Discovery on track as STS-119 heads into Agency FRR

by Chris Gebhardt

NASA senior managers will meet on Tuesday for the Space Operations Mission Directorate (SOMD) “Agency” Flight Readiness Review (FRR) which, among other things, will officially set the mission’s launch date.

With only a limited amount of time remaining before launch, the STS-119 Certification of Flight Readiness (CoFR) Requirements/Endorsements chart show a nearly green board, with all categories excect two ready to support launch.

The two exceptions to this green status are the resolution of Flight Anomalies and the Critical Items List Hazards from STS-126. These two yellow categories – which denote non-standard open work with expected resolution prior to flight – refer mainly the installation and testing of three good gaseous hydrogen Flow Control Valves (FCVs) into Discovery and flight rationale for the FCV issue which is expected at the SOMD FRR.

Monday processing information notes the valves have been installed and are undergoing testing out at Pad 39A.

Meanwhile, a Mission Operations Directorate (MOD) FRR presentation from the Flight Director’s office has thoroughly reviewed a number of aspects associated with Discovery’s mission, including special ascent/entry topics, carbon dioxide measurement procedures during docked operations, the Waste Hygiene Compartment (WHC) on the ISS, and other ISS specific requirements.

Ascent/Entry Topics:

The first accent/entry topic discussed in the MOD Flight Director’s FRR presentation, available for download on L2, is the Boundary Layer Transition (BLT) Detailed Test Objective (DTO).

“DTO will attempt to 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 FRR presentation.

The DTO will attempt to trip the boundary layer at Mach 15 by use of a 0.25 inch tall, 4 inch long, and 0.3 inch thick protuberance on one of Discovery’s Thermal Protection System (TPS) tiles.

The data from this experiment will be recorded real time by several thermocouples installed underneath TPS tiles located downstream of the protuberance.

As always, before this DTO was approved by shuttle managers, an extensive review was conducted to ensure that the DTO would not affect the performance of the Orbiter during reentry and that the protuberance tile was placed in an area that would minimize the occurrence of damage to the protuberance tile by ascent debris.

As part of this analysis, it was determined that roll reversals – a necessary procedure during reentry to ensure that the Orbiter bleeds off the proper amount of energy for landing and aligns properly with Heading Alignment Circle at the landing field – be minimized after the trip of the boundary layer.

To this end, Discovery’s orbital trajectory will be adjusted post-undocking by a series of course trajectory burns to set up a reentry profile to KSC that minimizes the number of roll reversals after the boundary layer transition.

Of course, the complete elimination of roll reversals after the BLT may not be possible based on Discovery’s mission objectives and the timing of certain critical events; however, an effort will be made to adhere to this specific roll reversal rule as well as possible.

Another ascent/entry topic discussed in the Flight Director’s update pertained to the lighting conditions during Discovery’s launch windows. With sunrise just after 7am on February 12, the first two days of Discovery’s launch window will be classed as daytime launches.

NASA flight rules state that a shuttle launch is considered a daytime launch if T0 occurs between sunrise -15mins or sunset +15mins.

Continually, Discovery’s launch window will allow for daylight Orbiter umbilical photography of the External Tank (ET) through February 17 and ET handheld photography by the Flight Crew through February 21.

The presentation further notes that ET umbilical camera flash is available for all launch days that result in nighttime Orbiter umbilical photography of the ET.

Furthermore, the presentation emphasizes that on days when the ISS plane allows for both Flight Day-3 (FD-3) and FD-4 rendezvous options, the launch window can be extended at the discretion of the Launch Director to capitalize on this opportunity.

The next issue discussed in the FRR presentation pertains to a concern for potential cracking of the sMIA (Serial Multiplexer Interface Adaptor) diode.

“sMIA diodes on primary ports on FF4 & FA4 deemed ‘suspect’ by Orbiter Project,” notes the presentation. “Manufacturing defect found in lots 7715 & 7535.

A cracked wave-forming diode has been identified as the root cause for the GPC (General Purpose Computer) split that occurred during Discovery’s STS-124 pad processing campaign in May 2008.

“KSC will preemptively port mode string four during S0007 pre-launch count to avoid the ‘suspect’ diodes on the primary ports.”

