The audio is a bit fuzzy, but I didn’t know anything with a nuclear engine ever flew until I saw this:
Image: the HTRE-3, Heat Transfer Reactor Experiment, without supporting structure. From the ATS forum:
Under the ANP program the General Electric Co., at Evendale, Cincinnati was issued a contract to develop a direct-cycle turbojet, and Pratt & Whitney Aircraft Division of United Aircraft Corp. was authorized to study an indirect cycle and work was started at the Connecticut Aircraft Nuclear Engine Laboratory (CANEL). In the direct air cycle air enters through the compressor stage of one or more turbojets. From there the air passes through a plenum an is directed through the reactor core. The air, acting as the reactor coolant, is rapidly heated as it travels through the core. After passing through the reactor the air passes through another plenum and is directed to the turbine section of the turbojet(s) and from there out through the tailpipe. An indirect system is very similar, except that the air does not pass through the reactor itself. After passing through the compressor the air passes through a heat exchanger. The heat generated by the reactor is carried by a working fluid to this heat exchanger. The air then passes through the turbine and out the tailpipe as above. The working fluid in the indirect cycle is usually a dense fluid, such as a liquid metal, or highly pressurized water. This allows more heat energy to be transfer, thereby increasing the efficiency of the system. …
General Electric ran a series of very successful experiments using the direct cycle concept. These were referred to as the Heat Transfer Reactor Experiment (HTRE) series. The series involved three reactors, HTRE-1 through HTRE-3. HTRE-1 became HTRE-2 at the conclusion of its test program. HTRE-1 (and therefore HTRE-2) successfully ran one X-39 (modified J-47) solely under nuclear power. HTRE-3 was the closest to a flight article the program came. It was solid moderated, as opposed to the earlier reactors which were water moderated, and it powered two X-211s at higher power levels. HTRE-3 was limited by the two turbojets, but it could have powered larger jets at even higher power levels. The system was called XMA-1. HTRE-1 was principally a proof of concept reactor. HTRE-1 achieved a number of full-power runs that demonstrated conclusively the feasibility of operating a jet engine on nuclear power. HTRE-2 was simply HTRE-1 modified to test advanced reactor sections in a central hexagonal chamber. In this way new reactor designs could be tested without the need to build a totally new reactor from scratch. The experience gained from HTRE-1 and HTRE-2 was used in the construction of HTRE-3. HTRE-3 was the final test item designed to prove the feasibility of producing an actual aircraft powerplant. The design and testing of HTRE-3 has advanced the direct-cycle program beyond the question of feasibility to the problems of engineering optimization. …
The HTRE either met or exceeded their goals, but although all had reactor cores of roughly the size needed to fit into an aircraft, none of the HTREs were designed to be a prototype of a flight system; the series showed that it then appeared “possible and practical with the technology in hand to build a flyable reactor of the same materials as HTRE-3 and similar in physical size.” Despite the fact that HTRE-3 didn’t produce the power that would have been needed for flight, that was mainly because it was not an optimized design; it was designed simply as a research reactor, to prove the concepts needed for a flight article. At the end of the HTRE run the probability of flying a reactor seemed high. The test runs showed that a reactor using the same materials as HTRE-3, and which could power a gas-turbine powerplant, could have been built at that time.
In april 1959 GE stated that studies indicated that the basic XMA-1 power plant was suitable for the CAMAL mission. Studies by both Convair and Lockheed on the CAMAL airplane based on design objectives for the XMA-1C (Expected to use an advance fuel element of iron-chrome-aluminum or ceramic material. The turbine inlet temperature was expected to be 1700 degrees F, producing about 42 000 pounds of thrust at static sea level conditions.) power plant indicated the possibility of attaining such an airplane. GE proposed that, after the airplane had been checked out on chemical power plants, the XMA-1A (Planned to operate with nichrome fuel elements at a turbine inlet temperature of about 1500 degrees F, producing about 26 000 poundss of thrust at static sea level conditions) would first be tested, to be followed by testing of the XMA-1C power plant. As a consequence of a program reorientation in July 1959, work on the XMA-1A powerplant was canceled in August 1959. – ATSForum
See Dreams of Nuclear Flight for available declassified info. Here is a summary from a few different Wikipedia entries:
The X211, also known as the J87, was a nuclear-powered turbojet engine designed to power the proposed WS-125 long-range bomber. The program was started in 1955 in conjunction with Convair for a joint engine/airframe proposal for the WS-125. It was one of two nuclear-powered gas turbine projects undertaken by GE, the other one being the X39 project. The X211 was a relatively large turbojet engine of straight conventional layout, save for the combustion chamber being replaced with a heat exchanger. It featured included variable-stator compressors and an afterburner. A single nuclear reactor was intended to supply heat to two X211 engines. In 1956, the USAF decided that the proposed WS-125 bomber was unfeasible as an operational strategic aircraft. In spite of this, the X211 program was continued for another 3 years, albeit with no target application. It was finally terminated in mid-1959, and by 1961, all funding for nuclear propulsion was canceled.
