Nuclear Thermal Propulsion

Winston

Lorenzo von Matterhorn
Joined
Jan 31, 2009
Messages
9,542
Reaction score
1,694
Clever EXTERNAL control rods which moderate via rotation, necessary to shorten reactor length and mass.

NUCLEAR PROPULSION IN SPACE (1968)

Produced by the Atomic Energy Agency and NASA, this film details Project NERVA -- the Nuclear Engine for Rocket Vehicle Application. This was a joint program of the U.S. Atomic Energy Commission and NASA managed by the Space Nuclear Propulsion Office (SNPO) at the Nuclear Rocket Development Station in Jackass Flats, Nevada U.S.A. Between 1959 and 1972, the Space Nuclear Propulsion Office oversaw 23 reactor tests,

As the narrator states, "The proposed mission to explore the moon, in addition to further missions, will require the acceleration and deceleration of very heavy loads." This documentary explores the use of nuclear propulsion to complement the chemical fuels used in today's rockets. The film shows a Saturn 5 rocket on its launchpad, launch and flight [including stage separation and air-ground shots]; the concept of substituting a nuclear 3rd stage to increase payload velocity; 1950s research in New Mexico to determine the feasibility of nuclear energy in rocket propulsion; development of engine technology via the NERVA project, engine testing; a description of how this technology may be used for a theoretical mission to Mars.

By the end of the program, NERVA had demonstrated that nuclear thermal rocket engines were a feasible and reliable tool for space exploration, and at the end of 1968 SNPO certified that the latest NERVA engine, the NRX/XE, met the requirements for a manned Mars mission. Although NERVA engines were built and tested as much as possible with flight-certified components and the engine was deemed ready for integration into a spacecraft, much of the U.S. space program was cancelled by Congress before a manned visit to Mars could take place.

NERVA was considered by the AEC, SNPO and NASA to be a highly successful program; it met or exceeded its program goals. Its principal objective was to "establish a technology base for nuclear rocket engine systems to be utilized in the design and development of propulsion systems for space mission application" Virtually all space mission plans that use nuclear thermal rockets use derivative designs from the NERVA NRX or Pewee.

The Rover/NERVA program accumulated 17 hours of operating time with 6 hours above 2000 K. Although the engine, turbine and liquid hydrogen tank were never physically assembled together, the NERVA was deemed ready to design into a working vehicle by NASA, creating a small political crisis in Congress because of the danger a Mars exploration program presented to the national budget. Clinton P. Anderson, the New Mexico senator who had protected the program, had become severely ill. Lyndon B. Johnson, another powerful advocate of human space exploration, had decided not to run for a second term and was considerably weakened. NASA program funding was somewhat reduced by Congress for the 1969 budget, and the incoming Nixon administration reduced it still further for 1970, shutting down the Saturn rocket production line and cancelling Apollo missions after Apollo 17. Without the Saturn S-N rocket to carry the NERVA to orbit, Los Alamos continued the Rover Program for a few more years with Pewee and the Nuclear Furnace, but it was disbanded by 1972.

The most serious injury during testing was a hydrogen explosion in which two employees sustained foot and ear drum injuries. At one point in 1965, during a test at Los Alamos Scientific Laboratory, the liquid hydrogen storage at Test Cell #2 was accidentally allowed to run dry ; the core overheated and ejected on to the floor of the Nevada desert. Test Site personnel waited 3 weeks and then walked out and collected the pieces without mishap. The nuclear waste from the damaged core was spread across the desert and was collected by an Army group as a decontamination exercise.

An engine of this type is on outdoor display on the grounds of the NASA Marshall Space Flight Center in Huntsville Alabama.




