Author Topic: NASA to make announcement concerning the Kilopower project  (Read 12919 times)

Offline john smith 19

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Re: NASA to make announcement concerning the Kilopower project
« Reply #40 on: 05/07/2018 07:24 AM »
Yeah, the aqueous reprocessing methods are messy, and produces lots of (mildly) irradiated nitric acid. Pyroprocessing improves matters, but you still have to mechanically strip and break down the clad. Metal fuel really helps... too bad it's not that great neutronically! It's nice that edge heating isn't a big deal on this, and I doubt that anything else other than CERMET would be good enough to get away with that.
Given the placing of the heat pipes for the 1Kw version it's fair to say that edge heating is a feature of the design.

On a general point what's always got me is that despite a 1000-1200c pellet temperature PWR's only manage a 300c coolant temp. This gives thermal efficiency 10 (or more) % points below a coal or oil fired plant. It also means the turbines are special order and (apparently) 10x the cost because of the non standard steam conditions they have to deal with.
BTW Balance of plant costs were recognized as an issue as far back as the 1960's, hence the various "Advanced" gas cooled designs to more closely match SOP of conventional plants. 
An obvious question would be if you could go LEU while staying fast spectrum you're effectively looking at a breeder design (of sorts), turning U238 to Pu. However one of the features of space nuclear is its avoidance of fuel swelling issues by a very low burnup level. If this rises swelling might be more of a problem.

An under recognized aspect of plant costs is that control rod drives for commercial reactors are roughly $1m each, because of their critical role in plant safety. OTOH Kilopower "load follows" automatically.
In fact connecting the top end of those heat pipes to a water cooled heat spreader would make quite a good boiler, and companies like Siemens can supply turbines down to this power.

https://www.siemens.com/global/en/home/products/energy/power-generation/steam-turbines/d-r-steam-turbines.html

Which suggests (in principle) you could transport a complete power package in a 20' container, but you'd probably need to put the reactor inside a shield and connects some well insulated (and reasonably long) insulated pipes between the reactor and the turbogenerator package. 

I think the whole "Cast-in-place" nature of a one piece reactor core is quite attractive, especially insuring intimated contact with the heat pipes, or at least a well fitting sleeve they can be slid down. 
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Offline john smith 19

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Re: NASA to make announcement concerning the Kilopower project
« Reply #41 on: 05/07/2018 07:38 AM »
In principle, water heated to 800C has a comparable ISP to hydrazine, so the heat could be used directly.

Thrust is small, though perhaps a hundred times the ion engine.
I think the question would be what is the total impulse requirement of a water system Vs a hypergol system? On the upside propellant freezing has been an issue with systems for long duration, outer planets missions, hence the use of miniature radioactive heaters. With an operating reactor (even on "idle") that should not be an issue.
Quote from: speedevil
For launch safety I can't imagine the long-pole being the hydrazine though.
You might be surprised

AFAIK there are no plans to launch an operating reactor. It's radiation hazard is thus that of the low level Alpha emissions from the lump of Uranium. Being a single lump it's minimally prone to dust issues (Uranium is pyrophoric if finally divided). Historically the joker has been that if a thermal spectrum reactor is dropped in sea water (or wet sand) it's reactivity goes up  because they are good moderators. Kilopower is a fast reactor, so it's spectrum WRT to moderators does not match. They make neutrons less likely to interact with it in a way that will stimulate it.

OTOH any baseline nuclear/hygergol bus is likely to be quite heavy, so need some pretty big tanks of NTO/UDMH, and that stuff is WMD grade toxic, aggressive and prone to becoming airborne if it leaks. It can also be absorbed through the skin so a full body impermeable SCAPE suit is needed rather than just a gas mask.

An operating Kilopower reactor is not safe to approach, but on the pad I'd be more worried about the hypergols.
« Last Edit: 05/07/2018 07:55 AM by john smith 19 »
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Offline ThereIWas3

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Re: NASA to make announcement concerning the Kilopower project
« Reply #42 on: 05/07/2018 02:15 PM »
An operating Kilopower reactor is not safe to approach, but on the pad I'd be more worried about the hypergols.

Would this be a hazard to the electronics on board a deep space probe?  These things are usually not very big, maybe 1m on a side, and it is hard to get very far away.   Some probes have had a long truss arm to hold some pieces at a distance, though that starts to get interesting from a manuvering point of view when the reactor part masses at least as much as everything else put together.  For example, Dawn massed a bit over one ton at launch, which is close to the large 10kW size of a KRUSTY reactor.
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Offline speedevil

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Re: NASA to make announcement concerning the Kilopower project
« Reply #43 on: 05/07/2018 03:42 PM »
An operating Kilopower reactor is not safe to approach, but on the pad I'd be more worried about the hypergols.

Would this be a hazard to the electronics on board a deep space probe?  These things are usually not very big, maybe 1m on a side, and it is hard to get very far away.   
'yes' - but no.
To make the weight low, the shielding is only in one direction.
You put the probe in the shadow of this block of shielding, usually on a bit of an arm.
It is a concern, but less dynamically than - for example 20m*20m of solar panel.

