Author Topic: Will SpaceX use NASA Kilopower Nuclear Reactors?  (Read 26227 times)

Offline kfsorensen

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Re: Will SpaceX use NASA Kilopower Nuclear Reactors?
« Reply #80 on: 01/15/2018 11:05 PM »
No, gigawatts.  The nuclear thermal rocket cores they tested back in the 1960s had thermal powers of several gigawatts apiece, making them the largest nuclear reactors (by thermal power) ever built in the United States.

Offline john smith 19

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Re: Will SpaceX use NASA Kilopower Nuclear Reactors?
« Reply #81 on: 01/15/2018 11:49 PM »
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.
Technically what you were proposing is more like those Solar Thermal Rocket concepts in the 80's, with a lump of porus carbon at the focus of a mirror array with GH2 streamed through it.

Actually I think the thrust was about that level as well.

An actual full on NTR is indeed in the GW range and AFAIK there is no serious funding on the table to build one of those. I think they're trying to recover the mfg technology of both NTR designs (the graphite thermal spectrum and the tungsten cermet fast spectrum) but that's a long way from being able to design (or even recreate) an NTR, not to mention the serious ground level test facilities needed.
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Offline Robotbeat

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Re: Will SpaceX use NASA Kilopower Nuclear Reactors?
« Reply #82 on: 01/16/2018 12:39 AM »
Yeah, there has been some fuel element work on NTR.

kfsorensen convinced me NTR really isn't that great, but I think that it is a useful long-term technology, so I'm not opposed to work on it.

I guess if I had multiple gigawatts of thermal fission power, I'd probably want it as a surface power reactor rather than as a rocket engine. The designs are obviously very different typically, but perhaps you could somehow dump heat to the CO2 atmosphere (compressed somewhat) instead of hydrogen. Someone had proposed such a modification for a Mars nuclear aircraft, but it should work on the ground, too.

Apparently some of the low TRL work NASA is doing on NTR is about using low enriched uranium (~30%, right at the cut-off for some definition of "low") in order to reduce the cost and regulatory burden of NTR.
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Offline john smith 19

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Re: Will SpaceX use NASA Kilopower Nuclear Reactors?
« Reply #83 on: 01/16/2018 07:05 AM »
Yeah, there has been some fuel element work on NTR.

kfsorensen convinced me NTR really isn't that great, but I think that it is a useful long-term technology, so I'm not opposed to work on it.
I think Mueller while at SX said they saw NTR as a key long term enabler of settlement. While 90-1000secs Isp doesn't sound great next to Ion thrusters or fission fragment designs it's still 100% than the best available LO2/LH2 engines and it's the only high thrust  technology available with a TRL above 0 (highly energetic materials like monoHydrogen , or Nitrogen rings might deliver but their storage and mfg is close to SF.
Quote from: Robotbeat
I guess if I had multiple gigawatts of thermal fission power, I'd probably want it as a surface power reactor rather than as a rocket engine. The designs are obviously very different typically, but perhaps you could somehow dump heat to the CO2 atmosphere (compressed somewhat) instead of hydrogen. Someone had proposed such a modification for a Mars nuclear aircraft, but it should work on the ground, too.
The fundamental problem is the design lives of NTRs are measured in hours and a surface thermal system is in years. The power densities are much higher. IMHO a surface power reactor would be a completely different design. I think the best  you could do is reuse the fuel rod design, with greater spacing and different stacking, lower gas speeds but higher gas flows etc.
Quote from: Robotbeat
Apparently some of the low TRL work NASA is doing on NTR is about using low enriched uranium (~30%, right at the cut-off for some definition of "low") in order to reduce the cost and regulatory burden of NTR.
LEU is a legal definition. Kilopower is HEU, but the volumes are quite small. An NTR is HEU and is big and its Uranium is relatively accessible (not one single big block). That makes people very nervous.

Kilopower is a relatively low profile effort, but formal NTR testing will be much more public and public concerns will need to be dealt with. It will also be much more expensive (IIRC the line item for NTR was $13Bn, compare that with Kilopower to date. $100m? $200m? From lots of disparate sources)

What's been achieved by the Kilopower to get even this far (given we don't know the results of the press conference) on the funding they've secured, is amazing.
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Offline speedevil

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Re: Will SpaceX use NASA Kilopower Nuclear Reactors?
« Reply #84 on: 01/16/2018 07:57 AM »
I think Mueller while at SX said they saw NTR as a key long term enabler of settlement. While 90-1000secs Isp doesn't sound great next to Ion thrusters or fission fragment designs it's still 100% than the best available LO2/LH2 engines and it's the only high thrust  technology available with a TRL above 0

I would say Orion has a TRL above 0 too.
But that has issues with other sorts of readiness levels.

