Turn up the bass! Orion Service Module to begin acoustic testing at Plum Brook Station

Michael Cole

SANDUSKY, Ohio — Engineers and technicians wheeled the Orion service module test article into the powerful acoustic testing chamber at NASA’s Glenn Research Center’s Plum Brook Station testing facility in Sandusky, Ohio, last week. The long-awaited first round of testing is scheduled to begin Monday, April 18.

“This week we are hooking up all the instrumentation cables and the sensors and checking those out,” Plum Brook’s Space Power Facility Manager Jerry Carek told SpaceFlight Insider. “If we start on Monday as planned, we’ll be testing for the next six weeks.”

The testing will take place in the Reverberant Acoustic Testing Facility (RATF), one of Plum Brook Station’s trio of world-class test chambers that will put the service module through its paces. In addition to the RATF, Plum Brook Station also features the world’s largest vacuum chamber and the world’s most powerful vibration table. All three are housed within Plum Brook’s Space Power Facility.

Last week, the service module was towed on rails from the Space Power Facility’s preparation high bay, across the floor of the vacuum chamber, which is at the center of the building, and into the RATF at the building’s west end. Once inside the chamber, the service module was elevated in preparation for testing.

“The service module is placed on a special support stand,” Carek said, “which is designed so that its held up off of the floor far enough to bathe the vehicle completely in the acoustic energy field.”

The RATF is a chamber that features a wall studded with numerous rows of powerful horns. Nitrogen gas flowing through hydraulic actuators that are turning on and off at incredibly rapid speeds create the horns’ horrendous acoustic assault. Capable of bathing the service module with an overall acoustic sound pressure level of 163 decibels, it is by far the most powerful acoustic chamber in the world.

Mounted atop the service module for these tests are a number of mass simulators intended to simulate the mass distribution of the Orion crew module. A crew module test article is not scheduled to arrive at Plum Brook for testing until late in 2017.

For now, the acoustic testing on the service module is expected to continue until this summer.

“There will be multiple rounds,” Carek said, “and for each round, we basically do four different tests. We sort of creep up on what we call the final acoustic spectrum.”

This “creep up” is what causes the testing to take so many weeks.

“With every test, you’re subjecting the test article to different inputs,” Carek explained. “You’re throwing different forces at it, and you’re measuring the responses at different areas on the test article. Each test has its own objective. There are different load cases too. Throughout a mission, you don’t just take the very worst case that this thing experiences. You take the different cases because the forces will be different at different areas. Even in the acoustic environment, right during launch, you’ll have a different acoustic profile than you’ll have halfway through the atmosphere. Each test case is tailored toward a specific condition.”

The Orion service module is provided by the European Space Agency (ESA) and built by Airbus Defence and Space. The service module will power, propel, and cool the vehicle; it will also provide Orion with air and power.

Following the approximately six-week campaign of acoustic testing, the service module will next be moved onto the Mechanical Vibration Facility (MVF) for vibration tests that will continue throughout the summer.