Confronting the Credibility Gap for Crewed Exploration of Mars • Hacker News Board

Re: Confronting the Credibility Gap for Crewed Exploration of Mars

#91

Post by ColanR » Wed, Dec 21, 2016, 9:19 PM UTC

Animats wrote: post #87

chandmer wrote: post #60

Earlier quoted context omitted.

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.

With robotics, it's no harder than any other pioneering expeditions humans have conducted.

Re: Confronting the Credibility Gap for Crewed Exploration of Mars

#92

Post by Animats » Wed, Dec 21, 2016, 9:38 PM UTC

ColanR wrote: post #91

Animats wrote: post #87

Earlier quoted context omitted.

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

With robotics, it's no harder than any other pioneering expeditions humans have conducted.

As I told the robotics people at Stanford who were talking about something similar on the moon in the 1980s, "how soon can you do it in Arizona?" The machines sent to Mars so far are very small and wimpy. Because they're semi-teleoperated, and have very limited solar power, they're really slow. If you want to do any high-power activity on Mars, you'll probably have to send a nuclear reactor.

Re: Confronting the Credibility Gap for Crewed Exploration of Mars

#93

Post by dwaltrip » Thu, Dec 22, 2016, 12:27 AM UTC

brilliantcode wrote: post #69

Why Mars though? Why not build a lunar base on the moon? Maybe even a hotel on the moon, I'm sure people will enjoy watching earth from the moon. I just fail to see this obsession with Mars. We don't even have manned landing on Mars and we are already having questionable stuff like "Mars One" And finally (one for the conspiracists): nearly 50 years ago we landed on the moon without any of the technology we have today…

My understanding is that the Moon has far less useful resources. Sustaining any kind of base or colony on the Moon would require a larger degree of constant imports and may be much harder to sustain.

Another huge factor is the lack of consistent solar power. 14 out of every 28 days have zero solar. Mars doesn't have this problem.

There are other lesser factors as well, off the top of my head: weaker gravity which may affect health, the psychological problems with 2 weeks of solid darkness every month, and less scientifically interesting.

However, it may be still worth considering.

Re: Confronting the Credibility Gap for Crewed Exploration of Mars

#94

Post by nickparker » Thu, Dec 22, 2016, 1:17 AM UTC

chandmer wrote: post #22

nickparker wrote: post #17

There's a very enjoyable discussion in the comment section with my (brilliant) former colleague Max Fagin. He points out that Casey's first draft of this post neglects the curvature of Mars, and when you account for it Casey's model predicts the craft punching out the other side of the atmosphere.

Always appreciate careful criticism! It turns out the ratio of centrifugal-gravitational force to aerodynamic force is about 10:1, so punching through the atmosphere is a solvable problem. I love Max's videos! -C

Oh man, I hadn't seen those videos before. That's gold.

Off-topic, but your post popping up with the Hyperloop One name attached helped me decide[1] to sign w/ you folks instead of another company for Summer 2017, so see you in a few months!

[1] I was probably picking Hyperloop anyway, a cool Mars post + vague affiliation with Max just made it easier :)

Re: Confronting the Credibility Gap for Crewed Exploration of Mars

#95

Post by fapjacks » Thu, Dec 22, 2016, 1:26 AM UTC

james-watson wrote: post #35

chandmer wrote: post #24

Earlier quoted context omitted.

Sorry to come across as grumpy. It wasn't really the venue or topic to argue about exotic propulsion. There are many excellent resources online explaining why EM cavities are reactionless. You can write down the Poynting vector and then use Green's theorem, it's a neat result. With dire consequences for wish-powered spacecraft. -C

Don't be sorry. We need scientists to be skeptics when it comes to absurd assertions which violate the most fundamental principles of physics. Extraordinary claims require extraordinary evidence.

There's actually a difference between being skeptical and calling this thing -- with peer-reviewed research[0] -- "wish-powered".

[0] http://arc.aiaa.org/doi/10.2514/1.B36120

Re: Confronting the Credibility Gap for Crewed Exploration of Mars

#96

Post by jcoffland » Thu, Dec 22, 2016, 9:42 AM UTC

dTal wrote: post #88

jcoffland wrote: post #83

Earlier quoted context omitted.

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…

The harpoon could be a big heavy thing. Perhaps we crash an astroid into Mars that is trailing a cable. That doesn't really jive with the planetary protection principals but it might be the kind of thing we need to consider to get the job done.

> As an incidental benefit of solving this we would be able to perform sustainable agriculture anywhere on Earth.

True. Although sustainable on Earth usually also means economical. I would like to see a sustained habitat on the moon.

Re: Confronting the Credibility Gap for Crewed Exploration of Mars

#97

Post by namlem » Thu, Dec 22, 2016, 6:05 PM UTC

semi-extrinsic wrote: post #85

namlem wrote: post #80

Earlier quoted context omitted.

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.

Musk hasn't discussed the exact details of his plan, but it seems like the unmanned missions in 2018, 2020, 2022, and possibly 2024 (if there's no manned mission that year) are meant to establish a rudimentary fuel production infrastructure and start producing fuel in anticipation of a manned mission.

NASA, I believe, is currently trying to solve the problem with more efficient engines for interplanetary travel. Ion drives seem to be the preferred method, but there is still some research going on in nuclear thermal rockets.