Author Topic: Weir's The Martian.  (Read 69422 times)

Offline bknight

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Re: Weir's The Martian.
« Reply #135 on: December 31, 2015, 10:53:40 AM »
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.
Truth needs no defense.  Nobody can take those footsteps I made on the surface of the moon away from me.
Eugene Cernan

Offline Echnaton

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Re: Weir's The Martian.
« Reply #136 on: December 31, 2015, 11:27:21 AM »

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.
The sun shone, having no alternative, on the nothing new. —Samuel Beckett

Offline bknight

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Re: Weir's The Martian.
« Reply #137 on: December 31, 2015, 11:34:45 AM »

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?
Truth needs no defense.  Nobody can take those footsteps I made on the surface of the moon away from me.
Eugene Cernan

Offline smartcooky

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Re: Weir's The Martian.
« Reply #138 on: December 31, 2015, 02:56:51 PM »
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?)
If you're not a scientist but you think you've destroyed the foundation of a vast scientific edifice with 10 minutes of Googling, you might want to consider the possibility that you're wrong.

Offline VQ

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Re: Weir's The Martian.
« Reply #139 on: December 31, 2015, 07:31:04 PM »
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."

Offline Echnaton

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Re: Weir's The Martian.
« Reply #140 on: January 01, 2016, 01:54:21 PM »
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. 
The sun shone, having no alternative, on the nothing new. —Samuel Beckett

Offline Echnaton

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Re: Weir's The Martian.
« Reply #141 on: January 01, 2016, 01:57:58 PM »
"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. 
The sun shone, having no alternative, on the nothing new. —Samuel Beckett

Offline bknight

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Re: Weir's The Martian.
« Reply #142 on: January 01, 2016, 02:13:37 PM »
"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.
Truth needs no defense.  Nobody can take those footsteps I made on the surface of the moon away from me.
Eugene Cernan

Offline Glom

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Re: Weir's The Martian.
« Reply #143 on: May 22, 2016, 10:17:56 AM »
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.

Offline Dalhousie

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Re: Weir's The Martian.
« Reply #144 on: May 24, 2016, 04:36:44 AM »
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?

Offline Ranb

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Re: Weir's The Martian.
« Reply #145 on: May 24, 2016, 12:41:15 PM »
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.

Offline Glom

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Re: Weir's The Martian.
« Reply #146 on: May 24, 2016, 06:35:13 PM »
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.

Offline VQ

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Re: Weir's The Martian.
« Reply #147 on: May 24, 2016, 08:43:06 PM »
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.

Offline Glom

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Re: Weir's The Martian.
« Reply #148 on: May 25, 2016, 05:25:51 AM »
Yes that was wrong, but at least they acknowledged that habitats don't need to be rigid.

Offline ka9q

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Re: Weir's The Martian.
« Reply #149 on: May 25, 2016, 04:14:35 PM »
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.