From Missiles to Medicine:
The development of boron hydrides
March 2001

Dave Schubert, PhD

Boron hydrides, also known as boranes, are the exotic branch of the boron family. Unlike their more familiar and stable cousins - borax and boric acid among them - some boranes are so reactive they catch fire when exposed to air, burning with boron's signature green flame. The chemistry of this unique family of boron compounds was first explored in the early part of the 20th century. So difficult were these materials to handle safely that scientists had to invent completely new laboratory methods.

One of boron hydrides' first claims to fame was as a potential means to produce weapons. Research sponsored by the U.S. National Defense Research Committee in the 1940s studied uranium borohydride and related compounds for ways to separate uranium isotopes in the race to produce the first atomic bomb. But the real contest to unlock the secrets of boron hydrides began after World War II ended.

In the early days of the Cold War Arms Race, aircraft and missiles could not fly far enough or fast enough to deliver weapons to their intended targets on distant continents. This military need gave birth to intense effort in both the U.S. and the U.S.S.R. to produce more powerful jet and rocket fuels. Attention naturally focused on the high-energy boron hydrides.

Massive, top secret government programs were set in motion to manufacture large quantities of boron-based fuels, and to develop new and better ones. The U.S. Army launched Project HERMES in the late '40s; in 1952 the U.S. Navy Bureau of Aeronautics started Project ZIP; and, in 1956 the U.S. Air Force sponsored Project HEF (High Energy Fuels).

Throughout the 1950s, these programs pushed forward at a tremendous pace, mobilizing many gifted scientists and engineers, all working under a veil of secrecy. At least five boron fuels production plants were built in the U.S., requiring heroic efforts by those involved in handling these dangerous materials. Many problems were tackled along the way, but not without exacting a price, both in terms of money spent and lives lost - two workers were killed in an explosion that destroyed one plant in New York, and tragic fatalities occurred at other sites as well.

News reports of the 1950s conveyed electrifying rumors about boron fuels. Many at the time believed that the Russians used boron fuels to launch Sputnik in 1957. U.S. Borax made news as a material supplier in the race to make full-scale boron fuels a reality. And the U.S. government launched a major project in 1955 to build a boron-fuel-powered long-range strategic bomber called the Valkyrie XB-70A.

Two of these magnificent jet aircraft were eventually built. One XB-70A was destroyed in a mid-air collision with a fighter jet over California's Mojave Desert - near Borax's current mining operation - but the remaining bomber is on display at the Wright Patterson Air Force Base in Ohio, U.S. Although they never flew solely on boron fuel, their construction led to technological advancements in the design of high speed aircraft. In fact, the XB-70A served as a model for the design of the Concorde supersonic jet.

Ultimately, the era of boron fuels came to a close. By the end of the 1950s, new generations of jet engines and new fuels involving liquid hydrogen and hydrazine made boron fuels obsolete. Technical problems with boron fuels - including byproducts that decreased engine function and high fuel consumption rates - had proved too hard to overcome.

In 1959, the U.S. military cancelled the boron fuels program, having invested the equivalent in modern currency rates of more than one billion dollars. In wasn't until 1964 when both the U.S. and the U.S.S.R. almost simultaneously declassified documents about their boron fuels projects that the public could finally see the monumental scale of these efforts.

Looking back, the history of boron fuels projects might seem like an utter waste - but the story doesn't end there. These Herculean efforts produced myriad discoveries that are still finding applications today. For instance, boron hydride research led to the discovery of a new chemical reaction known as hydroboration, which in turn made important pharmaceutical applications possible.

Chemists also discovered a new class of compounds called carboranes. These hybrid molecules, containing both boron and carbon in their cage structures, have remarkable properties. Unlike the simpler boron hydrides, the larger cage boranes and carboranes turned out to be much safer to handle. Not only are they stable in air and can be heated to high temperatures without decomposing, but they also resist attack by strong acids. This discovery provided a basis for one of the fastest growing areas of inorganic chemistry over the past four decades.

Current work on boron hydrides is still led largely by chemists who received their initial training during the military projects of the '40s and '50s, as well as their students. The groundwork laid by these pioneers has led to boron hydride applications in everything from pharmaceuticals to automobile safety equipment, and paper production to water treatment.

Science shapes culture, but the opposite holds true as well. The power of boron hydrides was harnessed for battle when the world was recovering from its greatest modern conflict. Now the race is on to develop boron hydrides' high-tech and medical applications - progress that makes the world a safer place.

For more information, please contact Dave Schubert at (1) 661 287 6074 (United States).