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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

#81

Post by kitsunesoba »

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…

> mars is nothing more than a further, more annoying version of the Moon.

I would say the opposite. Compared to the Moon, Mars has:

- A day-night cycle more suited to humans that’s nearly identical to that of Earth (Moon colonies will need to be in polar areas to avoid long stretches of no sunlight)

- A more temperate climate with less dramatic temperature swings

- Gravity likely high enough for most processes and machines developed on Earth to work correctly

- No sharp, statically charged regolith

- An abundant, readily available source of Co2 for use in production of fuel, oxygen, and other materials

The primary downside is longer transit time, but that can be overcome with smart planning and could be seen as a boon in the long run since it’s a forcing factor in developing self-sustainability — moon colonies will likely remain Earth-dependent for much longer than they need to simply due to how convenient it is to get things shipped from Earth.

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

#82

Post by kitsunesoba »

jmyeet wrote: post #64
tiborsaas wrote: post #62

Earlier quoted context omitted.

With this mindset we won't get very far as a species. It was probably already a mistake to climb down from the trees, right? But seriously, what else we should do as humans? I just can't imagine we will sit on our asses because that's a reasonable thing to do. If the benefits of going to Mars only results in a new generation of humans to fall in love with space, that's already good enough. Also don't forget all the c…

> With this mindset we won't get very far as a species. I assume you're saying this in good faith but it's really a straw man argument because it's a false dichotomy. For one there's the obvious: I'm not saying "go nowhere". I'm saying "the Moon makes more sense to colonize than Mars". Also, that doesn't preclude ever colonizing Mars. A Moon-first policy just makes way more sense. Another flaw: why do we even need to…

I think that yeah, in the long term, humanity’s future in space is in human-made crafts.

That’s a long way down the road, though. Before that, we need to develop a huge amount of infrastructure in space, and doing that will be extremely expensive so long as we have to fight Earth’s gravity well to do so (even accounting for things like cheap reusable rockets).

Either the moon or mars could serve as the “stepping stone”, but I think Mars is better situated for that due to having a wider variety of raw resources available and being overall less harsh than the moon while also having a dramatically weaker gravity well and practically nonexistent (aerodynamically speaking) atmosphere that would allow launching of vastly larger and oddly shaped crafts into orbit. From there, it’s much more feasible to start looking into mining asteroids and building city-ships.

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

#83

Post by revicon »

bryanlarsen wrote: post #70
revicon wrote: post #18

Earlier quoted context omitted.

With no magnetosphere would there even be a point to terraforming?

Maintaining an atmosphere is a lot easier than creating it in the first place, and can use the same process and machines. In other words just live with the slow loss and replace the loss gradually.

I think what I meant is with no magnetosphere we would all die of radiation exposure regardless if there was a terraformed atmosphere or not. Without a magnetosphere we'd all be living underground anyway, no point in terraforming.

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

#84

Post by kdbeall_ »

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…

> mars is nothing more than a further, more annoying version of the Moon.

This is simply wrong. Mars has had the geological processes necessary for ore formation. Whereas the Moon largely lacked those processes. Furthermore, Mars is rich in volatiles. It is likely Mars has everything needed to sustain human civilization. The issue is developing the extraction technologies and proving mineral reserves on Mars.

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

#85

Post by revicon »

I haven't seen it mentioned in this thread, but a much easier place to colonize is the atmosphere of Venus. There's a band of altitude in Venus's atmosphere where it's equal pressure to earth and you'd be able to get out and walk around with a simple oxygen mask. Huge blimps could suspend colonies in this zone (think Bespin from Star Wars).

Interesting stuff, more info: https://bigthink.com/hard-science/how-to-colonize-venus/

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

#86

Post by kdbeall_ »

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?

I'm not firmly in the terraforming camp, but something I'd like to point out is that humans don't need exactly 1 atm. About 0.5 atm would be sufficient. It's analogous to what is found in Bolivia's altiplano. Mar's gravity is sufficient to hold onto oxygen and nitrogen.

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

#88

Post by 0_____0 »

politician wrote: post #30
0_____0 wrote: post #12

Earlier quoted context omitted.

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?

Watch any of the videos on terraforming Venus by Isaac Arthur on YouTube.

A brief summary of proposed methods and their feasibility and a link to further literature may do a bit better at getting your point across than the name of a youtube channel that close to 0% of the people reading this are going to seek out at your say-so.

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

#89

Post by 0_____0 »

kdbeall_ wrote: post #86
0_____0 wrote: post #12

Earlier quoted context omitted.

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?

I'm not firmly in the terraforming camp, but something I'd like to point out is that humans don't need exactly 1 atm. About 0.5 atm would be sufficient. It's analogous to what is found in Bolivia's altiplano. Mar's gravity is sufficient to hold onto oxygen and nitrogen.

True, although if you've fixed the "atmosphere gets stripped away" problem, you've achieved the hard part.

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

#90

Post by 0_____0 »

ben_w wrote: post #46
0_____0 wrote: post #12

Earlier quoted context omitted.

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?

Nuking the core is neither sufficient nor necessary for the magnetosphere. Not sufficient because all of the nukes together are orders of magnitude too little to melt it, not necessary because a spinning ball of liquid metal is a really inefficient way to make a magnet. IIRC one of the plans for an artificial magnetosphere for Mars only needed a 1 GW supply to the magnetic coil.

The core nuking thing I pulled out of my ass but I guess it sounds serious given a sufficiently fantastical context.

Doing a little more reading I came across the superconducting latitudinal "wrap the planet in a solenoid" thing, as well as magnets at L1 etc. I guess that's possible, but that's more of a 2000-years-out sort of set of ideas.

There's a philosophical debate to be had about how far out humans should be thinking when expending resources. If you build for tomorrow, you solve yesterday's problems. If you build for the next millenium, you solve nobody's problems.

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