Long duration Human space missions - Can we survive them?

comstar03 · 2004-10-02 22:27:32

Tethered space vessels , look primative and not in the best interests in long term space development. Development of artifical gravity mechanisms on space vessels are the issue. We need to build this for long term exploration and colonization, starting with mars.

Commodore · 2004-10-03 18:08:16

So if we were to build a pair of ridgid wheels, and attach 6-8 modules to the outside, and spin it at whatever speed we deem appropreate for the mission, how big would the whole thing have to be so people wouldn't fall on there heads.

Grypd · 2004-10-03 19:07:53

To make a wheel or similar sized device, a certain size is needed so that the required apparent gravity can be created without there being too much rotations which cause other problems. It has been assertained that having a speed of four rotations a minute is the maximum perferable for humans as this what the majority of people can stand. This means that for a vessel to have an apparent gravity of about 1g then it reguires to be about 40 metres in diameter.

Frankly 40 metres is a bit on the small side and if we would want to go the way of making artificial gravity using centrifugal forces we should use a much slower rotation and as such a larger diameter in the wheel. It also allows a better comfort zone where an astronaut will not feel as if his legs are going faster than his head and that the difference in speeds causes dizzyness. And for reference we do not need to use a wheel shape a nice H shape would do just as good and probably easier to put into space in the first place.

BWhite · 2004-10-03 19:17:33

Tethered space vessels , look primative and not in the best interests in long term space development.

Why? Other than you say so?

Development of artifical gravity mechanisms on space vessels are the issue. We need to build this for long term exploration and colonization, starting with mars.

Coriolis effects rule out spinning vessels on a short radius.

The idea of putting habs on a wheel will need a really big wheel to avoid Coriolis and even tidal forces. Hence, a BattleStar Galactica.

Centrifuge chairs might solve certain physiological effects but the kinesthetic skills of the astronauts will be shot all to hell transitioning between 3/8ths gee or 1 gee and zero gee.

Commodore · 2004-10-03 21:02:37

To make a wheel or similar sized device, a certain size is needed so that the required apparent gravity can be created without there being too much rotations which cause other problems. It has been assertained that having a speed of four rotations a minute is the maximum perferable for humans as this what the majority of people can stand. This means that for a vessel to have an apparent gravity of about 1g then it reguires to be about 40 metres in diameter.
Frankly 40 metres is a bit on the small side and if we would want to go the way of making artificial gravity using centrifugal forces we should use a much slower rotation and as such a larger diameter in the wheel. It also allows a better comfort zone where an astronaut will not feel as if his legs are going faster than his head and that the difference in speeds causes dizzyness. And for reference we do not need to use a wheel shape a nice H shape would do just as good and probably easier to put into space in the first place.

40m isn't all that bad for a full g. A compromise could even be made somewhere along the line. In theory 3/4s g's, or 4/5s g's would go a long way to limit the damage of long duration zero g exposure, and not give anyone an upset stomach.

My consern for a huge complex is the cost of launching all the truss segements required, and that providing even trust for whole complex would require a lot of individual thrusters, lest we stress to many many differnt pieces during repeated burns. If were going to spend all this money on an interplanetary vessal, we'd surely want to get many trips out of it.

Martian Republic · 2004-10-03 21:38:01

To make a wheel or similar sized device, a certain size is needed so that the required apparent gravity can be created without there being too much rotations which cause other problems. It has been assertained that having a speed of four rotations a minute is the maximum perferable for humans as this what the majority of people can stand. This means that for a vessel to have an apparent gravity of about 1g then it reguires to be about 40 metres in diameter.
Frankly 40 metres is a bit on the small side and if we would want to go the way of making artificial gravity using centrifugal forces we should use a much slower rotation and as such a larger diameter in the wheel. It also allows a better comfort zone where an astronaut will not feel as if his legs are going faster than his head and that the difference in speeds causes dizzyness. And for reference we do not need to use a wheel shape a nice H shape would do just as good and probably easier to put into space in the first place.

One possibly way to construct it might be to use carbon fiber, rope, polymers and poxes to construct the ship. That way we could make it big enough and have it all one piece without having to send up individual modules to construct it. That way it will be several times stronger and be less likely break at stress points.

Larry,

comstar03 · 2004-10-03 22:26:04

BWhite,

I don't think we need to go to another planet until we can provide a lower risk of injury to the human system. If that means development of larger vessels with some sort of artifical gravity then wait.

