Space Nuclear Power

[tater]

https://beyondnerva.wordpress.com/2018/05/02/krusty-we-have-fission-kilopower-part-iii/

Kilopower test worked.

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After an initial proof of concept fission test (DUFF), KRUSTY was designed and built by NASA (at the Glenn Research Center in Cleveland), and the Department of Energy (Y12 in Tennessee fabricated the core, and Los Alamos was the lead design site), and just last month completed fission powered testing at the National Nuclear Security Site (NNSS) in Nevada.

Full power critical test in March.

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This highly successful test shows that KRUSTY performed exactly as expected, and that Kilopower is ready for the next step in its’ development: the construction of a flight article for the first new astronuclear reactor design in the US for close to 50 years.

 

[Racescort666]

I listened to the press conference and they said that they don't think they need to do any more ground tests. The likely next test would be a flight test.

[tater]

15 minutes ago, Racescort666 said:

I listened to the press conference and they said that they don't think they need to do any more ground tests. The likely next test would be a flight test.

Yep, that's sort of the last quote I put in there, that they are ready for a flight article test.

This is awesome.

[sevenperforce]

57 minutes ago, tater said:

Yep, that's sort of the last quote I put in there, that they are ready for a flight article test.

This is awesome.

Ridiculously so.

[HebaruSan]

3 hours ago, tater said:

https://beyondnerva.wordpress.com/2018/05/02/krusty-we-have-fission-kilopower-part-iii/

This is the most comprehensive, in-depth blog post I have ever seen. I was casually wondering what we need this for, and the post goes into several specific missions where it could be used and the pros and cons of using it. Very impressive.

[Brotoro]

Fun stuff!

[Gargamel]

Ya know, I appreciate the humor, but sometimes rocket scientists just need to be locked in a room and let them work without any out side access to pop-culture. 

 

Very interesting stuff. 

 

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Eight hours in, they started playing with things

Those are words I never want to see associated with a nuclear reactor.  We've been there, done that, so sorry Northern Ukraine.  But I understand they were (HOPEFULLY) staying within safety limits.

 

Oh god... the more I read, the scarier it gets... 

Edited May 3, 2018 by Gargamel

[Racescort666]

Does anyone have any numbers on how the power density of Kilopower compares to RTGs and Solar Panels?

[StrandedonEarth]

Hard to say at this point. It’s supposed to generate 10 kW, but the mass of it won’t be known until they build a flight article, and even then, the mass will likely change on future versions depending on lessons learned. 

The Voyager RTGs: 

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each RTG had a total weight of 37.7 kg including about 4.5 kg of Pu-238.^[2] It uses 24 pressed plutonium-238 oxide spheres and provides enough heat to generate approximately 157 watts of electrical power initially - halving every 87.7 years

Future RTG's were expected to use a Stirling cycle generator instead of thermocouples,  while there was development work done I'm not sure if any SC-RTGs are currently under development.

The more modern RTG for Curiosity:

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The MMRTG is designed to produce 125 W electrical power at the start of mission, falling to about 100 W after 14 years.^[6] With a mass of 45 kg^[7] the MMRTG provides about 2.8 W/kg of electrical power at beginning of life.

 

Edited May 6, 2018 by StrandedonEarth

[Nuke]

the iss can generate 120kw from its solar array so thats not much of a boost unless you can make the reactor lighter than that solar array and support hardware. at least not in the inner solar system. outer solar system is a whole other can of worms. if it lets us build a multipurpose long haul nuclear-electric survey ship that can visit multiple locations then its a huge improvement. 

[tater]

Looks like a 1kW reactor is around 620 kg all in.

[KSK]

17 hours ago, Nuke said:

the iss can generate 120kw from its solar array so thats not much of a boost unless you can make the reactor lighter than that solar array and support hardware. at least not in the inner solar system. outer solar system is a whole other can of worms. if it lets us build a multipurpose long haul nuclear-electric survey ship that can visit multiple locations then its a huge improvement. 

Quick bit of searching gets me approximately 16 tons per solar array for the ISS which presumably includes the Integrated Truss section and rotating joint needed to point the thing. For comparison the spacer sections of the Integrated Truss weigh in at approximately 2 tons each. So call it 14 tons per solar array and joint.

