A revival of interest in Nuclear Thermal Propulsion?

Oldfart1939 · 2017-11-09 23:00:37

In a recent article on space.com, there seems to be interest growing in a revival of the 1970's technology as in the NERVA system. Here's the link to the How Vintage Rocket Tech Could Be NASA's Ticket to Mars and Beyond article:

aHR0cDovL3d3dy5zcGFjZS5jb20vaW1hZ2VzL2kvMDAwLzA3MS81OTAvb3JpZ2luYWwvbnVjbGVhci10aGVybWFsLXJvY2tldC5qcGc=

Nuclear thermal rockets like the one in this artistic rendering could halve the time needed for a Mars mission.

Fixed link and added the image, I hope you don't mind
Fixed as indicated in post by member 3015....

elderflower · 2017-11-10 06:00:38

and could a BFR put one into LEO so that it and its propellant could be mated with a Mars transfer ship? This would avoid having an operational reactor in the Earth's atmosphere.

RobS · 2017-11-10 06:45:00

All that is possible. But if Space X brings about a huge cost revolution in launching stuff to low Earth orbit, it could get people to Mars in 3 months or less with chemical propulsion at a reasonable price. Space X doesn't need nuclear, IF they bring about the cost revolution they are aiming for. Nuclear could still be used with it, but it would take a long time to make up for the large up-front development cost.

louis · 2017-11-10 07:25:32

I agree Rob.

If you have to go nuclear then go Orion...atomic bomb pulses...accelerating your craft to 150 Km per second or 13 million miles per day (so maybe 6 days to get to Mars) or 4.7 billion miles pa...take a mere 5000 years to get to our nearest star.

RobS wrote:

All that is possible. But if Space X brings about a huge cost revolution in launching stuff to low Earth orbit, it could get people to Mars in 3 months or less with chemical propulsion at a reasonable price. Space X doesn't need nuclear, IF they bring about the cost revolution they are aiming for. Nuclear could still be used with it, but it would take a long time to make up for the large up-front development cost.

elderflower · 2017-11-10 11:40:50

A great deal of development was done in the USA and in the USSR, including run tests of Nuclear thermal engines. I don't think we need these for Mars, but if humans are to go further out than the moons of Jupiter we will have to have something with higher performance than chemical rockets as risks to health build up with transit time.

Oldfart1939 · 2017-11-10 12:27:10

In the 1970s, the NERVA program had an operationally useable engine that was simply shelved due to the Nixon cutbacks in space spending. What is poorly understood by the present generation is the reasoning behind these cutbacks. Nixon had his ultimate revenge on John Kennedy by just about killing the space legacy of his hated political opponent.

That all is behind us now. In the 1970s the Isp for the Kiwi engine using H2 as the "propellant," was 900 seconds. The new article states that newer alloys and structural materials allow higher operational temperatures which in turn, result in higher exhaust velocities and thus, higher Isp.

RobertDyck · 2017-11-10 13:33:28

The 1974 version of NERVA was fully complete, tested in a static test stand, all that was left was to test it in space. According to a 1968 film released by NASA, it was intended for a new stage to replace the 3rd stage of Saturn V as a TMI stage for a manned mission to Mars. The 1974 version of NERVA had Isp=850s in vacuum, Isp=380s at sea level. In 1991 they did a study with computer simulations. (Part of SDI.) That increased Isp to 925s in vacuum. The 1960s/1970s NERVA was intended to be launched into orbit with the reactor not started. Saturn V used the 3rd stage to circularize orbit, then a second burn for TMI. So this implies some sort of smaller chemical 3rd stage would be necessary to circularize orbit.

In 1969 the manufacturer of the F-1 engine for the 1st stage of Saturn V had completed development of F-1A, which produced 1.8 million pounds thrust per engine. F-1 for Apollo 4, 6 and 8 produced 1.5 million pounds and Isp=260s at sea level, for Apollo 9-17 produced 1.522 million pounds and Isp=263s. F-1A would have had the same Isp, and was a direct bolt-in replacement, so that means propellant would run out sooner requiring staging (starting the 2nd stage) that much sooner. They intended to use the 2nd stage unmodified. There were various proposals for Mars, but this sounds like they did significant development.

