Astronauts to Mars are preposterously expensive without ISRU-based propellant and radiation shielding.

The Russians have asked several times to increase to 9 months at least. I always thought it was about the numbers. At 6 months you have the statistic of having twice as many people up per year. 3 or 4 per year versus 1 or 2.

Should be at least two groups, shielded and unshielded. We need a control group to compare with so that we know it wasn’t microgravity, the stress of launch, etc. that caused any observed problems. With more groups we could compare different kinds of shielding.

I don’t have any special connections at NASA. Post in places where some NASA folks may be reading.

BTW, microgravity is another big problem. There are good reasons, of bad faith, that NASA hasn’t had any astronauts up on ISS for much more than six months. They should either shut up about about manned Mars missions altogether or get serious and put up astronauts on ISS for 500 days so that we all know what happens.

A cycler ship is a very large spaceship that cycles in an elliptical orbit that takes it around Mars and Earth without descending deep into their gravity wells. You would use a small, fast crew ship to rendez-vous with it whenever it passed close either Earth or Mars.

I believe the idea of using lots of propellant to use fast trajectories is sound, probably more feasible than using large amounts of shielding. It can also be easily combined with ISRU and SEP, which will reduce IMLEO by a lot. NTR would reduce it even further, but it doesn’t seem strictly necessary. I’m personally not all that eager to go to Mars or Mars orbit, it’s just that if NASA does do it I would want them to do it without an HLV.

Remember once at Mars, Mars itself shields half your GCR and there is plenty of regolith you could use for shielding your hab. On Phobos the situation is even better. If you stay on the Mars-facing side of Phobos you are shielded on both sides. If you put your hab at the bottom of the Stickney crater, you even get shielding from the sides of the crater. It works for micrometeoroids too.

So NASA should put a bunch of rats up in a shielded spacecraft in L1 for one month, then repeat the experiment with successively longer duration missions. Great idea. How do we make sure this idea goes to Bolden? If wouldn’t be very expensive. I can’t imagine you’d have to send up the shielding on separate launches.

That is certainly true, but GEO is a market that will look after itself, unlike LEO. Nothing much that NASA needs to do.

The astronauts and space tourists are a romantic distraction that keeps us from paying attention to real space commerce.

I believe space tourism may be the only thing that will enable large scale activity in space. It’s also something I’m really enthusiastic about. Like exploration, it’s something you do for its own sake. Whether those two things are worth taxpayers’ money is another question, probably not.

But what I’m getting at is this: why don’t we see commercial development of space? The two main hurdles are development costs for crew vehicles and habs and high launch costs. Thanks to NASA and Mr Bigelow the first hurdle is about to be removed. It’s the second one that’s the big obstacle. And since you’re advocating NASA shouldn’t go beyond LEO until there is substantial commercial activity in LEO that means that as long as we have high launch costs you would be opposed to exploration. Also, there’s not much NASA can do about launch costs, short of stimulating demand and letting private R&D solve the problem. But you’re opposed to that. Your positions sounds reasonable enough, but I wanted to check if you agreed that would be its logical conclusion: no exploration for a long, long time with launch costs being the bottleneck. Do you agree with that?

Not statistically significant. We need real studies, with very large numbers of lab rats, not with statistically insignificant numbers of astronauts.