Endeavour in outstanding shape – Docks with ISS

by Chris Bergin

In another historic milestone for Endeavour’s final flight, the fleet’s youngest orbiter chased down the International Space Station (ISS) to kick start the docked phase of the STS-134 mission. Endeavour arrived in superb shape, with the Mission Management Team (MMT) only having to review a handful of very minor issues, following an extremely clean ascent to orbit.

STS-134 Latest:

Endeavour is into Flight Day 3, following what is being described as a superb ascent performance from the main shuttle propulsion elements, as she rode uphill towards a nominal MECO (Main Engine Cut Off) on Monday.

“The STS-134 mission was launched at 136/12:56:27.994 GMT on May 16. A nominal Orbital Maneuvering System (OMS) assist maneuver was performed following SRB separation. Ignition occurred at 136/12:58:42 GMT [00/00:02:14 Mission Elapsed Time (MET)], and the maneuver was 164.24 sec in duration,” noted a Mission Evaluation Report Ascent summary report (L2).

Only two items of interest – both minor – were charged against Endeavour’s ascent, both of which resolved by the time the MER had a chance to report them.

“At 6 min 11 sec MET, the Space Shuttle Main Engine (SSME) -1 Low Pressure Fuel Turbopump (LPFTP) pressure Channel B instrumentation experienced a data drop-out for 0.1 sec. This caused the SSME controller to post a Failure Identifier (FID) and disqualify that measurement,” added the Ascent summary report (a specific article, based on the expansive MER ascent report will follow later in the mission).

“The SSME uses this transducer for the Liquid Hydrogen (LH2) flow-rate calculation on the center engine. It continued to use the Channel A pressure for that calculation. The FID did not affect any other SSME operation. This transducer is not used after Main Engine Cutoff (MECO). MECO occurred at 136/13:04:49 GMT (00/00:08:21MET).”

The other issue – the Vernier R5D Chamber Pressure Tube Slow Pressure Decay – was observed when the R5D chamber pressure failed to drop to vacuum as expected during ascent, indicating a possible blockage in thruster or PC sense tube. However, upon first firing of R5D, the response was nominal with normal Pc response.

At time of publishing, the MER had only listed five issues, ranging from a data transmission issue on the Right Nose Landing Gear (NLG) transducer to the Forward Event Timer error, which has since been resolved. MER presentations on the issues – available in L2’s expansive STS-134 mission coverage sections – show all the issues are very minor and hold no mission impact.

STS-134 Specific Articles: http://www.nasaspaceflight.com/tag/sts-134/

Endeavour’s TPS:

Following the separation of Endeavour’s External Tank (ET-122) – listed at 136/13:05:10 GMT (00/00:08:42 MET) – photography from the orbiter’s umbilical well, along with handheld photography, was downlinked to the Damage Assessment Team (DAT) in Houston.

The high quality imagery (bulk dump in L2) provided post-ascent data on the state of what is known as the “Katrina Tank” – due to its return to the launch manifest after damage sustained during the hurricane of 2005 was repaired. The imagery shows the tank performed like a champ.

Only five minor foam liberations have been tracked back to observations on the separated tank, with small mass foam losses seen in areas such as the Ice Frost Ramps (IFRs), a remarkable achievement given ET-122 did not receive the full set of Return To Flight (RTF) modifications during its fabrication at the Michoud Assembly Facility (MAF) in New Orleans.

As noted by Mission Management Team (MMT) chair LeRoy Cain, the tank “exceeded expectations by quite a bit,” based on the routine pre-launch risk assessments.

With the payload bay doors opened at 136/14:26:29 GMT (00/01:30:01 MET), and the Ku-Band antenna deployed, along with a self-test being completed with satisfactory results, the crew also carried out a survey of the exposed cargo bay and OMS Pods.

The checks on the Pods allow for early observations of protruding gap fillers, cracked tiles or torn stitching on the blankets. The latter issue required a special EVA repair during Atlantis’ STS-117 mission, which resulted in ground processing mitigation procedures being put into place.

As with all recent flights, the imagery shows the OMS Pods are in excellent condition, with no items of interest being noted by the DAT engineers at this time.

It’ll be a few more days before the DAT can inform the MMT Endeavour is cleared from any further inspections, via what is known as a Focused Inspection (FI), as ascent data, crew photography and the imagery gathered from the main focus of Flight Day 2 – the inspections using the Orbiter Boom Sensor System (OBSS) – are fully reviewed on the ground.

So far, FD2’s scans have raised no flags with the DAT engineers, as they reported their latest findings to the MMT late in the flight day.

“Review of FD2 scans is continuing – no reportable damage,” noted the DAT status on the MMT presentation for Flight Day 2 (L2). “Port and Starboard T0 Inspection complete. OMS Pods complete – both LE and acreage with no blanket/gap filler protrusions or reportable tile damages.”

Only one mark on one RCC panel was noted, which was a “nature related” observation, pre-launch.

With the OBSS scans focusing on the Port and Starboard Reinforced Carbon Carbon (RCC), Nose cap and Thermal Protection System (TPS) in the path of the pre-defined map of Endeavour’s Heatshield, the only DAT note of interest related to the partial coverage of Starboard regions 2-4.

However, that data will be refined via the Flight Day 3, as Endeavour was put through a series of burns, highlighted by the Terminal Initiation burn (TI) at 2:37am Central, to begin final approach to the ISS. The TI burn, which makes final course adjustments to the orbiter’s approach to the ISS, placed Endeavour and her crew on the proper heading to reach a point 600-feet “below” the Space Station along the R-bar.

Once on the R-bar, Mission Control gave Endeavour’s crew the go ahead to perform the 360-degree R-bar Pitch Maneuver, or RPM, at 4:14am Central – to allow the flight crew aboard the International Space Station to conduct a photographic survey of the orbiter’s TPS, including her belly.

When the always-stunning maneuver was completed, Endeavour was commanded to perform the TORVO (Twice Orbital Rate V-bar Approach) maneuver to take her from the R-bar to the V-bar (Velocity bar) directly in front of the Space Station’s line of travel.

Once properly aligned within the docking cone, Endeavour’s thrusters were pulsed to reduce the orbiter’s speed by two-tenths of a foot per second, effectively slowing the vehicle and allowing the ISS to “catch up” with the visiting spacecraft.

Following docking, timed at 5:14am Central, hard seal was confirmed and air leak checks performed between Endeavour’s Orbiter Docking System (ODS) and the Pressurized Mating Adaptor (PMA). This was followed by the crew of Endeavour ingressing the ISS for the traditional crew greeting.

A safety briefing with the newly arrived crew was conducted, as Flight Day 3 movedtowards the next milestone, involving robotics and Endeavour’s ELC-3 payload. This operation was successfully completed.

Further updates will follow, with this article being updated during the key events.

(All images via L2. Extensive coverage is being provided on the news site, forum and L2 special sections – the latter of which is the world’s best front row seat to Shuttle missions. With specific and extensive flight day coverage, from interactive “one stop” FD live coverage in the open forum, to internal documentation, photos, videos and content in the specific L2 FD areas).

Related Articles