NASA Tests Second Entry of New RS-25 Engine Test Series

NASA performed a second RS-25 single engine hot-fire test on April 6, 2021, as part of a new sequence designed to aid in constructing and manufacturing engines for NASA's Space Launch System (SLS) rocket on possible Moon missions.

The space agency performed a full-duration hot fire lasting more than eight minutes (500 seconds) on the A-1 Test Stand at NASA's Stennis Space Center near Bay St. Louis, SciTechDaily said.

It's part of a seven-test series planned to provide Aerojet Rocketdyne, the lead contractor for the SLS engines, useful data as it prepares to start developing new RS-25 engines after the first four SLS flights.

Four RS-25 engines power SLS that fire simultaneously to produce 1.6 million pounds of thrust at launch and 2 million pounds of thrust during ascent. The RS-25 engines for the first four SLS flights have passed certification tests and are modified space shuttle main engines.

What About NASA's RS-25?

Slashgear said that the RS-25 is one of the most common and well-known when it comes to rocket engines. It's the same rocket engine that'll power NASA's Artemis moon missions. Still, the Artemis missions aren't the first time the RS-25 engine has been used. The primary space shuttle engine, the RS-25, has a proven track record of 135 flights over 30 years.

When the Space Shuttle Program ended in 2011, NASA put 16 RS-25 engines into storage. The space agency used it to help develop the International Space Station and launch the Hubble Space Telescope, among other missions. The RS-25 engines offered a way to save money by not building a new engine when NASA was searching for rocket engines to fuel the Space Launch System (SLS). NASA chose the RS-25 engines because of their ability to use technologies and expertise from the Space Shuttle Program.

The RS-25 is regarded as one of the most reliable, effective, and high-performance engines ever produced, and it was designed, engineered, and performed ahead of its time. Getting the RS-25 engine to work with the new SLS was one of the challenges. To get the venerable engine ready for flight in the more challenging SLS environment, engineers had to make design changes.

NASA and Aerojet Rocketdyne began adapting the engines, with the outdated flight controllers becoming the first to be redesigned. Engine flight controllers effectively monitor engine performance and maintain command and data protocols between the engine and the spacecraft. It was essential to provide a machine capable of running modern SLS algorithms. Four engines sit at the base of the rocket's center stage, directly next to a pair of solid rocket boosters, in the SLS configuration.

RS-25 engine nozzles are due for extreme base heating, especially within the first two minutes of flight. NASA crew added insulation to the nozzles to increase their efficiency. Another enhancement is the liquid oxygen tank's location in relation to the SLS's four RS-25 engines. The tank's position causes high pressure at the RS-25 inlets. The nozzles needed to be qualified to withstand the weight, which they could achieve with only minor modifications. In April 2019, all 16 retired space shuttle main engines passed acceptance inspection.

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