Washcloth delays SLS engine tests

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The testing of an engine for the giant SLS rocket will be delayed because engineers have found the remains of a washcloth in the ducts of the test stand at Stennis Space Center.

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.

Replacing the duct will cause a several month delay in the test program. Fortunately for NASA, they have some wiggle room (for the moment), since the entire SLS schedule has already slipped a year to 2018.

Nonetheless, do not be surprised if this is only the first of many further delays.



  • geoffc

    A duct that will handle thousands to millions of gallons of LOX is being replaced since it has some cotton fibers on it. Odds are really good on first test, the LOX will combust the fibers and they last micro seconds. (I know, there are real concerns, early ignition, whatever, but still seems strange).

    Contrast a Merlin 1 where one of the acceptance tests is to drop a standard 5/8″ nut through the fuel flow, for the pump to handle and not RUD.

    Designing for reliability is tough.

  • Cotour

    I once fully assembled a Chevy 350 LTI engine and wondered why it was bogged down upon the first test run. I assembled the top end and left a towel stuffed in the new manifold. It happens :)

  • Pzatchok

    Stuff does happen, but if you had 40 people looking at and helping you with that engine and a 4 million dollar budget you would think someone would find it long before you started the engine.

  • Vladislaw

    but but .. my dog ate my homework… can you give a few more days?

  • Matt in AZ

    Bob, on Tuesday’s john Batchelor Show, I heard you wondering about why NASA was bothering to test the Shuttle engines at Stennis, since they’re a totally proven and known system. In a July issue of Aviation week, there was a mention of tests of that engine with a new controller that had originally been developed for the J-2X engine. The obsolete electronics supply chain for the shuttle is definitely an issue that needs to be addressed in any shuttle-derived hardware production. Which of course only adds to the ever-expanding costs of SLS…

  • Matt,

    Thank you for the information. It explains the tests, though it also provides further proof that SLS is a stupid waste of money.

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