True, but it will still have uses as insulation surrounding whatever reactor can hold up. I wonder if a working fluid can be passed through asbestos pipes...Some of the work-arounds for NSWRs and put-put Orion pusher plate cooling--advances in heat-shields and what have you might help with reactor designs...it might be something obtuse. Maybe from a field of research unrelated to nuclear power or even aerospace.
So how about a lead cooled design? A big advantage to that is the coolant itself can double as shielding while still being able to run fairly hot. In fact, these were used in the Alfa class for a couple of decades before the class was retired during the breakup of the USSR. It seems to be fairly well known.
Based on my admittedly limited understand, the heat pipe concept seems promising as a solution to the problem. Also I would imagine that the construction material of choice would have some effect on radiator mass.It did seem that several of the posters were missing the rather significant design issue of the rejection of waste heat. Radiators are going to be a significant mass for a space-based reactor power system, regardless of the temperature chosen for rejection of waste heat.
But not impossible? Given that higher tempurature leads to lower radiator size and mass, I would think that the performance advantages would make it a worthwhile endevour.At 1600K, most materials won't work. Refractories -- either ceramics or metals -- will be needed. While people use them all the time, they are not easy to process.
In anycase, according to table 1 in this it would be possible to achieve a radiator temp of ~800K using titanium with potassium as the heat pipe working fluid. In the context of future settlements on the moon (yes, they will happen in the coming few decades one way or another), this would make sense because the relative wealth of titanium in the Lunar Lowlands would reduce the amount of material needing to be imported from elsewhere. While it wont have the performance of that 1600k I mentioned, it should still be more than mass competitive with solar at comparable wattages. The ISS solar trusses by themselves have a mass of 79 metric tons, surely the system mentioned above can beat that.
But the space shuttle was neither. :PEngineering is always "whatever works" and gives the most cost-effective results.
If the Shuttle had been able to meet its requirements, it would have been a much more cost-effective system. There's a system engineering course on the MIT OCW site which studies the Shuttle and its design process, using many of the original engineers as information sources; it's a great way to spend a about 2 dozen hours.
I wonder if this may play a part: http://en.wikipedia.org/wiki/Borazon
"Borazon is used in industrial applications to shape tools, as it can withstand temperatures greater than 2000 °C (3632 °F), much higher than that of a pure diamond at 871 °C (1600 °F)."
In other news...SLS to use F-1 strap-ons:
Perhaps nuclear upper stages can have a smoother ride...
Last edited by publiusr; 2012-Apr-20 at 09:47 PM.