The return of RS-25 engine testing at the Stennis Space Center has been delayed, following the discovery of a contamination issue involving cloth fibers inside the A-1 test stand duct system. Engine 0525 – which will be the first RS-25 to be test fired since the end of the Shuttle Program – has to be removed from the test stand in order for the ducts to be reworked.

A-1 Test Stand Issue:

The RS-25 has an impressive heritage of aiding the ride uphill for the Shuttle orbiters during their 30 year career.

Now re-purposed for use on the Space Launch System (SLS), the RS-25s are heading back into testing at the Stennis Space Center in preparation for the Heavy Lift Launch Vehicle’s first flight in 2018.

For that debut flight – known as Exploration Mission-1 (EM-1) – NASA’s Liquid Engine Office selected the first four engines that will loft the monster rocket uphill.

The four engines – ME-2045, ME-2056, ME-2058, and ME-2060 – are all established Shuttle veterans with numerous successful missions under their belts.

These engines are scheduled to be delivered from their current home at the Stennis Space Center to the Michoud Assembly Facility (MAF) in New Orleans at one-month intervals, beginning in September 2015.

SLS processing will see the engines being installed into the core stage at MAF, ahead of being shipped to the Kennedy Space Center (KSC).

After the last of those engines are delivered in December 2015, four more engines will be prepared and tested as contingency engines, to be available in case one or more of the first four engines need to be replaced.

Prior to the testing of the flight RS-25s, the first engine that is gracing the test stand for the opening tests of the RS-25 for SLS is Engine 0525.

This engine never flew in space, as it was one of two development engines used for component testing on Stand A-2 to support shuttle flights – 0528 was the second development engine.

The Stennis team will perform developmental and flight certification testing, collecting data on the performance of its new advanced engine controller and other modifications.

It was hoped the testing of 0528 – since installed on the the test stand – would take place in July, opening with a test firing. However, this was pushed back, prior to notes revealing the test schedule would be delayed further due to a contamination issue at the test stand.

“During a borescope inspection of the A-1 run lines prior to engine E0525 installation, a number of cloth fibers were found attached to the liquid oxygen (LOX) duct inner diameter (ID),” added notes via L2’s SLS section.

“The fibers were attached firmly and in-situ cleaning attempts were unsuccessful in removing all particles prior to engine installation. It was determined that these were consistent with fibers from a cleaning rag or something similar and were not detrimental to the engine.

While engine installation tasks proceeded, the Stennis team set up an investigation to identify the source of the fibers.

The investigation found the fibers belong to a cotton shop rag from a weld shop that had been involved with working on the LOX duct ID surface during manufacture.

The roughened surface (of the duct) was where the fibers were observed to be hanging up on.

The investigation team reported that, under microscope inspection, a piece of the run duct stock showed metallic particles loosely adhered to the ID surface and embedded in the ‘machining’ groves. Several were easily dislodged and identified as ID surface material.

“A tape sample was pulled from the same stock (after an identical cleaning process) and produced a rather large quantity of particles. This is an unacceptable condition and it was agreed that the entire run duct will need to be replaced or reworked (~30-ft of pipe),” added the investigation notes.

“There is a filter in the system and options to only rework the sections below the filter were discussed. However, due to the quantity of particles found on the tape sample, the likelihood that they are throughout the entire line, and their ease of shedding, it does not appear to be prudent to leave them in the system, even above the filter.

While the notes added the reworking of the duct will require the removal of the engine from the test stand – resulting in some test schedule slip – the information did not specify a realigned schedule for the hot fire. However, sources note the delay in the ballpark of “months”.

It is hoped the engine firing can still take place before the end of the year. Impacts to the overall schedule for the RS-25 and the SLS Program as a whole is not thought to be an issue, given the recent slip of the first mission into 2018.

The main driver for SLS’ schedule issues remains Orion, specifically the European Space Agency contribution to the program via their involvement with the Service Module.

(Images: Via NASA and L2 content from L2’s SLS and SSME specific L2 sections, which includes, presentations, videos, graphics and internal – interactive with actual SLS engineers – updates on the SLS and HLV, available on no other site.)

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