Investigation of a Sodium Vapor Compressor Jet for Nuclear Propulsion of Aircraft

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This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency Thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

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Portions of this document may be illegible in electronic image products. Images are produced from the best available original document.

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IMVESTIGATION OF A SODIUM VAPOR COMPRESSOR JET FOR NUCLEAR PROPULSION OF AIRCRAFT ATOMIC ENERGY RESEARCH DEPARTMENT

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REPORT APPROVED BY: S. SIEGEL, Associate Director C. STARR, Director AF Plant Representative, Burbank AF Plant Representative, Seattle ANP Project Office, Fort Worth Argonne National Laboratory Armed Forces Special Weapons Project (Sandia) Atomic Energy Commission, Washington Battelle Memorial Institute Brookhaven National Laboratory Bureau of Ships California Research and Development Company Carbide and Carbon Chemicals Company (ORNL) Carbide and Carbon Chemicals Company ( Y - 1 2 Plant) Chicago Patent Group Chief of Naval Research Commonwealth Edison Company Detroit Edison Company Foster Wheeler Corporation General Electric Company (ANFP) General Electric Company, Richland Hanford Operations Office Idaho Operations Office Iowa State College Knolls Atomic Power Laboratory Los Alamos Scientific Laboratory Massachusetts Institute of Technology (Kaufmann) Monsanto Chemical Company National Advisory Committee for Aeronautics, Cleveland National Advisory Committee for Aeronautics, Washington Naval Research Laboratory New York Operations Office Nuclear Development Associates, Inc. Patent Branch, Washington Pioneer Service & Engineering Company San Francisco Operations Office Savannah River Operations Office, Augusta USAF Resident, East Hartford University of California Radiation Laboratory, Berkeley University of California Radiation Laboratory, Livermore Vitro Corporation of America Walter Kidde Nuclear Laboratories, Inc. Westinghouse Electric Corporation Technical Information Service, Oak Ridge

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TABLE OF CONTENTS Summary of Views Relative to the Attainment of Supersonic Flight with Nuclear Powered Aircraft A. Discussion of Technical Assumptions B. Effect of Airplane and PowerPlant Performance on C. High Temperature Approach. E. Present Status of Compressor Jet. Sodium Vapor Compressor Jet LIST OF TABLES I. Possible Reactor Coolants for High Temperature Application. II. Possible PowerPlant Working Fluids for High Temperature III. Airplane Design Conditions IV. Airplane Weight Breakdown. VI. Neutron Cycle F ronnE pi thermal Calculations.... VII. Fate of 100 Fission Neutrons in Reactor...... VIII. Reactor Cooling Characteristics and Weight.... IX. PowerPlant Performance Characteristics.....

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LIST OF FIGURES 1. Effect of L / D Ratio on Airplane Gross Weight 43 2. Schematic Diagram of Compressor - Jet System 44 3. Temperature - Entropy Diagram for Sodium ........ 45 5. Three Views of Airplane 47 6. Inboard Profile Perspective of Airplane 48 7. Engine Thrust and Airplane Drag vs Mach Number. ..... 49 8. Thrust Horsepower vs True Air Speed. ......... 50 9. Rate of Climb and Climb Speed vs Altitude ........ 51 11. Reactor - Power Plant Installation 53 12. Temperature Entropy Diagram for Sodium Compressor Jet... 54 13. Sodium Vapor Generator. 55 14. Compressor and Turbine Assembly. 56

