Nuclear Rocket Power in Space: Generational Legacy

A fifty-four hour workweek is not my idea of fun, even for a dreamy eyed procrastinator like me. Sometimes you have to acknowledge the savvy, curious and inventiveness of people who dedicate their life to develop tangible means of propulsion for in-space transportation, especially when it involves the peaceful noble pursuit of guaranteeing continued survival of our species in the solar system.

In the mid 60's Government and Industry looked to a cheaper reliable alternative to chemical rocket engines. The era of President Kennedy, Cold War and the race to the Moon was in full bloom. Project Rover was an effort to build a nuclear reactor to power a rocket in space. Los Alamos National Laboratory was assigned this task. Project Rover developed a series of reactor designs that took advantage of fissionable materials to heat high temperature fuels.

The basic concept was simple; take a solid-core Hydrogen-cooled reactor in which the exiting gas expanded through a rocket nozzle to discharge in space producing thrust. The motivation for development was that it could produce about twice the specific impulse Isp (thrust per unit flow rate of propellant) of the best chemical rockets (even today) thus a reduction by a factor of 5 in the ratio of take-off mass to final mass at earth-escape velocity.

Project Rover attracted the famous including President Kennedy and Wernher Von Braun considered the, "Father of space travel' who came to visit the facilities. Westinghouse Electrical Corp. and Aerojet General Corp. prime contractors helped test the NERVA program NRX series prototype reactors based on the Los Alamos designs. Serious research began in 1964 with advanced designed engines: KIWI, PHOEBUS, PEEWEE, which culminated with the NF-1 (nuclear furnace). After $1.5 billion dollars spent on the project it terminated January of 1973. At the point of flight engine development the project was appraised as a technical success.

Rover was terminated from government accounts due to "Shifting national priorities", nuclear rockets were considered a potential back-up for intercontinental ballistic missile (ICBM) propulsion, later cited as a use in a second stage for Lunar flight and lastly as a more durable possibility in propulsion efforts for manned mars missions. But, no one I have spoken to fails to leave out the obvious political pressure amid the growing environmental chorus of dissent to the project at the time.

Other than Russian nuclear achievements in space no other entity had won at demonstrating the raw power of crafted nuclear rocket propulsion except Project Rover. Code-named "Phoebus" after the Greek Sun Chariot God; this engine tested at an Isp of 825 seconds producing peak power of 4080 MegaWatts (measure of power) for 12 minutes duration. Project Rover was tested at the Department of Energy DOE facilities in Jackass Flats, Nevada. "Pewee reactor tested in 1968 ran for a total of 192 minutes at power levels above 1MW on two separate days. The full-power test consisted of two 20-minute holds at design power (503MW) and an average fuel-element exit-gas temperature of 2550 Kelvin. This temperature was the highest achieved in the Rover program. It corresponds to a vacuum specific impulse of 845 seconds at a level in excess of design goals set for NERVA." (Experience gained from ROVER, 1986, Daniel R. Koenig)

The last reactor test of Rover was Nuclear Furnace NF-1. A reactor ten times less in design power than Pewee, NF-1 was a low priced means to test full-sized rocket reactor fuel elements and other core components in a reactor having low fuel inventory. A major objective of this design was to have a reusable test device. The core assembly would be removed and disassembled for examination, whereas a permanent structure would be retained for use with a new core. Removable and portability features were demonstrated on NF-1. Hydrogen exhaust gas was also treated. Instead of exhaust convergent-divergent nozzle directed into atmosphere hot hydrogen was cooled by injection of water, exhaust resultant steam was ducted off to an effluent clean up system for fission by-product scrubbing before gas release to atmosphere.

Toward the end of the NERVA/ROVER project other comprehensive design studies were placed on smaller engines for orbital transfer missions. Example: Miniature Nuclear Propulsion Engine. Also, closed-loop and open-loop electrical power systems NEP (nuclear electric propulsion) were incorporated. The "Gas core" concept was also investigated (Weinstein 1960 & Kerrebrock 1961)

"Rover Program terminated before showing that an engine could be operated for 10 hours with up to 60 starting cycles with a reliability of 0.995." (Experience gained from Rover, 1986, Daniel R. Koenig)

Again, without blowing the, benefits of "Nuclear rocket power science" horn too hard, I have never heard of main engine high thrust chemical propulsion system capable of sustained high Isp 845 seconds thrust, at a temperature average of 2450 K, for continuous 10 hour running with average 20-40 on/off cycles on different days, at almost solid reliability of operation, that's better performance reliability than most cars on the road today.