Offline A_M_Swallow

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Re: NASA to make announcement concerning the Kilopower project
« Reply #44 on: 05/07/2018 06:57 PM »
{snip}
An operating Kilopower reactor is not safe to approach, but on the pad I'd be more worried about the hypergols.

Replacements for traditional hypergols are being tested.

Propellant AF-M315E developed under the Green Propellant Infusion Mission is due for launch.

Masten Space has the rival MXP-351 propellant.
https://en.wikipedia.org/wiki/Masten_Space_Systems#MXP-351

Offline john smith 19

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Re: NASA to make announcement concerning the Kilopower project
« Reply #45 on: 05/07/2018 08:38 PM »
Would this be a hazard to the electronics on board a deep space probe?  These things are usually not very big, maybe 1m on a side, and it is hard to get very far away.   
'yes' - but no.
To make the weight low, the shielding is only in one direction.
You put the probe in the shadow of this block of shielding, usually on a bit of an arm.
It is a concern, but less dynamically than - for example 20m*20m of solar panel.
Indeed.

There are various tweaks in a reactor powered design. A key one is that the reactor could be in front of the experimental payload with just the power and monitoring cables coming through (around?) the shield. Obviously the further forward the reactor is in front of the shield the smaller a sector of the sphere the reactor is emitting over is an absorption target for the electronics (True for gamma rays. Works for neutrons as well?). Given the fairly low thrusts of even large ion thrusters the truss separating the reactor from the shield and payload can still be pretty light.
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. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline A_M_Swallow

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Re: NASA to make announcement concerning the Kilopower project
« Reply #46 on: 05/08/2018 01:06 PM »
Kilopower could also power telescopes. Since the reactor works in the dark the telescopes can be in craters shielded from the sun.

Kilopower can provide both electricity and heat to keep the equipment warm.

Offline BeyondNERVA

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Re: NASA to make announcement concerning the Kilopower project
« Reply #47 on: 05/08/2018 01:46 PM »

Given the placing of the heat pipes for the 1Kw version it's fair to say that edge heating is a feature of the design.

...

BTW Balance of plant costs were recognized as an issue as far back as the 1960's, hence the various "Advanced" gas cooled designs to more closely match SOP of conventional plants. 
An obvious question would be if you could go LEU while staying fast spectrum you're effectively looking at a breeder design (of sorts), turning U238 to Pu. However one of the features of space nuclear is its avoidance of fuel swelling issues by a very low burnup level. If this rises swelling might be more of a problem.

An under recognized aspect of plant costs is that control rod drives for commercial reactors are roughly $1m each, because of their critical role in plant safety. OTOH Kilopower "load follows" automatically.
In fact connecting the top end of those heat pipes to a water cooled heat spreader would make quite a good boiler, and companies like Siemens can supply turbines down to this power.

https://www.siemens.com/global/en/home/products/energy/power-generation/steam-turbines/d-r-steam-turbines.html

Which suggests (in principle) you could transport a complete power package in a 20' container, but you'd probably need to put the reactor inside a shield and connects some well insulated (and reasonably long) insulated pipes between the reactor and the turbogenerator package. 

I think the whole "Cast-in-place" nature of a one piece reactor core is quite attractive, especially insuring intimated contact with the heat pipes, or at least a well fitting sleeve they can be slid down. 

Wow, there's a lot to unpack here... and I'd love to pick your brain about a few things in the future. Feel free to get in contact with me through my blog!

The edge heating is a bonus only in the 1 kWe version, since none of the others have peripheral heat pipes. According to a couple far more knowlegeable friends than I, the metal fuel kinda oblivates the edge heating advantage in the balance of systems, but... you gotta play the margins in astronautical engineering, so it's worth looking at moving the outer ring of heat pipes on the larger models closer to the edge. I've got a file with KRUSTY's MCNP model, if you're interested, but I'm pretty sure you have it already!

http://permalink.lanl.gov/object/tr?what=info:lanl-repo/lareport/LA-UR-16-28377

There are two companies, to ny knowledge, that are exploiting heat pipe cooling already: Oklo Power is the more attractive one, IMO, for a number of reasons, but the biggest one is dirt simple: they're using a vertical core/PCS architecture, which allows heat pipes to also act as thermosiphons, which is a balance-of-energy-budget bonus to a large degree. Westinghouse also has a design - closer in line to the Megapower project through DNSA and DOD (possibly, considering the squirrely reporting the get away with) which I suspect are the primary funders of the higher powered (and UO2 fueled,prismatic FE variants), but it's horizontally oriented in operation. There's something going on with that PCS that I'd love to find out about, but... welcome to nuclear. Sometimes there's a door in you face, and it can't be breached with money.

