Aerojet Rocketdyne refurbishing RS-25 engines for Artemis 1 launch and production restart testing - NASASpaceFlight.com - NASASpaceflight.com

With the completion of another single-engine RS-25 development test, Aerojet Rocketdyne is now refurbishing five engines at the Stennis Space Center in Mississippi for their next use.

After the second test firing of the Retrofit 2 series in the A-1 Test Stand on April 6, development engine 0528 is going through a streamlined refurbishment prior to its next firing as a part of the production restart Retrofit 2 test series.

In parallel, the four RS-25 engines installed on the first Space Launch System (SLS) Core Stage in the nearby B Test Stand are being taken through a longer refurbishment checklist for flight engine hardware.

The next planned ignition for those Core Stage engines is for the first SLS launch on the Artemis 1 mission to send an Orion spacecraft to lunar orbit.

Hot-fire testing of the two current RS-25 ground test engines resumed on April 6 with the second test in the Retrofit 2 series.

Aerojet Rocketdyne (AR) said the primary objectives of the test were to demonstrate engine thrust vector control (TVC) and operating characteristics of the new oxidizer preburner oxidizer valve (OPOV) retrofitted on E0528.

The single-engine, hydrogen-oxygen A-1 test stand was modified a few years ago to support gimbaling the RS-25 and other possible future customers.

AR noted that the demonstration included 118 cumulative seconds of engine gimbaling by the new test stand system.

(Photo Caption: Aerojet Rocketdyne is now processing the five RS-25 engines shown in this composite image.  Engine 0528 on the left is a development engine that is ground-testing newly-produced engine components retrofitted to its powerhead.  Engines 2045, 2056, 2058, and 2060 are seen firing during one of the SLS Core Stage Green Run Hot-Fire tests; all five engines were originally Space Shuttle Main Engines used by the program for flight operations and engineering support.).

The Retrofit 2 test series is the second of four in support of certifying the restart and modernization of RS-25 engine production.

The SSMEs were adapted largely as-is to the higher SLS operating requirements, which were recently demonstrated in the second Core Stage Green Run Hot-Fire test in the B-2 position of the B Test Stand at Stennis on March 18.

In the April 6 single-engine test in the A-1 stand, E0528 started and throttled up to 100 percent power level before throttling up to 111 percent a little over six and a half seconds after ignition, simulating what the new flight engines will do during SLS launches immediately after liftoff.

Nominal “start box” conditions at the liquid oxygen and liquid hydrogen inlets were used for the test; for some development testing, the test stand can be configured to supply pressure and temperature conditions at the engine inlets at the edges or corners of the engine’s standard pressure-temperature ranges at start.

Aerojet Rocketdyne also said that E0528 was throttled at 111 percent power level for 384 seconds during the test, with another 23 seconds at 90 percent and 40 seconds at 80 percent power level where the engine was shut down.  The restarted production lines of new RS-25 engine components are introducing modern manufacturing techniques, like additive manufacturing (AM).

With the April 6 test completed, the development engine joins its four former SSME teammates in refurbishment for their next firings.

E0528 is being refurbished for its next ground test firing later in April; after two ground tests of the Core Stage, the next ignition of the four RS-25 flight engines will be for the first SLS launch on Artemis 1.

The RS-25 engine design is largely the same between the development engines being retrofitted with production restart components and the engines that will power the Core Stage on Artemis 1; however, the usage environments are different and the requirements account for that.

(Photo Caption: The four RS-25 engines in Core Stage-1 fire in the B-2 position of the B Test Stand at Stennis Space Center on March 18. The veteran engines served as test support equipment for the Green Run, which was a test of the new SLS Core Stage. The second Hot-Fire ran a full 500 seconds in duration, accomplishing all planned test objectives.).

Ground testing of development engines often go beyond flight specifications, not just in terms of temperatures and pressures within a single firing, but also in terms of the number of firings conducted

“We can’t go outside those [operating] boxes like development testing can go do.” Minimizing wear and tear on the flight engines and operating within the specified limits during flight use provides extra margins of safety that are mandatory for human-rated spaceflight

New Honeywell engine controller units that were developed as a part of adapting the Block II SSMEs for use on SLS as the RS-25 were coupled with pre-Block II hardware on an AR-22 engine that was test-fired ten times in ten days in the summer of 2018

The first purge is a part of the engine shutdown sequence; for vehicle firings, the gaseous helium comes from the supply stored in five large composite overwrapped pressure vessels (COPV) in the engine section of the Core Stage instead of from the test stand

(Photo Caption: An Aerojet Rocketdyne AR-22 engine fires in the A-1 Test Stand in July, 2018, as a part of a rapid-reuse demonstration of the SSME technology for the Defense Advanced Research Projects Agency’s since-cancelled (DARPA) Experimental Space Plane (XSP). The test team at Stennis Space Center fired the engine, assembled from retired pre-Block II SSME hardware, ten times in ten days. The average time between tests was about 18.5 hours.)

After the Core Stage is inerted and it is safe for workers to return to the test stand, engine drying purges begin

“And that’s one of the four critical things that we have to do before we say that the engines are acceptable [for travel] before you pull the Core Stage out of the test stand,” he added

Following both hot-fire tests on the Core Stage as a part of the Green Run design verification campaign, both the engines and parts of the Core Stage were refurbished for their next firing

Tasks within the overall refurbishment work on the engines and the stage are divided and organized so they can be performed in parallel with each other as much as possible to maximize productivity

The thermal blankets protect the engine powerheads from the heat generated when they are firing and the eight-minute long, static ground test exacerbated the heat flux on the bottom of the stage; for inspections and servicing inside and outside, they are removed

“We have enough room in the engine opening to stand through that engine opening hole and do a lot of the inspections and a lot of the work around the engine through the engine opening.”

Access to an engine in the A-1 Test Stand is greater than inside the four engine cluster installed in the Core Stage

The engine powerhead is not covered by any flight or ground test equipment in the single-engine test stand, where the whole test stand is substituting for a rocket stage as a engine services provider

An initial estimate of a couple of months worth of refurbishment work on the engines was refined to about six weeks last Summer, with half of the work done in the B-2 stand at Stennis and the remainder in the Vehicle Assembly Building at KSC after the Core Stage is stacked with its Artemis 1 Solid Rocket Boosters

By the time the plan was implemented after the January 16 Hot-Fire test, almost all the engine refurbishment work was expected to be completed at Stennis

They were ready to support a February 25 test date before issues with a Core Stage prevalve pushed the test to March 18

A third critical area of refurbishment work after the engines are fired is inspecting the 1080 coolant tubes in each engine’s nozzle for leaks

Those four areas were previously prioritized as critical to removing the Core Stage from the stand to place it back on the Pegasus barge for transport to KSC

Sometime after the stage arrives at Kennedy Space Center (KSC), one of the final engine refurbishment tasks will be a few changes to fully configure the engines for flight.)

“So we have to put the engines back in the transportation configuration, which is basically we’ve got to put [in] a transportation throat plug.” Leak checks deferred until after the Core Stage arrives in Florida for launch preparations and the blanking plates are removed, then those engine-MPS interfaces can be leak checked with the engines in their flight configuration while stacked in the VAB

The launch team will perform the engine flight readiness test (FRT) that checks out the electrical, computer, hydraulic, and pneumatic systems in all four engines, along with their built-in redundancy, and runs the valves through a countdown and ascent timeline