The SM11 is part of a system that collects samples of exhaust gases from the Shuttle orbiter's propulsion system aft fuselage area to sense any gas leaks in the plumbing. During ascent, an SM11 Microphone mounted inside a system electronics box, picks up the sound generated from the orbiter propulsion area at launch. Its output signal controls equipment that triggers a sequencing of pyro-valve devices that enable air samples to enter each of 6 vacuum bottles at various times during the ascent. The collected gas samples are later analyzed after the orbiter returns to Earth. Having this data can save maintenance and inspection hours.
"Using the SM11 as the triggering mechanism has several advantages," said Michael Pettersen, director of applications engineering at Shure. "Because it's a dynamic microphone, it can withstand the extreme sound pressure levels without being damaged. Sounds at that high a level can't be created by any other source on the Shuttle, so it is a reliable system-triggering device. Finally, using the SM11 acoustical sampling method doesn't require any direct connection to the orbiter propulsion system.
On this mission (STS-24), Discovery will transport the Kibo Japanese Experiment Module - Pressurized Module (JEM-PM) and the Japanese Remote Manipulator System (JEM-RMS) to the International Space Station.
(Claire Beeson)