NASA Announced its Intentions to Revisit the Issue of Nuclear Power in Space Early in 2002.

It has been nearly fifty years since the U.S. government began experimenting with nuclear power for space applications. Other than the latest much publicized Cassini Mission to Saturn launched 1997 in which a Radioisotope Thermoelectric Generator RTG using the radioactive fuel Plutonium 238 flown to Saturn; not much has happened since. Although NASA had known for years about advanced space transportation technology such as fission it has always maintained an estrangement toward other in-space propulsion modes claiming; conventional chemical rockets in every instance provide adequate propulsion. In the mid 90's concern of NASA's reluctance of things new in the field of propulsion led to workshops in "Propulsion breakthroughs" in order to quell the space culture's desire to see some real advancement in the field.

In an effort to rekindle the public's romance with space some changes by the Bush administration's anointed NASA chief, Sean O'Keefe made it clear that in fact things would change at NASA and it drew up the, Space Launch Initiative (SLI). How the Bush Blueprint on budget deficits and the war on terrorism will effect NASA is still under stressful reorganization. What is known is significant out sourcing of personnel, equipment and operations including ownership of most of the refitted RS-83 engine space shuttle fleet of vehicles to a new private company. There will be fewer space shuttle missions for the near future.

Old Cold War to Cold New Terrorists States Could Put Nuclear Technology in Space.

Similar situation different circumstances may help to put nuclear technology in space. Human nature by nature is competitive and lethal at times, views proselytizing permanent eternal tranquility, though noble in pursuit can be fatal. Ignoring defensive capability breeds' denial to catastrophic eventuality as witnessed on the World Trade Center in New York City on September the 11th.

Our military's future testing and deployment of nuclear rocketry is necessary; security only works when people responsible for defense have access to advanced nuclear propulsion in space to perform the many tasks in space of defending our country and allies on the ground. The Bush revamp of NASA could qualify as a leader doing what is necessary in space in the face of adversity and criticism. Such as the politically heavy weighted issue of the DOE's Nevada Yucca Mountain Nuclear Waste Facility. Energy Secretary Spencer Abraham's correct conclusion, that the remote desert facility is scientifically sound and important to national security in testing and proper storage of nuclear material; creating permanent well paying technical jobs for Nevada rather than low wage temporary work at Las Vegas hotels cleaning toilets.

Nuclear Propulsion Dependant on Which Gear a Mission Planner Wants to Shift Into.

It runs the gamut from the natural gravitational and solar assists or the tiniest amount of thrust production the equivalent to a sheet of paper held against your finger; to the charge of an ORION style pulsed nuclear concept at Isp in excess of 10,000 sec. with great velocity change (delta V) requirements. How would you like a spacecraft to steer in space? Would you like standard slow steering or faster power steering or both? These are examples of what space scientist and engineers wrestle with against a backdrop of issues involving cost, safety, desired performance levels and politics.

To sense how the scientist in the field sees I asked Herb Funsten: Center for Space Science and Exploration, Los Alamos Laboratory. "What is the future in Nuclear power in space, now that the NASA has decided to rethink the issue of nukes in space for thrust production? He said, "The future on nuclear activities in space will revolve around (NEP) Nuclear electrical Propulsion at least in the immediate future involving light payload long duration missions."

I asked, " Would this be similar to 'Deep Space 1' the 1998 launched robotic spacecraft powered by the heavy molecular weight gas fuel Xenon blown through a charged grid to produce ionized plasma that is electrically accelerated to a speed of 30km/sec in rocket exhaust that produced the tiniest thrust that ended in 2001?"

He said, "Similar - the change from that system would be a small nuclear reactor core essentially providing the charge of electrical power to produce the ionized plasma rather than the use of extensive solar array structures used to provide electrical power."

Since our phone conversation drifted toward safety issues I asked him, about specific in-space nuclear core safety issues and mechanisms such as reactor components launched separately and assembled when desired orbit is achieved, based on SAFE-100 proposals for both credible and non-credible accidents. He said, "Safety in developmental testing capabilities are of high importance at Los Alamos Labs for both terrestrial and in space activities when employing nuclear reactor cores."

