AFRL tests next-generation NASA communications system

  • Published
  • By John Schutte
  • Human Effectiveness Directorate
Engineers at the Air Force Research Laboratory's Human Effectiveness Directorate (AFRL/HE) are testing a next-generation hearing protection and communications system for astronauts, designed for use inside NASA's advanced crew escape suit (ACES) during the remaining space shuttle missions. 

NASA's upgraded technology and AFRL/HE's related assessment techniques could also help guide design of helmet and communications systems for NASA's Constellation Program, according to audiologist Richard Danielson of the National Space Biomedical Research Institute and the manager for Audiology and Hearing Conservation at the NASA Johnson Space Center in Houston, Texas. 

Constellation is NASA's recently initiated space exploration mission to return humans to the moon, then on to Mars and other solar system destinations. 

"We're assessing the modification only for the shuttle missions through 2010 right now, but the method of evaluating it and what we know about the technology may be used for the new Orion launch vehicle's helmet and communication system," Danielson said. 

NASA wants to improve comfort and incorporate a dual-microphone system with a shorter boom that can adjust to accommodate a range of head shapes and sizes. With the current fixed-position boom the microphone sometimes is too far away from smaller crew members. 

Dr. Danielson said NASA teamed with AFRL to conduct tests "because we've had good working relationships with AFRL and the team here is very supportive. AFRL's reputation and facilities are well-known as is their expertise in conducting tests that are technically correct." 

AFRL has been a leader in aircraft acoustics for more than 50 years, according to Dr. Mark Ericson, an AFRL/HECB electronics engineer with a doctorate in speech and hearing science who is directing the tests. 

Tests were conducted March 13 at the 50,000-watt microphone-in-real-ear (MIRE) facility at AFRL/HE's Warfighter Interface Division, Battlespace Acoustics Branch (HECB), where sound levels experienced during a shuttle launch were reproduced.
Astronauts in the shuttle crew compartment experience noise levels around 115 dB SPL (sound pressure level) during liftoff for less than one minute, according to Dustin Gohmert, NASA Johnson Space Center's lead engineer for the communications upgrade project. For comparison, a chain saw operates at about 110 dB and a loud rock n' roll concert can exceed 120 dB SPL.
 
While the data will help NASA determine if astronauts are exposed to potentially harmful noise levels during missions, researchers also want to make sure that communications remain as clear as possible during the all-important launch period. 

"During liftoff the high-noise level is pretty short duration, but typical of military scenarios the noisiest and busiest parts of their missions are also the most critical for communication," Dr. Ericson said. 

Researchers placed small microphones in the ears of 10 human test subjects to pick up noise levels at the ear, both with and without hearing protection. The difference between the two readings reflects the noise protection level afforded by the system. 

With this data AFRL researchers can also establish safe exposure times for speech intelligibility test subjects. While tests conducted in the MIRE lab were of short duration--about five minutes of actual noise exposure--the speech intelligibility tests will last for several hours per day for each test subject, Dr. Ericson said. 

For those tests, NASA's improved dual-microphone system will be attached to the communications cap assembly, Mr. Gohmert said. The new system is expected to marginally increase hearing protection for astronauts and greatly improve comfort, which means crew members will be able to wear the device for longer periods, Mr. Gohmert said. 

The ACES is a fully pressurized system that includes the bright orange full-body suit, a launch/entry helmet that attaches to the suit with locking rings, and a communication carrier assembly (CCA)--also known as the "Snoopy cap"--worn under the helmet that contains protective ear caps and the microphone boom assemblies.
 
The ACES suit is primarily worn during shuttle launch and entry and in any on-orbit emergency situations to protect crew members from exposure to the elements and to provide a safe atmosphere around the astronaut, Mr. Gohmert said. 

The system weighs approximately 95 pounds fully equipped with emergency oxygen bottles, parachute, life raft, life preserver, search and rescue radio, drinking water, survival knife, day/night flares and signaling mirror and other survival gear.