I suspect this will in the end be solved in utmost unsexy, boring and reliable way by solar plus huge NiFe battery and/or hundreds of kilometers of high voltage grid, manufactured by robots from local resources or asteroid mining.
Or somewhat sexier, beamed orbital power or mirrors are less technically challenging than on earth.
Either should be less expensive than hauling nuclear reactors from earth and ensuring they get reliable cooling.
> "manufactured by robots from local resources or asteroid mining."
I feel like this just creates the new problems of operating, powering, and maintaining the robots, plus all the difficulties associated with mining asteroids and refining the mined materials somewhere (presumably somewhere that's not Earth's surface, which means we still need to generate power somewhere off Earth for this to work).
I am still awaiting the future promised me where 3d printers replicate themselves. This is orders of magnitude easier than robots making themselves in outer space, yet we are still waiting and I assume we always will be.
Orbital power has the huge advantage that setting it up is essentially independent of the rest of the mission - we can set up most of the work in advance, so that part doesn't count towards a weight limit and we can abort/wait if it doesn't work. Once a secure base using orbital power is set up, then NiFe should be arranged for redundancy.
What’s wrong with operating half the day? I guess it’s space, so it’s worth a lot of effort, but I’d think if they can avoid RTGs and just use solar they would.
I think the heat part would best be Feolite, which is mostly sintered iron oxides, but with some other bits added. It has a tremendous volumetric heat capacity, nearing that of water, but you can crank it way past 100 C without worrying about pressure.
One of my all time favorite everyday engineering things I've learned is the absolute bonkers amount of energy needed to boil water (vs nearly any other fluid).
It's so commonplace yet absurd/impressive when you really think about it.
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.
- "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.
> 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.
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.
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.
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.
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.
Nuclear is probably most practical for long term generalization, for now I think the approach all crewed landers have proposed to use is to place panels as high up as they can to maximize sunlight duration.
At the poles this could enable some permanent power generation by getting the panels high enough to access permanent sunlight.
People survive Antarctic winters so I can't see that there is a particularly big challenge. There is no atmosphere on the moon so heat loss to the sky is purely radiative whereas in Antarctica you have winds blowing that cool the habitats by conduction.
Solar panels should be able to provide the necessary energy which can be stored in piles of rock and insulation should be able to to prevent the loss.
The 'article' says that the lunar night is rife with problems but doesn't mention what they are. There is no weather after all.
Any permanent habitation should include a smelter to alleviate some of the cost of shipping metals from Earth. From it oxygen or CO2 will be "waste" byproducts, liquefacting and storing them should not be a problem. I can imagine that having large reserve of oxygen will be desired safety feature.
Hydrocarbons will likely be in short supply on the moon but if there is, say, a zinc mined, it could be "burned" in zinc-air cells.
The lunar surface temperature is like -150C at night. And yeah, heat loss is radiative.. to a sink at roughly -273C. And night is 2 weeks long. Just use solar heaters and insulation? Well you have to fly that stuff there first, and also fly whatever equipment and people/robots to make the system.
There are various studies to have stuff survive lunar night without a nuclear source, and it takes on the order of 10kg of stuff to keep a 1kg payload alive. And in turn that takes 100kg of spacecraft/fuel to fly it all there. That’s not including the rocket and its fuel to get to Earth orbit first.
The very large temperature difference between day and night means you can bank heat in the daytime, and cold in the night, and generate power from the difference.
You need a pair of very large bags of regolith to store the heat and cold in, and a gas to percolate through them from radiators exposed alternately to sun and black sky.
Or you can just put up very big reflectors in orbit, lighting up your solar panels. Maybe they pump laser tubes pointed at your solar panels.
Nukes would be a big nuisance, needing constant maintenance, unless you just run a naked pile at incandescent temperature and catch the light coming off photovoltaically.
> Nukes would be a big nuisance, needing constant maintenance, unless you just run a naked pile at incandescent temperature and catch the light coming off photovoltaically.
If we had piles of Pu-240 we could use RTGs, though they wouldn't be very efficient considering the amount of mass we'd have to send.
Running a naked reactor doesn't sound so bad considering there's no atmosphere or water sources to poison -- just stay away from the reactor. Running a steam turbine shouldn't be too hard, but it probably can't be serviced -- if it breaks, you replace it.
Sealed free piston Stirling engines might be even lower maintenance and can provide a number of kilowatts pretty simply. Couple with a fast reactor or a combined fuel moderator solution alas TRIGA should work.
