Convair NB-36H (USAF)
A Brief Case History of
the Air Force Aircraft Nuclear Propulsion Program
and Its Future Implications
by Clyde D. Gasser, Colonel, USAF
Published 5 Nov 2023
Convair NB-36H (USAF) |
Several articles and documents have been prepared for a number of reasons on the USAF Aircraft Nuclear Propulsion Project (ANP) since its cancellation in early 1961. Some of these have been written for the record in terms of applicable technical events, fund expenditures, etc.; some have been published on lessons learned in management or mismanagement; and still others on the pro and con generalities of the program. Because of my charter affiliation in the ANP venture, I have read these publications with great interest. Interestingly enough, I have found that most have been relatively objective in fulfilling their basic intent; the remainder have been mildly or heavily biased. As expected, throughout an appreciable percentage of these writings, a flavor of scientific-technological sin and wickedness, and how-not-to-do-things prevails. |
An Assessment
As an amateur student of history it has for some time been my feeling that most history is written largely by people who have had nothing or very little to do with it in terms of actual events that occurred. It is also apparent in writing history that viewing matters from their peripheries is far more meaningful and interesting than from within. Presumably this position arises from the time-honored axiom that (from within) "one cannot see the forest because of the trees." Notwithstanding this evidence and at the risk of committing a serious transgression of well-established conventionalism, I have decided to record briefly in the following paragraphs a case history of the ANP program both "from within and from without." In so doing it is my sincere hope that in addition to negative lessens already recorded, a few points on the positive side will become obvious. I am also hopeful that it will tend to identify self-evident technological implications of the ANY program, which although quite possibly not appreciated if indeed even recognized during its closing years, remain available and should be quickly capitalized upon in aid of enhancing our future national posture in space. In this vital area, nuclear power is one of the key elements in ensuring our superiority.
The Past
The ANP program had its beginning during the closing months of 1945 and the first half of 1946. The United States had achieved an all-time high in power and prestige; while World War II had been won and the victory achieved should be a lasting thing, traditionally it was incumbent on the Armed Forces to look ahead and devise even more modern ways and means to insure that peace would be maintained, or should war again occur, that our side would win. During the war it had become crystal clear to all that military air power had emerged as a key element, the future of which would undoubtedly pace and control the welfare and destiny of any country or combination of countries.
Technological achievements brought about during the war including the jet engine, significantly improved aeronautical engineering techniques, an expanding gamut of electronics, conventional armaments, and many other things had enhanced almost immeasurably the capabilities of aviation. They had also stimulated the imaginations of research and development and operational people in the Air Force and the other services on behalf of an even greater potential that lay ahead. Part of the stimulus of these people arose from their own imaginations; another part was due to the scientific-technical speculation and challenge outlined in the documents "Towards New Horizons" developed at the request of General H. H. Arnold by Dr. Theodore von Karman, then the Chairman of the Air Force Scientific Advisory Board. Of all the stimulus at hand, however, probably the greatest point that had arisen was via the spectre of atomic energy manifested in the dropping of atomic bombs on Hiroshima and Nagasaki just prior to the end of the war.
During this period and within the elements of the Air Force concerned with research and development matters, one of the most serious problems in need of a new and different solution was that of how to improve markedly the overall performance of aircraft thereby extending the operational capabilities of bombers, fighters, interceptors and the range capabilities of other types of aircraft including long range transports. Along with a desire for extension in range w also the hope to achieve greater speeds at very high altitude or, as the case may be, on the deck where detection would be minimized and penetration survival substantially increased. If chemical fuels were to be employed, however, the realization of any substantial increase in range was not technically compatible with other performance criteria mentioned except by somewhat complex air refueling techniques.
The relatively newly acquired gas turbine, whether in the form of a turbojet or turboprop had high fuel consumption characteristics compared with piston engines and, in addition, only operated at its best at altitude. Quite clear, therefore, was the necessity for an intensified search for a fuel that would provide both high heating value and lasting qualities. A number of new chemical fuels had been thought of and experimentally tested under some complicated cookbook processes. Included were gaseous and liquefied hydrogen, powdered metals suspended in petroleum products, and the addition of a variety of other exotic chemical ingredients including a by-product of TNT, in both kerosene and gasoline. While some of these fuels or their facsimiles have since proved useful in rockets for missile applications, their total burning duration was and remains a matter of minutes thereby falling seriously short of the hours required for aircraft missions.
Because of this deficiency, the advent of the atomic bomb quite understandably sparked the imaginations of other than only those persons charged primarily with weaponeering. For the first time, there appeared to exist a possible quantum step in the solution to performance problems of the aircraft-propulsion system designer. A tremendous heat source existed in the nuclear fission process which, if it could be harnessed, would provide aircraft flight duration of days and possibly soon weeks without refueling. It could conceivably also simultaneously provide greatly enhanced speed capabilities. While it was not clearly apparent what could be done about adapting nuclear energy to aircraft propulsion, there certainly existed engineering know-how in reactor technology et a number of universities and in the U.S. Army Manhattan Engineer District (MED) by virtue of reactors already built and operated successfully at Chicago, at Oak Rridge, Tennessee and at Hanford, Washington. In addition there existed a very significant store of knowledge and accomplishment at Los Alamos, Now Mexico in nuclear physics, chemistry, metallurgy and engineering that had led to the design and development of the original experimental bomb tested at Alamagordo and the two models used later on Japan.
