STS-125: Processing for Hubble – Atlantis to be super-modified

by Chris Bergin

Atlantis is beginning her five month OPF (Orbiter Processing Facility) flow, in readiness for the flagship STS-125 mission – her first mission to the space telescope.

The final servicing mission by a shuttle will launch in late August/early September, ahead of which Atlantis can look forward to undergoing a series of unique safety modifications, for what is the only remaining mission to be without the “safe haven” of the International Space Station (ISS).

**The most comprehensive collection of Shuttle, Ares, Orion and ISS related presentations and mission documentation, plus expansive daily processing documentation and updates are available to download on L2 **

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**STS-122 Special: 29 Flight Readiness Review (FRR) Presentations, Baselines and Mission Overviews. **Click here for FRR overview articles: Article 1Article 2** Payload Presentations and vast amounts of live, uploaded images and presentations, movies (several) – already 3900 megabytes strong**

**STS-122 MMT Level now into post flight IFA Reviews.
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STS-125 Processing Preview:

Atlantis is now undergoing post flight deservicing inside OPF-1, ahead of a flow that will involve the removal of her Orbiter Docking System (ODS) – a milestone that will signal her transition to an orbiter ready to pursue Hubble.

As part of her post flight operations, known as ‘S0069 Integrated Roll In Ops’, Atlantis arrived inside the OPF Wednesday afternoon. The orbiter was powered down for the period of hyper deservicing and engineering access.

‘The Orbiter was successfully spotted in OPF-1 on the 1st attempt at 1430L. S0069 Integrated Roll In Ops picked up after the Orbiter was spotted,’ noted processing information on Thursday.

‘RH/LH T-O connections, Fuel Cell power down, jack and level, White Room extension, have been completed. Access to the crew module has been established. Comm. and BFS GPC (General Purpose Computer) deactivation are complete. S0069 operations are on schedule and will continue today. Payload Bay Doors will be opened on Sunday.’

Atlantis’ processing flow will be fascinating to follow, as the orbiter transitions from a module carrying vehicle, to a Hubble servicing ship.

The most obvious signs of that transition will be in the payload bay, as she receives the multitude of components required for SM-4.

Lining up in the payload bay will be the Super Lightweight Interchangeable Carrier (SLIC), Orbiter Replacement Unit Carrier (ORUC), Flight Support System (FSS), and the Multi-Use Logistic Equipment Carrier (MULE).

Hosted on those elements will be the replacement Wide Field Camera 3 for Hubble, along with its new batteries, a Fine Guidance Sensor, and the Spectrograph Rate Sensor Units. Also observed in the payload bay is the IMAX camera, which will take movie footage of the mission.

However, while this payload is unique to Atlantis, it’s the modifications that are to be utilized for increased safety that will gain their debuts with STS-125.

While some of the improvements are awaiting full approval by the Space Shuttle Program (SSP), the list is fascinating by way of using lessons learned from previous flights, in order to increase safety margins. Listed below are just a few of the modifications noted.

Already classed as baselined is ‘Fiducial Markings on Nose Cap RCC’, markings that will appear as a cross on the nose cap of Atlantis. This will enable more accurate and expeditious coordinate location identification for inspection and damage assessment activities.

This is an element associated with the inspections of the vehicle by the Orbiter Boom Sensor System (OBSS) – which will hold more responsibility for checking for any ascent related damage, given the lack of the RPM (Rbar Pitch Maneuver) due to the non-involvement of the ISS on this mission.

‘Implements fiducial markings to facilitate on-orbit imagery X-Y-Z coordinate location to allow for more efficient damage assessment during the mission,’ noted one of the numerous mission baseline presentations.

‘Permanent reference marks will be added using Black Sharpie marker at 14 original Shuttle Entry Air Data System (SEADS) locations on nose cap. Reduces ‘uncertainty’ from ~5” without marks to ~0.5-1.0”.’

Implementation of Protective Window Shields / On-Orbit Installation: This modification – awaiting official approval – will add safety margins in the event of an MMOD (micrometeoroid/orbiting debris) strike on the windows in question – and allows for the potential for damaged shields to be removed on orbit.

‘Implements polycarbonate window protective shields on Orbiter pressure panes (W7, W8, W9 and W10) to reduce possibility of window breakage and accommodate launch and on-orbit removal / installation,’ added the presentation. ‘A thin polycarbonate sheet installed at current shade attachment locations has demonstrated the ability to prevent damage by a factor of six (minimum).

