Catching Some Z's - How to sleep in low to no gravity?

Palomar · 2002-07-12 11:32:21

*Thought I'd put this here, rather than in Free Chat. Hopefully it's okay here.

I've been wondering just how Mars Direct folk are going to be able to sleep on beds if there's no gravity in the spaceship, or if there's fractional gravity due to a rotating spaceship? Maybe a person with enough weight even in Marsian-strength gravity could rest fully against a bed, but I'm wondering. Arthur C. Clarke mentioned in one of his novels people more or less being gently strapped down to their beds by lightly weighted webs of material. I'm a very fussy sleeper, and move around a lot at night, so this has been on my mind especially. I'd probably be bleary-eyed the entire trip!

Speaking of the beds in the spaceship, I think they should be designed like futons: For use as a sofa during the "day" and as a bed at "night." This would give each astronaut some flexibility with their private quarters; and it's easier to read or watch a video program sitting up on a comfy sofa rather than sitting on a bed.

Just wonderin'...

--Cindy

Byron · 2002-07-12 13:56:36

I've been wondering just how Mars Direct folk are going to be able to sleep on beds if there's no gravity in the spaceship, or if there's fractional gravity due to a rotating spaceship? Maybe a person with enough weight even in Marsian-strength gravity could rest fully against a bed, but I'm wondering. Arthur C. Clarke mentioned in one of his novels people more or less being gently strapped down to their beds by lightly weighted webs of material. I'm a very fussy sleeper, and move around a lot at night, so this has been on my mind especially. I'd probably be bleary-eyed the entire trip!
Speaking of the beds in the spaceship, I think they should be designed like futons: For use as a sofa during the "day" and as a bed at "night." This would give each astronaut some flexibility with their private quarters; and it's easier to read or watch a video program sitting up on a comfy sofa rather than sitting on a bed.
Just wonderin'...
--Cindy

Hey...

If the Mars Direct spacecraft have no artificial gravity (rotating using a tether system), then there would be no way the travelers could "lay" down on a bed, as there would be no "downward" pressure to make this possible (unless webbed material is used to "strap" into a bed. Instead, they would probably do what is done on the Space Shuttle and ISS currently...sleep in webbed sleeping "bags" attached to the ceiling and floor in an upright fashion (to save on space).

Sleep is not easy to come by in microgravity...I think most astronauts sleep less than 6 hours per night. However, on Mars, there is enough gravity to make sleeping in beds practical, and indeed, sleeping in .38 g should be more comfortable than a full g, although we won't know until we get there...lol..

B

Shaun Barrett · 2002-07-13 00:06:27

Byron has summed up the situation well .... as we've come to expect from him.
I would just like to add it's my strongly-held belief that with 6 month travel times to Mars and back, artificial gravity is essential. And I'm inclined to think a tethered arrangement allowing a full 1g for most of the outward trip is highly desirable ... perhaps reducing the rate of rotation down to 0.38g in the last stages to allow for acclimatisation.
In addition, the reverse process should be applied on the return journey ... starting at 0.38g and increasing the rotation rate in stages to reach full Earth gravity shortly before arriving home.
I know, I know! This isn't the first time I've preached this gospel, but I believe its importance can't be over-emphasised for the health of the crew and the success of the mission.
Imagine a mission with no attempt made at artificial gravity. The crew would spend approximately 180 days in zero-g, 500 days in 0.38g (on Mars), and then another 180 days in zero-g again. ...... Then you expect them to survive high g-forces re-entering Earth's atmosphere, and full Earth gravity when they step (read crawl) out of the landing vehicle!! I strongly suspect some, if not all, of the crew would simply be unable to adapt and would probably die.
And besides ... we wouldn't want Cindy to be all bleary-eyed, would we!!

Byron · 2002-07-13 08:23:31

I know we all realize the importance of artificial gravity...but the idea of a tethered spacecraft is more complex and problem-prone than most people might expect...like what happens when a course correction needs to be made? The rotation would have to be stopped, the tether reeled in, the rockets fired for the course correction, and then the whole process is reversed to regain artifcial grav again. All this would greatly add to the risk of something going wrong...