Nuke the moon! Right now the topography of the poles necessitates quite tall towers to get into perpetual sunlight; but a bunch of judiciously placed nukes could easily take away most of the shadow-bringers (crater rims) and reduce the tower height necessary to get up into perpetual light to a small fraction of what it would be now.
Just remember: nuke first, then colonize. So, sooner rather than later.
Let's assume 10mm copper wire to the other side of the moon. 3000km long copper wire 10mm in diameter will have 600 ohms resistance. The amount of copper needed is 235 m³, copper at 9t/m³ weighting 2115 tons in total or 21 starship flights costing $21 milion.
Local aluminum will be cheaper, and stonkin' high voltage will be needed to combat the ohmic losses. The 'atmosphere' on the moon is rather extremely dry, so corona losses shouldn't be an issue, you could probably run north of a megavolt w/o too much trouble.
Now, you could lay both conductors in parallel and only need to build the power line half-way around the moon, probably save some dough on prospecting for and constructing pylon sites that way. Alternatively, you could run a single conductor all the way around. Doing that, you could establish a lunar scale magnetic field, though it'd probably be pretty wimpy unless you ran serious kA (MA?) of current, which would mean much bigger conductors etc, but it's fun to think about. Heck, with a loop that big, you'd probably get significant induction from the solar magnetic field .. which might be something to harness, or might just be a headache for your line operators.
> Doing that, you could establish a lunar scale magnetic field, though it'd probably be pretty wimpy unless you ran serious kA (MA?) of current, which would mean much bigger conductors etc, but it's fun to think about.
Or a stator in orbit? But hrm… for Mars the same idea needs only 1T to 1.5T stator but has to place xt at lagrange between Mars and Sun. So, I naively guess for the stator to be far enough away that the deflected solar wind merges after the moon could /reall/ mean that the stator would be at lagrange between Earth and Sun, which could have perhaps interesting effects on Earth.
This seems like a chicken-and-egg problem. Wouldn't you need power in the first place (and therefore transmission lines) to even extract and refine aluminium locally?
But even at $100m/launch, a big fat copper wire (IIRC aluminium is better per unit mass) would still make more sense than shipping up a nuclear reactor or a huge pile of batteries, and that part of this hypothetical mission would still be about 80% cheaper than the JWST.
Payload to low earth orbit might be 100+ tons each. But payload to lunar surface is a small fraction of that. We could assume 10 tons. So 210 starship flights.
One can see pretty quickly that any larger constructions far from earth would really benefit from maximum use of local materials.
There wont be much left on the other end because of volt drop in cables. But can be possible to make it into a HVDC transmission line. Will add bit of weight on the starship.
You definitely need HV. At 100kV and 10A, the lost power if you send 1MW is around 60kW: a fairly serviceable 6% or 20W/km. However, your losses at a fixed voltage scale quadratically with your power draw: you'd lose 24% of 2MW.
If you sent it at 1000V, the I²R losses to send 1000A over that cable outweigh the transmitted power by 600 to 1 and your cable is burning 200kW per kilometre. Which in a vacuum would probably just melt it in fairly short order.
Which is why the bigger HVDC links get, the higher the voltage: there's a 1MV+ system in China that sends 12GW over 3000km.
Also I'm not sure how lunar regolith will work with regards to the "earth" return path so you might well actually need two wires.
600Ω (WolframAlpha gave me 510, but let's go with the bigger number) isn't that bad, and you don't need anything expect bare metal to run HV on the moon because both the vacuum and the regolith are already insulators.
How awesome would it have been if Artemis actually carried a payload to just dump off on the moon? It's just so absurd that this feat of engineering and rocket science just did a fly by/test.
Starship and Superheavy ("can and kicker") will not realistically cost any less than $20M per launch, plus whatever what you are launching costs to make, stow, and deploy. If it takes 100 tons to orbit, that is $200/kg minimum.
Getting a can to the lunar surface takes launching a bunch of fuel runs, so that much several times over, say $1000+/kg all told.
Bringing cans back from the moon would be counterproductive, except as needed to bring crew home. Maybe you unmount used vacuum engines, cut their bells off, and bring home the fiddly bits. Somebody should find a use for the cast-off cans, eventually, and the cut-off bells. Maybe swing the cans on the ends of a wire for artificial gravity so your bones don't dissolve; though getting in and out would be tricky. You could store energy in their kinetic motion, resolving the nighttime power problem at the expense of variable artificial gravity inside.
