2020's nuclear thermal propulsion efforts

[RON_P]

It seems like in recent years there is a new push by NASA and the DOD to develop NTR for mars and cislunar applications  and especially the Particle Bed HELU kind ( or in other words project timberwind/SNTP second chance ?) .
https://breakingdefense.com/2020/02/darpa-doubles-dough-for-nuclear-powered-cislunar-rocket/ .
Plus NASA recent report on their effort https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20190032440.pdf ( taken from NASA NTRS) .
Also there seems to be a thought for a second gen system that uses a Centrifugal Gas Core Reactor ?! https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20190032556.pdf ( look at page 8 ) .

[Eric Hedman]

There was the following article about $125 million added to the budget for this back in May:

https://www.digitaltrends.com/cool-tech/nasa-nuclear-thermal-125m/

[RON_P]

Hopefully the new program will go beyond NERVA achievements or especially Timberwind/SNTP .
America could have had a flyable NTR back in the 70's . Today with modern materials you could build an NTR with an ISP approaching  1000 seconds or higher and with T/W higher than 10 .

[Eric Hedman]

This article says they want a demonstration flight in 2024:

https://spacenews.com/momentum-grows-for-nuclear-thermal-propulsion/

[john smith 19]

This article says they want a demonstration flight in 2024:

https://spacenews.com/momentum-grows-for-nuclear-thermal-propulsion/

For $125m.

It cost the Kilopower team about $65m to get to a 1Kw nuclear power reactor. That was only possible by a very motivated team pursuing all avenues of partnership and funding to make it work.

Note that NASA asked for no money to pursue this as a separate line item, suggesting it is entirely driven by Congress.

Would an upper stage engine with an Isp of 1000sec be useful? Yes

Can NASA develop it for $125m. No. 

[RON_P]

First of all it's much more than 125 million but more like 350 million if count from 2017 to 2020 ( not counting DARPA or maybe some DOE contribution which is already more than what was allocated to Timberwind/SNTP program ).
Yes it's true it was pushed by the congress , but for the first time in NASA proposed FY21 white house budget there is a specific money allocation toward the development of space nuclear power ( NTR + kilopower ) and cryofluid management ( i.e hopefully zero boiloff tanks ) https://www.nasa.gov/sites/default/files/atoms/files/fy2021_congressional_justification.pdf ( look at page 169 ) .

[john smith 19]

First of all it's much more than 125 million but more like 350 million if count from 2017 to 2020 ( not counting DARPA or maybe some DOE contribution which is already more than what was allocated to Timberwind/SNTP program ).
Yes it's true it was pushed by the congress , but for the first time in NASA proposed FY21 white house budget there is a specific money allocation toward the development of space nuclear power ( NTR + kilopower ) and cryofluid management ( i.e hopefully zero boiloff tanks ) https://www.nasa.gov/sites/default/files/atoms/files/fy2021_congressional_justification.pdf ( look at page 169 ) .

Firstly welcome to the site.

I'd expect the vast majority of that money will go to developing a fully engineered Kilopower reactor for surface power on the moon or mars. Currently Kilopower uses HEU. This was readily available to the staff at Los Alamos during design but is highly problematical for orbital launch and would be expected to be replaced by LEU, which is also discussed in the NTR work.

As for ZBF it's been known since Robert Braun's major presentation that better cryo management could cut mass to orbit for a Mars mission by sixty percent.

Even nuclear can't cut the mass to LEO necessary for a Mars mission as much as that.  Zero (or very low) boil off is just a very good idea all round.

NASA' repeated failure to run a flight demonstration of on orbit cryo management reflects very badly on an organization supposedly deeply committed to exploration.    Doing such a demonstration with LH2 was always going to be difficult but isn't doing difficult things a NASA's goal?

Time will tell how much of this new money actually materializes.  While I think a flight demo of Kilopower by 2024 is quite possible (although transitioning to LEU might be difficult)  a flight demo of a new NTR design is ambitious. An LH2 turbo pump is a non trivial design task.

