ApolloHoax.net
Off Topic => General Discussion => Topic started by: Ranb on December 26, 2014, 06:39:56 PM
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I read The Martian and enjoyed it. http://www.amazon.com/Martian-Andy-Weir/dp/0553418025/ref=sr_1_1?ie=UTF8&qid=1419636340&sr=8-1&keywords=the+martian
I do have a question. The time on the surface was supposed to be one month. The book was written in 2012; were we still thinking in terms of a year to Mars, spend a month on the surface and then trek 12 months back to Earth? I'm thinking that a longer term on the surface so they can return 18 months later when Mars approaches Earth would be more believable.
Anyone here think the first manned mission to Mars will be one way?
Ranb
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Anyone here think the first manned mission to Mars will be one way?
Ranb
I tend to think the scenario laid out in the movie "Mission to Mars" (Gary Sinise) was pretty much right (even if the movie itself were crap... it had a weak, contrived premise and contained more cheese than a family sized pizza. In the movie, there were two missions each with a crew of four, launching three months apart near the beginning and end of the 2020 launch window (Jul to Sep). The intent was for the first crew to set up the habitation module (the Hab) with the intent of having everything ready to support a total of eight people on Mars for an extended period.
In 2007, Discovery Canada put out a three hour "docu-drama" mini-series called "Race to Mars" that gave a reasonably believable portrayal of what a Mars mission might look like. If you have three hours to spare....
Part One:
Part Two:
I think the idea that we might to go to Mars and only stay for a few days is not feasible or practical and frankly, I can't see them doing that. It worked for the moon because the travel time is just a few days. For Mars its 5 to 10 months, so longer term missions will need to be planned. They will likely set up a base of operations there and plan to stay until at least the next return window.
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I read an interview where Weir stated he used ion propulsion on the Hermes interplanetary craft to avoid some of the problems chemical propulsion systems would have as far as launch windows and transfer orbits etc. for human transport.
He also said in that interview that there is an easter egg in the novel. He doesn't explicitly give the year(s) that The Martian takes place during, but I guess it can be determined from the other info he does give, ie. launch windows, travel times, the light time communication lags etc.
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The novel was concerned with launch windows as there was no long term sleep for the crew and consumables were an issue. A movie based on the book will be released late 2015 with Matt Damon in the main role; he will be the protagonist this time instead of the antagonist of Interstellar.
I recall the unpressurized habitat (as shown by the tent flapping in the breeze) in Mission to Mars protecting a man without a suit as one of the reasons I walked out of the movie. Maybe they can do a better job with this one. :)
Thanks for the links cooky
Ranb
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I bought the book on Saturday at lunchtime. As I write this on Sunday night I'm about a third of the way through, and thoroughly enjoying it.
There are moments when I ask, "Seriously, would it be that simple/safe?" and other moments when I ask, "Seriously, would it be that hard/dangerous?" But then, I have none of the skill sets of the characters, so I'm willing to take it on trust that these various activities would pan out the way they do.
Incidentally, what's the angular size of Phobos as seen from the surface of Mars?
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I bought the book to read when I was in Hospital in October, but for one reason or another I didn't read it. I picked it up Friday night and finished it last night. Very good read I must say.
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Incidentally, what's the angular size of Phobos as seen from the surface of Mars?
.14 degrees at the horizon, .20 degrees at zenith, about a third of the size of our full moon. http://en.wikipedia.org/wiki/Phobos_%28moon%29#Orbital_characteristics
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Incidentally, what's the angular size of Phobos as seen from the surface of Mars?
.14 degrees at the horizon, .20 degrees at zenith, about a third of the size of our full moon. http://en.wikipedia.org/wiki/Phobos_%28moon%29#Orbital_characteristics
Cool, thank you.
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Okay, finished it last night.
Thoroughly enjoyable.
Although I have a few questions that would act as spoilers. Anybody mind if I post them here, or should I start another thread?
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Okay, no one's said anything, so here goes:
1. The atmosphere on the surface of Mars has 1% of the density of Earth's at sea level. Would any Martian dust storm have enough pressure to blow away an astronaut or tip over a spacecraft?
2. How likely would it have been for Watney's spacesuit to survive so many uses without failure?
3. How realistic is the idea of removing an engine from the Ares 4 MAV? What about the pipes supplying the fuel and oxidiser to the combustion chamber?
4. How realistic was the scenario of using Pathfinder to communicate with the rover?
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rtf
Okay, no one's said anything, so here goes:
1. The atmosphere on the surface of Mars has 1% of the density of Earth's at sea level. Would any Martian dust storm have enough pressure to blow away an astronaut or tip over a spacecraft?
2. How likely would it have been for Watney's spacesuit to survive so many uses without failure?
3. How realistic is the idea of removing an engine from the Ares 4 MAV? What about the pipes supplying the fuel and oxidiser to the combustion chamber?
4. How realistic was the scenario of using Pathfinder to communicate with the rover?
All good questions.
It's just my layman's opinion, but I suspect that Weir found a nice sweet spot between the realities of living on Mars against weaving a classic (yep, I think it is) sci-fi narrative.
Now, I'll get my layman's ass out of the way.
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Incidentally, another issue occurred to me, thanks to remembering reading somewhere something unusual about an Apollo mission.
I think it was on Apollo 16 that one of the crew picked up a rock which had been placed inside the LM, and nearly gave himself a cold burn. The rock had been collected before it had warmed up much, and then chilled while sitting in the shade inside the LM.
In the novel, at one point Watney uses 600 kilograms of rocks as ballast while testing out the rover. One of the aspects of the rover he wanted to test was his jury-rigged heating system. But one thing he never takes into account is the temperature of the rocks. I thought that 600 kg of rocks which had been sitting outside on the surface of a planet at a temperature 10s of degrees below zero (Celsius) would have a significant chilling effect on the air inside the rover, and that it'd take quite a bit of heat for them to warm up, but the issue is never raised, despite these sorts of issues being behind several of the challenges Watney faces.
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Incidentally, another issue occurred to me, thanks to remembering reading somewhere something unusual about an Apollo mission.
I think it was on Apollo 16 that one of the crew picked up a rock which had been placed inside the LM, and nearly gave himself a cold burn. The rock had been collected before it had warmed up much, and then chilled while sitting in the shade inside the LM.
Yes, it was John Young.
https://books.google.co.uk/books?id=eInnwg77gbkC&pg=PA167&lpg=PA167&dq=Apollo+16+rock+shadow+cold&source=bl&ots=e4LgyX7NkH&sig=YGpQfkewwiuPQFaoRHiXbWzJ06I&hl=en&sa=X&ei=YwL7VKbtDIL1Urefg_gB&ved=0CCEQ6AEwAA#v=onepage&q=Apollo%2016%20rock%20shadow%20cold&f=false
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For those who have read "The Martian", here is an interesting interview with author Andy Weir (warning, contains spoilers).
http://podcasts.scienceforthepeople.ca/episodes/Science_for_the_People_312_Impossible_Space.mp3
The interview is the first half of the 1hr podcast. As a bonus, the second half is the podcast is an interview with Professor Ethal Siegal about the so called "EM" drive.
Enjoy
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I don't know why - there's certainly no reference to it in the text - but when reading this book I always imagined that the Watney character was black. So as much as I like Matt Damon, I was a bit disappointed to find that they'd cast him instead of a black actor. Strange how your mind works sometimes.
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I already knew Matt Damon was cast in the role when I read the book, so I guess I didn't really have a chance to imagine the character any other way.
They released a full trailer today. I'm pretty excited for the movie.
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"..... I'm going to have to science the shit out of this!"
I love it!!!
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I'm looking forward to seeing this, but I feel like I only have to bother with the last 20 minutes thanks to the trailer!
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An interesting issue has come up about a technical aspect of this story regarding Watney's breathing oxygen. A post on another forum has suggested that it would be hazardous to use pure oxygen for the hab over a long period
"Doesn't a long stay on Mars require lots of nitrogen gas? A person can't stay on pure oxygen the whole time right? There was mention of oxygen toxicity and making oxygen from CO2, but nothing of how the lost nitrogen was made up for. "
The answer to that should be that you don't need nitrogen or anything else to "make up the difference". You just breathe pure oxygen at a partial pressure equivalent to the % of oxygen in the atmosphere; 21% so that's about 3.1 psi.
However, the issue of the Apollo 1 fire then came up...
"Apollo One showed one problem with pure O2"
I fired off a quick reply to the effect that the real cause of Apollo 1 was an electrical spark, combined with the massive amount of flammables used inside the capsule, especially velcro and nylon netting, combined with the fact that the O2 level inside was at 16.7 psi, 2 psi higher than atmospheric pressure.
But now, I'm not so sure. Would the Apollo 1 fire have still happened if they had been breathing air, or breathing pure O2 at a partial pressure of 0.21 atm.
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Aerobic organisms (like us) and fires both depend on oxygen, but respond differently.
Oxygen diffuses from the air through our lungs into the bloodstream in a "downhill" direction, i.e., from a high partial pressure in the air to a lower one in the blood. This won't work unless the oxygen has a minimum partial pressure. (One of the reasons you'd lose consciousness so quickly in a vacuum is that the oxygen already in your blood will diffuse back out through your lungs.) We also can't let that partial pressure get too high or the excess oxygen will become toxic, even fatal.
Adding inert gases to increase total air pressure has little or no effect (within reason) as long as they're not highly lipid soluble (which tends to make them anesthetic) or allowed to dissolve into body tissues and then rapidly released by a sudden drop in total pressure. That causes the bends.
Fires are different because nominally inert gases can carry away heat. This means pure oxygen is a greater fire hazard than air even when the partial pressures of oxygen are the same. Somewhere I saw a film of a Sealab mission in which the crew demonstrated the impossibility of striking a match in their high pressure helium/oxygen atmosphere. Even though there was plenty of oxygen for the crew, all that helium cooled the match head before it could ignite the match.
Some nominally inert gases also lose their inertness at high temperatures and interfere in the chemical reactions of a fire; this is how Halon worked.
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An interesting issue has come up about a technical aspect of this story regarding Watney's breathing oxygen. A post on another forum has suggested that it would be hazardous to use pure oxygen for the hab over a long period
"Doesn't a long stay on Mars require lots of nitrogen gas? A person can't stay on pure oxygen the whole time right? There was mention of oxygen toxicity and making oxygen from CO2, but nothing of how the lost nitrogen was made up for. "
The answer to that should be that you don't need nitrogen or anything else to "make up the difference". You just breathe pure oxygen at a partial pressure equivalent to the % of oxygen in the atmosphere; 21% so that's about 3.1 psi.
However, the issue of the Apollo 1 fire then came up...
"Apollo One showed one problem with pure O2"
I fired off a quick reply to the effect that the real cause of Apollo 1 was an electrical spark, combined with the massive amount of flammables used inside the capsule, especially velcro and nylon netting, combined with the fact that the O2 level inside was at 16.7 psi, 2 psi higher than atmospheric pressure.
But now, I'm not so sure. Would the Apollo 1 fire have still happened if they had been breathing air, or breathing pure O2 at a partial pressure of 0.21 atm.
From what I've read about the Apollo fire, a regular atmospheric mixture of gases would not have allowed the type pf conflagration that happened; I'm really not sure if that means a less intense fire or no fire at all.
I'm not sure about how much the fire hazard is reduced at partial pressure, but I am thinking the spacecraft might have imploded had you depressurized the CM to .21 atm at (virtually) sea level.
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Aerobic organisms (like us) and fires both depend on oxygen, but respond differently.
Oxygen diffuses from the air through our lungs into the bloodstream in a "downhill" direction, i.e., from a high partial pressure in the air to a lower one in the blood. This won't work unless the oxygen has a minimum partial pressure. (One of the reasons you'd lose consciousness so quickly in a vacuum is that the oxygen already in your blood will diffuse back out through your lungs.) We also can't let that partial pressure get too high or the excess oxygen will become toxic, even fatal.
Adding inert gases to increase total air pressure has little or no effect (within reason) as long as they're not highly lipid soluble (which tends to make them anesthetic) or allowed to dissolve into body tissues and then rapidly released by a sudden drop in total pressure. That causes the bends
So 0.21 atm of pure oxygen (3 psi) would be too low, but it would not be necessary to "fill up" with inert gas all the way to 1 atm would it? Is there some lower pressure that would be sufficient and safe?
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Adam Savage interview with Andy Weir.
Its 55min long and worth every minute of the time spent watching it..........
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I finally got and read the book, and it's every bit as good as everybody says.
I read most of it on a cross-country flight, and I didn't even mind that a jetbridge problem kept our flight at the arrival gate for a whole hour because it gave me enough time to finish it. Yes, it's that good.
The whole story is driven by a particularly perverse form of Murphy's Law: anything that can go wrong will go wrong -- but it won't actually kill you, and you'll still figure out a way. It's a little like the old Columbo TV series where there was never any mystery as to who the murderer was; the fun was in watching the battle of wits between Detective Columbo and the bad guy. And just as you know that Mark Watney must ultimately survive -- after all, this is fiction, and he is the hero -- the fun is in seeing how he survives.
Naturally, I'll soon have a long list of technical quibbles, but they're really quite minor given that nearly all of what passes for "science fiction" these days is really fantasy. This is hard science fiction of a quality I haven't seen in a very long time.
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From what I've read about the Apollo fire, a regular atmospheric mixture of gases would not have allowed the type pf conflagration that happened; I'm really not sure if that means a less intense fire or no fire at all.
I'm not sure about how much the fire hazard is reduced at partial pressure, but I am thinking the spacecraft might have imploded had you depressurized the CM to .21 atm at (virtually) sea level.
While the hazardous nature of pure oxygen is reduced by the partial pressure, it is certainly not eliminated. The fire in Apollo 1 was a ticking time bomb as all ground tests of American spacecraft had used pure oxygen at an elevated pressure versus ambient pressures. NASA was lucky for many years and grew complacent concerning fire. Even with the partial pressures of 3.5-5 psi. fire is a concern.
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Even with the partial pressures of 3.5-5 psi. fire is a concern.
Yes, there were a whole bunch of post-fire tests that came to the same basic conclusion.
A diluent gas like nitrogen conducts heat away from a fire, reducing the hazard even when the ppO2 is the same.
Since helium has a much higher thermal conductivity (0.142 W/m-K) than nitrogen (0.024), I wonder if using it as the diluent might allow a lower total pressure. This is always desirable in a spacecraft for weight reasons. If the speech problem is intolerable, consider neon. Its thermal conductivity (0.046) is much lower than helium, but it's still twice as high as air. Argon is cheap, but at 0.016 it's even worse than air (that's why it's used to fill double-pane windows).
Hydrogen has an even greater thermal conductivity than helium, but...
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Hydrogen has an even greater thermal conductivity than helium, but...
Hydrogen is even more flammable, a Zeppelin in outer space!
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Not if it's pure hydrogen. Get rid of all that nasty wasty oxygen! :P
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Not if it's pure hydrogen. Get rid of all that nasty wasty oxygen! :P
Seriously though, was there ever a small fire extinguisher in Apollo/Shuttle? Seems like a reasonable piece of equipment even though it has mass(maybe not as bad for the Shuttle.
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Not if it's pure hydrogen. Get rid of all that nasty wasty oxygen! :P
You may think you're joking, but hydrogen/oxygen mixtures (hydrox) and hydrogen/helium/oxygen (hydreliox) mixtures have been used in deep sea diving. As you descend, the O2 concentration has to be reduced to keep the ppO2 constant; too high, and you get oxygen toxicity.
Hydrogen has a famously wide flammability range, but it's not 0-100%; it actually tops out at around 96% in pure O2. So as long as you're deep enough to keep the O2 concentration well below 4%, you're safe.
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You may think you're joking, but hydrogen/oxygen mixtures (hydrox) and hydrogen/helium/oxygen (hydreliox) mixtures have been used in deep sea diving. As you descend, the O2 concentration has to be reduced to keep the ppO2 constant; too high, and you get oxygen toxicity.
Hydrogen has a famously wide flammability range, but it's not 0-100%; it actually tops out at around 96% in pure O2. So as long as you're deep enough to keep the O2 concentration well below 4%, you're safe.
Being a former scuba instructor and having no experience with either of those mixtures, it seems likely that sufficient recovery time would be necessary to allow all the H2 and He to evolve from tissues back to the lungs and then exhaled. I always wondered why so many people wanted to deep dive nothing much living from 60-90 foot depth. I guess being an instructor made me more conscious of the dangers involved.
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it seems likely that sufficient recovery time would be necessary to allow all the H2 and He to evolve from tissues back to the lungs and then exhaled.
Well sure, long decompression schedules are still required. When using hydrogen at depth, during the ascent you switch to helium well before the O2 percentage would rise to the explosive level, and the time spent decompressing would flush any residual hydrogen so there would never be an explosive mixture.
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Being a former scuba instructor and having no experience with either of those mixtures, it seems likely that sufficient recovery time would be necessary to allow all the H2 and He to evolve from tissues back to the lungs and then exhaled. I always wondered why so many people wanted to deep dive nothing much living from 60-90 foot depth. I guess being an instructor made me more conscious of the dangers involved.
As an instructor you will appreciate the following stories from my time as a BSAC instructor (stuff this PADI garbage :D)..
A guy turns up at our branch of the BSAC name of Dave, he says he is a "Level 3" qualified diver just moved to the area and would like to join our branch. OK bring your qualification record along for us to have a look at, no problems.
His diving record just looked wrong to me, no proper stamps and all signed by the same hand.. Still, without calling him a barefaced liar we inducted him into the branch. I was taking a class on high level entry techniques i.e entering the water in full gear from "say" a harbour wall. I demonstrated the correct technique from the 10M board at our pool. Dave tries it, enters the water, two fins emerge going in different directions, he comes up with his cylinder twisted 90degs on his back and his mask around his neck.. So we decide to test him, he doesn't even know the basics..
Anyway after 3 months winter pool training, we get him up to some sort of better standard and go on a real open water dive, but nobody wants to be his dive buddy! Roger, the clubs senior instructor decides to dive with him. As chance would have it, Roger gets into problems, when his demand valve (regulator) suddenly stopped functioning. Because of his lack of faith in Dave he didn't want to buddy breath with him. (This pre-dated the buddy mouthpieces that are commonplace now!). Roger decides to do a free ascent, as the clubs most experienced diver, this does not pose him a real serious problem. He gives Dave the throat sign, indicating he is having breathing problems and indicates that he is going up.
I had finished my dive and was sitting on the club boat, unaware of the dramas below. Dave in a panic has fully inflated his ABLJ (remember them ?). I was casually watching the water when Dave emerges like a Polaris missile, his fins came clean out of the water, how he never suffered a major embolism I will never know.. That was his first and last dive with the club.. :)
and now back to "The Martian!" :D Sorry for the hijack.
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As an instructor you will appreciate the following stories from my time as a BSAC instructor (stuff this PADI garbage :D)..
Different strokes for different folks!
A guy turns up at our branch of the BSAC name of Dave, he says he is a "Level 3" qualified diver just moved to the area and would like to join our branch. ...
I had finished my dive and was sitting on the club boat, unaware of the dramas below. Dave in a panic has fully inflated his ABLJ (remember them ?).
We had old fashioned buoyance compensators(70's)
I was casually watching the water when Dave emerges like a Polaris missile, his fins came clean out of the water, how he never suffered a major embolism I will never know.. That was his first and last dive with the club.. :)
and now back to "The Martian!" :D Sorry for the hijack.
That was one of the last tests we did in open water was an emergency ascent. The had to do it correctly to be certified. One of the instructors was "on top" of the diver incase (s)he panicked. I can remember "holding down" panicked divers, giving my buddy mouth pieces when necessary and slowly ascending, stern lecture, try again routine.
Ok back to Martians, again.
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I always wondered why so many people wanted to deep dive nothing much living from 60-90 foot depth. I guess being an instructor made me more conscious of the dangers involved.
[thread drift]
If you haven't already read this book, then I can thoroughly recommend it:
http://www.amazon.co.uk/Diving-Into-Darkness-Story-Survival/dp/0312383940
It's a terrible story of how quickly things can go fatally wrong in technical diving, but also a brilliant insight into the minds of the people that are compelled to push the envelope. As a total outsider to diving such as myself, it is also a fascinating peep into the technicalities involved.
[/thread drift]
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[thread drift]
If you haven't already read this book, then I can thoroughly recommend it:
http://www.amazon.co.uk/Diving-Into-Darkness-Story-Survival/dp/0312383940
It's a terrible story of how quickly things can go fatally wrong in technical diving, but also a brilliant insight into the minds of the people that are compelled to push the envelope. As a total outsider to diving such as myself, it is also a fascinating peep into the technicalities involved.
