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Comment by wallflower | Hacker News Reader

Buzz Aldrin is very passionate about colonizing Mars [1]. He says there are two big things that have to be accomplished before we can colonize Mars. The first is to train astronauts to live in a confined isolated space for 260 days (the length of a journey to Mars) [2]. This alternative journey trajectory increases the 260 days.

The second is harder: We need to go to Mars at least three times and bring back the men and women successfully. Once is not enough. Three proves we've mastered the engineering, financial, physical, and physiological aspects.

[1] http://www.pbs.org/wgbh/nova/space/aldrin-mars-au.html

[2] http://www.guardian.co.uk/science/2010/jun/03/mock-mission-m...

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> We need to go to Mars at least three times and bring back the men and women successfully.

First we'd need to find a way to bring back pretty much anything else successfully, no?

The first is an easy problem to solve, compared to pretty much every other issue. More space (or better space) is a non-linear issue.

Unless you're envisioning spacecraft with literally hundreds of astronauts, the first will be anything but easy to solve. Doesn't help having an awesome spaceship if everyone on board goes batshit crazy after six months.

Bubbleheads are tested in Submarine School for compatibility with the idea of living in the intellectual equivalent of a sewer pipe for months on end with each other. I'd assume NASA would do the same. End of the day make sure you know who holds the keys to the weapons locker.

Why do we need to bring them back? Pioneers don't normally set off with a guarantee or even likelihood of coming back.

If in 1500 you dropped some European settlers in the Americas, there a high chance they'll survive. If in 2014 you drop some settlers in Mars, they would surely die.

Plenty of robots must be sent beforehand to build greenhouses, setup solar panel arrays, dig deep tunnels to provide shielding against cosmic radiation, etc.

A one way trip is more feasible. Resources spent on supplying a base will yield more knowledge, if slightly less PR.

Furthermore, if there are indigenous biologic agents there, I don't think we want them coming back. Like the Greek expedition to Asia Minor, Mars is a burn the ships mission.

If you can guarantee #2, doesn't #1 become much more difficult?

Not really. Either we are going to inhabit Mars as residents or just spend money on space tourism. If we're intending to inhabit it, then the deal has to be one way. Otherwise, sending machines is vastly more cost effective.

Elon Musk has said from the beginning of SpaceX that trips to Mars would have to return as well. It's not because of the humans but because the cost of producing the space ships will be so large that it's not feasible to shoot them to Mars once and leave them there; they have to be reusable.

> The principle behind all of its vehicles is total re-usability; every single system must be able to be serviced and pressed back into operation. This is to cut down on the already astronomical cost of space flight (pun intended), making it more affordable for private companies to conduct missions into the heavens. The company’s main goal is to eliminate the equipment cost for space travel, leaving fuel as the only financial burden.

http://www.extremetech.com/extreme/122923-spacex-ceo-claims-...

The ship itself returning would be relatively trivial as long as it didn't need to degravitate from Mars.

That doesn't mean you have to return from the ground. Have the large reusable craft swing by Mars without slowing down, dropping off a small daughter ship/lander, and continuing back to Earth.

> It's not because of the humans but because the cost of producing the space ships will be so large that it's not feasible to shoot them to Mars once and leave them there; they have to be reusable.

The problem with the return trip is Earth reentry. Coming in at interplanetary speeds (falling to the sun from a "height" of Mars' orbit to Earth's), it is impossible for humans to reenter the Earth's atmosphere safely. It's barely possible from the moon.

This means that there has to be about as much deceleration before reentry than there was there was acceleration on the way out. So now you have to carry double the fuel, and the fuel to carry that, etc. This vastly complicates the problem with a manned mission to mars.

This is one reason why it's often thought that a long-term station in Earth orbit (possibly at one of the Lagrange points) is a pre-requisite for a Mars mission. So, you could decelerate to the station instead of to re-entry. But, it is possible if one sent enough supplies ahead.

One way of handling things if there's a long-term station is to build the ship to Mars in space (or at least refuel at the station). If you send the return fuel ahead (or find a way to make it while at Mars) you aren't required to carry a large amount of fuel.

You still have to carry twice the fuel. What about a refuel station orbiting mars? Replenish the mars fuel station with fuel before the manned mission departs, they can just use that fuel stored at Mars when they return from the manned mission.

Deploying a station orbiting Mars would be pretty expensive.

Lunar speed reentry is quite feasible, and has been practiced. Apollo did it fine, and Orion did it a few weeks ago. State of the art ablative shields, like the PICA-X used on Stardust and Dragon, are quite capable of handling entry at Mars transfer speed. (Lunar entry profile is about 11km/s, Mars 13-14km/s--though it can go as high as 20km/s deformation on design.)

The real problem with the return trip is getting off Mars. Specifically, putting enough propellant on the surface to get you back up. Sure, it's easier than Earth, but it's still a planet. If NASA were serious about Mars, they would be sending prototype ISRU plants every cycle, because having rocket fuel waiting for you on the surface is the real enabling technology for Mars exploration. Or Lunar or Venus for that matter.

It's not just getting fuel to Mars. It's building and operating launch infrastructure there. Unmanned LEO missions from KSC get delayed and fail. On Mars there won't be spare parts or separate ground crews, and the spacecraft will have to be readied having been through launch and touchdown cycles rather than a slow gentle roll from a VAB to launch pad.

The speed of light means no real time support from Houston. If ten people go out, then ten people have to get an interplanetary space program established on Mars. It ain't gonna be a matter of pushing the easy button.

Why re-enter?

> two big things that have to be accomplished before we can colonize Mars

Colonizers could probably live on packaged food from here 'til Judgment Day (or as long as Earth is willing to send always more supplies), but I would still add the maintenance of man-made ecosystems for food production to the list of big problems that we have not yet solved.

The biggest problem is not food, it's radiation.

>> The first is to train astronauts to live in a confined isolated space for 260 days

Bubbleheads can do that, current and ex.

>> We need to go to Mars at least three times and bring back the men and women successfully.

I don't know that the delicacy of the orbital entry described is going to be sufficient for long term operations. It sounds like an artistic dance combined with luck. I think the old wing it into space at high velocity then put on the brakes method is more deterministic. Whole transportation systems on Earth function this way.

Wouldn't they have to live in a confined isolated space on Mars too?

Yes. Mars has an extremely thin atmosphere that would kill us if we did not have pressurized suits and stations.

Don't forget the radiations. The main problem of the Mars atmosphere is that it's too thin to stop enough of them for human beings.

A spacecraft could double as living space on the planet, alongside whatever other prefab buildings they bring along. A cargo hold packed full of prefab walls could itself double as building space, once emptied. Also there would be more opportunities to leave those spaces to go outside.

It would certainly still be cramped by conventional standards, but conceivably much less so than the flight there.

They'd be getting out of the habitat regularly to do science/construction, though.

Yes. Beyond food and supplies, people would have to either want to spend their lives while on Mars in containerization or there would have to be a large pressurized common area for work and socialization. With a thin atmosphere stuff falling from space is a problem as it would be on the Moon so building underground would be required. That's why I think going to Venus first makes sense, get people used to the long travel periods living in confined spaces dependent on machines.

You can build more space from local materials.

Also excursions, though you need a space suit.

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