<i>"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><p>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.<p><a href="https://upload.wikimedia.org/wikipedia/commons/1/1e/Premier_model_Easy_Bake_oven.jpg" rel="nofollow">https://upload.wikimedia.org/wikipedia/commons/1/1e/Premier_...</a><p>Though there was a 2006 redesign that apparently didn't go well: <a href="https://www.cpsc.gov/Recalls/2007/new-easy-bake-oven-recall-following-partial-finger-amputation-consumers-urged-to-return" rel="nofollow">https://www.cpsc.gov/Recalls/2007/new-easy-bake-oven-recall-...</a>
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.<p>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.<p>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 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.<p>Here's one of the reports, from 1969: <a href="https://core.ac.uk/download/pdf/85241637.pdf" rel="nofollow">https://core.ac.uk/download/pdf/85241637.pdf</a><p>Some highlights from this report:<p>- 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.<p>- 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.<p>- 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.<p>- 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.<p>Other details that I recall from other reports -- sadly not ready to hand:<p>- 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.<p>- The optimal core fuel temperature would have been <i>even higher</i> except that it was difficult to find materials that would be adequately transparent to even shorter ultraviolet radiation.<p>- 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.<p>- 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.<p>[1] <a href="https://www.world-nuclear.org/information-library/current-and-future-generation/thorium.aspx" rel="nofollow">https://www.world-nuclear.org/information-library/current-an...</a>
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.<p>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.<p>Thrust in meganewtons, and 1000+ ISP
Oh, I thought a <i>real</i> nuclear lightbulb. The New York Central Railroad once developed one.[1], at 8:20.<p>[1] <a href="https://archive.org/details/0221_Big_Train_The_00_25_39_00" rel="nofollow">https://archive.org/details/0221_Big_Train_The_00_25_39_00</a>
In case you can't see the original link: <a href="https://web.archive.org/web/20210130190443/https://beyondnerva.com/2020/03/21/the-nuclear-lightbulb-a-brief-introduction/" rel="nofollow">https://web.archive.org/web/20210130190443/https://beyondner...</a>