81–90 of 138 posts
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The Blackwater one always mystified me. It’s like they set out to be villains.
It was founded in North Carolina. The large number of freshwater waterways around there are generally known as black water.
I find it frustrating NASA talking about putting people on Mars but if you look at reality, it can't even put astronauts in the orbit anymore. What about solving that problem first, and when it's done, then we can dream about Mars... Or are we going to outsource such mundane tasks like manned orbital space flight to the Russians and Chinese forever, while we are proudly preparing the colonization of Mars? /s
> it can’t even put astronauts in orbit anymore But this isn’t really a NASA problem, this is a US government funding problem right? I can’t imagine how anyone can put people in space without the budget for it
IMO all that sandbox research they are doing now is useless, because they ain't gonna need it: they ain't gonna need it if they are not going, and they ain't gonna need it if and when they are really preparing to go because everything is gonna be different and nobody will give a shit about how such a power device might have looked like 10 years ago.
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It's not really a concern. U235 is basically radiologically inert, it doesn't become significantly radioactive until after the reactor has been running for a while. The concern with fission reactors in space is for stuff that might return to Earth after it's been in operation long enough to build up other isotopes that are radioactive and subsequently burning up in the atmosphere. For a vehicle that is on a one-way t…
> the reactor can just be jettisoned before re-entering Earth‘s gravity well I think if there’s one thing to be learned from previous missions, it’s that nothing will „just work“. If the ejection mechanism is damaged, or the spacecraft is hit by some object and rendered useless shortly before ejection, then the radioactive payload will make it to Earth. I think a roundtrip would be dangerous, and the core should be l…
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Please provide a citation for this claim. Chernobyl still is a massive cost factor for plenty of countries ( all that are helping out financially with building the new mantle ). Also look at the large effects of Fukushima. Every time nuclear power comes up here on HN, there are some fierce defenders. No matter how 'safe' newer generation plants are and how much it was the oprators fault, the potential for disaster is…
http://www.unscear.org/docs/reports/2008/11-80076_Report_200... Now please provide citations for your claims. Specifically 'Massive Costs' and 'large effects'. Nuclear power does not need to be safe, only saver than the alternatives, this includes long term pollution from solar panel waste. Every ounce of nuclear waste is entirely contained, every other power source's waste is dumped into the environment.
That's a little disingenuous, though, isn't it? It's only contained because no one will allow it to be dumped ("stored") near them. Actually, the fact that we have to take special precautions with nuclear waste due to its toxicity is a disadvantage of nuclear power vs. fossil fuels (for example).
Obviously, there is a much different calculus when thinking about Mars though.
As far as I understand it they are pumping the equivalent thermal energy as an actual operating core would produce into the reactor casing and assembly using a specially designed electrical insert that uses external power. This isn't a fission test. It's a mechanical engineering test. Still cool.
From my understanding the fission part is "easy", the hard part is taking the heat and converting to electricity efficiently and reliably. The Mars Curiosity rover among other probes use a thermocouple based generators to create electricity from the fission heat[1]. Extremely robust , no moving parts, but extremely inefficient just a few percent converted to electricity the rest to heat. The heat is very useful on ma…
As far as I understand it they are pumping the equivalent thermal energy as an actual operating core would produce into the reactor casing and assembly using a specially designed electrical insert that uses external power. This isn't a fission test. It's a mechanical engineering test. Still cool.
From my understanding the fission part is "easy", the hard part is taking the heat and converting to electricity efficiently and reliably. The Mars Curiosity rover among other probes use a thermocouple based generators to create electricity from the fission heat[1]. Extremely robust , no moving parts, but extremely inefficient just a few percent converted to electricity the rest to heat. The heat is very useful on ma…
The maximum what you can get can't be higher than the hypothetical ideal quantum diode made from a material pair.
There are much more down to earth alternatives that beat both stirlings and thermocouples on reliability and specific power density: thermionic converters, thermoaccoustic generators, AMTEC converters, radiophotovoltaic (works only in 0g)
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> the reactor can just be jettisoned before re-entering Earth‘s gravity well I think if there’s one thing to be learned from previous missions, it’s that nothing will „just work“. If the ejection mechanism is damaged, or the spacecraft is hit by some object and rendered useless shortly before ejection, then the radioactive payload will make it to Earth. I think a roundtrip would be dangerous, and the core should be l…
Triple redundancy usually works really well. Fail safes are great too.
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From my understanding the fission part is "easy", the hard part is taking the heat and converting to electricity efficiently and reliably. The Mars Curiosity rover among other probes use a thermocouple based generators to create electricity from the fission heat[1]. Extremely robust , no moving parts, but extremely inefficient just a few percent converted to electricity the rest to heat. The heat is very useful on ma…
In fact the fission[1] part in such small scale is hard. Curiosity and other probes using thermonuclear batteries harness alpha decay[2], which is relatively easy as it happens whether or not you want it to happen, but creates also much less power. In that case the hard part is to obtain material with appropriate half-life and other properties. Perhaps best material for this is Pu-238, which is far more expensive to…
"Thermonuclear" usually refers to the sorts of fusion reactions found in stars and modern nuclear warheads.
[1]: https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge...
I find it frustrating NASA talking about putting people on Mars but if you look at reality, it can't even put astronauts in the orbit anymore. What about solving that problem first, and when it's done, then we can dream about Mars... Or are we going to outsource such mundane tasks like manned orbital space flight to the Russians and Chinese forever, while we are proudly preparing the colonization of Mars? /s
[1] - https://en.wikipedia.org/wiki/Commercial_Crew_Development#Fl...
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The political fallout will probably be more dangerous than adding another kilowatt-class nuclear reactor to decaying megawatt-class ones on sunken submarines.
This actually happened in the past. A Russian radar satellite failed to eject its nuclear reactor to a safe parking orbit and fell in Canada instead. https://en.wikipedia.org/wiki/Kosmos_954