So - back of an envelope calculation, that's 2.1 tons per kW for ISS solar arrays compared to 620kg per kW for KRUSTY.

So, very roughly, KRUSTY has three times the power density, unless my arithmetic has gone askew somewhere. On the other hand, using those same numbers and assuming that a scaled up version of KRUSTY can be built and that it's power output scales linearly with it's mass (omigosh, my hands are sore with all this waving), you would need a 74 ton reactor to equal the ISS output. 

That's a lot of fissile material to strap on top of a rocket...

 

Edit: I expect you could design a lighter version of the ISS arrays these days but even so I think KRUSTY would still have the edge in terms of power density.

Edited May 7, 2018 by KSK

[RCgothic]

Unirradiated uranium isn't all that dangerous. It's only once it's been irradiated in an online reactor that it becomes so (due to neutron activation and fision products). As long as any reactor isn't started until it's on orbit there's nothing particularly nasty on the rocket being launched.

The biggest issue is that you'd probably use highly enriched fuel for mass reduction so you'd want to be able to recover it if the spacecraft didn't make orbit, but even if it gets incinerated and disperses into the atmosphere it's no big deal.

Of course media and public would probably react hysterically, but that's a separate issue.

Edited May 8, 2018 by RCgothic

[ment18]

On 5/7/2018 at 8:18 AM, KSK said:

Quick bit of searching gets me approximately 16 tons per solar array for the ISS which presumably includes the Integrated Truss section and rotating joint needed to point the thing. For comparison the spacer sections of the Integrated Truss weigh in at approximately 2 tons each. So call it 14 tons per solar array and joint.

So - back of an envelope calculation, that's 2.1 tons per kW for ISS solar arrays compared to 620kg per kW for KRUSTY.

So, very roughly, KRUSTY has three times the power density, unless my arithmetic has gone askew somewhere. On the other hand, using those same numbers and assuming that a scaled up version of KRUSTY can be built and that it's power output scales linearly with it's mass (omigosh, my hands are sore with all this waving), you would need a 74 ton reactor to equal the ISS output. 

That's a lot of fissile material to strap on top of a rocket...

 

Edit: I expect you could design a lighter version of the ISS arrays these days but even so I think KRUSTY would still have the edge in terms of power density.

Based on the wiki page you linked, each pair of solar arrays and associated stuff is about 16t.  There are 4 of them total on the ISS, which produces about 120kw, so 30kw per pair.  This means that the solar is actually around 500kg/kw.  And as you pointed out the ISS solar arrays are old and not very mass efficient.  Those 16t figures includes a lot of extra junk, like radiators and batteries, so the figures are much better for solar in reality.

Edit: The batteries per truss weight about 4t.  So more like 400kg/kw.

https://www.nasaspaceflight.com/2017/01/spacewalkers-upgrading-iss-batteries/

(48/4) * 335 = 4t

This paper claims 10kg/kw currently exists

https://digitalcommons.usu.edu/cgi/viewcontent.cgi?referer=https://www.google.com/&httpsredir=1&article=1941&context=smallsat

 

Edited May 8, 2018 by ment18

[tater]

2 minutes ago, ment18 said:

Based on the wiki page you linked, each pair of solar arrays and associated stuff is about 16t.  There are 4 of them total on the ISS, which produces about 120kw, so 30kw per pair.  This means that the solar is actually around 500kg/kw.  And as you pointed out the ISS solar arrays are old and not very mass efficient.  Those 16t figures might also include batteries, which would make the solar arrays themselves much, much better.

This seems to be about the same as kilowatt.

The trick is that solar will drop off as you get farther from the sun, so while solar is great in our back yard, it's gets worse as we go farther. It's also a pain on the Moon, where night is a couple weeks long.

[KSK]

Yeah you’re right. 2.1 kW per ton, not 2.1 tons per kW. My bad.

So yes - what @tater said.

As a comparison, the solar panels aboard Dragon apparently output about 5KW. Not sure how much they weigh but I’d be surprised if it was 3 tons, which would be the equivalent KRISPY weight (approximately).