As a non-Americocentric note, the UK pretty much only has high-temp gas cooled reactors. I didn't realize this until recently. I heartily endorse the quotes, and think that this is another example of British excptionalism being demonstrated by dropping the ball, as is their wont on advanced topics. IMO, between HTCGR and MSR (let the fanboys exult!), with a fission fragment reactor in the basement of every hospital, we've got EVERYTHING that fission has to offer - and let the civilians be as epically amazed as they should be!

Cast-in-place is epic... except as done at Y12. They're a weapons manufacturing facility that occasionally gets to pla with civilian work, so the Cold War is still very real. Just having the core manufactured there adds exceptional expense due to the fissile material reporting requirements... I think that you, John, understand the antipathy in the civ/mil nuc spectrum). So, in any other facility, it would potentially be cheaper... BWXT, are you listening?

Regulatory burden of casting/manufacturing aside, just casting the KRUSTY core seems to be an incredible achievement... U7 is the ideal, and they managed in on a corewith THAT cross section? I'd love to knkow about their thermal management system...assuming I don't have the DNA/NNSS/DOE tapping politely at my door at 3AM!

Ed Pheil seems skeptical of breeding in this design... and in these matters I tend to trust him! In the coming months I hope to rewrite my blogs into a proper system description (and webpage) of Kilopower, since my posts have focused on KRUSTY up until now... hopefully I'll be able to play with the fast spectrum LEU implications, and again, I'd love to pick your brain, John!

A spacecraft propulsion bus that combined nuclear powered Hall thrusters and chemical propulsion (likely hypergolic) would form a formidable basis for outer solar system exploration. Imagine a 'Block' series of standardized 'Buses' that can be attached to differing spec spacecraft... That would be very cool. And scaling them up for crewed spacecraft use would give terrific capability.

I call it Magellan III, because as much as I love Galileo/Cassini, they should have been Mariner II as a program... the names made them sound like the one-off spacecraft that they were deliberately designed NOT to be.


Indeed.

There are various tweaks in a reactor powered design. A key one is that the reactor could be in front of the experimental payload with just the power and monitoring cables coming through (around?) the shield. Obviously the further forward the reactor is in front of the shield the smaller a sector of the sphere the reactor is emitting over is an absorption target for the electronics (True for gamma rays. Works for neutrons as well?). Given the fairly low thrusts of even large ion thrusters the truss separating the reactor from the shield and payload can still be pretty light.

Another option is to have your power and propulsion in one leading module, and have your payload on the end of a cable being pulled behind... it adds GNC complexity, but saves a lot of mass compared to a load bearing truss.

All PCS equipment is on the payload side of the shield, so the only thing that you really need is a control cable for the stepping motor used for the control rod. One benefit to this design is that by monitoring the hot end temp of the Stirlings, you are also monitoring the fission power level to a reasonably high degree of confidence.

Yes, the inverse cube law also applies... but unfortunately, as the shield is slowing the neutrons you get additional gamma production within the shield, so it's not perfectly "spherical." Also, if anything is outside the shield then you will get backscatter from it, so you add a sphere (for a point), cylinder, etc of radiological source for each unshielded component.

IIRC one of the papers mentioned that the radiation flux recieved by the payload would be lower than that from an MMRTG, but I can't find the reference anywhere, and that seems kinda wonky to me. However, this is a matter of optimizing the shield thickness for the needs of the sensors being used, and is a fairly minor issue.

...

One thing to keep in mind is that most of the attention is given to the 10 kWe version right now, since it's the "big boy" in the design family, but the 1 kWe version is the most advanced - and that's more than enough for a lot of space probe missions. The flux off this reactor will be significantly lower than the 10 kWe version (although the shielding is also less, so the overall flux exposure is likely similar).

Offline john smith 19

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Re: NASA to make announcement concerning the Kilopower project
« Reply #48 on: 05/09/2018 07:58 AM »
Wow, there's a lot to unpack here... and I'd love to pick your brain about a few things in the future. Feel free to get in contact with me through my blog!

The edge heating is a bonus only in the 1 kWe version, since none of the others have peripheral heat pipes. According to a couple far more knowlegeable friends than I, the metal fuel kinda oblivates the edge heating advantage in the balance of systems, but... you gotta play the margins in astronautical engineering, so it's worth looking at moving the outer ring of heat pipes on the larger models closer to the edge. I've got a file with KRUSTY's MCNP model, if you're interested, but I'm pretty sure you have it already!

http://permalink.lanl.gov/object/tr?what=info:lanl-repo/lareport/LA-UR-16-28377
That's very flattering but you are over estimating my skills in this area.  :( Actually I'm guessing it's quite tricky to model in some ways. KRUSTY really has circular symmetry and MCNP works best in Cartesian co-ordinates. It's also quite homogeneous, compared to most PWRs, which have a well defined cell structure. 
Quote from: BeyondNERVA
There are two companies, to ny knowledge, that are exploiting heat pipe cooling already: Oklo Power is the more attractive one, IMO, for a number of reasons, but the biggest one is dirt simple: they're using a vertical core/PCS architecture, which allows heat pipes to also act as thermosiphons, which is a balance-of-energy-budget bonus to a large degree. Westinghouse also has a design - closer in line to the Megapower project through DNSA and DOD (possibly, considering the squirrely reporting the get away with) which I suspect are the primary funders of the higher powered (and UO2 fueled,prismatic FE variants), but it's horizontally oriented in operation. There's something going on with that PCS that I'd love to find out about, but... welcome to nuclear. Sometimes there's a door in you face, and it can't be breached with money.
If you're talking about the LANL "Special Purpose Reactor" design (5MW(t)) for remote locations the Idaho NL report says it's expected to use the Brayton cycle at 645c.

