A test motor for NASA’s Space Launch System, designated Qualification Motor 1 or QM-1, has run into a problem. QM-1, which is manufactured by ATK, is manifesting voids in the aft segment. As ATK’s Trina Helquist explained to AmericaSpace:
“During routine X-ray inspection that followed the casting of the propellant, un-bonds and voids were found. Un-bonds are areas where the propellant did not adhere to the insulation/lining of the case. A void in this situation is an air pocket in the propellant.”
While this might ordinarily be treated as an unfortunate but routine snag in the complicated development process, this is the second time this particular section has developed such voids. Earlier this year NASA requested that ATK discard and recast the first QM-1 for exactly the same reason. It is now this recast version that has put testing on hold once again.
NASASpaceflight.com is investigating the issue:
Voids – though rare – are one of the items screened for in order to pass stringent operational requirements. Even for ground tests they could have significant impact to the time pressure traces that subsequently impact flight analysis models.
The likely cause of the voids points to a change in processing when using a relatively new material in the insulation lining for the segments, a material that has replaced the previous use of crysotile – the most common mineral form of asbestos.
The replacement of asbestos in the insulation package has been noted as one of ATK’s long-term goals. Crysotile-free rubber insulation had already been qualified for Shuttle, but never used in flight. It was then baselined for Ares I and subsequently for the SLS boosters.
For more details of the investigation, continue reading here. The QM-1 test will likely be rescheduled sometime in 2014.