Description of Driving Event:
Several items of EVA hardware were lost during the EVAs on STS-88. Impact to immediate mission is loss of availability of needed tools. Lost tooling, when unretrieved, also adds to on orbit debris. - The flight support equipment (FSE) for the EVA installable slidewire and an on-orbit installed worksite interface (OIWIF) with an attached retractable tether were lost on EVA1.
- One of the trunnion pin covers was lost on EVA2.
- Two of the safety tether hook guards were also lost during the EVAs.
There is no identified common hardware cause for the lost hardware. The EVA Project Office chartered a team to investigate the issue and make recommendations for corrective action. Root cause: - Slidewire Carrier - inconclusive, most probable cause is inadvertent opening of Tool Stanchion bayonet.
- On orbit installed WIF/retractable tether - inconclusive, most probable cause was the hardware was tethered to another end item and was released when that end item was removed from the mini workstation.
- Trunnion pin cover - was not properly tethered due to a lack of a tether loop on the mockup/trainer.
- Tether hook clips - inadequate restraint in design.
Lesson(s) Learned:
Careful planning from design through training, flight rules, and operations is required to prevent loss of equipment and tooling during space walk operations.
Recommendation(s):
Slidewire carrier - implement an operational constraint to require that items in Tool stanchion and other similar bayonets also be tethered. OIWIF/retractable tether - reemphasize crew training to visually verify hook mate/demate on mini workstation. Trunnion pin cover - update trainer to include tether loop. Tether hook clips - Include integral ring/spring to allow clip to be attached back to itself.
Evidence of Recurrence Control Effectiveness:
All the recommendations were implemented for 2A.1 with no recurrence of loss.
Documents Related to Lesson:
N/A
Mission Directorate(s):
- Exploration Systems
- Space Operations
- Aeronautics Research
Additional Key Phrase(s):
- Extra-Vehicular Activity
- Flight Equipment
- Hardware
- Human Factors
- Policy & Planning
- Risk Management/Assessment
- Safety & Mission Assurance
- Spacecraft
- Training Equipment
Additional Info:
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