 |
Testing out tools for repair of STIS
Credit: Nasa |
Neither STIS nor ACS are particularly space-repair friendly, and developing a strategy to fix them presented engineers with many challenges. Planners needed answers to three main questions in order to accommodate the repairs in the mission schedule:
- How to access circuit boards hidden behind panels, requiring the removal of over 100 screws;
- What new tools would be needed to make it easier for astronauts to complete the tasks;
- How to quickly seal the instruments when finished without compromising requirements.
Knowing exactly what needs fixing is not enough to make repairs straightforward. To access the failed circuit boards on these two instruments, astronauts have to remove 111 screws from the cover of STIS, and 32 screws from ACS, a lengthy process in an environment where time is a scarce commodity.
To overcome this challenge, Goddard engineers developed a high-speed power screwdriver with low torque, or twisting force. This combination of operational abilities means that the drill will speed up the removal process without breaking the screws or fasteners.
Hubble’s instruments are extremely delicate and any floating debris poses a real threat to exposed electronics. So, as astronauts open Hubble’s outer shell to make their repairs, they must exercise extreme caution.
To avoid floating debris, NASA engineers designed the fastener capture plate. Using the custom drill, astronauts will first remove four outer screws to install the transparent capture plate over the electronic access panel. Tiny, labelled holes in the plate will allow them to then insert the drill bit and remove screws as the capture plate contains them. At the end, the entire capture plate is released as one unit, safely taking the access panel and all the debris away from Hubble.
The second challenge is grasping the circuit boards. These are very thin, but the astronauts' suits, including their gloves, are bulky and pressurised. If you were to put on a pair of thick, woollen mittens before trying to grab a single piece of paper from the middle of a stack, you might have some idea of how difficult and time-consuming the task is for astronauts. NASA engineers got around this issue by developing a special card extraction tool that allows the astronauts to easily grab and remove the circuit boards.
The last major challenge of the repair process involves closing the instruments. To conserve time, engineers designed a simplified version of the access panels. Two lever-like latches will be all it takes for the astronauts to securely lock the new STIS cover into place. A new panel is not required for ACS because the fresh electronic cards are in a single box that easily slides into place and covers the open side of the instrument.
| 