In addition, we would have to spend big bucks on a test mission to see how a tethered system works, which will add to the overall mission cost, of course. My take on this is: Take the "extra" money that would be used to test and implement an artificial gravity system, and use that to "buy" more delta-v on the trip to Mars and back. If the astronants can make it to Mars in, let's say four months as opposed to six, that would mean that they would only have to spend a total of only eight months in micro-gravity..which is much less than the proven stays of endurance on the space station Mir.

Of course, you still have the 500 days of .38 g to contend with, but I think the astronants will be able to deal with that without significant difficulty, especially with all the exercise they'd be getting, as opposed to being cooped up in a tiny spacecraft for months on end.

Also, I think special exercise suits could be developed to simulate the pull of gravity to a fairly significant degree..all they've used in the orbiting platforms is a simple treadmill with bungee cords..I know we can do better than that to maintain shipboard health in micro-g.

B

Phobos · 2002-07-13 16:56:46

I know we all realize the importance of artificial gravity...but the idea of a tethered spacecraft is more complex and problem-prone than most people might expect...like what happens when a course correction needs to be made? The rotation would have to be stopped, the tether reeled in, the rockets fired for the course correction, and then the whole process is reversed to regain artifcial grav again. All this would greatly add to the risk of something going wrong...

I wonder if nausea would be a problem on a ship that produces gravity via centrifugal force. It would suck being motion sick all the way to Mars. Or maybe they could invest in some of those seasickness patches that go behind the ears.

In addition, we would have to spend big bucks on a test mission to see how a tethered system works, which will add to the overall mission cost, of course. My take on this is: Take the "extra" money that would be used to test and implement an artificial gravity system, and use that to "buy" more delta-v on the trip to Mars and back. If the astronants can make it to Mars in, let's say four months as opposed to six, that would mean that they would only have to spend a total of only eight months in micro-gravity..which is much less than the proven stays of endurance on the space station Mir.

If the money could be spent on getting the astronauts to Mars months earlier, that would definately be the proper route. I think it would be good from a psychological standpoint to. As one cosmonaut said, stuffing a group of people in a tin can and sending them aloft for seven months will create the perfect conditions for murder. And getting rid of the centrifuge system would reduce a lot of complexity to boot.

Palomar · 2002-07-13 19:24:29

*Well, if the mission goes zero-gravity, that will provide more individual space in the private quarters. All wall space will be utilizable, every inch of the room usable; that might make for happier space campers, instead of being "confined" to the floor.

--Cindy

Aetius · 2002-07-13 20:38:35

I read somewhere that an astronaut said the best sleep she ever got was in microgravity. Hopefully it won't cause many problems, in the event that artificial gravity isn't available.

