STS-119 mission planning – special Thrust Oscillation test added

by Chris Bergin

Discovery’s STS-119 flight – currently targeting February 2009 – has gained its opening planning documentation, created for the mission that will carry the final truss element to the International Space Station.The expansive mission baseline includes documentation on the deferred Boundary Layer Transition (BLT) experiment that was originally scheduled for STS-126, plus a special Thrust Oscillation test – designed to provide valuable launch vibration data for Ares I.

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Discovery’s STS-119 Mission:

Currently targeting a NET (No Earlier Than) February 12, 2009 launch date, Discovery crew’s primary focus for the mission will be to install the S6 truss segment, the final truss element – and final set of solar arrays – to be added to the Station.

Due to the intense amount of robotics operations in the early phase of the mission, flight planners have deferred EVA-1 from Flight Day 4 to Flight Day 5, according to the 61 page presentation, available on L2. 

‘For planning purposes EVA 1 will be deferred to FD5; TPS (Thermal Protection System) Focused Inspection place holder moves to FD6,’ added the PRCB (Program Requirements Control Board) document.

Additional changes to the mission may also follow as a result of this decision – specifically EVA-4: ‘Action to ISS to confirm content for 4 EVA’s or may delete 4th EVA; decision will have mission duration implications.’

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In addition to these changes, flight planners are also working a possible middeck stowage threat relating to the BMRRM (Bearing Motor Roll Ring Module) payload on ascent.

Placement of this middeck payload on Discovery will eliminate space that was previously to have been used to carry two 5 (full size) MLE bags (equipment bags). To accommodate this payload change, the ISS program is planning to defer the two 5 MLE bags to the STS-128 (ISS-17A) Shuttle mission later in 2009.

Thrust Oscillation DTO:

The Thrust Oscillation Seat DTO is designed to provide the Constellation Program with valuable launch vibration data as refinements to the Ares I launch vehicle and Orion capsule continue.

Thrust Oscillation is a recognized characteristic of solid rocket motors – in Ares I’s case, the five segment first stage – with concerns arising when pressure oscillations drive resonant modes in the vehicle structure, holding the potential to – in the most extreme cases – incapacitate, injure or kill astronauts riding in the vehicle.

Constellation engineers are currently finalizing a mitigation plan for Ares I. However, any additional flight data – noted as a priority requirement in Constellation documentation – will aid understanding on the issue.

‘Constellation Program (CxP) has requested OPO (Orbiter Project Office) to implement a DTO to gather launch vibration data. DTO will be done in conjunction with a DSO to record astronaut visual performance to aid in CxP unimpeded crew performance specification development,’ noted the PRCB document.

To perform this DTO, three Mission Specialist seats will be outfitted with triaxial accelerometers. After recording data during launch, the accelerometers will be removed and stowed during the post-insertion timeline.

Graphics associated with the DTO also appear to show that astronauts will carry out an eye sight test – placed in front of them on the wall of the middeck – during the ride uphill.

‘Astronaut records visual function from middeck locker mounted card and other symptoms during launch profile,’ noted the text byline associated with the graphic.

The Space Shuttle Program (SSP) is currently planning two additional Thrust Oscillation DTOs on STS-127 and STS-128, though the Constellation Program have been quick to send out a memo to disassociate this as a test for Ares, even though it is.

“Removing DTO wording regarding that it’s for Constellation. Will just say that it’s a DTO, what it’s for, who is responsible for funding, and what safety boards the DTO will go through for certification,” noted the memo, pointing to Constellation making sure they don’t have to pay for the tests out of their funding.

Boundary Layer Transition DTO:

Originally scheduled to be conducted on Endeavour’s STS-126 mission later this year, the Boundary Layer Transition DTO (Detailed Test Objective) has been moved to STS-119, due to processing constraints on Endeavour ahead of her unique LON (Launch On Need) support roles for STS-124 and STS-125.

The Boundary Layer Transition DTO will involve the use of “integrated TPS and MADS (Modular Auxiliary Data System) instrumentation (designed) to fly with a fixed protuberance tile with a height of 0.25” to initiate BLT at around Mach 15,” noted the PRCB documentation.

To help mitigate some of the risk associated with this DTO, a total of three TPS tiles downstream of the protuberance will be changed to eliminate the risk of overheating in these areas. In addition to this mitigation effort, thirteen temperature sensors will be installed in surrounding TPS tiles.

“A total of thirteen thermocouples will be installed in TPS tiles: eleven will be in the affected wing area downstream of the transitional cone of influence, one in the protuberance tile, and one as a reference upstream of the protuberance.”

Of the thirteen sensors, ten will be selected for temperature recording during flight. This recording will take place through “the MADS instrumentation system via wiring to a new thermal reference junction (TRJ) in the wing and from there (through) wiring (most existing) to the mid-body MADS shelf,” added the baseline presentation.

In all, 22 tiles and 20 gap fillers will be affected during TPS modifications for this DTO.

Additional Orbiter Hardware Upgrades:

Also making its debut on STS-119 will be an upgrade to the Inertia Reels on the crew’s launch and entry seats.

The new Inertia Reel design (MA-16) is designed to mitigate this risk by providing absolute locking during any differential acceleration of the crewmember and the seat in the forward and backward X, Y, and Z axes.

“Current MA-8 design locks through differential acceleration of the crewmember and the seat in the forward X direction only,” noted the presentation. “During a low onset acceleration event, the Inertia Reel may allow the crewmember to become dislocated from the seatback.”

In addition to the Inertia Reel modification, an upgrade to the End Effector (EE) of the SRMS (Shuttle Remote Manipulator System) is planned for STS-119. The upgrade, which centers on a no-longer-available raybestos material, will see the raybestos brakes/clutches of the EE changed to a ceramic material.

Two other modifications to the EE will be implemented on this flight following issues with the back-up release stall during Discovery’s STS-103 flight to the Hubble Space Telescope in 1999.

The necessary equipment of these upgrades is scheduled to arrive at the Kennedy Space Center (KSC) this summer.

Furthermore, three more upgrades for STS-119 have been approved but not yet baselined.

These upgrades include: “WLE (Wing Leading Edge) Spar “Sneak Flow” Protection (on) Right Hand panels 1-4, Left Hand panels 2-4; Lower WLE CP Horse Collar Gap Filler Redesign (on) RH 1-4, LH 2-4; and Connector Saver Redesign (on) LH OMS Pod and Ku Band (antenna).”

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