Project pluto
Project History
Back in the mid 1950's, nuclear powered cruise missiles were being studied and in 1957, development was initiated as Project Pluto. The reactor for the missile was to be developed by the Lawrence Radiation Laboratory, with the ramjet being built by Marquadt. Ling-Temco-Vought was awarded the contract to develop the airframe for the missile itself, which was known as SLAM (Supersonic Low-Altitude Missile).
The mission profile called for SLAM to be launched from hardened silos, propelled by solid rocket boosters up to ramjet ignition speed. SLAM would then cruise at high altitude (35,000ft/10,700m) at Mach 4, where it's range was estimated to be more than 10,000km. This meant the missile could 'loiter' at a fail safe point until it was ordered to either continue to it's target or abort its mission. Over enemy territory it would descend to low level, using TERCOM (Terrain Contour Matching) to find its way to multiple targets.
It was envisaged that between 16 and 24 thermonuclear weapons would be carried, and ejected one by one as it flew over it's targets. The weapons would be launched on a lofted trajectory from hatches in the top of the missile to allow it a few seconds to escape the blast. The mission profile gave rise to a number of unique features. Flying at low level, the sonic boom of a 25m long aircraft flying at Mach 3 would flatten any unhardened structures, while the exhaust from the unshielded nuclear reactor would leave a trail of radioactive debris. It was estimated that the sound level on the ground could be as high as 150db. Once the weapons were exhausted, the missile itself could be used as a weapon - crashing a 'hot and dirty' reactor onto the ground would leave a very large area uninhabitable for many years. Due to the stresses and temperatures involved in flying at high speeds at low levels, the airframe would have to be extremely robust, earning it the nickname 'Flying Crowbar' from Ted Merkle, the project director. Another engineer said it was a durable "as a bucket of rocks'. The design itself was wingless, with three stabilising fins at the rear and three small all-moving fins at the front. The intake for the ramjet was underneath the body of the missile.
The first flight was due in 1967, but by 1964 the project was in trouble. Intercontinental Ballistic Missiles (ICBMs) were in place which could strike the Soviet Union, and SLAM wasn't expected to be in service before 1970. Also, flight testing proved to be a problem, as it couldn't be tested over land due to the radioactive exhaust, and testing over the sea would mean crashing the missile, complete with several tons of nuclear reactor, into the ocean. Also, the whole venture was getting more and more expensive, and the project was finally cancelled in July 1964.
Reactor Development
Development of the reactor eventually resulted in the testing of a reactor named TORY-IIA in 1961. TORY-IIC, the reactor intended for initial flight tests was tested at full power in 1964, producing 170kN (38,000lbs) of thrust at an estimated speed of Mach 2.8. Operational missiles would have used an improved design called TORY-III. The reactor would have to be a piece of extreme engineering; operating at 1,600 Celsius meant that pneumatic controls would be red hot and exposed to intense radioactivity. Most metals would melt at its operating temperatures so ceramic fuel elements would have to be used. It was calculated that aerodynamic stressed would be 5 times that experienced by the X-15.
The reactor testing was conducted at a custom built, eight square mile facility costing $1.2 million at Jackass Flats in the Nevada Test Site. 6 miles (10km) of roads had to be built, along with the assembly building, control building, assembly and shop buildings. 25 miles of oil well casing was used to store pressurised air need to create the ramjet conditions for ground testing. The lab borrowed huge compressors from the US Navy's submarine base at Groton, Connecticut to supply the air.
Revival
One of the few nations that have bothered reviving this project is the Federation of Dosuun. Development is slow but several redesigned airframes are undergoing testing using conventional engines as all potential replacement reactor designs are still in some stage of assembly.
Reference
Much of this page was taken from Project Pluto