Shaun Barrett · 2002-07-14 01:19:20

Looks like I'm outvoted on the artificial gravity question! But, for what it's worth, I still maintain that any problems encountered in developing tethered rotating spacecraft dynamics will be less troublesome than the debilitating effects of not spinning the ship.
Naturally, the faster we can get to Mars the less problematic the whole question becomes. Ideally we would use the Israeli concept of "straight through" nuclear thermal americium-based rocket motors and get to Mars in 4 WEEKS! But in the absence of such technology, and using Mars Direct as the mission plan, I believe rotation is the way to go.
Phobos asks about nausea in a 'spun-up' ship. Research indicates that humans can adapt to rotations of up to 4 revs per minute. The faster you can rotate your craft, and the less artificial gravity you require, the shorter you can make your radius of rotation. This has led to the idea of providing 0.38g by using a radius of 22 metres and spinning at 4 revs/minute.
This would mean the crew adapting to some very weird effects (Coriolis effects) for some months, and then suddenly having to adapt back to 'normal' gravity on Mars. a bad idea in my view.
I advocate using a long tether, radius 900 metres, and spinning the craft at only 1 rev/minute. This will give a very natural 1g feel to life onboard with almost unnoticeable Coriolis effects and absolutely no nausea .... and no problems adapting to real gravity at Mars.
The supposed difficulties of spinning up and spinning down the craft are, in my opinion, most likely exaggerated. The concept of orbital rendezvous back in 1963 was seen by some as way too risky to incorporate into the Apollo missions. 4 years later it was routine.
Another benefit of using a spent upper stage as a counterweight and producing artificial gravity is that you have that counterweight with you in the event of a solar storm. You spin down, winch the craft together, and turn the craft so that the spent upper stage acts as a shield between the crewed section and the sun. Some extra material may even be deliberately built into one of the bulkheads to increase the shielding effect. I for one would be comforted to know we were taking our 'parasol' with us on such a hazardous interplanetary trip!
If the counterweight is left in orbit around Mars during the exploration phase, it can be used again on the way home. And wouldn't it be nice to see the astronauts walk off the shuttle looking fit and strong, with no significant bone loss, at the end of 2.5 years away from mother Earth?!
Naturally I have to be content with the will of the majority, but my vote is still with artificial gravity!

Aetius · 2002-07-14 06:55:00

I support the use of artificial gravity as well. I think Zubrin's idea of using the spent rocket booster as a counterweight was a good one.

Shaun Barrett · 2002-11-11 07:00:40

I was browsing on the net the other day and came across some interesting stuff which is relevant to my argument in favour of "setting that sucker on the spin cycle" (to slightly paraphrase Phobos's immortal line! ). In other words relevant to the argument for spinning the Mars Hab to create artificial gravity.

The first article can be found at this site. But for those who don't want to bother reading the whole thing, a couple of the more interesting sections are set out below:-

[When NASA astronauts return to Earth's gravity, about a fourth of them, mostly women, become so weak they have trouble standing. ...
..... "Astronauts are very healthy, vigorously trained individuals", Dr. Richard Summers, the UMC physician leading the project, said Monday. "If space flight is ever going to be a popular thing, these problems have to be overcome"]

The article goes on to say:-

[Space intolerance, or 'orthostasis, is caused by the sudden shift back when the shuttle enters gravity. Summers said symptoms include fatigue, dizziness, dehydration, even fainting.
The longer a person is in space, the more difficult the transition. That makes the prospect of a six-month stay on the space station or a trip to Mars that could take over a year a daunting one.]

A second article, which you can view here, is taken from an address given by Dr. Zubrin at the World Space Congress last month, concerning the Mars Arctic and Desert Research Stations:-

[ Zubrin explained how the physical demands of the type of exploration work done at the stations underscored the need for NASA and ESA to begin substantial research into artificial gravity as the preferred method of travelling to Mars.]

My personal opinion, for what it may be worth, is that "setting that sucker on the spin cycle" is simply not an issue. We shouldn't even contemplate sending astronauts to Mars without spinning the Hab for artificial gravity.
Apart from the health of the people concerned, a weakened crew would certainly endanger the success of the entire mission.
We have no choice but to spin it!

Adrian · 2002-11-11 14:34:34

Exactly! Using the spin cycle is merely an engineering problem, and in a single stroke you would overcome practically *all* the medical problems associated with long term space travel. Why not use centrifugal force?

Aetius · 2002-11-11 19:23:23

But what will the 'Life Sciences Priesthood' do? Isn't the study of biological adaptation to microgravity the primary focus of many NASA biomedical specialists? I smell some jobs being threatened. That's the only reason I can imagine why NASA has never committed itself to a serious demonstration of this technology in the Space Shuttle era. Even the centrifuge module planned for the ISS (Once Upon A Time) was only designed to examine small creatures, like TransLife. Then again, maybe there's some information I don't have that's relevant to this subject.

Go Spin Cycle, Go!

nebob2 · 2002-11-11 20:40:09

I think NASA was waiting for a space station before looking into a serious demonstration of artificial gravity in space, and that quest is taking a little longer then they suspected it would back in the shuttle era.