In the 1950s, interest in the development of nuclear-powered aircraft led GE to experiment with two nuclear-powered gas turbine designs, one based on the J47, and another new and much larger engine called the X211. The design based on the J47 became the X39 program. This system consisted of two modified J47 engines which, instead of combusting jet fuel, received their heated, compressed air from a heat exchanger that was part of the Heat Transfer Reactor Experiment (HTRE) reactor. The X-39 was successfully operated in conjunction with three different reactors, the HTRE-1, HTRE-2 and HTRE-3. Had the program not been cancelled, these engines would have been used to power the proposed Convair X-6.
The X-6 would have been powered by General Electric X-39 engines, utilizing a P-1 reactor. In a nuclear jet engine, the reactor core was used as a heat source for the turbine’s air flow, instead of burning jet fuel. One disadvantage to the design is that since the airflow through the engine was used to cool the reactor, this airflow had to be maintained even after the aircraft landed and parked. GE built two prototype engines, which can be seen outside the Experimental Breeder Reactor I in Arco, Idaho.
A large, 350-foot (106.7 meter-) wide hangar was built at Test Area North, part of the National Reactor Testing Station (now part of the Idaho National Laboratory), Monteview, Idaho to house the X-6 project, but the project was cancelled before the planned 15000-foot (4572m) runway was built. The length was necessitated by the expected weight of the nuclear-powered aircraft. … In the 1960s, the Soviet Union‘s Tupolev design bureau conducted a similar experiment using a Tupolev Tu-119, which was a Tu-95 bomber modified to carry an operational reactor.
What about shielding? From Aviation-History:
After establishing the parameters for the power plant and the transfer mechanism, engineers commenced work on the shielding for the crew and aircraft avionic systems. Initial plans called for the shielding of the reactor by massive layers of cadmium, paraffin wax, beryllium oxide, and steel. The idea behind this setting was that the more protection the reactor have, the less shielding the crew cabin would require. Technically, this was a sound approach, but in a rapidly functioning environment such as an aircraft setting, this shielding proved to be ineffective. For this reason it was decided to implement what is known as Shadow Shielding Concept. In shadow shielding, the layers of protection would be equally divided between the reactor and the crew cabin. Shadow Shielding would also provide a more robust protection for the aircraft’s avionics systems. An added plus from the implementation of this system was the reduction in the weight of the aircraft due to the distribution of the shield.
Having tackled the reactor, transfer mechanism, and shielding problems, the program moved it to the aircraft design stage. By late 1951, the program was heavily involved in the acquisition of a test-bed type aircraft for the initial trials of the configuration. The only proven airframe large enough to carry the massive reactor and Heat Transfer system was the Convair’s B-36 Peacekeeper Bomber. The Peacemaker started to enter front line service with the U.S. Air Force in late 1948 and at the time of the nuclear powered program, was the Strategic Air Command (SAC) main nuclear deterrent platform. The B-36 was indeed massive. The dimensions are impressive even today. A wingspan of 230 ft, a length of 162 ft 1in, high of 46 ft 8in, and a wind area of 4,772sq ft. This bomber maximum take-off weight was an amazing 410,000 lbs—which is why the program managers selected the B-36. A service ceiling of 39,900 ft and a climb rate of 2,220 ft per minute were also pluses in the selection process. Once the testing aircraft had been identified, the next phase would commence at once—the conversion of the B-36 into an experimental aircraft. The main modification made to the original B-36 airframe was on the nose cone section. The original crew and avionics cabin was replaced by a massive 11 ton structure lined with lead, and rubber. Water tanks were also placed in the aft section of the frame to absorb any escaping radiation. …
The NB-36 now had four GE J47 nuclear converted piston engines generating 3,800 hp augmented by four 23.13 kn turbojets generating 5,200 lbs of thrust. Each of the engines utilized the Direct-Cycle Configuration for power conversion. The NB-36 was designed from the beginning, to be propelled to the air with a conventional chemical mixture, and then the crew would switch on the reactor after achieving the necessary heat requirements on its core. On landing approaches, the aircraft would switch back to chemical mixture. This procedure was implemented in order to minimize the possibility of a major radiation leak in case of a crash landing. – ah
How small and safe could we make a nuclear reactor?
Toshiba has designs for a micro nuclear reactor that generates 200 kw for 40 years
The new reactor, which is only 20 feet by 6 feet, could change everything for small remote communities, small businesses or even a group of neighbors who are fed up with the power companies and want more control over their energy needs.
The 200 kilowatt Toshiba designed reactor is engineered to be fail-safe and totally automatic and will not overheat. Unlike traditional nuclear reactors the new micro reactor uses no control rods to initiate the reaction. The new revolutionary technology uses reservoirs of liquid lithium-6, an isotope that is effective at absorbing neutrons. The Lithium-6 reservoirs are connected to a vertical tube that fits into the reactor core. The whole whole process is self sustaining and can last for up to 40 years, producing electricity for only 5 cents per kilowatt hour, about half the cost of grid energy. It has dimensions of 20 feet by 6 feet. Toshiba expects to install the first reactor in Japan in 2008 and to begin marketing the new system in Europe and America in 2009.
Perfect for all your underground base needs. Is it possible that research continued secretly?