Boron mining and Pentaborane (B5H9) synthesis

Pentaborane is an ideal fuel for hypersonic ramjet missiles, afterburning turbojets and conventional rocket engines with dioxygen diflouride as an oxidizer. Despite pentaborane’s outstanding energy density and impulse, turbopumps must be designed to cope with boron oxide formation. Pochari Technologies is actively researching special borane fueled rocket engine turbopumps. Pentaborane can be easily synthesized from diborane and hydrogen via pyrolysis. Typical conditions are 250 C° and a 1:5 diborane/hydrogen ratio. The cost of boron oxide is only $5/kg, reserves are estimated at 1 billion tons. Primary applications will be scramjets and ramjets for the coming hypersonic missile age. Pentaborane, being pyrophoric, gives it an immensely wider flammability range than kerosene, making it highly attractive for high altitude air vehicles.

“The fuel injectors were maintained relatively free from deposits by the atomizing air supplied to the orifice. When the air supply to an individual injector failed, deposits were formed as shown on the injector to the left of bottom center.
The deposits on the afterburner and diffuser walls, the totalpressure rake at the exhaust-nozzle inlet, and the exhaust nozzle are shown in figure 4(b). This photograph, taken immediately after the test, shows the deposits before hydrolysis from atmospheric moisture
occurred. The deposits on the afterburner and diffuser walls consisted
of a thin transparent coat of glass.
The relatively minor boron oxide deposits shown in figure 4 presented no particular obstacle to the use of pentaborane in the afterburner configuration investigated”

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