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STATEMENT OF GEORGE H. McLAFFERTY, PROGRAM MANAGER, UNITED AIRCRAFT RESEARCH LABORATORIES; ACCOMPANIED BY GEORGE HAUSMANN AND JAMES PATTERSON
Mr. McLAFFERTY. Mr. Chairman and gentlemen, my name is George H. McLafferty. I am program manager for the gaseous-core nuclear rocket program which has been in progress at the research laboratories of United Aircraft Corp. during the past 5 years.
I am accompanied by Mr. George Hausmann and Mr. James Patterson.
I am pleased to have the opportunity to appear before this committee today, since it is our belief that the gaseous-core nuclear rocket offers a most unusual potential for economic space transportation in the future.
Today I will discuss the basic features of gaseous nuclear rockets and the program which is being conducted to investigate their characteristics.
Because of security restrictions the discussion will be severely limited. It is, therefore, recommended that additional classified information be presented to the committee in an executive session so that you may judge for yourselves the status of the work on gaseous
First, many of the features of a gaseous nuclear rocket are no different from those of a solid-core nuclear rocket, and I have here a sketch which probably looks very similar to the sketches Mr. Harry Finger has shown you on solid-core nuclear rockets. (See fig. 1, p. 27, of accompanying prepared statement.) There is the usual array consisting of a tank, pump, turbine, and radiation shield. There is a cavity which is surrounded by a moderator reflector and a pressure shell. There is an exhaust nozzle. However, we have as a goal the same kind of performance as Dr. Taylor with his Orion project rather than the performance of a solid-core nuclear rocket. We would like to obtain values of specific impulse between about 1,500 and 3,000 seconds. Although we see ways of improving the specific impulse of gas-core rockets above 3,000 seconds, possible to 10,000 seconds, let's look at the relatively lower values first.
For a specific impulse of 1,500 seconds, the exhaust velocity would be about 45,000 feet per second, or about 30,000 miles an hour. The temperature upstream of the nozzle would be about 10,000° F.
For a specific impulse of 3,000 seconds, the exhaust velocity would be about 90,000 feet per second, or about 60,000 miles an hour, and the temperature upstream of the nozzle throat would be about 30,000° F. These are all quite high numbers compared to what you are used to.
Because the temperatures in this region are so high, it brings us to the first problem, which is protecting the walls from the hot gases. It is obvious that if you put gases at a temperature of 10,000° to 30,000° F. next to a solid material it will melt and boil in no time at
We have done enough work to make us think we can protect the walls, and we can discuss the techniques we would use later in executive session if you wish.
The second problem is concerned with fuel-loss rate. In order to make a device like this work we have to have a certain minimum critical amount of nuclear fuel in it. This minimum critical amount is a function of the geometry and a lot of other factors, but for a diameter of approximately 8 feet it tends to be about 5 kilograms, or 11 pounds. We would have to have 11 pounds of nuclear fuel in the cavity, and this fuel would have to be in gaseous form because of the high temperature involved. If we consider an engine diameter of 25 feet, the amount of nuclear fuel required for criticality would be about 20 kilograms, or about 44 pounds, and again this would have to be in gaseous form.
If we were to let this nuclear fuel mix with the hydrogen propellant which comes out the nozzle, there would be a tremendous loss rate of fuel. For every pound of hydrogen coming out the nozzle at high velocity there would be roughly one pound of fuel along with it. Now, nuclear fuel is very expensive, about $7,000 a pound, so that if we were to use a configuration where the hydrogen and fuel were intimately mixed we would lose all the economic advantages we could gain by high temperatures and high specific impulses. Therefore the second problem is to find a means of keeping the nuclear fuel and propellant apart so that the propellant will go out the back at a high velocity and yet the fuels will stay in for an acceptable period of time.
Economic studies have indicated that we would like to keep the propellant-flow rate to something like 500 or a thousand times the fuel-flow rate. If we can do that we can have a truly economic space transportation system which would allow us to go single stage from the earth to nearby planets and some fairly distant planets. Development of such a rocket engine would completely revolutionize the cost of space transportation.
