Zero G is fun. Zero G is bad for you. We figured that out a long time ago.
Spin the frackin spacecraft to create “artifical Gs” and just be done with the problem.
Grrrr.
Its one of the biggest problems with going to Mars,or just living in space long term and its the most EASILY solved. NASA’s been dicking around in low earth orbit for the better part of 40 years and a trillion dollars (or more?).
Yet they have done ZERO experiments on what fraction of a G humans need to be exposed to long term for the bone loss to stop.
Putting a spin on a spacecraft or space structure of sufficient size to provide simulated gravity. For one, the structure needs to be of a minimum diameter (roughly 10m) to avoid physiological effects of the Coriolis component of a moving body in a rotating reference frame. This means that you’d either have to have an assembled structure of greater than 10m and a launch vehicle capable of delivering said structure, or a structure that can be assembled once placed in orbit capable of accepting the loads and resultant stresses imparted by such rotation.
There is also the problem of balance; the mass of personnel and equipment moving in a lightweight structure will result in significant imbalance, which either requires a counterbalancing active ballasting system or a reaction control system that would continuously compensate for imbalances. Any system heavy enough that this would not be significant would be much heavier than could be boosted by any extent or (seriously) proposed launch system.
Then you have the issue of having to mate up to a rotating system. Either you need to have some kind of non-rotating hub with a sealed pin-1 joint, or any vessel that mates to it has to match rotation a la the Pan Am Space Clipper in 2001: A Space Odyssey (see above for why this would be a problem).
Of course, all of these issues are engineering problems, but they are excruciatingly difficult engineering problems, especially for a structure that has to function flawlessly for years. It’s easy to wave hands and say, “Make it spin,” but much more difficult to turn that into a functional reality. I agree that the methods and technology need to be developed to support long term human habitation or exploration, and that space exploration agencies have been remiss in not developing this capability, but it would add costs to existing space structures that would have been prohibitive compared to available budgets.
Compared to everything else that is hard, this part is easy IMO.
A few humans moving around in a many multiton craft aint that big a problem.
As for structural problem. Anything that is launched must survive 3 g’s give or take AND a bunch of nasty vibrations to boot.
One G or decent fraction with very little vibrations, would seem to be nearly trivial on comparison.
One heavy end with lots of crap. Another heavy end with more crap and people in it. A long cable(s). Start spinning. Whats the difficultly there? Whats to wear out?
Re: long-term life in space; haven’t several russian cosmonauts been in space for over 1 year? They were a bit woozy on return to earth, but seemed to survive OK.
I liked those coffin;like cabinets they had in “2001-A Space Oddysy”…although, i don’t want “HAL” being able to turn my air off!
This is what I mean by handwaving. As previously addressed, a structure large enough to be spun for simulated gravity would be larger than anything that could be carried by any existing or proposed launch vehicle, so it would have to be light enough to be carried, capable of being assembled in space and yet be capable of resisting not only the tensile loads from rotation but side, torsional, and vibration loads that would result during spin-up and spin-down and orbital escape/injection maneuvers. You would not, as you suggest, want to attach two masses at the end of a cable, either, or at least not without applying some kind of robust rotational damping; forced during spin-up and spin-down would cause the individual masses to oscillate. As I stated, it’s not an irresolvable problem, but it is a significant one and beyond currently developed and demonstrated spacecraft technologies.
Astronauts and cosmonauts who have remained in space for over six months return demonstrating calcium depletion, weakening of heart and skeletal muscle, et cetera. It is not known what the impact of long term habitation in low gravity (i.e. Mars surface) environments is. Given that our hypothetical Mars explorers would have to disembark and remain on the surface of Mars for over a year, this is a definite concern.
We don’t have anything like the long-term hibernation capability displayed in 2001, nor the ability to keep non-active people physically healthy and fit for months at a time. That simply isn’t an option at this point.
Of course, if we can figure out some sort of sustainable high-g engines, all of these problems are easily solved. A trip to Mars under 1g acceleration takes days, not months. So, if you want to go to Mars, work on engine technology or get a bunch of little nukes.
Of course it aint trivial. NOTHING in space flight IS.
But, compared to everything ELSE that has to be done to get into earth orbit, leave earth orbit, live in space for years, enter mars orbit, deorbit to mar’s surface, land on mars surface, live there for months, renter orbit, rendevous in orbit, leave mars orbit to return to earh, live for years in space again, reenter earth oribt, deorbit to land on the earths surface (damn that just made me tired thinking about it) I aint buying artifical G’s as the hardest part or even a deal breaker.
And more importantly, we now pretty much know, baring some medical breakthrough or massive propulsion breakthrough, we NEED to do it. And we have never tried. And as far as I can see, we still arent even planing on trying.
Sometimes I get the feeling that NASA doesnt even care about it, like they are going get everything designed and planned and funded, then at last minute a report will come out proving beyond all doubt that zero g for that long will absolutely kill everyone…oopps, nevermind, back the drawing board for another 40 years.