Among those attracted by this idea was Colonel Don Keirn (now retired as a Major General), who was assigned to the Power Plant Laboratory at Wright Field. Already an expert in aircraft propulsion matters and a top-flight engineer, General Keirn together with his immediate staff undertook a study and analysis of engine-nuclear reactor combinations including both turbojet and turboprop versions with a view toward establishing theoretical feasibility. His considerations also extended, though to a lesser degree, into possibilities of nuclear powered ramjets and rockets. Concurrently with the efforts of General Keirn and his staff, at Air Force Headquarters in Washington where I was assigned in the Engineering Division, Office, Deputy Chief of Staff for Materiel, we had also entered independently into the same type of speculation. While we had examined in general terms the possibilities of the application of nuclear power to aircraft and missile propulsion systems, it was not until General Keirn, together with Headquarters representatives, had further discussions with MED authorities in Washington, D. C., at Los Alamos and elsewhere, that it was concluded that a formalized program of research and experimentation pointed at feasibility determination would be in order.
While this conclusion was a point in progress, ways and means to put a program into motion were not immediately apparent. The principal reason for this was that within the Air Force itself there existed almost no technically trained personnel to carry out such a venture, much less the specialized facilities within which to design and fabricate parts or conduct experiments. Except for certain consultation services provided to MED by Colonels R. C. Wilson (now retired as a Lt General) and M. C. Denier (now a Maj General) and a few others on the development of the atomic bomb, the Air Force had not participated in nuclear affairs and for all intent and purposes was literally an "atomic outsider." Fortuitously or not (historically speaking), at this point the Air Force was approached by industry with proposals attending the adaptation of nuclear energy to aircraft propulsion. Evaluation of these proposals took place first at Wright Field by General Keirn and his staff and subsequently at Air Force Headquarters under the direction of Maj General 'Pop' Powers and Brig General Alden Crawford (both now retired). As a result, the Fairchild Engine and Airplane Company was selected as the Air Force contractor to carry out a feasibility study of an aircraft nuclear propulsion system. General Spaatz, Commanding General of the U.S. Army Air Forces, and Mr. J. Carlton Ward, then with Fairchild were especially instrumental in negotiations.
This move was definitely a further point of achievement, but it was still not a solution as to how to actually get underway with a program. There remained the very formidable issue of conducting any work involving the use of uranium, using applicable MED facilities or, for that matter, even the part-time services of nuclear scientists or engineers in the employ of MED or its contractors without the approval of General Leslie Groves, the Commanding General of MEB. There were some obvious reasons for these restrictions including stern guidelines from the White House, the very small national stockpile of uranium at the time, and the limited number of experienced and capable people who could be called upon to carry out nuclear work. After a fairly lengthy period of discussion and negotiation, it was, however, agreed that the Air Force and its contractor, Fairchild, could begin work in some unoccupied buildings on a small tract of land identified as the S-50 Area at Oak Ridge, Tennessee. There were a number of provisos included in this agreement but it did permit a start.
The formalized program got underway at Oak Ridge early in 1946 under the name of the Nuclear Energy Propulsion for Aircraft (NEPA) project, The project continued to grow in a gradual manner throughout the period extending to mid-1948 by which time a considerable number of engineers, craftsmen and administrative people were in the employ of Fairchild. The contractor's efforts were being devoted to problems ranging from theoretical studies to limited hardware design and experimentation in the area of possible reactor-engine-shield combinations. Various composite propulsion systems were examined on paper, and a umber of parametric airplane designs using these propulsion systems were also considered. Brig General T. A. Sims (a retired Air Force Brig General) had become the General Manager of Fairchild operations at Oak Ridge. I had been transferred to Oak Ridge in the spring of 1947 and was and was assigned to the project as Air Force Engineering Officer reporting primarily to the Chief of the Power Plant Laboratory at Wright Field. In addition, I was obligated to report to General Curtis E. Lemay, then Chief of Air Force Research and Development at Air Force Headquarters and to Rear Admiral T. C. ('Ted') Lonnquest, Navy Bureau of Aeronautics, which was financially contributing to the program. I was also held responsible to work closely on project matters with MED authorities at Oak Ridge.
As mentioned earlier, the Air Force and its contractor had entered into activities at Oak Ridge under a considerable number of restrictions. Some of these proved to be handicaps to progress in that they gave grounds to frequent denials by authorities at Oak Ridge to Fairchild requests to conduct experiments in the large graphite reactor located there and in other existing laboratory facilities. There were also accounting and numerous other administrative problems bearing on the apportionment of costs for items and services ranging from electrical power to hospitalization. However, largely through the imaginative accomplishments of Major Don Grant, the on-site Air Force Contracting Officer and his assistant, Mr. Jim Gray, we manage, to acquire things needed to progress.
