Maintaining Equipment in Space

The Software Technology Branch of NASA's Lyndon B. Johnson Space Center is exploring the use of virtual environments as a training aid. Maintenance of the Hubble Space Telescope as well as Space Station Freedom is problematic. How do you train astronauts to repair equipment in the weightlessness of space with realistic dynamics of the objects? Virtual environments which immerse the user into a synthetic space can play an important role in training for such maintenance missions.

In an attempt to address these issues two research and development projects are underway. The objectives of the Hubble Space Telescope Repair and Maintenance is To develop a Virtual Environment suitable for training astronauts in preparation for Hubble Space Telescope Repair and Maintenance missions. Graphical models of the Hubble Space Telescope and a large number of digitized close-out photographs of the instrument are available. A virtual environment based on a graphical model of the HST is under development. Where high fidelity, detailed images are needed, appropriate digitized images will be displayed. The system is designed to address specific elements of future missions that will require location of objects and interaction with handholds, panels, fasteners, and orbital replacement units.

A second demonstration project, Training for EVA (Extra Vehicular Activity) Payload Interaction has as it's stated object: To develop a proof of concept training environment that provides astronauts with a simulation of satellite dynamics such as that match those observed during the STS-49 Intellsat retrieval mission. If the proof of concept system is judged to be valuable for training by training personnel and experienced astronauts, a more complete model will be developed and delivered as a training system for future payload retrieval missions. As was observed in the 1992 rescue of the STS-49 Intellsat satellite, the capture and manipulation of large objects in a weightless state was quite difficult. It is hoped that the use of virtual environments will give crew members an opportunity to develop and be trained on new procedures. According to Bowen Loftin manager of the program the initial demonstration proof-of-concept of a training environment will operate as follows:

"The objective of this demonstration is to allow users to experience a training session in an interactive virtual environment by exchanging a faulty battery in the Hubble Space Telescope (HST) with a new replacement battery. The user moves to the HST, opens the door to the battery bay, takes it back to the space shuttle orbiter, and places it on top of the hardware pallet in the payload bay. The user than takes the new battery from the cargo bay hardware pallet to the HST and installs it behind the battery bay door. A narrator will introduce a few details to the user in the beginning of the session, and correct the user when he/she makes a wrong move. The user can grab the bay door or the battery by reaching out and clinching the yellow handle with the gloved hand. Movement about the environment is accomplished with the two hand-controllers of the chair. This chair emulates the functionality of a Manned Maneuvering Unit and uses a translational control (left side) to move in any straight line by pulling or pushing in the desired direction of motion. Also, a rotational control (right side) adjusts the user's orientation about his/her center point. Changes are initiated in yaw by twisting the control left or right, in pitch by pulling it back or pushing forward, and in roll by tilting it left or right. In addition to the direct anticipated benefits of using a virtual environment for training the Software Technology Branch is also collaborating with the Marshall Space Flight Center to enable personnel at the two centers to simultaneously share the same virtual environment. Using these techniques joint training exercises could be conducted without the usual collocation constraints."