[kerbiloid]

On 5/6/2018 at 10:46 PM, tater said:

Looks like a 1kW reactor is around 620 kg all in.

 

2 hours ago, RCgothic said:

recover it if the spacecraft didn't make orbit, but even if it gets incinerated and disperses into the atmosphere

 

Why not make it modular and deliver a small reactor or a fuel cassette for a big reactor in a man-rated capsule with LES and chutes.

Dock/berth, uncover with (whatever)arm, take, attach, put the cover back, deorbit the reusable capsule, repeat.
Level2 : put the capsule on a mini-spaceplane nose.

Spoiler

http://lemur59.ru/node/10246

Edited May 8, 2018 by kerbiloid

[tater]

Kilopower guy in interview said the 1kW is 2W/kg, and the 10kW version is 6-7W/kg.

Edited May 17, 2018 by tater

[Wjolcz]

What about solar power on Mars. How does that compare?

I'm asking mainly because I got into argument on Reddit recently with a guy who, when I said solar power is easier to handle, went "No, no, no. Nuclear and nothing else. There's no better solution and launching solar panels to Mars is just waste mass."

Edited May 16, 2018 by Wjolcz

[Bill Phil]

2 hours ago, Wjolcz said:

What about solar power on Mars. How does that compare?

I'm asking mainly because I got into argument on Reddit recently with a guy who, when I said solar power is easier to handle, went "No, no, no. Nuclear and nothing else. There's no better solution and launching solar panels to Mars is just waste mass."

Night time necessitates batteries or some form of energy storage. Cosine losses could be significant if the panels don't track the Sun and the sheer distance from the Sun adds another layer of problems.

Maybe a solar satellite in orbit beaming power down to the base... no night time, short eclipses, and ultra-light mirrors can overcome the distance problem (increasing irradiance on the panels). Then we need a rectenna.

[kerbiloid]

Do the ice caps have polar night?

[Brotoro]

50 minutes ago, kerbiloid said:

Do the ice caps have polar night?

Mars' axial tilt is similar to Earth's, so the polar cap regions of Mars have very long nights during winter (and continuous darkness for half a Martian year at the poles).

[hms_warrior]

Those W/kg numbers...does that include cooling?

Edited May 17, 2018 by hms_warrior

[kerbiloid]

43 minutes ago, Brotoro said:

Mars' axial tilt is similar to Earth's, so the polar cap regions of Mars have very long nights during winter (and continuous darkness for half a Martian year at the poles).

Yes. So, exactly at the places to mine the ice most effectively. solar panels are out of service for months.

Also if combine the ice mining with water electrolysis and sabatiering, you get a lot of hydrogen to cool a compact reactor, before it becomes a hydrocarbon. 

Melt the ice with overaheated hot water/steam, collect the molten water, heat it with reactor's waste heat, electrolize, use the hydrogen in the internal contour of its colling system, use the molten water in the external contour, use it to melt ice.
Move the hot hydrogen from the cooling system into sabatier pipe together with carbon dioxide from a gas splitter/condenser, get methane.
Store methane and free oxygen in tanks.
Move nitrogen from the same gas scoop/splitter/condenser (several % of atmo) together with the same hydrogen into ammonia pipe, get ammonia, store it.

So, one plant - 4 processes and power.
LqdMethane, LqdAmmonia, LqdOxygen, LqdArgon, Water, ElectricCharge (Megajoules if KSPI-E)

***

2nd plant - make methanol, hydrogen peroxide, ethylene oxide.

***

3nd plant - nitric synthesis. Hypergolics, etc.

***

Integrate into the first plant (with reactor) a furnace to burn out all hydrocarbon wastes from three plants and mix them to the atmoscoops incoming products.

***

Profit!!!

Edited May 17, 2018 by kerbiloid

[tater]

On 5/15/2018 at 4:41 PM, tater said:

Kilopower guy in interview said the 1kW is 2W/kg, and the 10kW version is 6-7W/kg.

I edited this to fix an errant "k" that appeared. 6 to 7 W per kg.