Geoffrey Landis - The Nuclear Rocket Workhorse of the Solar System



The Nuclear Option



NASA's New Space Reactor Is Powered by Nuclear Fission



Nuclear Engine for Rocket Vehicle Application (NERVA)


NERVAenginemockup.jpg


NERVA-II_Envelope.gif


Kiwi B4-A reactor

8YNR0IFQpGODwKFClwWRYIAXoRwR_vJMbna33h2MejE.jpg


NUCLEAR ROCKETS: To Mars and Beyond


NASA's plans for NERVA included a visit to Mars in 1979 and a permanent lunar base by 1981. NERVA rockets would be used for nuclear "tugs" designed to take payloads from low-Earth orbit to higher, larger orbits as a component of the later-named Space Transportation System. The NERVA rocket would also be used as a nuclear-powered upper-stage component for the Saturn rocket (a chemical-based rocket), which would enable the upgraded Saturn engine to launch much larger payloads (up to 340,000 pounds) to low-Earth orbit.

In 1973, Project Rover/NERVA was cancelled. Although the projects proved very successful, the space mission itself never took place. No nuclear-thermal rockets were ever used to send explorers on long-range space missions.

It was the Mars mission that led to NERVA's termination. Members of Congress judged the manned mission to Mars was too expensive and that funding the project would continue to foster a costly "space race" between the United States and the Soviet Union.

By the time NERVA was cancelled, the NERVA-2 would have met all the mission's objectives. Two of these engines would have been fitted to a NERVA stage capable of powering a manned interplanetary spacecraft.

During its lifetime, Project Rover/NERVA achieved the following records:

4,500 megawatts of thermal power
3,311 K (5,500.4°F) exhaust temperature
250,000 pounds of thrust
850 seconds of specific impulse
90 minutes of burn time
thrust-to-weight ratios of 3 to 4
Beyond proving the feasibility of nuclear space propulsion, Project Rover/NERVA enabled scientists to produce approximately 100 technical papers that covered the properties of graphite, graphite flour, and other forms of carbon. The program also produced several important spin-offs, including Sheinberg's room-temperature graphite-fabrication process and methods for coating graphite with thin films of metal carbides.

Moreover, the technology for coating UC2 particles with pyrolytic graphite eventually led to the TRISO fuel beads now used in commercial high-temperature, gas-cooled reactors to generate electricity. However, the program's most important spin-off—by any measure—was the heat pipe (see the " Inspired Heat-Pipe Technology" article).

The heat pipe is currently the centerpiece of the Los Alamos research program known as Heatpipe Power System (HPS) reactors. As envisioned by heat pipe inventor Los Alamos physicist George Grover, HPS reactors use heat pipes to transfer heat from a reactor core to thermoelectric elements or heat engines.

In 2000, NASA created Project Prometheus to develop nuclear-powered systems for long-duration space missions. This project was NASA's most serious consideration of nuclear power for space missions since the cancellation of Project Rover/NERVA in 1972. For the Jupiter Icy Moons Orbiter (JIMO), a spacecraft designed to explore Europa, Ganymede, and Callisto, NASA intended to use an HPS reactor. The JIMO (Fig. 10) design used a fission reactor to power a Brayton-cycle heat engine that ran an electrical generator. The electricity would then power scientific instruments and an ion-propulsion unit. In 2005, NASA canceled the Prometheus Project as a result of budget constraints.


Nuclear Thermal Propulsion (NTP) [extensive resource! - W]


Nuclear Rocket Images
NERVA, Phoebus, Kiwi


 

prfesser

Well-Known Member
TRF Supporter
Joined
May 7, 2017
Messages
2,767
Reaction score
3,585
Location
Murray, KY
"The Throne of Saturn" by Allen Drury is a pretty decent (though very political) novel about the development of fictional Project Argosy, a mission to Mars. It's set in the late 1970s. Three Saturn V launch vehicles, each with a NERVA vehicle in place of the regular third stage. The NERVA stage would be almost the same diameter as the 1st and 2nd stages, and I think it was to be longer than either of the other stages. Need a lot of room to hold enough LH2 for a trip to Mars. A gallon of LH2 weighs about half a pound, compared to about eight pounds for a gallon of milk.
 

