NASA demos little nuclear power plant

[Jethro_uk]

NASA has announced successful tests of a small fission reactor capable of producing about 10 kilowatts of power, and hopes the technology will prove suitable for use on the Moon or Mars.

The space agency?s developed the reactor because crewed missions will need lots more electricity than can be generated by either the Sun or the radioisotope thermoelectric generators that power the likes of the Voyager probes, New Horizons and the Curiosity rover. Future probes will also be able to do more if they have more power to play with.

Enter ?Kilopower?, a fission reactor with the potential for output of 10 kilowatts.

As described in a 2015 paper (PDF) the device has a small, hollow, Uranium 235 core. The central hole can be occupied by a single control rod. When on, the device creates heat that passes up through ?sodium heat pipes? until it reaches Stirling Engines that turn it into electricity.

NASA on Wednesday announced that a first round of tests - dubbed KRUSTY (Kilopower Reactor Using Stirling Technology) ? have proven a success.

Two test phases ?confirmed that each component of the system behaved as expected.? A third phase ?increased power to heat the core incrementally?. Phase four ?culminated with a 28-hour, full-power test that simulated a mission, including reactor startup, ramp to full power, steady operation and shutdown.?

The reactor is not yet flight-ready and will need lots of testing to get it there, not least because people tend to be nervous about large chunks of fissile material on rockets. There?s also the small matter of vacuum testing.

Overall, however, NASA boffins are chuffed with their progress and therefore the progress Kilopower might enable in space.

[GB]

What does it do for a cold heat sink?

[Jethro_uk]

Presumably the close to absolute zero of space helps ?

[Chris Hogg]

Every home should have one!

(that'll be the day!)

[GB]

As you wrote at 16:53 "No shit Sherlock!" :)

Yes, the low temperature of the surroundings means the spaceship is not receiving much heat from its surroundings. It's still got to radiate the

10kw it's generating, though.

I should have just done the sums rather than post a silly comment.

The energy radiated per square meter is:

sigma x T^4

Where: Sigma is 6 x 10^-8 (Stefan-Boltzmann constant) T is the temperature of the radiating body in Kelvin.

If the heat radiator is a couple of square meters, it needs to be at a temperature of around 550K, which is no problem at all, really, with liquid sodium for heat transfer.

[Tim Streater]

Presumably it only has to radiate *unused* energy. And can't it wind the reactor down when less energy is required?

[Andy Burns]

A stirling engine may be up to 50% efficient, so it has to dump an amount of heat equivalent to the amount it converts, otherwise the cold side warms up and eventually it will grind to a halt.

Yes, or charge some batteries etc.

[Tim Streater]

Ah yes, of course I was overlooking efficiency losses.

I suppose in worst case it has to be able to dump the whole output.

Hmmm, would it need to keep the rad at a constant temperature to avoid thermal cycling?

[Harry Bloomfield]

Tim Streater wrote on 03/05/2018 :

The Stirling needs heat on one side, cool on the other to work, so all of the heat energy put into one side needs to be lost from the other.

[Andy Burns]

Apart from the amount extracted electro-mechanically

[GB]

But that useful energy may well be expended inside the spacecraft. If some of the 10Kw is used to power an onboard computer, say, that amount of energy will have to be radiated as heat into space.

[Brian Gaff]

Hmm, well, who knows, but 10Kw seems not to be very much power. Brian

[Dave Plowman (News)]

Just what's needed for wind power, then? ;-)

[tabbypurr]

for output of 10

ore

full-power test

Are they on Ebay yet?

NT

[newshound]

One of the "illustrative" pictures showed one on the surface of a planet (Mars?), with a large thin round disk mounted horizontally above the main unit, on a stalk. So presenting a reasonably large area with a good view of the "sky".

[newshound]

Ah yes, solar wind power. Ticks all the boxes :-)

[Adam Funk]

There's practically zero convection, though.

[Tim+]

Pretty huge radiator mounted on the top in the picture.

Tim

[newshound]

Radiation does a pretty good job of putting frost on a car under a clear sky when the air temperature is a degree or two. In the great days of Islam, they made ice overnight all through the year in Iraq and Saudi Arabia by constructing large shallow pools which they flooded after sunset.

[newshound]

I meant to add, ISTR the effective temperature of a clear dark sky is typically below -100 C