Dream of Atomic Powered Flight



I found this article online, and, as I had done a major reaserch piece (The Decay of the Atomic Powered Aircraft Program) on the Aircraft Nuclear Propulsion program, I decided to add this to my Web. Note that this is NOT my work. -MegaZone

Well, I've gotten enough responses that I'm obligated to post this article. It was written by Vincent Cortright, and was contained within the March, 1995 issue of Aviation History.

Dream of Atomic Powered Flight

Even in 1944, while bombs were still raining down on Germany from radial-engine Boeing B-17 Flying Fortresses, planners in the U.S. Army Air Forces (USAAF) were looking ahead to a new power source for aircraft that was even more revolutionary than the German jet- and rocket-propelled fighters attacking those bombers. The USAAF got most of its information from a then ultra secret organization known only as the Manhattan Project; barely a year later the Boeing B-29 Superfortress Enola Gay dropped a single bomb on Japan that dramatically revealed to the world the terrific power of nuclear fission.

For a time after World War II the dreaded mushroom cloud was the only image the public associated with atomic power, but soon this frightening image was almost displaced by a happy "nucleomania." What the then recently discovered wonder drug penicillin was to medicine, atomic power would be to industrial society. It was envisioned that atomic bombs would be detonated over the Arctic to melt the ice cap and thus give the world a more moderate climate, an early form of global warming. There would be atomic-powered cars, trains, helicopters, cargo ships, rockets, and truck-mounted portable generators. There would even be an atomic-powered blimp, designed for the Navy by Goodyear and three times the size of its ordinary over-the-Super-Bowl blimp.

And, of course, there would be atomic-powered airplanes.

Because the airplane was virtually the symbol of 2Oth-century progress, designs for the nuclear version often were wild flights of fancy. One design was for a huge seaplane the size of Howard Hughes' Spruce Goose. Another showed what looked like a gigantic arrow with the atomic engine at the tail and the crew compartment perched far forward at the tip of the arrowhead. Then there was the "sky-train" design, in which conventional airplanes used their engines only during takeoff and landing and were towed like gliders most of the way by immense nuclear planes that stayed aloft for weeks at a time, cruising the major air routes.

But the USAAF was not interested in flights of fancy for the Cold War also had begun with the Atomic Age. The service wanted a bomber powered by a nuclear reactor that would give an airplane almost unlimited range. Just a pound of uranium theoretically could propel an airplane around the world nonstop 80 times-so great a range, a joke went, that it would only have to land periodically so the crew could re-enlist.

Officially, serious research on a nuclear-powered airplane began in 1948 with a program called NEPA-Nuclear Energy Propulsion for Aircraft. NEPA was managed for the Atomic Energy Commission (AEC) by the Fairchild Engine and Airplane Corp. Despite what the media said about the new Atomic Age, there was very little that was glamorous about NEPA. In fact, it became a sort of unwanted stepchild among government research programs. Its headquarters was a woebegone tar-paper shack behind the AEC's library in Oak Ridge, Tenn. Much more serious than that was opposition to the program from senior scientists. The noted atomic physicist J. Robert Oppenheimer was among them. He believed that a nuclear plane could not be built and advised younger colleagues about the professional danger of being associated with it.

This conflict prompted the AEC in 1948 to call for a review of NEPA by the Massachusetts Institute of Technology. Its "Lexington Report" surprised some opponents when it concluded that a nuclear plane was feasible given an overriding national interest in tackling the enormous technical problems-and as long as approximately a billion dollars was spent over 15 years to do so. The report also postulated, as future events were to prove correct, that such a long development time meant that some other technology (such as the guided missile) could render the nuclear plane obsolete by the time it was finally completed.

That was a gamble the AEC and the U.S. Air Force, renamed when it became a separate service in 1947, were prepared to take. By 1951, development had begun in earnest, with contracts going to General Electric (GE) for an aircraft-mounted reactor and to Convair and Lockheed for a suitable airframe in which to mount it. The first flight was confidently scheduled for 1956. For its part, Convair decided to modify two standard B-36H bombers, then the largest bomber in the world, to accommodate the reactor power plants. These airplanes were redesignated X-6s. A third B-36H, redesignated NB-36H, was set aside as a flying laboratory not to be atomic powered but to carry aloft a test reactor to evaluate radiation shield requirements. While they were at it, the whole NEPA program was redesignated ANP for Aircraft Nuclear Propulsion.

