The National Aeronautics and Space Administration (NASA) has awarded BWXT Nuclear Energy a $18.8 million contract to initiate conceptual designs for a nuclear thermal propulsion reactor in support of a possible future manned mission to Mars. BWXT Nuclear Energy is a subsidiary of nuclear components, fuel and services provider BWX Technologies, which is based in Lynchburg, Virginia.The reactor, based on low-enriched uranium (LEU) fuel, would be part of a nuclear thermal propulsion (NTP) rocket engine designed to propel a spacecraft from Earth orbit to Mars and back. According to NASA, an NTP system can cut the voyage time to Mars from six months to four and "safely deliver human explorers" by reducing their exposure to radiation. That also could reduce the vehicle mass, enabling deep space missions "to haul more payload".:Part of NASA's Game Changing Development (GCD) Program, the NTP project "could indeed significantly change space travel", NASA said, largely due to its ability to accelerate a large amount of propellant out of the back of a rocket at very high speeds, resulting in a highly efficient, high-thrust engine. In comparison, a nuclear thermal rocket has double the propulsion efficiency of the Space Shuttle main engine, "one of the hardest-working standard chemical engines of the past 40 years". That capability makes NTP "ideal for delivering large, automated payloads to distant worlds", it said.
"BWXT is extremely pleased to be working with NASA on this exciting nuclear space program in support of the Mars mission," Rex D. Geveden, president and chief executive officer of parent company BWX Technologies, said in a press release. "We are uniquely qualified to design, develop and manufacture the reactor and fuel for a nuclear-powered spacecraft."
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.
Update. I found this on the NASA website for NTPhttps://gameon.nasa.gov/gcd/files/2016/05/FS_NTP_160525.pdf
One of the initial project goals is to purify Tungsten (the matrix material for the cermet designs) to 90% purity affordably, then to look at a reactor built with LEU at a regular engine test site IE Stennis). I'm baffled by this.
Initial project goals are to demonstrate the ability to purify tungsten to a minimum of 90 percent purity and determine the production costs at that purity level; to determine the technical and programmatic feasibility (pre-phase A level) of an NTP engine in the thrust range of interest for a human Mars mission; and to determine the program cost of an LEU NTP system and the confidence level of each major cost element.
I think it's fair to say that for this project to get beyond the Powerpoint stage it's going to take a lot of commitment from NASA
This seems like NASA dipping a toe in case they suddenly need to try and play catch-up to Russia. In 2016 Rosatom received experimental fuel for their NEP design, which began development around '09-'10, and are expected to unveil the prototype next year.It's a 4MWt ~ 1MWe high temperature gas-cooled fast reactor for 100-150kw nominal ion propulsion.
I don't know if this helps but they expand a little bit on this here:Quote from: page 2Initial project goals are to demonstrate the ability to purify tungsten to a minimum of 90 percent purity and determine the production costs at that purity level; to determine the technical and programmatic feasibility (pre-phase A level) of an NTP engine in the thrust range of interest for a human Mars mission; and to determine the program cost of an LEU NTP system and the confidence level of each major cost element.
Hmm, I wonder if the clue is in the phrase "isotopically pure tungsten" - do they just want one isotope? That does sound difficult and expensive.
That's the usual meaning and AFAIK you're right. For isotope sep you're talking exactly the sort of systems that do Uranium enrichment, which are specialized, complex and very expensive.
Would SILEX/laser enrichment schemes from uranium (re)processing be applicable here? I understood that the laser wavelength is output isotope specific so you can't use the same designs directly, but the basic principles should still apply, right?
Though there is the whole reprocessing taboo from the Carter era that made SILEX development run for so long. Trying to push SILEX tech for non-uranium use now may raise some technology dissemination concerns again.
Naturally occurring Tungsten has five stable isotopes...All of these isotopes can be enriched or depleted by URENCO to any required concentration. Using our centrifuge technology, concentrations can be enriched to exceed 99.9% or depleted below 1%.
Urenco actually offers isotope separation on elements other than uranium:https://media.urenco.com/corp-website/74/stableisotopes_2.pdf (p14)QuoteNaturally occurring Tungsten has five stable isotopes...All of these isotopes can be enriched or depleted by URENCO to any required concentration. Using our centrifuge technology, concentrations can be enriched to exceed 99.9% or depleted below 1%.