[/thread drift]
If you saw the bent arm of our lead instructor, you would understand the dangers associated with diving, and that was "only the bends". To have gasses expand in organs and tissues because of to rapid decompression was UGLY. We had an old Navy training video that was shown to students showing the complications. But having said that the scenery from 20' down was unbelievable well worth the time and effort to train and then dive them.
I guess the mind set to dive deep is rather akin to climbing mountains, driving/flying very fast has the same endorphins. :)
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If you saw the bent arm of our lead instructor, you would understand the dangers associated with diving, and that was "only the bends". To have gasses expand in organs and tissues because of to rapid decompression was UGLY. We had an old Navy training video that was shown to students showing the complications. But having said that the scenery from 20' down was unbelievable well worth the time and effort to train and then dive them.
Oh, I understand them alright. A chap that I knew a few years back got badly bent after a dive at Scapa Flow. He did two heavy dives in a day and pushed his luck on his last deco. He got the bend in his spine and lost the use of his legs. Luckily he was diving in an area that has some of the best treatment centres that you will find anywhere (due to the North Sea rigs) and was airlifted to a deco tank in Aberdeen. It took him a week to regain use of his legs....a fair bit longer before he didn't need adult nappies. Not a nice experience for him at all and it affected his mental outlook quite badly. He used to live for diving and it was a massive loss for him being told never to dive again.
I guess the mind set to dive deep is rather akin to climbing mountains, driving/flying very fast has the same endorphins. :)
I'd agree with that. it must be the thrill of going where very few have gone before. There's only a handful of people alive that have gone deeper than 250 metres. Something like 10% of people that have dived to that depth have had no injuries and 50% of them have died. They are pretty damning statistics.
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I guess the mind set to dive deep is rather akin to climbing mountains, driving/flying very fast has the same endorphins. :)
Or maybe it's all that N2 dissolved in body lipids...
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I guess the mind set to dive deep is rather akin to climbing mountains, driving/flying very fast has the same endorphins. :)
Or maybe it's all that N2 dissolved in body lipids...
Well something must drive them. I personally don't have all those thrill seeking juices. A fast ride down a zip line is about as far as I go.
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I remember some of my friends coming back from a dive, all exuberantly proclaiming "It was wonderful! We didn't die!"
For some reason, that sort of endorsement never made me want to take up the sport.
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I remember some of my friends coming back from a dive, all exuberantly proclaiming "It was wonderful! We didn't die!"
For some reason, that sort of endorsement never made me want to take up the sport.
Well I will testify it is wonderful and not because no one died. In fact on all the dives I have been on, there were no injuries as everyone took the training to heart. I'm not saying it wasn't a dangerous environment, but with caution the sites, animal and plant life is hard to describe, wonderful does an adequate job though. For young people (to me that is) I would highly recommend taking the training and then dive.
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I remember some of my friends coming back from a dive, all exuberantly proclaiming "It was wonderful! We didn't die!"
For some reason, that sort of endorsement never made me want to take up the sport.
"If at first you don't succeed, skydiving is not for you."
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"If at first you don't succeed, skydiving is not for you."
"Its not the fall for 10,000' that kills you...its the stopping in the last inch."
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"If at first you don't succeed, skydiving is not for you."
"Its not the fall for 10,000' that kills you...its the stopping in the last inch."
That will leave a mark that won't be easily healed.
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I remember some of my friends coming back from a dive, all exuberantly proclaiming "It was wonderful! We didn't die!"
For some reason, that sort of endorsement never made me want to take up the sport.
"If at first you don't succeed, skydiving is not for you."
"Lithobraking is a stone, cold killer manoeuvre"
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"Lithobraking is a stone, cold killer manoeuvre"
Especially if you calculate the start of the break using feet instead of meters.
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"If at first you don't succeed, skydiving is not for you."
"Its not the fall for 10,000' that kills you...its the stopping in the last inch."
If you find yourself in such a situation, do the following:
- Straighten your back and limbs.
- Cross your legs with your left leg over your right.
- Place your left hand on your right hip.
- Place your right hand on your left buttock.
This won't do YOU any good, but it will make it easier for the clean-up crew to unscrew you from the ground.
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Anyone interested in NASA's future plans for Mars or "The Martian", this is a must see. Its a panel discussion at this year's Comic Con in San Diego. The panellists are....
Aditya Sood - Producer of "The Martian"
Jim Green - NASA Planetary Science Director
Todd May - NASA SLS program Manager
Victor Glover - NASA Astronaut
Andy Weir - Author of "The Martian"
Very interesting and well worth the time to watch. The hour just flew by...
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Saw the movie today. It was fantastic! Some parts of the book were cut, but I don't feel like it hurt the story.
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Saw the movie today. It was fantastic! Some parts of the book were cut, but I don't feel like it hurt the story.
Notes to put that in the itinerary.
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You may think you're joking, but hydrogen/oxygen mixtures (hydrox) and hydrogen/helium/oxygen (hydreliox) mixtures have been used in deep sea diving. As you descend, the O2 concentration has to be reduced to keep the ppO2 constant; too high, and you get oxygen toxicity.
Hydrogen has a famously wide flammability range, but it's not 0-100%; it actually tops out at around 96% in pure O2. So as long as you're deep enough to keep the O2 concentration well below 4%, you're safe.
Being a former scuba instructor and having no experience with either of those mixtures, it seems likely that sufficient recovery time would be necessary to allow all the H2 and He to evolve from tissues back to the lungs and then exhaled. I always wondered why so many people wanted to deep dive nothing much living from 60-90 foot depth. I guess being an instructor made me more conscious of the dangers involved.
Depends whether or not the life is photosynthetic or not. Lots of sponge and soft coral reefs below 27 m.
Lots of other things to see as well - deep wrecks, caves etc.
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Just got back myself from the film. Capsule review:
Faithful to the book? Close enough.
Scientifically accurate? Yes, close enough.
Matt Damon appropriately cast? Yes.
Other cast good? Yes.
Exciting? Yes, even if you've read the book and know what happens.
Spoiler: Sean Bean's character does not die.
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Depends whether or not the life is photosynthetic or not. Lots of sponge and soft coral reefs below 27 m.
Lots of other things to see as well - deep wrecks, caves etc.
I didn't say there was no life I said nothing much, the preponderance of life is much greater in the 60-90' range, than deeper. Yes there is life that does not depend on photosynthesis and does exist a very deep depths.
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Just got back myself from the film. Capsule review:
Faithful to the book? Close enough.
Scientifically accurate? Yes, close enough.
Matt Damon appropriately cast? Yes.
Other cast good? Yes.
Exciting? Yes, even if you've read the book and know what happens.
Spoiler: Sean Bean's character does not die.
Boromir was OK after all? Yay!
A good chunk of our local NASA/contractor workforce is going to a special screening tomorrow. I'll be heading in early to take care of business beforehand. Should be fun.
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Spoiler: Sean Bean's character does not die.
Dammit! >:(
Does he not even get to go to t'foot of yon mountain?
One day someone will trap him in a wet paper bag and challenge him to act his way out of it.
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I saw it in 3D the other night, which did absolutely nothing to dissuade me from thinking that 3D has got to be one of the best ways of distracting from a movie.
Overall, it was a bit "meh". I think that the film lots most of the dark humour and genuine laugh-out-loud aspects of the book. The big attraction of the book was how he solved the various problems using science, most of which is lost in the movie. It was a very difficult proposition to transfer to the big screen with the amount of internal monologue.
It was a decent popcorn type of affair. It certainly won't be a movie that will get added to the Blu Ray collection and I doubt if I would be prepared to give it a second watching.
On a side note, I think that now, after Interstellar, The Martian and Saving Private Ryan, Hollywood has spent more than enough money rescuing Matt Damon. The next time that he gets himself in trouble I vote for letting him sort himself out. ;D
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Depends whether or not the life is photosynthetic or not. Lots of sponge and soft coral reefs below 27 m.
Lots of other things to see as well - deep wrecks, caves etc.
I didn't say there was no life I said nothing much, the preponderance of life is much greater in the 60-90' range, than deeper. Yes there is life that does not depend on photosynthesis and does exist a very deep depths.
The sponge, soft coral (and bryozoan) density can be very high as well. So lots to see as opposed to "nothing much" IMHO.
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I thought it was a great movie. Certainly ones one the best more or less realistic space SF movies of the past decade or more. Also one of the very few good Mars movies (a very under populated field). Probably the only one that attempts to convey Martian grandeur
Lots to think about and discuss with people on many levels, from life support, human factors, orbital mechanics, habitat, rover and suit design to mission architecture.
4.5/5
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Spoiler: Sean Bean's character does not die.
Well, now I've GOT to see it!
He seems to be consciously bucking the trend - he didn't die in Jupiter Rising either, I heard. Maybe it's a new contract demand - "My character shall remain on the right side of the earth when the credits roll."
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Spoiler: Sean Bean's character does not die.
Well, now I've GOT to see it!
He seems to be consciously bucking the trend - he didn't die in Jupiter Rising either, I heard. Maybe it's a new contract demand - "My character shall remain on the right side of the earth when the credits roll."
...and will be from Yorkshire.
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Spoiler: Sean Bean's character does not die.
Well, now I've GOT to see it!
He seems to be consciously bucking the trend - he didn't die in Jupiter Rising either, I heard. Maybe it's a new contract demand - "My character shall remain on the right side of the earth when the credits roll."
He doesn't die in Sharpe either, one of my favourite TV series, where he is lead.
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...and will be from Yorkshire.
Robert Mugabe is from Yorkshire, the clue is in his name, just say his surname backwards.. Very English humour may not travel well.. :D
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Spoiler: Sean Bean's character does not die.
Well, now I've GOT to see it!
He seems to be consciously bucking the trend - he didn't die in Jupiter Rising either, I heard. Maybe it's a new contract demand - "My character shall remain on the right side of the earth when the credits roll."
He doesn't die in Sharpe either, one of my favourite TV series, where he is lead.
Sharpe rocks.
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Finally saw the movie last night. Terrific. It was surprisingly faithful to the book, and the parts that were missing weren't really essential to the story. It's easily the best hard science fiction on the screen in a very long time. But of course it has its nits, and like any other geek I feel compelled to discuss them.
So what's the deal? Can we give spoilers here?
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Finally saw the movie last night. Terrific. It was surprisingly faithful to the book, and the parts that were missing weren't really essential to the story. It's easily the best hard science fiction on the screen in a very long time. But of course it has its nits, and like any other geek I feel compelled to discuss them.
So what's the deal? Can we give spoilers here?
I've read the book, haven't seen the movie, but intend to do so.
As far as I'm concerned, discuss away.
