It’s Thursday, meaning it’s time to dig through the Nuclear News archives for another #ThrowbackThursday post. Today’s story goes back 60 years to the January 1963 issue of NN and the cover story “Review of Rover: A nuclear rocket” (p. 9), which reviews the first phase of the nuclear rocket program from Los Alamos National Laboratory.
Some quick digging online uncovers a lot of information about Project Rover, most notably, a short 20-minute film on the LANL YouTube page that reviews the project (Historic 1960s Film Describes Project Rover). The description of the video notes that the project was active from 1955 to 1973 and led to the design of multiple reactors suitable for testing, including Pewee 1, and that NASA has a modern nuclear thermal propulsion project based on the Pewee design. So it seems fitting to revisit Project Rover, given that there is today a lot of renewed interest in nuclear propulsion for space exploration.
The opening line from the January 1963 article seems to ring true today— “Provided the U. S. continues her space efforts, nuclear-powered rockets are inevitable”—although that probably didn’t seem likely to the nuclear community after the country’s attention shifted from the Space Race to the Vietnam War in the early 1970s when Project Rover was canceled. The introduction to the article lays out the argument for a nuclear-powered rocket and provides a review of the program since its launch in 1955.
The full article as it appeared in 1963 is reprinted below, but don’t forget, all ANS members have full access to the Nuclear News archives that has decades of great content about all topics on nuclear science and technology. Happy reading!
REVIEW OF ROVER - nuclear rocket
The first phase of the nuclear-rocket program (the KIWI stage - developing the reactor and its operating principles) is coming to an end, with the full engine development (the NERVA stage) now getting thoroughly started. This transition, together with President Kennedy's recent visit and his December 12 press-conference comments on the program, prompts the review of Project Rover.
Provided the U. S. continues her space efforts, nuclear-powered rockets are inevitable. The reason is basic thermodynamics: a nuclear-heated system has a theoretical advantage of between two and three over a chemical system. The unit in discussing the relative potential is specific impulse, the pounds of thrust delivered per pound of propellant used per second. It depends inpart on the square root of the molecular weight of the propellant used, the lighter the propellant (and therefore the faster the exhaust velocity) the better. Nuclear rockets, which heat hydrogen, have a clear impulse advantage over chemical fuels with their propellant of molecularweight of about 18. In actual numbers, the NERVA engine will develop a specific impulse of fully 800 seconds (about 50 Ib of thrust per megawatt of power); the best for chemical rockets is about 400 seconds.
The longer the space mission, the greater the advantage. For instance, on a manned landing on Mars, the weight of material to be put in an earth orbit is about 12x106 lb with a chemical system, about one tenth of this with nuclear. The saving in money thus effected in one mission is reckoned to pay for the entire nuclear-rocket program. (The weight advantage on a lunar trip, which offers less chance for the best utilization of fuel, is about two).
It should be noted, however, that chemical rockets are much more suitable for the first stage - a launching from the earth. For one thing the thrust needed for a first stage is about 1.5x106 Ib; this is equivalent to a reactor of 30,000 MW. For another, the radiation field of the reactor operating in the earth's atmosphere makes Iaunching too complicated. There are ways of getting round this - placing the propellant tank behind the reactor, or Iaunching from the middle of the ocean - but the first step of a space mission, and in fact any landing or launching stage, seem ideal for the chemical system.
The relative advantages of the two propellant systems explains the use to which the NERVA engine will first be put: the third stage of the Saturn C-5 vehicle with a space mission about 1970. The flight tests preceding the mission are planned for 1967-8.
PAST, PRESENT AND FUTURE
PAST. The nuclear-rocket program started in Los Alamos and Livermore late in 1955. Feasibility and design studies were carried out through 1956. In 1957 Los Alamos took over sole responsibility for the reactor for space propulsion (KIWI, the wingless bird), Livermore concentrating on the nuclear ramjet (project Pluto). The next two years continued the technical work to the accompaniment of budgetary debates and arguments on the prospects for the programs.
In 1959 the first KIWI reactor test was held, the primary purpose being to use hydrogen in exploring the Iimits of high-temperature operation. Two further tests in 1960 extended the power levels and the operating range and brought the preliminary series to a close. This A-series configuration was not like the final design, but the tests provided the necessary information on fundamental parts of the system such as fuel-element design and reactor control.
The KIWI-B series has also had three tests (late 1961, and in September and November 1962). The B series has carried the technology to the stage of using Iiquid hydrogen in a core of virtually the final design. The last test, on Novernber 30, showed predicted reactor behavior, but the test was not run to completion because unexpected flashes appeared in the exhaust flame. The flashes are believed to be caused by parts of the thermal insulation spalling off and burning.
Two or three further tests will be run by LASL in the next few months under the KIWI part of the project. The transition to the NERVA engine will be accomplished in a test series under the auspices of LASL with Aerojet General/Westinghouse.
The KIWI tests (all of which have been done with the reactor upside-down - i. e. with the H2 being propelled upwards instead of down) tend to be run in a different way from most development series. Seldom is a test designed to explore any particular aspect. The approach has rather been to do a test and see what turns up in the analysis of the data. Each of the six tests has been of immense value, though often in an unexpected way. And, to quote LASL Test Director Keith Boyer, this gives the runs an additional feature of excitement!
