The launch dates for the last two scheduled flights of the shuttle remain in flux, as managers assess the modification timeline for Discovery’s Multi-Purpose Logistics Module (MPLM) payload, and the delivery date for Endeavour’s Alpha Magnetic Spectrometer (AMS). Major scheduling challenges with STS-134 may result in the flight slipping as far as Spring, 2011.
With STS-132 still on track to achieve a May 14 launch date target, mission planners are currently working out how to align STS-133 and STS-134, even after swapping the mission order to allow Endeavour to fly later in the year, following the delay to the arrival of the AMS.
“With the recent decision by the Alpha Magnetic Spectrometer (AMS) program to change out its magnet, it’s clear the STS-134/ULF-6/AMS launch currently targeted at the end of July is no longer viable,” noted a manifest planning memo (L2).
“The Space Shuttle Program and International Space Station Program met with Space Operations Mission Directorate Senior Management to discuss manifest options. From that discussion, the following is what we know that will influence our manifest planning and decisions:
“We now will plan to fly STS-133/ULF-5 before STS-134/ULF-6/AMS. With STS-134 moving after STS-133, STS-133/Discovery now becomes the Launch-On-Need (LON) vehicle for the STS-132/ULF-4 mission that is targeted for a May 14, 2010 launch. We will hold STS-133/ULF-5 on its current target date of September 16, 2010.”
STS-133’s Leonardo is undergoing modifications to become a Permanent Multi-Purpose Module (PMM) – allowing it to remain docked on the International Space Station (ISS) following Discovery’s departure.
However, Boeing contractors note hardware that is to be installed on to Leonardo – such as meteoroid shields (MMOD) and several internal elements – are still being constructed, and are yet to be shipped to the Kennedy Space Center for integration.
It is understood that engineers have run out of contingency time in the flow to make September 16, placing the launch date at risk of slipping.
“Challenges with the modifications of Leonardo (MPLM) into the Permanent Multi-Purpose Module (PMM) for its stay on the International Space Station (ISS) have planed the September 16 launch date at risk,” noted information.
“Because Leonardo, the Multi-Purpose Logistics Module (MPLM) that will be modified to become the Permanent Multi-Purpose Module (PMM), was launched on STS-131 later than originally planned, achieving the September 16, 2010 target launch date is at risk.
“Additionally, a couple of much needed Orbital Replacement Units (ORUs) scheduled to be manifested on the PMM are slightly behind delivery schedule.”
STS-133 Specific Articles: http://www.nasaspaceflight.com/tag/sts-133/
No changes will be made to Discovery’s current NET (No Earlier Than) launch date until Atlantis returns from her STS-132 mission, providing Atlantis remains on track to launch in the middle of this month. This is related to STS-133 now being STS-132’s Launch On Need (LON) rescue vehicle.
“We will continue to process Discovery to support a September 16, 2010 launch date to support the LON capability for STS-132 until we determine that the need for crew rescue is no longer needed,” the outline continued. “At that time, most likely post-STS-132 landing, we will assess the STS-133/ULF-5 schedule and update its target launch date.
“Although not anticipated, if STS-132 slips out of the May window, we will most likely assess the STS-133/ULF-5 target launch date then rather than waiting until after LON release. Our current assessment of Contingency Shuttle Crew Support (CSCS) on ISS for STS-132 is in excess of 125 days, which allows STS-133 to serve as LON.”
The challenge of STS-134:
Currently slipped to a November slot in the manifest, STS-134 is only tracking an assumed launch date based on estimations for AMS hardware changes to be completed. It was hoped a more refined target would be available at the end of last week, though this was not forthcoming due to the complex work that is being planed on AMS.
“AMS program management has stated they will be ready to ship to KSC for payload processing in preparation for STS-134/ULF-6/AMS in late August 2010,” noted the overview. “This delivery date will support a launch of STS-134 in the mid-November 2010 time-frame.
“We need to let AMS work through its magnet change-out activity and see how that progresses before establishing a target launch date for STS-134.”
However, any slippage past November – which is currently deemed “likely” – would throw the launch date into a game of schedule dodgeball, as planners take into account a range of constraints – including beta angle cutouts and other vehicles visiting the orbital outpost.
“Launch planning for STS-134 will not be easy and there are challenges to work around. Beginning in early November 2010, there is a series of operational plans that will constrain launch availability,” the overview explained. “There is a beta angle cut-out for launch that begins on November 7, 2010 and ends on November 23, 2010, which means we cannot launch during that time.
STS-134 Specific Articles: http://www.nasaspaceflight.com/tag/sts-134/
“With the planned undocking of Soyuz 23 on November 26, we drop to three crew members on ISS until the arrival of Soyuz 25 on December 12. This will reduce our ability to perform all the tasks necessary during a docked Shuttle mission below that which could be accomplished with a six-person crew. We are assessing this impact to determine our ability to successfully complete the STS-134 mission during this time.
Workarounds for Dual Docked Operations (DDO) are still being worked, although they remain a constraint for at least STS-132. A potential solution to another issue – known as YERO (Year End Roll-Over) – is available, although managerial notes continue to class the problem of having an orbiter in space during a change of year as a hard constraint.
“From December 15, 2010 through January 1, 2011, we would not launch STS-134 because it would have Discovery on orbit during the year-end roll-over, which we have determined not to be advisable to do. The flight software is not designed to accommodate the change in year from one to the next while in flight,” listed the constraints for STS-134 in the event of a slip towards the end of 2010.
“ESA’s ATV-2 (Automated Transfer Vehicle #2) has a target docking date of December 17, 2010. January 4 through January 20, 2011 we experience another beta angle cut-out period for launch.
“January 27 is the targeted docking date for the JAXA HTV-2 (H-II Transfer Vehicle #2). It is targeted to remain docked through February 24, 2011. HTV-2 would block the Shuttle cargo bay unless transfer to a different berthing location.”
As such, managers need a firm delivery date for AMS in order to determine a viable launch window for Endeavour, which means the mission will likely remain in flux until the summer. It could also result in the mission being delayed to as far as Spring 2011.
“Bottom line is we need to evaluate all constraints, some of which could move, others, like beta-angle cut-outs, are set. We will continue to evaluate these constraints and will determine a target launch date for STS-134 at a later date.
“For now, it will be no earlier than November TBD (To Be Determined), 2010 on Endeavour.”