Though perhaps it might be polite to mention at the start of the post that you're posting spoilers. If you're really concerned, just change the text colour to the same as the background.
But seriously, go for your life. I don't mind.
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Finally saw the movie last night. Terrific. It was surprisingly faithful to the book, and the parts that were missing weren't really essential to the story. It's easily the best hard science fiction on the screen in a very long time. But of course it has its nits, and like any other geek I feel compelled to discuss them.
So what's the deal? Can we give spoilers here?
As for me, discuss ahead. It will not make any difference I have seen Star Wars (iv) about 3-4 times in theater and perhaps a dozen more times on the small screen. Nothing detracts from a good movie, whether you know what happens or not.
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Seen the movie twice, read the book twice, it's very good. I think prefer the movie to the book (which is unusual for me), probably because the technology is better thought through in some respects and with a better ending.
But without a doubt the best hard SF movie for a very long time, and the best Mars movie ever. Full of teachable moments and surprisingly funny.
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I haven't read the book but enjoyed the movie. Sure, there are the 'suspension of disbelief' moments but the overall story, acting, etc, made that suspension very easy to do.
I would recommend it to anyone.
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Here's quite a good review of the movie which appeared in New Zealand newspapers. Includes a three-minute video. Four-and-a-half stars out of five.
http://www.stuff.co.nz/entertainment/film/film-reviews/72749116/review-the-martian
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Okay, my list of nits is a little longer than I had thought...still working on it.
But it's still a great movie.
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Just back from seeing it.
I agree with Dalhousie; for mine, this was by far the best hard sci-fi movie since Blade Runner, and yes, Matt Damon was absolutely the right space pirate actor for the part.
If someone had told me beforehand, the type of music they would use in this movie, I would have said WTF? However, it workeds really well
WARNING: BEYOND THIS POINT THERE BE SPOILERS
Just a couple of nitpicks and questions
1. the obvious one was the storm that injured Watney at the beginning. As has been stated, it could not have caused the damage it did due to the low pressure of Mars' atmosphere.
2. When the HAB airlock malfunctioned and blew off, Watney's helment visor was punctured, and he lost pressure, it seemed to take about 30 secoinds to get down to 5% pressure, but once he taped over the cracks and the small hole, it was almost instantly restored to nominal. Really? That quickly, and what anout the bends?
3. Would taping some plastic sheeting over the gapiing hole left by the malfuntion of the HAB airlock have been enough to keep the HAB pressurised?
4. Could they really have accurately calculated the deceleration effect of blowing the front airlock off the Hermes
5. Would puncturing his glove really have worked the way it was depicted? How was he able to stop it leaking, once Lewis caught him, long enough to get him into Hermes?
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WARNING: BEYOND THIS POINT THERE BE SPOILERS
2. and what about the bends?
It is my understanding (and I'm not an expert) that the bends SCUBA divers may suffer from are an effect resulting from pressure decrease from far above 1 atm down to 1 atm.
In a space suit, the pressure decrease would be from, say, 0.6 atm down to near 0. Maybe that's not causing nitrogen bubbles in blood at all?
I remember seeing a video of a suited person, where the suit failed, the person fell unconscious and was rescued. After a while (measured in minutes) he was literally up and running again.
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WARNING: BEYOND THIS POINT THERE BE SPOILERS
2. and what about the bends?
It is my understanding (and I'm not an expert) that the bends SCUBA divers may suffer from are an effect resulting from pressure decrease from far above 1 atm down to 1 atm.
In a space suit, the pressure decrease would be from, say, 0.6 atm down to near 0. Maybe that's not causing nitrogen bubbles in blood at all?
I remember seeing a video of a suited person, where the suit failed, the person fell unconscious and was rescued. After a while (measured in minutes) he was literally up and running again.
OK. I just thought that the bends was caused by a sudden decrease in pressure, and that a slow decrease in pressure, i.e. by stage decompression from a deep dive, would avoid it. IOW, I thought it was due to a relative pressure decrease, not a specific pressure decrease.
Does Weir actually mention the pressure/partial pressure the Ares crew would be breathing in their suits on the surface and in the HAB? I haven't read the book, and if it was mentioned in the movie, or there was a graphic showing it, I missed it.
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Does Weir actually mention the pressure/partial pressure the Ares crew would be breathing in their suits on the surface and in the HAB? I haven't read the book, and if it was mentioned in the movie, or there was a graphic showing it, I missed it.
The book actually plays looser with partial pressures than with most of the chemistry presented. It talks about relative percentages but doesn't really go into ppO2 being the critical value at all. In the book the astronauts are breathing mixed N2/O2 at ~100 kPa in the fabric-constructed hab as well as on EVAs; I have no idea if that would be considered on an actual mission but it seems unlikely.
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The book actually plays looser with partial pressures than with most of the chemistry presented. It talks about relative percentages but doesn't really go into ppO2 being the critical value at all. In the book the astronauts are breathing mixed N2/O2 at ~100 kPa in the fabric-constructed hab as well as on EVAs; I have no idea if that would be considered on an actual mission but it seems unlikely.
* * * * * SPOILER * * * * *
OK, so I think my question #3 earlier
3. Would taping some plastic sheeting over the gapiing hole left by the malfuntion of the HAB airlock have been enough to keep the HAB pressurised?
Definitely had some validity.
The hole was at least 8ft in diamater, its area given by πr2
R = 48" , so
a = 7238 in2 at 14.83 lb in2
Thats a force of 107,342 lb (nearly 48 tons) pushing out on that plastic sheeting.
Surely, it would puff out tight like a baloon and not flap around in the breeze like to did. I was anly held in place with a few strips of duct tape so I would not be trusting that enough to wander around inside the HAB without a spacesuit on.
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Does Weir actually mention the pressure/partial pressure the Ares crew would be breathing in their suits on the surface and in the HAB? I haven't read the book, and if it was mentioned in the movie, or there was a graphic showing it, I missed it.
The book actually plays looser with partial pressures than with most of the chemistry presented. It talks about relative percentages but doesn't really go into ppO2 being the critical value at all. In the book the astronauts are breathing mixed N2/O2 at ~100 kPa in the fabric-constructed hab as well as on EVAs; I have no idea if that would be considered on an actual mission but it seems unlikely.
I think you are right.
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The book actually plays looser with partial pressures than with most of the chemistry presented. It talks about relative percentages but doesn't really go into ppO2 being the critical value at all. In the book the astronauts are breathing mixed N2/O2 at ~100 kPa in the fabric-constructed hab as well as on EVAs; I have no idea if that would be considered on an actual mission but it seems unlikely.
* * * * * SPOILER * * * * *
OK, so I think my question #3 earlier
3. Would taping some plastic sheeting over the gapiing hole left by the malfuntion of the HAB airlock have been enough to keep the HAB pressurised?
Definitely had some validity.
The hole was at least 8ft in diamater, its area given by πr2
R = 48" , so
a = 7238 in2 at 14.83 lb in2
Thats a force of 107,342 lb (nearly 48 tons) pushing out on that plastic sheeting.
Surely, it would puff out tight like a baloon and not flap around in the breeze like to did. I was anly held in place with a few strips of duct tape so I would not be trusting that enough to wander around inside the HAB without a spacesuit on.
I got similar numbers. I don't think it would work. In the book he uses "hab canvas" and much more robust sealants.
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There is the very common failure in heltent design (about as common as sound in space) - lights in the helmet. This was first shown in Outland I think. It would never work, because it would blind the wearer's night vision. The reason for it in films is obvious of course, it is to show the astronaut's face
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On another board someone asked why people were so obsessively picking technical nits with this movie, when technobabble and worse in star wars or star trek gets off almost scott free. One reply was intriguing, there is an equivalent of "uncanny valley" in depiction of humans, as one gets very close to reality people notice the technological issues more and are more upset by them.
There might be something in this. It got to the point with Gravity that people think it was a very bad movie, when it's not. I would be very sorry if that happened here. Not only is it a more positive movie that Gravity, I think, like it, the film as a good chance of a Hugo and an Oscar.
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If someone had told me beforehand, the type of music they would use in this movie, I would have said WTF? However, it workeds really well.
As running gags in space movies go, that wasn't a bad one.
But if I had been selecting the rest of the music, I would definitely have used Ralph Vaughan-Williams' Sinfonia Antartica. He originally wrote it as the score for the 1947 movie Scott of the Antarctic and later turned it into a complete symphony (his 7th). I think it is one of the most vivid tone poems ever written, and it's just as good at conjuring up images of Mars as of the Antarctic. It would have been ideal for those outstanding wide CGI shots of Watney's long treks.
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On another board someone asked why people were so obsessively picking technical nits with this movie, when technobabble and worse in star wars or star trek gets off almost scott free. One reply was intriguing, there is an equivalent of "uncanny valley" in depiction of humans, as one gets very close to reality people notice the technological issues more and are more upset by them.
I've been saying exactly that for some time -- sure it wasn't me?
Don't get me wrong, it's because The Martian is such an excellent movie overall that we enjoy picking nits in it, just as generations of fans have been picking nits in Star Trek. If I thought it was a bad movie I wouldn't be talking about it.
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WARNING: BEYOND THIS POINT THERE BE SPOILERS
Just a couple of nitpicks and questions
1. the obvious one was the storm that injured Watney at the beginning. As has been stated, it could not have caused the damage it did due to the low pressure of Mars' atmosphere.
Right. He might have picked some other plot device that required the crew to make a fast getaway and leave Watney behind for dead. Maybe an unstoppable leak in the fuel system that forced them to launch immediately or be stranded.
2. When the HAB airlock malfunctioned and blew off, Watney's helment visor was punctured, and he lost pressure, it seemed to take about 30 secoinds to get down to 5% pressure, but once he taped over the cracks and the small hole, it was almost instantly restored to nominal. Really? That quickly, and what anout the bends?
That wasn't too unrealistic. A PLSS automatically adds O2 through a pressure regulator to replace metabolic consumption, and it will also keep a suit pressurized against leaks if the max regulator flow rate is high enough -- until your high pressure oxygen supply runs out. It might well maintain survival pressure against the leaks depicted for some time, especially if the PLSS was augmented with an Apollo-style OPS. (The flow of a pressurized gas through a small hole is generally Mach 1.) But I don't remember if the warning was for low suit pressure or a low oxygen supply. The former would cause him to pass out quickly; the latter would require him to get to shelter quickly before he exhausted what was left of his oxygen supply.
3. Would taping some plastic sheeting over the gapiing hole left by the malfuntion of the HAB airlock have been enough to keep the HAB pressurised?
