STS-135: KSC realign schedule targets for a preliminary July 12 launch

by Chris Bergin

Kennedy Space Center (KSC) engineering teams have realigned processing targets for STS-135 to point towards a July 12 launch date. The preliminary target is dependant on numerous – and upcoming – factors, not least the need for Endeavour to launch on her re-planned May 16 date, but also a nominal pad turnaround and a smooth pre-launch flow for Atlantis herself.

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Atlantis now finds herself patiently sat on the Orbiter Transporter System (OTS) waiting to roll over to the Vehicle Assembly Building (VAB) for mating operations. However, that wait will last until at least next Wednesday, following the realigned schedules relating to Endeavour’s latest launch date target.

De-conflicting milestones between the two orbiters has resulted in a fluid schedule for STS-135, although Atlantis is currently expecting to begin her final short trip to the VAB with two day’s worth of separation from her younger sister’s final ride into space.

“OV-104 (OPF Bay 1): Final landing gear retract was completed on Monday. Hydraulic hose demates and securing and 1660 box disconnect and stow is complete. This marks the last planned OTS mate for the program,” noted the latest processing report (L2) from the NASA Test Director (NTD). “Rollover to the VAB is under review; targeting NET (No Earlier Than) 5/18. (Moved up to the 17th despite the NET.”

Internal schedules are continuing to be realigned, to the point that July 4 was periodically targeted as Atlantis’ latest launch date, prior to the latest assessment being produced – based on Endeavour launching on May 16 – via what is known as the Ops Forecast.

Based on Tuesday’s updated Ops Forecast schedule, STS-135 will enter S0007 Launch Countdown operations on July 9, ahead of a launch date target of July 12.

However, while these schedules are consistently accurate, further realignments can occur within the Space Shuttle Program (SSP), usually based on potential conflicts such as events scheduled on the International Space Station (ISS).

For now, STS-135 is only being classed as aiming for sometime in the second week of July, according to Mission Management Team (MMT) chairman and Space Shuttle Launch Integration manager Mike Moses on Monday.

“We’re not going to be able to tell you a launch date for STS-135,” noted Mr Moses at the presser to update the status of STS-134. “Every time we have a plan, something else comes up. We do know we’re going to have to slip the launch, and we’re going to slip a few weeks to early July, but I’m really hesitate to say (a date) as every time we look at a schedule something else changes and makes us rebalance it.”

Mr Moses also noted that the pre-pad flow plan is also subject to de-conflicting efforts, given Atlantis’ stay inside the VAB has to avoid a rollout to the pad date which threatens to be at the same time Endeavour is due to land.

“So we’re going to wait until we have Endeavour up on orbit and out of the way, we’ll look at the damage to the pad and see what needs doing to turn it around, and then we’ll set a hard and fast launch date for STS-135,” Mr Moses added, with a key reference to the condition of the launch pad after Endeavour blasts off.

Some damage is usually suffered by areas of the pad structure and the flame trench, understandable after being hit by seven million pounds of thrust at T-0.

However, no serious pad damage events have been observed since the infamous STS-124 launch when thousands of Apollo-era bricks were blown out of the flame trench, with some of the debris confirmed as rising above the zero level of the Mobile Launch Platform (MLP).

A major investigation was launched into the event, while a large repair effort was carried out on the flame trench walls, which included embedded instrumentation being added to monitor the stresses on the trench.

A similar – if highly unlikely event – during STS-134’s launch would delay the current plan of a 14 day pad turnaround, providing an example of how a launch date is always very much in the balance until late in the pad flow.

“Planning to rollout STS-135 to Pad approximately 14 days after STS-134 launch,” noted KSC Ground Operations (L2).

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Ground Operations also noted the External Tank (ET-138) and twin Solid Rocket Boosters (SRBs) are in the final stages of preparations to welcome the orbiter, with the NTD report adding the current status of the stack located in High Bay 1 (HB-1).

“Booster and ET/SRB integrated closeouts continue. SRB ordnance preps continue with installation planned for Thursday.”

Also noted on the latest Shuttle Standup/Integration Report (L2) is the delivery status of Atlantis’ Flow Control Valves (FCVs), with the third of three now at KSC and a fourth – spare – valve expected to arrive in Florida from the Californian fabricator this week.

“For OV-104/STS-135, the third FCV was delivered. Vacco is working to deliver a spare, so there will be a fourth as a backup early,” United Space Alliance (USA) Logistics added.

The reference to the Flow Control Valves – at the time STS-134’s troubleshooting is coming to a close – is coincidental, albeit interesting, given the mitigation of the poppets on the valves potentially cracking, firing debris into the internal Main Propulsion System (MPS) plumbing of the orbiters resulted in a much larger investigation than the failure in Endeavour Aft Load Controller Assembly (ALCA-2).

The highly successful mitigation effort has resulted in no further concerns with the valves, and provides useful context in the ability of the Shuttle teams to solve problems with the highly complex orbiter systems.

(Images: KSC NASA, L2 Documentation. Further updates on STS-135’s status will be provided as information arrives, driven by L2’s new STS-135 Special Section.)

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