Driven by testing – not schedule

Space Shuttle Program manager Wayne Hale has stated that the Return to Flight of the fleet will be determined by the outcome of testing, not schedules.

Discovery is currently being prepared for a May launch – but on-going testing on the External Tank’s PAL ramp, added to the timeline which it affects, will be the ultimate guideline from which NASA will make a decision on when the next launch will occur.
Stating that the only people who pressure him over the launch date of Discovery are members of the media, Hale explained that they simply aren’t going to do anything ‘stupid’ by way of adhering to a schedule that can’t be finalised, while they evaluate how to ensure foam liberation from the ETs has been solved.

‘The only people we get schedule pressure from is from the media,’ said Hale, during today’s NASA press conference. ‘We have not set a launch date. If the testing comes out as planned, then there is a probability that we’ll launch in May.

‘Everything determined by the testing not the schedule. We’re not driving to a date on a calendar to do something stupid because of a schedule date.’

The testing involves 500 blocks of a fault tree to evaluate the potential reasons why foam liberated from the ET during STS-114’s ascent. 75 percent of that fault tree has been worked through, with the remaining 25 percent on hold while the testing processes on the PAL ramp are completed.

The testing of the PAL ramp on ET-120 at the Michoud Assembly Facility (MAF) is being hailed as a great opportunity, due to the two occasions it was loaded with super-cold propellant ahead of STS-114.

Problems with the Engine Cut Out Sensors and the LH2 Diffuser meant ET-120 never flew with Discovery. Instead, the Shuttle was rolled back and swapped with what was then Atlantis’ ET (ET-121) before being launched in July.

During testing on ET-120’s PAL ramp, nine small cracks were found, primarily on the LH2 section of the section of foam. Engineers continue to ‘slice’ through sections of the ramp to try and find reasons and solutions for the cracks and subsequent liberation during ascent.

Again omitted from the conference was the information that pointed to a previous repair job on ET-121, in the crotch area of the intertank section.

MSFC (Marshall Space Flight Center) chief engineer John Chapman would only touch on the subject by noting they are still looking through worksheets from when the ET was at MAF, prior to shipping to KSC (Kennedy Space Center).

‘We are replacing all of the mats with new mats for work on the tank,’ added Chapman, noting on-going evaluation of how crushing of the foam by engineers working on the ETs at MAF affects the surface.

‘We are well into the verification of an enhanced spray process, should we wish to replace the PAL ramps,’ he also noted. ‘It would be very similar to what we do on the first 10 feet of the PAL ramp (the LH2 section). This involves a series of spraying on mock up tanks, to verify we have the process control right.’

Another area of the ET that is being looked at is the Bi-Pod ramp, which is undergoing a modification.

‘The Bi-Pod is a potential area for cryo-ingestion – which could cause a piece of foam to come off,’ said Chapman. ‘We will seal the wire down the bipod. The close out of the foam will not change – it will be the same application.

‘All of our activities are in support of the correct launch date, and won’t be affected by schedule pressures.’

While the orbiters at KSC continue to have their gap fillers evaluated, along with sections of their thermal protection system (TPS), Hale made it clear that NASA fully intends to get to a point where they are taking even greater care of their space vehicles.

‘We are taking a lot more care with our vehicles,’ he noted. ‘Sadly experiences have shown we have to take these greater steps with our vehicles.

‘We have assessed the plan forward, and if the testing comes in as we expect it might, and we get the workforce back to applying foam, then clearly we have an opportunity for the Spring. As we get the results back and work is progressing, we will be able to select a firm schedule. We don’t want the schedule to drive the work.’

‘We do need to get to the bottom of the foam liberation. We going to get to the practical solution so that we don’t lose large amounts of foam off the tank. We think we can accomplish that in the next few months.’

NASA is not yet sure if they’ll make the May launch window for Discovery – as several elements of processing will determine if all the key elements are ready to support STS-121 for a Spring launch.

‘We need to start reapplying Pal Ramps January time,’ said Hale. ‘The ETs needs to be shipped from MAF first week in Feb. From there it’s compressed flow to get to the launch window.’

Even though Hale went to great measures to re-iterate than NASA isn’t working to a schedule, the current plan involved 19 flights before the Shuttle is retired in 2010.

Hale remains confident that the remaining lifetime of the Shuttle fleet will carry out the intentions drawn up in the Vision for Space Exploration.