put it in a car
Like this? https://en.wikipedia.org/wiki/Ford_Nucleon
Also, you need more than a few kilowatts to power a car. 10kW = 13.4 hp. It may work, but you won't break speed records...
NASA to test prototype Kilopower nuclear reactor
101–110 of 116 posts
Re: NASA to test prototype Kilopower nuclear reactor
#102Earlier quoted context omitted.
The problem with Stirling engines is they have moving parts. It's highly unlikely a Stirling cycle generator on the Voyagers would have operated for 40+ years as their RTGs have.
Yup, I wonder how they can guarantee the engine will keep turning for 10 years even. Maybe if everything is sealed in a (very long) lived lubricant that stands the harshness of space? Still hard to imagine
Sounds like there is some redundancy. These are intended for manned missions so occasionally replacing parts might be part of maintenance.
Re: NASA to test prototype Kilopower nuclear reactor
#103Earlier quoted context omitted.
For anyone else wondering why Pu-238 is dwindling, from the linked wikipedia: “The United States stopped producing bulk Pu-238 with the closure of the Savannah River Site reactors in 1988.[12][13][14] Since 1993, all of the Pu-238 used in American spacecraft has been purchased from Russia. In total, 16.5 kilograms (36 lb) has been purchased but Russia is no longer producing Pu-238 and their own supply is reportedly r…
When I lived in Seattle I was sitting at a cafe one day and a government motorcade came down the street with an 18 wheel truck carrying a dumbell-shaped canister with a giant yellow nuclear symbol on the side. I've never been able to figure out what they were transporting. Does anybody here know what it might have been? It was post 9/11 so I was surprised they were still moving radioactive material on the surface str…
An RH-72B[1] cask is a container for shipping trans-uranic nuclear waste, probably to the WIPP site.
[1] http://www.wipp.energy.gov/WIPPCommunityRelations/images/pho...
Re: NASA to test prototype Kilopower nuclear reactor
#104Earlier quoted context omitted.
When I lived in Seattle I was sitting at a cafe one day and a government motorcade came down the street with an 18 wheel truck carrying a dumbell-shaped canister with a giant yellow nuclear symbol on the side. I've never been able to figure out what they were transporting. Does anybody here know what it might have been? It was post 9/11 so I was surprised they were still moving radioactive material on the surface str…
An RH-72B[1] cask is a container for shipping trans-uranic nuclear waste, probably to the WIPP site. [1] http://www.wipp.energy.gov/WIPPCommunityRelations/images/pho...
That's the one! I can finally put that mystery to rest. :)
Re: NASA to test prototype Kilopower nuclear reactor
#105Earlier quoted context omitted.
Inverse square law. Every n AU you go out from the earth you will need n 2 are of mirror to focus on a solar panel to get the same power. That assumes you can even build a structure that can keep that shape. Say you have a mission to Uranus, you will need a mirror with 400 times the area of the solar cells to get as much power as they would in earth orbit.
Hm, ok the mirror is probably out of the question then. But if you use a laser? I imagine it will be easier to focus it more precisely?
Lasers are still subject to the diffraction limit, regardless of the quality of focus.
We can examine this limit in the context of delivering energy to a remote object. This analysis will be simple - we assume that the optics are perfectly aligned (dubious - pointing is difficult); we assume nothing about the absorption properties of the object, which will necessarily need to be very high efficiency. The angular size T of a laser beam of wavelength L emitted by an aperture of diameter D_a is roughly L/D_a. Similarly, using the small angle approximation, this angular size T at the object itself will be the width of the beam, W, divided by the distance between the object and the aperture, D_o: T = W/D_o. Ultimately, this gives us the width: W = L*(D_o/D_a).
What does this tell us about the practicality of such a system? Visible light, wavelength roughly 500 nm, is perhaps a solid guess for a real system. Realistically the aperture size is probably limited to about 10 meters, but we can go even further and assume a synthesized aperture of a realistic system being 100 meters. You would want to get all of your beam for power transmission, so lets assume an upper limit for the beam width at the object to be 100 meters as well - probably unrealistic, but maybe solar sail/ultralight absorbers could get there. Throwing these numbers in gives a maximum range of... 2x10^10 meters. This is roughly a tenth of an AU. In comparison, this is about 50 Earth-Moon distances... and only a quarter of the distance between Earth and Mars at their closest approach. Coincidentally, this is also about one light-minute.