We have carried out a lot of work on several schemes to try to minimize the loss rate of nuclear fuel. I can't discuss these in open session, but I will give you some details later in a closed session.
As we have said, there are the two problems: Keeping the wall cool and keeping the fuel from flowing out the back. We are in a research phase in our attack on these two problems. We have been at it for 5 years, and we have spent about $212 million.
Mr. FULTON of Pennsylvania. Mr. Chairman.
Before you leave the description
Mr. McLAFFERTY. Yes, sir.
Mr. FULTON of Pennsylvania. Could you distinguish this from a solid core?
Mr. McLAFFERTY. Well
Mr. FULTON of Pennsylvania. What is the chief difference?
Mr. McLAFFERTY. The chief difference is the following: In a gaseous-core nuclear rocket the nuclear fuel is in gaseous form and hence its temperature is not limited, whereas in a solid-core nuclear rocket the fuel has to be in solid form which limits its temperature to 4,000° or 5,000° or 6,000° F. I am not sure exactly what tempera
gram. This limitation on the maximum temperature of solid materials is the factor which limits the temperature of the hydrogen propellant, and which, in turn, limits the velocity of the exhaust dow and limits the specific impulse to something on the order of 700 to a thousand seconds. However, if we can drive the exhaust temperature up 10,000° to 30,000° F., we can obtain the exhaust velocities which correspond to very high specific impulses and which are required to obtain economical space transportation. But at 10,000° to 30,000° F. the fuel has to be in the form of a gas. Mr. TEAGUE. Mr. Bell.
Mr. BELL. May I ask a question here?
What prevents the, as you call it, fuel, the gaseous fusion, from going out with the propellant? Is there some reason? Is that classified?
Mr. McLAFFERTY. That is classified, yes.
In the current research phase of the investigation, we have spent approximately $800,000 of company money. In the period 1961 to 1963 we spent a little over a million dollars of Air Force money. We are now in the middle of two different NASA contracts totaling about $600,000. We have spent approximately half the NASA money to date, and all of it will be used up by September of this
The $800,000 of corporate expenditure is a measure of the faith that United Aircraft Corp. has that such a device can be built. It is a major percentage of this total and is an example of free enterprise pushing something they think will work.
We have obtained encouraging results in this research phase of the work, which is all I can say in an unclassified session. However, we obviously must have a few problems left or we would be ready to build one right now. We feel that the research part of this program should continue for between 2 and 5 years more, and at the end of that time we hope we will be in a position to recommend a demonstration program or a development program. We do not think the country should be putting any money into a development program yet because it is too early to guarantee that this device will work the way we believe it will. We are pretty sure it will work but we cannot guarantee it to the point of recommending the expenditure of very large sums of money.
However, we have done some thinking about the Nation's ability to test gas-core nuclear rockets when such engines get to the demonstration and development phase. (See fig. 2, p. 29 of accompanying prepared statement.) We would use a facility that might operate something like this: The high-temperature exhaust gases from the gascore nuclear rocket engine would be diluted by dumping in water from an upper pond during the test. The resulting mixture would be at a temperature of approximately 150° F., where the water would exist in the form of liquid rather than in the form of steam. The mixture would be carried down to a lower pond. If this engine produced a thrust of several million pounds and were tested for a minute, the total amount of water which would be required would be about 50 acre-feet. That means a pond having an area of one acre and a depth of 50 feet. I mention this to indicate that
the amount of water required would fill a pond, but not a large lake.
At the end of the test, all of the water and fission products and any unburned fuel would be in the lower pond and would be pumped back over a period of time through a circuit to the upper pond. This circuit would include a separator, where all of the_fission products and unburned nuclear fuel would be removed. By employing a separator we can completely prevent contamination of the atmosphere during routine tests of gaseous nuclear rockets.
Mr. FULTON of Pennsylvania. Where is your exhaust on that diagram?
Mr. McLAFFERTY. It is pretty much a closed system. That is, we would pump the exhaust products in the lower pond through the separator, remove the material we didn't want in the circuit, and dump the remainder back into the upper pond.
