Since 2017, MISCO has had the honor of working on the speakers for the Orion spacecraft. The Orion capsule will transport humans further into space than ever before, enabling a return to the Moon and, perhaps one day, to Mars.
Meeting NASA's Rigorous Standards
Just how tough does the speaker in Orion need to be?
"It has to be able to withstand 4,000 Gs," says Rich Field, Chief Engineer at MISCO, who led the project. "And it has to withstand that force along multiple axes and still be able to perform during and after that impact. It's an example of the 'margin on margin' thinking that is critical to assure the success and safety of each NASA mission."
MISCO prides itself on designing robust speaker drivers and offering extensive testing capabilities. However, developing and testing a loudspeaker that would withstand four thousand times the strength of gravity was a new challenge for MISCO.
"They do what's called a pyroshock test," says Rich. "They use a steel beam with an explosive on one side and then put an object on the other side to represent the speaker. They detonate the explosive and then confirm it created enough force. Then they strap the real speaker on and do it again."
This test simulates the extremes of a rocket launch or a possible emergency mission abort scenario. Following the test, the speaker is checked for any damage or loosening of parts and must meet all of the electro-mechanical-acoustical specifications it had before testing.
Out of this World Engineering
MISCO engineers are used to solving unique acoustical challenges for customers here on Earth. In space, the problems are a bit different. For example, loudspeakers make sound by exerting force on air to create localized variations in air pressure, i.e., sound waves. A loss of air pressure in the Orion could be a life-threatening situation, and the astronauts need to be able to hear the loss-of-pressure alarm, even if they're sleeping.
However, this loss of pressure means the speaker must produce sufficient dB SPL in an atmosphere of 9 PSI (the minimum specified) just as effectively as it does in 14.7 PSI (the air pressure at sea level on Earth). Modeling or measuring loudspeaker performance within the context of atmospheric modulation was a new challenge for MISCO. Extensive modeling and calculations were conducted to demonstrate that the chosen speaker design would work. This was then validated with customer measurements in pressure chambers.
"We had 1,600 lines in our log book related to issues on this project. Each represented something we had to check, tweak, and figure out. That's much more than any other project we've ever done," says Rich. "We spent a lot of time and resources getting just the right adhesives for the speaker."
There's a special list of NASA-approved materials that have been tested and verified to function in space over the years, and the commercial-grade epoxy MISCO uses on many of its speakers was missing from that list. MISCO worked with a special supplier and applied our decades of speaker building and adhesive knowledge to create a solution that met the severe testing of both the pyroshock, the temperature requirements of -40°C to +85°C, and the general requirement that the speaker operate "in all conditions and all environments."
MISCO’s Expertise and Innovation
MISCO was selected for the Orion project because of its background working on speakers for military applications and because its Oaktron division had previously developed speakers for the International Space Station (ISS).
The need for more equipment and lab space meant the speakers for Orion had to be even smaller than the ones used in the ISS. That created sound power challenges because smaller speakers have smaller diaphragms and are physically more limited in coupling with the ambient air. To ensure success in achieving acoustical output, MISCO engineers spent countless hours designing and creating predictive models and drawings long before the first proto unit was even built.
The Orion speaker has two identical transducers for redundancy purposes because no one wants to take any chances with people's lives when they are hundreds of thousands (or millions) of miles away from the Earth. (Mars, at its closest, is about 35 million miles away.) Each transducer uses a powerful neodymium magnet to optimize speaker output and help reduce size and weight.
Countdown to Orion Liftoff
The Orion will be lifted into space for the first time atop the Artemis I rocket, the most powerful rocket NASA has ever used. Because the first mission, scheduled for August or September of 2022, will not have astronauts on it, MISCO's speaker will not be installed inside the Orion yet.
"They told me to pencil in 2025," says Rich. "That's when Orion is scheduled to fly around the Moon with people in it for the first time."
Everyone at MISCO will cheer on each launch and be proud of the part we're playing in furthering the exploration of space. Sometimes, the work MISCO does is, in fact, rocket science.
If you have extreme audio engineering needs, either for this planet or another, please contact us. We'd be happy to discuss how to support you.
Image credits: NASA/Joel Kowsky, NASA/Rami Daud