The aforementioned circumstances still did not comprise all of the troubles at hand ‑ far from it. An additional feature of note was a continuous critique of our efforts by a sort of free-lance scientific group that had appeared from rather peculiar quarters and whose views were entirely gratis. We were told by these experts that an airplane using a nuclear I soot- for power could never fly successfully because of the weight of shielding required and that oven if it could fly, the entire crew might well be seriously injured by nuclear radiation, probably along with everyone on the route ever which it might fly. Intermixed with this type of advice was another version and in this instance significantly more valid by Admiral H.G. Rickover, who at the time was serving at Oak Ridge as a Captain, where he was busy acquiring nuclear knowledge which later was to make him famous. The Admiral's remarks were to the effect that the Fairchild studies involving complete propulsion systems and airplanes were in error. Far more realistically, he said, we should concern ourselves principally with reactor materials studies and experimentation, the development of an optimum complex of nuclear fuel elements, controls, shielding techniques and other pertinent features. In retrospect, Admiral Rickover was quite correct on several of the points that he made.
Such criticisms and advice were something that we came to accept as a way of life. We failed, however, to take into account their accumulative effect because they helped materially to bring about the first serious soul-searching investigation of the NEPA project in the late summer of 1948. This investigation was launched basically at the request of the Atomic Energy Commission, which had succeeded MED. In due course a group of scientists, engineers and others was assembled via a joint agreement reached between the AEC and the Air Force, and after several weeks of briefings, study and deliberation, the group's findings were published in a document entitled the Lexington Report. While the report did not state that a nuclear powered airplane was unattainable, it left little doubt but that nuclear flight would not occur soon, and that if it did fly it would not be earlier than 20 years hence and even then would be of questionable value. The net result of the issuing of the Lexington Report was about as would be expected; the Air Force contractor was somewhat shaken up, and the freelance critics became even more active. I was particularly concerned regarding the reaction of many of the capable people in the employ of Fairchild. A degree of depression was certainly apparent, however, somewhat like a hangover, it wore off before too long; being replaced with an even greater determination by most to get on with the job.
Official Air Force reaction to the Lexington Report was mixed, nevertheless, there was little doubt in the minds of most but that the NEPA project should be continued. At the same time it was also deemed appropriate to undertake more selective effort in aid of providing answers to basic or semi-basic problems including materials, reactor core technology, reactor control systems, shielding and the like. General Keirn, Colonel Wassell and others at Wright Field did much to ,affect this reorientation and Fairchild collaborated fully primarily due to the understanding and cooperative attitude of General Suns. A new Technical Director had appeared on the scene at this time in the Fairchild organization at Oak Ridge, Dr. Miles Leverett. Also, under the able direction of Dr. Larry Hafstad (now with General Motors), who had been appointed as the new Director of Reactor Development in AEC, Washington offices, support within the AEC laboratories at Oak Ridge and elsewhere on behalf of the NEPA project improved to a very gratifying degree.
By the spring of 1950, the rate of progress in demonstrating feasibility was at a state where, in the opinion of the Air Force at least, it could be said that a reasonably sound position had been reached. This did not mean the Air Force felt that it could proceed to develop a finished product in the same sense that a airplane using conventional chemical engines could he built. The marriage of a nuclear reactor and an airplane indeed presented many engineering difficulties, and even the relatively uninformed recognized that much work still lay ahead. The real point that seemed to have been arrived at, therefore, was that it woe clear that a level of understanding had been reached based on which it appeared possible to design and build an operationally safe and geometrically sized reactor that could produce the necessary thrust under controlled conditions to propel an airplane. Equally important was the belief that required shielding could be devised in a sufficiently compact package or packages to protect the crew and vital equipment and payload carried in the aircraft from nuclear radiation from the reactor. It was felt that the shielding would also be light enough to permit fairly reasonable aircraft performance. This opinion was obviously in conflict with the Lexington Report findings and was also at odds with the views of the loyal freelance opposition.
In the opinion of the Air Force it was also becoming apparent that the position of technological accomplishment they believed was at hand really represented one of departure to the next programmatic phase. Fairchild as a contractor had performed quite satisfactorily under a series of severe handicaps. However, since it was now generally the Air Force intention to go ahead with tie design and fabrication of an experimental full-scale nuclear propulsion system, to be followed (hopefully) later with an experimental airplane, its position was that some other element of industry (than Fairchild) having the capacity to more effectively and efficiently deal with such a task should be brought into the picture. It should not be construed that anything was wrong with Fairchild's performance in meeting its contractual obligations. Fairchild's history in the aviation industry nevertheless evidenced wide diversification on a relatively small scale in each instance, and not enough big plant and manpower capability in those areas considered vital to the success of the foreseen nuclear powered flight program. It was deemed appropriate therefore that a new contractor should be selected to carry out phase II of the program. Along with this contemplated move, I was "transferred" overseas to Great Britain as an Exchange Officer to serve in the Royal Air Force.