aerostadt

Well-Known Member
TRF Supporter
Joined
Oct 26, 2009
Messages
3,924
Reaction score
652
Location
Brigham City, UT
Yes, a lot of good basic nuclear thermal rocket research was done in the 60's. The hazards of launching radioactive material by rocket was and still is a public concern and puts a large damper on this concept. Roughly, an nuclear thermal (liquid H2) rocket Isp is about 800 sec. versus a chemical H2 rocket of about 400 sec. , a respectable gain. Conceivably, a nuclear rocket could be refueled. One of the biggest drawbacks of a nuclear thermal rocket is the same problem as land-based commercial reactors. When the reactor is shut down, decay heat from isotope radioactive decay must be removed. This is no problem if a fluid can be re-circulated through the nuclear core to remove the decay heat. At Three-Mile Island the operators thought water was being re-circulated, but it was not due to a stuck open safety relief valve. For the Japanese reactor failure the diesel generators to power the electric re-circulation pumps were wiped out by the tsunami and the core became uncovered. In space there is no way to dump decay heat by convection, there is only thermal radiation, which is not as good. Some of the alternatives at the end of the article might be helpful, i.e., use nuclear energy for ion propulsion or use thermal heat in a Brayton cycle to make electricity.
 

UhClem

Well-Known Member
Joined
Feb 6, 2009
Messages
2,010
Reaction score
399
For the Japanese reactor failure the diesel generators to power the electric re-circulation pumps were wiped out by the tsunami and the core became uncovered.

This has always mystified me. The reactor was generating more than enough heat to generate steam to spin a turbine.

As for nuclear thermal propulsion, DUMBO was a better design than NERVA in a lot of ways.
 

aerostadt

Well-Known Member
TRF Supporter
Joined
Oct 26, 2009
Messages
3,924
Reaction score
652
Location
Brigham City, UT
This has always mystified me. The reactor was generating more than enough heat to generate steam to spin a turbine.
Usually, when the control rods drop and the core shuts down such as an earthquake or tsunami, there is a severe mismatch in the steam supply to the turbines and what the reactor is producing and so the whole plant goes off-line. The idea is that the emergency diesel generators will supply the residual coolant flow to the reactor to remove the isotope decay heat. There is now of using natural convection in commercial designs to remove residual decay heat after shut-down.

As for nuclear thermal propulsion, DUMBO was a better design than NERVA in a lot of ways.
What was the DUMBO design?
 

UhClem

Well-Known Member
Joined
Feb 6, 2009
Messages
2,010
Reaction score
399
When I first read about that project this report was still classified so I had to make do with an article in the popular press. That article (Analog magazine, December 1975) showed a design for a F1 class nuclear rocket motor.
 

aerostadt

Well-Known Member
TRF Supporter
Joined
Oct 26, 2009
Messages
3,924
Reaction score
652
Location
Brigham City, UT
When I first read about that project this report was still classified so I had to make do with an article in the popular press. That article (Analog magazine, December 1975) showed a design for a F1 class nuclear rocket motor.
UhClem,
Can you boil this Dumbo concept down for me? The report is 378 pages of equations for fluid flow, neutron diffusion, and heat transfer. I do not see the advantages and conclusions clearly laid out. Are you implying that the nuclear core is self-regulating with fluid flow? If so, how come such a device was not tried out in practice?
 

aerostadt

Well-Known Member
TRF Supporter
Joined
Oct 26, 2009
Messages
3,924
Reaction score
652
Location
Brigham City, UT
I went through the Analog article pretty quick, but I think I caught the gist of it. It looks like Dumbo had a way of reducing thermal gradients in the fuel elements, which is an important problem. I don't see any mention of control rods, but perhaps I missed it. As far as I know all present large-scale commercial reactors start criticality by removing control rods and shut down by putting rods back in. There are tricks for controlling criticality by modifying the density of the moderator or reaction poisons. It sounds like Dumbo can be throttled better, but I am thinking that it still has the decay heat problem. The author says that there are thrust-to-weight improvements, so lift-off from the earth's surface is practical. There are still radioactive problems. I don't think the public is ready for nuclear rockets taking off from the surface of the earth. I still like idea of putting land-based nuclear rockets on the moon or Mars and producing hydrogen and oxygen for space exploration.
 