SpaceNut · 2017-11-10 14:51:28

The image that I added from the article to the first post and is article content is where Nasa is headed in the DRM 5.0 mission plan, to which Nasa is just kicking the can down the road.

RobertDyck · 2017-11-10 15:29:34

Thanks, but the link doesn't work for me. The image is an old one. An old idea with no real intention to go to Mars.

SpaceNut · 2017-11-10 16:47:50

Ya it fails in internet explorer 8 but works with firefox 48.0.2 and I agree that its old art and perspective of going to mars.

Where nuclear option was the answer by Nasa Design Reference Mission 5.0
Of course we had the oposite view in this topic Forget NTR, SEP is the Future

The company Nasa is paying for nuclear developement work is https://www.bwxt.com/news/featured/mission-to-mars

We have also talked about the fuel not being hydrogen that is liquified being the source to make it a better more capable mars rocket as CO2 would be more practical for Mars.

https://www.bwxt.com/what-we-do/nuclear … ulsion-ntp

NASA is projecting up to a 50 percent reduction in interplanetary travel times compared to chemical rockets.
Which would significantly increasing the crew's safety by reducing exposure to cosmic radiation.
The technology that is being developed...

LEU Nuclear Thermal Propulsion
Current development of 500 MW LEU CERMET fuel reactor for manned space applications.
Design of 19.75% Enriched Ceramic Metallic (CERMET) Tungsten-Clad fuel
Nuclear, thermal-hydraulics and mechanical design of the reactor
Licensing and design support for full-scale full-thrust ground test of the NTP engine
Space Nuclear Thermal Propulsion
Formerly classified advanced technology design to develop and test high-performance nuclear reactor rocket engine for military applications.
Particle bed fuel
Mechanical, nuclear and thermal-hydraulic design of the core
Reactor control and auxiliary systems
Small Ex-core Heatpipe Thermionic Reactor
Program to develop a nuclear reactor in the power range of 10 to 40 kW for space applications.
Mechanical and Nuclear Design of UO2-Tungsten Clad Fuel
Mechanical, nuclear and thermal design of the core and shield components
Design of the reactor control and reactor support systems
Extended reactor design to include propulsion (Bi-Modal) capability
Nuclear Thermal Rocket
Bi-Modal Reactor
Nuclear thermal rocket program to provide Bi-Modal propulsion capability for future human exploration missions to the Moon and Mars and generating electrical power for spacecraft systems.
Design studies for Various Fuel Types and Configurations including: PBR, UO2-Moly CERMET and Twisted Ribbon Ternary Carbide fuel forms
Mechanical, nuclear and thermal design of the various core configurations and shield designs

RobertDyck · 2017-11-10 18:30:12

I have Firefox ESR 52.2.1 (32-bit), still doesn't work. I'll update... now Firefox ESR 52.4.0 (32-bit), the latest version. Still says

Houston, we have a problem.
We’re sorry, but something went wrong.
If we can’t land you on the page you’re looking for, at least we can hook you around the moon in order to get you HOME.

But all the links for your latest post work.

In 1987, BWXT received a contract to design a space nuclear thermal propulsion (SNTP) system in support of the U.S. Department of Defense’s SNTP program. The program sought to develop a lighter and smaller second-generation, PBR-based nuclear rocket. While the program ceased at the end of the Cold War in 1993, the PBR was extensively tested and validated, signaling a giant leap forward in the size reduction of NTP engines.

Yea! They're talking about Timberwind. That's the low mass NTR that I've posted about so often. However...

Although previous nuclear propulsion concepts relied on high-enriched uranium, BWXT’s latest design utilizes low-enriched uranium-based fuel. In addition to determining the feasibility of using low-enriched fuel, the NTP project will also test and refine the manufacturing of the system’s fuel elements throughout the next year.

Well, that should undo any mass saving. Oh well.

SpaceNut · 2017-11-10 20:03:50

Possibly another ITAR marked article then, which really is not from what I am reading for its content; especially since you are able access the other...I have seen other problems with the java embedded code causing issues with firefox as well even with my computer.

Back to the nuclear power for rockets... I also read an article that indicated that the Small Nuclear reactor program was dropped by them...

