RS-25 Engine 2059 – a veteran of five Shuttle missions – is scheduled to begin static fire testing at the end of February, initiating a test series on the engines that will be tasked with launching the Space Launch System (SLS). Meanwhile, Aerojet Rocketdyne explained some of the cost saving processes for the new expendable RS-25s that will fly with SLS in the second half of the 2020s.
Next Phase of RS-25 Stennis Testing:
A long series of initial RS-25 static fires were conducted at the Stennis Space Center during 2015, with testing resumed with the use of the development engine ME-0525 hosted in the A-1 test stand at Stennis.
Engine 0525 never flew in space, as it was one of two development engines used for component testing on Stand A-2 to support shuttle flights.
Seven tests were conducted on ME-0525, allowing engineers to validate a new engine controller and how the RS-25 engine design functions in the SLS operating environment, which has functional and environmental differences from the Space Shuttle.
The seventh and final test in the series with ME-0525 was conducted in August, with the goal of beginning the next test series on a flight engine by the end of the year.
Engine 0525 was replaced in the A-1 facility last year, with flight engine 2059 installed on November 4.
Engine 2059 is a veteran, having helped power five Space Shuttles into space, flying three times on Shuttle Orbiter Atlantis (STS-117, STS-122, and STS-125) and twice on Orbiter Endeavour’s last two flights (STS-130 and STS-134).
The engine flew all five flights installed in the center – or number one – position. It was the last flight engine to be shipped from the Kennedy Space Center to Stennis, arriving in April, 2012.
Documentation shows this flagship – in terms of flight data – engine will fly with SLS on the second flight of the rocket.
Testing has been delayed from its initial target, following the installation of the ME-2059 on the A-1, with the latest documentation (L2) showing the return of static fire testing has been rescheduled for No Earlier Than (NET) February 25 – although this date may slip again in the near future.
Once this “calibration run” test has been conducted on ME-2059, data from this engine will be used to help further calibrate the systems on the A-1 test stand and the data stream. The test series then ups its pace, as more engines undergo “green runs” to prepare the report cards of the flight engines ahead of being officially assigned to fly with SLS.
It is understood that ME-2063 – the newest “legacy” build engine – will undergo its “green run”.
This will be followed by Development Engine 0528, which will receive a full test series of 10 firings.
The next engine to be tested will be ME-2062, which is the last engine that was built while STS was still flying. This 2010 build engine will also receive a full “green run” test.
By this point, all 16 of NASA’s current inventory of “legacy build” RS-25s 0 using the stainless steel regenerative cooling nozzles – will have been fired.
The ultimate goal is to prepare the flight engines for the milestone that will culminate in the “green run” of four Main Engines at the same time, namely ME-2045, ME-2056, ME-2058, ME-2060, all mounted on to the core stage of the first SLS core.
The Green Run testing will be conducted on the modified B-2 test stand at Stennis, the first time four RS-25 engines – on the first Core Stage – will be fired for a full mission duration of approximately 500 seconds.
That core will eventually be transported via the upgraded Pegasus barge to the Kennedy Space Center (KSC) for mating inside the Vehicle Assembly Building (VAB) ahead of the first SLS mission, known as EM-1.
The launch date for EM-1 is currently in the mid-to-late 2018 timeframe, although numerous NASA sources claim they have been told this unlikely to remain the schedule.
Aerojet Rocketdyne RS-25 Second Life:
As recently reported by this site, six new RS-25s will compliment the existing stock of 16 engines, allowing SLS to have enough engines through to her fifth flight.
Via the restart of RS-25 production facilities, Aerojet Rocketdyne will modernize the engine to make it more affordable for SLS – previously tagged as the switch from the reusable RS-25D used on the Space Shuttle to the expendable RS-25E.
The engine will be known only as the RS-25 during its SLS career.
Moving to an expendable version of the RS-25 includes lessons learned from other engines in the company’s stock, such as the RS-68, which flies as an expendable engine on the first stage of the United Launch Alliance Delta IV.
“We have performed studies that suggest highly matured designs can be affordably introduced into the expendable version with minimal recertification,” noted the company in response to questions from NASASpaceFlight.com
“One example is a main combustion chamber derived from the expendable RS-68 engine that has demonstrated to be robust, reliable and cost-effective.
“Another area is at the articulating joints, which are complex bellows designed to meet Shuttle reusable life requirements, that can now be replaced with simple flex hoses for an expendable application – again based on RS-68 flight experience.”
As noted in NASA’s Justification for Other Than Full and Open Competition (JOFOC) overview, Aerojet Rocketdyne is the only viable option for providing additional engines for SLS.
For its part, Aerojet Rocketdyne will be focusing on the transition to the expendable RS-25 within the required certification parameters, while focusing on improving production efficiency.
“There will be a big focus on how to drive efficiency, and thus improve cycle time and reduce waste, during the entire fabrication process,” added the company.
“SSME (Space Shuttle Main Engine) was fortunate to have validated this process on nozzle production and it is our intention to use the same process on all the high valued components of the engine.
“Future changes to the engine design and processes will be coordinated and concurred with by NASA to yield a final engine configuration, that for the time being is simply designated RS-25.”
(Images: Via NASA and L2 – including photos from Philip Sloss and SLS renders from L2 artist Nathan Koga – The full gallery of Nathan’s (SpaceX Dragon to MCT, SLS, Commercial Crew and more) L2 images can be *found here*)
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