A 10Kw Kilopower reactor would be a formidable power source for an ion thruster as well as surface power, although radiator design is quite tough.

[edzieba]

For an NTR, the budget line-item to look out for is funding for building the test stand.
 NRDS has long been decommissioned, and direct-discharge of reaction-product-contaminated exhaust into the atmosphere would not fly today. That means new construction of a test stand:
- Capable of hosting and nuclear reactors with minimal inherent shielding (i.e. basically needs to be in the middle of nowhere and ideally a site with existing security in place)
- Capable of capturing exhaust products, scrubbing and sequestering them
- Capable of altitude operation (likely using a steam ejector, which would aid in capture of exhaust products)

NRDC may be a viable site if the hot cells are still viable, but the rest of the site would need buildup essentially from scratch.

[RON_P]

Off course they will build a new test stand from scratch . Just like the DOE with their new proposed fast neutron test reactor i.e the so called versatile test reactor (VTR) instead of repairing the FFTF .

[RanulfC]

Off course they will build a new test stand from scratch . Just like the DOE with their new proposed fast neutron test reactor i.e the so called versatile test reactor (VTR) instead of repairing the FFTF .

The research teams have been constantly updating the plans for a new test facility as this keeps popping up every few years but the sticking point is that the facility will likely cost more than the research or the engine and Congress will usually balk at the outlay.

The two main issues are the same as always: Congress wont' pay for it and the public won't accept it

Randy

[TrevorMonty]

Podcast on this subject, not listen to it yet.

http://fiso.spiritastro.net/telecon/Kokan-Joyner_6-3-20/

[dglow]

Podcast on this subject, not listen to it yet.

http://fiso.spiritastro.net/telecon/Kokan-Joyner_6-3-20/

Interesting, looks like AJR is pivoting to NTR.

[TrevorMonty]

Podcast on this subject, not listen to it yet.

http://fiso.spiritastro.net/telecon/Kokan-Joyner_6-3-20/

Interesting, looks like AJR is pivoting to NTR.

For cost of developing NTR we could have lunar ISRU plant that would give low cost fuel at EML1. Hydrolox engines are reliable, light and cheaper compared to NTR especially with EML1 refuelling for Mars missions.
There also SpaceX SS to consider which NASA wouldn't need to spend $Bs developing.

[RotoSequence]

Podcast on this subject, not listen to it yet.

http://fiso.spiritastro.net/telecon/Kokan-Joyner_6-3-20/

Interesting, looks like AJR is pivoting to NTR.

For cost of developing NTR we could have lunar ISRU plant that would give low cost fuel at EML1. Hydrolox engines are reliable, light and cheaper compared to NTR especially with EML1 refuelling for Mars missions.
There also SpaceX SS to consider which NASA wouldn't need to spend $Bs developing.

If cislunar space becomes a commercial economic zone in a politically competitive geostrategic future, it will accordingly need to be defended by the military. The large Delta-V budgets of nuclear thermal rockets are invaluable in this use case.

[Lodrig]

Complete waste of money, Solar Electric propulsion is superior for virtually every conceivable use scenario, particularly the High Delta-V missions. 

For cis-lunar space where transfers to-from the lunar surface and various lunar and high-Earth orbits are often ~2km/s, the ISP of a NTP simply isn't high enough to produce a propellant fraction saving with would outweigh the heavy mass of the engine and the bulky low density hydrogen tanks.

For example

2.5km/s DeltaV with HydroLox 450 ISP, propellant fraction 44%
2.5km/s DeltaV with NTP 900 ISP, propellant fraction 25%

Savings 19% propellant fraction, but now all propellant mass is H2 so bulk density drops to 71 kg/m^3, about 1/4th that of a Hydro-LOX mix, so tank sizes actually increases by a factor of 2.2.  That will eat up several percent dry mass and then the engine the rest.