Absolutely not, as others have already shown. It sure looked like HDPE to me, nothing magical. And the Martian wind even depresses it inward at one point. No way.
4. Could they really have accurately calculated the deceleration effect of blowing the front airlock off the Hermes
Maybe. The whole bit with blowing off the airlock door was over the top. The reason for doing it, as I recall, was that an interlock prevented both doors from being opened at the same time. It would have been far more realistic (if not as dramatic) for one of the crew to just hotwire the damn thing. But the story has you on the edge of your seat by that point so you can sort of excuse it.
5. Would puncturing his glove really have worked the way it was depicted? How was he able to stop it leaking, once Lewis caught him, long enough to get him into Hermes?
Seems unlikely. He does kinda forget about the leak later, doesn't he?
I noticed another "physics failure" in that sequence (one of several). At one point Lewis and Watney are wrapping themselves in Lewis's tether, which draws them toward the airlock and each other. That should have had them spinning like a neutron star due to angular momentum conservation. Maybe Lewis' maneuvering unit was better than I thought.
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A few more nits not already mentioned (SPOILERS):
Scavenging Hydrazine
Watney apparently drains surplus descent stage hydrazine through the engine nozzles. Strange, anybody who knew liquid rockets would use the fill-and-drain valves provided for exactly that purpose.
Straight hydrazine (N2H4) freezes at +1C. No way it would still be liquid on Mars. Although a large rocket would more likely use UDMH, MMH or Aerozine-50 (50-50 UDMH + N2H4) with lower freezing points (but which would still probably freeze on Mars) he uses a catalyst to decompose it. That only works with straight hydrazine.
Not sure why he couldn't just burn the fuel directly. Also, it's incredibly toxic and I very seriously doubt he could burn it completely enough to avoid all sorts of noxious byproducts (NH3, etc).
The RTG Space Heater
Use of a Pu-238 RTG as space heater is entirely plausible and wouldn't be dangerous at all unless you deliberately cut it open (as he does concede). Many pictures exist of workers (some in ordinary clothes) around fueled RTGs at launch sites. I had that idea way back during Apollo 13 when I heard how cold they were. But it would have required a hazardous EVA for which they had not trained, and it wasn't truly necessary anyway.
There's no plausible reason you'd ever want to throw away something as valuable as several kg of Pu-238 on Mars, especially when you have a habitat that needs a lot of heating.
Burying a fueled RTG in deep sand would almost certainly insulate it so well that the fins would melt, if not the whole thing.
Martian Dust
Not sure a spacecraft would be totally buried by dust after only 2 decades or so. (The setting isn't specified, but the JPL Pathfinder guys didn't look that old.) I think the orbiting cameras have spotted the two Vikings that have been there 40 years now.
JPL and JSC
I've been to both places several times; they look nothing like their gleaming, modern depictions in the movie. Think 1960's University Institutional.
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While picking nits I should be fair and cite elements of the story that I think worked really well.
The real standout is that great, nail-biting rescue sequence. You must match position and velocity in a rendezvous, and because you don't have the fuel to decelerate into Mars orbit and escape again, it has to be a flyby. And that means you get only one shot at the rescue, which creates an enormous amount of suspense. It was a perfect example of working with physical laws to drive your story instead of just dismissing them with lame handwaving.
After Gravity I was so delighted to see some realistic trajectory physics that I was willing to overlook the more unrealistic, over-the-top elements like using an IED to blow off an airlock door and puncturing Watney's suit to act as a maneuvering jet. That kind of seat-of-the-pants space physics is very unlikely to work in real life. But it was still great fun. That's the section I was reading when my plane got stuck at the arrival gate for an hour, and I was so engrossed I didn't mind.
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Does Weir actually mention the pressure/partial pressure the Ares crew would be breathing in their suits on the surface and in the HAB? I haven't read the book, and if it was mentioned in the movie, or there was a graphic showing it, I missed it.
Yes in both places. In the movie it frequently shows up as on-screen telemetry in his video recordings. We were seated toward the left side of the theater and they were almost in front of us on the left side of the screen. It was ordinary air slightly below sea level pressure.
I was surprised that he didn't seem to research this one very well. He was supposedly talking to lots of NASA guys and other space geeks, so one of them should have explained that even after 5 decades of work, nobody has yet produced a really comfortable suit that operates at ~0.22 bar, much less a full 1 bar. And because the crews were doing frequent EVAs, that would call for the habitat also being pure or nearly pure O2 at reduced pressure to avoid decompression sickness ("the bends"). That would also greatly reduce the stress on the structure (which we find is an actual problem).
There is at least one confirmed case of decompression sickness during flight in the US program: Michael Collins during Gemini X. He didn't report this at the time for fear of never flying again, but he did write about it in his book Carrying the Fire. He was more careful to follow the prebreathing protocols before his Apollo 11 flight and didn't have a problem.
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There is the very common failure in heltent design (about as common as sound in space) - lights in the helmet. This was first shown in Outland I think. It would never work, because it would blind the wearer's night vision. The reason for it in films is obvious of course, it is to show the astronaut's face
This always reminds me of Mad's long-ago spoof of the original Battlestar Galactica, specifically a scene where Baltar is glowering from his throne and the oily Cylon henchman asks him, "Is there anything else I can do for you, Imperious One?"*
"Yes! You can turn off these lights that are always shining up into my face to make me look evil! They're driving me crazy!"
* dialog recall not guaranteed; Mad's exact wording was of course much funnier.
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How come a storm was strong enough to tilt the MAV over to critical levels, thus enforcing a rapid take-off, yet NASA was happy to send a similar design to sit in Schiaperalli or a number of years?
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How come a storm was strong enough to tilt the MAV over to critical levels, thus enforcing a rapid take-off, yet NASA was happy to send a similar design to sit in Schiaperalli or a number of years?
Just...Because....
You could also ask why NASA never heard of guy wires.
I suppose NASA would think it a very unlikely occurrence, especially since it's impossible in reality, but this being fiction the author has the right to cause all sorts of unlikely things to happen.
Kinda like the opening scene in Rosencranz And Gildenstern Are Dead, when they're flipping a coin and it comes up heads 92 times in a row. They realize the extreme unlikeliness of this according to the laws of probability, and begin to speculate that they're not real or that somebody is controlling everything that happens.
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On another board someone asked why people were so obsessively picking technical nits with this movie, when technobabble and worse in star wars or star trek gets off almost scott free. One reply was intriguing, there is an equivalent of "uncanny valley" in depiction of humans, as one gets very close to reality people notice the technological issues more and are more upset by them.
I've been saying exactly that for some time -- sure it wasn't me?
Don't get me wrong, it's because The Martian is such an excellent movie overall that we enjoy picking nits in it, just as generations of fans have been picking nits in Star Trek. If I thought it was a bad movie I wouldn't be talking about it.
Not unless your haunt the nasa spaceflight forum under a different name.....
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Does Weir actually mention the pressure/partial pressure the Ares crew would be breathing in their suits on the surface and in the HAB? I haven't read the book, and if it was mentioned in the movie, or there was a graphic showing it, I missed it.
Yes in both places. In the movie it frequently shows up as on-screen telemetry in his video recordings. We were seated toward the left side of the theater and they were almost in front of us on the left side of the screen. It was ordinary air slightly below sea level pressure.
I was surprised that he didn't seem to research this one very well. He was supposedly talking to lots of NASA guys and other space geeks, so one of them should have explained that even after 5 decades of work, nobody has yet produced a really comfortable suit that operates at ~0.22 bar, much less a full 1 bar. And because the crews were doing frequent EVAs, that would call for the habitat also being pure or nearly pure O2 at reduced pressure to avoid decompression sickness ("the bends"). That would also greatly reduce the stress on the structure (which we find is an actual problem).
Nothing supposed about it, he did. However partial pressures is not high on what most people want to talk about or volunteer advice on.
There is at least one confirmed case of decompression sickness during flight in the US program: Michael Collins during Gemini X. He didn't report this at the time for fear of never flying again, but he did write about it in his book Carrying the Fire. He was more careful to follow the prebreathing protocols before his Apollo 11 flight and didn't have a problem.
I think that has been questioned.
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How come a storm was strong enough to tilt the MAV over to critical levels, thus enforcing a rapid take-off, yet NASA was happy to send a similar design to sit in Schiaperalli or a number of years?
Just...Because....
You could also ask why NASA never heard of guy wires.
I suppose NASA would think it a very unlikely occurrence, especially since it's impossible in reality, but this being fiction the author has the right to cause all sorts of unlikely things to happen.
Guy ropes are not going to be easy to do with a MAV that's landed unmanned and it is clear from the story that this is a very improbable and local event.
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Not unless your haunt the nasa spaceflight forum under a different name.....
Or maybe somebody else picked it up from me and repeated it.
Or maybe great minds just think alike...
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Nothing supposed about it, he did. However partial pressures is not high on what most people want to talk about or volunteer advice on.
Actually I think it would be high on the list of the kinds of things technically knowledgeable people would mention.
I think that has been questioned.
We discussed this before a couple of years ago. In the sense that he was never examined and diagnosed by a doctor at the time, yes. But his description of his symptoms (nagging but temporary knee pain) are certainly consistent with decompression sickness:
(About 8 hours into the flight, trying to go to sleep):
"Speaking of hurting, my left knee hurts, a throbbing ache that began a couple of hours ago, gradually worsened, and is now holding steady at a moderate but very uncomfortable level of pain. I think it is nitrogen coming out of solution in the tissues... The reason I make this diagnosis is that the pain is exactly like ones I have felt before in altitude chambers. ...what to do now(?). Discuss it or try to ignore it? I have a vivid picture of the avalanche of medical conferences one quick complaint will produce... everything short of a house call. ... What can they tell me to do, besides take a couple of aspirin?"
Eight hours, four aspirin, and a couple of hours of spotty sleep later:
"... when I awake I note with relief that my knee pain has nearly disappeared."
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Guy ropes are not going to be easy to do with a MAV that's landed unmanned and it is clear from the story that this is a very improbable and local event.
Where there's a will, there's a way. Gas-driven harpoons shot into the surface at an angle just after landing. Worked great on Philae, right?
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Don't get me wrong, it's because The Martian is such an excellent movie overall that we enjoy picking nits in it, just as generations of fans have been picking nits in Star Trek. If I thought it was a bad movie I wouldn't be talking about it.
Personally, I enjoy this sort of nitpicking because I generally learn something, which is less likely for a softer sci-fi.