https://inldigitallibrary.inl.gov/sites/sti/sti/7365867.pdf

I'd call that a hot air driven gas turbine, which (in principle) puts it much closer to the knowledge base around conventional gas turbines than Helium.  Technically the TORI nuclear heated ramjet for project PLUTO would be in this class as well.
Quote from: BeyondNERVA
As a non-Americocentric note, the UK pretty much only has high-temp gas cooled reactors. I didn't realize this until recently. I heartily endorse the quotes, and think that this is another example of British excptionalism being demonstrated by dropping the ball, as is their wont on advanced topics. IMO, between HTCGR and MSR (let the fanboys exult!), with a fission fragment reactor in the basement of every hospital, we've got EVERYTHING that fission has to offer - and let the civilians be as epically amazed as they should be!
A "Fission fragment" reactor? That's normally associated with spaceflight (the actual fragment speed is about 5% of the speed of light. The sort of thing you want if you want to look at interstellar, rather than interplanetary distances).

Keep in mind though that the Pebble bed designs are also advanced, in the sense of running much  hotter than current PWR's and 1st generation GC reactors.  These were built in Germany and have been pursued in South Africa and (IIRC) Brazil. I think the French also had a 2nd generation GC reactor design in planning. The Germans seemed to have gone with plans for a gas turbine but He gas turbines are quite tough design problems (I think the OECD "Dragon" and the US "Peach Bottom" (?) needed GHe pump technology)

And of course all NTR designs (NERVA included) have been gas cooled in "straight through" mode.
Quote from: BeyondNERVA
Cast-in-place is epic... except as done at Y12. They're a weapons manufacturing facility that occasionally gets to pla with civilian work, so the Cold War is still very real. Just having the core manufactured there adds exceptional expense due to the fissile material reporting requirements... I think that you, John, understand the antipathy in the civ/mil nuc spectrum). So, in any other facility, it would potentially be cheaper... BWXT, are you listening?

Regulatory burden of casting/manufacturing aside, just casting the KRUSTY core seems to be an incredible achievement... U7 is the ideal, and they managed in on a corewith THAT cross section? I'd love to knkow about their thermal management system...assuming I don't have the DNA/NNSS/DOE tapping politely at my door at 3AM!
At the same time using Y12, and all it's reporting procedures might have been the only way to do this on the budget.  :(

This raises the question of getting approval for a design.
My feeling is that KRUSTY is more the "experimental aircraft" end of the nuclear regulatory process, but a design for commercial use is more like the passenger jet end of the process, and the current nuclear regulations make no distinction between a 2 seat Cessna (IE KRUSTY) and a Boeing 777.  :(

Regarding the mfg Uranium melts around 1300c while Zirconium melts at 1800c, so casting parts in Zirconium into it is not too big a deal.
Modern casting software can make the process much more predictable, provided you load it with the relevant materials properties (which they should be very well placed to provide).
This lets you place the runners and risers to ensure the mold is fully filled ares don't run dry due to premature freezing of the flow.
I'd guess the ideal for the process is vacuum melting and casting to eliminate porosity AFAP. Not that different to ordinary (high performance part) casting, but the irradiation of the hardware afterward....
Obviously the ideal is a U7Mo alloy rather than U10Mo but at this stage it's all about predicatability in materials properties.
Quote from: BeyondNERVA
Ed Pheil seems skeptical of breeding in this design... and in these matters I tend to trust him! In the coming months I hope to rewrite my blogs into a proper system description (and webpage) of Kilopower, since my posts have focused on KRUSTY up until now... hopefully I'll be able to play with the fast spectrum LEU implications, and again, I'd love to pick your brain, John!
"Breeding" is sometimes used a bit loosely. Historically it means a reactor that makes much  more fuel than it consumes, enough to power 2 (or more) reactors.
But in fact all you need to "breed" fuel is a supply of fissionable material. IE Material that can be converted into fissile material. 
So a reactor that's all fissile already can't breed.
OTOH a LEU version of KRUSTY has fuel that's 7-10% inert (the Mo) and about 70% fissionable (U238). Irradiate that with enough neutrons and you get U239, Pu240 etc. 

So while the "breeder reactor" remains on the drawing board for the (distant) future IRL all real reactors (with any level of U238 in the mix) have been "breeding" since they started up. Indeed breeding was the goal of the early UK and French programmes, but to make more efficient bombs.