Readit News
Or somewhat sexier, beamed orbital power or mirrors are less technically challenging than on earth.
Either should be less expensive than hauling nuclear reactors from earth and ensuring they get reliable cooling.
I feel like this just creates the new problems of operating, powering, and maintaining the robots, plus all the difficulties associated with mining asteroids and refining the mined materials somewhere (presumably somewhere that's not Earth's surface, which means we still need to generate power somewhere off Earth for this to work).
It's so commonplace yet absurd/impressive when you really think about it.
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.
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.
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.
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...
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.
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...
The absence of atmosphere would make it viable to beam electrical energy down from orbit. Seems cheaper.
At the poles this could enable some permanent power generation by getting the panels high enough to access permanent sunlight.
Solar panels should be able to provide the necessary energy which can be stored in piles of rock and insulation should be able to to prevent the loss.
The 'article' says that the lunar night is rife with problems but doesn't mention what they are. There is no weather after all.
https://en.wikipedia.org/wiki/Army_Nuclear_Power_Program
Hydrocarbons will likely be in short supply on the moon but if there is, say, a zinc mined, it could be "burned" in zinc-air cells.
There are various studies to have stuff survive lunar night without a nuclear source, and it takes on the order of 10kg of stuff to keep a 1kg payload alive. And in turn that takes 100kg of spacecraft/fuel to fly it all there. That’s not including the rocket and its fuel to get to Earth orbit first.
You need a pair of very large bags of regolith to store the heat and cold in, and a gas to percolate through them from radiators exposed alternately to sun and black sky.
Or you can just put up very big reflectors in orbit, lighting up your solar panels. Maybe they pump laser tubes pointed at your solar panels.
Nukes would be a big nuisance, needing constant maintenance, unless you just run a naked pile at incandescent temperature and catch the light coming off photovoltaically.
If we had piles of Pu-240 we could use RTGs, though they wouldn't be very efficient considering the amount of mass we'd have to send.
Running a naked reactor doesn't sound so bad considering there's no atmosphere or water sources to poison -- just stay away from the reactor. Running a steam turbine shouldn't be too hard, but it probably can't be serviced -- if it breaks, you replace it.
Just remember: nuke first, then colonize. So, sooner rather than later.
Now, you could lay both conductors in parallel and only need to build the power line half-way around the moon, probably save some dough on prospecting for and constructing pylon sites that way. Alternatively, you could run a single conductor all the way around. Doing that, you could establish a lunar scale magnetic field, though it'd probably be pretty wimpy unless you ran serious kA (MA?) of current, which would mean much bigger conductors etc, but it's fun to think about. Heck, with a loop that big, you'd probably get significant induction from the solar magnetic field .. which might be something to harness, or might just be a headache for your line operators.
Or a stator in orbit? But hrm… for Mars the same idea needs only 1T to 1.5T stator but has to place xt at lagrange between Mars and Sun. So, I naively guess for the stator to be far enough away that the deflected solar wind merges after the moon could /reall/ mean that the stator would be at lagrange between Earth and Sun, which could have perhaps interesting effects on Earth.
Would heat pumps work on the moon?
Where can I book a Starship flight for $1M?
But even at $100m/launch, a big fat copper wire (IIRC aluminium is better per unit mass) would still make more sense than shipping up a nuclear reactor or a huge pile of batteries, and that part of this hypothetical mission would still be about 80% cheaper than the JWST.
One can see pretty quickly that any larger constructions far from earth would really benefit from maximum use of local materials.
If you sent it at 1000V, the I²R losses to send 1000A over that cable outweigh the transmitted power by 600 to 1 and your cable is burning 200kW per kilometre. Which in a vacuum would probably just melt it in fairly short order.
Which is why the bigger HVDC links get, the higher the voltage: there's a 1MV+ system in China that sends 12GW over 3000km.
Also I'm not sure how lunar regolith will work with regards to the "earth" return path so you might well actually need two wires.
Getting a can to the lunar surface takes launching a bunch of fuel runs, so that much several times over, say $1000+/kg all told.
Bringing cans back from the moon would be counterproductive, except as needed to bring crew home. Maybe you unmount used vacuum engines, cut their bells off, and bring home the fiddly bits. Somebody should find a use for the cast-off cans, eventually, and the cut-off bells. Maybe swing the cans on the ends of a wire for artificial gravity so your bones don't dissolve; though getting in and out would be tricky. You could store energy in their kinetic motion, resolving the nighttime power problem at the expense of variable artificial gravity inside.