Quote from: Propylox on 08/08/2017 03:34 am4MWt ~ 1MWe high temperature gas-cooled fast reactor for 100-150kw nominal ion propulsion. (snips) The Russian NE is very big reactor by space nuclear standards ...Nuclear thermal is in the 100s of MW of thermal power ... and it converts heat directly into thrust with no intermediate conversion. That's important because radiators in space are true radiators. The more efficient your generator the lower its waste output temperature and the bigger the radiator you need. For any system there will a "break even" mass where making the generator 1% more efficient increases the radiator mass too much to be worth it.
4MWt ~ 1MWe high temperature gas-cooled fast reactor for 100-150kw nominal ion propulsion.
... The reactor, based on low-enriched uranium (LEU) fuel, would be part of a nuclear thermal propulsion (NTP) rocket engine ... In comparison, a nuclear thermal rocket has double the propulsion efficiency of the Space Shuttle main engine ...
Well aware, as I'm sure you are that the higher the temperature - the faster the heat transfer through radiance and convection.
Rosatom's fast reactor design's high temperature therefor needs smaller radiators to create the working fluid's temperature differential for power production.
NASA's NTP would traditionally use high temperatures to excite the propellant as quickly as possible - but they call it a "reactor" instead of a "core" and set a relatively low bar of ~900s isp, but which seems high for the LEU they've also proposed. That's curious.http://www.world-nuclear-news.org/ON-NASA-boosts-nuclear-thermal-propulsion-with-BWXT-contract-04081701.htmlQuote... The reactor, based on low-enriched uranium (LEU) fuel, would be part of a nuclear thermal propulsion (NTP) rocket engine ... In comparison, a nuclear thermal rocket has double the propulsion efficiency of the Space Shuttle main engine ... Whatever NASA is envisioning, it'll need to produce electricity (turbine, stirling, thermoelectric) and for reliability/efficiency purposes will probably use a working fluid. No surprises there.With LEU they'll need to increase nuclear activity (temperature) right before the throat after the propellant spends considerable time circulating around the core, building temperature. This choice of LEU adds incredible complexity to the design while decreasing its performance - so why do it?
Quote from: Propylox on 08/10/2017 02:18 am Rosatom's fast reactor design's high temperature therefor needs smaller radiators to create the working fluid's temperature differential for power production. True, but you sacrifice efficiency because you can only use a limited amount of that high temperature if you want the waste heat temp to be high. Conversion efficiency Vs radiator weight impacts overall system efficiency.
(snips) Historically reactor flow through they NASA cores has been pretty simple. In one end, out the other. I'd expect a longer core. ... The temperature of the reactor vessel is like that of a rockets thrust chamber so it's regeneratively cooled. Piping some of that flow through a generator would be no problem. The issue is with the reactor shut down can you get enough heat of the core without a propellant flow between the core and the walls to extract the heat? Personally I like heat pipes. They can move a lot of heat and they can be made one way and switchable. IE turned off while the reactor is running but switched on to extract decay heat for electrical power.
AFAIK HEU (or "weapons" grade) is quite cheap, hence it's interest by the Kilopower team. IOW in principal going LEU saves a lot of money
1) An earlier report on the subject said that Graphite Composite fuels had much more maturity than cermets (20 reactors built Vs no cermet unit ever tested, not a trivial difference in this field). One of the initial project goals is to purify Tungsten (the matrix material for the cermet designs) to 90% purity affordably, then to look at a reactor built with LEU at a regular engine test site IE Stennis). .. and ..But TBH I did not realize there was any problem with W purity to begin with, unlike say the issue of all commercial Mo (low capture cross section) having enough Hf (high capture cross section) in it to affect its use in nuclear applications without serious processing.2) Going from HEU to LEU will make the core larger. I can only presume they think a thermal spectrum reactor (all that graphite makes it a thermal reactor, epithermal at most) will be simply too large to launch (IE from 97% U235 to <20%) and the only way to cope with the reduction is to go with a fast reactor, hence the cermet approach.