It was a good beginning, full of promise; but it was only when the project engineers started to closely study how to build a nuclear plane that they realized the staggering technical problems. The main problem was, and always would be, how to make an adequately shielded reactor that was still light and powerful enough for use in an airplane.

The reactor could be one of two types. The first and most widely used was the "slow" model, in which the neutrons are slowed by a bulky moderating substance, such as graphite or water to a low enough speed for a self-sustaining chain reaction to take place. This type of reactor was relatively easy to design and operate. However the shielding was usually made of a specially prepared concrete 5 to 10 feet thick and weighing about 200 tons, too much even for the heavy-lifting capability of the B-36H. The "fast" model ran on higher speed neutrons, the same kind that activate an atomic bomb. Such a reactor could be made the size of a 3 to 4 foot sphere and weigh approximately 50 tons. But the heat generated would be very high, at least 2,000 degrees Fahrenheit-four times as hot as the slow reactor. Unless the engineers made materials that could withstand such heat, the reactor would simply melt itself.

GE's solution for the X-6 was to design a single, large, air-cooled reactor that had a core of 143 pounds of uranium dioxide fuel elements riddled with air passages and sandwiched between rings of stainless steel. Four J-53 turbojet engines were manifolded to the front and rear ends of the reactor; air from the compressor sections of the jets passed directly through the core and then out the exhaust nozzles. The all-up weight of the power plant came to about 128,000 pounds, 60,000 pounds of which was shielding.

The GE design employed the so-called direct or open system. Air was ducted straight through the reactor, emerging super hot to replace the heat formerly generated by the burning of fossil fuel (such as kerosene) in the jet's combustion chamber. The reactor-jet power plant was to be mounted inside the X-6 in its aft bomb bay with the four J-53s underneath the aft fuselage in an exposed group. The total amount of shielding was divided. A large tank of water surrounded the reactor itself (water acting not only as a shield but also as a reaction moderator in the core). A circular, lead-and-steel Gamma-ray shield, 80 inches in diameter and 4 inches thick, was immediately behind the forward Crew compartment.

Even with all that shielding, a worrisome amount of radiation still could get through. For a plane designed to stay aloft perhaps weeks at a time, the cumulative effect might be too much. And it was not enough just to protect the crew; airplane parts were also vulnerable. For example, radiation will sometimes transform rubber tires into a glassy or molasses-like substance.

Despite these problems, the first serious setback to the ANP program was political rather than technological. In 1953, the Eisenhower administration was looking for ways to fulfill its campaign promise to trim the federal budget. The ANP was singled out for severe cutting. Secretary of Defense Charles Wilson claimed that even if the X-6 could be built, it would be no more than a flying platform to prove that nuclear flight was feasible-it would not be a militarily useful aircraft. "I am not interested, as a military project, in why potatoes turn brown when they are fried," he declared, a pointed reference to the ANP and what he thought was its philosophy of doing something "because it is there." Wilson also called the X-6 a "shitepoke"-a Texas nickname for a species of heron. "That's a great big bird that flies over the marshes," he explained, ".. .that doesn't have much body or speed to it or anything, but it can fly" The ANP however had some powerful friends, principally in Congress' Joint Committee On Atomic Energy "I do not care how big it is," said one representative, "and I do not care how much it costs. I want the Department of Defense to propel an airframe with nuclear power 50 feet off the ground, 20 miles an hour if need be, but move it." It was this kind of support that kept money coming through to the ANP but at a steep price. The scheduled X-6 test flight in 1956 was indefinitely postponed.

Still, even with continued funding, the question of military usefulness dogged the ANP Its rationale from the beginning had been that a nuclear plane would be the world's first true intercontinental bomber It would be able to travel supersonically from an inland base in the United States to strike any place on earth without the need for politically uncertain foreign bases or vulnerable aerial refueling. But as shielding and heat-transfer problems made completely atomic-powered supersonic flight less likely a proposal was made in 1955 for a so-called hermaphrodite system. Officially known as the 125-A weapon system, it used both conventional and nuclear power.

