ET-119 arrives at KSC

by Chris Bergin

External Tank (ET-119) has arrived at the Kennedy Space Center (KSC), ahead of a potential launch date in May for Shuttle Discovery on STS-121.

The modified tank left Building 420, Cell 2 at the Michoud Assembly building (MAF) on Saturday and has been unloaded from its barge, following docking at the Florida spaceport.

The tank is the first of two required to allow STS-121 to proceed, with ET-118 needed to fly with Atlantis, primarily on STS-115, but also on the STS-300 rescue mission requirement as a precaution, should Discovery suffer serious damage on ascent.

A number of modifications have been made on the ET, some of which are yet to be certified, pending wind tunnel tests this month. The headline modification has been the removal of the protuberance air load (PAL) ramp – which shed a one pound chunk of foam during STS-114’s ascent.

Foam will still shed from the tank during launches, but NASA managers are keen to keep the size of liberations down to that vastly smaller than the briefcase sized chunk, which fatally wounded Columbia on STS-107.

‘We talk more in terms of mass which turns to kinetic energy than size, (but we’re looking for sizes) smaller than a matchbox which we’d like to stay beneath,’ said Shuttle manager Wayne Hale.

‘It has been our goal to get rid of any foam that might come off in large sizes.’
Further modifications may be made on the ETs during the final 17 flights of the Shuttle program, with the aim to bring down foam shedding to an absolute minimum.

However, Hale explained that some level of shedding won’t pose a threat to the orbiter’s TPS (thermal protection system), at which levels will have ultimately proven the new modifications to have solved the problem.

‘As you get to small sizes, then clearly we have what we call popcorn, which we’ve seen for years and that clearly does not pose a threat to us,’ he added.

‘So as we get down to the small pieces then we think we’ll of eliminated the threat.’

ET-119 will now be placed in the VAB’s checkout cell for further inspections, before being prepared for stacking in-between the two Solid Rocket Boosters (SRBs) which are currently being closed out after assembly.

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