Spin it, but not before you lay on the coal. That would help solve the rest fo the medical hazards of interplanetary flight, like radiation. Flank speed straight to Mars!

AltToWar · 2002-11-12 22:59:01

What is the proper way to sleep in 0g?

With a friend of course!

dickbill · 2002-11-13 16:12:22

Hi all,

By tethered spacecraft you mean two modules linked by a long cable and rotating around the center of gravity ?
Why not just a cylinder module, in the spacecraft axis and rotating like in "mission to Mars" (I liked the movie for the pictures by the way, but not for the scenario).

This web site http://www.labcentrifuge.com/gforce5.html
gives a Relative Centrifugal force of 0.86g for a 12 meters (1200 cm, feet level) cylinder rotating at 8 tours par minute (rpm) and 0.72g at the head level if you are 2 meters tall. Whatever, 12 meters and 8 rpm don't seem excessive values, if the calculus is right.
Is that so difficult for a metallic structure of that size to hold the constrain ? Is that so bad for the spacecraft stability and ability to maneuver ? It seem so easy to create a gravity that way.
I guess Shuttle-C be would be able to lift a 12 meters diameter cylinder as long as the mass is not greater than 90 tons.

nebob2 · 2002-11-13 18:56:51

12m would be a rather bulbous payload for a shuttle derived HLLV. The external tank has a diameter of about 7.5m(?) I think, so 12m is a little less then twice this. The origonal Shuttle-C had an internal diameter of about 4.6m, so would be unable of fitting a 12m object inside.

Shaun Barrett · 2002-11-14 00:23:30

Hi Dickbill!

I enjoyed "Mission to Mars" too. The scenery was excellent and, unlike you, I quite liked the storyline, too. But then I'm a sucker for science fiction movies, despite all the little mistakes they tend to make!

The rotating cylinder they used for artificial gravity looked so neat and seemed to work so well, I can see why you find the idea attractive. If only it were that simple!
The trouble lies with the small radius of such a set-up. With a small radius, you need to spin the craft quickly in order to achieve the kind of g-forces we're looking for.
With high rates of spin, you encounter big problems with the Coriolis effect. It's this effect which makes it obvious to the occupants of such a spaceship that the 'gravity' they're experiencing isn't real ... the effect including strange sensations when you turn your head or bend over to pick something up, and the fact that when you drop something, it falls sideways as well as 'down'!

I dug up this article on google.
It's pretty old (1989), but the principle hasn't changed and it gives a fairly vivid description of what Coriolis effects at high rates of rotation must feel like ... not very pleasant!

The article ends by saying the worst of the Coriolis problem can be avoided by using a tether and making the radius of rotation much larger, thus reducing the required rate of rotation.
This is fine, but it goes on to say it will take another 10 years before we iron out the developmental problems of such a system for lengthy crewed missions. Well ... it's been 13 years since then ... and we haven't even started yet!!
:angry:

dickbill · 2002-11-14 13:50:47

I dug up this article on google.
It's pretty old (1989), but the principle hasn't changed and it gives a fairly vivid description of what Coriolis effects at high rates of rotation must feel like ... not very pleasant!
The article ends by saying the worst of the Coriolis problem can be avoided by using a tether and making the radius of rotation much larger, thus reducing the required rate of rotation.

http://www.graybiel.brandeis.edu/article2.htm

Interesting article. Indeed, rotating fast in a small diameter chamber is obviously not the best way to simulate gravity.
I have some comments however: the chamber in this article was too small: 22 feet, about 7 meters (I like the imperial system...) but I don't understand the calculation. The author said he is spinning in a 22 feet diameter chamber (11 feet radius, about 3.3 meters ) at 5 rpm to create a "combined force of about 1.45g", while I got a mere 0.09 g with the following formula:
RCF (relative centrifugal force to earth) = .00001118 x radius (in cm) x RPM2.