Before I returned to America in the summer of 1952, several significant things occurred. The General Electric Company had been selected by the Air Force as the new aircraft nuclear propulsion contractor and had set up shop in Evendale on the outskirts of Cincinnati. Fairchild operations at Oak Ridge had been brought to a halt. A special organization had been established to accommodate the project by GE identified as the GE Aircraft Nuclear Propulsion Department under the supervision of Mr. D. Roy Shoults. The project name had been changed by the Air Force from NEPA to Aircraft Nuclear Propulsion (ANP). Along with these events was the temporary disappearance of General Keirn to the year's course at the National War College at Ft. McNair in Washington and his reappearance in the ANP program in a new capacity. In his new post, namely that of Chief of the Aircraft Reactor Branch in the AEC, General Keirn occupied a position comparable to that of Admiral Rickover who, by that time, was serving as Chief of the Naval Reactor Branch in the AEC. General Keirn had also acquired a second "command hat", i.e., that of assistant for nuclear matters to the Commander of the Air Research and Development Command. The Power Plant laboratory at Wright Field was functioning; as an agent of General Keirn in the execution of ANP contractual matters from the Air Force side of the house with GE and with Convair at Fort Worth, Texas. There had also been established at Wright Field an ANP office in the Center's Directorate of Weapons Systems to deal with problems of study and foreseen design and development of an entire airplane system. In general, therefore, there had appeared during this particular period a markedly different ANP management and research and development complex within the Air Force, the AEC and industry.
At the GE Evendale facility the approach was one of theoretical effort, design study and experimentation, and fabrication and test of components on behalf of a practicable reactor-engine-shield combination on a basis of one of the propulsion system cycles that had been under consideration at Oak Ridge. Work progressed rapidly notwithstanding the fact that there existed a shortage of money, men and facilities. Not too long after I returned to America (in the summer of 1952), the next major programmatic upheaval occurred. It seems as if GE had arrived at what they and the Air Force considered to be an experimentally useful aircraft nuclear propulsion system design, and, simultaneously, an appropriate aircraft application. The price tag attached to this venture being somewhat formidable caused the whole idea to be brought up through channels for approval of the (then) Secretary of Defense, the Honorable Charles E. Wilson. The ultimate result of this maneuver was almost catastrophic. Mr. Wilson took an extremely dim view of the entire approach and directed that any thought of building and flying such an airplane should be shelved, and that the entire ANP program should be reoriented to a level of effort attending only materials and components investigation and experimentation. This directive proved (to put it mildly) to be somewhat embarrassing to General Keirn, his staff, the Air Staff at Air Force Headquarters and the AEC. The freelance critics were nothing less than ecstatic over Mr. Wilson's decision in that the Air Force had been put right scientifically once more.
After returning to America I talked to several people in and outside the ANP program in order to get a better appreciation of why Mr. Wilson rendered the decision that he had. Without exception, no one believed that the decision announced was his own. Much more likely, I was told, pressures had been brought to bear on him by certain members of his organization in the DOD who were opposed to the program and that he therefore was essentially only the spokesman. Upon my return from the RAF I attended the Armed Forces Industrial College at Ft. McNair in Washington. Just prior to the end of the school year I was approached by General Keirn and Colonel Wassell with a proposal of an assignment in the ANP program. In brief, General Keirn wanted me to join his staff in Washington; however, the Personnel Department at Headquarters USAF, curiously enough, disapproved the idea. Because of this it was agreed that I should join the General's staff with duty station at Wright Field as the Chief of the ANP Division which was attached to the Weapons Systems Directorate, then under the command of Colonel Homer Boushey (now a retired Brig General). My job would be that of acting as his chief Air Force representative at the Wright Field level to help insure that effort at the Center and at applicable contractor facilities was brought to bear in the most effective manner.
During my year's tour at the Industrial College many additional notable things happened in the program. The GE facility at Evendale was expanded and the AEC had undertaken the construction of facilities for testing experimental GE propulsion systems at the AEC National Reactor Test Station at Idaho Falls, Idaho. The AEC also had undertaken at Oak Ridge design and experimental effort in the area of shielding and another propulsion system approach differing appreciably from the course being pursued by GE. The Air Force had enlarged its facility at the Convair plant at Fort Worth, Texas and a contract was also in force with Pratt & Whitney for the study of still other nuclear propulsion system concepts. As the time neared for me to rejoin the program, I was warned by General Keirn not to generate any radical ideas relative to designing and building a nuclear powered airplane regardless of how good it might appear to be. He made it especially clear that he was still in the process of recovering from the Wilson edict and wes, therefore, in no humor to experience a repeat performance. I obviously understood this warning and, with every good intention to comply with it, again set to work in July 1953 on nuclear propulsion affairs.