Mr. GURNEY. Have you done any testing yet?
Mr. McLAFFERTY. We have carried out fluid mechanics tests at low temperature to investigate the containment and wall cooling problems of gaseous nuclear rockets. I can describe the results of those tests to you in a closed session, if you wish.
We do not show this sketch to indicate that we want to build anything like this right now. We only show this sketch to indicate that we believe that the test problem will not limit development of gas-core rockets.
In conclusion, it is obvious that we are very enthusiastic about gaseous nuclear rockets. By this we don't mean that work should stop on more immediate space propulsion concepts. Chemical rockets and solid core rockets will have to be used for a number of years to come. In addition, a lot of the technology which is required for the development of gas-core rockets is being generated in the process of working on solid-core rockets, and in the process of working on high-pressure chemical rockets. Therefore we feel that this work should continue because we hope to be able to use. the results in future work on gaseous-core nuclear rockets. The gas-core rocket in a sense is an advanced graphite reactor, because we would probably use graphite as a major material within the engine.
We do feel strongly, however, that the results to date indicate that the work on gas-core rockets should be accelerated. We have very encouraging results, which, if they continue, will lead to successful development of a gaseous nuclear rocket engine. Such a development would save the national space program many billions of dollars.
I believe that concludes the presentation.
Mr. BELL. I understand that, as you said, we are again developing the type of transportation that you have indicated in this type similar to Orion. You spoke about 2 to 5 years that it would take you to study this.
Mr. McLAFFERTY. We are now in a research phase. At the end of an additional 2 to 5 years of such research we would not have a flyable engine, but we would hope to have sufficient evidence to justify de
schedule that the Project Orion personnel have talked about, where they are talking about when they would fly the engine. We are talking about when we would get the evidence necessary to justify a development program. We think our development program might be relatively easy to carry out, but the final flight date is uncertain.
Mr. BELL. As you may know, there has been in the form of an amendment a suggestion that the NASA allocate a certain amount, $12 million, to be exact, additional funds for research in this area for gaseous-core development. Would that be a help to you?
Mr. HECHLER. Would you yield? That wouldn't be additional. Mr. BELL. Excuse me; not additional. An allocation of the funds that NASA already has. It would be an additional indication to this particular job from funds NASA already has, which is gaseouscore research and development.
Mr. McLAFFERTY. Yes, sir.
Mr. BELL. That will be of some considerable help to you, will it? Mr. McLAFFERTY. Oh, it would. We now have about $600,000 worth of contracts from NASA, but Mr. Finger's office, besides supporting us, supports work at the NASA Lewis laboratories, as well as at several other places. Their total, I believe, right now is considerably more than one and a half million dollars in advanced propulsion. But
Mr. FINGER. Not on the gaseous core. There is about one and a half million dollars going into the gaseous core, including administrative operation.
Mr. BELL. This would be an additional one and a half million that was suggested to be used in this area, too.
Mr. McLAFFERTY. This would undoubtedly help us. I am sure that it is probably good to assume that we wouldn't get all of it ourselves, but we could very effectively use any part of it that came our
We have outlined a program to the Space Nuclear Propulsion Office for fiscal year 1965, which would cover work in all these different fields, from the field of fluid mechanics, which still represents the key problem area, right through to some material work, some work on conceptual engine design and some work on the facility which might eventually be used to test gaseous nuclear rockets. We have recommended this level of effort at United Aircraft Corp. research on three bases: One, we have the people pretty much on hand with the training necessary for them to immediately start work on the various problems. This is important.
The second basis is that an enlarged level of effort would give the same output per dollar spent as now exists. It is not the kind of a program where, if you double the funding, you get 10 percent more information out of it. We feel that the output per dollar would be the same for the increased program as for the program we now have. The enlarged program would, as a result, squeeze down the research time so that we can get at the development earlier and get at the advantages to be gained by economic space transportation earlier.
The third basis is that we feel that this level of effort is warranted by the amount of money that would be saved in the national space program if a gaseous nuclear rocket worked.