Blue Origin has completed acceptance flight tests of its cryogenic BE-3 deep-throttle engine, and plans to begin autonomous flight tests with the reusable New Shepard suborbital human spacecraft it will power later this year.

Rob Meyerson, president of the secretive company bankrolled by Amazon.com found Jeff Bezos, told reporters April 7 “we’re probably a few years away from selling tickets” on New Shepard, but the completion of acceptance testing was a big hurdle to clear.

The 110,000-lb.-thrust engine can be throttled down to 20,000 lb. thrust for a vertical landing, Meyerson said. New Shepard testing at the company’s facility in West Texas will begin in autonomous mode, with Blue Origin crew eventually occupying the vehicle’s three seats for the initial push to 100 km – the traditional altitude where space is said to begin.

Ultimately paying passengers will fly from the Blue Origin site in Van Horn, Texas, either for tourism or research. The vehicle’s booster will lift them to the suborbital altitude before flying back to a tail-down landing at the launch site. The crew capsule will return to the same facility via parachute, after providing about four minutes of microgravity to its passengers and experimental payloads, Meyerson said, declining to announce a price for the service.

Flight testing New Shepard also will allow the company to build time on the BE-3, a liquid-oxygen, liquid-hydrogen engine the company plans to upgrade as a commercial product designated BE-3U for upper stage use. That will require a larger nozzle and other changes.

“To make the BE-3 into a BE-3U, the simplest change could be a large expansion ratio nozzle, which is designed to operate at altitude,” Meyerson said. “But there will be other changes we’ll make as we fly the BE-3 in our suborbital flights. We could theoretically with our plans have dozens if not hundreds of flights with the New Shepard vehicle with the BE-3 before we fly an upper stage BE-3U. So we could do performance improvements if our customer base needs that.”

That base could include United Launch Alliance, which already has said it will buy Blue Origin’s BE-4 hydrocarbon-fuel main-stage rocket engine for its next-generation launcher. That engine is in testing at the component level – the power pack and a subscale injector – and is on schedule as a rapid follow-on to the Russian-built RD-180 engine, with full-scale testing set to begin next year, according to Meyerson.

“The BE-4 is a first-of-its-kind engine to be developed in the United States. It uses liquefied natural gas to produce 550,000 pounds of thrust,” Meyerson said. “The BE-4 offers the lowest cost and is the fastest path to production for an American-made engine. The engine is more than three years into development, and we’re now on track to conduct full engine testing in 2016 and complete development of the engine by 2017, two to three years ahead of any other alternative engine that’s out there.”