COLORADO SPRINGS — United Launch Alliance CEO Tory Bruno says his choice of planning to reuse only the BE-4 engines – not the entire first stage – of the company’s new Vulcan rocket was driven purely by the economics.

The cost equation also favors the Blue Origin BE-4 engine, he says, because it employs “clean burning” methane fuel, he says.

“It takes a good seven to eight reuses before you can pay off the additional cost of all the extra equipment and the logistics of recovering it and then bringing it back to the factory with a reasonable amount of refurbishment that you have to do,” Bruno told Aviation Week in an April 15 interview. “You can’t just dust it off and reuse it. You have got to do plumbing and new cables and insulation and all this kind of stuff. Our calculations say [it takes] 7-8 uses to break even … To really make it worth while, you have really got to reuse it about 15 times.”

ULA’s rival, SpaceX, failed to successfully land a Falcon 9 v1.1 first stage after an April 14 launch. “I’m surprised they didn’t make it yesterday,” Bruno said. The company plans to attempt its fourth first-stage recovery during NASA’s seventh Commercial Resupply mission, slated for the summer. SpaceX is attempting to land the first stage on a barge at sea to prove the concept, before eventually landing it back at Cape Canaveral Air Force Station, Florida.

In the April 14 attempt, “We seem to have landed a little bit too hard,” said Hans Koenigsmann, chief engineer for the mission at SpaceX, during a post-mission briefing at NASA. “Looking at the data, everything seemed to be fine. It is not quite clear what happened.”