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Confronting the Credibility Gap for Crewed Exploration of Mars

caseyexaustralia.blogspot.com

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Re: Confronting the Credibility Gap for Crewed Exploration of Mars

#81

Post by jcoffland »

nine_k wrote: post #74
chandmer wrote: post #63

Earlier quoted context omitted.

No access to generic raw materials and huge lifting gas overhead, even huger delta-V requirements to do anything. I don't get Venus cloud tops. I've never seen anyone explain how to transport, fuel and launch a Saturn V rocket from a zeppelin.

The access to solids is definitely a problem. One approach might be digging them from the surface and lifting up using balloons. High temperatures don't help, but without the need to stay on the surface for very long periods, the digging robots may probably accumulate enough cold while high in the atmosphere, and then dive down for a short while, managing the temperature e.g. by melting and boiling the coolant, then…

Don't forget the extreme pressures on the surface which have crushed every probe we've sent there.

Re: Confronting the Credibility Gap for Crewed Exploration of Mars

#82

Post by jcoffland »

coldtea wrote: post #42
jcoffland wrote: post #39

Radiation is a huge problem. Both en route and on Mars. A lot of these problems beg the question. Is Mars really the best target? Sure it's close but there are moons around Saturn that are interesting as well. Titan for example. Sure it's cold but it has a lot of atmosphere. Presumably landing would be easier. If we could learn to live underwater we could possibly visit Ganymede or Europa.

> A lot of these problems beg the question. Is Mars really the best target? Sure it's close but there are moons around Saturn that are interesting as well. You seem to imply that the issue of radiation should cause us to reconsider whether Mars is worth it. But the same, and worse, problem people will have with Saturn too.

No, I mean all the problems taken together.

Re: Confronting the Credibility Gap for Crewed Exploration of Mars

#83

Post by jcoffland »

dTal wrote: post #76
jcoffland wrote: post #37

Earlier quoted context omitted.

How about we harpoon Mars and pull down one end of a space elevator?

Interesting proposal. You still need a lot of delta vee to get a harpoon+cable from orbit to the surface. You can't just fire it straight down, you have to cancel most of your orbital velocity (which would have to be way out at geostationary). Dunno what the strength requirements of the cable would be either, but I imagine the answer is "not small". Doing the same trick to Earth probably wouldn't be that much harder…

You don't need to get the entire mass of the elevator down initially. Just the harpoon and cable.

Many of the ideas for visiting other planets could and should be tested on earth first. I think we need to get comfortable with visiting the moon and performing large scale industrial projects in space before we have any chance of visiting remote planetary bodies and returning.

Re: Confronting the Credibility Gap for Crewed Exploration of Mars

#84

Post by restalis »

jcoffland wrote: post #39

Radiation is a huge problem. Both en route and on Mars. A lot of these problems beg the question. Is Mars really the best target? Sure it's close but there are moons around Saturn that are interesting as well. Titan for example. Sure it's cold but it has a lot of atmosphere. Presumably landing would be easier. If we could learn to live underwater we could possibly visit Ganymede or Europa.

"Is Mars really the best target? Sure it's close but there are moons around Saturn that are interesting as well. Titan for example."

First, for what is worth, I share your Mars questioning. But then I can't just let you downplay the distance factor with "sure it's close" glossing-over. One can find interesting tools out there¹ that may help grasping the astronomical distances better. The bottom line is that it just makes more sense to take our chances with planets closer to us and so far, at least with the landing on Moon, the humans respected in this regard their species' "rational" self designation.

¹ http://joshworth.com/dev/pixelspace/pixelspace_solarsystem.h...

Re: Confronting the Credibility Gap for Crewed Exploration of Mars

#85

Post by semi-extrinsic »

namlem wrote: post #80
semi-extrinsic wrote: post #45

Earlier quoted context omitted.

How are they going to come back? All realistic plans I've seen are for one-way trips. The thought of dying isn't the inherently problematic part, but rather the extreme isolation. People who go to war are there for only some months and have plans for going home, back to friends and family. People who dive and explore the oceans are isolated for a few days at worst; perhaps months in a nuclear sub, but there you have…

What are you talking about? Both NASA's and Musk's plans involve return trips.

Wow, that is so hard I didn't think it was being seriously considered. They're going to send a Mars surface-to-orbit launcher as payload in one piece, without fuel, and then produce >30 tons of rocket fuel on Mars? My hat's off to them.

Re: Confronting the Credibility Gap for Crewed Exploration of Mars

#86

Post by Crespyl »

nonbel wrote: post #72
XorNot wrote: post #20

Earlier quoted context omitted.

