A new issue with Atlantis' External Tank LH2 Feed-through connector hardware will require further investigation, after cracks were found on the glass seal below the pins on ET-125's removed external connector.
At present, engineers do not believe it is related to the Engine Cut Off (ECO) system anomalies, as the process begins at the pad to install a replacement Feed-through connector system into the tank, in time to allow STS-122 to launch in early February
The surface cracks were observed on the vitreous glass seal, via initial inspections over the weekend at the Marshall Space Flight Center (MSFC). Engineers used a magnification of x50 to gain imagery of the 'crazed' cracks.
The concern relates to the potential that unacceptable amounts of liquid hydrogen could leak through those cracks during ascent, which would breach safety rules. As a result, engineers are being tasked with understanding and eliminating the concern via testing. 'Surface cracks could result in unacceptable LH2 leakage during ascent (Crit. 1). Rationale required prior to installation and flight. This is currently the main focus of the engineering evaluations on the cracking, after opening results showed that there is neither the flight history, nor the data, that supports any correlation between the observation of cracked glass and the ECO sensor system anomalies.
As a result, MSFC engineers are now tasked with a separate investigation, likely in cooperation with the vendor, to pinpoint the exact cause of the cracks, along with a full understanding of any potential safety implications during the ride uphill.
Opening data shows that engineers have been aware such cracks can exist, and are the result of processing. Sources believe that certain levels of observed cracking leads to hardware being rejected - via a quality control process. However, such cracking has only when spotted via inspections that are to a certain level of magnification.
Due to the intense focus on ET-125's connector, the cracking was observed at magnification levels of up to the power of x50. This may add confidence, due to the likelihood that cracking is typical - though not always spotted - yet has not exhibited a problem on any flight of the shuttle.
However, NASA aren't taking any chances with the connector hardware, following the problems associated with STS-122. A full investigation will be utilized in parallel with the MSFC cryogenic testing of ET-125's connector, as engineers hope to recreate the error seen during the two launch scrubs and subsequent tanking test, with an eye on confirming that the removed external connector is at fault.
At present, engineers do not believe it is related to the Engine Cut Off (ECO) system anomalies, as the process begins at the pad to install a replacement Feed-through connector system into the tank, in time to allow STS-122 to launch in early February
The surface cracks were observed on the vitreous glass seal, via initial inspections over the weekend at the Marshall Space Flight Center (MSFC). Engineers used a magnification of x50 to gain imagery of the 'crazed' cracks.
The concern relates to the potential that unacceptable amounts of liquid hydrogen could leak through those cracks during ascent, which would breach safety rules. As a result, engineers are being tasked with understanding and eliminating the concern via testing. 'Surface cracks could result in unacceptable LH2 leakage during ascent (Crit. 1). Rationale required prior to installation and flight. This is currently the main focus of the engineering evaluations on the cracking, after opening results showed that there is neither the flight history, nor the data, that supports any correlation between the observation of cracked glass and the ECO sensor system anomalies.
As a result, MSFC engineers are now tasked with a separate investigation, likely in cooperation with the vendor, to pinpoint the exact cause of the cracks, along with a full understanding of any potential safety implications during the ride uphill.
Opening data shows that engineers have been aware such cracks can exist, and are the result of processing. Sources believe that certain levels of observed cracking leads to hardware being rejected - via a quality control process. However, such cracking has only when spotted via inspections that are to a certain level of magnification.
Due to the intense focus on ET-125's connector, the cracking was observed at magnification levels of up to the power of x50. This may add confidence, due to the likelihood that cracking is typical - though not always spotted - yet has not exhibited a problem on any flight of the shuttle.
However, NASA aren't taking any chances with the connector hardware, following the problems associated with STS-122. A full investigation will be utilized in parallel with the MSFC cryogenic testing of ET-125's connector, as engineers hope to recreate the error seen during the two launch scrubs and subsequent tanking test, with an eye on confirming that the removed external connector is at fault.
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