Wind turbines are usually too inefficient on earth to be commercially viable without subsidies, and on mars the thinness of the atmospehre makes them ~170 times less effective than on earth.
On the topic of energy sources that aren't the topic of this thread, what about not going via electricity at all? Electrolysis can be supported by high temperatures all the way up to pure thermal water splitting and there is definitely need for heat to melt ice. So anywhere between simple thermal solar collectors to concentrated solar power with mirrors could be used for part of the ISRU needs. In addition, the Sabatier reaction is exothermic so a useful heat cycle could recover quite a lot of spent energy and significantly increase efficiency.
May I ask the basis for "500kW" cited upthread – from where did this figure originate? I've scanned a few other threads (e.g. 'powering Mars via eBay') that cite less than half this number for BFS propellant production, so I'm afraid I missed the work/logic that leads to 500kW. Thanks.
I see. So 500kW is not a need-defined number but rather capacity-defined, as in, "here's how much solar power a BFS can carry", correct?
500kW is about the average power on Mars you can get out of a BFS full of commercial semi-flexible mono-crystalline panels plus Tesla batteries. $25M is approximate cost of purchase and shipping to Mars on $130/kg lift. (this number assumes BFS reuse)The exact number is of course not going to be exactly that, given the need for structure, but that structure is very lightweight, with storm winds equivalent to perhaps 10MPH on earth, ...
The atmosphere is 1% the pressure but 2% the density. And wind speeds are significantly greater (average 10m/s), which is relevant because wind /power/ scales as the wind speed CUBED, so if the wind speed is 3 or 4 times that on Earth, the wind power is actually the same. That all said, not a near term source of power.
With the obvious corollary that solar reduces proportionally in costs, to a degree, but even assuming a 500kWe reactor can be had for $25M, it's pretty clear a 1kWe one will never be $50K, in the foreseeable future.The other way nuclear works is if you assume the solar panels cost is $500/W.A cosy relationship with a particular program might get you the first reactor free.It may not get you the second.
Quote from: DnA915 on 05/02/2018 06:27 pmSo NASA just released some press about the success of a new Kilopower fission reactor. Sounds like great news for space travel. Is this the sort of thing that SpaceX could use within the BFR? I realize they have these animations of fancy solar ray deployments, but the sun is not always available (on the surface of the moon for instance) and it would reduce complexity it seems too. For a ship like BFR, it seems like having a constant power supply for 10 years would be a perfect fit.The figures given above are from memory about 1500kg for a 10kW electrical solution.This is 7 watts a kilo or so, which is very bad from a solar panel perspective in the inner solar system.Juno, for examples panels get about 50W/kg around earth, and around half of that at Mars.10kW means you need about (of poor solar cells) 40m^2 near earth, or 100m^2 near Mars. Note that 10kW is only twice of the power of the Dragon solar arrays. You'd want four of these near Mars of course.
So NASA just released some press about the success of a new Kilopower fission reactor. Sounds like great news for space travel. Is this the sort of thing that SpaceX could use within the BFR? I realize they have these animations of fancy solar ray deployments, but the sun is not always available (on the surface of the moon for instance) and it would reduce complexity it seems too. For a ship like BFR, it seems like having a constant power supply for 10 years would be a perfect fit.
But I agree that this goes against the concept of BFS, as it is supposed to land on Earth again. Too much risk at the moment to have a nuclear power source going up and down the atmosphere over and over.
Burning fuel to generate electricity to generate that fuel.. just wasting energy for the inefficiencies of the process, also makes no sense.
when upthread we have this:
The solar I see on this planet requires quite a bit of 'structure' relative to the panels themselves. Will Mars really be that different?
Quote from: dglow on 05/15/2018 02:58 pmThe solar I see on this planet requires quite a bit of 'structure' relative to the panels themselves. Will Mars really be that different?it doesn't need much, certainly not as much as on earth. most of the support structure on earth is to keep the panels from blowing away, as well as adjust the panels to an adequate angle. you don't have to worry about them blowing away on Mars, so they only need something as simple as a kickstand. if there's any worry about them moving, staking them down would be sufficient.
Kilopower still needs a deployable radiator to dump heat.
Quote from: Robotbeat on 05/16/2018 03:12 amKilopower still needs a deployable radiator to dump heat.I believe the thinking was that on Mars your problem is getting too cold not too hot.
Just sat through a kilopower presentation by Dave Poston and it was pretty impressive. The fission is a low enough level that it could still be producing power in 200 years. The main thing limiting lifespan should be the Stirlings and they're making those easily replaceable. Testing is pretty well along and the main thing to do is wade throught the paperwork/permit maze.
2. I've read comments, elsewhere, to the effect "a Kilopower will never produce X" or "you'd need too many Kilopowers" to produce X... but what is X? We don't necessarily need 500kWe, do we? What do we need for ISRU propellant production for a single BFS? Assume that task, alone. Is the 200kWe cited in the 'eBay' thread sound?