From the summer of 1953 to the summer of 1955 not only did the program progress on all fronts but, towards the end of this period, we had all but forgotten the earlier decision rendered by Mr. Wilson. During the last half of 1953 I had endeavored to follow carefully the instructions given to me; however, at the outset of 1954 and thereafter, progress was made at such a rate that my staff and I were ultimately able to convince even General Keirn that the program was rapidly approaching if indeed not already at the point where there could be undertaken the design and development of an attractive prototype aircraft. There was a host of reasons contributing to this feeling and I shall not take the time or apace to record the details here. In general, they included the achievement of some rather significant steps in materials techniques, reactor and shielding technology, determinations in radiobiology, some unique reactor-engine combination engineering ideas, and the sifting out of airplane designs to a few that appeared to have real potential. There had also been successfully flown a modified XB-36 with a live and fully controlled 1 megawatt reactor in it, along with adequate crew shielding. In addition, there had developed considerable enthusiasm in applicable segments of the aircraft industry concerned with the building of complete nuclear powered airplanes rather than simply the conduct of research and the development of pieces and parts.
The net result of this was the undertaking of a campaign which, in partnership with Colonel Dill Maxwell, Chief of the Bomber Division, of the Weapons Systems Directorate, was carried up through various echelons to the Air Staff at Headquarters USAF. This particular episode occurred under the direction of brig General Howell Est.., (now a Lt General) my new Commander, who had replaced General Boushey as Director of Weapons Systems activities. The proposed airplane in mind was a heavy-weight quite obviously lending itself primarily to the Strategic Air Command mission. It had fairly good speed characteristics (on paper) and its range was phenomenal when compared with its chemically-powered contemporaries. Our efforts eventually paid off and it was concluded by the Commander of the Air Research and Development Command, General T. S. Power (now Commander-in-Chief, SAC) and others that the program should go ahead on a weapon system basis pointed at the ultimate introduction of nuclear powered bomber aircraft into the SAC inventory.
This move was considered sufficiently important to bring about the establishing of the Directorate of Nuclear Systems in lieu of the Division that I had been operating and, organizationally, to also appreciably increase the complement of personnel. I was relieved of my command, which was taken over by Colonel Wassell, who was simultaneously promoted to a Brig General. I accepted a new post offered to me by Brig General 'Lud' Bryan, Commander of the Wright Air Development Center, as his Deputy Commander for research matters and also as Director of Research. My entire staff was transferred to General Wassell's Directorate except for a few very able officers, including Colonel John Hood and Lt Colonel Bent Howard, who accompanied me to the Directorate of Research and assisted in undertaking among many other things, investigation in the areas of radiation effects and shielding in aid of the ANP program.
The pattern of affairs that followed was equally if not more interesting than any or all of the foregoing events. Effort at the propulsion system contractor's plants was intensified and sharper definition was given to experimentation, tests and development in order to arrive at specific engineering designs pointed at final subassemblies and subsystems that would be used in a prototype airplane. Shielding work at Oak Ridge was focused on more precise configurations resembling crew compartments, and the entire spectrum of ground support items was pinpointed and examined. Work in the area of nuclear radiation damage investigations at the Air Force facility at the Convair plant at Ft. Worth, Texas was given special attention in aid of arriving at workable solutions for crew compartment layouts and equipment design and its integration into a nuclear powered aircraft. There was considerable additional work undertaken involving the investigation of test facilities, ground hazards, crew training and possible flight facilities. The remaining big issue at hand was that of the complete airplane configuration since it was the end item for which everything underway was being done. Several design studies were undertaken and completed extending appreciably beyond the nature of similar work accomplished while I still had the ANP Division at Wright Field.
At this point a new and more serious trend of events was beginning to appear in the form of stringent aircraft operational requirements as seen by Air Force planners. Air Force Headquarters quite rightfully was continuing to define new and increased performance requirements in terms of range and speed for all types of military aircraft to cope with the estimated enemy threat. It was the speed criteria of these particular requirements that was causing the difficulty as far a concerned nuclear powered aircraft. It did not take long to determine that the newly established performance needs were seriously incompatible with the capabilities of the best nuclear powered aircraft design that had been produced. The basic reasons for this disparity were manifold; however, very briefly they amounted simply to the fact that reactor technology in hand or immediately foreseen would permit the generation of only a given level of heat, which, transferred into terms of thrust output of engines, would provide a, most only relatively modest airplane speed. There was technically no opportunity to squeeze out more nuclear power without the possibility of a disaster and the unacceptable consequences that such an event would entail. Even with chemical fuel augmentation the results were less than acceptable, and it was quite obvious therefore that nuclear powered aircraft design capabilities in hand or that could be forecast with any real confidence could not meet established requirements.
Perhaps an error was made at this point in not retreating from the competition with other weapon systems in trying to meet the advanced performance needs as established by the requirements people and, instead, taking a different tact by proposing nuclear powered aircraft as an experimental venture, or, in systems areas having leas stringent performance requirements such as reconnaissance or logistics. It also might have been an error for Bill Maxwell and me to undertake our campaign back in 1955 when we first began to sell the nuclear powered weapon system concept. Whatever errors that may or may not have been made, it was concluded approximately at the outset of 1958 by the Commander of ARDC and the Air Staff that the full-blown weapon system approach should be appreciably slowed down. General Wassell's organization at Wright Field was disbanded and he was transferred to a new post. The people in his organization gravitated largely to General Keirn's shop located in the AEC complex at Germantown, Maryland, or to his office in the Pentagon, and into various echelons of ARDC.
