https://en.wikipedia.org/wiki/Convair_B-36_PeacemakerExperiments
NB-36H nuclear reactor testbed
GRB-36 carrying YRF-84F modified for FICON test
The B-36 was employed in a variety of aeronautical experiments throughout its service life. Its immense size, range, and payload capacity lent itself to use in research and development programs. These included nuclear propulsion studies, and "parasite" programs in which the B-36 carried smaller interceptors or reconnaissance aircraft.[48]
In May 1946, the Air Force began the Nuclear Energy for the Propulsion of Aircraft project, which was followed in May 1951 by the Aircraft Nuclear Propulsion (ANP) program. The ANP program used modified B-36s to study shielding requirements for an airborne reactor to determine whether a nuclear-powered aircraft was feasible.[49] Convair modified two B-36s under the MX-1589 project. The Nuclear Test Aircraft was a B-36H-20-CF (serial number 51-5712) that had been damaged in a tornado at Carswell AFB on 1 September 1952. This aircraft, designated the XB-36H (and later NB-36H), was modified to carry a 1 MW, air-cooled nuclear reactor in the aft bomb bay, with a four-ton lead disc shield installed in the middle of the aircraft between the reactor and the cockpit. A number of large air intake and exhaust holes were installed in the sides and bottom of the aircraft's rear fuselage to cool the reactor in flight.[50] On the ground, a crane would be used to remove the 35,000-pound (16,000 kg) reactor from the aircraft. To protect the crew, the highly modified cockpit was encased in lead and rubber, with a 1-foot-thick (30 cm) leaded glass windshield.[50] The reactor was operational, but did not power the aircraft; its sole purpose was to investigate the effect of radiation on aircraft systems. Between 1955 and 1957, the NB-36H completed 47 test flights and 215 hours of flight time, during 89 of which the reactor was critical.[citation needed]
Other experiments involved providing the B-36 with its own fighter defense in the form of parasite aircraft carried partially or wholly in a bomb bay. One parasite aircraft was the diminutive McDonnell XF-85 Goblin, which docked using a trapeze system. The concept was tested successfully using a B-29 carrier, but docking proved difficult even for experienced test pilots. Moreover, the XF-85 was seen as no match for contemporary foreign powers' newly developed interceptor aircraft in development and in service; consequently, the project was cancelled.[51]
More successful was the FICON project, involving a modified B-36 (called a GRB-36D "mothership") and the RF-84K, a fighter modified for reconnaissance, in a bomb bay. The GRB-36D would ferry the RF-84K to the vicinity of the objective, whereupon the RF-84K would disconnect and begin its mission. Ten GRB-36Ds and 25 RF-84Ks were built and had limited service in 1955–1956.[citation needed]
Projects Tip Tow and Tom-Tom involved docking F-84s to the wingtips of B-29s and B-36s. The hope was that the increased aspect ratio of the combined aircraft would result in a greater range. Project Tip Tow was cancelled when an EF-84D and a specially modified test EB-29A crashed, killing everyone on both aircraft. This accident was attributed to the EF-84D flipping over onto the wing of the EB-29A. Project Tom-Tom, involving RF-84Fs and a GRB-36D from the FICON project (redesignated JRB-36F), continued for a few months after this crash, but was also cancelled due to the violent turbulence induced by the wingtip vortices of the B-36.[52]