The Grim and Gory Reality of Surgery in Space
bbc.com
bbc.com
An orbital station would likely be similar, with a rotating section and a stationary section, for ease of docking and to reduce the dangers of space walks (we don't want astronauts flying out the airlock at 1 g acceleration). I believe this was the flaw in the orbital station in 2001: A Space Odyssey.
The criticism of centripetal force as a substitute for planetary gravity is that it has directional vectors of force that would make you dizzy every time you turn your head. Presumably, the larger the structure, the more subtle these forces become. Perhaps humans can get used to these lateral forces over time, if indeed it is an issue at all. Having the simulated gravity would be very useful, especially in medical situations but also simply for the purposes of maintaining bone density and muscular health, both of which suffer enormously in zero-G conditions over long stretches.
I wonder if astronauts would develop "land sickness" that affects some people coming from cruises - constant dizziness when out of spin gravity.
Even if the zero-g journey to Mars is uneventful, astronauts will be severely weakened by the time they arrive there, even with heavy exercise and preventative measures. And in the first few weeks they actually do the most and heaviest work.
So there's a little mystery why NASA insists on trying to find a pharmacological or mechanical workaround when artificial gravity is right there.
[EDIT]
Here you go. The relevant info is on wikipedia: https://en.wikipedia.org/wiki/Artificial_gravity#Rotation
The radius of rotation would have to be a minumum of 224 meters.
Now this is a pretty huge space craft, but compare that with the ISS which is already 108 meters wide by 73 meters long. It's a huge undertaking but in the realm of possible. Of course, there's still the issue with mass and thrust required to propel a huge craft to an interplanetary trajectory.
The question is whether artificial gravity is a requirement for interplanetary human expeditions.
If you want 0.3g at 6RPM, it means a radius of 30m.
I can see why this might be a bit of a challenge, the time and costs involved would be enormous.
You'd probably want all that stuff reeled in together for acceleration and deceleration, but you can unspool the whole thing while you're coasting in between.
I sincerely doubt it's that easy.
Thrust against the direction of travel, but angle the thrust appropriately to maintain tension on the cable or whatever?
I mean, this part sounds like it's a low-level college physics problem.
All of that requires reaction mass and energy (or chemical rockets).
On top of that you can't do work on the outside of the space ship since everything (including the space walker) would fly away. You need a double tether at least for safety, etc. Storing the propellants for the thrusters will be an issue: solid boosters won't do because they can't be stopped. Storing oxygen/hydrogen over long periods is an issue in itself.
It _is_ a low level physics problem, but the practical implications are massive.
Yes, obviously. (Unless that microwave drive from earlier this year turns out to be really for reals).
> For every course change of the spinning construct you'd need to stop the rotation, reel in the drum...
I'm not convinced that this is entirely true. Doing so would simplify the math required to perform the course alteration, but I expect that altering the course of the craft while it is spinning is not impossible.
Regardless, as pavel_lishin mentioned in the first comment you replied to in this subthread, you can reel the tether in when making craft course changes.
> On top of that you can't do work on the outside of the space ship since everything (including the space walker) would fly away.
Unless -as you go on to say- you're attached to the outside of the craft.
> Storing oxygen/hydrogen over long periods is an issue in itself.
...if you're going to take a long journey in space, this is one of the problems you're gonna have to have solved, no?
So, I'm a little confused.
We go from:
> so how do we stop the rotation while reeling in for acceleration? Shortening the tether would accelerate the objects at the end...
to:
> Thrusters require energy and reaction mass (or chemical propellants). ... It _is_ a low level physics problem, but the practical implications are massive.
You're moving the goalposts. Your first question asked "How do we maintain the speed (and -thus- the g-forces in the craft) while altering the length of the tether?". Your follow-on comments to the answer to your question say -in a nutshell- "Gosh, solving that problem would make maneuvering too hard, and is thus kinda impractical.". :/
Or two counter-rotating tethers that can be braked against each other; the Arenauts could move to a non-rotating part of the ship for the procedure.
Admittedly, this is going to take energy to climb "up", but I'm assuming energy_to_climb << energy_to_alter_rotation.
Reliable reeling mechanisms that actually work in vacuum seem a yet unsolved problem, and there's occasional research into it. Sure, there could be more, but it's not like the lack of gravity is the only (medical) problem to solve for a Mars flight.
Parent commenter presents this idea occasionally without justification. At present stage of research, as you correctly point out, tethering in space is further out than biomedical research.
One question NASA has yet to answer is the minimal level of gravity necessary to prevent muscle and bone degradation. Is the Moon or Mars human-habitable in terms of gravity? If that's not the case, then mission plans would have to include rotating habitats for planetary surfaces, which makes matters a little more complex.
Research papers that prove NASA are doing their job.
The other simpler way requires expensive in orbit construction to do anything in the way of research.
I don't want to give away any spoilers here but the authors describe a huge ship designed for long-term deep space travel/living with the capability to "spin up the drum". The drum is a ~2km long tube that generates spin gravity when engaged, inside which the ship crew can live and farm.
There are also frequent but subtle mentions of the effects of spin gravity. For example, the apartments closer to the center of stations are cheaper due to the higher spin forces.
I am just starting the fourth book but the first three have been great. Quick, light reading but still a full-fledged space opera that is thought provoking and engaging.
The objective reality of our world and this (Eurasian part of) its species is that we have already reached the sorry apex of our "space travel": in other words it's not getting any better or more involved or complicated, or indeed gory and dangerous than it is now. EVAR. This is it: humans (9 times out of 10, air force personnel - not scientists, not engineers) spinning safely albeit wildly, around this planet at an altitude of 350-400 kilometers in a bunch of excruciatingly expensive modules ("ISS") with artificially created 0 gravity (actual low Earth orbit gravity at that altitude is about 96-97 percent of what it is right where I, and you, sit now).
.... and if anything goes wrong, the Ruskies ship them down to Earth ASAP to get operated on, or whatever. That's all.
So - what was that thing about "surgery in space"? Where? When? What species might have to do it? Not _us_ - I assure you, BBC, you poor Buzzfeed competitor, you.
And those people up there "in space" are, as of Nov. 30 and the latest news, being sent "caviar, fruit, and chocolate" - but no vodka?
http://tass.ru/en/science/840306
Eh???
I wouldn't wanna be on that "space station" when the Russian segment finds out about this conspicuous and inexplicable lack of the core "good times" component.
However, his other point has a lot of validity. Sending people into space and keeping them there is extremely expensive. Absent any major cost breakthroughs, I agree with his assessment of 'the sorry apex of our "space travel"'. Where will the money come from?