Under this again reoriented set of conditions, attention was devoted to propulsion technology and "bread-board" tests by GE at Evendale and at Idaho Falls and more soul-searching was done by the aircraft contractors than in the program as to possible ways and means to improve airplane performance. Work at Convair and at Oak Ridge o radiation effects and shielding was curtailed along with generally similar investigations at Lockheed's nuclear facility that had appeared at Marietta, Georgia. In addition to these aspects, a new propulsion system investigation had bean initiated and was being carried on by Pratt & Whitney near Hartford, Connecticut. I continued to follow intimately events in the ANP program as an interested onlooker. I had been transferred from Wright Field at the outset of 1958 to Headquarters AFDC (now AFSC) at Andrews Air Force Base to the post of Director of Experimental Vehicles. In this relatively adjacent location, as in my subsequent (and present) assignment at USAF Headquarters as Secretary of the Air Force Scientific Advisory Board, it was opportune to maintain frequent liaison with General Keirn and his staff.
One of my interests in ANP had to do with nuclear rocket possibilities inasmuch since I was concerned in my directorate with space vehicles (including the then existing Air Force Man-in-Space program), and with advanced airplane concepts. In my contacts during this period I was continuously curious regarding the decision to pursue the ANP program on a weapon systems basis in view of events that had occurred at the close of 1958. It seemed fairly obvious to be far more realistic to attempt to gain support for the program on a basis of an experimental vehicle, the flight tests of which would provide the Air Force with an excellent opportunity to judge its value as a system. Apparently I failed to understand the problem since General Keirn and others seemed to have good and valid reasons to follow such a course of action. To give final credence to General Keirn's position on this matter, he had the backing of top management inasmuch as it has been reported that just before the late Assistant Secretary of Defense, the Honorable Donald Quarles, passed away, he had given approval to go ahead with the actual building and flying of a nuclear powered airplane. Not long after this General Keirn retired from the Air Force and Brig General I.L. Branch took over the direction of the program.
Sometime after the death of Mr. Querles (in May 1958), the findings of an ANP investigation launched by Dr. Herbert York, then Director of Defense Research and Engineering of DOD, were reported on during open hearings in Congress. This occurred during July 1959 and, in testimony presorted to members of the Joint Coccaittee o Atomic Fhergy
of Congress by the Honorable Mr. Gates (who had succeeded Mr. Quarles) and by Dr. York, it was made clear that the DOD intended to go ahead with only an applied nuclear propulsion research and experimental program, shielding and work on other attendant subsystem elements, and that the design and construction of an airplane would not be undertaken in the foreseeable future. Dr. York outlined for Congress the extent of money spent thus far (almost a billion dollars) on the NEPA and ANP programs. He also gave his opinion on how effort in the program to be pursued should be oriented, and emphasized that any premature undertaking of the development and construction of an airplane would entertain a fund investment several times more than that already spent. The testimony presented by Mr. Gates and Dr. York was not particularly well received by the Joint Committee since it had long been the opinion at that level that the Air Force should accelerate the development and flight of a nuclear powered airplane.
The final chapter of the ANP program was written in March 1961 when the President in his budget message to Congress announced that the program to build and fly a nuclear powered airplane was to be cancelled. It was also stated that certain research effort in the area of materials and selective reactor experimentation would continue and would be directed at improvement of (so-called) state-of-the-art. The principal reasons given were essentially that: (1) to develop nuclear powered flight article would require again as much and probably much more money than had already been spent on the program; (2) if and when developed, a nuclear powered airplane would be marginal or less than marginal in performance when compared with other systems available or coming along; and (3) funds for military purposes should be spent where they would achieve best results in overall national defense. Needless to say, this decision resulted in an interesting admixture of remarks embracing expressions of consternation, criticism, satisfaction and relief. Individuals from essentially every imaginable level were involved including the White House, Congress, various echelons of DOD, contractors, the press, a variety of reactionary periodicals and, last but certainly not least, the old, OLD original group of freelance critics.
Since then I have many times thought about the ANP program from beginning to end and have rehashed it with informed persons in an attempt to at least satisfy myself regarding the overall program, pattern followed, possible errors made, and the ultimate decision reached to cancel the building of a nuclear powered airplane per se. From my point of view, I think most would agree that a fully objective assessment is not easily arrived at on any of these points; however, to state a view at this ,juncture, I concur generally with the decision reached to cancel the program for the reasons stated. Alternatively, I am convinced that the nuclear powered airplane that was finally on the drawing boards would, technically speaking, have flown successfully even though possibly not competitively (depending on the operational mission considered), had the program been continued through 1965. I feel even more strongly that had this course been taken, very valuable direct or secondary benefits would have been realized on behalf of a currently badly-in-arrears nuclear power program for application to our national space needs.