It was also called the "nuclear cruise, chemical dash" technique. Along with the thrust provided by the reactor-heated air from the main combustion chamber there was a separate chamber directly behind it for burning chemical (fossil) fuel only. This combination allowed the aircraft to cruise for periods on atomic power alone and, when near the target or under attack, to boost its speed with the chemical fuel to 2,000 mph for short periods.

The Air Force wanted weapon system 125-A by 1963. But project engineers soon discovered not only that the necessity of carrying liquid fuel decreased payload but also that mating nuclear and chemical engine technologies added needless complexity to a program that had yet to build a flyable aircraft. "It was as though the Wright brothers had been asked to build the F-86 Sabre Jet," said one critic. All in all, it began to appear that the projected 125-A mission could be performed much better by an intercontinental ballistic missile (ICBM), the development of which was proceeding faster than expected.

A further complication entered the AMP when indecision cropped up about the basic nuclear-engine design. The Pratt & Whitney Aircraft Division of United Aircraft, which, since 1953, had a small contract with the AEC, seemed to be making rapid progress on a design that GE had considered at the start and then rejected. It employed the so-called indirect (or closed) system, which, instead of ducting air straight through the core, transferred the reactor heat to a heat exchanger by pipes filled with a liquid metal, such as sodium. The jet's air would be heated by pipes from the exchanger and not by passing through the reactor itself-heated second hand, so to speak. The advantage of this was that liquid metal is a much better conductor of heat than air so the reactor could be made smaller and thus operate with about 50,000 pounds less shielding than the direct system.

The disadvantage, as GE was always quick to point out, was that the weight and complexity of the heat exchanger with its network of 18 miles of tubing carrying molten metal under high pressure, nearly canceled out the shielding decrease. Less quickly pointed out by GE was that the relative simplicity of the direct system had severe disadvantages as well. The shielding would have to be heavier, and, because the air would go directly through the core, far more radioactivity would be released into the atmosphere. Indeed, this problem was serious enough to warrant a separate study by the Air Force, appropriately named Project Halitosis.

Support was to swing back and forth between the two systems for several years, but, since GE was further along in its work, it was the first to build and test its design, at least on the ground. As an experiment, GE took the dependable J-47 engine, already used in the Air Force's Boeing B-47 Stratojet bomber and modified it to use a nuclear heat source. This was then redesignated the X-39 engine.

In 1955, on a test site in Idaho, the X-39 was run on a ground test stand in what was called the Heat Transfer Reactor Experiment No. l (HTRE-l). Engineers tested a complete aircraft power plant consisting of a reactor, a radiation shield, two X-39 engines, ducting, control parts and instrumentation; the whole assembly was called a core test facility because it was designed for the insertion of different reactor cores as they were developed. In January 1956, the engines were operated successfully but, because there had been no attempt to restrict the weight of the shielding, they would not have been flyable. Later in 1957, other cores that were tested, HTRE-2 and -3, did reduce the weight somewhat. The HTRE-3 assembly produced enough thrust to theoretically sustain a flight at 460 mph for about 30,000 miles. However radiation levels were still a problem; at one point in the tests, controls failed and released enough radioactivity to contaminate 1,500 acres.

This was steady but very slow progress, and what made the slowness all the more vexing to the ANP program was the relative speed and concrete results of the U S. Navy's concurrent nuclear program. Aside from minor efforts toward the atomic-powered blimp and a turboprop seaplane called the "Princess Program" after the Sanders-Roe Princess (a huge 10-engine British seaplane), the Navy's main goal was to develop power plants for submarines and surface warships. And in this they were eminently successful.

With the forceful, sometimes ruthless, leadership of Admiral Hyman Rickover, the world's first atomic-powered submarine, USS Nautilus, was launched on January 21, 1954. Progress had been rapid on that project because it was found to be much easier to float shielding than to fly it. Nautilus had the reliable Westinghouse water-moderated "slow" neutron reactor and the sub was able to submerge and run safely even with the great weight of its power plant. In comparison, an aircraft nuclear power plant would have had to be one-twentieth the size and to operate at five times the temperature.

Vexing, too, was the fact that Maj. Gen. Donald Keirn, Admiral Rickover's counterpart at the AMP project, did not have the same sweeping powers to get things done. Infighting and empire building among the Air Force, the AEC and the main contractors were needless irritations added to the already formidable technical problems. (incidentally it was Keirn, then a colonel, who had been one of the original Air Force planners of nuclear flight back in 1944.)