Rocks&Rockets

Re-tired Inspector
Joined
May 27, 2020
Messages
51
Reaction score
37
Location
Grand Junction, CO
HTRE INEL.JPG

HTREs.JPG
It's not a rocket, but would you fly on this?
Nuclear powered aircraft engine devleoped in the 1950s. One verticle core, one with a horizontal core. It actually flew HOT on a modified Consolidated B-36 test-bed though not powering the aircraft.
 

Rocks&Rockets

Re-tired Inspector
Joined
May 27, 2020
Messages
51
Reaction score
37
Location
Grand Junction, CO
Your are correct.. INEEL now.
Been a while since I worked up there,
Those two engins are displayed at EBR-1 Experimental Breeder Reactor- atomic museum west of Idaho Falls.
Gotta go again!
 

OverTheTop

Well-Known Member
TRF Supporter
Joined
Jul 9, 2007
Messages
7,305
Reaction score
5,326
Location
Melbourne Australia
The AIAA has a magazine called Aerospace America which is published monthly. The December issue is a synopsis of the various fields over the past year. Here is the text from the relevant page of the magazine, relating to Nuclear and Future Flight Propulsion:
Since 2016, NASA has been exploring lowenriched uranium, LEU, reactors for nuclear thermal propulsion or NTP. The LEU NTP project, led by NASA, is aimed at developing a demonstrator to fl y before 2030 as a test for crewed missions to Mars. Significant conceptional design evaluations and work were completed toward LEU NTP in 2019.

In February, the LEU NTP project received additional funding and initiated several studies with
industry and U.S. Energy Department labs. In May, Aerojet Rocketdyne refined its predicted performance modeling of an LEU NTP engine.

In July, researchers at NASA’s Marshall Space Flight Center in Alabama revisited demonstrator vehicle concepts through various design cycles.

In August, retired nuclear engineer David Black published a study concluding that low-enriched uranium reactors, though higher in mass than a highly enriched uranium reactor, can be designed to meet the mission, lifetime and operability requirements of NTP missions while simultaneously offering less stringent safety, security and proliferation concerns.

Also in August, the Energy Department’s Sandia National Laboratories, Oak Ridge National Laboratory and Idaho National Laboratory worked with Marshall and BWX Technologies of Virginia to develop a path forward for LEU NTP fuel selection and reactor design.
In other advanced propulsion areas, NASA’s Innovative Advanced Concepts office in April conducted a Phase II midterm review for a proposal awarded in 2018 to California State University-Fullerton to continue its experimental efforts examining the Mach effect, a theoretical form of gravitational propulsion that does not expel mass and only uses electrical power. CSU-Fullerton has been developing and testing Mach effect devices for 25 years as well as refining the theory of operation. Experiments in Germany, Canada and Italy and by multiple independent researchers in the U.S. are heavily focused on thrust balance calibration, experimental procedure, signal amplifi cation and corrections to the theory. The forces generated from these devices are generally less than 10 micronewtons, but the true nature and source of the signals remains inconclusive. If the theory is found to be legitimate, Mach effect research could pave the way for new propulsion physics and have applications well beyond space systems.

Researchers from Quantum Fields LLC in Illinois; the Institute for Advanced Studies in Texas; and the Center for Astrophysics, Space Physics and Engineering Research at Baylor University in Texas published new results in August on producing and accessing the negative quantum vacuum energy densities theoretically required by general relativity to produce novel propulsion schemes such as warp drives and worm holes. This work noted the startling fact that the theoretical quantum inequality restrictions needed to generate such energies have not been experimentally tested. The researchers analyzed the various technical schemes known to produce “squeezed vacuum states” with the technique called a “squeezed light” and discovered that the restrictions were violated in the evaluated published quantum optics squeezed light experiments (represented by 25 years of published data). The Casimir effect (with negative vacuum energy density in the space between the two Casimir cavity walls) is also expected to demonstrate experimental violation of quantum inequality, but this experiment has yet to be demonstrated in the lab because of numerous technical challenges. The consequence of the experimental violations of quantum inequality was that nature does not impose any truly significant constraint on technologically producing and accessing negative vacuum energy density; this result implied that there should be no roadblock to artificially producing a warp drive or a traversable wormhole to achieve faster-than-light propulsion for interstellar flight.