The Present and the Future
In as effort to illustrate and clarify the significance of nuclear power in space applications, as the initial forerunners of our manned space program the chemically propelled (or launched) X-15 and Mercury vehicles have been a relatively immeasurable boon to our national posture and sense of accomplishment. These programs and their associated successful flights accomplished thus far by highly skilled pilots have done much to negate the national feeling of "second best" brought on by earlier Soviet space flights. The most recent Soviet effort with Vostok III and IV spacecraft has added new prestige and capability to the USSR; however, Mercury flights to follow, together with the execution of the Gemini and X-20 programs will again more than balance the books in our favor. As inspiring as any of these ventures may be, all will pale in the light of the hoped-for success to accrue in the landing of manned spacecraft on the moon. A manned lunar landing represents a deadly serious contest between this country and the Soviet, with the winner quite possibly being provided with the ultimate capability of world control.
From a technological point of view, the international space effort underway and foreseen is in several respects without precedence. Probably the greatest single element of uniqueness is the introduction of man into environmental conditions that are biologically and physiologically foreign and in some instances hostile to him. Problem areas already identified are numerous with more yet to be uncovered in exploring and (hopefully) facilitating the functional usefulness and safety of man in space. Long term space flight and/or operations on the moon are of special concern, wherein but to mention a few, the effects of weightlessness, lengthy periods of relative inactivity - (bearing on muscle tone and skeletal decalcification) and radiation from solar flares or other sources are viewed as being acutely or chronically deleterious and, in certain instances, possibly even fatal. To these must be added. an array of additional serious problems bearing on assuring a constant supply of oxygen, a well-regulated cabin environment, the removal of odors, toxic contaminants and waste, and an adequate supply of food and potable liquid.
The one if not the greatest underlying requirement for successful spacecraft and lunar operations is massive amounts of power. Primarily these needs arise in terms of boosters (launch vehicles) and where applicable, for staging to ensure ultimate flight patterns desired. Power is also needed to insure safe reentry into the earth's atmosphere, and for deceleration purposes attending lunar landings, with follow-on relaunch for return to space stations or to the earth's surface. The future will hold even greater demand: for power in aid of placing tens or hundreds of thousands of pounds of payload in orbit, or for landing an the moon or on other planets. A still further power requirement will have to be satisfied to facilitate maneuvering of spacecraft (at will) from their normal flight patterns.
Essentially the entire booster program currently being pursued or being talked about for the future is chemical in nature, employing liquids or solids as fuel. Specific impulse is a key element, in all booster performance, and since there exists a fairly well-established upper limit to what can be achieved chemically, the principal avenue open to improvement is to go to larger sizes, clustering and/or more staging. The only existing significant exception to this approach is that being pursued at a relatively slow pace and without applicational direction in the nuclear propulsion area. The development thinking in this instance is primarily founded on a very marked improvement possible over chemical rockets in terms of specific impulse. Limitations are imposes however, and it is currently conceded that operation with such rockets must be confined to outside the earth's atmosphere due to fission product contamination and post-operation radioactivity problems. Further difficulty is also present due to radiation hazards to spacecraft crews and to sensitive equipment or payloads present, although shadow shielding techniques may well largely alleviate this situation.
The approach to auxiliary power units for spacecraft and for remote use such as on the moon is to an appreciable extent similar to that being pursued in the instances of boosters and staging in that it is chemically based. The major exceptions are via the current SNAP approach and in the area of solar cells. Battery power, while having worked well in its applications thus far, cannot fulfill many future needs where power demands are high, or where equipment operating requirements are even modestly high and of long duration. SNAP concepts and solar cells differ from batteries in that life span limitations are such as to meet essentially adequately all foreseen requirements. Limitations are apparent in the SNAP radioisotope/thermocouple method and in solar techniques due to the low efficiency in the transition from temperature to electrical output. Consequently, the achievement of compact and lightweight auxiliary units through the latter means for use in spacecraft having high power demands, currently appears unlikely. The location of such units on lunar surfaces offers possibilities provided the economics of transportation prove to be a practical thing. Regardless of their use in spacecraft or on lunar surfaces, additional investigation will be in order to determine radiation damage susceptibility from solar flares and possible other sources.
Insofar as concerns future needs in space for primary booster power, it is clear that an imaginative and energetic program should be undertaken to explore fully ways and means to improve the design and performance of existing concepts, and to evolve now concepts with significantly improved capabilities. Major performance improvement possibilities available for exploitation in the area of chemical boosters are not readily apparent, but there may well exist opportuniities to realize several modest improvements through the incorporation of certain additional materials (solids, liquids or gas) into the basic fuel complex in aid of achieving higher specific impulse. Total performance improvement may also be enhanced by the incorporation of variable nozzle designs, throttling features and highly selective segmentation techniques. Across-the-board improvement can be realized by giving greater attention to design simplicity, reliability and unit cost reduction. A relatively significant improvement may arise from effort in the "Spaceplane" concept area thus achieving a better method to launch spacecraft and at the name time retain the basic launch vehicle for repeated reuse.