Not surprisingly enthusiasm began to wane for the AMP in the mid-1950s, even among its powerful congressional allies. Funding might have been canceled entirely had not the program received one final, enormous boost-on October 4, 1957, the Soviet Union launched Sputnik and beat the United States in the race to put a man-made satellite into orbit.

In the aftermath of tile launch there was near hysteria in the United States about supposed inadequacies in scientific matters. It was no secret that for years the Soviets had had their own atomic-powered aircraft program, and they had sometimes boasted of being on the verge of nuclear flight, but relatively little attention was paid to it in the West. Now things were different. "If Russia beats us in the race for atomic bombers, our security will be seriously endangered," groused Senator Henry "Scoop" Jackson, and a virtual cascade of alarmist statements burst forth. "Coming on the heels of the Sputnik fiasco," another congressman complained, "a Russian victory in this field could well prove disastrous to world confidence in America's scientific abilities"-a statement reflecting the focus on the propaganda value of winning a race and not on the United States' security in the Cold War.

Now the goal of the ANP was to rush some kind of atomic-powered airplane-even a "shitepoke" flying platform-aloft within three years. This was called the "Fly Early" proposal-the sooner the better in the view of the ANP's supporters, finer all, America's prestige was at stake.

Two years later, in 1959-a year that would be pivotal for the ANP-Washington was still debating Fly Early when the Air Force submitted another proposal for a militarily useful atomic-powered mission. This was the CAMAL (continuously airborne missile-launcher and low-level) system, in which a nuclear bomber carrying ballistic missiles would remain aloft for weeks at a time, patrolling just outside the enemy's radar range and thus supplementing the proposed submarines and land-based missiles. Such a plane also could be flown on low-level, below-radar sorties, carrying conventional bombs deep into enemy territory.

It was an ingenious and farsighted scheme, yet it failed. What turned out to be the straw that broke the CAMAL proposal was the exceptional performance of the then new Boeing B-52 Stratofortress, which made the great risk and expense of a nuclear plane much less attractive. Adding weight to those doubts was the result of remarkable advances in missile technology such as the 9,000-mile range of the then newly developed Atlas missile, which reduced the need for a flying launcher in the first place. Conversely if such an in-flight launcher was really deemed necessary the Defense Department calculated that for the cost to date of the ANP program 1,200 B-525 could be procured immediately not after more years of reactor and shield tests.

The year 1959 marked the beginning of the final decline of the nuclear airplane effort. Nine hundred million dollars had been spent on it since 1946, and not even a flying platform of any kind was near completion. Consequently President Dwight D. Eisenhower's budget message of January 1959 stated that until "the technical problems involved in operating a nuclear-powered aircraft safely are solved, there is no practical military value in attempting to build the airplane itself" and that any more money spent should be for basic research only especially research on better reactor materials. Herbert York, chief scientific adviser to the Department of Defense, was more emphatic when he declared that "no possible (within reason) ANP development program could lead to the kind of plane the military could depend on for important and useful missions before approximately 1970."

That kind of talk was anathema to the ANP's supporters in Congress. In a bid to rally support, on July 23, 1959, the Joint Committee on Atomic Energy began an unprecedented series of public hearings about the program; there had been only closed sessions (36 of them) up until then. The forces lined up for the debate were considerable, with Keirn and York leading, respectively the side for the nuclear plane to "Fly Early" and the side for the "Go Slow" option-the latter advocating a policy of concentrating more on basic research rather than racing the Soviets for what would be militarily useless nuclear night. "I think it is high time that we nail down once and for all what is meant by 'usefulness,"' retorted a congressman on the ANP side. "From my own point of view and that of the working engineers in the field, the most useful thing we can do at this point is to test out the propulsion system in actual flight as soon as possible."

Keirn, agreeing, asserted that even a primitive airplane would provide valuable test data; the barely adequate reactor materials that would have to be used could be replaced later by improved ones when they were developed. To which York responded that an airplane built now would divert money from the very research program developing those improved materials. And when (or if) they were developed, substitution into a primitive system might not be practicable. 'A change of materials in a reactor is not a minor thing," he said. "The only difference between a tennis ball and an orange is a matter of materials."

