111–120 of 164 posts
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Sure it's not in critical mass or particularly radioactive, but Plutonium is toxic...
NASA's Kilopower design uses enriched uranium fuel, and with such a small reactor it won't be much uranium.
I looked into some numbers on this, comparing theoretical costs of nuclear power with a solar PV solution on Mars. Kilopower (NASA's research project for a Martian nuclear fission reactor, from the article): 7,200 kg for 40 kW. [1] ISS solar arrays: 14,515 kg for ~100 kW in Earth orbit. [2] If we assume 40-50% Earth solar insolation on Martian surface, the ISS PV array probably isn't far off 40 kW output on Mars Conc…
You should use Ultraflex or similar as a standard. Instead of the ~7W/kg you used for ISS arrays at Earth orbit, you'll get ~150W/kg at Earth orbit:
https://www.orbitalatk.com/space-systems/space-components/so...
We have commercial satellites that also use much cheaper arrays with much higher efficiency.
Using 30 year old solar tech with a very mass-inefficient design is putting your thumb on the scale of such a comparison.
I like kilopower and am a fan (it really helps for super deep space missions that currently have to rely on the tiny amount of Plutonium-238 we have and can make), but we're going to use a LOT of solar power on Mars just as we do today.
Before we can consider seeding terrestrial stations on Mars, we should consider seeding a communications net around Mars. Once we have a half dozen satellites circling Mars, we can start stable comms from the surface to orbit to Earth. It may take 10-20 minutes (for a signal to be received), but the communication is the essential piece here. I'd also consider putting satellites in Earth and Mars lagrange L3, L4, and…
> Before we can consider seeding terrestrial stations on Mars, we should consider seeding a communications net around Mars. We already do. > Once we have a half dozen satellites circling Mars... We already have half a dozen active satellites circling Mars: https://en.wikipedia.org/wiki/2001_Mars_Odyssey https://en.wikipedia.org/wiki/Mars_Express https://en.wikipedia.org/wiki/Mars_Reconnaissance_Orbiter https://en.wik…
>Data rates up to 1 Mbit/s
That's a bit of a problem. It only seems to be a relay for other spacecraft and small surface craft. Much more data will need to be exchanged between Earth/Mars when humans are involved (weather, video, entertainment, collected data, software, etc.)
You'd probably want several brand new satellites dedicated to communications for an initial colonial undertaking.
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> Before we can consider seeding terrestrial stations on Mars, we should consider seeding a communications net around Mars. We already do. > Once we have a half dozen satellites circling Mars... We already have half a dozen active satellites circling Mars: https://en.wikipedia.org/wiki/2001_Mars_Odyssey https://en.wikipedia.org/wiki/Mars_Express https://en.wikipedia.org/wiki/Mars_Reconnaissance_Orbiter https://en.wik…
> https://en.wikipedia.org/wiki/Electra_(radio) >Data rates up to 1 Mbit/s That's a bit of a problem. It only seems to be a relay for other spacecraft and small surface craft. Much more data will need to be exchanged between Earth/Mars when humans are involved (weather, video, entertainment, collected data, software, etc.) You'd probably want several brand new satellites dedicated to communications for an initial col…
But indeed, NASA intends much higher bandwidth for future missions using laser communications.
SpaceX would likely use a variant of their constellation satellites which should be capable of multiple Gbit/s using laser communications.
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There are some "human factor" problems that engineers cannot and should not be expected to resolve. I mean, how can someone design a communist-proof nuclear reactor?
Make them pay to get in?
Not a bad idea though.
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Enriched uranium has a very high energy density. 20% enriched Uranium would contain 16TJ/kg. So a 4MW u-battery would use around 8kg fuel per year.
>Enriched uranium has a very high energy density. 20% enriched Uranium would countain 16TJ/kg. I did not count in burnup ratio. A simple thermal neutron reactor can only use <1% of fission energy in its fuel.
Burnup could still be limited due to fission products poisoning the reaction.
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The important part of mars colonization is being able to produce 100% of all needed goods (from food to CPU's) on the surface of mars, not covering the planet with people. Really 2-3 redundant geosynchronous satellites on mars should be plenty for a very long time. Musk wants satellite internet as it lets Space X lower cost per launch by launching a lot of satellites.
> on the surface of mars Why? Wouldn't it be easier to bootstrap by mining asteroids, and manufacturing in micro gravity, then dropping nearly finished goods onto the planet? That'd also allow you to use the same bootstrapping infrastructure for several surface sites.
Also, a Mars colony would require millions of tonnes of raw materials. You can only get that in-situ.
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Very unlikely that we could do anything on Earth that would make Mars look like a better place to live.
"Very unlikely that we could do anything on Earth that would make Mars look like a better place to live. " Humanity: Hold my beer....
Even if the biosphere were to go to hell, it would still have an atmosphere, and a magnetic field. Fantasists have wildly impractical ideas for fixing the former on Mars, but nothing for the latter.
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>The build cost of the ISS arrays was around $300 million (space PV is way more expensive than terrestrial). That was 20 years ago, on a government contract, for panels that must survive the rigors of actual space. Panel manufacturing costs have dropped almost 10x since then, and the environment (assumed under the protection of martian atmosphere) which they will operate will be far less extreme than Earth orbit, nec…
Space applications use single crystal GaAs (Gallium arsenide) process instead of wide spread c-Si (Crystalline silicon, currently usually multi-Si), due to their superior performance and weight. Process of producing c-Si panels has become a lot cheaper but this doesn't apply to GaAs process.
https://www.nasa.gov/mission_pages/station/structure/element...
Space applications are now mostly using triple-junction cells with GaAs as one of the layers. Spectrolab, Azur Space, and SolAero's product lines are dominated by triple-junction cells. Azur Space also still sells space-qualified silicon cells (lower efficiency and much lower radiation tolerance, but cheaper):
http://www.azurspace.com/images/pdfs/0002162-00-03_DB_SIA.pd...
The Martian radiation environment is mild enough that crystalline silicon might still be competitive if you needed large stationary arrays. But on the Martian surface, where you can't rely on near-constant sunlight, nuclear is going to be tough to beat. (Orbiters are a much better match with solar.)
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If we could terraform a planet as barren as Mars, wouldn't fixing earth be significantly easier?
Yes, it would be.