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Guy ropes are not going to be easy to do with a MAV that's landed unmanned and it is clear from the story that this is a very improbable and local event.
Where there's a will, there's a way. Gas-driven harpoons shot into the surface at an angle just after landing. Worked great on Philae, right?
Or, an anemometer and a tilt sensor. If the wind gets up and the MAV starts to tilt, the nose RCS fires as required to keep the tilt from going beyond limits. That what the crew did in their MAV
But hey, thats "in story".....in reality, we know that even the strongest known Martian winds wouldn't budge the MAV due to the low atmospheric pressure.
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How come a storm was strong enough to tilt the MAV over to critical levels, thus enforcing a rapid take-off, yet NASA was happy to send a similar design to sit in Schiaperalli or a number of years?
The storm that hit the Ares III site was unprecedentedly strong and the Ares IV MAV was landed before the Ares III mission landed, in fact in the book its mentioned that it was remotely flown down by the Ares III pilot prior to their landing, so NASA was kinda stuck with it being there for the ~4 years prior to the Ares IV mission getting there (well if Cap'n Blondbeard hadn't absconded with it anyway). Presumably the next MAV that was sent to Mars would be a modified design that would be better able to handle a superstorm like hit Ares III.
The modified Mars Direct plan used by the Ares missions means that the MAV has to arrive years ahead of the actual mission because it takes that long to generate the fuel it will use for take off from a relatively small onboard hydrogen supply and some clever chemistry with the Martian atmosphere.
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Was the Hermes in an Aldrin Cycler orbit? I don't remember that term being used in either the book or the movie, but it certainly resembled it. It was said to be reused by each successive Ares crew.
Aldrin's original idea was to put a spacecraft into a gravity assist trajectory that would move back and forth between Earth and Mars indefinitely with very little propellant. The crews would join up with it as it flew past their departure planet and jump off as it passed their destination planet.
I think the original idea was to have two separate spacecraft in two separate Cycler orbits, one going from Earth to Mars in 6 months and the other returning from Mars to Earth in 6 months, with each taking another ~18 months to get back into position.
Edited to add: Never mind. I see the Hermes remained in Mars orbit, which made it immediately available when the Ares III crew had to leave early. (I don't recall, though, how they were able to leave Mars orbit for earth before the originally scheduled return window.) I know that in the story it makes an unauthorized hyperbolic flyby of Earth, but what was the original plan? Go into Earth orbit and leave again for Mars with the next crew, or make a quick swap during a flyby?
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Edited to add: Never mind. I see the Hermes remained in Mars orbit, which made it immediately available when the Ares III crew had to leave early. (I don't recall, though, how they were able to leave Mars orbit for earth before the originally scheduled return window.) I know that in the story it makes an unauthorized hyperbolic flyby of Earth, but what was the original plan? Go into Earth orbit and leave again for Mars with the next crew, or make a quick swap during a flyby?
The original plan would be for the Hermes to enter Earth orbit where it would be resupplied and refitted while the Ares IV pre-supply missions were being sent to Mars and the MAV was cooking the martian atmosphere and its supply of hydrogen to make methane and oxygen to fuel its ascent (and possibly be used for stuff on the surface too). Once all their supplies and the MAV were ready on Mars then the next Ares crew would depart on Hermes
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Gotcha, so it wasn't intended to be an Aldrin cycler. Entering and leaving orbit on each end would take a lot of propellant, but it makes the timing easier. With an Aldrin cycler you would be doing a Watney/Hermes-style rendezvous by intent on each end, and even with careful planning it would probably be pretty exciting because you'd only get one chance.
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Gotcha, so it wasn't intended to be an Aldrin cycler. Entering and leaving orbit on each end would take a lot of propellant...
I think it was described in the book as a continuously thrusting ion-powered spacecraft, with a nuclear reactor as its power source. I would imagine that circularizing (and later exiting) earth and mars orbits would take a LONG time in reality for that mission profile, though.
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Oh, as a self-respecting EE I should say that I object to the one line in the movie that is rapidly becoming its catchphrase:
I'm gonna have to science the shit outta this.
With all due respect, he should have said
I'm gonna have to engineer the shit outta this.
There is a difference between science and engineering, ya know. Or to paraphrase a classic Star Trek exchange:
I'm a botanist, not an engineer!
Now you're an engineer!
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Okay, went to see the movie last night.
Enjoyable and engaging. I had no problem staying awake throughout, even though the session started at 9.20pm and I'd had only a few hours sleep the night before.
But sometimes I felt it lacked emotion. Compared to Ed Harris's Gene Kranz in "Apollo 13" wearing his heart on his sleeve, many of the NASA characters in "The Martian" come across as bored rather than inspired by the part they're playing in the manned exploration of Mars (or the rescue of Watney): Teddy the Director, Bruce Ng, Mitch Henderson and to a lesser extent Vincent (and Kristen Wiig seemed to be channelling Allison Janney's character from "The West Wing"). Also the five surviving astronauts seemed a little emotionless during their own launch, despite the sudden loss of Watney and their own narrow escape. It seems to take the crowd shots to set the emotional mood in tense scenes. Lastly, the post-rescue scenes of Watney on Earth seemed a little anti-climactic.
But there was plenty to like too: I enjoyed feeling as well as hearing and seeing the MAV launches (I watched a Shuttle launch filmed from close-up at an IMAX cinema so it was good to experience that effect re-created). I liked the portrayal of the Hermes and the changes from the weightless spine to the rotating habitats. And I thought the Rover and all the spacecraft had a realistic solidity about them. Plus I enjoyed the moments of humour (Purnell doing the banana-skin gag on loose papers on the floor, Annie Montrose so not getting the LotR references and then objecting when the spacecraft-pen touches down on her head, the many jokes at the expense of disco music). And overall I just enjoyed the scientific solidity of it all (even if they essentially ignored the effect of Mars's lower gravity as Watney moved around in the Hab).
Oh, and are mountains on Mars anything like those in the movie? And could an astronaut make his way around the outside of a spacecraft which was accelerating with an ion drive?
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Okay, went to see the movie last night.
Enjoyable and engaging.
I saw this last week and noticed the dryness of the characters too. It was refreshing. The action was very believable without the emotions and it made me dig a bit to understand the characters better. Best picture of the year.
Spoiler: Sean Bean's character does not die.
That depends on how one feels about golf.
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And could an astronaut make his way around the outside of a spacecraft which was accelerating with an ion drive?
I would think so (assuming there were no issues such as gamma/neutrons from the nuclear reactor from a less-shielded direction). Contemporary ion drives have a thrust of less than one Newton at an energy cost on the order of kilowatts, and achieve very high dV's at very low accelerations.
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And could an astronaut make his way around the outside of a spacecraft which was accelerating with an ion drive?
I suppose that there would be certain exclusion areas outside where the astronaut would not be allowed to venture while on an EVA. Much like a nuclear powered submarine. When I enjoyed swim call on a surfaced sub, we were restricted to the area forward of the sail so that we were kept a good distance from the unshielded portion of the hull around the reactor.
Ranb
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I suppose that there would be certain exclusion areas outside where the astronaut would not be allowed to venture while on an EVA. Much like a nuclear powered submarine. When I enjoyed swim call on a surfaced sub, we were restricted to the area forward of the sail so that we were kept a good distance from the unshielded portion of the hull around the reactor.
Ranb
I had never thought about this. So SSNs rely on the water around the sub for shielding the external environment from the reactor?
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Oh, as a self-respecting EE I should say that I object to the one line in the movie that is rapidly becoming its catchphrase:
I'm gonna have to science the shit outta this.
With all due respect, he should have said
I'm gonna have to engineer the shit outta this.
There is a difference between science and engineering, ya know. Or to paraphrase a classic Star Trek exchange:
I'm a botanist, not an engineer!
Now you're an engineer!
100% agreement.
I told my 14 year old daughter, "learn new skills, master old ones, never take anything for granted" because she balked at my teaching her how to change a tire. It is better to be resourceful than anything else. If you can think outside the box to solve a problem, then you're ten steps ahead of everyone else. Intelligence is not the end-all and be-all. Academic performance only demonstrates how well you take tests. Critical thinking and the ability to apply knowledge is the ticket. So she grumbled all the while she was changing the tire in the backyard last summer. Until this past weekend. She came in from being at a friend's house for the weekend, and her friend's mom had taken them to the movies. Yep, they had a flat. The friend's mom got on her cell to call for roadside assistance, but my daughter got out, popped the trunk, and had the tire changed before the AAA guy even got there. Came back home all puffed up and proud of herself. Not as proud as I was.
Watney didn't really "science" anything. But he engineered everything.
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I had never thought about this. So SSNs rely on the water around the sub for shielding the external environment from the reactor?
There is very little unclassified information on submarine shield design that I can find. But I can say that there is a shielded passageway going through the reactor compartment (RC) for access fore and aft. The shield is also designed to eliminate high radiation levels on the top of the hull above the reactor so that Sailors can work topside.
The thick steel hull attenuates some of the radiation while the reactor is critical. The primary shield greatly reduces radiation levels to the ship's components in the RC, the secondary shield (bulkheads) forward and aft of the RC protects the crew. During the brief periods that a submarine operates in port, the water around the mostly submerged hull protects anyone from the low radiation levels that make it through the steel.
Ranb
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Oh, as a self-respecting EE I should say that I object to the one line in the movie that is rapidly becoming its catchphrase:
I'm gonna have to science the shit outta this.
With all due respect, he should have said
I'm gonna have to engineer the shit outta this.
There is a difference between science and engineering, ya know. Or to paraphrase a classic Star Trek exchange:
I'm a botanist, not an engineer!
Now you're an engineer!
100% agreement.
I told my 14 year old daughter, "learn new skills, master old ones, never take anything for granted" because she balked at my teaching her how to change a tire. It is better to be resourceful than anything else. If you can think outside the box to solve a problem, then you're ten steps ahead of everyone else. Intelligence is not the end-all and be-all. Academic performance only demonstrates how well you take tests. Critical thinking and the ability to apply knowledge is the ticket. So she grumbled all the while she was changing the tire in the backyard last summer. Until this past weekend. She came in from being at a friend's house for the weekend, and her friend's mom had taken them to the movies. Yep, they had a flat. The friend's mom got on her cell to call for roadside assistance, but my daughter got out, popped the trunk, and had the tire changed before the AAA guy even got there. Came back home all puffed up and proud of herself. Not as proud as I was.
Watney didn't really "science" anything. But he engineered everything.
Maybe Watney didn't like Wollowitz...?
ETA: A great story about your daughter.
