Endeavour tracking KSC return on Friday – TPS cleared for entry

by Chris Bergin

STS-127 is coming to the end of another highly successful mission for the shuttle program, as the crew prepare for one of two attempts to land at the Kennedy Space Center (KSC) on Friday – following the clearance of the vehicle’s Thermal Control System (TPS). With LiOH consumables limiting to a Sunday return deadline, Saturday would likely see all three US landing sites being open for Endeavour.

STS-127 Latest:

End Of Mission minus one day (EOM-1) involved the checkout of Endeavour’s systems for her return to Earth, including the Reaction Control System (RCS) jets and aerosurfaces.

The Flight Control Surfaces (FCS) checkout is a vital element of ensuring Endeavour can conduct the DAP (Digital Auto Pilot) stage of re-entry – as she changes from a spaceship into an aircraft.

The RCS will also be involved for the first part of re-entry, helping Endeavour control her attitude and positioning before and after deorbit burn, and also through entry-interface.

“FCS Checkout & Deorbit/Entry Operations: Nominal FCS Checkout. APU 1 (Auxiliary Power Unit) will be used for aerosurface drive and secondary actuator check. RCS Hotfire will invoke 2 pulse technique (based on propellant margins),” noted the Mission Management Team (MMT) plan.

One RCS thruster behaved off-nominally during the checkout – specifically F2F – although that holds no mission impact, as it is not used during re-entry.

The vehicle was – as expected – cleared for re-entry at the MMT, following the DAT (Damage Assessment Team) evaluations into the imagery gained from the Late Inspections. A few Regions Of Interest (ROIs) were noted, but that is to be expected.

Endeavour will target two attempts on Friday – both for her home base of the Kennedy Space Center. Friday looks hopeful on the weather front, and even better on Saturday, raising hopes she will not require a ferry ride home from California, unlike her older sister at the conclusion of STS-125.

“The weather forecasts for EOM, +1 and +2 was briefed. We have a decent shot at KSC on Friday and an even slightly better shot on Saturday. EDW (Edwards Air Force Base) and NOR (White Sands) forecasts are solid GO’s for all three days,” noted the MMT meeting notes on L2.

Consumables – as always – determine how long Endeavour can stay on orbit, in the event of landing wave offs. Currently, the deadline is Sunday, due to LiOH limitations related to CO2 removal. Sunday will be reserved as a technical wave off day, in the event problems with Endeavour force the crew to stay in space for an additional day.

“In addition, the MMT heard the Entry briefing. LiOH is the limiting consumable with only EOM+2 capability. Cryo margins are about 16 hrs above 16+2. Prop, N2 and water margins exceed +3 days. Only KSC will be called up on Friday, and all three sites will be called up on Sat since that will be our pick’em day,” noted the latest MMT presentation, available on L2.

“Planned EOM is Friday, July 31. Consumables support through EOM+2 (Sunday, August 3). LiOH supports EOM+2 and is the limiting consumable.

“Supply Water supports 7 opportunities over 4 days. Cryo can support 15 hours over EOM+2. OMS/RCS margin over 3-3-3 is: 100 lbs FRCS, 460 lbs ARCS, 980 lbs OMS. Group B powerdown nominally planned for wave-off days. N2 supports well beyond EOM+3.”

D2Once again, cameras will keep an eye on the four radiator retract hoses, during Payload Bay Door closure on Friday. This was called for following incidents with a couple of flights that suffered from kinks in the hoses, as seen during post flight processing, and in the pad flow ahead of launch.

“Nominal Deorbit/Entry operations: Deorbit Prep procedures will capture video of 4 radiator hoses during payload bay door closing,” added the MMT presentation.

“Edwards Permanent runway ready to support on EOM+1. Lakebed status: EDW 15/33 green. Northrup lakebed: green.”

Discovery STS-128 Latest:

Meanwhile, Discovery’s STS-128 launch date has slipped to NET (No Earlier Than) August 26, as the stack waits to leave the Vehicle Assembly Building (VAB) next week.

Mission Management Team (MMT) manager Leroy Cain noted the launch date will be “around” August 25, but a good idea of the real target will depend on when Discovery rolls out to 39A.

Discovery is now hard mated to her External Tank (ET-132) as part of S0004 Orbiter/ET mate operations.

“S0004 Orbiter/ET mate continues: Crew Module hatch functional was successfully completed. LO2 and LH2 umbilical ordnance installation, stud tensioning, and exterior closeouts are complete. LO2/LH2 Monoball installations and mates are in work,” noted processing information on L2.

This operation found a problem with the monoball electrical mate connections, which will require a repair.

“During LH2 monoball electrical mates connector 50P523 was found to have galled extension threads,” added processing information on Thursday. “Will probably have to demate the connector for repairs and then remate. Engineering is evaluating.”

Thursday involves the Shuttle Interface Test being carried out on the stack, while the STS-128 payload is scheduled to make its journey out to Pad 39A tonight. Discovery herself is set to move to the pad on August 3, for a 23 day pad flow prior to launch.

“The team continues to work toward payload move to Pad-A tonight; first motion is planned for 2000L. Payload Canister lift operations are scheduled to begin early (3rd shift) tomorrow. SSV (Space Shuttle Vehicle) rollout from the VAB to Pad-A remains planned for August 3. Terminal Countdown Demonstration Test is now scheduled for August 6-7.”

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