Author Topic: eevBLAB#15 - The Martian Movie Review  (Read 48267 times)

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Online coppice

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Re: eevBLAB#15 - The Martian Movie Review
« Reply #150 on: July 11, 2018, 05:15:59 am »
"The first cellular analysis of muscles from astronauts who have spent 180 days at the International Space Station shows that their muscles lost more than 40 percent of their capacity for physical work, despite in-flight exercise.

No matter how good their shape was before the astronauts left, they returned with muscle tone that resembled that of the average 80-year-old. In fact, the astronauts who were in the best shape before they launched were the most likely to come back with withered, or atrophied, muscles.

NASA currently estimates it would take a crew 10 months to reach Mars

So? You make a ship with artificial gravity (by spinning it).
You have to make a really big ship for that to work well. If the ring you spin is much less than a kilometre across the difference in centripetal force between your head and your feet will make you constantly queasy. 2001 tried to be pretty realistic, but although the huge space station around the Earth was so big it would have provided a practical synthetic gravity, the ship to Jupiter would have been problematic.
 

Online Fungus

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Re: eevBLAB#15 - The Martian Movie Review
« Reply #151 on: July 11, 2018, 08:16:32 am »
So? You make a ship with artificial gravity (by spinning it).
You have to make a really big ship for that to work well. If the ring you spin is much less than a kilometre across the difference in centripetal force between your head and your feet will make you constantly queasy.

How about .... two small ships joined by a piece of string?  Would that work for you? :popcorn:
« Last Edit: July 11, 2018, 07:27:11 pm by Fungus »
 

Online Nusa

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Re: eevBLAB#15 - The Martian Movie Review
« Reply #152 on: July 11, 2018, 10:26:07 am »
So? You make a ship with artificial gravity (by spinning it).
You have to make a really big ship for that to work well. If the ring you spin is much less than a kilometre across the difference in centripetal force between your head and your feet will make you constantly queasy.

I suspect that's only a short-term problem on smaller rings, much like ocean sea-sickness is for most. After the first day or two your body/mind adapts to it and it stops being a problem. Also, you'd only have to lie down to relieve the symptoms of having your head and feet at different levels.
 

Offline GK

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Re: eevBLAB#15 - The Martian Movie Review
« Reply #153 on: July 11, 2018, 07:05:13 pm »
And Mars itself is NOT a zero-gravity situation.



It doesn't have to be a zero gravity situation. A 62% reduction in gravity is hardly an insignificant reduction as far as human physiology is concerned. There is no way that even Arnold Schwarzenegger from his Mr Universe days could spend 575 earth days on Mars on a starvation diet that wouldn't by a long shot give a calorie surplus to sustain any kind of worthwhile strength training without ending up with the physique of Mr Burns from the Simpsons.
« Last Edit: July 11, 2018, 07:08:46 pm by GK »
 

Online coppice

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Re: eevBLAB#15 - The Martian Movie Review
« Reply #154 on: July 11, 2018, 07:52:42 pm »
It doesn't have to be a zero gravity situation. A 62% reduction in gravity is hardly an insignificant reduction as far as human physiology is concerned. There is no way that even Arnold Schwarzenegger from his Mr Universe days could spend 575 earth days on Mars on a starvation diet that wouldn't by a long shot give a calorie surplus to sustain any kind of worthwhile strength training without ending up with the physique of Mr Burns from the Simpsons.
I wonder how much astronaut health has taught us about how the human body would react to a wide range of levels of gravity? We seem to only have results for 0G and 1G. I suspect anyone heading to Mars will be heading very much into the unknown, and will be a heck of a long way from a decent hospital.
 

Online Nusa

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Re: eevBLAB#15 - The Martian Movie Review
« Reply #155 on: July 12, 2018, 05:16:50 am »
What Coppice said.

I never said it was insignificant, I merely said it is probably not as bad as you suggest. Straight-line approximations between 0g and 1g are probably wrong IMO, but we are short on empirical data points to create the correct curve.
 

Offline GK

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Re: eevBLAB#15 - The Martian Movie Review
« Reply #156 on: July 16, 2018, 11:31:56 pm »
Yawn. Gravity is the one thing that has been basically constant for all of human evolution. Sure there are unknowns, but one of them certainly is not that long term exposure to just 0.38g will result in, amongst other things (reduced bone density, reduced circulatory health, etc), a significant degree of muscle atrophy. How completely any deleterious effects of 0.38g can be effectively countenanced in the long term is anyone's guess for now - but a starvation potato diet certainly isn't going to make any future suggested cures list.

Online Fungus

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Re: eevBLAB#15 - The Martian Movie Review
« Reply #157 on: July 16, 2018, 11:40:14 pm »
a starvation potato diet certainly isn't going to make any future suggested cures list.

Presumably we'd send some extra food and vitamins along, too.

(Even The Martian had real food until it ran out...)

Or we can send Bear Grylls, he'll find something to eat on Mars.
 

Offline apis

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Re: eevBLAB#15 - The Martian Movie Review
« Reply #158 on: July 23, 2018, 10:15:23 pm »
So? You make a ship with artificial gravity (by spinning it).
You have to make a really big ship for that to work well. If the ring you spin is much less than a kilometre across the difference in centripetal force between your head and your feet will make you constantly queasy.

How about .... two small ships joined by a piece of string?  Would that work for you? :popcorn:
Yes, you don't need a gigant ring for spingravity, just a long wire and a counterweight.
 

Online coppice

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Re: eevBLAB#15 - The Martian Movie Review
« Reply #159 on: July 24, 2018, 05:16:15 am »
So? You make a ship with artificial gravity (by spinning it).
You have to make a really big ship for that to work well. If the ring you spin is much less than a kilometre across the difference in centripetal force between your head and your feet will make you constantly queasy.

How about .... two small ships joined by a piece of string?  Would that work for you? :popcorn:
Two small space stations connected by a cable is a scheme found in several sci-fi stories. It should be fine once you are in there, but getting in and out could be a pain. Two ships connected by a tube, with some kind of docking bay at the middle of the tube seems more realistic. Then you can dock reasonably easily, by spinning your ship until it syncs with the station, ala 2001. If the tube is long enough the spin speed should be low enough not to make everyone vomit during docking - although it would probably be fairly disorienting for most people.

Making a ship like this could be more problematic. If both the pair of connected ships have comparable drive systems, and run them in accurate synchronisation, they could accelerate the structure orthogonal to direction of spin. Any mismatch in the two drive units could produce some funky high stress results, though.
 

Online Fungus

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Re: eevBLAB#15 - The Martian Movie Review
« Reply #160 on: July 24, 2018, 07:54:31 pm »
Making a ship like this could be more problematic. If both the pair of connected ships have comparable drive systems, and run them in accurate synchronisation, they could accelerate the structure orthogonal to direction of spin. Any mismatch in the two drive units could produce some funky high stress results, though.

You normally wouldn't be landing/docking while spinning and course corrections are very tiny if done early.

I imagine the biggest problem would be slowing it down when you arrive but really it's just math and fuel calculations. I wonder if weight could be transferred from one side to the other along the cable. This would move the main ship towards the center of mass. This could be followed by reeling in the cable with a bit of weight left on it. The "reeling in" could cancel a lot of the spin of the main craft using just electric motors, no fuel needed.

 


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