It will take us time to assemble the earth orbit facilities and lunar facilities for continued expansion for humanity into space. Test new technology for all the different planets and moons within our solar system.

If we try to expand into space like a " wagon train through indian country " then we will work sometimes and fail others without any way to rescue or have some backup plan.

Tethered spacecrafts will have strain and temperature variations on the cable for long periods that could break, and the random action will cause the space vessels to lost position without ability to be retrieved, Thus the risk is unacceptable.

Grypd · 2004-10-04 09:05:31

The problem is long term exposure to zero gravity and does this mean that regular exposure to normal gravity or increased gravity ward of these health problems. And we have yet to experiment at what level of gravity is needed does it have to be 1G or can it be less.

So does a Mars vessel need to be as big as a hundred metres in diameter maybe not. As zubrin points out we can use tethers to create the same effect as a vessel much larger. In the future we will probably have cyclers based on the wheel shapes with inflated habitats to provide accomodation

GCNRevenger · 2004-10-04 11:57:53

I don't think we need to go to another planet until we can provide a lower risk of injury to the human system. If that means development of larger vessels with some sort of artifical gravity then wait.
Tethered spacecrafts will have strain and temperature variations on the cable for long periods that could break, and the random action will cause the space vessels to lost position without ability to be retrieved, Thus the risk is unacceptable.

Okay, then we are green light for Mars in that case... five or six months of zero-G should not be a problem if you give the crew a little time to acclimate when they get there, ISS crews stay up that long and are able to walk okay if they have kept to a physical routine. Advanced drugs, vibration tables, and carefully controlled diets should be allright. A longer flight in the event of an abort might be a little problematic, but that is a risk the astronauts have to take... Speaking of risks, there is a point where you just have to say that the risk is okay backup or not. There is no way an early Mars mission can have a backup for everything without breaking the bank I don't think.

As far as the tether being at risk of failure, I don't think that is a problem. We can predict with good certainty how long a polymer can resist a strain at a certain temperature before breaking, and exsisting polymers are strong enough to do the job. Spray them with Aluminum to protect the cable from UV radiation, test it with a particle accelerator here on Earth to model solar wind, make the thing a mesh rope with redundant strands, etc. As far as what would happen if the cable did suddenly break, there wouldn't be any spinning out of control, just a little tiny amount of extra linear motion. The risk is very well acceptable, it just won't come cheap.

RobS · 2004-10-04 12:14:15

Regarding whether we have to have 1 gee or somewhat less, I think it is safe to assume "somewhat less" is fine. I was overweight two years ago and have lost 15% of my body mass since (235 to 205 pounds). So my skeleton is now experiencing 0.85 gees relative to what it experienced two years ago. I could easily lose another 15% of my mass, too, and still not be drastically underweight.

The fact that an adult of normal height can weigh 140 pounds or 300 pounds suggests to me that we can handle a range of gee levels as well. If we are living at 0.4 gees, fifty kilograms of weights slipped into pockets in our clothing (preferably of radiation-absorbing material) would help our bodies experience close to normal vertical stresses anyway.

-- RobS

C M Edwards · 2004-10-04 14:57:10

you can't control the motion if you are of similar mass and have nothing to hold onto... [...] if only one vehicle thrusts, then the other vehicle will still be pointing the original direction, so there is going to be a big tug at an angle instead of directly again the cable [...]

That sideways tug you refer to is angular acceleration. It will be there no matter how many sets of thrusters you use.

Yes, the tether will form a catenary under acceleration, creating potential energy in the tether that will recoil or "whip" as pendular oscillations in the spinning tether after the engines shut down. However, I don't think that's as dangerous as you imply. We wouldn't need vast amounts of thrust relative to the mass of the system, which wouldn't create much of a restoring force to recoil with. (An ant can push a tricycle in space, but it can't always crack a bullwhip.)

A spinning system can be controlled with only one set of thrusters. Because of the low levels of thrust required, microgravity might be a better place to conduct the experiment than full gravity.

Unfortunately, in spite of any minor details of the rocketry, your point about the potential returns is correct. Even if the additional cost were only < $10 milllion, much less > $50 million, I don't see how the few days that would buy us would yield any useful data. The test would have to be full scale. That means no combination of Soyuz or Progress modules is adequate.

Darn!

:bars2:

Euler · 2004-10-04 16:44:47

Unfortunately, in spite of any minor details of the rocketry, your point about the potential returns is correct. Even if the additional cost were only < $10 milllion, much less > $50 million, I don't see how the few days that would buy us would yield any useful data. The test would have to be full scale. That means no combination of Soyuz or Progress modules is adequate.