RobertDyck · 2017-11-10 23:03:42

Java. Retrying on an iMac with OS X El Capitan version 10.11.6 and Firefox 56.0.2 (64-bit). Same problem.
Retrying with Safari version 10.1.2 (11603.3.8). Same problem.

3015 · 2017-11-10 23:47:27

Change the .htm in the address to .html, the link worked for me after doing that.

RobertDyck · 2017-11-11 00:25:59

That did it.

GW Johnson · 2017-11-11 12:11:27

Timberwind was the performance upgrade for NERVA that improved thrust/weight at the cost of not being restartable at all for a second burn (partial melting in the fluidized particle bed). NERVA as it was, was restartable multiple times. One of the problems for a nuke Mars mission is you need to restart the nuke about 2 or 3 times as a minimum. That would be for Mars capture and Mars departure, plus one more for Earth capture if you intend to recover anything but a crew in a capsule.

The talk from NASA in the old days (before that idiot Nixon killed it all) was NERVA-type nuclear thermal was baseline for a 1980's trip to Mars. Chemical was the backup, but at about 4 times the launched mass assembled in Earth orbit. The "preferred better option" at that time was the entirely untested gas core nuke, an open-cycle type with a spherical feed geometry at higher T/W than NERVA if operated only to 2500 s Isp, and dragged down to a fractional T/W by the waste heat radiators if operated at 6000 s Isp.

Neither the gas core engine design nor the radiator design was ever built and tested. The spherical flow scheme achieved adequate uranium confinement in benchtop plasma tests, and a uranium core in the gas phase was actually made critical and controlled in some other tests. The two were never combined into a single experiment.

So, in reality, it was NERVA as the prime, with chemical as the backup. Then Nixon killed it all in the middle of the planned Apollo landings. And NASA in its infinite wisdom killed NERVA, on the logic that "who needs the rocket if we aren't going to go?". That sort of logic was a preview of what has come to pass, actually.

The manned Mars mission was scheduled for the 1983 opposition during the earlier phases of Apollo in the mid to late 1960's. That had been pushed back to the 1987 opposition by the time Nixon killed everything.

GW

SpaceNut · 2017-11-11 12:49:25

sorry for that missing single character, the L has been added to that orginal link, thanks 3015 and RobertDyck for the efforts.
The http://www.differencebetween.info/diffe … ml-and-htm always learning about coding....

back the the nuclear thermal reactor powered rocket based on the old Nasa technology and current path contract funding to BWXT...

AS we were say nasa just can not seem to get out of the battlestar galatica or the 20 billion dollar price tag....

RobertDyck · 2017-11-11 12:51:54

GW Johnson wrote:

Timberwind ... (partial melting in the fluidized particle bed)

The particle bed was not fluidized. Liquid hydrogen flowed through pebbles of uranium, boiling to hydrogen gas. The problem was some spots between particles produced a gas bubble that stayed in place, preventing liquid hydrogen from cooling the pebble. This caused the face of both pebbles to overheat, causing that face to melt. This caused the pebbles to weld together, agglomerating the pebbles into a solid mass. That made the engine not restartable.

We need something that reduces reactor mass like Timberwind, but ensures the engine is restartable like NERVA. Timberwind had Isp=1000s, the 1991 study to update NERVA had Isp=925s. That difference was due to temperature. If a new reactor only produce 925s, good enough. We certainly don't have to go back to the 1972 or 1974 version of NERVA, or even the 1991 version. We should be able to apply technology from Timberwind to reduce reactor mass while ensuring it's restartable.

One problem is attempts to update NERVA have attempted to get the one reactor to produce electrical power as well as thrust. Combining too many different functions will dramatically increase mass. A single purpose engine should be much simpler, lower mass.

SpaceNut · 2017-11-11 19:53:52

Baffle plates inserted at specific distance with just the correct size and count of holes in each would help to stop what is called cavitation

Many fluids exhibit the chance for bubbles to occur.

http://www.machinerylubrication.com/Rea … -hydraulic

https://en.wikipedia.org/wiki/Cavitation

Quaoar · 2017-12-03 15:00:44

RobertDyck wrote:

We need something that reduces reactor mass like Timberwind, but ensures the engine is restartable like NERVA. Timberwind had Isp=1000s, the 1991 study to update NERVA had Isp=925s. That difference was due to temperature. If a new reactor only produce 925s, good enough. We certainly don't have to go back to the 1972 or 1974 version of NERVA, or even the 1991 version. We should be able to apply technology from Timberwind to reduce reactor mass while ensuring it's restartable.
.