With SEP at 5k ISP and same DeltaV, propellant fraction is 5%, at high density, and much of your engine mass is actual a solar array that can power the mission hardware when you reach the destination.

[RotoSequence]

Complete waste of money, Solar Electric propulsion is superior for virtually every conceivable use scenario, particularly the High Delta-V missions. 

For cis-lunar space where transfers to-from the lunar surface and various lunar and high-Earth orbits are often ~2km/s, the ISP of a NTP simply isn't high enough to produce a propellant fraction saving with would outweigh the heavy mass of the engine and the bulky low density hydrogen tanks.

For example

2.5km/s DeltaV with HydroLox 450 ISP, propellant fraction 44%
2.5km/s DeltaV with NTP 900 ISP, propellant fraction 25%

Savings 19% propellant fraction, but now all propellant mass is H2 so bulk density drops to 71 kg/m^3, about 1/4th that of a Hydro-LOX mix, so tank sizes actually increases by a factor of 2.2.  That will eat up several percent dry mass and then the engine the rest.

With SEP at 5k ISP and same DeltaV, propellant fraction is 5%, at high density, and much of your engine mass is actual a solar array that can power the mission hardware when you reach the destination.

There's no magic rule about nuclear engines that says that you can only use hydrogen as your propellant. Throw methane in there if you want better bulk density and more delta-V.

[butters]

Why not both? The private sector can develop SEP and ISRU so that the government can marshal its resources to tackle nuclear propulsion and space-rated nuclear power. Just about any kind of propulsion or propellant system except for nuclear is now within the capability of commercial spaceflight. For the government to completely foot the bill for anything other than nuclear propulsion would be the waste of money.

[RON_P]

Also there is the the DOD and DARPA project https://www.darpa.mil/program/demonstration-rocket-for-agile-cislunar-operations .
Is this a new  SNTP/TIMBERWIND  ?
Furthermore i am a bit confused Seems like the DOD project is pursuing a TRISO fueled 3D printed NTR ( maybe even a particle bed one for a a very high T/W ratio and an ISP greater than 1000 sec ) like this  Oak ridge project https://tcr.ornl.gov/ . While NASA is pursuing a more ''conservative'' design with a CERMET fueled NTR  for now maybe later with Carbide fuels ( or even joining the DOD program)  .

[Lodrig]

Why not both? The private sector can develop SEP and ISRU so that the government can marshal its resources to tackle nuclear propulsion and space-rated nuclear power. Just about any kind of propulsion or propellant system except for nuclear is now within the capability of commercial spaceflight. For the government to completely foot the bill for anything other than nuclear propulsion would be the waste of money.

Nope, most SEP research is still government funded for one, just because commercial interests can also contribute doesn't mean government effort should cease.  NASA still dose huge amounts of Aeronautics research which is then farmed out to the industry to make it help make it competitive on the world market.

NTP and especially nuclear-power in space are a waste because neither civilians nor governments will have any use for such a device regardless of who were to develop it.

[dglow]

Why not both? The private sector can develop SEP and ISRU so that the government can marshal its resources to tackle nuclear propulsion and space-rated nuclear power. Just about any kind of propulsion or propellant system except for nuclear is now within the capability of commercial spaceflight. For the government to completely foot the bill for anything other than nuclear propulsion would be the waste of money.

Nope, most SEP research is still government funded for one, just because commercial interests can also contribute doesn't mean government effort should cease.  NASA still dose huge amounts of Aeronautics research which is then farmed out to the industry to make it help make it competitive on the world market.

NTP and especially nuclear-power in space are a waste because neither civilians nor governments will have any use for such a device regardless of who were to develop it.

That'a a rather broad statement; every RTG-powered probe we've sent and the Curiosity and Perseverance rovers would choose to disagree. The idea behind low-enriched Uranium-based reactors is about working with safer, less-controlled fuel with an eye to broadening the use of such power sources. See Kilopower.