As a further precaution, STS-119 will be flown entirely on the secondary ports even though the primary ports are not considered ‘failed’ by either pre-launch Launch Commit Criteria (LCC) or on-orbit operations standpoints.

Another new LCC that will debut on STS-119 is the verification of functionality of two O2 systems prior to launch.

The MOD FRR presentation states that “LCC encompasses functionality check made by EECOM (Electrical, Environmental, Consumables) with ‘Good Visor Flow’ call at L-2:00 minutes.”

Moreover, as reported by this site after STS-126, Edwards Air Force Base has transitioned back to its permanent runway. Shuttle Training Aircraft verification and Federal Aviation Authority verification of the Microwave Scanning Beam Landing System have been completed and I-loads are in a good configuration to support STS-119.

The wind towers have also be moved back to the primary runway at Edwards.

Yet another change debuting on STS-119 is a realignment of the High Pressure Fuel Turbopump Intra-channel qualification limit.

To account for hardware verification effects, the allowable intra-channel discharge temperature limit has been increased to 130 degrees R from 100 degrees R.

A further ascent/entry discussion in the Flight Director’s update relates to an Ascent Vibration DTO to support the Constellation program’s launch oscillation assessments.

For this DTO, accelerometers will be placed on the back of the MS1 (Mission Specialist 1), MS3, and MS5 seats.

*Click here for articles on Ares I Thrust Oscillation*

As part of the DTO, all middeck crewmembers will perform a cue card visual assessment to determine what can and cannot be read on the cue cards because of launch vibrations.

To accomplish this portion of the DTO, full middeck lighting will have to be provided to the crew during ascent.

Lastly, the final ascent/entry modification discussed by the MOD FRR is a new downlink parameter for the Space Shuttle Main Engines.

“OI-32 introduced new downlink parameters so pushbutton contact dilemmas can be detected in OPS-9,” notes the Flight Director’s update presentation.

The new modification for the OI-33 operating software will allow the launch team to constantly monitor pushbutton contacts until T-31secs for “2 of 2 pushbutton contacts failed ‘on.'” The previous OI-32 technique did not allow for continuous monitoring of the pushbutton contacts.

Weather, Carbon Dioxide, and ISS Activities:

As with all space vehicles, the weather is a primary consideration for launch operations. For STS-119, an improved French radar system will allow the rain shower rule to be applied to the Istres, France Transoceanic Abort Landing (TAL) site.

This TAL rain shower rule states that a launch may be allowed to occur even if the current observed TAL weather is “no go” but sufficient information is present to indicate that acceptable conditions will be present at the landing field at the time of a TAL landing.

All software changes to support this upgrade were completed on January 23 and MIDDS (Meteorological Information Data Distribution System) is ready to support STS-119.

Conversely, the automated weather stations at both Spanish TAL sites – Moron and Zaragoza – are not transmitting data.

The FRR presentation states that troubleshooting will begin once mission personnel arrive on site in the coming days.

Meanwhile, continuing an investigation that began during STS-123 in March 2008, the Environmental Control (EC) division has requested further testing and analysis of a new ISS/Orbiter stack ventilation configuration to reduce Carbon Dioxide (CO2) levels throughout the integrated complex.

During STS-123, the flight crew reported CO2 symptoms in Endeavour.

To mitigate this condition, a ventilation configuration change was introduced during STS-124 in June 2008 and continued on STS-126 in November. As a result of this change, neither flight crew reported CO2 symptoms.

For STS-119, the formation of a tiger team was proposed to further assess this issue; however, due to insufficient time, the tiger team formation was denied. Instead, a detailed CO2 survey will be performed by an ISS crewmember during STS-119.

This survey will involve an identical complex ventilation configuration as was seen during STS-124 and STS-126 and an ISS crewmember taking CO2 measurements in the Orbiter and every ISS module at mid-day and again during pre-sleep activities.

These readings will help supply insight into the modified ventilation configuration and “help EC strategize on how to further assess system performance without risking crew comfort and crew performance,” notes the Flight Director’s update.

