Endeavour home on second landing opportunity

by Chris Bergin

Endeavour’s has returned home from her record breaking STS-123 mission on the second landing opportunity at the Kennedy Space Center (KSC). Endeavour’s night landing was highlighted by APU gases flaming out of her aft.

Refinements and procedures have already been made to Flight Day 17’s opening landing attempts, taking into account various orbiter issues. Landing was at 20:39 EDT.

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 **LIVE news updates on Endeavour STS-123 Flight Day Specific**



Payload Bay Doors closed for entry. Into OPS 3. Refer to live update pages (linked above).

‘Fuel Cell H2O Common pH Transient Indications: At GMT 85/19:04:08 the Fuel Cell Common H2O Line pH indication was received. It cleared after 39 seconds. Six additional transient indications were seen.

‘The 3 individual fuel cell pH sensors did not indicate high, which exonerates KOH in the system, and the performance of all three fuel cells continues to be nominal.

‘The crew completed a FC H2O pH test and reported a pH of 4.5 which was more acidic that the expected neutral 7.’

STS-124 delayed to at least NET (No Earlier Than) May 29.

STS-123 Re-entry Preps:

Tuesday’s preparations saw the successful testing of critical re-entry and landing systems on Endeavour, with RCS (Reaction Control System) and FCS (Flight Control Surfaces) checkouts.

‘Endeavour’s mission continues to proceed according to plan. All systems are operating nominally. Flight Control System (FCS) check out and Reaction Control System (RCS) hot fire test was successfully completed yesterday,’ noted Wednesday MMT (Mission Management Team) information. 

‘Landing is scheduled for 1905 EDT with a second opportunity at 2039 EDT. OPF-2 is ready to accept the orbiter,’ added an MMT overview of the run to deorbit.

‘Orbit Adjust (4 fps posigrade) after post sleep (FD16) – Brings in second KSC deorbit opportunity (crossrange) on EOM+2. Sets up daylight conditions for 1st KSC opportunity on EOM. Relative motion with ATV (Automated Transfer Vehicle) not a concern.’

‘5 of 6 Vernier operations during FCS checkout – L5L will fail leak and auto deselect at OPS transition. Reapply GMEM in OPS 2 after FCS Checkout complete. Will evaluate if implementation desired after weather waive-off.’

This will also be the second 3-String Global Positioning System (GPS) re-entry, with GPS incorporated into PASS navigation prior to the deorbit burn (MM301) and after high-speed C-band radar tracking evaluation. BFS navigation will be managed with state vector transfers from the PASS.

This will be the final flight of GPS ‘ramp-up’ operations before 3-string GPS fully operational on STS-126.

‘3-string GPS Checkout: At end of FCS checkout, transition to OPS 3 and incorporate 3- string GPS into navigation for around 10 minutes. Integrated procedures for OPS 3 GPS checkout & L5L GMEM operations ready in Flight Note 22687A,’ added the MMT presentation.

**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 an astronaut held camcorder video – to post landing – several more videos showing landing from 90,000 ft also available and HUD videos from STA landings. Includes HALO II Re-entry video, and re-entry videos from Gemini and Apollo (converted from 8mm)**

Endeavour’s Auxiliary Power Unit (APU 1) pressure decay also proved to be no issue during checkout on FD16, and continues to confirm it has a GN2 (gaseous nitrogen) leak – which holds no issues for landing, versus a hydrazine leak – which is a fire risk during landing.

‘APU 1 used for FCS Checkout – APU 1 Fuel Tank pressure decrease still indicative of GN2 leak. Contingency operations: If hydrazine, run APU 1 to depletion (up to 55 min depending on leak rate). GN2, completed FCS checkout, leak rate supports.

“Landing Convoy personnel will be briefed on the APU1 fuel tank pressure decay. Additional assessments and safety precautions are in place to insure personnel safety in the event of residual hydrazine in the aft. Procedures are similar to those put in place for landing of STS-121.”

RCS Hotfire operations also underwent a nominal set of checkout procedures, despite a card failure early into the mission that affected three jets.

“Nominal RCS Hotfire procedures: All primary RCS jets fired, including L2L, L2U, L2D jets that lost leak RM at lift-off. Same DSC OL1 Card 1 failure that failed leak RM on vernier L5L. Flight Rule A6-156 {RCS RM Loss Mgmt} allows hot fire of primary thruster without Fail Leak RM to satisfy turnaround requirement. Propellant available for two pulses.”

Two landing attempts will made on Wednesday, both at KSC. Should weather become a problem on both attempts, Thursday will open up Edwards Air Force Base in California for EOM+1 (End Of Mission). Endeavour can happily remain in space until Friday.

“Planned EOM is Wednesday, March 26. Consumables support deorbit opportunities through EOM+2 (Friday, March 28). LiOH supports EOM+2 and is the limiting consumable. Supply Water supports 6 opportunities over 3 days. Delaying Rad Bypass/FES checkout could gain 1 additional opportunity,” added the MMT presentation.

“Prop (OMS/RCS) supports at least 2-2-2-2 deorbit opportunities. Margins: around 25 lbs FRCS, around 570 lbs OMS/ARCS (above 2-2-2-2). Cryo supports at least 4-4-4-4 deorbit opportunities. Group B powerdown nominally planned for waive-off days. N2 supports well beyond EOM+4

“Given consumables, orbiter systems status, and weather, plan is to attempt only KSC on EOM. EOM+1 will attempt KSC and EDW (pick-em day). Assess wx forecast after EOM waive-off to determine if NOR (White Sands) call-up is required. Landing Strategy is as follows: Rev 248: KSC. Rev 249: KSC.”

Flight Day 17’s preparations have already been preceded by the stowing of the KU antenna. Go for Payload Bay Door closure will be decided at 15:13 EDT, ahead of the deorbit burn (17:48 EDT) for the opening landing opportunity. Procedures will occur 90 minutes later if controllers decide on the second landing attempt on the following Rev.

The procedures ahead of the burn have already been refined, taking into account various orbiter status – including the failed A String on the Flash Evaporator System (FES).

“APU Start Plan: TIG-5 APU Start Sequence: If attempt 2, start APU 2 then APU 3. If attempt 1, start APU 2. 3-String GPS Operations: Take GPS in Ops 301 during Deorbit Prep and Inhibit about 45 min prior to deorbit burn. After ground tracking confirmation, take GPS to PASS. Manage BFS Navigation with state vector transfers.

“L2L Yaw Jet: Last priority and Deselected for loss of RM: Flight Rule A6-156, (RCS RM Loss Mgmt) requires this action. Flight control system certified to operate with 2 of 4 yaw jets/side.

“FES Pri A not available: No deltas required for Rad/Bypass FES C/O in deorbit prep. Nominal entry configuration with FES Pri B, Hi Load enabled.”

The mission has been a huge success during its docked phase, with Endeavour departing the ISS with only one new issue – which was only a failed backlight – epitomizing how well the multi-billion dollar vehicle has performed on this long duration mission.

“MER-15 Aft Panel A4 MET/GMT Timer Not Illuminated,” noted JSC’s Mission Evaluation Room (MER). “No mission impact.”

Praise has already been sent from JAXA, who saw the successful opening installation mission for their Japanese Experiment Module (JEM) “Kibo”.

“Program manager Mr. Hasegawa expressed gratitude for the mission,” noted the minutes from a Station MMT meeting. “This is a very wonderful and successful situation which has had high visibility with the Japanese public. We look forward to the continuation of this successful partnership.”

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