Sadly with the US regulatory regime in force no US operator can make use of this fact.  :(
The fuel rod mfg's are not going to disrupt their business to enable this and any startup would have a regulatory mountain to climb to shift USG policy in this area.
Not really the sort of deal that VC's jump at funding. And that's before the actual technology issues of what approach you plan to productionize, which are also non trivial   :(
Quote from: BeyondNERVA
Another option is to have your power and propulsion in one leading module, and have your payload on the end of a cable being pulled behind... it adds GNC complexity, but saves a lot of mass compared to a load bearing truss.
An ideas that's been around since the mid 60's. Obviously you need 2 nozzles (at least) to give thrust symmetry and you have losses depending on how canted away from the centre line they are to avoid hitting the payload with ion thruster output.
Quote from: BeyondNERVA
All PCS equipment is on the payload side of the shield, so the only thing that you really need is a control cable for the stepping motor used for the control rod. One benefit to this design is that by monitoring the hot end temp of the Stirlings, you are also monitoring the fission power level to a reasonably high degree of confidence.

Yes, the inverse cube law also applies... but unfortunately, as the shield is slowing the neutrons you get additional gamma production within the shield, so it's not perfectly "spherical." Also, if anything is outside the shield then you will get backscatter from it, so you add a sphere (for a point), cylinder, etc of radiological source for each unshielded component.
This is where it gets tricky. IIRC you need stuff a dense layer like Tungsten up front then a high density of nuclei (like say plastic or graphite) to soak up the induced radiation.
But as a general principle keeping as much of the hardware outside the shield is a good. You can use more or less OTS senses, but best of all is the system that's self regulating.
Quote from: BeyondNERVA
IIRC one of the papers mentioned that the radiation flux recieved by the payload would be lower than that from an MMRTG, but I can't find the reference anywhere, and that seems kinda wonky to me. However, this is a matter of optimizing the shield thickness for the needs of the sensors being used, and is a fairly minor issue.
As always with such statements you need to look at the assumptions very carefully. An RTG will start irradiating the payload the moment it's placed close to it. A reactor only when it's switched on, which (for a probe) will only happen with it's been separated from the main payload.
...
Quote from: BeyondNERVA
One thing to keep in mind is that most of the attention is given to the 10 kWe version right now, since it's the "big boy" in the design family, but the 1 kWe version is the most advanced - and that's more than enough for a lot of space probe missions. The flux off this reactor will be significantly lower than the 10 kWe version (although the shielding is also less, so the overall flux exposure is likely similar).
True. At that level I think it's got broad parity with an RTG. You can start to think of running a small ion thruster on a probe during cruise (like DS1), then powering up more sensors on close approach.
But it's when you get to the 10Kwe level you get substantial thrust gains, offering payload masses, or transit times that are completely  outside the abilities of PV systems, especially for Outer Planets missions to Jupiter, Saturn and Uranus, but also on to Pluto and the Oort cloud.
« Last Edit: 05/09/2018 08:33 AM by john smith 19 »
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. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline speedevil

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Re: NASA to make announcement concerning the Kilopower project
« Reply #49 on: 05/09/2018 10:56 AM »
A "Fission fragment" reactor? That's normally associated with spaceflight (the actual fragment speed is about 5% of the speed of light. The sort of thing you want if you want to look at interstellar, rather than interplanetary distances).
https://www.nasa.gov/pdf/718391main_Werka_2011_PhI_FFRE.pdf - as one example - a 16 year manned round trip to callisto.

The acceleration is terrible - 150 microgee - but that is 5km/s/year, more or less what might be expected for a kilopower ion drive vehicle.
Like that vehicle, it's unattrative for short distances, but once you get beyond saturn, it comes into its own.

Offline Asteroza

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Re: NASA to make announcement concerning the Kilopower project
« Reply #50 on: 05/09/2018 11:43 PM »
If a tractor design is acceptable, having a propulsion package with two or more nozzles works great, and even if you need a stiffness that a tether can't provide you can go with a tensegrity truss or inflatable truss for low mass. Payload can trail behind on an inflatable boom truss setup, something of a cross between a triangular straight truss style or curving (like the Eiffel Tower). Most recent example would be the Valkyrie derivative spacecraft concept in the movie Avatar.

Offline BeyondNERVA

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Re: NASA to make announcement concerning the Kilopower project
« Reply #51 on: 05/13/2018 04:30 AM »

A "Fission fragment" reactor? That's normally associated with spaceflight (the actual fragment speed is about 5% of the speed of light. The sort of thing you want if you want to look at interstellar, rather than interplanetary distances).


Sorry it took me so long to respond... 1000+ things going on right now.

Yes, it's talked about in terms of spaceflight, but... it's got a non-Carnot-based PCS by default as its' primary PCS, and as a side effect, you get isotopic enrichment of EVERY fission fragment FOR FREE! Really, that seems like the holy grail (and a containment challenge, but an easily solvable one) for a hospital: you can get plenty of gamma sources of ANY intensity for gamma knife or gamma-isotopic therapy, separate out the pure alpha and beta isotopes for therapies that can be delivered by pneumatic tube, so if you've got an hour's half-life that isn't a deal-killer (because the sucker is in the basement), and any beamline you WANT, including neutron, is readily available!