Of course, the author is spinning on Earth so we have to add vectorially 1 g but that still doesn't make 1.45 g. With the formula above, with a 330 cm chamber radius he would need to spin at 20 rpm to reach 1.45 g in space (no earth gravity added) which is consistant with what he said later in the article.
1) now 20 rpm is a lot, no wonder the author is sick !
2) there is no need to be at 1 g in space, maybe 0.5 g would be enough to counteract the effect of microgravity.
3) The control mice of the "translife" experiment, according to a report that a read (but a cannot find the link anymore) were fine in a table centrifuge of a 1 meter diameter. I am talking here about the control mice stayed on earth, specifically used to see the long term physiological effect of the coriolis forces, because in "translife" the artificial martian gravity is biased by that coriolis force, so we need to differentiate the effects of 0.38g from the effect of the coriolis generated. Anyway, in short, the mice were able to adapt to the coriolis, on earth.
3) a lot of the coriolis generated sickness is due to the vestibular apparatus. Maybe a possible approach would be to transiantly inactivate the vestiblar nerves.

4) at 12 meters diameter or 6 meters radius, only 8.6 rpm is required to generate 0.5g and only 3.86 rpm for a 30 meter radius structure. Now 12 meters is a big cylinder which doesn't fit in any shuttle. But what about a flexible structures that could be inflated in space ? I still prefer a cylindrical compact symetry in a robust space ship with a little bit of coriolis rather than a thetered rotating structure with no coriolis because....what happens if the cable breaks ?

AltToWar · 2002-11-15 03:17:49

At a 6' radius, your feet might stick to the ground but your head will be weightless.

I dont imagine your inner ear will like that too much.

Byron · 2002-11-15 06:11:12

I have a couple of questions to ask of those who favor spining the ship...

Assuming that Coriolis problem can be licked by using lengthy tethers (I'm still queasy -excuse the pun- about that idea...it'd be so easy to get that thing all tangled up), what do you think is the best level of gravity to use for the voyage out to Mars and back? Would it be a better idea to start off at a full 1 gee, and gradually slow it down to .38 gee over the course of the journey to Mars, or just start out at .38 gee and leave it at that for the duration of the voyage?

I think .38 gee would be imeasurably better than having no gravity at all, but would it be enough to maintain shipboard health for months at a time? After living in Martian gee for two or three years, I wonder how difficult it would be to suddenly adjust to Earth gravity...

If only they would use the ISS as a platform to carry out these types of experiments...there's just so much we don't know!...

B

Shaun Barrett · 2002-11-16 02:31:24

Hi Dickbill!

I agree with you about the mathematics of the article I linked to. There's been a major foul up somewhere - and I apologise for not checking the figures.
My main purpose was to indicate how uncomfortable fast rotation rates can be, but it never occurred to me that our correspondent (the author of the piece) might have slept through mathematics classes in highschool!

I agree that 3.35 metres radius and 5 rpm will give you no more than 0.093g. And no amount of vector analysis is going to give you 1.45g in any direction!

In order to get a vector acceleration of 1.45g at the floor near the wall (with 1g in the vertical of course), you'd need a lateral centripetal acceleration of 1.05g. This translates into a rotation rate of nearly 17rpm. And to stand up in that environment, you'd need to make an angle of about 44 degrees with the floor!!
None of these figures even remotely resembles the ones our author quoted, so I don't know where he went wrong with his numbers.
Sorry! ???

But nevertheless, Coriolis effects in space will be more troublesome the smaller we make the radius of rotation of our spacecraft or the more artificial gravity we want to produce. The unpleasantness reported in the article is accurate, even if the numbers aren't!

Hi Byron!

I couldn't agree more with your frustration that we're not doing much more in Low Earth Orbit to investigate the effects of long-term exposure to Coriolis effects and, especially, to 0.38g.