I'm trying the same thing in small ways with my kids. Our oldest has just turned eight, and because he's profoundly deaf and wears cochlear implants, he has a "hearing bag" with implant-related things he has to take to school (spare batteries, FM receiver, FM microphone and so on). It's his responsibility to collect all these things at the end of the school day and put them in his hearing bag to bring home each day, and he's really quite good about it. He also knows how to change the batteries if that needs to be done.
We've also been reminding him that it's his job to tell his teacher when there's a problem of some sort, and to explain the problem; in other words, he has to be his own advocate - he can't rely on us to solve his problems all the time. And as time goes by he's going to have to start taking responsibility for disassembling his implants at bed-time, putting the batteries on to charge and putting the other components in the drying box.
He's still the dreamy-headed eight-year-old in other respects, but hopefully pushing this problem-solving side of things and praising him when he does it will spread to other aspects of his life.
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And could an astronaut make his way around the outside of a spacecraft which was accelerating with an ion drive?
I would think so (assuming there were no issues such as gamma/neutrons from the nuclear reactor from a less-shielded direction). Contemporary ion drives have a thrust of less than one Newton at an energy cost on the order of kilowatts, and achieve very high dV's at very low accelerations.
Yeah, I was thinking solely from the point of view of acceleration, not radiation.
It's just that, given how risk-averse NASA is these days (and presumably likely to get even more so in the future) I wondered whether their SOP would be for no EVAs while the engine was lit.
And now another question comes to mind: what would the trajectory of the Hermes look like as it breaks out of orbit (either of Earth or Mars)? Given the acceleration is small but constant, I assume it would look like some sort of spiral? Would the presence of the Moon be an issue to deal with? And from the time the engine is lit while in Earth orbit, how long would it take to reach escape velocity? Hours? Days?
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Well if Hermes would need a delta V of 3.6 kps, at 2 mm/second squared it would take nearly 50 hours to get to escape velocity. If it takes a month or two to get to Mars, two days in Earth orbit isn't a big deal.
Ranb
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So SSNs rely on the water around the sub for shielding the external environment from the reactor?
Water is an excellent radiation shield.
The gamma dose from a bundle of spent reactor fuel (especially if it's freshly out of the reactor) would quickly give a lethal dose to anyone nearby, but they are regularly handled underwater in spent fuel pools with workers standing next the pool. A few meters of water makes all the difference.
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Water is an excellent radiation shield.
The gamma dose from a bundle of spent reactor fuel (especially if it's freshly out of the reactor) would quickly give a lethal dose to anyone nearby, but they are regularly handled underwater in spent fuel pools with workers standing next the pool. A few meters of water makes all the difference.
Yes, I wasn't necessarily critiquing the design decision. BTW, I suppose any reactor-powered stealth platform will be obsolete when sufficiently accurate neutrino detectors are developed?
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Unless somebody figures out a much better way to shield neutrinos.
Of course, the same property of the neutrino that makes it hard to shield makes it hard to detect. Works both ways.
As I understand it, it's not fission itself that generates neutrinos, it's the beta decay of (most of) its fission products. More accurately, it generates anti-neutrinos.
So you'd want to get rid of your fission products as quickly as possible, before they decay inside the reactor. One way to do that is with a nuclear fission-fragment rocket. You make the fuel thin enough that most of the fragments can directly escape the fuel, then use strong electric and/or magnetic fields to deflect these positively-charged ions out the back as your reaction mass. With each fission releasing about 200 MeV, Isp can be quite high.
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I suppose that there would be certain exclusion areas outside where the astronaut would not be allowed to venture while on an EVA. Much like a nuclear powered submarine. When I enjoyed swim call on a surfaced sub, we were restricted to the area forward of the sail so that we were kept a good distance from the unshielded portion of the hull around the reactor.
Ranb
I had never thought about this. So SSNs rely on the water around the sub for shielding the external environment from the reactor?
I am surprised at this, as ship reactors are heavily shielded in all directions. They have to be, as they come along side in harbours, and also have to be protected against collision.
Mass is not an issue in ships, and SNNs displace thousands of tonnes.
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While the neuron shield surrounds the reactor on the sides and the top, the coolant loops are not shielded 100%. All water cooled reactors emit lots of N-16 which has a half-life of only 7 seconds but produces high energy gammas that are the primary source of radiation penetrating the secondary shields.
Mass is still an issue with the shields weighing hundreds of tons. Image how submarine performance would be affected if only the forward shield was in place to protect the crew (with the propulsion plant operated remotely) and nothing for the aft and outboards areas. The weight savings could be directed towards a more powerful reactor/turbines or for a thicker hull for greater operating depth.
Ranb
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I went to see the movie with my daughter. We both enjoyed it a lot.
I was bit bothered about flapping tarp holding pressure and surviving the abrasion from martian sand storms. Another obvious mistake was sunlit parts of the Hermes and stars in the same shot but I guess a space movie can't avoid that :-\
I was left wondering about rotating artificial gravity compartment. Wouldn't it act like gyroscope and resist all attempts at changing attitude? I didn't see any contra-rotating weights. Would such gyroscopic forces damage the ship if attitude was forcefully changed?
Lurky
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I was left wondering about rotating artificial gravity compartment. Wouldn't it act like gyroscope and resist all attempts at changing attitude?
That occurred to me too. A simple fix is to have two counter-rotating artificial gravity wheels.
It's not so much the difficulty of changing the attitude of the wheel once it is turning, it's the difficulty of getting it to turn in the first place. You'd either spend a lot of fuel on thrusters, or put a thruster on the end of a very long boom, or spin up and fling off some counterweights. The latter method is routinely used to despin spent upper stages of the Delta launch vehicle.
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I was left wondering about rotating artificial gravity compartment. Wouldn't it act like gyroscope and resist all attempts at changing attitude? I didn't see any contra-rotating weights. Would such gyroscopic forces damage the ship if attitude was forcefully changed?
Lurky
Firstly, the gyroscopic effect doesn't so much "resist" change in attitude as cause the attitude to change in a different direction to the applied force. The rule is that when a force is applied to a gyroscope to change its spin axis, the resulting motion is in the same direction as the force, but 90° in the direction of rotation.
(https://dl.dropboxusercontent.com/u/98915197/ApolloHoax/WeirHermes.jpg)
I can't remember which way the Hermes centrifuge spun, but if it was in the direction of the yellow arrow, and thrust was applied in the direction of the red arrows, then the spacecraft would yaw in the direction of the green arrows. Of course you are right that the shape of the spacecraft (long and narrow) would have a very large "moment of inertia", and too much thrust could wreck it.
Secondly. IIRC, in the movie, they de-spun the centrifuge during retro-firing and course corrections, so I imagine that it would also be de-spun for attitude changes.
Anyone know if NASA took gyroscopic effect into account in Apollo when they used the 'barbecue roll". I imagine they would need either take it into account or de-spin the spacecraft when making course corrections.
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So having another artificial gravity compartment or counterweight contra-rotating the gravity compartment would simplify maneuvers and remove fuel expenditure in spinning up and down gravity compartment(s). But gyroscopic effects can be taken care of in astrogation software and all that extra weight would require extra fuel for every acceleration or deceleration. So having just one rotating compartment is plausible?
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So having another artificial gravity compartment or counterweight contra-rotating the gravity compartment would simplify maneuvers and remove fuel expenditure in spinning up and down gravity compartment(s). But gyroscopic effects can be taken care of in astrogation software and all that extra weight would require extra fuel for every acceleration or deceleration. So having just one rotating compartment is plausible?
I can't see any reason why not. A second rotating compartment would be additional expense, mass (that would need to be lifted to orbit for construction) and complication. Would the fuel savings offset the additional hassle?
Also, a contra-rotating centrifuge will not make the gyroscopic effect go away. Each centrifuge will have the gyroscopic effect pulling in opposing directions. There would be a lot of additional stress on any part of the spacecraft structure between them, effectively the stresses would be doubled as the gyroscopic effect of any attitude change would pull the intermediate parts of the spacecraft in opposite directions. The two centrifuges would have to be positioned right alongside each other.
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Also, a contra-rotating centrifuge will not make the gyroscopic effect go away. Each centrifuge will have the gyroscopic effect pulling in opposing directions. There would be a lot of additional stress on any part of the spacecraft structure between them, effectively the stresses would be doubled as the gyroscopic effect of any attitude change would pull the intermediate parts of the spacecraft in opposite directions. The two centrifuges would have to be positioned right alongside each other.
I imagined the centrifuges being side by side.
Lurky
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So having another artificial gravity compartment or counterweight contra-rotating the gravity compartment would simplify maneuvers and remove fuel expenditure in spinning up and down gravity compartment(s).
In space flight fuel (i.e., propellant) expenditure is everything. It's even more important than energy since solar panels can generate arbitrary amounts of energy (if you wait long enough).
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So having another artificial gravity compartment or counterweight contra-rotating the gravity compartment would simplify maneuvers and remove fuel expenditure in spinning up and down gravity compartment(s).
In space flight fuel (i.e., propellant) expenditure is everything. It's even more important than energy since solar panels can generate arbitrary amounts of energy (if you wait long enough).
AIU Weir's concept, Hermes in normal operation is on a sort of Mars Recycler. Its main engines are Ion Thrust fuelled by electrostatically-charged argon. It would be these Ion engines that are used for TMI/TEI and MOI/EOI at each end of the journey
Its manoeuvring (Attitude Thrust) engines use oxygen/hydrazine rocket fuel. If the Hermes orbital mechanics works as Weir is suggesting then propellant isn't really a great issue because the propellent used for course corrections would be the same propellant used for de-spinning and spinning up the centrifuge, and not the same propellant used for entering and leaving orbit.
So, the debate here is, would the propellant expenditure saved by not having to de-spin the artificial gravity centrifuge in order to make course corrections without compensating for gyroscopic effect, be offset by the additional mass (and therefore more propellant needed) of an extra centrifuge. Also keep in mind that the additional complication of having two counter-rotating centrifuges will make construction problematic with the additional stress of having two opposing gyroscopic effects, and that may require additional structural strength, and therefore additional mass.
Its easy to see why rocket science isn't easy!
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My thoughts about this type of spacecraft is the viability of rotating air seals for a long duration flight. Particularly the wear on bearings or other mechanism over that long of a time that will ultimately cause some wobble and degradation of the airtightness. I can imagine some of the wobble problem could be taken care of by a tuned mass in the extremity of the rotating section, but degradation of seals would occur, it is just a matter of how fast. One supposes this could be a maintenance item corrected by depressurizing part of the ship to adjust bearings and replace seals.
