You probably have high expectations for the reliability of speakers you want to use. Check out how they compare with some of NASA’s requirements for speakers going into space.Since 2017, MISCO has had the privilege of working on the speakers for the Orion spacecraft. The Orion capsule will carry humans further into space than they have ever traveled before, bringing people back to the Moon, and, possibly one day, to Mars.
Just how tough does the speaker in Orion need to be?
“It has to be able to withstand 4,000Gs,” 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 success and safety of each NASA mission.”
MISCO prides itself on designing robust speaker drivers and offering extensive testing capabilities. But to design and test something to withstand four thousand times the strength of gravity was something MISCO had never been asked to do.
“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 simulates the extremes of a rocket launch or a possible emergency mission abort scenario. Following this test, the speaker is evaluated for any damage, loosening of parts, and must meet all of the electro-mechanical-acoustical specifications that it did before the 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. soundwaves. 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 going off, even if they’re sleeping.
However, that loss of pressure also means the speaker needs to be able to produce sufficient dB SPL in an atmosphere of 9 PSI (minimum specified) just as well 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 not something MISCO had ever had to consider so another challenge was presented. Extensive modeling and calculations were done at MISCO to show the chosen speaker design would in fact work and then was validated with customer measurements in pressure chambers.
“We had 1,600 lines in our log book related to issues on this project. Every one of those 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 not on 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 -40C to +85C and the general requirement that the speaker operate “in all conditions and all environments.”
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 the 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 terms of its coupling with the ambient air. To assure 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 in it 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 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 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 be cheering 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 reach out to us and we’d be happy to talk about how to support you.
Image credits: NASA/Joel Kowsky, NASA/Rami Daud