Just as in the case of the Lexington Report submitted 11 years earlier the result of the hearings surprised opponents of the nuclear plane, but this time pleasantly the public debate had unexpectedly caused support to wane for the ANP so much so that by May 1960 the program only narrowly won a vote (19 to 18) of the House Appropriations Committee to continue its funding (mainly due to the efforts of a then little-known member from Michigan named Gerald Ford). After the November presidential election, Eisenhower decided to let the incoming administration of John F Kennedy have the final say on the fate of the ANP.

Not only a new administration was ushered in but also a new way of thinking about government policy especially in the area of national defense, Kennedy's appointment of Robert McNamara as the new secretary of defense epitomized that shift. Formerly president of Ford Motor Co., McNamara had been told by Kennedy "to take a fresh look at everything and make it better" and what he looked at were the defense programs that might pass his cost-effectiveness test. He defined this as the maximization of military capabilities through the rational allocation of available resources-getting the biggest bang for the buck.

McNamara was a systems analyst who believed that most of the significant items of a defense program could be reduced to computer-processed numbers. Brought to its logical conclusion, this outlook came close to saying that, since the atomic bomb had changed the rules, now war itself need not be fought-it could be managed, instead, just like Ford Motor Co, As for the ANP it did not pass the cost-effectiveness test. McNamara wisely felt the need to distinguish between what was possible and what was needed, between what could be done and what should be done. Instead of the nuclear plane, he wanted to increase appropriations for ICBMs-to end the so-called missile gap-and for conventional war capabilities without greatly enlarging the Eisenhower-designed defense budget. The decision was made that the ANP not merely be cut back but rather be canceled entirely.

After briefly considering whether to continue development of Pratt & Whitney's indirect-system engine, Kennedy agreed to the cancellation, and in his March 28, 1961, national security message he said that "nearly 15 years and about l billion dollars have been devoted to the attempted development of a nuclear-powered aircraft; but the possibility of achieving a militarily useful aircraft in the foreseeable future is still very remote,.. .We propose to terminate development effort on both approaches on the nuclear power plant...and will avoid a future expenditure of at least a billion dollars which would have been necessary to achieve first experimental flight." Shortly afterward, the ANP program was terminated.

And that was that. Neither the United States, nor the Soviet Union, nor any other country was ever able to develop a true atomic-powered aircraft. But a nuclear plane of sorts did manage to fly This was the NB-36H test airplane, authorized along with the X-6 design back in 1951. Its original B-36H airframe had been extensively modified, most notably with a 12-ton shielded crew capsule in the nose, a 4-ton lead disc shield in the middle and a number of large air intake and exhaust holes to cool the reactor in the aft section. The reactor was a 1000-kilowatt design weighing 35,000 pounds and situated in a removable mounting in the aft bomb bay Its operation was observed from the crew capsule by closed circuit television. When the plane was not being flown, the reactor was kept in a specially prepared pit near the runway at Convair's Fort Worth, Texas, facility.

NB-36H flew with its radioactive cargo 47 times between 1955 and 1957, and, although it did not power the airplane, the reactor provided considerable data on the effects of radiation emitted during night. Flying alongside NB-36H on every one of its flights was a Boeing C-97 Stratocruiser transport carrying a platoon of armed Marines ready to parachute down and surround the test airplane in case it crashed. This certainly deserved hazardous duty pay. Pity the poor troops assigned to this outfit, jocularly dubbed the "glow-in-the-dark platoon." Fortunately there never was a crash, and the test plane was eventually decommissioned at Fort Worth in late 1957. After languishing as a hulk for many months, it was scrapped.

This was a somewhat ignominious end for a program that had begun with such giant visions. The fatal flaw as McNamara and others pointed out, was that a small, light, high-powered and adequately shielded reactor had not been developed. In retrospect, it is clear that the Air Force should never have been involved in designing an airplane until the AEC had completed work on the reactor.

The Air Force planners had simply been hypnotized by the prospect of a fistful of uranium powering a bomber around the world. It might have given them pause to consider the fact that radiation from the biggest atomic reactor of them all, the sun, falling as light rays on the area of an airplane's wings, might have provided enough power to fly at high speed-if all the radiation could have been harnessed effectively.

Weblint Validated!
Image: Valid HTML 4.0!
  © Copyright 1997, MegaZone, megazone@megazone.org Revised Saturday April 29, 2000 19:34 EDT