NASA managers – following negotiations with their Russian partners – have decided to slip STS-134 to April 29. The slip of STS-134 – Endeavour’s final mission to the International Space Station (ISS) – allows for the Russian Progress M-10M cargo ship to remain on its April 27 launch date. The vehicle will now dock with the ISS on the same day Endeavour is scheduled to launch.
It has been known since last month that a potential conflict between STS-134 and the Progress M-10M was still to be resolved, although it was always believed that Endeavour would hold priority, with the Russians moving their launch date to allow STS-134 to remain on track to open the launch window on April 19.
Going into the negotiations, understood to have taken place on Sunday – after NASA management arrived at the Baikonur Cosmodrome in Kazakhstan for the Soyuz TMA-21 launch – Endeavour’s available launch window ran from April 19 – May 3. However, contained within that window is an April 23-29 cutout (or elimination of launch opportunities for Endeavour) due to the currently-scheduled rotation of Progress unmanned resupply vehicles at the ISS.
Only one line, in a managerial summary memo on March 21 hinted towards the Russians showing a strong preference for their vehicle to remain on schedule, mainly relating to the Progress’ time-sensitive cargo, understood to be a biological experiment which needs to be placed into one of the ISS’ freezers within days of launch.
“Russians have asked for launch slip for STS-134 to deconflict Progress dock/undock,” noted the memo from the Mission Operations Directorate (MOD). Options such as transferring the time-sensitive payload to Endeavour, or a plan to loiter the Progress on orbit should Endeavour’s launch directly conflict, appear to have been unacceptable.
While many people could have assumed a resupply craft would not be able to hold priority over a hugely important shuttle mission, Russian commentators have noted numerous occasions where they have altered their plans for NASA, which is likely to have been the basis for agreeing to provide assistance to Roscosmos this time around.
“The STS-134 launch date is moving from April 19th to April 29th to de-conflict the upcoming vehicle traffic at the Space Station, with the Russian 41 Progress scheduled to undock on 4/26 and the Russian 42 Progress scheduled to launch on 4/27 and dock on 4/29,” noted a memo on the slip, acquired by L2.
Citing the slip will allow additional breathing room in the event Endeavour’s mission requires extra time during her docked mission, the update also noted work is continuing on what is known as Dual Docked Operations (DDO), a constraint of having a docked orbiter on the Station when another vehicle is scheduled to dock or undock.
This DDO work is focusing on the contingency of Endeavour being delayed until a May launch date – in the event of a technical issue, weather, etc. – overlapping with the undocking of one of the Soyuz’s from the ISS
“Launching STS-134 on 4/29 provides a larger launch window and gives us the best opportunity to extend the docked portion of the mission by a day or two if required,” the notes added. “Teams are looking at the possibility of dual docked ops with the Soyuz 25 scheduled to undock on May 16th in case we cannot get off the pad until early May. Early indications are that this will not be an issue.”
Although the 29th is the last day of the cutout on the previously calculated cutout, because the Progress will be docking early in the day, providing all goes to plan, Endeavour would be cleared to launch on the 29th as is now official. Discovery was also counting down on her launch day, with the caveat of waiting for ATV-2 to successfully dock that same day.
As a result of the slip, the Agency Flight Readiness Review (FRR), which sets the official launch date following a highly technical overview of Endeavour and her mission – is also in the process of moving from April 8 to approximately April 19.
The slip may impact on the potential for a Soyuz flyabout of the ISS and Endeavour, due to the new timeline for the docked mission, due to the change in the Russian ground station passes compared to the previous schedule.
Following last week’s severe storm over the Kennedy Space Center (KSC), inspections of the STS-134 stack were completed over the weekend, showing nothing more than minor damage to Endeavour’s External Tank (ET-122). No repair work is expected as a result, although final clearance isn’t expected until Tuesday.
“S0018.100 severe weather walk downs were performed. Engineering is assessing potential damage from the heavy rains, wind, lightning, and reported hail. The lightning indications were outside of the 0.3 nautical miles; therefore, the preliminary assessment showed there is no concern to the vehicle,” noted the NASA Test Director (NTD) report on Monday (L2).
“The ET sustained minor hail damage mainly near the -Y GOX seal footprint and pencil point areas. Orbiter tile completed preliminary walkdowns and have reported no damage to the orbiter. An Engineering Review Board (ERB) will be held Tuesday to evaluate all the findings.”
With the Terminal Countdown Demonstration Test (TCDT) – also known as S0017 operations – successfully completed completed on Friday, engineers are working on four new Interim Problem Reports (IPRs), most of which are related to the dress rehearsal. Most of the IPRs are listed as accidental switch throws and hold no constraint to the flow.
With the weather-related delay to the completion of the TCDT, engineers were aiming to catch up on the pre-scheduled flow, although they now have an additional 10 days due to the launch date slip.
Going into Monday, engineers were preparing for a week highlighted by the Hypergolic fueling of the Solid Rocket Booster (SRB) Hydraulic Power Units (HPU), along with Ordnance Installation tasks. Managers may opt to delay these tasks to realign with the new launch date target.
“IMU (Inertial Measurement Unit) calibration was completed Friday night post-TCDT. S1287 Orbiter Aft Closeouts continue. S0024 HPU hyper load is (was) scheduled to begin this morning (Monday),” added the NTD report.
“Pad A will (was to) be cleared at 0800 EST this morning (Monday). HPU hydrazine loading operations will (was to) begin around 0900 EST. S5009 Ordnance Installation is (was) scheduled to begin tomorrow (Tuesday) afternoon with call to stations at 1400 EST. S07134 AMS End-to-End Test is (was) scheduled for Wednesday.”
(Numerous articles will follow. L2 members refer to STS-134 coverage sections for internal coverage, presentations, images and and updates from engineers and managers. Images used: L2 Presentations and NASA TV).