Atlas V’s Upper Stage Passes Milestone Toward Flying Astronauts

AmericaSpace image of Atlas V rocket fairing with the GPS IIF4 Cape Canaveral Air Force Station Photo Credit Jason Rhian.jpg
Photo Credit: Alan Walters /

United Launch Alliance (ULA) has successfully completed a Preliminary Design Review (PDR) to prepare the Colorado-based company’s Atlas V rocket for use to send astronauts to orbit in commercially developed and built spacecraft. This review dealt with the initial development testing of the Dual Engine Centaur (DEC) upper stage that is being developed as part of NASA’s Commercial Crew integrated Capability, or CCiCap. The announcement that the PDR had been completed was posted on ULA’s website on Wednesday, June 12.

AmericaSpace image of United Launch Alliance ULA Atlas V Centaur SBIRS GEO 2 Cape Canaveral launch Photo Credit John Studwell
Photo Credit: John Studwell / AmericaSpace

Through funding provided through Independent Research and Development, ULA is working to have the Atlas V’s Centaur Engine certified to receive a human-rating. The Atlas launch vehicle is capable of carrying both a single and dual engine on the Centaur second stage. Given the payloads the Atlas normally boosts to orbit, satellites and unmanned probes, are not of sufficient mass to require the DEC, the upper stage has flown in the single engine configuration for some time.

According to a release posted on ULA’s website, the dual configuration has traveled to orbit more than 160 times. The current iteration of the Atlas V has increased performance to a level that, since 2003, has rendered the dual engine configuration unnecessary.

Development testing was held at Innovative Engineering Solutions located in California. Testing included liquid oxygen duct gimbal waterflow tests to validate flow characteristics and loads testing at liquid nitrogen temperatures to determine loads and stresses and the ability of the duct to survive in the vacuum of space.

During the PDR, ULA’s customers under NASA’s commercial crew program, Boeing and Sierra Nevada Corporation (SNC), along with other government customers, reviewed the design requirements to implement the upgrades for the Centaur Upper Stage.

“DEC provides a performance improvement over Single Engine Centaur (SEC) that is extremely beneficial for LEO missions,” said George Sowers, ULA’s vice president of Human Launch Services. “For human spaceflight, the increased thrust of the DEC allows the trajectory to be ‘flattered’ to provide a safer re-entry environment for the crew in the unlikely event of a crew abort situation.”

Under CCiCap, SNC and Boeing have tapped the Atlas V to boost their commercial spacecraft (Dream Chaser and the CST-100 capsule respectively) to destinations in low-Earth orbit. Space Exploration Technologies (SpaceX), the third company competing in CCiCap, will use the combination of the company’s Falcon 9 rocket and Dragon spacecraft.

“The testing was successful and met all of the criteria,” Sowers said. “The next major milestone for the DEC design is the Critical Design Review, scheduled for next spring.”


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