For those not familiar:

http://www.rbsp.info/rbs/PDF/aiaa05.pdf
https://www.nasa.gov/pdf/718391main_Werka_2011_PhI_FFRE.pdf
http://www.rbsp.info/rbs/PDF/nets16b-ppt.pdf

Offline john smith 19

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Re: NASA to make announcement concerning the Kilopower project
« Reply #52 on: 05/13/2018 12:38 PM »
Sorry it took me so long to respond... 1000+ things going on right now.

Yes, it's talked about in terms of spaceflight, but... it's got a non-Carnot-based PCS by default as its' primary PCS, and as a side effect, you get isotopic enrichment of EVERY fission fragment FOR FREE! Really, that seems like the holy grail (and a containment challenge, but an easily solvable one) for a hospital: you can get plenty of gamma sources of ANY intensity for gamma knife or gamma-isotopic therapy, separate out the pure alpha and beta isotopes for therapies that can be delivered by pneumatic tube, so if you've got an hour's half-life that isn't a deal-killer (because the sucker is in the basement), and any beamline you WANT, including neutron, is readily available!

For those not familiar:

http://www.rbsp.info/rbs/PDF/aiaa05.pdf
https://www.nasa.gov/pdf/718391main_Werka_2011_PhI_FFRE.pdf
http://www.rbsp.info/rbs/PDF/nets16b-ppt.pdf
That's a fairly novel strategy. I'm not sure anyone has thought of using it that way.

One of the papers you referenced mentioned the idea of carbon fiber radiators and I think that's an excellent point.

In space thermal radiation is the only long term way to loose heat and the lower the delta t between the radiator and the environment the bigger that radiator has to be.

It's been very interesting to watch the way the ability to tailor the emitance and absorbance spectrums of radiation to and from surfaces has improved.

This will always be a trade off between extracting the heat (from the core) and simple reflecting it back (mirror surfaces tuned to one wavelength can be >99% reflecting at that frequency).

On a side topic. I was thinking about how fast the human race gets around it's own back yard IE the Solar System.

It took New Horizons 9.5years to reach Pluto.

The whole Solar System is roughly 11 light hours across.  Not even half a light day.

A drive capable of reaching 1/1000 the speed of light would be an enormous improvement. It would put Pluto on an 8 month flight (point to point, ignoring orbits).

I think the bottom line is that there is a lot of room for improvement before we get into the realms of "breakthrough physics," "warp drives" etc.
« Last Edit: 05/13/2018 12:48 PM by john smith 19 »
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. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline BeyondNERVA

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Re: NASA to make announcement concerning the Kilopower project
« Reply #53 on: 05/13/2018 03:56 PM »


It's been very interesting to watch the way the ability to tailor the emitance and absorbance spectrums of radiation to and from surfaces has improved.

This will always be a trade off between extracting the heat (from the core) and simple reflecting it back (mirror surfaces tuned to one wavelength can be >99% reflecting at that frequency).


I wonder... is there anything you can think of along these lines to replace the quartz in a nuclear lightbulb? The silicon mirrors are obviously too thermally limited, but... it's always been a favorite design of mine, despite the incredible mass of the system.


On a side topic. I was thinking about how fast the human race gets around it's own back yard IE the Solar System.

It took New Horizons 9.5years to reach Pluto.

The whole Solar System is roughly 11 light hours across.  Not even half a light day.

A drive capable of reaching 1/1000 the speed of light would be an enormous improvement. It would put Pluto on an 8 month flight (point to point, ignoring orbits).

I think the bottom line is that there is a lot of room for improvement before we get into the realms of "breakthrough physics," "warp drives" etc.

I couldn't agree more. Unfortunately, the vast majority of systems with even 1/10th of that capability are so far down the TRL spectrum that it's rather depressing, and often only due to readioillogical fears preventing testing. I've been lucky enough to make friends with a couple people who were students looking at vapor core and open cycle gas core NTRs, and they came away from their programs tearing their hair out at how many problems would be solved if only there were a way to do extensive criticality and containment experiments - something well within the capabilities of a modestly expanded NCERC. Both of us know that's not going to happen anytime soon, though, and unfortunately if it was propulsion systems should probably be well down on the list - Gen IV reactors need a TON of work to be ready for deployment, and they probably should have priority.

My favorite near-term design is the LARS out of Brookhaven, but you want to talk about a testing nightmare to qualify the fuel elements: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19910012832.pdf
Establishing criticality thresholds, bootstrapping methods, and the like would be unlike most things we've ever looked at in any depth, but it seems like such an elegant system (and at 1900 s isp, a game changer), with very little outside the fuel elements themselves that would need extensive testing.

