Author Topic: NASA boosts nuclear thermal propulsion with BWXT contract  (Read 8315 times)

Offline TrevorMonty

Humanity will never do anything truly substantial in space until it uses NTR of some type.
I have always been an avid supporter of NTR technology so this is really good news.

Really?
As long as you are not able to simply refuel at destination it will not open the Solar System.
And expendable architectures will not get us anywhere in the long run.
Careful now. This is a little more subtle than it looks.

In an NTR propellant is reaction mass. The core could (should?) be capable of multiple burns.

So the question is (with current designs) is there a source of LH2 at the destination?  Could be (in principle) Ammonia, Water or Methane (CO2 ?) as well.
Deliver return fuel with SEP, doesn't matter if it takes a year or two to get there.

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 6186
  • Everyplaceelse
  • Liked: 826
  • Likes Given: 5146
Re: NASA boosts nuclear thermal propulsion with BWXT contract
« Reply #41 on: 08/22/2017 05:57 AM »
No, they said " a nuclear thermal rocket has double the propulsion efficiency of the Space Shuttle main engine"  which means ISP and not thrust
Which sounds about right, given the SSME is about Isp 450 and NTR is about 900secs.

OTOH An SSME thrust equivalent NTR would be an absolute monster, with a budget requirement to match.  :(
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline Propylox

  • Member
  • Posts: 81
  • Colorado
  • Liked: 6
  • Likes Given: 7
Re: NASA boosts nuclear thermal propulsion with BWXT contract
« Reply #42 on: 09/13/2017 05:08 AM »
-snip- Weapons grade Uranium is no longer an option for NTR but you still want it to be small, so the plan is to make it small by running at the top end of LEU and stripping out all the moderator. It is now a fast spectrum reactor (and in principal a breeder as well with this spectrum). However AFAIK no one's actually done this before which is what this design exercise is all about.
No one has built such an NTR, but LEU fast breeders have been around for a while - in Russia. They even produce experimental fuels for other countries as well as their own constantly-developing designs. Considering NTRs have long been politically impossible in the US, this program seems like cover for catching up with our nuclear power technologies and expertise base.

PS-
A previous comment correcting all the inaccuracies and consistent contradictions in JS19's post was erased and I was banned temporarily for being accurate and helpful. Rather than recorrect it now, you guys can stay ill-informed. Your system, your loss.
« Last Edit: 09/13/2017 05:13 AM by Propylox »

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 6186
  • Everyplaceelse
  • Liked: 826
  • Likes Given: 5146
Re: NASA boosts nuclear thermal propulsion with BWXT contract
« Reply #43 on: 09/13/2017 09:16 AM »
No one has built such an NTR,

If you mean that no nation has put an NTR into orbit that would be correct.

OTOH the US ran a very substantial NTR development programme from about 1958 to 1973 and fired a number of them into the atmosphere at a place called "Jackass Flats."

IIRC at least one of them was close to flight weight.

Are you unaware of this?

Quote from: Propylox

but LEU fast breeders have been around for a while - in Russia. They even produce experimental fuels for other countries as well as their own constantly-developing designs. Considering NTRs have long been politically impossible in the US, this program seems like cover for catching up with our nuclear power technologies and expertise base.

Nuclear power is especially challenging in the US (the "no reprocessing" rule. I can't really get my head around that one, for example  :( ).
 Nuclear power for rocket propulsion even more so.  :( As for "politically impossible," I guess NASA are optimists.  :)
Part of softening that attitude to NTR would be to make (to the layman) an NTR look less  like a nuclear bomb that's a hairs breadth away from going bang
(let me repeat, "to a layman." I'm quite well aware that there are plenty of safeguards built in, starting with the fuel and its cladding). IOW not having an engine that mandates "bomb grade" fuel.

To have a chance of running, and continuing to run, any such programme would need to support a number of goals. "Improving (or sustaining) US competitiveness" is fairly standard language when something like this is looking for an appropriation, even if it's only for a design study. I had not realized you are not from the US, (but then neither am I) and might not be aware of this.


OTOH the US is just as prone to "Not Invented Here" syndrome as anywhere else. Consider how long it has taken for them to consider doing an Oxidizer Rich Staged Combustion engine, for example.  :(

On a personal note welcome back to the site.
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline bradjensen3

  • Member
  • Posts: 50
  • Tulsa, Oklahoma, USA
  • Liked: 3
  • Likes Given: 0
Re: NASA boosts nuclear thermal propulsion with BWXT contract
« Reply #44 on: 09/19/2017 08:03 PM »

The article states "Nuclear thermal power for spaceflight has a number of advantages over chemical-based designs, it said, primarily providing higher efficiency and greater power density resulting in lower propulsion system weight"

It is about efficiency and power density.  No mention of thrust.

That is two places where you have misquoted/misunderstood an article.  I suggest a little more careful reading.

You are absolutely correct! Thank you for pointing out my misunderstanding!





Offline Katana

  • Full Member
  • **
  • Posts: 276
  • Liked: 27
  • Likes Given: 11
Re: NASA boosts nuclear thermal propulsion with BWXT contract
« Reply #45 on: 09/20/2017 02:04 AM »
-snip- Weapons grade Uranium is no longer an option for NTR but you still want it to be small, so the plan is to make it small by running at the top end of LEU and stripping out all the moderator. It is now a fast spectrum reactor (and in principal a breeder as well with this spectrum). However AFAIK no one's actually done this before which is what this design exercise is all about.
No one has built such an NTR, but LEU fast breeders have been around for a while - in Russia. They even produce experimental fuels for other countries as well as their own constantly-developing designs. Considering NTRs have long been politically impossible in the US, this program seems like cover for catching up with our nuclear power technologies and expertise base.

PS-
A previous comment correcting all the inaccuracies and consistent contradictions in JS19's post was erased and I was banned temporarily for being accurate and helpful. Rather than recorrect it now, you guys can stay ill-informed. Your system, your loss.
Fast breeders are much more difficult on ground, let alone in space.

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 6186
  • Everyplaceelse
  • Liked: 826
  • Likes Given: 5146
Re: NASA boosts nuclear thermal propulsion with BWXT contract
« Reply #46 on: 09/20/2017 06:43 PM »
Fast breeders are much more difficult on ground, let alone in space.
True.

I think it's important to separate the idea of a "fast" spectrum reactor and a "breeder" reactor with low breeding or high breeding.

Once you strip all that graphite out of the design I think it's quite difficult for any reactor to remain a thermal spectrum system. IRL most PWR's have been "breeding" fuel for decades, in the sense of turning U238 into Pu and some of that fissioning in situ, improving reactor burnup. More a tweak in the ConOps, rather than a full re-design for breeding.

But you're right few actual breeder reactors, designed to produce significantly more Pu than the U235 they've burnt, have been built.

Historically NTR have been HEU systems (98% U235 IIRC) so there's been no U238 to breed in the first place. Obviously this design changes that. We'll have to see how far it goes.
« Last Edit: 09/20/2017 06:44 PM by john smith 19 »
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Tags: