31–40 of 164 posts
Earlier quoted context omitted.
Sure there is uranium on Mars. But extracting and refining it won't be easy.
Probably cheaper to just put the fuel rods on the rocket with the reactor for the foreseeable future...
So a 4MW u-battery would use around 8kg fuel per year.
The fact that we're going to have to use some sort of atomic batteries is one of them. Another is that we can't search the entire planet for life before we go visit. It's impossible to disprove a negative.
My preference would be to see every piece of gear have an integrated solid-state nuclear battery and O2/H2O generator. That way we design one cheap, rugged, relatively low-weight and low-volume piece of gear and then just mass-manufacture it. Also no astronaut would ever be far from water or air, and there becomes a zero chance of death by asphyxiation or dehydration.
Earlier quoted context omitted.
They don't have to build it on Mars. A kilowatt scale nuclear reactor is small and also safer and more portable. The Russians have already sent nuclear powered satellites into space.
Yeah, i used the wrong word there. I meant, "put" instead of "build"
I'm getting kinda sick of the media putting more & more non-sense in our heads instead of actual news. This is pure fantasy. They can't build nuclear reactors on Mars! The only reason why they write this article is because the topic "Mars" generates large amounts of views. News shouldn't be a bussiness :(
Genuine question: If it's possible to use mini nuclear reactors in satellites then why they just can't land that thing somehow on Mars (like they did with Curiosity) and use it on planet surface to power lab?
Earlier quoted context omitted.
> plutonium, which is in very low supply. Thermoisotopic generators are a bad idea for general power generation for a colony for other reasons (they're low power, you need a lot of them), but it's not a problem that they're in low supply. That's just because we haven't been making more plutonium recently, because we haven't needed it. We could simply make more.
Pl-238 is very expensive to produce. We are talking millions/kg.
NASA has also been buying Pu-238 from the Russians at around $1.5 million/kg[3], which would be $7.5 million for Curiosity, or 0.3% of the cost of the program.
I'm interested in deep-space exploration (but am no expert), and as far as I can tell the reason the US is running out of Pu-238 has absolutely nothing to do with cost.
It's been happening because only NASA has really wanted this, but producing it has been the purview of the military or the DOE.
So the issue has been stuck in some bureaucratic nightmare for decades, the only people allowed to produce Pu-238 didn't need it, and NASA couldn't simply spend a crapload of money to pay another agency or branch of the government to restart production due to the way money politics works, even though it was an overall good investment.
So rather than simply restart production at a trivial cost compared to what NASA otherwise spends, it's been easier to buy it from Russia.
As [1] shows there's now a real possibility that Pu-238 will run out, so the US has restarted production.
1. https://www.nasa.gov/pdf/636900main_Howe_Presentation.pdf
2. https://en.wikipedia.org/wiki/Mars_Science_Laboratory
3. http://dailycaller.com/2017/03/28/nasa-wants-to-stop-buying-...
The last time I heard about humanity settling on Mars on behalf of an Aerospace Corporation, it was about opening a gate to hell.
Earlier quoted context omitted.
Probably cheaper to just put the fuel rods on the rocket with the reactor for the foreseeable future...
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.
I did not count in burnup ratio. A simple thermal neutron reactor can only use <1% of fission energy in its fuel.
Earlier quoted context omitted.
Can we start by agreeing on whether or not we care about a nuclear reactor going "pop" on mars pre-colonisation? Because, you know, there's a chunk of me that thinks we can be less risk averse in trying to do things on an uninhabited planet. Nuclear meltdown is pretty awful on earth, on Mars I don't see it with the same fear. I also feel like this is not dissimilar from dumping rubbish in the neighbours yard because…
The concern was never about a nuclear reactor having a failure mode on Mars. It was about the rocket carrying the nuke having a failure mode and spewing radioactive fuel over central Florida.
Now, as soon as you turn the reactor on you start turning the relatively safe U235 into all sorts of nasty things with half lives that are much, much shorter than 700 million years like strontium 90 with a half life of 30 years. That stuff is indeed horrible and getting it spread over Florida would be a disaster. But the solution is to make sure you don't turn the reactor on until it's safely in orbit.
That makes them much safer than the RTGs we've been using to power space probes far away from the sun previously. Because the P238 isn't in a critical mass it has to be a synthetic isotope with a low half life in order to generate enough heat to power a spacecraft when it's outside a reactor and would be quite deadly if you interacted with it without shielding.
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
Conclusions:
Nuclear reactor would have approx. 50% launch weight. SpaceX estimate $45/kg payload with a Falcon Heavy, so about $324K for Kilopower or ~$600K for the ISS arrays.
The build cost of the ISS arrays was around $300 million (space PV is way more expensive than terrestrial). The development and test costs of Kilopower is around $15 million; build cost of final units is unknown.
You would have to automate and/or remotely control all of the nuclear power plant operations. Dust storms would be a challenge to a PV solution, though not insurmountable.
They actually look very comparable. Nuclear has an edge due to it weighing half as much as the equivalent PV generation system. I think there is definitely value to a simpler system that's more decentralized... but that's harder to quantify.
Edit: people noted I forgot to factor in batteries. 40 kW = 480 kWh per 12 hours. 1 Tesla PowerPack = 220 kWh @ 50 kW. Let's assume a worst case that the base needs the same electrical power during the night as it does in the day, so we need around 5 PowerPacks to get us through each night. 1 PowerPack weighs 1,622 kg, 5 = 8,110 kg. Wow, we need another Falcon Heavy trip just to bring us enough batteries for 1 night! Let's not mention those dust storms that can last for a month or so...
Now nuclear looks much better... and that has its own complexities. Colonising Mars is going to be very hard. :)
[1] https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/201600...
[2] https://www.nasa.gov/mission_pages/station/structure/element...
Earlier quoted context omitted.
Yeah, i used the wrong word there. I meant, "put" instead of "build"
Sure they can. That's the whole point! It turns out nuclear reactors scale down surprisingly well.