The Relativity of Wrong [ http://chem.tufts.edu/answersinscience/relativityofwrong.htm ] Mercury's motion does violate Newtonian gravity. General Relativity however simplifies to Newtonian gravity for various low-dimension applications though (i.e. an Apple falling from a tree, the orbit of the moon for most astronomical guidance purposes over that distance etc.) In much the same way we don't account for the curvatur…

>"General Relativity however simplifies to Newtonian gravity" I still don't see how this is possible. In GR gravity travels at the speed of light, in Newtonian mechanics it is instantaneous. I have been unable to find an acceptable explanation for how these two very different universes can be compatible.

I think the point is that they are compatible at sufficiently small scales.

Re: Confronting the Credibility Gap for Crewed Exploration of Mars

#87

Post by Animats »

chandmer wrote: post #60
Jarwain wrote: post #50

Earlier quoted context omitted.

I feel like a good first step would be setting up an orbital base/space station that orbits mars. It might be be a little easier than habitation On the planet itself, and more risk for the astronauts involved. However, if we set that up using knowledge gleaned from the ISS, I think its a viable path to take.

The attractive thing about landing on dirt is that the raw materials mean that a closed life support system isn't needed. There are relatively accessible supplies. Space stations anywhere, be that LEO, lunar orbit, Mars orbit, deep space, or floating in Venus' atmosphere, lack that option.

That means building a mining operation and industrial plant on Mars. Big job just for a few explorers.

Re: Confronting the Credibility Gap for Crewed Exploration of Mars

#88

Post by dTal »

jcoffland wrote: post #83
dTal wrote: post #76

Earlier quoted context omitted.

Interesting proposal. You still need a lot of delta vee to get a harpoon+cable from orbit to the surface. You can't just fire it straight down, you have to cancel most of your orbital velocity (which would have to be way out at geostationary). Dunno what the strength requirements of the cable would be either, but I imagine the answer is "not small". Doing the same trick to Earth probably wouldn't be that much harder…

You don't need to get the entire mass of the elevator down initially. Just the harpoon and cable. Many of the ideas for visiting other planets could and should be tested on earth first. I think we need to get comfortable with visiting the moon and performing large scale industrial projects in space before we have any chance of visiting remote planetary bodies and returning.

>You don't need to get the entire mass of the elevator down initially. Just the harpoon and cable.

That's what I said. The trouble is there's no "just" about it. A cable long and strong enough is going to be extremely heavy, never mind the "harpoon". In a traditional "harpoon" the cable is a small fraction of the total mass - you can't really afford that kind of design (shoot heavy thing, drag negligible thing behind) so it's not clear how the orbital dynamics would work. You'd be looking more along the lines of little tug rockets spaced along the length of the cable.

>Many of the ideas for visiting other planets could and should be tested on earth first.

Quite. This Mars stuff is completely pie in the sky. Let's see a self-sustaining habitat in a desert on Earth, never mind even the moon. As an incidental benefit of solving this we would be able to perform sustainable agriculture anywhere on Earth.

Re: Confronting the Credibility Gap for Crewed Exploration of Mars

#89

Post by nine_k »

jcoffland wrote: post #81
nine_k wrote: post #74

Earlier quoted context omitted.

The access to solids is definitely a problem. One approach might be digging them from the surface and lifting up using balloons. High temperatures don't help, but without the need to stay on the surface for very long periods, the digging robots may probably accumulate enough cold while high in the atmosphere, and then dive down for a short while, managing the temperature e.g. by melting and boiling the coolant, then…

Don't forget the extreme pressures on the surface which have crushed every probe we've sent there.

A few Soviet probes made it to Venusian surface and managed to even transmit pictures and scientific data.

High temperatures killed them in a matter of hour or so, though.

https://en.wikipedia.org/wiki/List_of_missions_to_Venus

Re: Confronting the Credibility Gap for Crewed Exploration of Mars

#90

Post by nonbel »

Crespyl wrote: post #86
nonbel wrote: post #72

Earlier quoted context omitted.

>"General Relativity however simplifies to Newtonian gravity" I still don't see how this is possible. In GR gravity travels at the speed of light, in Newtonian mechanics it is instantaneous. I have been unable to find an acceptable explanation for how these two very different universes can be compatible.

I think the point is that they are compatible at sufficiently small scales.

You really cannot introduce any lag at all and have newtonian gravity work. Try it, the system will soon fly apart.
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