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Design of a rapid transit to Mars mission using laser-thermal propulsion

arxiv.org

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Re: Design of a rapid transit to Mars mission using laser-thermal propulsion

#51

Post by jvanderbot »

bayesian_horse wrote: post #45
jmyeet wrote: post #2

Sure let's continue unmanned exploration of Mars but manned exploration let alone colonization makes absolutely zero sense. mars is nothing more than a further, more annoying version of the Moon. Similar gravity, less sunlight (ie further from the Sun), communication latency (~10 minutes vs 1.5 seconds), no magnetosphere (just like the Moon so you'll probably need to live underground) and just enough atmosphere to pr…

Gravity is higher, which is important for Humans. Also the resources are more diverse. And you can study Mars better from the surface of Mars than from the surface of the Moon (duh...). I'm not a massive fan of Mars colonization. But I do get the appeal of getting manned missions there. Some science really can't be done as well or cheaply by robots alone. Though even with Humans on board, much of the work will be don…

> Some science really can't be done as well or cheaply by robots alone.

I'm struggling to imagine how a "lab full of equipment, life support, beds, bathrooms, comms, and return rocketry" doesn't ($-wise) translate much better to "many, many more teleoperated robots with miniaturized labs operated from orbit or Earth with frequent sample return round-trips".

Boots on the ground is a moral victory, but I don't see the science victory until you get enough equipment / personnel there to get a thriving ecosystem of thought in-situ. Not to mention: Astronauts are rarely the scientists that study the place they are going.

Now an ISS around Mars? That makes a lot of sense to me.

Re: Design of a rapid transit to Mars mission using laser-thermal propulsion

#52

Post by ben_w »

bayesian_horse wrote: post #42
ben_w wrote: post #11

Earlier quoted context omitted.

Disaster recovery, the penultimate in off-site backups of humanity itself.

We're better off riding it out in a bunker or something on earth. It's easier to build something self sustaining on earth that can survive anything, than build the same thing anywhere else.

We can do both. Even Musk’s plan is aiming at 10s of hours of 2020 global GDP spread over the best part of a century.

Re: Design of a rapid transit to Mars mission using laser-thermal propulsion

#53

Post by foobarian »

jmyeet wrote: post #23
kilroy123 wrote: post #20

Earlier quoted context omitted.

I strongly disagree and I dare say this is an incredibly short sighted view. Pushing forward to living on Mars will unlock tons of technological and scientific advances that will only help us better live here on Earth, and Mars. The mother of invention will always been necessity. We simply don't need a lot of the tech that will be created, until we try to live off-world. So much technology and scientific know-how, ca…

Let's accept this premise (which amounts to essentially "we don't know what we don't know") and I'll ask a natural follow up question: what is the difference between colonizing the Moon and colonizing Mars in terms of problems we'd need to solve and thus technology we'd likely gain?

I always thought the "but look at all the science we got out of it" line was rationalization. The Moon race happened because it was a contest. The reason I would buy for either Moon or Mars colonies would be access to resources in the belt.

Re: Design of a rapid transit to Mars mission using laser-thermal propulsion

#54

Post by Retric »

sevenf0ur wrote: post #16
jmyeet wrote: post #2

Sure let's continue unmanned exploration of Mars but manned exploration let alone colonization makes absolutely zero sense. mars is nothing more than a further, more annoying version of the Moon. Similar gravity, less sunlight (ie further from the Sun), communication latency (~10 minutes vs 1.5 seconds), no magnetosphere (just like the Moon so you'll probably need to live underground) and just enough atmosphere to pr…

Agreed, if an extinction level event happened on Earth, we'd be better off riding it out underground, than moving off planet.

I agree going to Mars is never going to be a useful for evacuation, but it could help if we where already there.

Most plausibility the long duration space flight should prevent the common cold from making the trip which would also prevent many hypothetical super plagues from doing so as well. In theory you could do the same on earth, but it’s unlikely for a self sustaining underground colony to consistently maintain that level of quarantine for new arrivals.

However getting a self sustaining population on Mars that could survive indefinitely is currently just science fiction and making the trip is the least difficult hurdle for changing this.

Re: Design of a rapid transit to Mars mission using laser-thermal propulsion

#55

Post by tejohnso »

bdamm wrote: post #6

We must go to Mars, if only to convince people on Earth that there really is no second planet.

Hopefully people start to behave as though there is no second plant long before we go to Mars. Otherwise there will be nobody left to send there.

