The numbers are notable – 34 years of testing space shuttle main engines at NASA’s Stennis Space Center near Bay St. Louis, Mississippi, 3,244 individual tests, more than 820,000 seconds (totaling more than nine days) of cumulative hot fire.
The story behind the numbers is unforgettable.
“It is hard to describe the full impact of the space shuttle main engine test campaign on NASA Stennis,” Center Director John Bailey said. “It is hundreds of stories, affecting all areas of center life, within one great story of team achievement and accomplishment.”
NASA Stennis tested space shuttle main engines from May 19, 1975, to July 29, 2009. The testing made history, enabling 135 shuttle missions and notable space milestones, like deployment of the Hubble Space Telescope and construction of the International Space Station.
The testing also:
- Established NASA Stennis as the center of excellence for large propulsion testing.
- Broadened and deepened the expertise of the NASA Stennis test team.
- Demonstrated and expanded the propulsion test capabilities of NASA Stennis.
- Ensured the future of the Mississippi site.
NASA Stennis was not the immediate choice to test space shuttle main engines. Two other sites also sought the assignment – NASA’s Marshall Flight Center in Alabama and Edwards Air Force Base in California. However, following presentations and evaluations, NASA announced March 1, 1971, that the test campaign would take place in south Mississippi.
“(NASA Stennis) was now assured of a future in propulsion testing for decades,” summarized Way Station to Space, a history of the center’s first decades.
Testing did not begin immediately. First, NASA Stennis had to complete an ambitious project to convert stands built the previous decade for rocket stage testing to facilities supporting single-engine hot fire.
Propellant run tanks were installed and calibrated. A system was fashioned to measure and verify engine thrust. A gimbaling capability was developed on the Fred Haise Test Stand to allow operators to move engines as they must pivot in flight to control rocket trajectory. Likewise, engineers designed a diffuser capability for the A-2 Test Stand to allow operators to test at simulated altitudes up to 60,000 feet.
NASA Stennis teams also had to learn how to handle cryogenic propellants in a new way. For Apollo testing, propellants were loaded into stage tanks to support hot fires. For space shuttle, propellants had to be provided by the stand to the engine. New stand run tanks were not large enough to support a full-duration (500 seconds) hot fire, so teams had to provide real-time transfer of propellants from barges, to the run tanks, to the engine.
The process required careful engineering and calibration. “There was a lot to learn to manage real-time operations,” said Maury Vander, chief of NASA Stennis test operations. “Teams had to develop a way to accurately measure propellant levels in the tanks and to control the flow from barges to the tanks and from the tanks to the engine. It is a very precise process.”
The biggest challenge was operation of the engine itself. Not only was it the most sophisticated ever developed, but teams would be testing a full engine from the outset. Typically, individual components are developed and tested prior to assembling a full engine. Shuttle testing began on full-scale engines, although several initial tests did feature a trimmed down thrust chamber assembly.
The initial test on May 19, 1975, provided an evaluation of team and engine. The so-called “burp” test did not feature full ignition, but it set the stage for moving forward.
“The first test was a monstrous milestone,” Vander said. “Teams had to overcome all sorts of challenges, and I can only imagine what it must have felt like to go from a mostly theoretical engine to seeing it almost light. It is the kind of moment engineers love – fruits-of-all-your-hard-labor moment.”
NASA Stennis teams conducted another five tests in quick succession. On June 23/24, with a complete engine thrust chamber assembly in place, teams achieved full ignition. By year’s end, teams had conducted 27 tests. In the next five years, they recorded more than 100 annual hot fires, a challenging pace. By the close of 1980, NASA Stennis had accumulated over 28 hours of hot fire.
The learning curve remained steep as teams developed a defined engine start, power up, power down, and shutdown sequences. They also identified anomalies and experienced various engine failures.
“Each test is a semi-controlled explosion,” Vander said. “And every test is like a work of art because of all that goes on behind the scenes to make it happen, and no two tests are exactly the same. There were a lot of knowledge and lessons learned that we continue to build on today.”
Teams took a giant step forward in 1978 to 1981 with testing of the Main Propulsion Test Article, which involved installing three engines (configured as during an actual launch), with a space shuttle external tank and a mock orbiter, on the B-2 side of the Thad Cochran Test Stand.
Teams conducted 18 tests of the article, proving conclusively that the shuttle configuration would fly as needed. On April 12, 1981, shuttle Columbia launched on the maiden STS-1 mission of the new era. Unlike previous vehicles, this one had no uncrewed test flight. The first launch of shuttle carried astronauts John Young and Bob Crippen.
“The effort that you contributed made it possible for us to sit back and ride,” Crippen told NASA Stennis employees during a post-test visit to the site. “We couldn’t even make it look hard.”
Testing proceeded steadily for the next 28 years. Engine anomalies, upgrades, system changes – all were tested at NASA Stennis. Limits of the engine were tested and proven. Site teams gained tremendous testing experience and expertise. NASA Stennis personnel became experts in handling cryogenics.
Following the loss of shuttles Challenger and Columbia, NASA Stennis teams completed rigorous test campaigns to ensure future mission safety. The space shuttle main engine arguably became the most tested, and best understood, large rocket engine in the world – and NASA Stennis teams were among those at the forefront of knowledge.
NASA recognized the effort of the NASA Stennis team, establishing the site as the center of excellence for large propulsion test work. In the meanwhile, NASA Stennis moved to solidify its future, growing as a federal city, home to more than 50 resident agencies, organizations, and companies.
Shuttle testing opened the door for the variety of commercial aerospace test projects the site now supports. It also established and solidified the test team’s unique capabilities and gave all of Mississippi a sense of prideful ownership in the Space Shuttle Program – and its defining missions.
No one can say what would have happened to NASA Stennis without the space shuttle main engine test campaign. However, everything NASA Stennis now is rests squarely on the record and work of that history-making campaign.
“Everyone knows NASA Stennis as the site that tested the Apollo rockets that took humans to the Moon – but space shuttle main engine testing really built this site,” said Joe Schuyler, director of NASA Stennis engineering and test operations. “We are what we are because of that test campaign – and all that we become is built on that foundation.”
