Weir's The Martian.

[Dalhousie]

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.

[Dalhousie]

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.

[ka9q]

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...

[ka9q]

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."

[ka9q]

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?

[VQ]

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.

[smartcooky]

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.

[Grashtel]

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.

[ka9q]

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?

[Grashtel]

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

[ka9q]

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.

[VQ]

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.

[ka9q]

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!

[Peter B]

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?

[Echnaton]

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.