Arnold helps develop method for demilitarization of aging rockets

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Recently, Arnold Engineering Development Center (AEDC) played a role in the environmentally-safe destruction of an aging Army Multiple Launch Rocket System (MLRS) rocket motor in the center's J-6 rocket motor test facility.

El Dorado Engineering (EDE), of Salt Lake City, Utah, came to AEDC with a concept for a rocket disposal method and to take measurements that could be made to validate their approach and design for a suitable disposal facility.

"The purpose of the test was to demonstrate the feasibility of the contained burn concept for the MLRS motor and gather data to better evaluate this approach," Bob Hayes, senior engineer for EDE said.

One of EDE's officers toured AEDC years ago and remembered the center's capabilities.

"As a company we could not be more pleased with the performance of AEDC on this project," Hayes said. "They were helpful and capable in every phase of this job, including facilitating communication and logistics with other branches of the military involved on the project to ensure the test window was met."

Hayes said it was also "This test was necessary to also measure the rocket exhaust gases downstream of any exhaust plume afterburning in order to determine how much air participated in the rocket afterburning, how much exit-plane carbon monoxide was combusted to carbon dioxide and to quantify thermally generated oxides of nitrogen."

The team also investigated the maximum rocket motor case and rocket diffuser wall temperatures through the use of thermal phase change paint. Thermal change paint was applied to the rocket motor and diffuser walls and a comparison was made between pre-and-post-test paint appearances.

James Brooks, Aerospace Testing Alliance project manager for center's J-6 test cell said, "In order to accomplish this task a single MLRS rocket motor was fired at sea level conditions in J-6. Rocket exhaust gas was extracted using two gas sample manifolds in the J-6 exhaust duct and dehumidification cooler."

This was then analyzed for the primary products of combustion carbon monoxide, carbon dioxide and nitric oxide. Emissions data for several species were quantified and this data was fed into the EDE Products of Combustion and Dispersion (PCAD) model to quickly evaluate the amount of air which was entrained into the plume and participated in combustion.

Hayes said, "The test firing demonstrated the successful proof of concept for contained burn for this motor and test emissions data collected showed that the afterburning occurring after the rocket nozzle exit resulted in very complete combustion, so an additional expensive afterburner would not be required for the final system."

According to Hayes, the results will allow the military to evaluate the utility of this approach for disposal of these old motors.

The M270 weapons platform Multiple Launch Rocket System (MLRS) is a rocket artillery system manufactured by Lockheed Martin Missiles and Fire Control. The system is operational in the U.S. Army and 14 countries have fielded or ordered MLRS. It provides an all-weather, indirect, area fire weapon system to strike counter-fire, air defense, armored formations and other high pay-off targets at all depths of the tactical battlefield.

MLRS fires surface-to-surface rockets and the Army Tactical Missile System (ATACMS). Without leaving an armored vehicles cab, troops can fire up to 12 rockets in less than 60 seconds. MLRS has cross-country mobility and a road speed of 65 km per hour.

El Dorado Engineering, Inc. is a 27-year-old small business which specializes in the development of new technologies and the design of equipment for demilitarization. EDE also has expertise in the modeling of plumes from rocket motors, having developed the PCAD model which predicts the combustion products of rocket plumes and downwind concentrations based on input meteorological conditions.

According to Hayes, the PCAD was validated with full-scale space shuttle booster and Pershing missile motors and has been used for permitting of open burning for rocket motor demilitarization as well as launches.