At last week’s Space Shuttle Program (SSP) FRR, program managers discussed a wide range of topics, including Weather Satellite limitations, the Boundary Layer Transition DTO (Detailed Test Objective), several new operations that will be a part of STS-128 – including Discovery’s debut of new flight software – as well as previous flight performance of the MPLM (Multi-Purpose Logistics Module) on STS-126.
Weather and Boundary Layer Transition:
One of the first notes pertaining to new procedures for STS-128 in the Mission Operations Directorate’s (MOD’s) Mission Procedures presentation to the FRR related to the Continental United States (CONUS) weather satellite system.
“GOES-12 (East) will not be available due to eclipse power-outage,” notes the presentation.
Caused because the GOES-12 satellite will be in Earth shadow, the presentation notes that the satellite will be unavailable between 12:15 A.M. through 1:45 A.M. EDT from August 23rd through 28th.
Given that this period of time covers the extent of Discovery’s launch window – although the 23rd has been all but ruled out due to processing timelines – the Space Flight Meteorology Group has indicated that the GOES-11 (West) satellite is capable of providing a “non-optimal” oblique view of the Kennedy Space Center during the eclipse times for GOES-12.
The next item of interest to gain attention by the MOD is the Boundary Layer Transition DTO Discovery will conduct during her re-entry at the end of the mission.
“Second flight of DTO will gather data during entry regarding the aerothermal effects caused by the boundary layer transitioning from laminar flow to turbulent flow at a high Mach number,” notes the Mission Operations presentation.
This DTO was first performed on Discovery’s previous flight (STS-119). However, there are several changes to the DTO for its second flight.
For the second Boundary Layer Transition DTO, the protuberance height on a modified Thermal Protection System (TPS) tile on the underside of Discovery has been increased to 0.35 inches – enabling the Boundary Layer to be tripped at Mach 18.
Furthermore, based on post-flight analysis from STS-119, a temperature-sensitive coating has been applied to two TPS tiles located downstream of the protuberance, the thermocouples have been relocated, and one downstream tile has been replaced with one that has a higher heat load capacity.
Debuting on Discovery for STS-128 is the OI-34 (Operational Increment number 34) software.
“Enhancements made to Backup Flight Software Heads Up Display to make performance more similar to PASS HUD,” notes the Mission Operations FRR presentation.
Additional enhancements made possible by the OI-34 software include a Bodyflap warning message on the HUD, enhanced runway overlays using “landing site table data for correct length,” HUD high g limit warnings, and deceleration command restoration.
The remaining changes implemented include “memory efficiencies, minor DR fixes, removal of unused code, and documentation-only CRs.”
The previous software upgrade – OI-33 – included safety modifications for engine out scenarios, External Tank separation during a RTLS (Return To Landing Site) abort, and the orbiter’s ability to return to Earth unmanned.
Discovery will also debut the O2 crossover Valve Position indication as a result of a failure seen on STS-126 last year.
“MO10W wiring modification provides position indication for system 1 & 2 crossover valves and simplifies pre-launch and on-orbit troubleshooting.”
The final Launch Commit Criteria modifications for this new wiring configuration were approved by the PRCB (Program Requirements Control Board) at the Noon Board on June 23, 2009.
Also noted in the Mission Operations presentation under the “new procedures” category is the Ammonia Tank Assembly removal and replacement (R&R) on the P1 truss.
“NH3 vent planned for FD2. ATA will be isolated from EATCS loop and on-orbit tests confirm the EATCS loop can function without the ATA,” notes the FRR presentation.
Venting of NH3 is required for this operation in order to reduce the pressure in the ATA tank to the Quick Disconnect line. The venting will prevent over-pressurization in the lines that can be caused by thermal changes. It will also reduce the risk of a leak – which is classed as a “catastrophic hazard/flammability risk in PLB.”
The presentation also notes that if the venting operation should fail, “one tank isolation valve will be opened to reduce over-pressurization.”
Also, the vent can be performed manually during an EVA (Spacewalk) if required.
Previous Mission Anomalies:
The main issues/anomaly gaining note from the MOD relate to the previous MPLM flight – STS-126.
Before STS-126, the ISS Program and ASI telemetry representatives removed the MPLM off-nominal condition values in an effort to save S-band bandwidth. However, they did not properly communicate the removal with ASI flight control team.
As a result, “MPLM Telemetry Parameters were noted as off-nominal and were unavailable in the ISS S-band stream during the STS-126 mission for the ASI (Agenzia Spaziale Italiana) flight control team.”
In response to this anomaly, NASA and ASI agreed to provide Caution and Warning “events” to the ASI flight control team for the three remaining Shuttle MPLM flights – the first of which is STS-128.
This will be accomplished by “placing a camera on the Caution and Warning display and displaying it in the MPLM area.”
In all, the MOD is ready to support STS-128 pending the completion of all standard and non-standard open work.
L2 members: Documentation – from which the above article has quoted snippets – is available in full in the related L2 sections, now over 4000 gbs in size.