STS-134: SSMEs ready to fly – Stack cleared following more bad weather

by Chris Bergin

Endeavour is happily moving through her pad flow, despite having to endure yet more bad weather over her launch pad – resulting in additional inspections for hail damage this week. Thankfully, no new observations of damage have been noted on the External Tank (ET-122). Meanwhile, the Flight Readiness Review (FRR) for the Space Shuttle Main Engines (SSME) has been completed without issue.

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Endeavour is snugly protected inside the Rotating Service Structure (RSS) at Pad 39A, although the top of her tank is exposed to the elements. While it is not confirmed hail actually hit the tank – for the second time in around a week – inspections have shown no additional areas of interest, following what was only minor damage from the previous storm.

“OV-105/SRB BI-145/RSRM 113/ET-122 (Pad-A): Tuesday’s bad weather generated reports of possible hail observed on OTV (TV Cameras) at the pad. Another iteration of S0018.100, Op 90 has been generated. (However,) Instrumentation did not have any corroborating evidence of hail at Pad-A,” noted the NASA Test Director (NTD) report (L2).

“ET Mechanical, Launch Site Support, NASA Safety, and MAF (Michoud Assembly Facility) representatives completed a walk-down with no new observations of damage on the ET found.”

Interestingly, work is still being completed on clearing the vehicle and pad from the initial storm last week, although the Engineering Review Board (ERB) are officially satisfied that ET-122 is safe to fly as-is – with the very minor damage not requiring any repair work.

“The ERB also concluded that the ET foam hail indentations will be ok to fly as-is, and dynamic loading on the SRB (Solid Rocket Booster) hold down posts should not be a concern,” the NTD report noted. “Ground Support Equipment (GSE) evaluations still remain to be completed, as well as the GUCP (Ground Umbilical Carrier Plate) alignment guide pin fit check.”

Processing has continued in a nominal fashion since the four additional – and since closed – Interim Problem Reports (IPRs) were generated during the Terminal Countdown Demonstration Test (TCDT).

S0024 HPU hydrazine loading operations have been completed, while the APU/HPU (Auxiliary and Hydraulic Power Unit) cart lowering and transport to the fuel farm is in work this week. S5009 Ordnance Installation has been rescheduled to April 18 following the change to the launch date to April 29, caused by an International Space Station (ISS) schedule and Dual Docked Operations (DDO) conflict with a Russian Progress resupply ship.

Several tankers of LH2 are expected at the pad complex on Friday, while preparations are continuing to push towards offline testing of STS-134’s primary payload, the Alpha Magnetic Spectrometer-2 (AMS-02), this weekend – providing work after Friday isn’t impacted by a potential government shutdown.

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“S07134 AMS End-to-End Test was completed,” added the NTD report. “The AMS payload will be powered up to support off-line testing through the weekend.”


Endeavour’s ride into orbit at the end of this month will be aided by her three Space Shuttle Main Engines (SSMEs). The noisy trio are no stranger to the aft of the youngest orbiter in the fleet, after pushing her uphill during STS-130. The engines were installed in the following positions on the orbiter: 2059 is ME-1, 2061 is ME-2, while 2057 is ME-3.

With the Space Shuttle Program (SSP) Flight Readiness Review (FRR) completed (15 presentations available on L2), documentation shows managers first overviewed the performance of Discovery’s SSMEs during STS-133 via the In Flight Anomaly (IFA) review at the Program Requirements Control Board (PRCB) meeting (14 presentations available on L2).

“Engine operation was nominal. ME-1 2044, ME-2 2048, ME-3 2058 – No SSME IFA Identified,” noted the STS-133 SSME IFA presentation, outlining the superb performance from the reliable workhorses which have ably supported the Space Shuttle Program since the 1980s. “All SSME observations are encompassed by previous flight and/or test experience and identified as no impact.

“One (minor) observation (believed to be related to the Oxidizer Preburner Oxidizer Valve (OPOV) – though full information is restricted) – was presented to the MMT (Mission Management Team) – no IFA recommended.”

Only one item of interest made it into the FRR documentation for the SSMEs, referencing the incident when an ELSA (Life Support) bottle fell from the entrance level near the 50-2 door and hit Main Engine 2 (ME-2) during Vehicle Assembly Building (VAB) processing operations.

“STS-134 Endeavour ME 2 ELSA Bottle Damage Inspections: Issue: Possible handling damage to ME-2. Background: ELSA Bottle dropped from above ME-2 to heat shield adjacent to controller during VAB processing. Damage observed above and adjacent to engine,” noted the SSME SSP FRR presentation.

“Dent in Orbiter GN2 Line. Dent on edge of Heat Shield near ME-2 controller. Witness statements and damage indicate no engine impact. Assessment conducted around 4.5 Ft assuming possible engine contact.

“Path limited to E2061 in vicinity of LPO Duct and Controller. No visible evidence of engine contact. Normal electrical pad checkouts conducted. Tactile test of controller harness verified connector integrity.

“Harness “wiggle checks” confirmed internal wire integrity. Potential controller housing impact analyzed. Calculated shock loads within typical vibration levels.”

The presentation continued by overviewing the flight rationale which was presented to managers at the SSP FRR.

“Flight Rationale: Engine hardware inspected and no external or internal damage evident. Electrical Harness Backshells visual and tactile manipulation. Protect sensitive internal wire crimps. Harness “wiggle checks” completed with no anomalies. Effective in finding/confirming electrical intermittents. Controller receptacle integrity confirmed by controller internal pressure check.

“Integrity of ducts, lines, etc. confirmed by visual inspections. Pad verified electrical functions and controller pressure. Harness installation precludes adverse loading or pinching of wiring. Conductors protected by at least three layers of insulation. Potential shock loads to controller housing within vibration experience. Critical functions are redundant.”

Once Endeavour returns home from her STS-134 mission, her engines will be removed and stored, potentially for use with the Space Launch System (SLS), should the ongoing RAC teams at the Marshall Space Flight Center (MSFC) continue to baseline a Shuttle Derived (SD) Heavy Lift Launch Vehicle (HLV) as the Design Reference Vehicle (DRV).

It was back in October of last year when a Program Requirements Control Board (PRCB) meeting recommended the orbiters should gain Replica Shuttle Main Engines (RSMEs) – previously scrapped nozzles installed via an adaptor – for when all three of the vehicles retire to exhibitions, thus protecting the flown SSMEs for potential reuse with the opening SLS flights.

NASA’s scheduled to announce the location of all three orbiter’s retirement homes next week.

The FRR presentation also referenced the readiness of six other SSMEs, three of which are installed on Atlantis for her STS-135 mission – a reference which relates to Atlantis also holding the role of the STS-335 Launch On Need (LON) vehicle, in the event of a highly unlikely need of a rescue scenario for Endeavour’s crew.

The other three engines are allocated to the spare set, in the event any or all of Endeavour’s SSMEs require changeout prior to launch.

“STS-135 Engines: ME-1 2047 ME-2 2060 ME-3 2045. Engines installed on Atlantis 7-9 December 2010. Engines reviewed and ready to support contingency if required,” the SSP FRR SSME presentation added. “Spare Engine set: ME-1 2052 ME-2 2051 ME-3 2054. Post-flight processing and checkouts complete. All current flight and ground test anomalies have been evaluated with respect to impact on Flight Engines.”

(Numerous articles will follow. L2 members refer to STS-134 coverage sections for internal coverage, presentations, images and and updates from engineers and managers. Images used: Larry Sullivan MaxQ Entertainment/ and via L2 Presentations).

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