As STS-128 tracks an August 24 launch date – pending final clearance of the Ice Frost Ramp foam liberation concern – the Space Shuttle Program Flight Readiness Review (SSP FRR) has conducted thorough review of Discovery’s mission/payload content and launch opportunities.
The 37th voyage of Shuttle Discovery will be the Shuttle Program’s 30th mission dedicated to construction of the International Space Station (ISS).
The 13+1+2 day mission – including eight full docked days of operations between Discovery and the ISS – will involve three scheduled campout EVAs (Spacewalks) from the Station’s Quest Airlock as well as the transfer of several thousand pounds of equipment (totaling about 130-hours of transfer time) from the MPLM Leonardo and Discovery’s middeck.
For launch pad operations, the Launch Team will have 181-hours (7.5-days) of pad hold time based on the limiting liquid oxygen Fuel Cell commodity.
Nevertheless, the largest unanswered question at this point is when Discovery/STS-128 will make its opening launch attempt, with Monday, August 24 the earliest possible launch date at present.
However, the current issue with an Ice Frost Ramp on the Liquid Oxygen portion of Discovery’s External Tank is of more concern for Program and Agency managers than the selection of a launch date for Discovery.
If Flight Rationale is accepted at next week’s agency-level Space Operations Mission Directorate (SOMD) FRR, Discovery would then be cleared for launch the following week.
Assuming the earliest launch date from documentation, a launch on Sunday, August 23 would occur at 2:24:17A.M. for a FD-3 (Flight Day 3) rendezvous with the ISS.
With a realigned launch window now extending through to August 28, the launch opportunities for Discovery are as follows: Monday, August 24 at 1:58:35 A.M., August 25 at 1:36:03 A.M., August 26 at 1:10:21 A.M., August 27 at 12:47:49 A.M., August 28 at 12:17:07 A.M., August 28 at 11:54:35P.M.
The window was set to be longer, but is currently classed as restricted from the 29th by the Eastern Range.
The Mission Operations document from the SSP FRR – available for download on L2 – further notes that for certain days of the launch window, small phase angle limitations may create cutouts at the preferred in-plane launch time.
As a result, for days when the phase angles prevent an in-plane launch the launch team will have to decide whether to attempt launch before or after the cutout.
Once at the ISS, each EVA is scheduled to last six and one half hours, including one unscheduled EVA which could be performed late in the mission if cryo consumables allow.
While at the Station, Discovery will transfer 67lbs of nitrogen and 450lbs of cryo to the ISS.
Also gaining special note in SSP FRR documentation is the fact that this is the last ISS crew rotation flight for the Space Shuttle – with Nicole Stott replacing Tim Kopra.
However, the main aspect of the mission is the installation and transfer of cargo from the MPLM Leonardo and the Lightweight Mission Peculiar Equipment Support Structure (MPESS) Carrier (LMC).
For launch, the MPESS LMC will carry an Ammonia Tank Assembly (ATA) to the ISS. For reentry and landing, the MPESS LMC will return a spent ATA and the EuTEF (European Technology Exposure Facility) to Earth.
Additionally, the MISSE (Materials on International Space Station Experiment) 6A and 6B packages will be returned to Earth in the sidewall carriers on the Payload Bay.
Finally, Discovery’s payload will be rounded out by the TriDAR Automated Rendezvous & Docking Sensor detailed test objective which will benefit Orion and future spaceflight technology.
Mission Objective Priorities and Options:
As with all Shuttle missions, STS-128’s mission objectives have been divided into categories based on their necessity to the STS-128 mission and subsequent stage operations of the ISS.
For STS-128, the Category I Objectives include berthing the MPLM to the ISS, transferring “mandatory quantities” of water from Discovery to the ISS, and rotating Nicole Stott with Tim Kopra on the ISS.
Additional CAT I activities include the transfer of the Node 3 Air Revitalization System rack, transfer of the Treadmill-2 rack, transfer and installation of the ISS MPLM racks, the return of the used P1 truss ATA to the LMC, the return of the MPLM to Discovery, and the transfer of the EuTEF from Columbus to the LMC.
These CAT I activities are the necessary aspects of Discovery’s mission that must be completed during the mission.
As such, the SSP FRR mission overview document states that for a Minimum Duration Flight, completion of the CAT I objectives would be accomplished as soon as possible and the mission shortened 11 Flight Days with only two of the three scheduled EVAs.
A Minimum Duration Flight can be invoked by the Mission Management Team for a variety of reasons and would not necessarily be a result of a problem with Discovery’s systems.
A Minimum Duration Flight could be invoked because of an approaching storm system (i.e. a Hurricane) to Houston, Texas – a which point the protection and safety of the NASA workforce at the Johnson Space Center would take precedent over the full completion of Discovery’s on-orbit mission.
In addition to these CAT I requirements, the SSP FRR notes three CAT II objectives. These include performing a minimum crew handover of two hours per rotating ISS crewmember, transferring the MISSE 6A and 6B experiments from Columbus to the sidewall carriers in Discovery’s Payload Bay, and transferring the remaining cargo items per flight 17A TPL.
Furthermore, performing HTV preparation tasks, SSRMS (Station Arm) triple walk-off, charge of the BSA/REBA batteries, resize of EMU (Extravehicular Mobility Unit), removal and replacement of the S0 truss RGA, and the S3 Upper Outboard PAS deployment are among a long list of items classed as CAT III objectives.
Finally, a series of EVA get-ahead tasks comprise the CAT IV objectives. Some of these include the removal of Node 1 slidewire, installation of Node 1 MMOD (Micro-Meteoroid Orbital Debris) shields, and deployment of the S3 Nadir Outboard PAS.
A complete list of the CAT III and CAT IV objectives can be found in the Mission Operations portion of the SSP FRR documentation on L2.
Other items of interest in the Mission Operations presentation include information on the OBSS (Orbiter Boom Sensor System) Focused Inspection procedures for this mission.
“Various areas of Starboard RCC and Starboard Wing Belly tiles cannot be imaged due to clearance and sensor capabilities,” notes the FRR presentation. “Focused Inspection execution will be attempted the evening of FD4 if procedures can be quickly developed and crew has adequate time to review.”
However, this is not a certainty. As a result, mission planners have determined that installation of the MPLM will be delayed one day to FD-5 to accommodate any necessary vehicle inspections that would otherwise be impossible with the MPLM berthed to the ISS.
“Due to possible impacts to Mission Timeline, Focused Inspection requirements that are located in the MPLM installed/inaccessible area, must be delivered to the Flight Control Team ASAP — no later than the end of FD3 (prior to crew sleep).”
If this scenario plays out, the +1 day would be added to the mission to ensure that all MPLM transfer objectives are accomplished without violating crew off-duty and rest requirements.
Furthermore, the Mission Operations FRR presentation notes that the +1 day will also be used in the event of a launch that results in a FD-4 rendezvous. This will be done to ensure a nominal mission timeline for all activities.
The +1 day could also be added to the mission for a Contingency EVA in the event that all CAT I objectives are not accomplished in the first three spacewalks or if CAT II activities inside the Shuttle/Station complex are not completed before the scheduled undocking.
The final note on possible mission extension states that “If consumables cannot support the nominal mission duration, consideration will be given to extending docked time as long as possible to complete CAT I objectives while protecting mandatory post undocking activities.”
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.