Your scenario of starting at 1g and reducing to 0.38g as the Hab nears Mars is the one I favour. And spinning up to 1g as soon as practicable on the way home is the way to go, in my opinion.
That way, the astronauts are kept in normal Earth gravity for the maximum time possible, which must be better for them in the long term.
My notion of the ideal situation is a cable 1.8 kilometres long joining the Hab and counterweight (i.e. a spin radius of 900 metres), and a rate of spin of 1 rpm. This should give a supremely comfortable impression of normal Earth gravity with virtually none of the unpleasant side effects of rotation.

I visualise low thrust ion engines being used to maintain tension on the cable as the Hab separates from the counterweight. These engines could be shut down only as the two masses are 'spun up' using other ion engines, and as the rotation itself becomes sufficient to keep the cable taut. Using this technique, I foresee no difficulties with the cable getting "all tangled up".
I've suggested ion engines because we know how to make them, they exert a gentle and continuous thrust perfect for spinning up and spinning down, and the mass of fuel required would be small.

As far as the cable itself is concerned, I really think worrying about it breaking is taking nervousness to unrealistic extremes. People enjoy rides at carnivals all the time and hardly give a thought to how many things could go wrong and possibly kill them. Some people even jump out of perfectly serviceable aircraft ... on purpose ( ) ... and plunge Earthwards, hoping that a carefully packed pile of material and string will pop out of a sack on their backs and prevent them encountering the ground at high velocity!! Haven't you ever stood on the 30th floor of a skyscraper, this time with just a glass wall between you and that high velocity encounter with the ground?! And didn't you ever wonder about the glass breaking? But how often does that happen?

Life's a risk. As they say: Living is a life-shortening experience!
There are so many risks involved in a crewed Mars mission. The chances of the cable breaking would be so far down my list of things-to-worry-about as to be completely trivial.

dickbill · 2002-11-16 13:01:12

Hi Shaun,

don't worry about the math, I get the point: coriolis is really unpleasant. But you, or other, didn't really comment on my comments that:

1) 1 or more g are not necessary, 0.5g or less could do the deal. Everybody seems to agree with that.

2) At 6 meters of radius, less than 9 rpm is needed to create 0.5 g. At 30 meters diameter, less than 4 rpm is needed to create 0.5g.
The question is: at what moment the coriolis force will be physiologically acceptable ? and can we help on that issue by transiently inactivating the vestibular nerves since more of the bad coriolis sensation comes from our inner ear and vestibular apparatus. Remember, the author of this article said " piece of cake that rotation chamber", until he decided to move his head and then he felt sick because of the pain in his ears.

3) a 30 meter radius rotating structure is big but still wouldn't require a tethering cable with a countermass. I remember Nasa's studies of big inflatable structures. A toric inflatable chamber of kevlar or other strong new materials, supported by a flexible metallic exosqueleton for rigidity might be feasible, once inflated, it could be embedded or covered by a thick coat of polymers to provide resistance to meteorit impact, radiation, insulation. In biology one often use such polymers, liquid a ambient temperature, solid at minus 20 centigrade or below. For example, if such a polymer constitutes one sheat of the coating , it would melt at the meteoritic impact and quickly resolidify because of the ambiant cold, thereby protecting the inner chamber of depressurization.

Shaun Barrett · 2002-11-17 00:54:44

Apologies Dickbill!

You're right, I think, that maybe a majority of people believe we can get away with less than 1g of artificial gravity. I think Dr. Zubrin tends to favour a small radius of rotation and only 0.38g (i.e. Martian equivalent gravity.) I can't recall the figures and can't be bothered doing the calculations right now, but I think he was talking about a metal truss structure with a diameter of 22 metres (no cable).
Your idea of a 30 metre diameter inflatable structure providing 0.5g at less than 4 rpm would probably work well. I've read a little about human tolerance for a rotating environment and we do, apparently, adapt fairly quickly to anything up to about 4 rpm.
And your ideas for the self-sealing material are very interesting, though I know little about materials science so I can't make any sensible comments as to its viability.

