"For those of us of a certain age, there was a toy that was quite popular: the Easy-Bake Oven...Rather than having a more normal resistive heating element as you find in a normal oven, though, a special light bulb was mounted in the oven, and the waste heat from the bulb would heat the oven enough to cook the food."
I can't find any evidence that the Easy Bake oven used a "special" light bulb. It just used 2 normal 100 watt incandescent bulbs as far as I can tell. Tungsten is a normal resistive heating element, pretty common in electric furnaces.
I have this Panasonic toaster oven that has the usual element, plus this super intense bulb. When it fires on it's as bright as the sun, and all the other lights dim slightly in my apartment. I've never had a better toaster oven.
You can buy a Panasonic FlashXpress toaster oven and get the Easy-Bake experience. Great toaster! Fast and very predictable. It starts cooking immediately and every toast cycle is the same duration. In a regular toaster oven it takes a while for the heating element to get hot before it starts to actually toast the bread. If you immediately cook a second batch of toast for the same amount of time it burns.
The one I played with as a kid used oven light bulbs. They look pretty much the same, but solderless construction, and IIRC quartz glass and a slightly more robust filament.
I think you should be able to achieve an Isp approaching that of this rocket with a solid core nuclear reactor, without radiators, although at much lower T/W ratio.
The idea would be to not just dump hydrogen into the reactor to heat it, but gradually warm that hydrogen, extracting as much power as one could along the way. At the end, this power would be used to superheat the hydrogen after it went through the reactor (by some sort of electrical heating), to a temperature greater than the reactor's temperature limit. Alternately, the exhaust stream could be further accelerated by some sort of MHD afterburner.
The observation here is that a nuclear rocket is not energy limited, but rather is entropy limited: the exhaust can only carry away so much entropy. So, the goal is to make the engine as internally efficient as possible, with as little thermodynamic irreversibility as possible.
Things like this make me wonder how cheap a truly commoditized nuclear industry could be. What kind of lifestyle are we giving up by requiring orders of magnitude fewer deaths-per-megawatt-hour of nuclear compared to fossil fuels? What if we were civilized enough you didn't have to worry about anyone building their own atom bomb?
I think we need to be a spacefaring species to be able to fully utilize nuclear energy, and to be a spacefaring species, highly automated orbital manufacturing has to be established. Doing nuclear on the planet Earth at all is perhaps too akin to doing it in the middle of Manhattan island.
>What if we were civilized enough you didn't have to worry about anyone building their own atom bomb?
Then we'd be something other than human. You'd need a species that values all members equally and has no preference for those in the same social group (or family, etc.). Likely it also means members cannot value themselves above other members. Without all that "civilized" simply means that some group gets oppressed and isn't allowed to fight back in any way.
There is a lot of very complex, and very real human psychology and sociology at play in those decisions. A lot of it centers around who accrues the benefits of a given energy source, vs. who pays the consequences.
On the other hand, the consequences have already been paid. There are plenty of highly irradiated places on earth already that could be used for future nuclear projects.
As you are asking open ended questions. What do you think is an appropriate level of deaths per MWh? Can you put a number on it? And how do you engineer a reactor to accurately and repeatedly achieve a certain risk level?
Well, one answer to that is when the lives saved by nuclear balance out the lives cost by fossil fuels. Nuclear currently has a rate of 0.07 deaths per terawatt-hour. Coal has a rate of 24.6 deaths per terawatt-hour. If fully replacing coal with nuclear required making nuclear a hundred times more dangerous than it is now it would still be completely justified.
So imagine a nuclear plant that saves costs by reducing safety margins. You have less redundancy in equipment and staff, less containment, or whatever. How do you accurately predict the risk? And what error would that risk have? Every single factor you are modifying can come together in weird combinations and has an error bar of its own. What happens when there is suicidal engineer + metal fatigue + unusual weather conditions? Ultimately this seems like a fools errand. The belt-and-braces approach is the only way humans have found to safely design complex inherently risky machines. And deviating from that creates Shuttle shaped clouds in the sky and Boeing shaped holes in the ground.
Not that much. Nuclear energy alone wouldn't really make a huge difference. Even if we ignore the obvious problems with safety (big issue with older designs and their spent fuel storage) and security (huge issue with modern designs) when nuclear power would be similarly widespread as, e.g., natural gas: There is still the fact that it is inherently a stationary power source (with not that many good places to put it). Distribution of electricity isn't a big problem, but it doesn't help for mobility applications, so we would need the battery or H2 industry anyways.
Factor in the wastly different levels of difficulty between solar and nuclear power, I'd think we would also have the latter, if just as a simple alternative when you don't have the time or the capital to setup a nuclear power plant. Wind energy might be a different matter, as it comes with a lot more practical difficulties.
One could simply compare France and Germany to understand how things would end up, I think.
I read some of the old United Aircraft Corporation reports about the nuclear light bulb reactor the other weekend. The design parameters are delightfully extreme. You can see why it wasn't tested in later years. By the 1970s there was already much diminished tolerance for experiments that ejected fission products into the environment, and effective release prevention for testing this design would be expensive.