My last safety concern was random meteoric impact. Meteors that can range from the size of a grain of sand generally weighing 1-2 grams to a small pebble composed of low-density stony fluffy material depending on either cometary (majority) or metallic asteroid origins. With the Earth revolving around the Sun at a speed of 30 km/sec. they strike the Earth at an average speed of 20 km/sec.

Crew (25cm of water habitat shielding) and reactor core shielding technology has been addressed for this eventuality with lightweight composite laminate cloths. But I also wondered if there wasn't an added component to protection, a spinning shield capable of successfully deflecting a violent impact. Call it, "Spin police shield" for space debris and meteor protection. Sometimes law enforcement officials are involved in thwarting high speed out of control vehicles by using familiar methods to stop a perpetrator. On one occasion I was told a high speeding semi truck had evaded roadblocks at one point a police officer decided he had had enough and was determined to stop the culprit by drawing his .38 caliber service revolver. He leveled his weapon standing 10 feet from the right front tire traveling at approx. 80 mph. To his surprise every round fired point blank at the spinning tire bounced off harmlessly. Fortunately the officer was not harmed and the perpetrator's truck ran over a 'nail ribbon' placed further up the road and was apprehended. About the potential encounter with a meteoric storm which is predictable and navigable affording early warning Mr. Funsten said, "These nuclear systems would not be operational till the desired need to have them work and the distances involved would be far from any Earthly influence in any event."

An X Prize in Store for Those Who Can Build a Powerful, Safe, Reliable, Main Engine In-Space Nuclear Propulsion System.

President Bush senior announced a Space exploration initiative in 1989. The goal then was to send a manned mission to Mars by 2018. The Nuclear rocket was again considered as the main engine for Mars missions. In the end nuclear propulsion can take many forms ranging from low thrust nuclear electric propulsion, higher thrust nuclear thermal propulsion and electrical or thermal "Pulsed nuclear" propulsion. Essentially the old axiom, "Build it and they shall come" holds. A nuclear main engine that demonstrates all the right qualities will be used. Personally, Nuclear Fusion and Antimatter propulsion though promising is far into the future in development. Open nuclear thermal pulse technology is again intensively banked into the future in design. Could be useful for evasive and emergency maneuvering in space.

Uncomplicated Solid and Gas core nuclear thermal rockets show the most immediate promise.

Gas core nuclear fission rocket engine (GCNR) is cold hydrogen pumped into the main axis of a rocket's engine. Hydrogen circulates creating a "Re-circulation Vortex" in a chamber. Uranium particulate is injected into the center of the vortex until the Uranium accumulates to near-critical mass. After the chamber is stabilized, control drums in reflector walls rotate causing Uranium to go critical. The hot Uranium gas approaching 55,536 degrees C radiate energy to surrounding Hydrogen which exits through a nozzle to provide thrust at an Isp of >2000 seconds.

A claim has been made that GCNR can "Point-and-shoot" an "Opposition class" Mars mission trip time of 9 months. A few months arrival, 30-60 day stay on Mars with a few months return trip. "The delta V's for a fast transit mission occurring in the year 2011 are (courtesy of Michelle Monk at NASA/JSC) 6.4,12.3,15.3 and 14.7 km/sec. for four burns at Trans-Mars Injection (TMI), Mars Orbital Insertion (MOI), Trans-Earth Injection (TEI), Earth Orbital Insertion (EOI) respectively. Thus the total delta V for all four burns are near 50 km/second. If the GCNR has an ISP of 3000 seconds then just under 20% of the total ship mass in LEO (Low Earth Orbit) will be payload and structure-the rest will be fuel. That is to say, it will require 4 kilograms of fuel for every kilogram of payload to perform the entire mission" (Reducing the risk to Mars: The Gas Core Nuclear Rocket, S.D Howe, B. DeVolder, L. Thode and D. Zerkle, Los Alamos National Laboratory).

This claim of trip times to Mars is short indeed compared to NASA's Design Reference Mission (DRM) for Mars. Designed for a Solid Core Nuclear Rocket requiring TMI, aerobrake capture at Mars, a previously positioned cargo mission return ship which uses chemical propulsion into Mars orbit, aero capture at Earth. Total mission: 900 days from Earth - about two and one-half years.

