In this thread, I brought up the issue of your chances of surviving a long space journey (e.g. to Mars) without any short or long-term physical effects (leaving out the psychological). Given the Unwritten Rules at work in these boards (i.e. any topic drift=Bad), nobody followed up my comment in IMHO, but I thought it was a worthwhile point, so here it is.
The basic problem is shielding the human body from all sorts of nasty high-speed molecules /slash/ radiation which will be constantly bombarding the spacecraft in question, so that the astronauts in question don’t come down with any of a whole host of cancers and such, sooner or later. It would not appear that the Orion craft is up to the challenge; it would either require large amounts of lead, or a water tank (you’ll need water on your trip, natch) which almost completely surrounds the crew quarters. These remedies, assuming they actually do the job, may add too much weight to make them cost-effective.
So-can humans, with the current state-of-the-art technology, devise some sort of shielding scheme to avoid cosmic rays and their ilk so that they can withstand a trip which may last upwards of 3 years?
It seemed to me that the idea was rather to shield only a small part of the vessel, where the cosmonauts would seek refuge in case of a major solar flare (I’m not sure how solar flares would be predicted in a timely manner), while they would just be left exposed to radiations the rest of the time.
That was my understanding of how the issue was expected to be handled, but I might be very mistaken.
You have to take a butt load of fuel, oxygen, water, and equipment ANYWAY. If you use THAT for shielding, IMO you get adequate shielding. Not great, but enough in my WAG to survive the trip and with a little luck many years after before you get cancer.
Remember there are two kinds of radiation. Background and fairly constant which I am pretty sure you could shield adequately.
The other is from a solar flare. You get hit directly by a big one, and its gonna be a good bit worse. Probably not enough to kill you right away. But enough that you’d be sweating bullets for a few years wondering when the cancer is going to show up.
You chances of getting a direct hit by a big flare are probably no worse that getting killed when your rocket blows up or your air tank leaks or whatever.
The earth is shielded from highly energetic particles by the magnetosphere. It seems obvious to me that there should be a way to artificially generate a magnetosphere around the spacecraft to shield the occupants.
The worst damage from a solar flare isn’t from anything moving at the speed of light, but from slower (though still very fast) charged particles. So the simple answer is that you don’t need to predict them, you just see them coming.
Of course, since the Sun is the source of the dangerous particles, you also don’t need to surround the entire shelter: You just need a nice protective parasol you can hide behind.
[grammatical picking]I made some thread before complaining about people not differentiating between em- and en-dashes. I seem to recall being told it wasn’t that big a deal. I just spent 10 seconds trying to parse the title of this thread. Some of it probably has to do with my being tired. Carry on.[/gp]
Well, a proper Project Orion (the kind that uses atom bombs as fuel, not that that wimpy new chemical rocket design) should be quite build-able with current technology, and would be able to lift enough weight to allow adequate shielding for the crew, and as a plus the design requires a very thick steel pusher-plate, which can be kept pointed at the sun for most of the journery. Not to mention it would be much faster than a chemical rocket, reducing the amount of time astronauts are exposed to cosmic radiation.
Of course, dealing with the politcal & literal fallout of launching one of these would be a massive undertaking in and of itself.
You’d probably keep the ship oriented that way most of the time, anyway, just on general principles. When you’re not actually making a burn, there’s no compelling reason to orient any other particular way.
Actually, in the Apollo days leaving the ship in a fixed orientation was considered a bad idea because of differential heating - the side facing the sun would warm up, the opposite side would cool down. This was deemed undesirable, so they would put the spacecraft in a slow roll (I’m thinking one revolution per hour) to even out things. Formally, it was called Passive Thermal Control; informally, The Barbeque Mode.
Yes, but on a trip to Mars, you’re going to have the ass end of the ship facing Earth for most of the voyage, which is (roughly) where the sun will be. Putting a vehicle on a trip to Mars in something to transfer heat around would involve having the ship tumble ass over tea kettles, which would make it difficult to communicate with the Earth.
NASA, BTW, came up with a solution for the thermal differential that didn’t involve putting the ship into a roll, but chose not to adopt it for weight reasons.
[thread=444092]Possible Human Problems on the Mars voyage[/thread]
[thread=419387]complications of space travel[/thread]
[thread=406262]How fast could we get to Mars or Jupiter?[/thread]
[thread=379945]An off-the-shelf, manned mission to Mars?[/thread]
[thread=489401]We need to build a generation ship[/thread]
The short answer is, no, the current state of the art in manned space habitation and propulsion is insufficient to get a human crew to the surface of Mars and return with anything approaching acceptable risk. Spinning tales of lashed together equipment, ad hoc methodology, and a prayer is not a substitute for the very real and extensive development that would be required for such a venture. (Nor to anecdotes that attempt to portray the US and USSR Moon shot ventures as such patchwork efforts by a few selfless heroes do justices to the tens of thousands of engineers, scientists, pilots, technicians, et cetera who worked long hours to make gradual progresses at developing the methods and technology to make even the comparatively trivial effort to land on the Moon feasible.)
Radiation hazards, gravity simulation, high thrust propulsion systems capable of operating for years at a stretch without maintenance, reliable and efficient environmental recycling systems, et cetera are all major areas that need substantial development before such a mission would be feasible.
I’m still not seeing why they would have to keep the craft oriented nose-first since, as you’ve pointed out, orientation matters only when you’re doing an engine burn.
Com would not be a problem in an Ass-Over-Teakettle roll. Just mount the antenna on a mast perpendicular to the ship’s axis and spin the antenna at a rate that offsets the roll. I may be wrong, but I think Apollo’s steerable high-gain antenna was used in just this manner.
Anyway, I suspect all this is moot because a Martian mission would likely require the use of solar panels for power production, since such a mission already has considerable weight problems without also having to lug along enough hydrogen and oxygen to supply the fuel cells.
I’d forgotten about that possibility. Some of the experiments left on the moon were nuclear powered.
It opens a can of practical worms, too. Having a Service Module with fissable material on board is definitely a problem at the end of the mission when said module would presumably reenter the atmosphere. Avoiding that is a huge complication.
The only thing you want to bring back to earth are the astronauts, some CD’s with lots of pretty pictures, and rock/whatever samples.
You mars vehicle/transport habitat is either gonna stay in orbit to be reused, abandoned in HIGH orbit, or sent on its merry way to wander the solar system for a few million years.
Once you’ve got this out of the way, the biggest threat to humans is the leaching of calcium from the lower body due to zero-G, which, after about a year, would lead to bones that are incapable of supporting human weight in Mars gravity.
Not online cite: Perspective on the Impact of Weightlessness on Calcium and Bone Metabolism Bone, Volume 22, Issue 5, Pages 105S-111S