Zip Fuel - History

History

Several studies were made into boronated fuels over the years, starting with the U.S. Army's rocket-related Project HERMES in the late 1940s, the U.S. Navy Bureau of Aeronautics's Project ZIP in 1952, and the U.S. Air Force's Project HEF (High Energy Fuels) in 1955. For much of the 1950s, zip fuels were considered to be the "next big thing" and considerable amounts of money were poured into these projects in an effort to bring them into service. The Navy's name stuck, and all of the boronated fuels became known as "zip fuels", although the Air Force's naming for the fuels themselves became common.

The main thrust of the Air Force's program was based on HEF-3, which seemed to be the most likely candidate for quick introduction. HEF became part of the WS-110 efforts to build a new long-range bomber to replace the B-52 Stratofortress with a design able to dash at speeds up to Mach 2. The initial designs from Boeing and North American Aviation (NAA) both used conventional fuels for takeoff and cruise, switching to HEF during the high-speed dash, burning it only in their afterburner sections. This avoided both of the main problems with HEF; by burning it only in the afterburners the problem with buildup on the turbine was eliminated, and since the afterburners were only used for takeoff and high-speed flight, the problems with the toxic exhaust were greatly reduced.

When the initial designs proved to be too expensive to justify their relatively small performance improvement, both returned to the drawing board and came up with new designs that flew at supersonic speeds for most of a combat mission. These designs were based around new engines designed for sustained high-speed flight, with the NAA B-70 Valkyrie and General Electric J93 progressing to the prototype stage. In these cases the afterburners were used for a longer period, maximizing the benefits of HEF. There were plans to introduce a later version of the J93 that would burn HEF-4 throughout. Meanwhile there were also studies on using HEF-3 in the BOMARC ramjets, as well as studies about carrying it on the U.S. Navy's aircraft carrier fleet to power future aircraft, but these programs both died out.

As the problems were proving intractable, the Air Force canceled their program in 1959, and interest in zip basically disappeared. By this point the only design still considering using HEF was the XB-70 and its J93. NAA and General Electric responded by redesigning the engine to run on a new higher-density form of jet fuel, JP-6, and filling one of the two bomb bays with a new fuel tank. In doing so the range was dramatically reduced from about 7,700 nautical miles (14,260 km) to 5,500 nautical miles (10,190 km). This reduced the selection of targets that could be attacked from the United States and required in-flight refueling for every mission profile, one more problem that led to the project's eventual re-direction as a purely experimental aircraft.

It is estimated that the U.S. spent about $1 billion on the program, in 2001 inflation-adjusted dollars. At least five HEF production plants were built in the U.S., and two workers were killed in an explosion that destroyed one plant in New York. Most of the program was classified Top Secret while being carried out, but nevertheless it was widely covered both in the trade press and civilian newspapers. Both the U.S. and Soviet Union independently declassified their research in 1964.

One potentially lasting relic of the HEF program is an abandoned dirt airfield outside Boron, California. Marked on USGS topographical maps as "Air Force Plant #72", nothing but the airstrip and a water tank were even built on the site. It is speculated that this would have been a factory for HEF fuel, using the large borax deposits nearby (giving the town its name), where it could be easily shipped to Edwards Air Force Base.