NASA reviewing showstopper for STS-120 – RCC panels in question

by Chris Bergin

NASA Engineering and Safety Center (NESC) have officially recommended for three of Discovery’s RCC (reinforced carbon-carbon) panels to be replaced, after they were found to have “weakened SiC to carbon substrate adherence,” or ‘debonding’ of the top layer.

NESC’s recommendation is being reviewed by shuttle management, with a decision to be taken during the Flight Readiness Reviews (FRR). Replacement would lead to a rollback of the vehicle.

**The most comprehensive collection of Shuttle, Ares, Orion and ISS related presentations and mission documentation, plus expansive daily processing documentation and updates are available to download on L2 **

Extensive STS-120 Special Section on L2 now live, including Flight Plans, Handbooks, Manuals, documentation and presentations. STS-122 to STS-127 documentation already available.

STS-120 L2 Special includes 19 MOD Flight Readiness Review Presentations (see sample left) – the most expansive overview of the mission. **Click here for sample**
L2 is the world’s only ‘as it happens’ area on the net that gives you a seat next to the shuttle engineers and managers, in real time.

**LIVE news updates on Discovery STS-120 PAD Processing**

**LIVE news updates on Endeavour STS-123 Processing**

**LIVE news updates on Atlantis STS-122 Processing**


The RCC panels in question are on both leading edges of Discovery’s wings, namely panels 9R, 12L, and 13R.

The root cause of the issue is not known, but it is understood to be related to oxidization within the panels that causes the decrease in the adhesive bond that holds the SiC layer in place. However, that has not been confirmed by the resulting scans of the panels.

The issue is impossible to observe with the naked eye, and NASA have been using high tech analysis methods – such as Microscopy – to spot degradation in SiC Coating adherence.

The concern relates to the potential inability of the current on orbit scanning process – via the OBSS (Orbiter Boom Sensor System) – of seeing increased problems with the top coating of the RCC panels.

That becomes a problem due to notes of analytical data showing that a loss of this top coating holds a risk of burn through on all three panels in question, following a sustained period of heating.

As a result, NESC are recommending that the shuttle program should replace panels 9R, 12L, and 13R, which can’t be achieved at the pad due to accessibility issues. It is not clear if the process could be completed in the vertical. Either way, a rollback would delay STS-120 to December at the earliest.

However, given the data appears to point to worst case scenarios, and that flight experience has seen such issues before, shuttle managers may decide that the risk is no greater than they’ve previously flown with, allowing the launch to proceed on track.

**(NOW INCLUDES STS-118 Re-Entry Video) Ride home through the fire, sparks and plasma of re-entry with Atlantis, Discovery and Endeavour. FIVE Stunning high quality 2hr, 355-400mb Camcorder and HUD videos – from payload bay closure – through re-entry with a astronaut held camcorder video – to post landing – several more videos showing landing from 90,000 ft also available – Now includes HALO II Re-entry video**

This would appear to be good rationale, as NESC are noting that once the suspect panels have been removed, a variety of tests would be required to back up their claims, and even then the results may not provide conclusive data to justify a decrease in risk – by their own admission.

Managers and engineers at the FRR will continue to pore over the data, and will likely come to a conclusion over the next 24 hours.

That FRR process is more convoluted for this mission, with pre-FRRs and a large Shuttle FRR (taking place this week) ahead of another final top level FRR next week.

Timelines for the FRRs show the Shuttle Program Flight Readiness Review on October 9th and 10th, the MMT (Mission Management Team) Prebriefing on October 12th, the Level 1 SOMD Flight Readiness Review on October 16th and L-2 Prelaunch MMT on October 21st.

Pad processing continues to proceed well, with only minor troubleshooting issues, which are commonplace for such flows.

A few hours of contingency time remains, but that takes into account a cease to pad operations during the launch of the Atlas V carrying the Wideband Global SATCOM satellite Wednesday night.

‘An Atlas V is currently scheduled for launch from Complex 41 on Wednesday October 10th with a targeted T-0 at 2022. The launch window extends from 2022 – 2133. The launch vehicle is flying in the 421 configuration with a 12 foot fairing, two solid rocket boosters and a single engine Centaur upper stage.

‘This configuration allows for a concern for Toxics in the LC 39 area. Pad A will be cleared at 1700 Wednesday and Pad B will remain open.’

L2 members: All documentation and quotes – from which the above article has quoted snippets – is available in full in the related L2 sections, updated live.

**STARLIGHT: NEW STS-117 MISSION REVIEW MUSIC VIDEO** – STS-118 Mission review video also available. 

(Video section is FREE, but you need to sign up as a member of the forum to enter the video section of the site. We only use your e-mail to send you your password. It will not be used for spam etc.)

Related Articles