Atlantis ready for STS-335 flow following impressive mission performance

by Chris Bergin

After what is becoming more likely to have been her last flight, Atlantis is continuing post roll in operations, as she prepares to head into STS-335 processing in support of STS-134. If STS-132 proves to be Atlantis’ swansong, the post-flight reports from the Mission Management Team (MMT) point to a superb performance during entry and landing, arriving home in near-pristine condition.

STS-132 Re-entry/Landing:

Atlantis arrived back home in Florida with only nine reported issues in the Mission Evaluation Room (MER) – the last relating to the Flash Evaporation System (FES) during deorbit preparations. The FES provides cooling to orbiter systems when the Payload Bay Doors (PLBDs) – which include the radiators used on orbit – are closed.

“The FES in topping mode using the primary B controller shut down near the end of the radiator coldsoak for deorbit prep. The shutdown occurred about 46 minutes into the radiator coldsoak. The crew then restarted the FES topper using the primary B controller,” noted the post flight report to the MMT (L2). This resulted in a shutdown with the FES Freon outlet temperature failing to reach the control band.”

As part of the malfunctions handbook, the crew followed a procedure that has been used a couple of times on recent flights, known as a core flush – which is one solution for ice buildup in the FES. Contingency exists in the system if required.

“Subsequently, the crew restarted the FES using the primary A controller resulting in a successful seven minute operation, via a contingency procedure using a modified radiator bypass/FES checkout with core flush (on secondary controller) followed the primary A activation.

“In this contingency procedure, the FES is operated in secondary high load mode, followed by a core flush, then concluded with secondary topping operation. Ice and excess carryover were observed in the FES topping ducts during the core flush. The core flush stage of the procedure was performed twice because the initial core flush produced duct temperatures that indicated ice had not been completely flushed from the core.

“The second core flush produced duct temperature signatures that indicated a complete flush of the core. After completion of the contingency procedure, the FES configuration was switched to primary A controller in full up mode which prepares the orbiter for deorbit. Entry operations on the FES Pri A controller were nominal.”

STS-132 Specific Articles:

With the FES issue resolved, both PLBDs were closed nominally by 146/03:49:08GMT [11/09:28:59 Mission Elapsed Time (MET)] in preparation for landing. A delayed closed indication on the starboard door has previously occurred several times in the past on multiple vehicles and is a known condition, thus was not a concern for entry.

The deorbit maneuver for the first landing opportunity at KSC, a dual-engine straight-feed firing, was started on orbit 186 at 146/11:41:59.2 GMT (11/17:21:51.2 MET) with shutdown at 146/11:45:05 GMT (11:17:24:57 MET). The burn was 185.6 sec in duration with a delta V of 333.6 ft/sec.

Atlantis’ Fuel Cells and Auxiliary Power Units (APUs) all performed as advertised, after holding a good level of reserve in case of weather related wave offs.

“All APU parameters were nominal on the final day on-orbit (FD13), during entry, and postlanding at KSC. APU 2 was the TIG-5 single APU start, APU 1 and 3 were started at EI-13,” added the MMT overview.

“The fuel cells generated 13.8 kW and 449 amps, average, and 3896 kWh of total electrical energy during the 282.48 hour mission. The fuel cells consumed 337 lb of hydrogen and 2673 lb of oxygen from the PRSD (Power Reactant Storage and Distributation) subsystem. The PRSD system also provided 234 lb of oxygen to the crew. The fuel cells produced 3009 lb of water. Approximately 44 lb of O2 was used for tank-to-tank transfer to ISS.

“The PRSD subsystem could have supported a 75 hour mission extension at the average mission power level of 13.8 kW based on the usable quantities remaining at landing. At an extension day average power level of 12.51 kW, it could have supported an 83 hour mission extension.”

Thanks to a timely gap in the Florida weather, the first landing attempt – mirroring the first launch attempt – was taken, in what was a fitting finale to Atlantis’ successful mission.