I’m all high on drugs for the latest bug going around. Maybe I can make my point clearer later.
That’s way harder than spinning for simulated gravity. Even an ORION-type vehicle isn’t going to offer continuous thrust; it’ll boost for a few hundred meter-seconds of impulse. Constant thrust 1G propulsion is purely in the range of science fiction at this point.
There are no firm conceptual plans for a manned interplanetary mission, and despite vague mandates no funding exists for developing the requisite technologies. Blaming NASA–which is and always has been largely a political hobbyhorse with varying expectations–misses the core problem with developing the capability for manned space exploration beyond Low Earth Orbit, to wit, the lack of a consistent, long term fiscal and political support.
But we don’t need 1 G thrust for a Mars mission, really. Martian gravity is 1/4 that of Earth’s, and anything over that, will enable astronauts to keep the muscle tone needed for them to be able to function on Mars. Presumably, this would at least slow the amount of bone loss suffered by astronauts on a mission, and while such engines do not presently exist, there are designs which could be tested in a relatively short period of time, were NASA given the necessary funding.
And sadly, it doesn’t look like there’s going to be a significant amount of change in this attitude under the Obama Administration. The “Agenda” section of the White House website makes no specific mention of NASA at all.
We have plenty of rockets that will boost at over 1 G. The problem is that if you’re planning on using a rocket, you’re going to have to carry more fuel than is physically possible. You canna change tha laws of physics, Captain. Adding more fuel just means you need more fuel to accelerate the added fuel.
We don’t need research into better rockets. We’d need technology that is equivalent to magic, in that while we can imagine anti-gravity and so on, we have absolutely no ideas on how to even begin doing the research. Maybe someday we’ll invent something like anti-gravity, but it won’t be done by spending a lot of money researching anti-gravity, it will be done through breakthroughs in theoretical physics.
We have virtually no experience with the effects of low, non-freefall gravity on the human body. We don’t know what the low threshold is for sustainable health. 1/4G might be suitable, or it may be that 1/2G is a minimum threshold.
No, there aren’t. Electric rocket systems (ion, charged plasma, magnetoplasmic, Hall effect, et cetera) provide low thrust and are notoriously inefficient. They are well suited for intermittent use as attitude control thrusters on long duration satellites and spacecraft due to requiring no moving parts, liquid propellants, and high reliability, but they are ill-suited for use for high thrust propulsion. The most feasible proposals for interplanetary propulsion I’ve seen to date are ORION-type nuclear pulse propulsion (which requires a minimum mass and complex pusher plate and damper system to absorb the impulse), nuclear electric powerplants (inefficient and heavy, but capable of providing constant low thrust to ion or charged plasma propulsion systems), and nuclear thermal rocket motors like the old NERVA concept or fissile liquid salts, which can provide moderate thrust for extended periods but operate in regimes near instability to achieve reasonable propulsive efficiency and suitable specific impulse.
The other problem with constant high thrust engines are material limits; the kind of thermal and erosive environments that go with high thrust engines exceed existing material capabilities. With a low thrust attitude motor you can accept a reduction in performance that goes along with degradation in exchange for long term reliability, especially if you have a number of redundant thrusters; the same cannot be said for a high thrust engine that is critical for vehicle propulsion. Even if a concerted effort were launched to improve the state of the art in spacecraft propulsion it would be several decades before we could reasonably expect to have a reliable, fieldable, long firing duration, high thrust rocket engine suitable for interplanetary flight. The only possible exception to this is ORION, which for other reasons is politically and logistically unlikely.
We’ll be making Hohmann-type transfers and swing-by maneuvers to go from planet to planet for a long time to come, and these are discordant with reliable human exploration beyond Earth’s sphere of influence. Short of efficient and compact nuclear fusion or some other nearly-science-fiction-conceit-cum-reality propulsion system, a manned mission to Mars or any other major celestial body beyond Earth’s Moon is highly risky and unreliable, and unlikely to offer much scientific benefit beyond what vastly cheaper unmanned probes have done.
IIRC, studies have shown that things like resistance exercise in a weightless environment provides some benefit in terms of things like preventing boneloss. I believe that there are some studies which have proposed using osteoporosis drugs in a weightless environment to see if those can prevent boneloss.
Which directly contradicts the Wiki article I linked to above.
And I’ll lay odds we’ll never see such engines used.
I’ve seen a few theories batted about on how those could be improved, but no concrete research has been done so far.
And the whole “nuclear” aspect of them takes the concepts off the table so long as we’ve got people scared of anything with the word “nuclear” in it.
Not necessarily. It depends upon a number of factors, most of which are impossible to predict due to the randomness of scientific breakthroughs and political will. It may not even take a material breakthrough, if an inexpensive and lightweight method of generating thrust can be developed. At that point, having multiple redundant engines which can cycle on and off becomes a practical method.
It all depends upon how much risk we as a nation are willing to put up with. For me, a manned mission to Mars with a 10% chance of success is more than enough for me to strap myself in for the ride.