[iwwr]

Nuclear appears to be the only realistic contender. But the mission architecture of Artemis goes around the problem by having only short stays on the lunar surface.

Even with nuclear, it can be far safer: small reactors need less containment. There is no risk of fallout without an atmosphere, and no ground water to contaminate.

Still, relying too much on it and failing (melting down) will put in danger the whole human space program. For low-power unmanned applications the RTG remains unbeatable.

[perihelions]

- "There is no risk of fallout without an atmosphere"

I'd speculate that it would spontaneously propagate along the lunar surface through electrostatic forces. The fallout particles would be highly charged (self-ionizing), very small, and in a perfect vacuum -- a recipe for some seriously weird dust physics.

[idontwantthis]

How much more dangerous would that be compared to space normally?

[marcosdumay]

Space usually stops being dangerous once you get into some atmosphere. Nuclear waste doesn't.

[itworkslikethat]

Space is very irradiated, and direct sunlight is radiation itself. Anything you add there will be a drop in the ocean. Atmosphere is not sufficient to resolve space radiation, you need a magnetosphere.

[marcosdumay]

You don't take sunlight inside with you when you enter some place.

You take neutron radiation (well, its consequences), but that is pretty much non-existent when compared to nuclear waste.

[dragonwriter]

> There is no risk of fallout without an atmosphere

Fallout is mostly irradiated material spread by an explosion, so as long as you have a surface and some amount of debris from an accident that doesn’t reach escape velocity you can have fallout.

[cratermoon]

> There is no risk of fallout without an atmosphere

Studies have shown that in lunar vacuum, fine dust in the regolith can travel halfway around the globe and even end up in lunar orbit and beyond with just a little kick. https://www.theverge.com/2019/7/17/18663203/apollo-11-annive...

[jillesvangurp]

Rtgs are quite common already indeed and will likely be a part of the solution. But it's a stretch to call nuclear the only contender. Cables are a perfectly valid way to move power around from areas that do get solar exposure. And there are plenty of ways to create batteries or store energy. It might even be possible to use resources on the moon to build those (e.g. a heat battery would be doable).

The key limitation is going to be transporting stuff from earth. Solar panels have a key advantage here: they are pretty light and easy to deploy. There's no wind or weather that will dust them over. And per launch, you can move some significant amount of power generation.

[Stupulous]

What does the risk profile look like for launching nuclear fuel through our atmosphere? It seems intuitively concerning, but I don't know much about nuclear.

[dotnet00]

It isn't too big of an issue, rockets have to meet certain requirements to fly nuclear material. The flight profile is required to be over water, so intact material just gets diluted or sinks. There are some requirements about how the flight termination system works (eg it shouldn't spread payload debris over a large area) and general reliability considerations identical to those for human spaceflight.

Essentially, flying nuclear material is treated with the same level of basic care as flying humans.

Once the material is in space the regulations aren't as thorough, I imagine the most that NASA considers is for the launch to be into a direct injection orbit or at a sufficiently high parking orbit that there isn't an immediate risk of uncontrolled reentry in case of some failure.

https://space.stackexchange.com/questions/17518/what-does-it...

[acidburnNSA]

Basically zero. Unused nuclear fuel is not very radioactive. You can hold it in your hand with a glove. Once you split atoms it becomes more hazardous, but space nuclear doesn't start up until after it's been successfully lifted.

[Vox_Leone]

>>Nuclear appears to be the only realistic contender.

The absence of atmosphere would make it viable to beam electrical energy down from orbit. Seems cheaper.