‘The bonded polycarbonate window shields concept was developed in 2006 but it was determined that the Lexan would have a detrimental effect on high aperture photography. A new concept was developed to allow removal and installation of the polycarbonate shields on-orbit

‘A single layer of cloth is attached over the shield with Velcro to act as a shade; rear windows include tethering capabilities. Rear window shields will be installed for launch to protect the windows; Overhead window shields will be installed on-orbit after photographs are taken.

‘Utilizes existing overhead windows 7 and 8 clamps and rear windows 9 and 10 Velcro attachment locations without invalidating the crew module window basis of certification.’

Main Landing Gear Door (MLGD) Thermal Barrier Cavity Protection: This element is due to be certified in April, which – should it be approved – will see the installation of a thermal inhibitor on the barrier, in order to prevent potential failure of the MLGD environmental seal.

‘The current MLGD thermal barrier system has no redundancy and is vulnerable to impact damage which could allow the heat of re-entry into the cavity between the OML and the environmental seal,’ added the presentation.

Interestingly, the reference to ‘vulnerability’ is based on a number of debris strikes to that area of the orbiter. Atlantis’ STS-122 saw no noticeable strikes, and may as a result change this requirement.

However, if approved, the thermal inhibitor – constructed of a rigidized batting material enclosed in a sleeving – would be used to expand to seal the cavity during exposure to excessive heating and protect the environmental seal area from reaching an over-temperature conditions.

‘Arc jet testing demonstrated the ability of the thermal inhibitor to reduce the temperature at the environmental seal for the condition of a breach past the MLGD thermal barrier. All material and system testing performed to-date proved that additional insulation capability is provided by the thermal inhibitor.

‘Thermal inhibitor preliminary development schedule supports implementation on OV-104 for STS-125. Material qualification is scheduled for completion on 2/18/08, with production hardware / certification is expected to be complete on 4/17/08.’

ET Door Uplock Latch Actuator Modification: This calls for the redesign of the existing ET (External Tank) door uplock latch actuators (LH and RH) to reduce the maximum stall torque range.

‘Maximum stall torque of 4,000 to 6,000 in-lbs from the uplock ET door latch actuator could cause uplock mechanism yielding if debris causes a jam in the ET umbilical area during actuator operation.

‘The modified actuator test showed consistent stall torque results within 900 to 1,151 in-lbs under all test conditions, significantly reducing the risk of yielding the uplock mechanism

‘The new design included reducing the spring force on the torque limiter friction disks by reducing the Belleville spring thickness, adding a spacer to fill the gap, and the ball pockets ground for smoother surface and slightly increased depth to improve consistency.’

UPDATE: The ET Door Uplock Latch Actuator Modification will no longer being implemented for the HST flight. Managers have decided to focus attention on implementation of BRI-18 tile around the Main Landing Gear Doors and the ET Doors. To carry out both modifications is not viable for Atlantis’ OPF flow ahead of STS-125.

**CLICK HERE to review our series of articles on STS-125 and STS-400 LON**

Atlantis is currently scheduled to launch on August 28, although this date continues to jump around – from early August to early September – on updated FAWG and Launch Schedule manifests.

The month long delay to STS-124, caused by production issues with ET-128 and the Beta Angle cut out, aren’t expected to cause any issues with STS-125’s schedule, and ET-127 – the tank that will fly with Atlantis – is on schedule at the Michoud Assembly Facility (MAF) in New Orleans.

‘On ET-127, are continuing longeron preps; installed four ice/frost ramp brackets,’ noted recent processing information, adding that the work to ET-128 will not result in a slowdown on the STS-125 tank. ‘Will keep resources working on ET-127.’

As reported previously, the additional factor involved with an on-time launch of STS-125 is Endeavour. Currently on Pad 39A awaiting launch on STS-123, Endeavour is required to be processed in time to be rolled out to Pad 39B, where she will remain as the LON (Launch On Need) vehicle during the launch of Atlantis from Pad 39A.

Once stood down from that requirement, she will be rolled back – partly – down the crawlerway, before being moved on to Pad 39A in preparation for STS-126.

A smooth STS-123 mission thus required to support STS-125, and a full pre-Flight Readiness Review (FRR) preview will be published on this site in the next few days.

L2 members: All documentation – from which the above article has quoted snippets – is available in full in the related L2 sections, updated live.

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