The tricarbide foam core should have a T/W of 35, even better than the Timberwind, without the hotspot problem

https://www.osti.gov/scitech/servlets/purl/1266203

https://ntrs.nasa.gov/archive/nasa/casi … 011256.pdf

There are a lot of very interesting study about modern NTR with new material, but nobody seems really interested in build them

tahanson43206 · 2020-11-08 09:30:50

This post is offered in Oldfart1939's topic, primarily because it involves Nuclear fission, Thermal energy, and Propulsion.

However, ** this ** post is an inquiry into an approach I have not seen discussed before. That certainly does NOT mean it has not been discussed before, so if someone posts a link to earlier work, I'd appreciate it.

The idea offered here is to use nuclear fission to disassociate water into oxygen and hydrogen, and then burn ** those ** to make traditional chemical propulsion at the familiar and reliable 421 seconds ISP.

Google Search:

at what temperature does water dissociate into hydrogen and oxygen
About 22,600,000 results (0.69 seconds)
Image result for at what temperature does water dissociate into hydrogen and oxygen
2200 °C
Thermal decomposition of water
In thermolysis, water molecules split into their atomic components hydrogen and oxygen. For example, at 2200 °C about three percent of all H2O are dissociated into various combinations of hydrogen and oxygen atoms, mostly H, H2, O, O2, and OH.
Water splitting - Wikipedia

Can a fission reactor be run for an extended period at that temperature?

Water is a particularly stable form for long term storage of useful mass in a space going vessel

I'm thinking primarily of the design of a pusher tug for the Earth-Mars loop. A pusher tug would give a fully fueled space ship the shove it needs to embark upon a Hohmann transfer, without consuming any of the fuel or oxidizer on board. The benefit is that the vehicle can use that propellant to "dock" with Mars, instead of risking life and property in an encounter with the wispy atmosphere of Mars.

Such a pusher tug could be put into immediate service launching probes to Mars, because the vehicles would arrive with enough propellant to land safely on Mars without all the Rube Goldberg mechanisms currently needed.

(th)

SpaceNut · 2020-11-08 10:39:50

This is the heart of the DRM 5 topic that Nasa is continually kicking down the road as a result of the nuclear material issues....
Its hard enough to get a small amount onboard the deep space probes let alone a larger ship.....
Its also some that we know we need the deeper into space we go is reliable nuclear created power....

tahanson43206 · 2020-11-08 12:14:47

For SpaceNut re #22

Thank you for adding to this topic!

While I agree that financing a venture along these lines would depend upon the value of the materials to be collected, another important factor is the cost of the propulsion system.

I recalled that Calliban had done Masters work in the field of nuclear power, and found the reference here:
http://newmars.com/forums/viewtopic.php … 09#p172309

I am hoping that Calliban might be willing to evaluate the proposal as given in Post #21 ...

There are several aspects to the proposal that I am unsure about:'

1) Can a fission reactor even ** run ** at the temperatures needed for disassociation of water for an extended period?
2) Can the products of the action (disassociation) be collected separately?
3) Given that burning Oxygen and Hydrogen can yield chemical thrust, is it feasible to develop a decent ISP using gaseous inputs?
4) Given that the disassociated elements are already hot, do they have to be cooled before it makes sense to burn them for thrust?

It may well turn out that just heating water to make steam would be more productive of thrust, instead of going to all the trouble to separate the elements, cool them and burn them, to create steam.

I'm hoping this puzzle will be of interest to Calliban, and perhaps to others with similar backgrounds.

Edit#1: From reading earlier posts by Calliban, I recognize that the ability of the reactor and related components to withstand the operating conditions of the inquiry may NOT be sufficient to permit the experiment, even if it were to prove cost effective.

(th)

SpaceNut · 2020-11-08 16:55:04

The heated liquid to gas phase espansion is what creates the thrust for a thermal engine which creates the greater thrust not burning it....

