STS-124: Evaluations clear Discovery following aft incident

by Chris Bergin

Discovery has avoided damage, following a rare incident that occurred during her transition from horizontal to vertical in the Vehicle Assembly Building (VAB).

Engineers this week found an Emergency Life Support Apparatus (ELSA) unit had accidentally been left inside Discovery’s aft, which had fallen a short distance to a location behind Avionics Bay 6 during mating operations. Thankfully, the unit failed to damage any flight hardware in its path.

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Discovery Incident:

The ELSA unit is a high pressure cylinder of air with a hose attached to a plastic mask (head gear), used by engineers working in confined spaces on the vehicle inside the Orbiter Processing Facilities (OPFs). It weighs around five pounds.

The unit was spotted inside Discovery during aft closeouts at Pad 39A, leading to an engineering evaluation that initially found some damage via borescope checks.

‘Orbiter aft closeout operations continue. Emergency Life Support Apparatus (ELSA) unit, was found behind Avionics Bay 6. ELSA units are installed in the aft as a safety measure, whenever personnel are actively working in the confined space,’ noted Wednesday processing information.

‘The ELSA found behind AV Bay 6 was installed during OPF operations. Thorough inspections are being performed to ensure no damage to the flight hardware occurred during the transitioning of the vehicle from the horizontal to the vertical position. A team has been formed to conduct a full investigation.

‘Borescope inspections were conducted in possible areas the ELSA could have travelled to, and found some small tears in a TCS blanket – no other damage noted. ELSA bottle removed from AFT compartment.’

Those tears in the Thermal Control System (TCS) blankets – silver and goal mylar material that provides passive thermal control in various areas of the vehicle – are now classed as unrelated to the ELSA incident. It is not believed that any repairs need to be carried out on the blankets.

Due to where the ELSAs are located in the aft during OPF processing, the unit would not of travelled down the aft at any great speed, when the vehicle was moved into the vertical position.

Numerous elements of hardware lie in its path, meaning it would have likely bounced off various hardware and blankets before lodging behind Avionics Bay 6. Thankfully, inspections show that it failed to damage any of that flight hardware during its fall.

Though such incidents are rare, it doesn’t come close to what occurred in October, 1990, when a 9 foot long support beam audibly fell inside Atlantis’s aft compartment during her mating operations in the VAB.

‘While Atlantis was being hoisted to the vertical position, several employees involved in the operation heard several sounds which appeared to be coming from the orbiter,’ noted a status report from the time. ‘Officials were concerned and decided to proceed with the mating operation without detaching the sling upon its conclusion.’

However, the orbiter only suffered a broken purge duct and a requirement to replace a small portion of a manifold relief line in her Main Propulsion System (MPS). Minor abrasions to the surface coating of a strut and scuff marks on freon lines were also noted.

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Clearing Discovery from any repairs, Thursday’s processing report confirmed aft closeouts continued last night, though part of the process had to be carried out again this morning – due to an issue with the photography of the closeouts.

‘ELSA in the aft: Following data review, the Safety Investigation Board (SIB) released the constraint to S1287 allowing platform removal,’ added the processing information.

‘Orbiter aft closeouts (S1287): The 50-1 and 50-2 door was installed at 21:28 EDT. Aft closeout photos were accidentally deleted by Quality personnel. The 50-1 and 50-2 doors were removed in order to re-take photos. The doors were re-installed this morning and aft confidence check is planned for today on 1st shift.’

STS-124’s pad flow continues to proceed on the timeline for the May 31 launch attempt, with final ordnance installation/connection operations completed this week.

Upcoming flow milestones include APU (Auxiliary Power Units) cart lowering, which has been rescheduled to Friday, late 3rd shift. While preparations for S0071, Hyper/MPS pressurization and closeouts ‘call to stations for final operations’ is scheduled for midnight (EDT) on Tuesday, May 27.

International Space Station (ISS) Status Update:

Meanwhile, the International Space Station (ISS) has been busily preparing for the arrival of Discovery next month, ready for the two week, three EVA mission that will see the installation of the giant Pressurized Module of the Japanese Experiment Module (JEM) Kibo Laboratory.

‘1J/STS-124 Prep: A number of activities took place in preparation for the historic Kibo install mission. These activities included translating and checking out the Mobile Transporter at Worksite 6,’ noted an internal update this week.

‘(Also includes) adjusting the flow of the Medium Temperature Loop in the US Lab to ensure there is sufficient cooling flow for the new ECLSS rack, multiple crew conferences with both the Shuttle crew and the rotating crewmember Greg Chamitoff (Garrett Reismann will be returning), prepacking of return items, and R-bar Pitch Maneuver (RPM) training.

The Space Station Program Control Board (SSPCB) also approved several hardware enhancement CRs (Change Requests), specifically relating to replacements of Orbital Communications Adapters (OCA) and Orbital Replacement Units (ORU).

‘The first (CR) will replace the current OCA equipment. The OCA enables uplink and downlink of large files, video, and voice with the SSC Laptops (these laptops are not used for commanding). The new design will interface with the SSC’s via USB 2 connection vs PCI connection which required a docking port.

‘The board also approved the CR to replace 5 avionics Orbital Replacement Units (ORUs) with a single piece of equipment called the ICU (Integrated Communication Unit).

‘The 5 ORUs replaced are the baseband signal processor for Sband, the high rate frame multiplexer, the high rate payload data recorder, the high rate modem, and the video tape recorders.

‘Another very welcome enhancement as part of this change is the addition of two new voice loops, Space to Ground 3 and 4 (S/G) which will be transmitted via Kuband (S/G 1 and 2 are transmitted via Sband).

‘This provides 2 new abilities. First, we can now transmit synced audio with video (used to transmit video down Ku, audio down Sband, and then ground processing would be required to combine them). Second, we now have a backup method to talk to the crew if the Sband system is failed by using S/G 3 or 4, or in a loss of signal situation with the TDRS satellite network.’

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