Either that or Borowski's LANTR: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20170009140.pdf
TRITON is also attractive for near-term, but balance-of-plant issues seem like they would be a major challenge: http://alternatewars.com/BBOW/Space_Engines/AIAA-2004-3863_TRITON.pdf

Any of these designs would open up the inner Solar System out to the Main Belt for... well, whatever we want to do. Getting past the Belt gets harder in any near-term system, though... at least in any timeframe that humans would want to endure without artificial gravity and a quite extensive ship.

Offline john smith 19

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Re: NASA to make announcement concerning the Kilopower project
« Reply #54 on: 05/13/2018 07:28 PM »
I wonder... is there anything you can think of along these lines to replace the quartz in a nuclear lightbulb? The silicon mirrors are obviously too thermally limited, but... it's always been a favorite design of mine, despite the incredible mass of the system.
AIUI the Quartz envelop is GH2 cooled which, depending on wheather the design is open or closed, generates a substantial amount of the thrust.

The obvious choice beyond quarts is Zirconia.
The problem with controlled emittance and absorbance surfaces is they tend to have limited operating wavelengths, and I think what you're looking (not far off a fission heated plasma) at is a broadband "black body" emitter. 
The problem with materials for high power optical applications is how clear the glass is?
At high powers even (apparently) very clear glasses will absorb enough energy to shatter. IIRC the glass for the amplifier stages of the National Ignition Facility was a major PITA to produce in such large pieces with such high clarity.
Do you want to reflect the heat back in, or let it pass into a coolant as easily as possible?
Logically you want the reflector layer on the outer wall, to reflect the light back into the coolant layer.
Quote from: BeyondNERVA
I couldn't agree more. Unfortunately, the vast majority of systems with even 1/10th of that capability are so far down the TRL spectrum that it's rather depressing, and often only due to readioillogical fears preventing testing. I've been lucky enough to make friends with a couple people who were students looking at vapor core and open cycle gas core NTRs, and they came away from their programs tearing their hair out at how many problems would be solved if only there were a way to do extensive criticality and containment experiments - something well within the capabilities of a modestly expanded NCERC. Both of us know that's not going to happen anytime soon, though, and unfortunately if it was propulsion systems should probably be well down on the list - Gen IV reactors need a TON of work to be ready for deployment, and they probably should have priority.

My favorite near-term design is the LARS out of Brookhaven, but you want to talk about a testing nightmare to qualify the fuel elements: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19910012832.pdf
Establishing criticality thresholds, bootstrapping methods, and the like would be unlike most things we've ever looked at in any depth, but it seems like such an elegant system (and at 1900 s isp, a game changer), with very little outside the fuel elements themselves that would need extensive testing.

Either that or Borowski's LANTR: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20170009140.pdf
TRITON is also attractive for near-term, but balance-of-plant issues seem like they would be a major challenge: http://alternatewars.com/BBOW/Space_Engines/AIAA-2004-3863_TRITON.pdf

Any of these designs would open up the inner Solar System out to the Main Belt for... well, whatever we want to do. Getting past the Belt gets harder in any near-term system, though... at least in any timeframe that humans would want to endure without artificial gravity and a quite extensive ship.
LARS, being liquid phase rather than vapor phase, seems a good deal easier to test, but still no picnic.  :(

The problem with all nuclear systems is the attitude that failure is not an option.

The nuclear equivalent of SpaceX's first 3 F1 launches exploding (reactor designs melting down?) and the CEO saying "Well, we learned a lot more this time round and our next reactor won't explode" is (literally) unimaginable IRL.  :(

Throw in the desperately  poor T/W of current NTR designs to date and it look like you're in a very nasty crevice in the optimization landscape, difficult to improve without taking risks, difficult to take risks (even by other industries standards, quite small ones) in the first place.

This is what makes the Kilopower's team of getting to a live reactor test for 10s of $m such an extraordinary feat of both management and engineering skills, as they negotiated their way through the massive H&S issues around modern nuclear testing.
[EDIT
The LARS paper cites an earlier one by AV Grosse on how to construct such a spinning furnace (Science 1963) which I was able to get hold of. Most of the designs are horizontal but the photograph showed a vertical autoclave.

The trouble with LARS is that everything is a gradient, and most of them are quite extreme. It's got an acceleration vector top to bottom. It's spinning. You have a molten layer you need to immobilize without slippage or vaporizing too much into the GH2. There are radiation and neutron gradients heating the fuel (and everything else). That molten layer has an SG of about 19 and there are seven of these all spinning at the same time. and that's before we get to what you're going to make the nozzle out of now you've your 5-6000K dissociated Hydrogen gas flow.

Propellant slosh in main tanks with fluids with SG's near 1 have cause LV failures. On the upside I'd guess you can do some TVC just by varying the relative spin speeds of the seven pipes. No I wouldn't like to work out the maths for that.

