151–160 of 187 posts
For anyone who wants a refresher on the UNS nuclear thermal rocket propulsion program from the '60s, here's the final report. It's a very good read: https://ntrs.nasa.gov/api/citations/19920005899/downloads/19... For this new initiative, I can see 2 big differences. On one hand they will use medium enriched uranium (up to 20%), while the original program used highly enriched one (85%), so it's going to be more challe…
Why are they nerfing the uranium like that?
For anyone who wants a refresher on the UNS nuclear thermal rocket propulsion program from the '60s, here's the final report. It's a very good read: https://ntrs.nasa.gov/api/citations/19920005899/downloads/19... For this new initiative, I can see 2 big differences. On one hand they will use medium enriched uranium (up to 20%), while the original program used highly enriched one (85%), so it's going to be more challe…
> During this cool-down period, you will use the same coolant (hydrogen) as during normal operation, but you won't get the same exhaust velocity. That seems like a waste of propellant. Once the reactor has cooled enough that you won't get the desired exhaust velocity, couldn't you allow it to finish cooling down by radiative cooling?
Aw man, forget all that noise. Bring back "Project Orion"*, baby! If we're not gettin' out our (NASA-approved) Huarache sandals, "waxing down" our pusher plate, and surfing "the pocket" of those sweet nuclear detonations in the near future, then, I'm afraid our species is utterly consigned to the category of "posers"!! See, Kilgore knew how to put this kind of (heavier) ordnance to good use: https://youtu.be/8XJYnKhI…
I loved hearing this called “the Devil’s pogo stick” once. There were some paper studies showing that a thermonuclear version could theoretically work and reach speeds up to 10% the speed of light, which would be the Centauri system in a bit over 45 years. Of course you would have to slow down too which probably adds another few years. If this can be theoretically done with technology contemporary with the Summer of…
Not particularly necessary, most of the starshot type plans made seem to be fly-bys.
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Nuclear weapons testing was mostly designed to maximize power output by burning up as much fissile material as possible in one big explosion. Conversely, it was meant to minimize fallout. A broken nuclear reactor (no nuclear explosion) would be the opposite: lots and lots of fallout (broken reactor bits) scattered over a wide area. The radioactivity from a broken nuclear rocket could be more dangerous than that from…
One solution would be have a kill-switch that detonates the reactor fuel as a nuclear bomb (assuming it could be configured in such a way; this is probably more difficult than I imagine). There would be major political problems with this approach though, as you're then shooting nuclear missiles.
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It already happened with Kosmos 954 and will probably happen again soon: ~20 other satellites had been sent in space with the same tech. Kosmos crashed away from (human) life centers but that was a huge stroke of luck. Research area was 100k+ km2. Launches are less to be feared because they are oriented toward sea and the most critical moment are the first minutes. The device discussed is intended to travel away from…
It's crazy to me that people largely consider it safe as long as the unspent fuel or nuclear debris is dumped into the ocean. (Not a direct comment on your opinion specifically, just building of the general idea)
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The propellant is important for its bulk (some mass to shoot out the back) and it's energy. In a chemical rocket, the propellant provides both the bulk and the energy. As it happens, there isn't that much energy in chemical propellants per kg, but the rest of the engine is light enough that these things can fly to orbit. In a nuclear rocket, the energy comes from a nuclear reaction and the gaseous fuel only provides…
Would it be possible to skim the upper atmosphere while in orbit around a planet and top-up the gas reserves?
This might be a good time to review the number of failed rocket launches we've seen in the last few years. Now, imagine them with nuclear materials aboard.
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I remember learning that when they started testing atomic bombs (I think?) the nuclear debris in the air spread basically throughout the whole united states and the government tried to keep quiet about it. Something similar will probably happen here if they mess up with the launch. Btw, the video I saw was on Veritasium.
The thing to remember about that is that we can measure tiny amounts of radiation very cheaply, and tiny amounts are harmless. In fact we are bathed in a constant, but tiny, background level of radiation all the time. Thousands of nuclear weapons were tested all across the world, in the United States, in the Soviet Union, on Pacific Islands, etc, etc. The radiation from that certainly caused a small uptick in the bac…
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"Meh" is a casual response that means "this does not matter much". I don't know that it's proper English by any means, but it is certainly a common colloquialism. A cursory search suggests that it's imported from yiddish. [1] https://en.wikipedia.org/wiki/Meh
I have never seen it used outside of Hacker News.
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The people making these aren't any good at building houses. The lack of housing is, IMO, a failure of government — material costs for homes are surprisingly low compared to everything else — but even then, housing policy is a different department to the space stuff.
>The lack of housing is, IMO, a failure of government Lack of housing is a "feature", not a bug, as it enriches the housing owning class and makes it more difficult for "undesirable" people to move in with NIMBYs.