I’ve been fiddling around with another spaceship model. This one is going to be an ocean liner of space, designed to proceed at constant boost (to provide a semblance of gravity for passenger comfort). Also, I don’t want to postulate both a space-drive and artificial gravity; I’d prefer to keep my improbabilities to a minimum
The problem is that, if I boost at 1G, the ship is too fast; I can make it to Mars in 3 or 4 days and Neptune in a couple weeks. Which means I don’t need a ballroom and a gymnasium and a lounge and all those other beloved ocean liner accoutrements, and who’d want to build a model without 'em?
So I can cut the boost. At 0.25G, Mars is 6 to 10 days away and Neptune about a month, and at least on the Neptune run, I need a ballroom and lounges and all those other lovely things to keep the passengers occupied on the long trip.
But now a question arises, and I put it to you guys. I know at zero g, your bones start to lose mass and you get vision problems and heaven knows what else. So what’s the minimum G I can use and still have my passengers arrive in reasonably good health?
We have extensive experience of human health at 1 g. And we’ve had people go for over a year in 0g, so we have a decent amount of experience with that, too. But for any g value in between, the longest data we have are from the Apollo astronauts on the Moon. That’s it, just a few days. So the short answer is, nobody knows.
In my opinion, figuring out the effects of long-term simulated gravity ought to be one of the top priorities for NASA. We already know that long-term zero G living causes some pretty severe health issues, and that only some can be improved with rigorous exercise routines. That’s tolerable when you start with astronauts in peak physical condition, and they return to Earth where they can recover with the best modern treatments. That’s not so good when the astronauts have to immediately perform physical tasks, like they’d face on any kind of Mars mission.
Unfortunately, none of the proposals to test centrifugal artificial gravity have gone anywhere.
A better question is, how are you going to stop the ship when it reaches the destination? 0.25G acceleration for weeks is going to lead to ridiculous speeds.
My conspiracy theory regarding NASA and low G is that they have some inkling that anything other than 1 G leads to total bone “decay” over a period of years…and once that got out…well people living on the moon and mars is pretty much a no go…and that would be bad…
Do we know enough to say that a 150 lb man feels about half the effects from gravity as a 300 lb man? Or is there more to it than this sort of simple calculation?
We have ample evidence that even at 1 g your bones will eventually “decay” - that’s what osteoporosis is, after all, it’s just that at 1 g is doesn’t get hazardous (usually) until a fairly advanced age.
Short answer, as noted, is that “we don’t really know”. On the other hand, with 3-4 days to Mars it probably doesn’t matter much and gravity will be more important for passenger comfort (less nausea, cocktails stay in the martini glass, etc.) than overall health because the health effects of even microgravity for that time period is pretty minimal.
The designs for those toroidal space stations proposed by Werner von Braun for the US Space Program in the fifties (although they had been conceived of by others much earlier) were never intended to rotate fast enough to produce 1 g, a detail they n ever really told us about in those popularizations. (Although the Space Wheel and the Discovery centrifuge apparently produced 1 g in the film 2001, they were too small and/or rotating too slowly to actually deliver this. It’s one of those sneaky secrets of space engineering)
the conceptual Stanford Torus, proposed at 1.8 km in diameter, would have rotated at a stately one rotation per minute, which gives 1 g of artificial gravity at an angular rate thought to be imperceptible. For obvious reasons, no one has built one yet.
Coming up with a design to give an acceptable level of gravity without being too big (the Stanford Torus would require a million tons of material) or without unacceptably fast rotation rates (they’re still debating what this is) is the big problem of tradeoffs.
Anything smaller would either have to rotate at an angular rate that would make Coriolis forces noticeable, or would rotate too slowly to give you a gee.
Based on the OP’s description of his ship, it seems to have the ability to accelerate indefinitely (magic fuel?). If that’s the case, go ahead and run at 1 G, just turn the ship around 180 degrees for a while when you want to slow down. You’ll still be getting 1 G all the way.
Right, it’s not a question of fearing the answer, it’s that they already know the engineering/cost considerations make “build it just to find out what happens” a No Go at the appropriations committee. Hard enough to keep a manned program flying as it is, they’re not going to pop for a reduced-G environment experiment for its own sake.
Mind you, they could do a long term exposure to 0.17G research, w/o building spinning stations, by building a long duration Moon Base. But again: Apollo scale budget, the committee is gonna want more bang for those bucks.
That may be the most important manned space flight question we need to know…
There will be no Mars exploration/colonization program if a few years in zero G and another one or two at Mars gravity level’s results in human blobs that can never return to Earth.
The International Space Station is a zero-G science laboratory. You can’t do zero-G experiments on a rotating space station. Rotating a part of a station is difficult to do safely.
But we have known for about 30 to 40 years now that long term zero G is BAD for you. At some point you kinda need to figure out what level isn’t so much.
