Path: utzoo!utgpu!watmath!att!cbnews!military From: thomasw@doyle.cs.concordia.ca Newsgroups: sci.military Subject: Re: Nuclear Aircraft Message-ID: <11489@cbnews.ATT.COM> Date: 17 Nov 89 06:09:57 GMT Sender: military@cbnews.ATT.COM Lines: 140 Approved: military@att.att.com From: thomasw@doyle.cs.concordia.ca The following is from Chapter 10: The Convair X-6 of _The X-Planes_ (X-1 to X-31) by Jay Miller, greatly abbreviated and paraphrased and therefore, I hope, acceptable for posting. The Convair X-6 --------------- Manufacturer: Convair Division of General Dynamics (X-6 airframe, based on B-36) Aircraft Gas Turbine Division of General Electric (P-1 nuclear powerplant) In 1951, GE was awarded an Air Force contract to develop a nuclear turbojet engine and an Atomic Energy Commission contract to develop a nuclear reactor to be used for aircraft propulsion. The resulting powerplant, named the P-1, was an air-cooled nuclear reactor using metallic fuel elements and water as a moderator and coolant. Also in 1951, Convair was awarded an Air Force contract to modify two B-36H airframes (redesignated the X-6) to carry the P-1 powerplant, and a third B-36H to be used for shield testing. The aircraft were to be used to evaluate the practicability of nuclear propulsion systems, including reactor shielding and radiation effects on crew and electrical systems. The X-6 never got past the design stage, but the shield test aircraft was built and subsequently flown as the Nuclear Test Aircraft (NTA), designated as NB-36H (AF serial number 51-5712). History: First AF interest in nuclear propulsion in 1944 led to the establishment of the Nuclear Energy for Propulsion of Aircraft (NEPA) project at Fairchild Airplane and Engine Company in 1946, which was later joined by the AEC and the Navy. NEPA was dissolved in 1951 and replaced by the (expanded) Aircraft Nuclear Propulsion (ANP) program; ANP was permanently cancelled in 1961. A study in 1948 (Lexington Report) suggested that nuclear propulsion was feasible, but that it would require a 15-year, 1-billion-dollar effort. AEC then asked DoD to establish the military need for nuclear powered aircraft before embarking on such a large effort; as a consequence of the political situation, a long-range strategic bomber was deemed a necessity and the Air Force was given the go-ahead. The original goal was a extreme-range supersonic bomber, later scaled down to the X-6 subsonic testbed. Several reactor designs (using liquid-metal, air, and high-pressure water cooling) were competing with each other, with the air-cooled design the eventual winner. Design difficulties (no material could withstand the proposed temperature of 2500 F) led to a lowering of the reactor's operating temperature to 1800 degrees F and thus to a lowering of the reactor's power output. This, and concerns about the slow spool-up/down times of the reactor, led to the inclusion, in the design, of conventional jet engines to serve as auxiliary powerplants and to provide additional thrust during take-off. The design thus called for four turbo-jet engines to be connected to the reactor, which would produce 26,000 lbs thrust at 15,000 feet using reactor heat, but which would retain their combustion chambers for burning chemical fuels; this would propel the aircraft to speeds from 300 to 390 mph. The propulsion system was to weigh around 165,000 lbs (10000 lbs reactor, 60000 lbs reactor shielding, 37000 lbs crew shielding, 18000 lbs engine, 40000 lbs piping and accessories). There followed a series of technical problems (low power output, high shielding weight, piping problems), design changes (different airframes, different engines, different reactor/propulsion designs), changes in program direction (finally to include manned aircraft, nuclear rockets, and nuclear ramjets), and funding difficulties, which by 1961 resulted in the cancellation of the program after expenditures of about 470 million dollars. The only flying hardware that came out of the program was the above-mentioned NB-36H Nuclear Test Aircraft, which made its first flight in September, 1955. The aircraft had a totally redesigned nose section to accomodate the 12-ton shielded crew capsule and a redesigned fuselage to hold nine water-filled shield tanks and test instrumentation. The aircraft carried a 35000 lbs, one MW reactor mounted in the aft bomb bay, which could be removed after each flight for examination and ground testing (and continued cooling). The NB-36H completed a total of 47 flights between September 1955 and March 1957, examining "radiation shielding methods and materials, radiation effects on aircraft materials and components, and nuclear ground and flight operations." The reactor was never used to power any of the aircraft's engines or systems, even though it was made critical and power was generated during flight. (The last sentence seems to contradict itself, but that is what it says in the book). >From the pictures in the book and their legends, I could glean the following: - the aircraft had two fairly big air intakes added on the sides of its aft fuselage (about halfway between the wing and the tail), complemented by two large exhausts on the top of the fuselage - the crew capsule could only be entered through a special hatch at the top, which due to its weight could only be opened mechanically (forget about bailing out) - the cockpit windows were fairly small and consisted of a 9-11 inch thick layer of water; visibility was very limited - the reactor was stored in a special pit in the runway at Convair's Fort Worth plant which was covered by track-mounted lead doors. From there it could be installed in the NB-36H bomb bay by positioning the aircraft above the pit and winching the reactor into the bomb bay Just because some previous posters mentioned the prohibitive weight of reactor shielding, I want to add the following data from the design of the X-6: Gross weight: 360,000 lbs; empty weight: 225,000 lbs. Reactor shielding: - main forward shield: 103 foot, 12 foot diameter tank of pressurized water - forward gamma shield: 80-inch diameter, 4 inch thick circular lead shield - side shield: 2.5-inch thick layer of polyethylene plastic, double-walled fuselage Crew shielding (note that this is ~60 foot forward of the reactor!): - cylindrical, 14 foot long and 6.75 foot diameter, with small cutout for 12 inch thick water window in front - .25 inch lead and 9 inch plastic lining in front - 2.5 inch lead and 21.5 inch plastic in rear (ie. towards reactor) - 0.25 Roentgen hourly charge into crew compartment One thing I wonder is how much radiation escaped sideways out of the fuselage (the side and aft shielding is pretty flimsy compared to the massive frontal shielding) and how much radio-active exhaust was produced, but it doesn't give that data in the book. According to the description and the drawings of the reactor in the book, the air was going straight through the reactor core, heated up by the hot fuel rods. Sorry if this is a bit long, I hope it's of interest. Thomas Thomas Wieland Email: thomasw@jupiter.cs.concordia.ca Dept. of Computer Science or: thomasw@concour.cs.concordia.ca Concordia University Montreal, PQ Canada Phone: (514) 848-3039 [PS: Bill, regarding the German pocket battleships (in 50 Years ago), the correct use of the word is: one "Panzerschiff", two "Panzerschiffe" -- just nit-picking, I really enjoy your series. ]