As I see it the only way that a near future mission could operate beyond Saturn is by using Kilopower reactors. Since it appears that there will not be enough RTGs available by the proposed launch date.
Except there are no Kilopower reactors either. All this stuff has to be built, so you have to ask which would be easier to build--RTGs or Kilopower reactors.
As I see it the only way that a near future mission could operate beyond Saturn is by using Kilopower reactors. Since it appears that there will not be enough RTGs available by the proposed launch date.
Except there are no Kilopower reactors either. All this stuff has to be built, so you have to ask which would be easier to build--RTGs or Kilopower reactors.
AIUI the uranium to power the Kilowatt reactor is easier to obtain. It is similar to enriched uranium in the light water reactors used by the USN.
AIUI, the Kilopower project is designed for operation on a planetary body (i.e. in the presence of gravity and a good heat sink). For operation aboard a spacecraft, you'd need a modified reactor (with e.g. much larger radiators).
AIUI, the Kilopower project is designed for operation on a planetary body (i.e. in the presence of gravity and a good heat sink). For operation aboard a spacecraft, you'd need a modified reactor (with e.g. much larger radiators).
Something like that https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20190029259.pdf .
Which itself is reminiscent of JIMO and the SAFE reactor (which appears to have effectively been downsized and turned into Kilopower).
AIUI, the Kilopower project is designed for operation on a planetary body (i.e. in the presence of gravity and a good heat sink). For operation aboard a spacecraft, you'd need a modified reactor (with e.g. much larger radiators).
The idea with Kilopower is multi-mission capability like with MMRTGs. The smaller Kilopower units are definitely targeting deep space missions, and the radiators are sized for both environments (Mars atmosphere is not THAT good of a heatsink without forced convection).
But interestingly, they have to get the Sterling Generators working anyway, so I guess from a technological readiness perspective ASRGs (canceled tho they are) would be on the table. And ASRGs aren’t any heavier Watt-for-Watt than Kilopower and they scale down better.
What might be kind of interesting is if you used an MMRTG to power the instruments for reliability/longevity reasons and the Sterling Generator Kilopower (or even ASRG) for electric propulsion (as I think the main propulsion wouldn’t need more than about 10 years of operating time? The main mission may want to last decades like Voyager, however).
Especially the smaller versions (<10kW) of Kilopower are targeting deep space robotic missions. And some of those smaller concepts of Kilopower had the option of thermoelectric converters instead of Sterling (at the expense of greater weight).
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160012354.pdf
If you managed to solve zero boiloff capability, a small nuclear thermal rocket would be good to have for orbital insertion of Pluto. The lack of a gravity well means you could have a long thrusting period without being penalized by the lack of Oberth Effect.
...but of course, likely no planetary mission could afford that.
Even still, it’d be interesting to see some Kilopower-sized reactor (~40kW thermal) be used for a really low-thrust nuclear thermal rocket for deep space missions. Instead of sodium coolant, you use hydrogen and dispense with the heavy generators and radiators...
BTW, just doing some back of the envelope calculations, and...
A Falcon Heavy expendable based on SpaceX’s figures to Mars (16.8tonnes to probably 6.9km^2/s^2) should get 19.23t to Earth escape velocity.
13.22 tons of solid kick motor should get the 76km2/s2 for 5.76t to Jupiter flyby. Do a fairly close pass and a 2km/s Oberth Burn there, and I think you can get about 2.7t on a flyby trajectory to Pluto on about the same speed as New Horizons.
About 700kg of Xenon propellant and a 7kW NEXT and Kilopower-based NEP stage should slow down a ~575kg payload to orbit around Pluto in 5 years, comparable to New Horizons.
So flight time about 50% longer (~15 years instead of 10), using a Falcon Heavy Expendable, like a couple IUSes worth of solids, and a Kilopower/NEXT NEP stage to get New Horizons into Pluto orbit instead of flyby. All rough calculations, but I think conservative enough.
Only requires about 5years of operating time for Kilopower and the NEXT thruster, which should be relatively straightforward to qualify (700kg of Xenon at 47km/s is about 33MN*s of impulse... the NEXT Long Duration Test demonstrated 918kg of Xenon throughput and 35.5MN*s of total impulse, so this should be feasible). The Sterling Generators were designed for 17 years of life and demonstrated over 33,000 hours in the lab, but spread over multiple units... but still ~5 years operating life should be easier to qualify for than the design goal of 17 years.
As far as outer solar system targets, I would love to see a mission to Sedna as it approaches it's perihelion of 76 AU, which would be in reach within a 20-25 year travel time. The best opportunities for that with a Jupiter gravity assist would be a launch in 2033 or 2046.
I've seen a different Persephone paper that seems more compact. It involved 3 imager drop probes, NEP, but suffered from data relay bottlenecks. Apparently part of an Iowa State University study.