Any real power delivery system, using current tech and without assuming convenient fictions, will have a much more limited range. In short, lasers are not really perfect rays, even though they are approximately so over scales we typically encounter; at astronomical scale, diffraction always wins. This is why it is usually way better to bring the power with you - especially as you lose solar irradiance as you get further from the Sun. And for bringing power with you, nothing beats nuclear for energy density.
Re: NASA to test prototype Kilopower nuclear reactor
#106Earlier quoted context omitted.
They used to get protests back when Galileo launched, but I don't recall any for Curiosity. There's the soothing effect over time of a known technology not screwing up. Kilopower is safer, because it would launch inert, and it avoids Pu so any failures would be less toxic. Downplaying the usefulness of a technology because of imaginary protesters isn't very helpful.
I don't think New Horizons received any protestors either.
It did: https://www.space.com/1929-nasa-pluto-mission-draws-dozen-pr...
(Not many, but more than zero.)
Re: NASA to test prototype Kilopower nuclear reactor
#107Earlier quoted context omitted.
Inverse square law. Every n AU you go out from the earth you will need n 2 are of mirror to focus on a solar panel to get the same power. That assumes you can even build a structure that can keep that shape. Say you have a mission to Uranus, you will need a mirror with 400 times the area of the solar cells to get as much power as they would in earth orbit.
Does this mean that if you go towards the sun, you would be able to generate more solar electricity with less surface area? I'm not thinking dyson sphere style, but perhaps some sort of electricity space-tanker, that sails toward (or around?) the sun, collecting solar energy, and then returns to earth with batteries packed to the brim with energy? Dibs on Solar Harvester
Take a look at the solar panels on the Parker Solar Probe: http://parkersolarprobe.jhuapl.edu/index.php#spacecraft
Re: NASA to test prototype Kilopower nuclear reactor
#108Earlier quoted context omitted.
The problem with Stirling engines is they have moving parts. It's highly unlikely a Stirling cycle generator on the Voyagers would have operated for 40+ years as their RTGs have.
Yup, I wonder how they can guarantee the engine will keep turning for 10 years even. Maybe if everything is sealed in a (very long) lived lubricant that stands the harshness of space? Still hard to imagine
There is a Stirling engine design which only has a piston as the single moving part, called a "lamina flow Stirling engine".
Note that while implementations usually show a crank and rod with a flywheel, it could just as easily use a magnet and coil to generate electricity.
That get's you down to a single part.
Then you have this:
https://en.wikipedia.org/wiki/Thermoacoustic_heat_engine
...that gets you down to something that can generate sound from a heat differential, and you could couple that sound to some kind of transducer to generate electricity. Still a moving part, though.
You probably can't get zero moving parts and yet have it do useful work, but you can get really close I think.
Re: NASA to test prototype Kilopower nuclear reactor
#109Earlier quoted context omitted.
"over 20 years, a three-megawatt wind turbine can deliver 80 times more energy than is used in its production and maintenance." [0] Beyond that, Steel is 100% recyclable^, and that accounts for over 65% of US steel production. Recycled steel can be done in arc furnaces, requiring no coal coke. [1] Info like this is at the tip of your fingers. [0] https://www.worldsteel.org/en/dam/jcr:f07b864c-908e-4229-9f9... [1] htt…
Okay! Downvote me if you like but our fuel mix in this country is still ~40% combustion and the calculations on wind power say that at current power requirements civilization will harvest enough energy from the air currents to change the climate again. Maybe it stops hurricanes, I have no idea. Also, steel, like atomic fuel, is toxic to produce and reprocess! I know it is much-despised by but I am curious as to the l…
> the calculations on wind power say that at current power requirements civilization will harvest enough energy from the air currents to change the climate again
?
Wind doesn't circulate through the atmosphere forever with perfect efficiency, it eventually dumps its energy into the ground via friction.
There's no difference between slowing wind down with a wind turbine and slowing it down with a tree, they both end up as heat eventually.
Re: NASA to test prototype Kilopower nuclear reactor
#110Earlier quoted context omitted.
Hm, ok the mirror is probably out of the question then. But if you use a laser? I imagine it will be easier to focus it more precisely?
Lasers are still subject to the diffraction limit, regardless of the quality of focus. We can examine this limit in the context of delivering energy to a remote object. This analysis will be simple - we assume that the optics are perfectly aligned (dubious - pointing is difficult); we assume nothing about the absorption properties of the object, which will necessarily need to be very high efficiency. The angular size…
Thanks!
(also memorys of phsyik lectures are coming up again)
And forgive a nonserious reply:
"And for bringing power with you, nothing beats nuclear for energy density"
I think fusion does ...