WASHINGTON — Aerojet Rocketdyne of Sacramento, Calif., wrapped up development testing on a pair of launch-abort engines for the space capsule Boeing is developing to ferry astronauts to and from the international space station.

The latest round of tests took place near Mojave, Calif., during the second half of October. A pair of engines, each capable of generating about 39,000 pounds of thrust, were fired for a combined 29.7 seconds, Boeing spokeswoman Kelly George wrote in a Dec. 16 email. The successful development tests clear the way for qualification tests, in which each engine will be fired for 11 seconds — double their design requirement, George said. 

Developed by Pratt & Whitney Rocketdyne before the company was acquired this year by Aerojet parent Gencorp Inc., the engines are for CST-100’s pusher-style abort system. In the event of a launch mishap, four such engines would propel CST-100 and its crew to safety. In a normal launch, the system will be carried to orbit, where its fuel could be used to pad margins for the rest of the mission, Boeing Space Exploration of Houston said in a Dec. 16 press release. 

Space Exploration Technologies Corp. (SpaceX) is working on a similar pusher abort system for its Dragon space capsule, which is a competitor to the CST-100 in NASA’s Commercial Crew Program. The program aims to field a commercial crew taxi service for the space station by 2017. 

Pusher abort systems are different from tractor-style abort systems — such as the one used on the Saturn 5 rocket for Apollo missions and the one planned for NASA’s Space Launch System — which are discarded shortly after liftoff during a nominal launch.

NASA in August 2012 awarded Boeing, Sierra Nevada Corp. and SpaceX contracts to continue developing their crew taxi concepts in the third round of the Commercial Crew Program. Boeing’s award, at $480 million, is the largest of the three. 

Competition is now underway for the fourth and final round, under which a crewed demonstration flight to the international space station could happen as soon as 2015. A fourth-round award is expected by September.

NASA wants at least one commercial crew taxi flying by 2017 so that it can stop paying Russia to take crews on round trips to station aboard Soyuz spacecraft. 

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Dan Leone is the NASA reporter for SpaceNews, where he also covers other civilian-run U.S. government space programs and a growing number of entrepreneurial space companies. He joined SpaceNews in 2011.Dan earned a bachelor's degree in public communications...