This would, it seems to me, argue against a more complex counter rotating scheme which would require additional seal and bearing structures to be maintained.
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Good point about the seals. The other problems of rotating joints such as getting electrical connections across, are not that difficult. Rotary transformers work well.
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Speaking of rotary habitats, one thing I would really like to see them do in one of these movies is to depict someone jogging around one opposite its direction of rotation, and then lifting his legs and just continuing around.
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In the movie all Hermes's crew spaces were one continuous room which requires airtight seals.
Could the seals be bypassed using pressurised "elevator"? One would move from 0g compartment through airlock to "elevator", the "elevator" would detach and match the spinning of centrifuge and move to 1g compartment which is entered through another airlock. Air seals would exist only to block hard vacuum entering the "elevator" area.
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Speaking of rotary habitats, one thing I would really like to see them do in one of these movies is to depict someone jogging around one opposite its direction of rotation, and then lifting his legs and just continuing around.
How would this happen?
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How would this happen?
They would be stationary relative to the non-rotating spacecraft core, but appear to be moving relative to the spinning artificial gravity hab.
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Speaking of rotary habitats, one thing I would really like to see them do in one of these movies is to depict someone jogging around one opposite its direction of rotation, and then lifting his legs and just continuing around.
Mission to Mars?
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How would this happen?
They would be stationary relative to the non-rotating spacecraft core, but appear to be moving relative to the spinning artificial gravity hab.
Because they are under tangential acceleration until the moment they lift their legs they'll rapidly hit the deck.
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The jogging scenario would require a very loose definition of jogging.
Wouldn't a jogger "continuing around" already have to be in relative weightlessness, to the deck, before lifting his feet. Which would have made even the slightest prior foot contact send him away from the surface. Or perhaps he could use his last step to null out the motion, but that seems practically improbable.
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The jogging scenario would require a very loose definition of jogging.
Wouldn't a jogger "continuing around" already have to be in relative weightlessness, to the deck, before lifting his feet. Which would have made even the slightest prior foot contact send him away from the surface. Or perhaps he could use his last step to null out the motion, but that seems practically improbable.
That depends on how much artificial gravity is generated by the rotation.
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That depends on how much artificial gravity is generated by the rotation.
To continue around, the jogger would have to be a zero motion relative to the space craft while the wheel spun around him. From watching long shot clips from the space station, zero motion seems practically impossible for a person to achieve as the slightest touch sends one into motion. Now add the "jogging" effort of opposing the motion of the wheel and it becomes even "more impossible." If you get my drift.
Adding some motion allowance for the theatrics of the situation would give some room, but nulling the jogging motion to achieve relative zero g seems impractical. Perhaps it is a performance skill would could learn with practice. Under that loose definition of jogging.
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That depends on how much artificial gravity is generated by the rotation.
To continue around, the jogger would have to be a zero motion relative to the space craft while the wheel spun around him. From watching long shot clips from the space station, zero motion seems practically impossible for a person to achieve as the slightest touch sends one into motion. Now add the "jogging" effort of opposing the motion of the wheel and it becomes even "more impossible." If you get my drift.
Adding some motion allowance for the theatrics of the situation would give some room, but nulling the jogging motion to achieve relative zero g seems impractical. Perhaps it is a performance skill would could learn with practice. Under that loose definition of jogging.
"To continue around?" are you asking if the jogger remains in the same spatial relative position or complete a course around the circumference?
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A lot would depend on the diameter of the centrifuge and how fast it was spinning. The faster it is spinning, the higher the gravity; the larger the diameter the less steep the centrifugal force gradient will be. If it was large enough, then a person would be able to run around the inside in much the same way that they would run on earth because the centrifugal force gradient near the inside surface would be very low and the direction of the person's "local" gravity would always be "downwards" relative to their body. Losing contact with the "floor" would not make the person weightless because the radial vector of their absolute motion would ensure they were thrown outwards (conservation of angular momentum?)
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The jogging scenario would require a very loose definition of jogging.
Wouldn't a jogger "continuing around" already have to be in relative weightlessness, to the deck, before lifting his feet. Which would have made even the slightest prior foot contact send him away from the surface. Or perhaps he could use his last step to null out the motion, but that seems practically improbable.
(As two astronauts pass each other): "You know you're just cheating yourself by jogging counterclockwise, Carl."
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The jogging scenario would require a very loose definition of jogging.
Wouldn't a jogger "continuing around" already have to be in relative weightlessness, to the deck, before lifting his feet. Which would have made even the slightest prior foot contact send him away from the surface. Or perhaps he could use his last step to null out the motion, but that seems practically improbable.
(As two astronauts pass each other): "You know you're just cheating yourself by jogging counterclockwise, Carl."
This is the definitive answer to the question.
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"To continue around?" are you asking if the jogger remains in the same spatial relative position or complete a course around the circumference?
The continue around was meant to say the astronaut would appear to move around from the perspective of the circumference as a the fixed reference. Such as one might get from a video camera.
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"To continue around?" are you asking if the jogger remains in the same spatial relative position or complete a course around the circumference?
The continue around was meant to say the astronaut would appear to move around from the perspective of the circumference as a the fixed reference. Such as one might get from a video camera.
With the circumference rotating under his jogging body.
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I saw it last night. Really good. I thought they got Matt Damon's tone just right. Not too grim, but not too flippant either.
It got rather schlocky at the end though.
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I saw it last night. Really good. I thought they got Matt Damon's tone just right. Not too grim, but not too flippant either.
It got rather schlocky at the end though.
What aspect?
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The Ironman crap and Lewis jumping in at the last second to use the MMU to save Watney instead of sticking to the plan and using Beck for the rescue.
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The Ironman crap and Lewis jumping in at the last second to use the MMU to save Watney instead of sticking to the plan and using Beck for the rescue.
Yeah basically.
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Watched it with my 10 yr old last weekend. Pleased to find he found it engaging. Also pleased that he recognized the absurdity of the plastic enclosure drumming in the Martian wind ~2/3 of the way through the movie.
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Yes that was wrong, but at least they acknowledged that habitats don't need to be rigid.
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A lot of nits in that movie all have to do with atmospheres. Not just the Martian atmosphere being able to blow over a spacecraft (or blow inward a thin polyethylene sheet over the habitat door) but the choice of atmosphere in the habitat and space suits.
They apparently used ordinary air, which makes very little sense. I have yet to see a flexible pressure suit use anything but pure O2 at low pressure, and even they are famously stiff and fatiguing to work in. Nor would the habitat be using air; it would have to be considerably heavier to do so, and that's the last property you'd want to have to carry to Mars.
You'd also want the habitat atmosphere to be the same as in the suits, otherwise you'd have to go through a lengthy prebreathing procedure every time you did an EVA, just as they have to do on the ISS and did on the Shuttle. It's acceptable there because EVAs are uncommon, but it was clear that the astronauts on Mars did most of their work during EVAs.
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And if they used 1/3 bar pure oxygen then that airlock "malfunction" wouldn't have been so catastrophic.
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And if they used 1/3 bar pure oxygen then that airlock "malfunction" wouldn't have been so catastrophic.
I think the pressure for pure O2 corresponding to the same ppO2 as sea level air on earth would be even lower, about 210 mb. But that's still a lot of pressure. A 2-meter diameter circular piece of polyethylene sheeting would still be subjected to
pi*(1)2 * 0.21e+5 N/m2
= ~ 66 kN
That's a lot of force: the earth weight of a 6700 kg mass.
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There is still the fire hazard problem for any large spacecraft or habitat that uses pure O2, even at the same partial pressure as sea level air on earth. The presence of nitrogen (and argon) diminishes the fire hazard by carrying away heat.
The Apollo program was never able to completely eliminate the risk of fire even after a major campaign to minimize potential fuels. They added N2 to the prelaunch atmosphere, but there was no practical alternative to pure O2 during flight.
And that was just a small capsule carrying three guys who didn't have to do much on the way. A working Mars habitat would be a lot bigger (like the fictional one here) and have more people, more activities and a lot more material that could potentially burn. I'm not sure how you would mitigate the fire risk here without adding a diluent gas that would increase the total pressure, make the structure heavier, and complicate EVAs. One possibility is to inert as many of the equipment and storage areas as possible with argon or nitrogen at the same pressure as the living areas. You could work in those areas in shirtsleeves if you wear an oxygen mask. But there would still be a serious risk of accidental suffocation. You get no warning when you breathe an inert atmosphere; you just pass out.
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And if they used 1/3 bar pure oxygen then that airlock "malfunction" wouldn't have been so catastrophic.
Perhaps not, but his first attempt to make rain inside his "greenhouse" might have been.
Overall, I think the science in this movie was so good that we really are looking a lot harder to find fault and nitpicking some minor technicalities which we would not even bother with for other films since they are often making monumental errors in the science. e.g., Mission to Mars and the "abandon ship" scene which was great from a drama and tension perspective, but complete rubbish with regard to orbital mechanics. Contrast that with the Rich-Purnell manoever, from The Martian, which is not fictional and is completely sound from an orbital mechanics point of view. Nozomi, a failing Mars probe lanched by Japan in 1998 used a similar Earth-flyby trajectory in a second attempt to get to Mars after electrical failures crippled it.
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Yup. Though I have problems with his water-making method too....
Hydrazine is extremely toxic. He probably should have poisoned himself doing what he did.
If you just want to convert hydrazine into water, there's no need to decompose it first; just burn it directly. Decomposing it tends to make a mixture of nitrogen, hydrogen and ammonia. Ammonia has a negative enthalpy of formation meaning it's more stable than hydrazine (which is positive) and therefore somewhat harder to burn. But even ammonia is much less toxic than hydrazine.
That said, a large rocket engine would not be using straight hydrazine as fuel, especially not when it has to sit for months on a cold planet like Mars. Straight hydrazine freezes at +1C, and the same property that makes it useful in monopropellant thrusters (catalytic decomposion) makes it less than desirable for regenerative cooling, an important design feature of most larger rocket engines. They would be using either Aerozine-50 (50-50 mixture of straight hydrazine and UDMH, used by the larger Apollo spacecraft engines) or more likely monomethyl hydrazine. Both contain carbon that would quite likely produce toxic amounts of carbon monoxide unless burned very carefully in a surplus of oxygen.
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Overall, I think the science in this movie was so good that we really are looking a lot harder to find fault and nitpicking some minor technicalities which we would not even bother with for other films since they are often making monumental errors in the science.
Absolutely. Nitpicking is an expression of love.