The area of chemical staging is grossly similar to that of primary boosters in that design geometry, fuels used and controls are relative. The same pattern of possible improvement exists therefore, and should be energetically pursued. The area of staging, however, offers considerable probable latitude wherein a potentially really attractive opportunity exists to employ nuclear propulsion. As cited earlier, use of this type of propulsion is presently visualized as being confined to operations beyond the atmosphere because of radiation problems. This need not be a particularly difficult problem if nuclear powered staging is properly designed and incorporated into the total system complex in a manner that will prevent it from reentering the earth's atmosphere in its initial configuration.
Nuclear propulsion for in-space use is foreseen as not being confined solely to staging for achieving earth orbital or lunar mission flight. It also holds the potential for in-flight maneuvering and for facilitating rendezvous, docking and in-orbit launching. Design features incorporated in the graphite-core Rover concept hold considerable promise for such uses and this promise will be even further enhanced if impervious coatings or ceramic liners for working fluid passages can be realized. Metallic or ceramic core reactors hold equal promise and should be explored fully to insure the exploitation of all potential means of meeting either staging or in-flight propulsion needs. The entire area of fast or very fast reactors should be given a thorough assessment since from this may well result design concepts of particular interest and use, especially in military spacecraft. An additional possible advantageous approach may lie in nuclear rocketry employing a core design that is burned chemically (from the aft forward) in combination with fast nuclear reaction and the simultaneous injection of hydrogen or other working fluid. Specific impulse achievable may be exceptionally attractive.
Of currently equal if not greater importance in our national space program is the requirement for auxiliary power. If man in space for advanced scientific and for military purposes is to be truly realized, auxiliary power systems must be developed that are not only compact, reliable and simple in design, but that also have the capability of constant or variable high power output over long periods of time. They must also have low-maintenance and easy and quick-replacement characteristics, This aggregate of requirements arises directly from the need for a departure from the current "storables technique" and the accompanying urgent requirement to evolve completely reliable and adequate regenerative life support and associated fully-functional operational systems. With these requirements apparent, it is fairly obvious that the best solutions may lie in the nuclear power area.
In aid of furthering the realization of advanced auxiliary nuclear power systems for spacecraft and for lunar surface purposes, it may therefore be especially rewarding to examine designs with (some) excess uranium investment. Core poison bleed-off ideas and techniques should also he examined. Through these approaches it may be possible to extend appreciably the period between reloading and attendant complication and hazards. If in addition there can be designed core reloading features and techniques embracing a "package approach" the accompanying mechanical difficulty and radiation danger to humans, sensitive equipment or payload present can be even further reduced. Fuel element, moderator matrix and reflector designs and their combinations should be given special attention in an effort to facilitate optimum simplicity, reliability and maintenance-free operation. The control complex should receive similar attention and should incorporate features permitting manual, remote command or automatic adjustment.
An additional area associated with nuclear power for space application in need of attention is that of shielding and radiation effects. The crew and/or any sensitive equipment or payload aboard must be shielded from nuclear radiation emanating from nuclear rockets or auxiliary power units used. Similar protection must be provided in the instances of nuclear power applications for lunar surface operations. Since weight is a premium item in space, and since shielding is characteristically heavy, a thorough examination must be made of shield material combinations and configurations to achieve minimum weight and bulk. Shadow shielding techniques appear especially useful and should be fully exploited. Scattering due to atmospheric conditions will obviously not present a problem, however, adjacent vehicle structural scattering (or lunar surface scattering) will have to be considered and guarded against. Optimized shadow shield geometry and location can probably be depended upon for protection. It may also prove advantageous from a shadow shield concept to consider selective excess reflector design features for onboard nuclear auxiliary power units. Cross section dimensions of such power units will undoubtedly be small and the resultant weight penalty arising from excess reflector features will thereby be minimized.
While not associated with nuclear rockets or auxiliary power units used for space purposes, in considering radiation effects and attendant shielding for such purposes there must also be borne in mind the need for protection against naturally occurring radiation, i.e., solar flares, Van Allen belt effects, and radiation from possible other sources. Shadow shielding may not be entirely adequate in these instances and this concept together with other more complete shield configurations and possible advantageous flight patterns and associated maneuvers should be investigated in the light of radiation intensity spectrums present.
It is my opinion that there is a great deal in common in nuclear power engineering technology ultimately realized in the ANP program and power requirements that must new be satisfied to insure superiority in this country's future role and mission in space. If we are indeed to engage in sophisticated manned and unmanned space flight, the development of nuclear power for a variety of reasons will be requisite. I can only deplore the dispersion and virtual loss of the very extensive and capable group of expert people available when the ANP program was brought to a close. Positive steps should be taken at the highest level to recoup this talent wherever possible, and a significantly expanded and selectively-constituted national nuclear power program for scientific and military spacecraft and lunar operational requirements should be undertaken at the earliest possible time, I am convinced that in the latter instance (military space applications), there is an indisputable and pressing need to develop fully operational capabilities in the reconnaissance, defense, offense, and command and control areas if our American way of life is to survive.
Note of Appreciation
I should like to express my sincere appreciation to Lt Colonel Kent Howard for his thoughtful and objective editorial assistance, and to Mrs. Helen Manthos for her excellent secretarial services. — CDG
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