NASA and Redstone Collaborate on Solid Rocket Motor Firing

A subscale solid rocket motor tested in a flight-like vertical orientation fired with 50,000 pounds of thrust and ignited new insights into solid rocket performance.
The hot fire, conducted at the Redstone Test Center’s Test Area 5 on Redstone Arsenal in Huntsville, Ala., is the first vertical test for NASA’s 24-inch-diameter, two-segment solid rocket motor test article. Engineers from NASA’s Marshall Space Flight Center located on Redstone Arsenal led the test effort, which hot fired the 20-foot long test article for 20-seconds, reaching temperatures of 5,000-degrees.

“Our Team Redstone collaboration allowed us to test a subscale booster of this size in a vertical position for the first time,” said Scott Ringel, a Marshall Center engineer and the design lead for the test. “The vertical test position gives us better insight into how solid rocket booster technology performs during ignition, launch and liftoff.”

One of the test objectives is to look for evidence of “slag” — a pool of chemical components that can build up in the bottom of motors. Marshall engineers want to understand the effects of slag on the internal insulation material. Slag is a result of solid rocket propellant combustion, and NASA engineers have studied its effects since the early days of the space shuttle booster flights.
Marshall engineers also will use data collected from the test to study insulation, propellant and nozzle performance, which will improve the modeling techniques used on the design of large boosters.

A team from NASA’s Kennedy Space Center, Fla., worked with Marshall engineers to install samples beneath the motor to test candidate materials for the Space Launch System (SLS) booster aft skirt umbilical, a feed line that delivers gaseous nitrogen to keep temperatures at a determined rate before a launch.

All this data is valuable to NASA’s Engineering and Safety Center (NESC), which is one sponsors of the test. Test analysis will be added the engineering database on boosters to help ensure the safety and mission success for the many launch vehicles across government and commercial rockets powered by solid rocket boosters.

“This test is a low-cost, reliable way not only to reduce any risks associated with boosters, but also to provide our younger engineers with an excellent opportunity to get their hands dirty,” said Ringel. “They are involved in every part of the process — designing, analyzing, building, disassembling the motors and studying the data. You really can’t get better experience as an early-career engineer than learning directly from hardware.”

Previous similar tests were conducted in the horizontal position in Marshall Center’s test area, but there was no capability to test in the vertical position. Now, through a Team Redstone partnership, Marshall engineers can complete a test affordably at the nearby Redstone Test Center. This allows engineers to compare data from the numerous horizontal solid rocket motor firings to new data from the vertical firing.

“We are proud to provide test and evaluation support to our partners at Marshall,” said Chuck Gibbs, director for Redstone Test Center’s Missiles and Sensors Test Directorate. “Tests like this are a good example of the working relationship we have here on Team Redstone, to not only provide support to the warfighter in the field, but to our nation’s space program as well.”

The subscale motor test is a collaborative effort between the Marshall Space Flight Center; The U.S. Army Redstone Test Center; the SLS Program; NASA’s Engineering and Safety Center; Jacobs Technology Inc. of Huntsville; and ATK of Brigham City, Utah.

This kind of testing may be beneficial for future launch vehicles, including NASA’s SLS. Two five-segment solid rocket motors — the world’s largest at 154 feet long and 12 feet in diameter — will be used in the first two 70-metric-ton capability flights of SLS.