A CHUNK of foam fired by an air cannon slammed into the fibreglass wing panels on the space shuttle prototype Enterprise last week. The impact opened a gap 56 centimetres long between panels, lending weight to the theory that foam insulation surrounding Columbia鈥檚 giant fuel tank broke away and fatally damaged the shuttle鈥檚 heat shield when the doomed shuttle lifted off in January.
Tests on the more fragile reinforced carbon composite wing panels actually used on the shuttles are not due to be performed until next week. But NASA is already taking steps to minimise the risk of foam being dislodged on future missions. One casualty could be the spectacular night-time shuttle launches that NASA has used in the past to put the craft into certain orbits.
The Columbia Accident Investigation Board said last week that when Atlantis was being launched in October 2002, long-range monitoring cameras captured images of foam breaking off the struts that attach the shuttle to its fuel tank 鈥� the so-called 鈥渂ipod鈥� area. The CAIB is concerned that when Endeavour lifted off the following month cameras would not have caught any foam chunks peeling off because the launch took place at night, when rocket plumes would have illuminated the shuttle unevenly. The next launch was Columbia鈥檚. The CAIB has made no recommendation on the wisdom of night launches, but it is possible that the difficulty of videoing such launches could put paid to them.
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One safety measure that is being implemented is the removal of the foam from the bipod struts, where it prevents ice building up on the pipes carrying cryogenic fuel to the shuttle engines. A NASA spokesman says it is likely to shift to a design in which heaters warm the pipes, preventing ice from accumulating.