Even if it were just for a few days, that might be enough to give us some idea of how easily humans can adapt to Coriolis forces, and that would help us figure out how large the radius needs to be.

GCNRevenger · 2004-10-04 16:53:42

In a Soyuz? You can't even really stand up in a Soyuz with artifical gravity along its major axis, not much use for how humans operate (like walking) under artifical gravity. We're already talking like $50-60M of rocket, more like >$100M in the likly event you have to send up a purpose-built Progress as the counterweight/winch and the requisit structural & fluid modifications aren't factored in either.

comstar03 · 2004-10-04 17:18:36

Here we go again, development of " shoestring technology " for space advancement. We need technology that will last for endurance. In order to explore Mars over the next 50+ years we will require a larger personnel commitment on the surface that would require a larger vessel design and development.

We need the public to change their mindset around the uses of space and the role of humanity in space. shoestring technologies and wagon style rides to mars are not going to help change public perception. The ISS is turning into a lemon, and we don't want the mars missions to be preceived as lemons as well.

We need to develop permanent technology for artificial gravity and communication problems and other issues relating to long duration missions and voyages in space. We need to stage move of the humanity into space through space stations, lunar bases, mars bases, explorer vessels, then we can change the preceptions, creating an industry and living environment outside earth for humanity.

comstar03 · 2004-10-04 17:27:58

Secondly, tethered to moving objects, spinning vertical axis and moving horizontal with change weight in fuel, supplies and personnel movements within the vessels, thus the centre of gravity would continously change thus needs real-time adjustments, would require energy expelled. Therefore the device in the middle would be required to monitor strain factors, centre of gravity factors and have the control to correct them in real-time without effecting the course of the vehicles or the gravity within the vehicles.

Again to much risk, to much energy expelled, and the continous corrections for systems, the development of this shoestring technology isn't worth the time unless it helps to development of permanent vessel gravity technologies.

Ian Flint · 2004-10-04 17:44:05

the development of this shoestring technology isn't worth the time unless it helps to development of permanent vessel gravity technologies.

I'd have to say that without shoestring technology you wouldn't get permanent technologies.

Big non-shoestring projects like Apollo, the Space Shuttle, and the ISS have done some good things but shoestring projects like Space Ship One are what will move us forward faster.

comstar03 · 2004-10-04 19:15:09

Ian Flint,

SpaceshipOne isn't shoestring technology, it was systematic, tested and proven technology, what I mean shoestring technology is unproven technology with limited scope of use and alot of risks associated with the technology and not thought through.

Martian Republic · 2004-10-04 20:18:03

Ian Flint,
SpaceshipOne isn't shoestring technology, it was systematic, tested and proven technology, what I mean shoestring technology is unproven technology with limited scope of use and alot of risks associated with the technology and not thought through.

SpaceshipOne was basically a remake of the X-15, but with new technology. So the basic design had already been tested, but it had the benefit of new technology.

Larry,

SpaceNut · 2004-10-04 20:48:38

So if I have gotten the concept of rotational forces correct, if the mass of the rotating vehicle is small in comparison to changes of possible mass movement it would need almost constant mass movement to offset the imbalancing effect of crew movement. So the larger the central mass is the less the effect that there is on the outer ends of the rotating craft.

BWhite · 2004-10-04 21:12:58

Ian Flint,
SpaceshipOne isn't shoestring technology, it was systematic, tested and proven technology, what I mean shoestring technology is unproven technology with limited scope of use and alot of risks associated with the technology and not thought through.

So you say take Mars off the table until we can build Battlestar Galactica, correct?

= = =

PS - - suppose some wingnuts decided to go to Mars with tethers, and somehow survived.

By the time you build the first BattleStar Galactica, all the prime real estate will have been snarfed up. . .

GCNRevenger · 2004-10-04 22:24:24

For the first missions to Mars, Battlestar Galactica is almost certainly a non-starter. The sheer cost of building it and the gargantuan fuel load needed for a several hundred ton ship rules out building a reasonably small vehicle. Congress won't stand for such an expenditure when we could start missions to Mars far sooner for a portion of the price tag... Thats the way it is Comstar, there isn't going to be a massive "colonization class" ship for the first decade or so, smaller expendable vehicles are so much less involved and less expensive that it would be the doom of NASA not to use them...

