Will SpaceX use NASA Kilopower Nuclear Reactors?

[BrightLight]

What are mass estimates for operational 1KW and 10KW versions?

Would they stay mounted to lander that delivers them to surface? Lander may need  wheels to move to final location.

This table came from:
NASA's Kilopower Reactor Development and the Path to Higher Power Missions, Technical Report · November 2017
DOI: 10.13140/RG.2.2.32371.22565
https://www.researchgate.net/publication/320834023

Five 10kWe reactors - 40kWe plus a spare on a single lander gives a roughly a 2:1 advantage over solar at Mars surface for ISRU.  Additional advantages include the rate at which fuel can be created.

[Kaputnik]

It must be difficult to directly compare the power/kg of solar and fission systems: you need to consider battery storage for solar (if necessary- it may be more mass efficient to only run your ISPP during daylight hours), and also any potential uses for the heat waste from fission.

Any ideas how the above numbers were derived?

[BrightLight]

It must be difficult to directly compare the power/kg of solar and fission systems: you need to consider battery storage for solar (if necessary- it may be more mass efficient to only run your ISPP during daylight hours), and also any potential uses for the heat waste from fission.

Any ideas how the above numbers were derived?

Most of what your asking is in the paper:
"The study took three different approaches to the solar architecture design including—1A, daylight-only operation at 1/5 production; 1B, around-the-clock operation at 1/5 production; and 1C, daylight-only operation at 2/5 production. All three designs used the ATK Ultraflex™ arrays that were designed to operate at 120 Vdc, with a conversion efficiency of 33 percent. The arrays were mounted on a gimbal that would track the Sun and perform dust mitigation by sloping to 45°. Array and battery sizing changed with architecture options with contingencies for a 120-d global dust storm and an average of 10 h/sol of daylight. Lithium ion batteries were used for energy storage at 165 Wh/kg.
The fission option used a slightly oversized 10-kWe Kilopower unit with a permanent radiator attached to the top of the lander. The reactor operated 24 h a day at 6.5 kWe (65 percent capacity) with no interruptions or power loss from dust storms or landing locations. Power conversion was performed by eight 1,250-We Stirling engines in the dual opposed configuration."

[john smith 19]

Most of what your asking is in the paper:
"The study took three different approaches to the solar architecture design including—1A, daylight-only operation at 1/5 production; 1B, around-the-clock operation at 1/5 production; and 1C, daylight-only operation at 2/5 production. All three designs used the ATK Ultraflex™ arrays that were designed to operate at 120 Vdc, with a conversion efficiency of 33 percent. The arrays were mounted on a gimbal that would track the Sun and perform dust mitigation by sloping to 45°. Array and battery sizing changed with architecture options with contingencies for a 120-d global dust storm and an average of 10 h/sol of daylight. Lithium ion batteries were used for energy storage at 165 Wh/kg.
The fission option used a slightly oversized 10-kWe Kilopower unit with a permanent radiator attached to the top of the lander. The reactor operated 24 h a day at 6.5 kWe (65 percent capacity) with no interruptions or power loss from dust storms or landing locations. Power conversion was performed by eight 1,250-We Stirling engines in the dual opposed configuration."

Note that means the radiators don't need any complex (and potentially unreliable) unfolding mechanism, and can presumably be shaped to allow dust to drop off them, or carry some kind of sliding "wiper" mechanism to keep them clean.

It also means they had a lot of reserve power in case the schedule had to be accelerated.

AFAIK Kilopower is under test in Nevada right now. I wonder if anyone has an update on how the testing is going?

[BrightLight]

Most of what your asking is in the paper:
"The study took three different approaches to the solar architecture design including—1A, daylight-only operation at 1/5 production; 1B, around-the-clock operation at 1/5 production; and 1C, daylight-only operation at 2/5 production. All three designs used the ATK Ultraflex™ arrays that were designed to operate at 120 Vdc, with a conversion efficiency of 33 percent. The arrays were mounted on a gimbal that would track the Sun and perform dust mitigation by sloping to 45°. Array and battery sizing changed with architecture options with contingencies for a 120-d global dust storm and an average of 10 h/sol of daylight. Lithium ion batteries were used for energy storage at 165 Wh/kg.
The fission option used a slightly oversized 10-kWe Kilopower unit with a permanent radiator attached to the top of the lander. The reactor operated 24 h a day at 6.5 kWe (65 percent capacity) with no interruptions or power loss from dust storms or landing locations. Power conversion was performed by eight 1,250-We Stirling engines in the dual opposed configuration."

Note that means the radiators don't need any complex (and potentially unreliable) unfolding mechanism, and can presumably be shaped to allow dust to drop off them, or carry some kind of sliding "wiper" mechanism to keep them clean.

It also means they had a lot of reserve power in case the schedule had to be accelerated.

AFAIK Kilopower is under test in Nevada right now. I wonder if anyone has an update on how the testing is going?

