KSC Contact: Bruce Buckingham

KSC Release No. 28-00

The next Space Shuttle mission will be devoted to the continued growth of the International Space Station. In an indirect way, the mission also will contribute to the growth of citrus trees here on Earth.

A system for converting vapors from the Shuttle’s hypergolic oxidizer into fertilizer was installed at Launch Pad 39A in early March. Already in use, it received its first major test during pre-launch hypergolic loading operations for STS-101.

“It’s good to see something you’ve been a part of go to completion,” said Clyde Parrish, the NASA/KSC engineer who devised the system. “We are happy to see this all come together and operate like we expected and as the tests indicated it would.”

The Space Shuttle uses nitrogen tetroxide as the oxidizer for the hypergolic propellant in its on-orbit reaction control system. When the oxidizer is transferred from ground storage tanks into the Shuttle storage tanks – and during maintenance operations – some nitrogen tetroxide vapor develops as a by-product. Kennedy Space Center has used a “scrubber” system since the 1980s to capture the toxic vapor, preventing it from escaping into the atmosphere.

The Improved Nitrogen Tetroxide Scrubber system traps the vapor in water and then uses hydrogen peroxide to produce nitric acid. The addition of another compound, potassium hydroxide, converts the nitric acid into potassium nitrate, a commercial fertilizer.

Plans call for the resulting fertilizer to be used on the orange groves that KSC leases to outside companies. Parrish said the fertilizer will replace 10 percent of the amount purchased at KSC, resulting in an annual savings of approximately $20,000. Equally important, the conversion process eliminates KSC’s second largest source of toxic waste and saves about $60,000 on disposal costs.

The installation of the scrubber follows a five-year process of development and production. The concept arose from consulting work Parrish did in the 1970s involving chemical separations. NASA/KSC engineer Dale Lueck contributed plans for a hydrogen peroxide controller and Dynacs Engineering Co. produced the scrubber system under the direction of the NASA Instrumentation Lab. It was installed by United Space Alliance.

Parrish said the system automatically transfers the fertilizer produced during loading or maintenance operations into a trailer stationed nearby. Once the trailer has been filled, the fertilizer will be taken to its destination.

Parrish estimated that preparations for STS-101 will produce enough fertilizer to fill two 1000-gallon trailers.

“The system is designed so that when you start the scrubbing operations it automatically comes on and controls the process,” Parrish said. “Its operation is essentially transparent to the workers. It automatically offloads the scrubber sump to the trailers. No one needs to worry about it until the receiving trailer is full.”

Hypergolic propellants – those that generate power through chemical reactions – produce emissions not only in flight preparations at the pad but also in maintenance operations at other locations, including the Orbiter Processing Facility and the Hypergolic Maintenance Facility in KSC’s industrial area. Scrubbers are in place wherever hypergolic propellants are used. Once the new control system at the pad proves successful, KSC may develop and install similar devices on its other scrubbers. The new system reduces emissions to 10 percent or less of the previous levels.

The innovation also has commercial potential. Parrish noted that many industries – including power plants and metal finishing operations – use processes that produce oxides of nitrogen. Should KSC license the technology to businesses, the resulting royalties would make the system even more financially beneficial.