If we're looking at a Mars Direct scenario though, we have at least 180 days each way plus 500 days on Mars. Dr. Zubrin's design would mean the astronauts would effectively be in 0.38g for 860 days, or 2.35 years.
I don't have any idea (and I suspect nobody else does either) whether 0.38g is sufficient to prevent loss of bone-density. My guess is that it won't be.
But a 180lb male (I'm sticking to Imperial for the sake of my American cousins) would rapidly become used to weighing 68lbs. Every muscle in his body would adjust to this new situation by shrinking and losing tone. What's worse is the fact that every pint of his blood would weigh only 38% of its Earthly weight, so his heart will get used to much less work than it had to do back home, and weaken accordingly.
Despite rigorous exercise regimes, which are very difficult to maintain enthusiasm for (ask the Mir cosmonauts if you don't believe me), I have serious doubts about how well the astronauts will cope when they get back to Earth. I've expressed this fear before by asking other New Mars contributors to imagine suddenly weighing 2.63 times their normal weight. Let's go back to our 180lb male for a comparison. When he lands back on Terra Firma, he will think he weighs 473lbs!! That's how it will feel ... to every muscle in his body, including his heart.
I think that's going to mean big trouble.

Your 0.5g will probably help somewhat, but personally I don't believe it'll be enough. I emphasise I'm not a physiologist, but common sense tells me we're likely to have problems.

I think I'm probably in a minority of people who advocate providing a full 1g of artificial gravity for most of the year spent in transit. This is the ideal scenario which gives the crew the best possible chance of returning in good shape.
The research done so far on human adaptation to rotation suggests that up to 1 rpm, the Coriolis effects are very mild and adaptation times into it, and more importantly at Mars, out of it, are brief.
In order to achieve the best of all possibilities, 1g and 1 rpm, you need that 900 metre radius of rotation. And for that you need a cable and a counterweight. This is why I argue strongly for this option. It's the arrangement I'd prefer myself if I were making the trip.
Using a spent booster stage as the counterweight on the other end of the cable also has another incidental, but important, advantage ... radiation protection. If scientists anticipate a solar flare, the Hab and counterweight can be spun down and winched together with the booster stage between the Hab and the Sun for extra shielding. One of the booster stage bulkheads could even be beefed up a little with this protection role in mind.

Any thoughts?

nebob2 · 2002-11-17 01:46:44

I agree, the longer they are in 1g, the better. A cable will probably be able to be spun in and out easier then a truss, so long lengths are easy to accomidate.

I wonder, what are you going to use as a counterweight for the return trip? And how exactly were they planning on deploying a 22m truss. I havn't seen any mention in Zubrin's technicle papers.

I think an 180 day trip is streatching it, at least reduce it to 120 days, that does not require exotic propulsion systems as sub 100 day transits would. The less time in space the better for the crew.

Shaun Barrett · 2002-11-17 06:28:06

Good to have support for the 1g argument ... thanks nebob2!

I think the idea is to leave the spent booster stage in orbit around Mars while the expedition lands in the Hab.
500 days later, the Earth Return Vehicle leaves the surface and docks with the booster. They both leave Mars together and the counterweight performs the same function for the ERV on the way home as it did for the Hab on the outward leg.

If, as you say, it's feasible to reduce the transit time to 120 days, so much the better. But wouldn't that mean a trade off as far as allowable mass is concerned?
While we're on the subject, does anyone know roughly how long a transit would take using nuclear thermal engines?

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#19 2002-11-15 03:17:49

Re: Catching Some Z's - How to sleep in low to no gravity?

#20 2002-11-15 06:11:12

Re: Catching Some Z's - How to sleep in low to no gravity?

#21 2002-11-16 02:31:24

Re: Catching Some Z's - How to sleep in low to no gravity?

#22 2002-11-16 13:01:12

Re: Catching Some Z's - How to sleep in low to no gravity?

#23 2002-11-17 00:54:44

Re: Catching Some Z's - How to sleep in low to no gravity?

#24 2002-11-17 01:46:44

Re: Catching Some Z's - How to sleep in low to no gravity?

#25 2002-11-17 06:28:06

Re: Catching Some Z's - How to sleep in low to no gravity?

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