Wales.Larrison@ofa123.fidonet.org (Wales Larrison) (11/13/90)
Allan, you had asked how SSF was going to perform their design verification work. Coincidently, I ran across a description of the process in the 6 Nov "Aerospace Daily". Fundamentally, the NASA SSF program relies on end-to-end testing of high-fidelity replicas on the ground (which is standard industry practise). While the general outlines of the verification process are established, the exact test procedures and verification activities are still being planned, according to Marc Bensimon, deputy manager for Space Station Freedom programs and operations. Present plans call for two separate SSF verification facilities. An avionics facility similar to the Shuttle Avionics Integration Laboratory (SAIL) in Houston will verify electronic hardware and software systems, while a "stage integration facility" will test physical interfaces and interactions among SSF hardware elements. After the flight elements are verified as functional in before- launch tests using these facilities, a replica of each Station element would be installed in one facility to obtain a complete end- to-end simulator. (Which one would be cheaper to upgrade to the continuing end-to-end simulator is still being studied.) Under this "backfill" approach, "That replica can be a high fidelity prototype, or it can be an engineering model, or it can be a suitable representation of that first piece," Bensimon said. "That's something you've got to determine on a piece by piece basis...and you run the same kind of test on the replica as you do on the flight piece itself. That gives you a validation of the replica." In addition to testing how well Station elements work together, the two ground facilities will also help plan upgrades and work around problems that develop once the Station is orbited. Bensimon said. "If we're successful, to me the best sign of success on the Space Station is that 15 years from now you're doing things on it that today you hadn't imagined yet...So if that's the case, you're going to be changing an awful lot of things on the Space Station and a lot of the software is going to change." Bensimon said the ground-based verification activities will be supplemented with microgravity experiments on Station elements that will behave differently on the ground and in space. "Anything that's got a phase change in it, where you go from a liquid to a gas, those kind of things you can develop a process on the ground and try it on the ground, but the gravity effects, because of the buoyancy of the gases and so on, (are) difficult to simulate on the ground," he said. "...We'll do as much ground development as we can, but eventually you're going to have to prove it out in flight." "There is an effort in the program to identify where we feel flight tests are necessary," Bensimon said. "Some of them they're going to be doing KC-135 zero-G flights, and they're going to be doing some Spacelab experiments and so on." Bensimon said verification planning is going on throughout the Space Station program, with integration contractor Grumman responsible for the overall job and "significant efforts" underway at the various work package contractors. -------------------------------------------------------------------- Wales Larrison Space Technology Investor -- Wales Larrison Internet: Wales.Larrison@ofa123.fidonet.org Compuserve: >internet:Wales.Larrison@ofa123.fidonet.org --------------------------------------------------------------------------