And frankly, I don't think there is any hope of captivating the population of any country to invest the staggering sum needed to really earnestly build colonization-class hardware (real spaceplane, next-gen propulsion, giant interplanetary cycler, reuseable MAV, giant Martian fuel factory, etc) that would take decades and hundreds of billions of dollars. What you can talk them into doing is exploring Mars with Saturn-V derivitive or NOVA class rockets while technology and economy catch up to make colonization more affordable.

Either build a very large clean-sheet rocket and go direct or in two Shuttle-C shots per payload + CEV for crew from LEO with a upgraded NASA DRM style mission or small-scale cycler, maybe add Timberwind (better Isp but only one shot) or NERVA NTR (lower Isp but restartable) engines and we could go bigger, but we are a long way from any kind of colonization stuff.

As far as the dynamics of the teather are concerned, the ship(s) will only be spun up after TMI/TEI/orbital capture so there won't be any fuel "sloshing," and with how little people weigh versus the weight of the ship, the center of mass of the ship will be pretty constant. Its not an issue.

Ad Astra · 2004-10-04 22:48:47

Rob, you make an interesting analogy. But can it compare to instantaneously losing and regaining mass, like what the astronauts would feel when leaving earth or landing on Mars? I tend to think that the shock would play a factor.

Also bear in mind that extended periods of weightlessness cause all sorts of nasty side effects like bone decalcification and weakening of the immune system. I have faith that our pharmaceutical industry can step up to the challenge of mitigating these problems, but it will take plenty of research.

comstar03 · 2004-10-05 03:44:21

BWhite,

Could I have your budget, and resources to have a Battlestar Galactica style vessel, I didn't say anything about the size, however we need to build a more soundly built vehicle to transport humans across space to mars. I just commented on a human-centric vessel and unmanned cargo vessels. The human-centric vessel requires an artificial gravity system to help manage human physcology and convey humans to mars in a fit condition to work and develop Mars in the long term.

I think you are missing the movement to mars, its not " look can we do ", but a serious evolution of humanity into a permanent spacefaring race.

Also , with the reference to Battlestar Galactica do you think so conflict will happen in space like on earth between countries or industry ? That warrants an armed vessel in space, then you can use rail-cannon technologies already developed for protection.

If you have that as a thought then the first one there, should bring along four mobile platform rail-cannons and land them on the martian moons and use them as weapon platforms against the next land grabber, If ou think that way, BWhite.

How crazy that is , BWhite, but guarantee some people in all countries and some powerful individuals have those thoughts to extend their nations or tribes into space.

comstar03 · 2004-10-05 03:58:43

GCNRevenger,

I think you have some miss conceptions about the cost in development on larger scale space vessels. We need to work in stages first earth orbit needs cleaning up, next earth-moon needs progress that the public sees as substainable, all this time we have refined technologies, information systems, propulsion systems, environment systems, tested radiation shielding and more, at the same time expand to the moon and mining and manufacturing facilities on the moon. This leading the public into confidence about going into space permanent with exploring and colonizing other bodies within our solar system.

Watch any organization that moves change for hundreds of millions of people, and you will understand that you need them to think that its a good idea to move forward, even if you where going to do that, because the people feel part of the process, not alien of the process.

The movement of humanity into space is billions, not millions and it will cost trillions but don't talk about cost just benefits and the expansion of the human spirit of discover into the final frontier.

GCNRevenger · 2004-10-05 19:05:37

Ummmm not really, no. I think that building a huge ship weighing hundreds or even a thousand tonnes or more would be extremely expensive such that NASA could not afford to build it in a reasonable time frame given its limited budget, even with a small to modest HLLV. The simple fact that it would require extensive orbital assembly and hundreds of tonnes of fuel for every mission would be the doom of any "Battlestar Galactica" ship even 15-20+ years from now.

Heck, we're about 15 years away from even doing "sustainable" Lunar work with small vehicles to set up a small perminant base... there isn't going to be any Lunar manufacturing until the latter days of our lifetimes, and there might as well not be any serious Lunar water mining either (100's to 1000+ tonnes/year to Lunar orbit).

The public is also going to balk when drawings for the giant mega Mars star cruise liner hit the major networks, and it just isn't going to be practical to build without massive orbital infrastructure, which isn't happening... and people aren't going to "it will cost trillions but don't talk about cost just benefits" when its costing them.

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#51 2004-10-02 22:27:32

Re: Long duration Human space missions - Can we survive them?

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Re: Long duration Human space missions - Can we survive them?

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Re: Long duration Human space missions - Can we survive them?

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