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Analysis indicates that, in order to achieve supersonic flight with nuclear powered aircraft,are actor - powerplant combination capable of operating at tem - per a ture s considerably in excess of current practice must be developed. It is pointed out that there exist two general avenues of approach toward the goal of attaining high temperature reactors and powerplants.The first approach involves the continuation and augmentation of research along the lines pursued by the conventional turbo - jet engine nn anu fact u rer,namely a search for material coatings or materials that will retain structural strength in high temperature ox i - di zing atmospheres.The second approach seeks to take advantage of the peculiar characteristics of the compressor - jet engine that permit the operation of the high temperature components in anon - oxidizing atmosphere. The results of a preliminary design study of a supersonic aircraft powered by a high temperature sodium,liquid vapor compressor - jet engine are summarized. The analysis considered,inasmuch detail as was warranted by the limited ex per - innental information available,the characteristics of the reactor,powerplant and airframe involved in determining performance.This study has been conducted for the purpose of guiding future,long - term,research work along the lines of high temperature reactors and powerplants for aircraft propulsion.The sodium vapor compressor - jetis not presented as an engine that is presently considered feasible nor is any attempt made to establish a timetable for its development. The present status of reactor - powerplant combinations of the type discus - sed in this report is such that the configurations presented and the thermodynamic requirements set forth are highly conjectural.However,in light of the prom - ising results thus far obtained from very limited experimentation in the field of high temperature materials not subject to oxidizing atmospheres, it appears worthwhile to continue a research effort along these lines in the expectation of making high temperature,high performance aircraft a reality. This report is based upon studies conducted for the Atomic Energy Com - mission under Contract AT - 4 0 - 1 - GEN - 1064.These studies were concluded on September 1, 1951, and were informally made available to the Aircraft Nuclear Propulsion Group at ORNL at that time.

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I. SUMMARY OF VIEWS RELATIVE TO THE ATTAINMENT OF SUPERSONIC FLIGHT WITH NUCLEAR POWERED AIRCRAFT Before discussing in detail the sodium - vapor compressor jet, it seems worthwhile to discuss briefly the reasons for the interest in compressor jets in general and the sodium-vapor compressor jet in particular. These arguments have to do with assumptions which a r e made in connection with the feasibility of obtaining any desired performance of aircraft, including engine performance act eris tics such as the ratio of lift to drag, and reactor performance in terms It is now public knowledge that nuclear powered airplanes are considered feasible and that specific contracts are being negotiated with turbo - jet engine and aircraft companies, for the design and construction of the necessary apparatus. The technical decisions which culminated in the above mentioned actions are many and diverse, but perhaps the ones of greatest weight were those reached by the Technical Advisory Board as recorded in the report issued as a summary of the work done at ORNL in the s u m m e r of 1950. The members of the Technical Advisory Board recomm.ended immediate action on the engineering p h a s e s of subsonic airplanes on the grounds that such airplanes are reasonably certain of success, and that such a successful subsonic airplane is a desirable and necessary prerequisite to a high performance super - sonic airplane; and, further, that the reactors and turbo-jet engines which can propel a subsonic airplane at a maximum reactor temperature of 1500° F can also by further development (largely one of attaining higher operating t e m p e r a - tures of about 1800° F)reach a level of performance required by a supersonic As to the feasibility of the subsonic nuclear energy propelled airplane and the need for building such a subsonic airplane as quickly as possible, t h e r e should be little further discussion because there can be few doubts of a technical nature concerning the soundness of the decisions.

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However, the question of whether or not a 300° F increase in reactor wall temperature can be accomplished and if so, would it provide sufficient improve - ment in performance to propel supersonic airplanes, is one which is still open. In the language of the Technical Advisory Board, "Obtaining supersonic performance later may be expected as the result of further development. It depends on the solution of crucial problems with respect to materials, fabrication, and the airplane and engine developments. The time scale for solution of these problems cannot now be predicted. "The gaps in our knowledge of the properties of materials at high temper - a ture s are so wide, and the basis for predicting the rate of progress in this field so uncertain, that there are wide differences between the estimates of experts as to what ultimate working temperatures the various reactors are likely to attain. Consequently, the success of the whole project, at least for Phase II, may conceivably depend on the development of a propulsion system with somewhat reduced requirements for specific impulse and temperature. Such a development, though not insuperably difficult in principle, presents a major undertaking in view of the extent of the engine and airplane development resources now available. "The liquid metal cycle has a fair chance of operating in the range of max - t e r i a l s could probably be used near the lower end of this range and feasibility could be established within a short time. Temperatures in the upper part of this range would require research of indeterminate duration and unknown chances of success. This cycle may be expected to operate a plane satisfactorily, with prospects for high ultimate per for a i ance if reactors operating near the upper end of the above range can be developed. " While the Technical Advisory Board felt itself unable to make any estimates as to the time involved in the attainment of a supersonic airplane,a similar de - gree of caution did not pervade the technical field where assumptions were made and calculations gone through which resulted in estimates of airplane and power plant weights and performance. Such estimates are, of course, only as good as these technical assumptions which were made in fields where the experts are probably of as diverse views as those in the field of high temperature materials. Thus, it may be pointed out that the feasibility of the nuclear powered supersonic airplane is by no means as well established as that of the subsonic airplane.