Pages of reports on the numerous orbiter systems – used during the transition from a spacecraft to an aircraft – all listed nominal performance, ahead of the wheels touching down on Runway 33 of the Shuttle Landing Facility (SLF).

“STS-132 Landing System performance nominal. MGTD (Main Gear): 146:12:48:08 (loss of WOW indication) NGTD (Nose Gear): 146:12:48:19 (loss of WOW indication) DC (Drag Chute) DEPLOY: 146:12:48:10.5 BRAKES ON: 146/12:48:45 (RHOB first indication over 250 psia),” added the MMT report.

“MLG TD Velocity: 195 KGS Brake Pressure nominal at averaging 400-500 psi throughout rollout, with the max brake pressure reached approximately 684 psi (LHI) DC JETTISON = 146:12:48:47 WHEEL STOP = 146:12:49:26 Total roll out time ~ 1 minute 18 seconds from MGTD Video of MLG tires, all had typical spin-up tire wear exposing tire tread cord.”

According to early Thermal Protection System (TPS) evaluations, Atlantis arrived back in excellent condition, with only a couple of gap fillers and, four missing putty repairs areas and some frayed blankets – which is all nominal, and confirmed the Damage Assessment Team (DAT) confidence in the healthy condition of Atlantis’ heatshield during on orbit inspections.

“Great effort on the flight, both the prep to get the vehicle ready and during the flight,” noted Shuttle manager John Casper on the latest Shuttle Standup/Integration report (L2).

“(Thanks to) the Ground Operations team for all their outstanding work to get Atlantis ready to fly, and now putting back in the OPF (Orbiter Processing Facility).”

Post STS-132/STS-335 Processing:

It takes around a week of operations to safe an orbiter in preparation for their next flow, with Atlantis set to be processed as the STS-335 vehicle in Launch On Need (LON) support of Endeavour’s STS-134 flight – although the final manifest running order is yet to be finalized – not least if STS-135 will be added, and which orbiter will fly the mission, with a June 2011 launch date preferred.

Following landing on the SLF, the Convoy engineers completed Atlantis’ total downgrade at 0953 EDT, ahead of tow operations to OPF-1, which began at 1244 EDT. This marked the start of OPF Roll In Operations.

“S0069 Integrated OPF Roll In operations: The vehicle was spotted in the OPF at 1604 EDT. Fuel cells were powered down at 2224 EDT. Jack & level was completed at 0054 EDT. T-0 and Horizontal drain/control venting is in work,” noted the opening STS-335 notes (L2) from the NASA Test Director (NTD).

“Cryo drain and tank inerting is complete. Orbiter power system validation and PLBD strongback installation (Friday). PLBD functional is scheduled for Tuesday.”

As is usual, Interim Problem Reports (IPRs) tend to include troubleshooting from issues recorded during the mission, with the heater failure on the L3D Reaction Control System (RCS) thruster debuting on the STS-335 flow as IPR 0002, one of four IPRs are listed by the NTD.

“New IPR 0002: Thruster L3D heater failed off. Troubleshooting plan is TBD (To Be Determined). New IPR 0003: SLF personnel reported audible leak at PD-17, LH2 high point bleed QD (Quick Disconnect). MPS (Main Propulsion System) reports leak rate is minimal and does not pose a safety/hazard concern. No action planned while on runway. Plan is to mate QD and perform leak check.

“New IPR 0004: O2 Tank 4 Midbody connection near Door 45 Leak exceeded allowable level. Problem was detected during preps for Cryo drain. It was determined to be a fuzz leak at the QD. It was determined to not be hazardous since the QD only passes GHe. Engineering suspects a possible nose seal issue and will inspect the QD at a later time. No constraint to continue with Cryo drain/inerting.”

Engineers will work on Atlantis on Saturday, prior to a two day break over Memorial Weekend, with only the requirement to establish Orbiter Aft access on the books.

Related Articles