Discovery’s tank suffers foam issue

by Chris Bergin

The Mission Management Team (MMT) are meeting throughout the day to discuss a course of action – after a crack was found in Discovery’s External Tank. Managers are deciding on whether to repair at the pad, or fly “as is”.

However, two other issues that have come to light during Shuttle Discovery’s opening two attempts to launch on STS-121, but both are workable, according to officials and sources.


The crack, found on – or near – the 17 inch feedline bracket was spotted during an inspection carried out after the detanking of ET-119, following Sunday’s scrub. A piece of foam was also found on the MLP (Mobile Launch Platform).

The MMT are set to hold their daily press conference later today. Updates will follow. **Live update thread of the media conference**

Meanwhile, the failure of a heater on RCS (Reaction Control System) L5L, and an intermittent fault on a five percent LH2 ECO (Engine Cut Off) sensor, won’t affect the July 4 launch attempt – should NASA decided to fly ‘as is’ with the foam issue.

The ECO sensor in question is not critical to flight – and does not fall under the waiver that was issued in case of a repeat of STS-114’s sensor issues.

‘We watched it go from DRY back to WET – it toggled a few times before going dry – around the same time as the LOX 5% sensor,’ noted a source.

NASA, however, are not concerned, noting it confirms their suspicions of the ‘bad lot’ from which the sensor in question came from. The main LH2 sensors in the bottom of the tank are from a new batch, following their replacement in the Vehicle Assembly Building (VAB), prior to stacking with Discovery.

The failure of the heater on the RCS thruster is also not proving to be a problem for engineers to overcome, with a plan written up on compensating for the loss of the thruster on orbit.

While it is possible the stresses of ascent may bring the heater back on line, orbital positioning of the orbiter may ‘warm’ the thruster enough to be used.

Engineers at JSC (Johnson Space Center) tested the plan in the simulators – shortly after the heater was deemed as unworkable – to see how that would affect the rendezvous with the International Space Station (ISS).

Sources note that if they need to deselect L5L, then the flight software down-modes the DAP (Digital Auto Pilot) to FREE (Free Drift Mode). This will make matters complex for the orbiter, but there is understood to be plans in place for worst-case scenarios.

**INFRARED STS-121 MUSIC VIDEO** – Trust Discovery.
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