Viewing a single comment thread. View all comments

wave_327 t1_j2dfitl wrote

someone saw that kurzgesagt video on how to terraform Mars with lasers

157

athomasflynn t1_j2dqoeh wrote

Lasers and microwaves are both pretty inefficent for this. A few dozen heliostats could easily melt regolith from lunar orbit. Focusing a hundred square meters of reflected sunlight on a single square meter will melt a diamond when there's no atmosphere to attenuate the energy.

80

driverofracecars t1_j2e6jvb wrote

Does diamond melt? I know in the presence of high temperature oxygen, diamond will burn but idk what it does in a vacuum.

22

athomasflynn t1_j2e7qv7 wrote

I actually have no idea. I have some experience with allotropes of carbon at high temperature but that was also at high pressure in a fluid environment. I have no idea what would happen in a vacuum but that wasn't really the point I was making.

Not a lot can stand up to unfiltered solar power when it's concentrated 1000 to 1. The energy is free, they'd only need propellant to set and maintain the orientation of the mirrors. With enough of them they could probably cut a tunnel straight down.

22

MyTurntableAccount t1_j2eexuk wrote

That would be so damn cool.

5

athomasflynn t1_j2egtpu wrote

I completely agree. I thought about it for the first time 5 or 6 years ago when they were talking about 3D printing habs. I had a giant 3D printer (100x100x150cm) that I would run nylon through and it used more power than the rest of the building it was in. I couldn't see the practicality of 3D printing with local materials in an environment where energy efficiency was key. It didn't make sense. But if the energy was essentially free, instead of 3D printing they could essentially build a solar powered CNC machine.

Living underground makes more sense anyway. They need all the radiation shielding that they can get. Put the water supply on the roof above the living spaces and they'd be even safer.

There's a reason Musk started his boring company.

11

greenmachine11235 t1_j2eimzz wrote

The benefits of 3d printing is you can take raw materials to orbit and create a structure that couldn't exist in 1g conditions with no or little waste. CNC milling creates lots of waste as shavings and chips that are hard to reform into usable materials.

7

athomasflynn t1_j2eks2s wrote

You're missing the point.

The RFP was for 3D printing ground based habitats. Nothing that NASA or the ESA has actually pushed forward in terms of habitats involved 3D printing in low g. The competitions that they actually spent money on were for surface structures.

We're not talking about an actual CNC. The "wasted material" you're talking about is vaporized lunar rock. There's plenty to go around and you get a couple orders of magnitude more volume for your energy input by cutting down into it rather than building up with it. And that's before you even run the math on radiation shielding. Nobody is living off Earth without several meters of mass between them and the outside for any length of time any time soon

I like 3D printing, I've spent half a million on it over the last 10 years or so, but it's overhyped and it gets dropped in as a magic solution for every problem these days.

9

off_the_cuff_mandate t1_j2fgh91 wrote

If they made a big enough tunnel the off gassing would effect the lunar orbit

0

athomasflynn t1_j2fhj9z wrote

That's so far beyond the capability of our species that it's not even worth discussion. It's like saying that if we built a big enough skyscraper we'd have to worry about it knocking down satellites.

7

Apokolypze t1_j2e77k8 wrote

Pretty sure everything melts if you get it hot enough

5

driverofracecars t1_j2e7ycf wrote

According to google, diamond in a vacuum, when heated high enough, sublimates straight to gaseous carbon. In order to liquify diamond, you need pressures nearly 100,000 times greater than atmospheric pressure at sea level AND lots of heat.

33