Rockets using liquid propellants power most spacecraft and some launch vehicles. The liquid propellants currently use dinitrogen tetroxide (N2O4) as an oxidizer, and fuel mixtures containing hydrazine (N2H4), monomethyl hydrazine (MMH), and unsymmetrical dimethyl hydrazine (UDMH). For convenience, N2H4, HDH, MMH, UDMH, Aerozine-50, and N2O4 together are referred to as “hypergols” because the N2O4 oxidizer ignites spontaneously with any of the hydrazine fuels upon contact without the necessity of an ignition source,
At Vandenberg Air Force Base (VAFB) and at Cape Canaveral Air Force Station and Kennedy Space Center, waste N2O4 vapors and waste hydrazine fuel vapors in nitrogen or helium streams are removed at separate facilities with a wet chemical scrubber. The N2O4 scrubbers are typically better than 90 percent efficient, and hydrazine fuel scrubbers are essentially 100 percent efficient. The principal drawback of these scrubbers is that they produce toxic waste scrubbing liquors that must be sent off-site for disposal.
The Air Force Research Laboratory funded CHA Corporation’s development and testing of a prototype microwave system to decompose hypergol vapors in a nitrogen gas stream. The microwave process does not use water, mitigating the production of a secondary liquid waste. The systems were designed to be automated and do not require continuous operator attention. The prototype was successfully tested in August 2002 at Vandenberg Air Force Base (VAFB). The oxidizer destruction efficiency was 99.90% and the hydrazine fuel destruction efficiency was 99.3%.
The successful demonstration led to funding from VAFB to develop the design and drawings for separate microwave scrubbers to destroy fuel and oxidizer vapors. The detailed engineering design was complete in June 2005 and CHA Corporation was awarded a contract for construction of the scrubbers.
The oxidizer scrubber was installed at VAFB in August 2006 and the microwave fuel scrubber in June 2007. CHA Corporation completed startup tests of these two scrubbers in September 2007. The start-up test results show that the destruction efficiencies of oxidizer and fuel vapors were greater than 99.9%, which were independently verified by the Aerospace Corporation.
In December 2010 the microwave scrubbers were relocated to a new location at VAFB to support Boeing’s space activities. CHA Corporation has been providing maintenance services and other technical support to Boeing. Boeing is happy with the performance of these two microwave scrubbers. Following picture shows microwave scrubbers at Boeing site.