- The fully gaseous core would operate at a pressure of 200 atmospheres. This is somewhat higher than the pressure in a pressurized water reactor core.
- The vapor/plasma fuel temperature would be 42000 Rankine. That's about 23300 Kelvin, roughly 4 times as hot as the surface of the Sun.
- The fiberglass pressure vessel was projected to last about 6000 seconds (100 minutes) of full power operation before its strength was compromised by neutron irradiation.
- The preferred fuel was uranium 233, which does not exist to any considerable degree in nature. It has to be bred from thorium. Since U-233 never had significant use in civil or military nuclear applications, the US has not produced any U-233 since the 1980s [1]. Highly enriched uranium 235 or plutonium 239 would also work, just not as well. All fueling options needed "bomb grade" fuel purity. That was the only way to make the reaction zone so compact.
Other details that I recall from other reports -- sadly not ready to hand:
- Later iterations of the design kept thinning the quartz envelope to maintain adequate transparency to UV radiation after accounting for color centers induced by radiation damage. This required aggressive/optimistic estimates of how perfectly pressure could be equalized on both sides of the envelope, particularly during start-up.
- The optimal core fuel temperature would have been even higher except that it was difficult to find materials that would be adequately transparent to even shorter ultraviolet radiation.
- Fission products were supposed to be separated from the fuel centrifugally before the fuel recirculated into the reaction zone. This seems chemically optimistic to me.
- There was little consideration of chemical factors in any of the reports I read. Given that the environment was extremely hot, rich in fluorine, and would soon contain most elements of the periodic table from fission products, this seems like an oversight. One that would probably be testable only by actually building and operating test reactors.
Just saying that 200 atm + 23,300K alone would push the design feasibility firmly into 22nd century. Modern rocket engines can only handle 3000-4000K on the inside with roughly the same pressures.
They posited a clever solution for the irresistible temperatures. They didn't plan on having any structural material survive contact with with the fuel plasma. The quartz inner wall would be protected by a vortex of neon. Most energy transfer to the hydrogen propellant would be as radiated visible and UV light through the gas boundary and quartz wall. (There would also be some direct heating by neutrons.) The hydrogen propellant on the other side of the wall would be seeded with finely divided tungsten to make it absorb 98% of the radiant energy. The propellant would be much cooler than the plasma fuel, though still blazing hot [1]. The whole concept is in the intriguing fuzzy transition zone that separates AM engineering from FM [2]. It seems more likely to go "boom" than "whoosh" but I Am Not a Nuclear Rocket Scientist.
Keeping all core gasses confined is one option. A spec of dust on the quart, crytaline defect, hydrogen embrittlement, or anything else and you get R.U.D.
Another is not to fight it, and let them go. The closest thing to a torch drive possible with modern day engineering after the NSWR is the open cycle gas core rocket.
Nobody would accept the fallout if it was a space launch either, given that crud might either hang about in LEO poisoning it for everyone else, fall out onto the planet below, or drift around in space forming a radiation hazard for future travel. You'd have to get its speed up to solar escape velocity to ensure it wouldn't be captured somewhere.
This does not follow. Photons from the sun are not radioactive isotopes that can rain down on us as they decay from orbit. And the magnetosphere protects us from the bulk of the solar wind's traces of heavier isotopes. How much plutonium or whatever, is in near-Earth space, other than what we've sent up there? The old Soviet reactor-powered RORSAT series have their cores in orbit still. They'll come down eventually. See https://en.wikipedia.org/wiki/Kosmos_954 which crashed in the Canadian arctic. A cleanup operation was attempted over a wide area, as it survived reentry with pieces intact.
> They were ultimately able to recover twelve large pieces of the satellite, ten of which were radioactive.[1] These pieces displayed radioactivity of up to 1.1 sieverts per hour, yet they only comprised an estimated 1% of the fuel. One fragment had a radiation level of 500 R/h, which "is sufficient to kill a person ... remaining in contact with the piece for a few hours."
A more pragmatic argument is that, after the fission of literal tonnes of plutonium in the atmosphere in the previous century, the small risk of losing a few kg more here or there pales in comparison. Even all those RORSATs barely register in comparison to that.
Use it for the later stages in a many stage interstellar rocket. First stages are chemical, then NERVA style contained nuclear rockets, then open cycle nuclear when you are already well past solar system escape velocity.
I’m thinking of something like an interstellar flyby probe for the Centauri system. It wouldn’t be able to stop or do much course correction but you could send basically an autonomous space telescope that transmitted back observations. It would be able to see planets in the system much better than we can from here.
Not with an isp measured in the thousands of seconds. This is greater than earth escape velocity. Past the earth, it'll diffuse enough to not be a significant issue.
I can't find any evidence that the Easy Bake oven used a "special" light bulb. It just used 2 normal 100 watt incandescent bulbs as far as I can tell. Tungsten is a normal resistive heating element, pretty common in electric furnaces.
https://upload.wikimedia.org/wikipedia/commons/1/1e/Premier_...
Though there was a 2006 redesign that apparently didn't go well: https://www.cpsc.gov/Recalls/2007/new-easy-bake-oven-recall-...