Additionally, the International Space Station Program (ISSP) has requested – or would like – the STS-119 crew to perform the Waste Hygiene Compartment (WHC) high load (six crew) requirement test as specified by the Increment Definition and Requirement Document (IDRD).

Furthermore, there is a requirement for “Flight 15A (STS-119) …to demonstrate ability to go without Orbiter liquid waste dumps in preparation for 2J/A,” notes the MOD presentation.

Both of these requirements can be met by performing the high load checkout of the WHC for two days.

This plan would see six STS-119 crew members using the WHC on the ISS on FD-9 and FD-11. However, this test is at risk because of on-going problems with Urine Processor Assembly.

“If Urine Processor Assembly (UPA) inoperative during 15A, cannot perform WHC high load checkout without using limited supply of expendable containers,” notes the FRR presentation.

If the UPA cannot be fixed prior to Discovery’s undocking, the final opportunity to perform the high load test will be during the Expedition 18/19 handover activity period in late March/early April before the planned expansion of the ISS crew to six people in May.

As a result, the MOD can support the removal and replacement (R&R) of the UPA on STS-119 if deemed necessary. While a final decision has not yet been made to fly the spare DA component for the UPA on STS-119, both the ISS and Space Shuttle Programs are protecting for this possibility.

A final decision on whether or not to R&R the DA will be made sometime next week after the results of further on-orbit troubleshooting are analyzed by ground engineers.

If the decision is made to R&R the DA, both Expedition 18 Commander Mike Fincke and Flight Engineer Sandra Magnus are trained to perform the R&R with minimal impact STS-119 Crit 1 and 2 activities.

A further refinement of ISS activities for STS-119 pertains to the maneuvering of the ISS into the proper docking attitude.

The Operations Manager (OM) has proposed adjusting the ISS timeline for STS-119 FD-3. This adjustment would delay the maneuvering of the ISS into the Shuttle docking attitude to allow for an additional two and a half hours of solar array Autotrack.

This operation would provide additional power generation for the high beta angle docking of Discovery. Furthermore, it would reduce the planned power down operations and reduce the risk to science on the ISS during Discovery’s docked period.

Even with this modified timeline, the ISS would still be in the proper docking attitude prior to Discovery’s arrival on the Rbar for her Rbar Pitch Maneuver (RPM).

This proposal has since been approved based on simulation runs that identified no operational issues with the modified timeline.

Furthermore, highlighting the MOD’s review of every possible scenario for STS-119 is their analysis of possible robotics failures during the maneuvering operations of the S6 truss element.

“Robotic failures during maneuvers to S6 install could lead to inability for ISS to sustain Docking Loads,” notes the FRR presentation.

The presentation details a zero-fault tolerance during Shuttle Remote Manipulator System (SRMS) maneuvering of the S6 truss to its handoff position to the Space Station Remote Manipulator System (SSRMS).

“SRMS is 0FT to achieving S6 handback position. SSRMS has capability to grapple S6 given any SRMS joint failure and allow the shuttle to depart,” notes the presentation.

However, if the SRMS joint failure is severe enough to either warrant termination of the mission or prevent the safe installation of S6 to the S5 truss element, the ISS could be unable to withstand subsequent docking loads if S6 is not structurally attached to the station.

Two of the issues that could prevent the safe installation of S6 in the event of an SRMS joint failure are “robotic clearance issues” and “minimal verification that resolution optics are viable.”

Basically, the SRMS would not be able to provide a clear visual record that all clearance measurements by the SSRMS to Station structure are within safety limits.

Therefore, should a SRMS joint failure occur, Mission Control would have to determine whether the S6 truss could be safely installed, placed in a safe configuration to support subsequent docking loads, or returned to Discovery’s Payload Bay for return to earth.

Final flight rules to address any decisions required for S6 install following an SRMS joint failure were developed prior to January 26.

Finally, the presentation notes that all Orbit 2 and Planning Teams are in place to support STS-119 based on its expected mission duration.

At the time of the MOD FRR on January 16, all final flight-specific certifications were expected to be completed by January 30.

L2 members: All documentation – from which the above article has quoted snippets – is available in full in the related L2 sections, now over 4000 gbs in size.

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