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From: starrfie@hydro.la.asu.edu (Sumner Starrfield) Subject: The latest on contamination (fwd)-HST Date: Thu, 4 Nov 93 13:25:09 MST Forwarded message: >From JJH@wfpc.la.asu.edu Thu Nov 4 13:08:02 1993 Date: Thu, 4 Nov 1993 13:11:19 -0700 (MST) From: JJH@wfpc.la.asu.edu To: astro@bigbang.la.asu.edu Message-ID: <vsnet-history1718@hoge.baba.hajime.jp> Subject: The latest on contamination More details on the contamination problem at the Cape. This time from Dave Leckrone: On Tuesday, November 2, flight operations officials at KSC escorted HST Project management (Rothenberg, Leckrone, Cepollina) and contamination control experts (Hedgeland, et al.) to PAD A at KSC to view firsthand the situation regarding the fine sand-like material that has been leaking into the PCR since last weekend (at least), some of which has fallen onto the double-bagged surface of the HST FSM payload. The material is approximately 90% man-made sandblasting particles and 10% paint chips. The particles range in size from 30 to 200 microns (Hedgeland refers to them as "boulders" by the normal standards of dust particulate contamination). The influx of particles is primarily concentrated on one side of the payload stack. Only a small number have been observed in the payload bay of Endeavor. The first deposit discovered numbered 50-100 relatively large particles distributed over several square meters at the top of the stack (solar array carrier package exposed to the PCR ceiling). These were vacuumed off and "alumylar" sheets were draped over the payload to collect any further deposits. The numbers and sizes of particles observed per day have since declined somewhat. An intensive activity was initiated to locate the source of the particles, and to seal off any obvious openings around the ceiling where they might enter the PCR. The onset of the contamination apparently concided with gale-force winds that blew at the Cape all day last Saturday. The winds induced shaking of the PCR and may have also blown through small openings in the PCR structure. This Pad was refurbished over the past year, and that included extensive sandblasting last summer. The room had been properly recertified as a class 100,000 or better cleanroom and monitoring by GSFC personnel prior to last weekend had confirmed that it was very clean. The present contamination is anomalous (doesn't even fall within the norms of definitions applied to various classes of cleanliness), and is speculated to result from a hidden reservoir of sand-blasting material left over from the refurbishment. Its location has not yet been found. Although we strongly doubt that any of the particles have made their way through the bagging material, the bags have many folds, joints and taped access openings, into which particles have certainly fallen and collected. There is no guarantee that carrier surfaces, insulation, etc., will not be contaminated when the bags are removed. Clearly the process of integrating the payload into the payload bay cannot proceed as long as the PCR is contaminated, and crews cannot pursue the source of the contamination as long as our payload is exposed in this way. The KSC people made a valiant effort to define a plan which would have kept us on the pad inside Endeavor's payload bay (doors closed), and under strong purge while they sought to find and correct the source of the problem in the PCR. In the end we were unable to accept this approach. As Senior Project Scientist I could not accept even a remote possibility that some of these particles might find their way into our hardware, or might be carried by the crew into the aft shroud. I also advised that the launch should be delayed if that was what was necessary to safeguard the payload. All parties (including NASA Headquarters) concluded that the best course is to return the payload to the PHSF facility, where it will be carefully cleaned, de-bagged, and inspected. The hardware will itself be cleaned as necessary prior to re-bagging and return to the pad. In the meantime the investigation of the problem at Pad A will be vigorously pursued. However, it is not clear that Pad A can be rigorously recertified quickly enough to support our launch. There is a high probability that we will end up launching from Pad B. As to schedule, it is clear that the KSC people and the GSFC crew are going to work their keesters off to stay on track for an early December launch. I think there is a reasonable chance that they'll succeed. I am not planning as yet to change my own reservations for a launch in the first week in December. We will give you any updates on this as soon as we have them. Cheers, Dave Leckrone
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