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TTU News

NASA is proposing to use a mechanism invented by Tennessee Tech University mechanical engineering professor Stephen Canfield in America's first new human spacecraft in 30 years.

Named the "Canfield joint," the gimbal mount could be included in the design of the Crew Exploration Vehicle, or CEV, a transporter that would replace existing space shuttles when the current fleet is retired about 2010. The Canfield joint provides three degrees of freedom, allowing users to control and keep a thruster in a constant position on a rotating spacecraft.

"There are several advantages to this mechanism, including the ability to replace 16 fixed thrusters on the CEV's reaction control system with just four thrusters that give you active control to point them anywhere in the hemisphere," explained Canfield. "You don't assume you could get this type of full hemispherical pointing with other devices."

Canfield says this set up is a more efficient way to provide thrust, which increases performance. And fewer parts reduce the weight of the vehicle and the chances of mechanical failure.

According to, one of the nation's leading online sources on space flight developments, the Canfield joint could not only revolutionize the CEV's reaction control system, but also dramatically improve the vehicle's solar panel orientation capabilities.

With the current design, the solar panels are unable to continually track the sun. This tracking is vital because the panels provide electricity necessary to keep the CEV's super-cold propellants at the correct temperature. Using the Canfield joint at the base of the two solar panels could solve the issue.

"The solar arrays are capable of tracking the sun while the vehicle rotates in a thermal-control, or what we call a 'barbecue' roll maneuver," said Canfield. "It's basically swimming a backstroke in space to keep oriented to the sun."

NASA unveiled plans for the CEV in September 2005 as the key element in the Constellation Program. Plans include for the CEV to transport up to six crew members to and from the International Space Station. NASA is also planning to use the CEV to send up to four crew members to and from the moon in 2018. It could also support future Mars missions.

Canfield, named by Business Tennessee magazine in 2004 as one of the state's Top 10 scientists, conducts other high profile research supported by NASA. He and students continue work on the momentum exchange electrodynamic reboost tether system, or MXER system, that could some day lead to harnessing the Earth’s forces to propel rockets into space and to capture and release payloads.

To see animations of the gimbal mount and the thermal-control or barbeque roll, visit