STS-133: Healthy Discovery completes FD2 inspections on RCC panels

by Chris Bergin

Now safely on orbit, Discovery has completed inspections on her Reinforced Carbon Carbon (RCC) panels – the main task of STS-133’s Flight Day 2 (FD 2). Only two minor indications were registered by her sensor equipment embedded into her Wing Leading Edge (WLE) during ascent, while two noticeable debris events are of no concern from a damage standpoint.

Discovery On Orbit:

Flight Day 2’s main events were related to the inspection of parts of Discovery’s TPS (Thermal Protection System) and OMS (Orbital Maneuvering System) pod surveys via the OBSS (Orbiter Boom Sensor System).

EMU (EVA Suit) checkout and Centerline camera installation, along with ODS (Orbiter Docking System) ring extension and Rendezvous tools checkout, were also undertaken, as the crew prepare to arrive at the International Space Station (ISS) on Saturday.

Two course correction burns – known as NC2 and NC3 burns – are also part of Flight Day 2’s requirements, as Discovery continues to close in on the International Space Station (ISS) for docking on Flight Day 3.

Discovery and her crew successfully launched Thursday afternoon at 1653 EST. MECO occurred at 1701 EST. The go for on-orbit operations was given at 1830 EST,” summarized the NASA Test Director (NTD) report (L2). “Flight Day 1 Activities Completed: Payload Bay Door opening and KU band deployment. Flight Days 2 Activities Scheduled: OBSS TPS inspection. EMU checkout.”

All ascent milestones were reached nominally during Discovery’s ride uphill, which will be outlined in-depth via the expansive Mission Evaluation Room (MER) Ascent Report (L2) in a forthcoming article.

“The STS-133 mission was launched at 055/21:53:24.016 Greenwich Mean Time (GMT),” noted a quick summary report (L2). “The Reusable Solid Rocket Booster (RSRB) separation was visible. A nominal Orbital Maneuvering System (OMS) assist maneuver was performed following RSRB separation. Ignition occurred at 055/21:55:41.4 GMT [00/00:02:17 Mission Elapsed Time (MET)], and the maneuver was 152.50 sec in duration.”

“MECO occurred at 055/22:01:48 GMT (00/00:08:24 MET). The ET separated from the Orbiter at 055/22:02:09 GMT (00/00:08:45 MET). The open indication for both of the fill and drain valves for the Main Propulsion System (MPS) were received; however, the inboard valve open indication was lost for 10 seconds after which it returned. Analysis of this drain valve indication is in work.

“A nominal OMS-2 maneuver was performed at 055/22:31:54.2 GMT (00/00:38:30 MET). The maneuver was 63.4 sec in duration with a differential velocity of 96.5 ft/sec. The achieved orbit was 85.0 by 125.0 nmi. The payload bay doors were opened at 055/23:29:30 GMT (00/01:36:06 MET). The Ku-Band antenna was deployed and the self-test was completed with satisfactory results.”

STS-133 News Articles (over 110 articles):

The inboard drain valve indication “MPS (Main Propulsion System) LO2 Inboard Fill & Drain Valve Open Position Indication 10 second Dropout” is one of what is only two “funnies” listed by the MER, with no other “MER Items” of interest – pointing to a superb early performance by Discovery on her swansong mission.

FD2 Inspection Tasks:

The handheld photography and ET Umbilical Well imagery is already being collated on ground for the Damage Assessment Team (DAT), as they begin their evaluations into any foam liberation events. Two events were noted on ET cam video – both of which occurred well after the time of ascent where aerodynamic forces still exist to cause the debris to hit the orbiter with any noticeable velocity.

“Foam Loss/Strikes: At about 230 seconds, multiple pieces of ET TPS released from the area of the ET Intertank LH2 flange between the bipod struts.

The debris impacts the Orbiter but based on initial analysis of the ET feedline downlink video no tile damage is noted,” noted the initial assessment of the liberation events (L2).

“At about 282 seconds, debris originates near the aft of the ET inboard of LO2 Feedline and appears to impact the Orbiter. Again, based on initial analysis of the ET feedline downlink video no tile damage is noted.”

The DAT are also looking at sensor information, following data from the Wing Leading Edge Impact Detection System (WLEIDS), which picked up two minor indications at T+106 and T+115 seconds on the starboard RCC panels 8 and 10.

The highest of the two indications – at T+115 seconds – is documented as 1.8 GMRS, which is very minor. It is understood that indications of 10+ GMRS are only capable of causing any noticeable impact on the WLE panels.

Also, given the system is so sensitive, the indications recorded by the system have to go through a screening process via engineers on the ground, so as to ensure such indications are specific items of ascent interest, as opposed to ascent noise or vibrations from the Space Shuttle Main Engines (SSMEs) firing.

With the NC2 and NC3 Rendezvous burns planned into the flight day, the main role for the crew was the unberthing of the OBSS via the RMS (Remote Manipulator System), in order to carry out surveys of Discovery’s wing and nose cap, before heading to the OMS Pods to check for any tile damage or protruding blankets.

“TPS Surveys: All RCC (Reinforced Carbon Carbon) is inspected during the OBSS Starboard Wing, Nose Cap, and Port Wing surveys. The two wing surveys also cover most of the areas of the crew cabin. The OMS Pod is inspected using a handheld camera to take pictures from the aft flight deck windows,” noted Flight Readiness Review (FRR) mission outline documentation (L2).

The OBSS survey procedures incorporate the use of supplemental IDC (Digital Camera) images during LDRI (Laser Dynamic Range Imager) scans, thus reducing the likelihood of needing Focused Inspection. The OBSS unberth procedure incorporates the LDRI 3D calibration and the starboard survey the flat field calibration.

Three crewmembers are required continuously during the surveys, two for the SRMS/OBSS ops and one to operate the situational awareness cameras and sensors. Only two crewmembers are required during unberthing and berthing operations (non-laser ops).

Scans of the entire starboard wing are scheduled first, given they are not easily performed, or are impossible to perform while docked – providing a challenge should a docked late inspection be required. The surveys are scheduled to continue through the night passes, but the crew may elect to pause if the night time visuals are not sufficient.

“The LDRI survey attitude requires no sun within a +/-20 degree field of view (FOV) of the laser bore-sight. Additionally, no sun can be within a 10 degree half-cone directly behind the instrument; however it is highly desired to keep the sun at a 90 degree half cone behind the instrument as long as it’s not directly behind,” added the FRR overview.

Although Flight Day 3’s RPM (Rbar Pitch Maneuver) – carried out “underneath” the ISS ahead of docking – will provide a near-complete overview of Discovery’s heatshield, the OBSS inspections will give the opening insights into the extent of any damage sustained during the ride uphill, as much as it is unlikely Discovery has any damage.

A level of review is already been undertaken by engineers on the ground, who are able to review ground-based camera and radar footage relating to debris events.

(Numerous articles will follow. L2 members refer to STS-133 live coverage sections for internal coverage, presentations, images and and updates from engineers and managers – which is now into full Flight Day coverage during the mission. Images used, Launch: MaxQ Entertainment/ Rest via L2 documentation).

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