Re: Design of a rapid transit to Mars mission using laser-thermal propulsion

#56

Post by O5vYtytb »

jmyeet wrote: post #32
mchusma wrote: post #27

Earlier quoted context omitted.

I also think Dyson swarms are the future. But I think the Mars effort is helpful towards getting there. Elon's public motivation for Mars is basically a human backup plan. And for that, it probably may be the best shot of the next 100 years. It seems like a million people living and working on Mars is more likely to survive a worst case scenario that a million people in rotating space habitats.

But how is the Moon not a sufficicent backup plan?

How can a moon civilization support itself without the Earth?

Re: Design of a rapid transit to Mars mission using laser-thermal propulsion

#57

Post by ceejayoz »

maxerickson wrote: post #48
gambiting wrote: post #47

Earlier quoted context omitted.

I'm positively certain that in all of your examples people have pushed into new areas because of food, to find new land to live on, to find riches, to find the promised land or other mythological reasons. Somehow I don't imagine aborigines crossing the ocean because "it's cool". You know what we're going to find on Mars? Rocks. A whole lot of radiation. No breathable atmosphere and freezing temperatures. Imagine the…

Like if you could build something awesome on Mars it would pretty much universally be easier to build it in North Dakota.

Sure. It's easier to build in North Dakota than it is in the Swiss Alps, too, but people do that in part because they like the Alps.

There are going to be people for whom the idea of a frontier life in a place of natural, untouched beauty appeals. We've always had those folks. Some of them find life is harder than they expected; some thrive.

Re: Design of a rapid transit to Mars mission using laser-thermal propulsion

#58

Post by ceejayoz »

gambiting wrote: post #50
merpnderp wrote: post #24

Earlier quoted context omitted.

Except 8 billion starving desperate people trying to get it. For instance if people were starving or hiding from fallout, those doomsday shelters the rich are building for themselves would likely be overran by the locals who helped build them or heard all about them from town gossip.

How are those 8 billion starving people getting into a base 10km below the surface of the ocean which requires a specialized submarine to get to? How is this any more realistic than 8 billion starving people getting to Mars? And finally - I hope you aren't suggesting that the base on Mars is a way to escape "8 billion starving people".

You don't have to get to it to affect it. Eight billion very pissed off people can probably figure out how to drop rocks on the rich billionaire haven in an ocean trench.

Re: Design of a rapid transit to Mars mission using laser-thermal propulsion

#59

Post by zackmorris »

0_____0 wrote: post #12
slothtrop wrote: post #9

Earlier quoted context omitted.

If terraforming is in the cards, stands to reason it would be first tried in our own backyard. Mars is the best contender for it. Actually it might be useful in other respects than being livable. The vision is far less romantic if you consider it a distant future project.

At least Venus has a magnetosphere. How are you going to terraform a planet that can't retain more than 6.5 millibars worth of atmosphere? Build a big-ass bubble around the planet to deflect solar wind? Nuke the core of the planet to re-melt it and get a magnetic field back?

Ya I think that we'll fail to make any measurable impact on global warming in our lifetimes, because it's much easier to sabotage movements than to invest in them. So we'll inevitably reach for a solution that's a sure thing, and the only one I know of that's scalable is a 1-10 atom thick sunshield at the L1 Lagrange point. It's a problem similar in scope to a light sail, so there's no mystery to it other than trying to grow the dang thing in space.

So if Earth gets a sunshield, it's no more difficult to grow one for Venus. Then eclipsing it and getting it to room temperature would only take a matter of weeks maybe? That would reduce the atmospheric pressure too. Seems like an orders of magnitude easier problem than waiting around for Mars to warm up and pressurize. Although on that note, we could build a giant reflector at the L2 point behind Mars to have room temperature immediately there too.

Looks like a solar sail can be as light as 0.00002 kg/m2, the Earth has a cross section of about 125 million km2, or 1.25e14 m2, so that's 2.5 billion kg or 2.5 million metric tons. Of course there's always a way to make a thinner sail, and we may not need to block all of the light, so I think a million metric tons is a reasonable estimate. Sounds like a lot, but a locomotive is 1000 metric tons, so 1000 train engines or 10,000 heavy launches to save Earth doesn't seem unreasonable. Also we probably only need 1% of that area to have a measurable effect on climate, and that way we wouldn't have to see the shadow either. So we're talking 10 train engines or 100 heavy launches.

https://en.wikipedia.org/wiki/Solar_sail#Materials

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