Offline john smith 19

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Re: Will SpaceX use NASA Kilopower Nuclear Reactors?
« Reply #85 on: 01/16/2018 10:48 PM »
I think Mueller while at SX said they saw NTR as a key long term enabler of settlement. While 90-1000secs Isp doesn't sound great next to Ion thrusters or fission fragment designs it's still 100% than the best available LO2/LH2 engines and it's the only high thrust  technology available with a TRL above 0

I would say Orion has a TRL above 0 too.
But that has issues with other sorts of readiness levels.
I'd forgotten about Orion. That would be another candidate in the high thrust area, but it's engineering (despite massive improvements in CAD/CAM CFD and FEA) remains very tough.
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C Apply So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline Space Junkie

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Re: Will SpaceX use NASA Kilopower Nuclear Reactors?
« Reply #86 on: 01/18/2018 08:05 PM »

Offline Robotbeat

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Re: Will SpaceX use NASA Kilopower Nuclear Reactors?
« Reply #87 on: 01/18/2018 08:07 PM »
I think Mueller while at SX said they saw NTR as a key long term enabler of settlement. While 90-1000secs Isp doesn't sound great next to Ion thrusters or fission fragment designs it's still 100% than the best available LO2/LH2 engines and it's the only high thrust  technology available with a TRL above 0

I would say Orion has a TRL above 0 too.
But that has issues with other sorts of readiness levels.
I'd forgotten about Orion. That would be another candidate in the high thrust area, but it's engineering (despite massive improvements in CAD/CAM CFD and FEA) remains very tough.
Additionally, the most realistic implementations of Orion didn't have an Isp really much better than NTR.
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Offline john smith 19

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Re: Will SpaceX use NASA Kilopower Nuclear Reactors?
« Reply #88 on: 01/18/2018 08:52 PM »
Here are the the slides from the Kilopower briefing today:

https://www.nasa.gov/sites/default/files/atoms/files/kilopower-media-event-charts-final-011618.pdf
Thanks for that.

Do we  have any idea what the contents of the presentation were? We know the goals of the tests, but do we have any idea of how well they've been achieved?
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Offline john smith 19

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Re: Will SpaceX use NASA Kilopower Nuclear Reactors?
« Reply #89 on: 01/18/2018 08:55 PM »
Additionally, the most realistic implementations of Orion didn't have an Isp really much better than NTR.
I'd thought Orion was meant to be orders of magnitude over the best chemical systems.
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C Apply So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline Robotbeat

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Re: Will SpaceX use NASA Kilopower Nuclear Reactors?
« Reply #90 on: 01/18/2018 08:56 PM »
Tests aren't finished, yet.

They did the live-fission proof of concept test in FY12, I believe, where they used heat pipes to extract heat from the small HEU core and generate a small amount of power with a Sterling engine. But the actual fission tests for this round of Kilopower won't be done finished until March of this year, so in a couple months.
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Online RotoSequence

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Re: Will SpaceX use NASA Kilopower Nuclear Reactors?
« Reply #91 on: 01/18/2018 08:58 PM »
Additionally, the most realistic implementations of Orion didn't have an Isp really much better than NTR.
I'd thought Orion was meant to be orders of magnitude over the best chemical systems.

Specific impulse doesn't matter as much when each impulse releases more energy than an entire rocket.

Offline Robotbeat

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Re: Will SpaceX use NASA Kilopower Nuclear Reactors?
« Reply #92 on: 01/18/2018 09:06 PM »
Additionally, the most realistic implementations of Orion didn't have an Isp really much better than NTR.
I'd thought Orion was meant to be orders of magnitude over the best chemical systems.
Yup, but the nearer term implementations aren't. You can, for instance, increase the thrust a lot if you add ballast (inert mass). That also reduces the thermal load on the pusher plates, making them easier to engineer.
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Offline Space Junkie

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Re: Will SpaceX use NASA Kilopower Nuclear Reactors?
« Reply #93 on: 01/18/2018 11:44 PM »
Do we  have any idea what the contents of the presentation were? We know the goals of the tests, but do we have any idea of how well they've been achieved?

The audio doesn't seem to have been posted yet. Here are a few tweets:

https://twitter.com/SciGuySpace/status/954041916353630208
Quote
Listening to the Kilopower news conference. Not much "news" yet, but NASA says it wants the power system for ISRU activities on the lunar and Martian surfaces.

https://twitter.com/SpcPlcyOnline/status/954046295227949061
Quote
NASA's Lee Mason is explaning the Kilopower Project.  Compact reactor for human missions on planetary surfaces.  Compact means core is size of paper towel roll and height is about the same as a man or woman.
Scalable from 1-10 kWe.

https://twitter.com/SpcPlcyOnline/status/954055664078336002
Quote
Q - any other space agencies working on space fission reactors?
A - Russians have always had program, launched 33, but their financial situation has slowed it.  China has published papers on it, but don't know what they may be doing beyond that.