From the paper - the Kilopower reactor thermal radiators don't require complex folding to fit into the LV fairing.
I will talk to the Kilopower folks and find out if I can release the info on the NNTS results.

[john smith 19]

From the paper - the Kilopower reactor thermal radiators don't require complex folding to fit into the LV fairing.

Eliminating the tricky failure modes of bespoke folding mechanisms. that's very attractive from both a cost and a reliability standpoint

I will talk to the Kilopower folks and find out if I can release the info on the NNTS results.

That would be very exciting. The first space rated power fission reactor designed in the US since the early 60's.

I think most people here would consider that a pretty big deal.

[BrightLight]

Kilopower briefing on Thursday, Jan 18
https://www.nasa.gov/press-release/nasa-partners-discuss-power-for-future-space-exploration

NASA and its partners will host a news conference at noon EST (9 a.m. PST) Thursday, Jan. 18, at the National Atomic Testing Museum in Las Vegas, to discuss a recent experiment involving a new power source that could provide the safe, efficient and plentiful energy needed for future robotic and human space exploration missions.
Audio of the news conference and presentation slides will stream live on NASA’s website.

[john smith 19]

Kilopower briefing on Thursday
https://www.nasa.gov/press-release/nasa-partners-discuss-power-for-future-space-exploration

NASA and its partners will host a news conference at noon EST (9 a.m. PST) Thursday, Jan. 18, at the National Atomic Testing Museum in Las Vegas, to discuss a recent experiment involving a new power source that could provide the safe, efficient and plentiful energy needed for future robotic and human space exploration missions.
Audio of the news conference and presentation slides will stream live on NASA’s website.

Terrific news. It would be great if someone from the site can be there, but I don't know if that's going to be possible. 

TBH after 54 years since SNAP 20a even a bad result would still be pretty amazing, given the competing pressures of very limited time and budget and highly expanded H&S oversight.  I'm guessing the fact they are going to a formal press conference indicates the the results have been quite positive.

Watching those videos of SNAP 20a being assembled, and the somewhat relaxed attitude to radiation safety (by modern standards) was eye opening.

[docmordrid]

>
Watching those videos of SNAP 20a being assembled, and the somewhat relaxed attitude to radiation safety (by modern standards) was eye opening.

It was a different time with many radiologists direct viewing non- intensified fluoroscopic imaging screens, their head and much of their neck entirely within the exit beam. 20+ patients a day, 5-6 days a week.

The good old days.... /s

[Dave G]

It must be difficult to directly compare the power/kg of solar and fission systems: you need to consider battery storage for solar...

Exactly.  Many people seem to miss this.

However, reliability increases when you have multiple power sources of different types, so I suspect they'll use a combination of solar, batteries, and nuclear.

And that's not a bad combination for Earth either.

[ppb]

Kilopower briefing on Thursday, Jan 18
https://www.nasa.gov/press-release/nasa-partners-discuss-power-for-future-space-exploration

NASA and its partners will host a news conference at noon EST (9 a.m. PST) Thursday, Jan. 18, at the National Atomic Testing Museum in Las Vegas, to discuss a recent experiment involving a new power source that could provide the safe, efficient and plentiful energy needed for future robotic and human space exploration missions.
Audio of the news conference and presentation slides will stream live on NASA’s website.

This is a HUGE deal. I would argue that our lack of progress in spaceflight over the last 50 years is highly correlated to little advancement in propulsion/energy technology development. Consider our chances of landing men on the moon had we not developed LH2 engines. Or anything beyond Mars without RTEG.

[john smith 19]

Kilopower briefing on Thursday, Jan 18
https://www.nasa.gov/press-release/nasa-partners-discuss-power-for-future-space-exploration

NASA and its partners will host a news conference at noon EST (9 a.m. PST) Thursday, Jan. 18, at the National Atomic Testing Museum in Las Vegas, to discuss a recent experiment involving a new power source that could provide the safe, efficient and plentiful energy needed for future robotic and human space exploration missions.
Audio of the news conference and presentation slides will stream live on NASA’s website.

This is a HUGE deal. I would argue that our lack of progress in spaceflight over the last 50 years is highly correlated to little advancement in propulsion/energy technology development. Consider our chances of landing men on the moon had we not developed LH2 engines. Or anything beyond Mars without RTEG.

True.

Kilopower opens up the possibility of extending the ability to power probes beyond Mars to propelling them (by ion thruster) potentially out to Pluto with constant thrust, something just about impossible with RTG's.  It also opens up the range of sensors that can be carried, either in number or in type, for example active radar

[speedevil]

Kilopower opens up the possibility of extending the ability to power probes beyond Mars to propelling them (by ion thruster) potentially out to Pluto with constant thrust, something just about impossible with RTG's.  It also opens up the range of sensors that can be carried, either in number or in type, for example active radar

I somewhat disagree with the latter, if the argument is for pulsed power over a few minute encounter - batteries can do a kilowatt for half an hour in five kilos or so. They do require to be kept warmer than -30C or so over cruise and warmed up to 20C.
But this is some orders of magnitude lighter than a kilowatt reactor.
If you choose to use radio, using high output power for post encounter data return in principle is one option, but this can also be addressed by LASER.