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Therefore, it is of importance to the whole program to arrive at a thorough understanding of those airplane and power plant characteristics which indicate that the Technical Advisory Board ' s 312, 000 pound, 1800° F reactor temperature, turbo-jet powered supersonic airplane for Mach 1. 5 at 45, 000 feet is of m a r g i n a l A. Discussion of Technical Assumptions The cautious optimism of the Technical Advisory Board (TAB) report on supersonic feasibility as compared to the more doubtful attitude of the Lexington report was largely due to the reduction in airplane gross weights which resulted from the more optimistic assumptions that: 1. Airplane cruise L / D ratio would be around 6 at Mach 1. 5 and 45,000 feet instead of the 3 obtained by the X - 1 . By use of the split shield, the shield weight could be materially Turbo - jet engines can develop enough thrust with a maximum reactor temperature of 1800° F and still be of low weight. Analyses made for this report indicate that there are technical reasons which make some of this optimism difficult to justify. 1. Lift / Drag Ratios - Detailed analyses of preliminary designs of large supersonic airplanes (300, 000 pounds to 500, 000 pounds gross weight) with all the nuclear power plant in the fuselage, thereby eliminating nacelle drag, has so far indicated that the best cruise L / D r a t i o for Mach 1. 5 at 45, 000 feet is about 5, and that there is nothing presently known aerodynamically to justify a more optimistic figure for large airplanes at this flight condition. 2. Power Plant - Power plant analyses based on TAB data indicate that turbo-jet engines to power a 300, 000 pound supersonic airplane having a r e a l - izable L / D of 5 at Mach 1. 5 and 45, 000 feet will require reactor temperatures TAB. This results from the fact that turbine inlet temperatures several hun - dred degrees higher than the 1500° F figure currently attained in operational turbo-jet engines are necessary to get the additional power required from e n - gines of a weight compatable with that of the airplane.

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The difficulty of attaining even 1800° F in the reactor led the TAB to think that perhaps the problem of coming up with new designs for high performance from lower temperatures should be passed to the aircraft and engine builders. In other words ". . . the success of the whole project, at least for Phase II, may conceivably depend on the development of a propulsion system with somewhat reduced requirements for specific impulse and temperature. " It seems doubt - ful that higher performance airplanes can depend for success on lower perform - ance powerplants. Up to now, at least,this has not been the trend in airplane and powerplant development. It does not appear,however,that full realization exists of the effect on airplane gross weight of the use of lower temperature,lower performance engines. Such realization has been obscured by the optimistic assumptions of cruise L / D ratios which in turn produce optimistic airplane gross weights. Of course, if extremely large airplanes of a gross weight of about 500, 000 pounds and upward are acceptable,then the objections to low performance powerplants are of less B. Effect of Airplane and PowerPlant Performance on Gross Weight The effects of cruise L / D ratio and reactor temperature upon airplane gross weight are shown in Fig. 1. These curves are based on TAB data. It i s apparent that, if gross weights are to be kept below400, 000 pounds,higher tem - per a ture s and higher performance engines must be used,even upon the TAB demonstration of the effect of L / D on m cixi mum reactor wail temperature,consider the TAB point shown on Fig.1 and assume it is desired to maintain the same air - plane gross weight at an L / D ratio of 5instead of 5. 67, In this case,the maximum at 45, 000 feet. It should be pointed out that North American Aviation studies wall temperature at 1800° F with L / D ratio of 5, an airplane gross weight of 420, 000 pounds is required for Mach = 1. 5 at 45, 000 feet.ForL / D = 4. 5, which may be a more reasonable value,maintaining constant gross weight requires a weight of 62 0, 000 pounds.