Among the objectives of the next scheduled test of the space shuttle's reusable solid rocket motor (RSRM) is gathering further data on vibration loads that will be experienced by the RSRM-derived Ares I rocket's first stage, according to ATK.

ATK is both the prime for the RSRM and the first stage of the Ares I, which NASA will use to boost the Orion crew exploration vehicle to orbit. The Ares I first stage will be a five-segment version of the four-segment RSRM. The test is scheduled for Nov. 1. The last test was held in May (DAILY, May 29).

Engineers already have an idea what loads to expect on Ares I because of experience on the shuttle program, according to Mike Kahn, vice president of space launch systems for ATK.

"But now that we know the configuration of the Ares rocket, we can put instrumentation with better fidelity so we know what kind of vibrations are going to be induced on the system," Kahn told Aerospace Daily. The test also will evaluate some long-lead materials that are slated for use on Ares.

ATK tests full-scale RSRMs roughly twice a year at its Promontory, Utah test site. While the tests are sponsored by the shuttle program, ATK also uses them to gather data on Ares' largely similar systems. The first flight of the Ares will be the so-called "Ares I-X" test in April 2009, although that will use only a four-segment RSRM. ATK will begin tests of the five-segment RSRM around that same time. The only previous five-segment test was in October 2003.

Another test objective of the Nov. 1 firing is a "One APU Out" test in which engineers will validate the performance of the rocket's thrust vector control (TVC) system with only one of its two Auxiliary Power Units (APUs) working. The redundant APUs power the hydraulic system that gimbals the rocket's nozzle during ascent.

Eighteen seconds into the two-minute burn, the team will simulate an APU failing, to make sure a single APU is enough to turn the nozzle. "Now the analysis ... early in the [shuttle] program in the 80s shows that will work, but we've never actually had an APU go out on the shuttle program and we've never actually shut one off during a ground test," Kahn said.

Since the Ares I will use the same skirt and TVC system as the shuttle, "obviously the value of that knowledge is certainly applicable to Ares," he said.

The issue of whether the TVC system is capable enough to keep the rocket stable as it rises has been put to bed by previous tests, according to Kahn. Engineers have calculated that the current RSRM TVC system has twice the capability that should be needed to keep the Ares I flying straight, he said.