[john smith 19]

Kilopower opens up the possibility of extending the ability to power probes beyond Mars to propelling them (by ion thruster) potentially out to Pluto with constant thrust, something just about impossible with RTG's.  It also opens up the range of sensors that can be carried, either in number or in type, for example active radar

I somewhat disagree with the latter, if the argument is for pulsed power over a few minute encounter - batteries can do a kilowatt for half an hour in five kilos or so. They do require to be kept warmer than -30C or so over cruise and warmed up to 20C.
But this is some orders of magnitude lighter than a kilowatt reactor.
If you choose to use radio, using high output power for post encounter data return in principle is one option, but this can also be addressed by LASER.

I chose radar as an example of a system that would be much simpler to implement with more power.  The big thing is that you can run electric thrusters going to the outer planets, then switch over to running sensors when you get there. That's not really possible with RTG's and solar arrays at this size is quite large and heavy.

[speedevil]

I chose radar as an example of a system that would be much simpler to implement with more power.  The big thing is that you can run electric thrusters going to the outer planets, then switch over to running sensors when you get there. That's not really possible with RTG's and solar arrays at this size is quite large and heavy.

Outer planet electric thrusters are a great example of game-changing stuff enabled by reactors.
Encounter power rather less so, given the very short encounter times.
I haven't looked at kilopower properly, and suspect it's not useful for higher thrust gravity manoevers using hydrogen heated by 'waste' heat. (~700s@300C).

I do wonder if the political environment is sensitive enough to the fact reactors are safe to launch to not consider them as a PR issue compared to RTG.

[john smith 19]

Outer planet electric thrusters are a great example of game-changing stuff enabled by reactors.
Encounter power rather less so, given the very short encounter times.
I haven't looked at kilopower properly, and suspect it's not useful for higher thrust gravity manoevers using hydrogen heated by 'waste' heat. (~700s@300C).

I don't think anyone's talked about this. 10Kw can drive an ion thruster with an Isp of 3000secs. H2 is a real PITA to managed. I'd guess it would we simpler (at 300c) to vaporize water (that would hit 200bar).

I do wonder if the political environment is sensitive enough to the fact reactors are safe to launch to not consider them as a PR issue compared to RTG.

That's a good question.  RTG's are very hot and much more radioactive after mfg, but before they start generating power, than reactors.

Will future programmes announce they run on Kilopower, or simply not bother to mention how they are powered?

[Robotbeat]

10kW is like 40kW thermal. At an Isp of 700s, that's about 7km/s exhaust velocity... That's about 12 Newtons at 100% thermal efficiency (real engine will be somewhat less than that, maybe 50%, so 6 Newtons?). So you're stuck doing fairly low-thrust maneuvers.

...but much the weight of kilopower is in the radiators and dynamo. Don't need much of that stuff if you're building a rocket engine.

[john smith 19]

10kW is like 40kW thermal. At an Isp of 700s, that's about 7km/s exhaust velocity... That's about 12 Newtons at 100% thermal efficiency (real engine will be somewhat less than that, maybe 50%, so 6 Newtons?). So you're stuck doing fairly low-thrust maneuvers.

...but much the weight of kilopower is in the radiators and dynamo. Don't need much of that stuff if you're building a rocket engine.

Again it's 700s Vs 3000 secs of Isp. It's also the mass of that LH2 tank  you're carrying and of course what will do for cooling when it runs out?

That said 6N sounds like quite a high thrust level (by ion thruster standards), so could as an upper stage during Earth departure. However that's another development project. The question would be does the faster acceleration offset the complexity (LH2 tank, valving, injectors, nozzle) of this new stage (which is basically what it is) versus just making the Xenon tank bigger?

In terms of developmental "leverage" improving radiator efficiency sounds like it could be more broadly applicable. My instinct is better "tuned" high emissivity coatings, or carbon "hair" can make smaller, higher efficiency radiators which can operate in any environment better than existing designs.

In truth I doubt that on Mars any heat will be "waste" heat. A use can (and will) be found for all of it

[Robotbeat]

6N is only high thrust because it's low Isp. You can do a similar thing with a solar panel and resistojet/arcjet. Probably would be lighter weight in the inner solar system.

Nah, I think using kilopower for a nuclear thermal rocket doesn't make sense. Too low power. A REAL NTR is like Gigawatts.

[jpo234]

A REAL NTR is like Gigawatts.

1GW is a full sized power plant. Do you mean MW?

See for instance https://en.m.wikipedia.org/wiki/AP1000