In August, Stan Borowski presented a summary of recent design studies in both nuclear thermal propulsion and in-situ resource utilization that could lead to viable experiments blending the two technologies. This work will be critical for planning and modeling missions using NTP. Borowski retired in December 2018 from NASA’s Glenn Research Center after a 30-year career.



Here is another interesting article on NASA and NTP:
 

aerostadt

Well-Known Member
TRF Supporter
Joined
Oct 26, 2009
Messages
3,924
Reaction score
652
Location
Brigham City, UT
The year-end AIAA Aerospace America gives a wide report on dozens of different subjects. Summaries are submitted by invited experts/authorities nationwide. Across the country there are always many research avenues that are being explored.
 

OverTheTop

Well-Known Member
TRF Supporter
Joined
Jul 9, 2007
Messages
7,305
Reaction score
5,326
Location
Melbourne Australia
Yes. Each page has a one-page synopsis of each area of endeavour. It is a really good read. I would post a link to the mag here but they have it locked only for members. They used to release the older mags for general access, but no more.
 

aerostadt

Well-Known Member
TRF Supporter
Joined
Oct 26, 2009
Messages
3,924
Reaction score
652
Location
Brigham City, UT
I quickly skimmed through the Wikipedia entry for the NERVA rocket, which gives information similar to Winston's first post. It seems that the NERVA program was doing well, but was cancelled by congressional budget considerations and the end of the infatuation of the Saturn V program. In a way, so near, but yet so far.

 

BBowmaster

Well-Known Member
Joined
May 29, 2017
Messages
346
Reaction score
229
I read about NERVA in school in the early 70s. If it weren’t for politics, we’d be on the moon complaining about politics by now. 😀
 

Winston

Lorenzo von Matterhorn
Joined
Jan 31, 2009
Messages
9,542
Reaction score
1,694
The US military is getting serious about nuclear thermal propulsion
“Activity in cislunar space is expected to increase considerably in the coming years.”
6/15/2020


...now, the US Department of Defense is getting interested in space-based propulsion. Last month, through a presolicitation, the US Defense Advanced Research Projects Agency announced its intent to have a flyable nuclear thermal propulsion system ready for a demonstration in 2025.

Through this Demonstration Rocket for Agile Cislunar Operations, or DRACO program, the defense agency seeks technology that will allow for more responsive control of spacecraft in Earth orbit, lunar orbit, and everywhere in between, giving the military greater operational freedom in these domains.

"Activity in cislunar space is expected to increase considerably in the coming years," Maj Nathan Greiner, manager of the DRACO Program, told Ars. "An agile nuclear thermal propulsion vehicle enables the DOD to maintain Space Domain Awareness of the burgeoning activity within this vast volume."

In "Phase 1" of its solicitation, DARPA has asked industry for the designs of both a nuclear thermal reactor and an operational spacecraft upon which to demonstrate it. This initial phase of the program will last 18 months. Subsequent phases will lead to detailed design, fabrication, ground tests, and an in-space demonstration. No contracts have yet been awarded, and award values will be determined by industry submissions.

With the DRACO program, the US Defense Department could potentially move large satellites quickly around cislunar space. For example, moving a 4-ton satellite from point A to point B might take about six months with solar electric propulsion, whereas it could be done in a few hours with nuclear thermal propulsion.

DARPA's decision to push forward with development of nuclear thermal propulsion comes as critical enabling technologies are maturing...

One advancement has come in the ability to manufacture refractory metals, which are extraordinarily resistant to heating. To operate efficiently, Cirtain said, an engine must be able to withstand huge temperature and pressure changes across just two meters in length. Hydrogen fuel is stored at just 19 Kelvin and heated to 2,500 Kelvin or higher.

At the same time, engineers designing nuclear reactor cores have access to computational power that allows them to iterate new designs—calculating such variables as neutron flux and fluid dynamics—quickly. "Now, with supercomputers on your desk, you can go from years' worth of calculation time to days, and iterate to a design solution much faster than you could previously," he said.
 
Top