![]() ![]() This way, heat gradient will naturally move heat to the radiators. The simple solution to this is to keep radiator temperature lower than reactor temperature. This is typical so if you have a design that creates a different direction (for example your fusion is being conducted in you radiator) then you need to give details and not wave hands. The water that cools this has a lower heat density. This is to say in a typical powerplant design the steam in the reactor has the highest energy density, once it transfer via heat exchanger to the turbine water the steam temperature and pressure fall some, then over the turbine it looses more energy density per mole of water. 'Fuel' in the context of nuclear thermal rocket would be the slug of U235 in the reactor itself.īut it cost energy to move heat up a heat gradient instead of away from it. Then, once the reactor temperature is the same as the radiator's, the heat engine stops generating power, and the reactor stops cooling.Īlso, when you wrote 'fuel', you might meant 'propellant' - that's the stuff spewing out of the rocket nozzle. Should a heat engine (thermocouple) be plugged in at this state, the reactor would get cold fast, because while heat flows through the heat engine, the reactor isn't producing additional heat to compensate. ![]() If a NTR is powered down post-burn, it can be left still hot - the heat will radiate on its own, given enough time - without the crew needing to worry about deadly radiation, as long as the reactor components can withstand the temperature. If the reactor is powered down, it doesn't emit as much deadly radiation as it does under full power. Just don't expect such cooling to remotely compare to an open cycle system where transferring the heat to ejected mass is the whole idea. It isn't just the addition of power, just removing the heat is reason enough to do such a thing. Obviously the existence of such a graphene system (or even just a peltier or thermocouple) is likely to be used to extract heat as radiators grow larger and larger. I've suggested that a rather likely system involves ejecting all used fuel after each "burn". Of course, this leaves nasty cooldown issues, you either have to keep ejecting "fuel" (and killing your effective Isp) or somehow deal with cooling a reactor is still radiating plenty of heat/energy. One of the huge advantages of nuclear thermal rockets is that they can do similar cooling tricks as chemical rockets: use the expelled mass for cooling before sending it into the "combustion chamber/reactor" for final heating. The reactor isn't completely turned off, merely kept warm, to provide power to the ship. This is the type of reactor that both propels a ship by being a NTR, while also providing power through a secondary coolant loop. I still think that cooling issues will drive a "always on" solution, cooling a reactor in space is non-trivial and the danger of coolant failure (abandon ship**) outweighs the danger of radiationįor a start, there are things such as bimodal nuclear reactors. Normally I'd assume that lowering the output such the the reactor is "always on" would reduce the danger from radiation (assuming equal shielding), but in practice I'm less sure (ignoring strategies involving sequestering crew in highly shielded areas during a burn). Also I wonder at the idea of powering down a reactor to limit radiation. Simply "leaving it hot" is likely to cause a full meltdown*. ![]() When a NTR (or any nuclear reactor) is "turned off' the nuclear fuel will still be reacting as some of the fuel will be turned into isotopes that are still emitting neutrons and powering the reaction. A closed cycle reactor will have the same cooling system it used when operating after it is turned off, so that shouldn't be an issue. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |