The pace of Space Launch System (SLS) development engine test firing is in full swing at NASA’s Stennis Space Center near Bay St. Louis, Mississippi, as NASA and Aerojet Rocketdyne completed their longest SLS main engine test fire to date on June 25. Secured tightly on the historic A-1 test stand, SLS development engine #0525 came roaring to life for 650 seconds, a full 150 seconds longer than its previous test fire on June 11, sending a thunderous roar across Stennis as the engine successfully carried out its fourth test fire for the colossal 320-foot-tall rocket which will launch astronauts over the coming decades to destinations farther from home than any human has ever been.
“While we are using proven space shuttle hardware with these engines, SLS will have different performance requirements,” said Steve Wofford, manager of the SLS Liquid Engines Office at NASA’s Marshall Space Flight Center in Huntsville, Ala. The Marshall Center manages the SLS Program for the agency. “That’s why we are testing them again. This is a whole new ballgame — we need way more power for these engines to be able to go farther than ever before when it comes to human exploration. And we believe the modifications we’ve made to these engines can do just that.”
Yesterday’s fourth RS-25 engine test fire went off without issue—something that has come to be expected of the RS-25 engine, which formerly powered NASA’s now-retired space shuttle fleet uphill on 135 missions. The RS-25 was the first reusable rocket engine in history, as well as being one of the most tested large rocket engines ever made, having conducted more than 3,000 starts and over one million seconds (nearly 280 hours) of total ground test and flight firing time over the course of NASA’s 30-year space shuttle program.
The engines proved their worth time and time again, but the RS-25 now requires several modifications to meet the giant SLS rocket’s enormous thrust requirements.
Yesterday’s test fire will provide engineers with critical data on the engine’s new state-of-the-art controller unit—the “brain” of the engine, which allows communication between the vehicle and the engine itself, relaying commands to the engine and transmitting data back to the vehicle. The new controller also provides closed-loop management of the engine by regulating the thrust and fuel mixture ratio while monitoring the engine’s health and status, thanks to updated hardware and software configured to operate with the new SLS avionics architecture.
This fourth test firing expands on the performance objectives of the first two firings, which took place in January and May this year, and will help engineers to better understand the upgraded engine under a range of operating conditions.
“We’ve made modifications to the RS-25 to meet SLS specifications and will analyze and test a variety of conditions during the hot fire series,” said Wofford after the first test fire earlier this year. “The engines for SLS will encounter colder liquid oxygen temperatures than shuttle; greater inlet pressure due to the taller core stage liquid oxygen tank and higher vehicle acceleration; and more nozzle heating due to the four-engine configuration and their position in-plane with the SLS booster exhaust nozzles.”
For shuttle flights the engines pushed 491,000 pounds vacuum thrust during launch—each—and shuttle required three to fly, but for SLS the power level was increased to 512,000 pounds vacuum thrust per engine, and the SLS will require four to help launch the massive rocket and its payloads with a 70-metric-ton (77-ton) lift capacity that the initial SLS configuration promises.
The pace for SLS engine testing at Stennis will remain steady this summer, with three more scheduled for July and the final test fire for this first test series scheduled for Aug. 13.
NASA is inviting social media gurus to the August test fire; anyone interested in applying for that “NASA Social” can do so HERE.
After the first test fire on Jan. 9, upgrades were needed on the A-1 test stand’s high pressure industrial water system, which provides cool water for the test stand during a hot-fire engine run. Engine 0525 will carry out a total of seven test fires in this first series of tests and will fire for a grand total of 3,500 seconds, followed by another 10 test fires with another development engine, which will be put through its paces for a grand total of 4,500 seconds.
To put the power of the Aerojet Rocketdyne-built RS-25 engines into perspective, consider this:
- The fuel turbine on the RS-25’s high-pressure fuel turbopump is so powerful that if it were spinning an electrical generator instead of a pump, it could power 11 locomotives; 1,315 Toyota Prius cars; 1,231,519 iPads; lighting for 430 Major League baseball stadiums; or 9,844 miles of residential street lights—all the street lights in Chicago, Los Angeles, or New York City.
- Pressure within the RS-25 is equivalent to the pressure a submarine experiences three miles beneath the ocean.
- The four RS-25 engines on the SLS launch vehicle gobble propellant at the rate of 1,500 gallons per second. That’s enough to drain an average family-sized swimming pool in 60 seconds.
WATCH! SLS RS-25 Development Engine #0525 Test Fire #4 June 25, 2015
Four previously-flown RS-25 engines will be attached to the first SLS core stage, which will be manufactured at Michoud Assembly Facility in New Orleans, and test fired together atop the B-2 test stand at Stennis as a stage before being approved for the first SLS launch, planned for late 2018.
NASA currently has 16 RS-25 engines in their SLS inventory—14 of which are veterans of numerous space shuttle missions. Aerojet Rocketdyne just recently finished assembly of the 16th engine (engine 2063), one of the space agency’s two “rookie” RS-25s. It will be one of four RS-25 engines that will be employed to power the SLS Exploration Mission-2 (EM-2), the second SLS launch currently targeted for the year 2021.
“There is nothing in the world that compares to this engine,” said Jim Paulsen, vice president of Program Execution Advanced Space & Launch Programs Aerojet Rocketdyne. “It is great that we are able to adapt this advanced engine for what will be the world’s most powerful rocket to usher in a new space age.”
The SLS program also kicked off its Critical Design Review (CDR) in May at NASA’s Marshall Space Flight Center in Huntsville, Ala., which demonstrates that the SLS design meets all system requirements with acceptable risk and accomplishes that within cost and schedule constraints. The CDR proves that the rocket should continue with full-scale production, assembly, integration, and testing, and that the program is ready to begin the next major review covering design certification. The SLS CDR is expected to be completed by late-July.
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