No doubt there is much glorious fun to be had developing the maths to handle such a problem.
AFAIK the nearest to this is a bunch of work the US army did on artillery shells with fluid fillings in the 1000s of RPM range. Obviously their density was much closer to water than Uranium.  The Isp is impressive relative to all conventional systems. More so is that this looks like a high thrust system as well, which are much rarer (only solid core NTP and Orion look capable of that combination without some magic physics)
AFAIK the LARS apper dates from the early 90's so another 25 years of processor enhancement should have made the simulation significantly more tractable. ]
« Last Edit: 05/14/2018 06:22 AM by john smith 19 »
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Offline A_M_Swallow

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Re: NASA to make announcement concerning the Kilopower project
« Reply #55 on: 05/13/2018 10:38 PM »
{snip}
The problem with all nuclear systems is the attitude that failure is not an option.

The nuclear equivalent of SpaceX's first 3 F1 launches exploding (reactor designs melting down?) and the CEO saying "Well, we learned a lot more this time round and our next reactor won't explode" is (literally) unimaginable IRL.  :(

Throw in the desperately  poor T/W of current NTR designs to date and it look like you're in a very nasty crevice in the optimization landscape, difficult to improve without taking risks, difficult to take risks (even by other industries standards, quite small ones) in the first place.

This is what makes the Kilopower's team of getting to a live reactor test for 10s of $m such an extraordinary feat of both management and engineering skills, as they negotiated their way through the massive H&S issues around modern nuclear testing.

One day you may be able to test nuclear engines on the Moon.

Offline john smith 19

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Re: NASA to make announcement concerning the Kilopower project
« Reply #56 on: 05/14/2018 06:37 AM »
Sorry it took me so long to respond... 1000+ things going on right now.
Not a problem.
Quote from: BeyondNERVA link
Yes, it's talked about in terms of spaceflight, but... it's got a non-Carnot-based PCS by default as its' primary PCS, and as a side effect, you get isotopic enrichment of EVERY fission fragment FOR FREE! Really, that seems like the holy grail (and a containment challenge, but an easily solvable one) for a hospital: you can get plenty of gamma sources of ANY intensity for gamma knife or gamma-isotopic therapy, separate out the pure alpha and beta isotopes for therapies that can be delivered by pneumatic tube, so if you've got an hour's half-life that isn't a deal-killer (because the sucker is in the basement), and any beamline you WANT, including neutron, is readily available!
You're seeing "Direct conversion from fuel to electricity" which is admirable.
But sadly in the times in which we live a lot of people will just see "Dirty bomb waiting to happen."  :(

Uranium powder will burst into flames on contact with air. Obviously UO2 powder has already done this reaction but the fact remains it would be highly toxic even if it was not radioactive.

While that might be an acceptable risk for an upper stage or deep space reactor (with very strong pre-launch security), on Earth that sort of possibility makes people much more twitchy.

IRL I consider such threats to be exaggerated but the cleanup if something did happen would take  centuries  :(
Consider the events in Oklahoma City in 2005 for the scale of explosion accessible to quite ordinary people. Uncommon and improbable, but sadly not impossible.

What I liked about the KRUSTY design is how monolithic it is and how simple (in principle) its recycling would be. No cladding to strip off, no pellets to reduce to pure metal. A question of wheather you can build a big enough induction furnace and handle the waste gases and dross.
« Last Edit: 05/14/2018 06:39 AM by john smith 19 »
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. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline ThomasGadd

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Re: NASA to make announcement concerning the Kilopower project
« Reply #57 on: 05/15/2018 03:49 PM »
The Kilopower series appears the be designed to produce electricity such as nuclear electric propulsion.  Can it be used in a nuclear thermal system?

Offline speedevil

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Re: NASA to make announcement concerning the Kilopower project
« Reply #58 on: 05/15/2018 04:02 PM »
The Kilopower series appears the be designed to produce electricity such as nuclear electric propulsion.  Can it be used in a nuclear thermal system?
Yes, but the temperatures are so low, and the ISP is so low due to that, and the power output is so low that it is somewhat better than an ion engine in terms of thrust, and at best on a par with hypergolics.

If you can come up with a scenario where for example you have free water, can't electrolyse it for some reason, and need a few hundred m/s delta-v over a week or so, it may have a point.
Outer planet comet hopper?

Otherwise you need _lots_ more power for meaningful thermal rockets, as well as for them to get a whole lot hotter.

Offline A_M_Swallow

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Re: NASA to make announcement concerning the Kilopower project
« Reply #59 on: 05/16/2018 01:06 AM »
The Kilopower series appears the be designed to produce electricity such as nuclear electric propulsion.  Can it be used in a nuclear thermal system?
Yes, but the temperatures are so low, and the ISP is so low due to that, and the power output is so low that it is somewhat better than an ion engine in terms of thrust, and at best on a par with hypergolics.

If you can come up with a scenario where for example you have free water, can't electrolyse it for some reason, and need a few hundred m/s delta-v over a week or so, it may have a point.
Outer planet comet hopper?

Otherwise you need _lots_ more power for meaningful thermal rockets, as well as for them to get a whole lot hotter.


Kilopower is sufficiently hot that after generating electricity its waste heat can boil nitrogen and argon. Proving a probe with both thrust and power.

The waste heat could be used to cook food and make coffee. It gets very cold on the Moon so the heat can warm the inside of rovers and habitats.

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