Design Reference Mission 5.0

also DRM 3.0 was NTR based architecture

tahanson43206 · 2020-11-08 20:47:14

For SpaceNut re #24

Thanks for the reminder of "traditional" thermal nuclear rocket designs.

I have presented an alternative to the traditional design which would (presumably) have distinct advantages.

I have a copy of "The Nuclear Rocket" by James Dewar (with Robert Bussard), in case you need a lookup for some reason.

It is possible I have an earlier book by Dewar as well, but my "library" is disorganized and I am less sure.

I'll look at the stacks to see if it's lurking in one of them.

What I have proposed a few posts back was a way of using a fission reactor that does not produce thrust directly, as a thermal rocket does, but instead produces Oxygen and Hydrogen separated from each other, and thus (potentially) available to recombine in a propulsion package at a time when it is needed.

My understanding is that something like that is planned for the ion engine propulsion system (vasimr).

Here is a snippet from Google:

Variable Specific Impulse Magnetoplasma Rocket
Engine category
Description
DescriptionThe Variable Specific Impulse Magnetoplasma Rocket is an electrothermal thruster under development for possible use in spacecraft propulsion. It uses radio waves to ionize and heat an inert propellant, forming a plasma, then a magnetic field to confine and accelerate the expanding plasma, generating thrust. Wikipedia

That system would depend upon a traditional nuclear fission reactor to produce the energy needed to drive the plasma.

In that system, a neutral gas such as argon or xenon is employed as the propellant.

The question I asked is about using plain water as the working fluid.

The application I have in mind is a massive thruster to push a fully fueled Starship toward Mars from Earth orbit, so that the vehicle can "dock" with Mars using chemical propulsion, and avoid the risks of encounter with the thin atmosphere of Mars.

(th)

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#1 2017-11-09 23:00:37

A revival of interest in Nuclear Thermal Propulsion?

#2 2017-11-10 06:00:38

Re: A revival of interest in Nuclear Thermal Propulsion?

#3 2017-11-10 06:45:00

Re: A revival of interest in Nuclear Thermal Propulsion?

#4 2017-11-10 07:25:32

Re: A revival of interest in Nuclear Thermal Propulsion?

#5 2017-11-10 11:40:50

Re: A revival of interest in Nuclear Thermal Propulsion?

#6 2017-11-10 12:27:10

Re: A revival of interest in Nuclear Thermal Propulsion?

#7 2017-11-10 13:33:28

Re: A revival of interest in Nuclear Thermal Propulsion?

#8 2017-11-10 14:51:28

Re: A revival of interest in Nuclear Thermal Propulsion?

#9 2017-11-10 15:29:34

Re: A revival of interest in Nuclear Thermal Propulsion?

#10 2017-11-10 16:47:50

Re: A revival of interest in Nuclear Thermal Propulsion?

#11 2017-11-10 18:30:12

Re: A revival of interest in Nuclear Thermal Propulsion?

#12 2017-11-10 20:03:50

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#13 2017-11-10 23:03:42

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#14 2017-11-10 23:47:27

Re: A revival of interest in Nuclear Thermal Propulsion?

#15 2017-11-11 00:25:59

Re: A revival of interest in Nuclear Thermal Propulsion?

#16 2017-11-11 12:11:27

Re: A revival of interest in Nuclear Thermal Propulsion?

#17 2017-11-11 12:49:25

Re: A revival of interest in Nuclear Thermal Propulsion?

#18 2017-11-11 12:51:54

Re: A revival of interest in Nuclear Thermal Propulsion?

#19 2017-11-11 19:53:52

Re: A revival of interest in Nuclear Thermal Propulsion?

#20 2017-12-03 15:00:44

Re: A revival of interest in Nuclear Thermal Propulsion?

#21 2020-11-08 09:30:50

Re: A revival of interest in Nuclear Thermal Propulsion?

#22 2020-11-08 10:39:50

Re: A revival of interest in Nuclear Thermal Propulsion?

#23 2020-11-08 12:14:47

Re: A revival of interest in Nuclear Thermal Propulsion?

#24 2020-11-08 16:55:04

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#25 2020-11-08 20:47:14

Re: A revival of interest in Nuclear Thermal Propulsion?

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