STS-119: NASA assess contingency launch dates up to March 17
Several options, including a reduced mission duration with only one EVA, are being considered as a contingency to ensuring STS-119 launches in March – prior to the Soyuz cut out. Dependant on gaining flight rationale for Discovery’s Flow Control Valves (FCVs), the effort would add options to avoiding a downstream delay to STS-125’s mission to the Hubble Space Telescope, which would not be able to launch on schedule, if STS-119 slips into April.
The contingency evaluation – which includes a March 17 launch option for a short docked mission that includes just one EVA – is being carried out by Mission Operations Directorate (MOD), lead by Kwatsi Alibaruho of the Flight Director Office.
Last week Mr Alibaruho tasked his team with ensuring they will be able to support a March 12 launch – the current NET (No Earlier Than) date. However, with the key meetings on assessing the ability to make that launch date taking place this week, MOD need to look at the potential of launching up to March 17, but within the restrictions of the Soyuz launch cut out.
“As successful Shuttle launches depend on a number of factors, our experience dictates that we must consider how we’d posture ourselves such that we have more than one day of capability to attempt a launch,” noted Mr Alibaruho in a memo attached to a presentation outlining the options, both available on L2.
“Normally, that’s not overly challenging; however, in this situation, we have a scheduling constraint that potentially drives decisions that we have not often had to confront. The Soyuz 18S, carrying the Expedition 19 crew, is set to launch on March 26, 2009.”
The launch of the Soyuz, which works on a fixed timeline due to the limited on-orbit lifetime of the Russian vehicle, equates to a need for Discovery to depart from the International Space Station (ISS) no later than March 25.
Such a timeline would technically allow Discovery to add a few additional dates on to the end of the launch window, but only by reducing the docked stage of the mission.
“Per our currently accepted Ground rules and Constraints, the Shuttle needs to be undocked from the ISS prior to the launch of the Soyuz. Thus, whatever mission we fly in March under the banner of STS-119 / ISS-15A needs to conclude its business on ISS No Later Than March 25, 2009,” added Mr Alibaruho.
“With that as a constraint, ISS Program Manager, Mike Suffredini, asked us assess mission content for all available launch days.
“To assist us, our ISS and Shuttle Planning Teams and our Flight Dynamics experts have provided us data to turn around a very rapid high level assessment of what our mission might look like for March launches subsequent to 3/12/09. We sent (the assessments) to the Shuttle and Station Program Management after some internal peer and management review.”
Those assessments, shown in the associated presentation with flight plan outlines for the March 16/17 options, open with the initial nominal mission timeline, which would conclude the docked mission on Flight Day 13. Such a timeline is allowable for launches on March 12 and March 13.
The contingency assessments show the docked phase mission timelines being reduced in increments, with a March 14 launch reducing the timeline by one docked day, resulting in the loss of one of the four planned EVAs, for both a Flight Day 3 and Flight Day 4 rendezvous with the Station.
A March 15 launch would result in undocking on Flight Day 11, still includes three EVAs, but with the loss of crew off duty time making up for the shorter docked phase of the timeline.
Options for a March 16 and March 17 launch call for an undocking on Flight Day 10 and Flight Day 9 respectively, for a mission that would be reduced to just one EVA.
How these options would play out during the mission lack detail at this stage of the evaluation, pending the activation of additional options for STS-119’s launch window as a result of the upcoming meetings on the status of FCV flight rationale.
“The assessment is high level and captures many of the critical elements in play for March launch dates that respect the Soyuz cut out,” added Mr Alibaruho. “The devil, of course, is always in the details, most of which are not represented in this assessment.
“At this time, we’d like the teams to take a look at this data and start thinking about some specific elements of your systems constraints and timelined activities on this mission that might need to be addressed in more detail if some of the ‘alternate’ timelines become a reality.”
In the assessment presentation, several notes are added, some of which are based around the original Flight Readiness Review (FRR) documentation – created prior to the FCV-driven delay – which give an element of scope, based on priority and secondary mission objectives, notably work on the troublesome water recycling hardware that was delivered on STS-126.
Click here for NASASpaceflight.com articles on the FCV issue since STS-126.
“All trajectory information assumes NO additional ISS reboost or orbit adjustment between now (2/27/09 EST) and STS launch,” noted the presentation. “Launching on KSC local March 12th or 13th results in nominal mission duration and content.
“All timeline options include Focused Inspection as a requirement since this is the worst case scenario. All timeline options preserve the UPA (Urine Processing Assembly) DA (Distillation Assembly) R&R and associated requirements: Actual R&R. 5 Minute Dry Spin of the new DA. 1 Full urine Processing Cycle.
“Must preserve a full Non-EVA/Non-Robotics Day to accomplish UPA DA objectives due to spatial conflict between UPA rack and RWS (Robotic Work Station).”
Should the option of a one EVA mission be taken, the EVA would work on the priority of Discovery’s payload, the installation of the Integrated Truss Segment (S6) and its fourth set of solar arrays and batteries.
The main reason for an assessment – that could see the mission reduced to several priority items only – is to protect STS-125’s May launch date.
Both Atlantis and her STS-400 support from Endeavour are on track to support the current May 12 launch NET (No Earlier Than) date. However, a mid April launch of STS-119 would mean STS-125’s mission would have to slip at least two weeks, if not more, due to the required turnaround time of both launch assets and the conclusion of post flight IFA (In Flight Anomaly) reviews.
With downstream missions already pushing the schedule further to the right, options to launch STS-119 ahead of the Soyuz cut out may prove to be the best path forward. The most desirable option would be for the upcoming meetings, concluding with the Delta FRR at the end of the week, to approve a March 12 launch date.
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.