@SpcPlcyOnline has some more tweets about the briefing, but it's nothing we didn't already know. The audio was apparently pretty bad.

BTW, this recent op-ed by John Casani in support of space fission power was pretty good. Basic, but there were a few nuggets I hadn't seen before.
http://spacenews.com/op-ed-an-argument-for-space-fission-reactors/

This blogger also goes into Kilopower in some detail.
https://beyondnerva.wordpress.com/2017/11/19/krusty-first-of-a-new-breed-of-reactors-kilopower-part-ii/

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Re: Will SpaceX use NASA Kilopower Nuclear Reactors?
« Reply #94 on: 01/19/2018 09:29 AM »
An important slide wrt the thread title,
DM

Offline john smith 19

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Re: Will SpaceX use NASA Kilopower Nuclear Reactors?
« Reply #95 on: 01/19/2018 11:11 AM »
Specific impulse doesn't matter as much when each impulse releases more energy than an entire rocket.
For the kind of money such a programme would cost it has to offer a serious increase in Isp. NTR is estimated to cost 10s of $Bn for a 2x increase over chemical Isp.  Orion would be much more expensive give the safety precautions needed throughout the whole design, build and operating of the system.
Yup, but the nearer term implementations aren't. You can, for instance, increase the thrust a lot if you add ballast (inert mass). That also reduces the thermal load on the pusher plates, making them easier to engineer.
I didn't think lack of thrust was ever an issue with Orion.  :(

My first thought would be put a bag of water between the pusher plate and the (what's the correct term these days?) "fission package."
Tests aren't finished, yet.

They did the live-fission proof of concept test in FY12, I believe, where they used heat pipes to extract heat from the small HEU core and generate a small amount of power with a Sterling engine. But the actual fission tests for this round of Kilopower won't be done finished until March of this year, so in a couple months.
I hadn't realized that. I knew they were expected to start Nov/Dec '17 but I'd thought they were only run a couple of months.

If I'd realized they were running to March I wouldn't have expected anything substantial till then beyond "We put all the bits together. It's gone critical. Nothing has blown up,"  which is encouraging but obviously they've still got a long way to go.
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Offline john smith 19

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Re: Will SpaceX use NASA Kilopower Nuclear Reactors?
« Reply #96 on: 01/19/2018 11:46 AM »

This blogger also goes into Kilopower in some detail.
https://beyondnerva.wordpress.com/2017/11/19/krusty-first-of-a-new-breed-of-reactors-kilopower-part-ii/
The blog is very interesting. Especially the ways they've managed to leverage existing resources to get the tests done. Especially the issues with thermal vacuum testing, which is absolutely vital for this sort of thing.  Making the system realistic as necessary (to collect data that will accurately model the full system) without unnecessary duplication.
Putting the reflector on a lift is kind of like the Toshiba 3S design, and obviously makes very easy to shut the reactor down by bleeding the hydraulic fluid off the drive cylinders.

One odd thing about the blog was it talked about the "DU Core" mfg for testing to have 15% U235. That makes no sense. A DU core should have U235 levels substantially below the 0.7% of natural Uranium.
[EDIT
Small note. Large Stirling engines have been used IRL. They are one option for the power plants of Diesel electric submarines mfg (IIRC) by German and Dutch companies. So there is operational experience with the technology, it's just not with nuclear reactor heat sources or in the US ]
« Last Edit: 01/20/2018 09:46 AM by john smith 19 »
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Offline john smith 19

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Re: Will SpaceX use NASA Kilopower Nuclear Reactors?
« Reply #97 on: 01/19/2018 11:54 AM »
An important slide wrt the thread title,
Indeed.

Realistically there is no chance that SX could ever have done this on their own. However if they can get it supplied as a service IE a complete package, that radically changes the playing field, just as a nuclear thermal "tug" would (although I think the chances of such a thing happening anytime soon are very remote).
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C Apply So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline Robotbeat

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Re: Will SpaceX use NASA Kilopower Nuclear Reactors?
« Reply #98 on: 01/19/2018 01:22 PM »
An important slide wrt the thread title,
What's important for commercial missions is price of Kilopower units. If they cost $100m, no way in heck it will be affordable. Even $10 million is a lot for just 10kW of power.
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Online AncientU

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Re: Will SpaceX use NASA Kilopower Nuclear Reactors?
« Reply #99 on: 01/19/2018 02:17 PM »
An important slide wrt the thread title,
What's important for commercial missions is price of Kilopower units. If they cost $100m, no way in heck it will be affordable. Even $10 million is a lot for just 10kW of power.

Especially since many apps will require tens of mega-Watts... $10billion is laughable from commercial perspective.
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