The problem with the proper effectiveness of hot plasma (fourth state of matter) enclosed in a chamber causing hot hydrogen to escape producing thrust, though simpler to achieve than complete closure without confronting issues of, inertial or magnetic plasma stability was told, is at least 20 years away. Due in part to a lack of funding in construction, with extensive computer modeling and use of high end plasma study facilities, such as use of the National ignition Facilities (Hot Point).

All the Nuclear systems mentioned are adequate for use in space; some are more advanced in development, testing and actual in-space operations than others. To date no serious attempt using this tool to its full potential in space, as a main engine high (Isp), high mass thrust producer.

Technologies for this important tool exist today. As Mme. Curie so apply stated, "everyone is gifted." Excessive procrastination on its full use is not using the gift.

I could still see the enviro-weenies demagoging the issue. I could hear their shrill voices right now "If one of those cannons mis-fires it will spew radiation across the entire west (or east) coast!"
We just need leadership that has the cajones to tell them to get stuffed. Of course this administration just might do it. :)

"I'll let the engineers and scientists belly up to the bar on the technical problems but the main impediment will be the earth launch of large amounts of fissionable material. That is political in the US though other space faring states might not have that problem."

This is absolutely not a problem (except in the minds of anti-nuke "green weenies"). Send the fissionables up as "less than critical mass" segments---one per shuttle flight--during the normal re-supplying of the now-under-construction space station. Assemble the reactor and the rest of the vehicle at the space station, tank it up, and "awaaaaay we go"---on to Mars and the rest of the planets.

FWIW--back in the "dark ages" of the early 70's, one my profs in my Nuclear Science classes (radiation shielding) was a nuclear engineer who had actually worked on NERVA. He REALLY knew his stuff!

You obviously are knowledgable about space travel. Let me ask you a question I have often wondered about. The physicist, Freeman Dyson, wrote an article for Time a couple of years ago in which he said that to get to Pluto in 16 months one would need a spacecraft capable of traveling 100 miles per second. This is many times faster than some of the meteors/comets/asteroids that have caused so much destruction on earth in eons past. What happens when a spacecraft traveling at 100 miles per second hits some space dust, space sand or even space gravel? Won't these have the power of little nuclear explosions? What will that do to the spacecraft itself? Will there be anything left by the time it reaches Pluto?

What happens when a spacecraft traveling at 100 miles per second hits some space dust, space sand or even space gravel?

The energy of kinetic motion is not nuclear, but it is enough to not only vaporize some material, but ionize it to a plasma. It is an awesome energy. For spaceship design, one needs to consider the probability of encountering something large enough to be a problem and to have some kind of shield in the design.

Along with a kinetic shield, another kind of shield should also be part of the design, which would be shielding against dangerous radiation.

"You may well be right but that is my point. STS has failed. Spectacularly. It does not good to say that it is unlikely or that the 'fissionables' cannot explode. This is a perception problem."

The fact that the Cassini probe got launched despite exactly that same "perception problem" proves that to be a non-problem. As long as the total amount of fissionable material is less than one "critical mass" per shuttle load, you cannot have a nuclear reaction at all--the assemblies are so much metal bars, and in fact are more innocuous than the Cassini plutonium. The shuttle has to make the flights anyway to haul up the rest of the mission supplies, so adding a single reactor assembly (or two, or three as long as the total mass of fissionable is less than critical) per trip to the overall supply load is no problem Your "cannon" idea is simply an un-necessary additional complication.

Bump!

NASA'S MIDLIFE CRISIS -Poll: Space program generates low enthusiasm in public--- John Pike, space-policy expert and director of the defense think tank Globalsecurity.org, was more blunt. "Rich white men like the space program; other people don't," he said. "Rich people are prepared to spend money on luxuries that poorer people aren't."

I'm still waiting for ORION.

Inverted saucer of battleship steel (THICK, mind you). Stick a payload the size of the USS Missouri on top, and light off a series of nukes underneath.

Nuclear propulsion, big time.

Wouldn't mind being pinged on this subject . Bump for later. I'll refrain from mentioning the most powerful nuclear fuel but I definitely believe nuclear power is the only way to go for space so thanks for the link. The future really should be like a Heinlein novel.

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