All tests are carried out at the Nuclear Rocket Development Station, a desert plateau about 12 miles in diameter amidst the harsh hills of southwestern Nevada. There are two test cells for the KIWI series, with an associated MAD building for maintenance, assembly and disassembly. About half complete is the first NERVA cell (ETS-1) for the downward-firing rocket. It will be followed by ETS-2 and the associated E-MAD buitding. The ETS-I, as the picture shows, looks satisfyingly like a full-blown engine pad, with huge facilities above the core for the coolant tank and below it for the exhaust gas. It is planned for completion in mid 1964. NRDS has $60 million worth of hardware installed, with a further $90 million committed. There are 700 people who work there, this number to be tripled in the next two years.
NRDS is about 90 miles from Las Vegas, and this points out one difficulty in conducting the tests: the need for vlrtuatly all employees to drive 180 miles up and down the "Widow-maker" highway each day. Extensive investigations are in progress to see how to overcome the travel problem - e. g. building a townsite near the test station.
PRESENT. As the transition to the engineering phase is starting, the general problem is of course the blending of the reactor to standard rocketry hardware - i. e. nozzles, turbo-machinery, instrumentation, propellant tank, thrust structure and vectoring system. Some specific examples:
a) Testing the rocket the right way up. In addition to the vast heat-transfer problems of coping with the downward-directed hydrogen, care is necessary to prevent air being sucked into the nozzle and causing a hydro gen/oxygen explosion.
b) Further tests in pumping the propellant. Transferring liquid hydrogen at -400oF is about as easy a handling problem as causing water to move smoothly through a white-hot furnace. The need for non-turbulent flow is evident when one remembers that hydrogen passing near and through the core will cause pronounced effects on the neutron population.
c) Control. Instrumentation on chemical rockets has been designed for start-up rates of fractions of seconds; nuclear systems are some hundred of times slower, with cooling-down rates slower yet.
d) Radiation effects. Though radiation effects of structural materials are fairly well documented at standard reactor operating temperatures, little is known of effects at cryogenic temperatures. (Allied to this problem is the continuing in-core problems at the high temperature end of the operating range. Though the exhaust-gas temperature is a classified figure, it is clearly getting on towards the 2500oC barrier that presents a seemingly insurmountable barrier to metals and alloys. Intense gamma heating presents further difficulties. In fact, the temperature problem has been absorbing the efforts of one out of every three people working on Rover at Los Alamos. )
e) Operation in a Vacuum. The NERVA reactor tests will take place in a space environment, and one main investigation will be on moving the propellant in a vacuum.
FUTURE. The Reactor In Flight Test takes over from the NERVA stage in preparing the engine for its space fliglrt as the third stageof a Saturn C-5 vehicle. Problems here are more the "conventional" ones of rocketry- flight, stability, withstanding take-off stresses - together with the enormous size of the finished vehicle. The three-stage complex will be 348 feet high, and be as sembied in a building over 400 feet from floor to ceiling. (The Statue of Liberty, plinth and all, is 151 feet high.)
Ten RIFT stages are expected to be fabricated, two prototypes for NRTS and then three more for final testing there, one for dynamic testing with the first stages at Marshall Space Flight Center in Alabama, and four for delivery at Cape Canaveral
As for the KIWI and NERVA stages, RIFT will also need special cells and buildings at the rocket development station. The names here are E/VTS (Engine/Vehicle Test Stand)-3, 4 and 5 and the SAM (Stage Assembly and Maintenance) building. As with all the tests, remotely controlled trains will be used to move the components about.
More than the initial Rover concept is being looked at under the nuclear-rocket program. Los Alamos is pushing the KIWI reactor to higher specific impulses and increased power densities in the phoebus project planned for testing in 1964-5. Argonne is examining the various advanced reactor concepts going on round the country, mostly as in-house efforts - e. g. cavity reactors where the fuel is gaseous. Such work is being done at the Lewis Center, the Jet Propulsion Laboratory, United Aircraft and Los Alamos.
WHO lS INVOIVED. The AEC and NASA run the program under their joint Space Nuclear Propulsion office. SNPO has three extensions - at Albuquerque for Iiaison with Los Alamos, at Cleveland for administering the NERVA stage and for liaison with NASA's Lewis Research Center, and at Las Vegas (Nevada) for managing the NRDS.
Prime contractors for the KIWI stage was LASL, for NERVA is Aerojet General, for RIFT is Lockheed and for NRDS construction is Catalytic Construction. Major NERVA subcontractors are Westinghouse Astronuclear for the reactor part of the engine, AMF for remote handling, Bendix for control-system actuation and Edgerton Germeshausen Grier for instrumentation; the Lewis Center provides other non-nuclear support.
In the RIFT stage, NASA's offices come more into prominence - the Nuclear Systems Office for over all management, Marshall Space Flight Center for technical direction, and the Launch Operation Center for the flight tests.
Rover has had spent on it about $265 million since it started in 1955, and it will be a billion-dollar project before it is through. As with any such project, its viability depends on federal policy, and it seems that about six months from now will be another time of decision when budget talks roll around. President Kennedy in a somewhat enigmatic statement on December 12 made a pronouncement that many people interpret as "If the tests in the next few months are encouraging Rover wiII get a real financial stimulus. "
If the NERVA engine does not fuIfiII the promise expected of it the AEC presumably will have to accelerate the development of one of the several classified nuclear rocket programs that are now being studied.