Blue Origin, the secretive commercial space company established by Amazon.com founder Jeff Bezos, is readying for qualification tests of its liquid hydrogen-fueled BE-3 engine for a suborbital flight following completion of a key ground demonstration that simulated a full mission of its New Shepard vehicle from launch to vertical landing.

Unveiling new details about the design and testing of the liquid hydrogen-fueled BE-3 engine at the core of its plans to develop low cost, reliable suborbital and orbital human launch systems, Blue Origin says the company remains on track to perform its first orbital flight in 2018. The BE-3 will provide power for both the suborbital and orbital versions, with the former mission providing an experience-building exercise to the latter flights. Blue Origin also reveals it is developing an upper-stage version of the engine for the orbital vehicle dubbed the BE-3U.

The full mission cycle test, which was conducted at the company’s test facility near Van Horn, Texas, began with a run at 110,000 lb. thrust for 145 sec. to simulate the boost phase, followed by a four-and-a-half minute shut down to simulate the coast through apogee. The engine was then restarted and throttled down to 25,000 lb. thrust to simulate a controlled vertical landing.

“This is a very significant milestone for us because it gets us over a major hurdle and a major risk, and it gets us ready for the checkout of the vehicle and for flight test,” says Blue Origin program manager and president Rob Meyerson.

Test work building up to the full-cycle BE-3 test in November was conducted over nine months and included 160 starts and 9,100 sec. of engine operation. “That equates to a test every two days and sometimes was actually three or four tests per day,” Meyerson says. The work forms part of an unfunded extension of Blue Origin’s Commercial Crew Development Round 2 (CCDev2) contract with NASA, and builds on tests of the BE-3 thrust chamber conducted under an earlier funded phase of CCDev2 at the space agency’s Stennis Space Center in Mississippi in 2012. Those tests “allowed us to accelerate the program by about one year,” Meyerson adds.

The next major milestones include a review later this month of the subscale propulsion tank assembly, and a full space vehicle subsystem interim design review in March 2014. Blue Origin is scheduled to give NASA its final CCDev2 briefing in May 2014.

The BE-3 design is based on the combustion “tap-off” engine cycle, sometimes also known as the ‘topping cycle’ or chamber bleed cycle, in which the combustion gases from around the walls of the main chamber are bled off, partially cooled and used to power the engine’s turbopumps. Blue Origin says the cycle, which produces a relatively high specific impulse (Isp), is simpler for options such as pre-burning staged-combustion, and well suited to human spaceflight because of its single combustion chamber and “graceful” shutdown mode.

Despite the challenges of the cycle, including potentially complex startup systems and high temperature turbine drive gases, Meyerson says “it is different because it only uses the one combustor, so it has got a tendency to shut down rather than feed the combustion process.” Although the heritage Rocketdyne company developed the experimental J-2S “tap off” variant of the upper-stage J-2 Saturn V, Meyerson says the BE-3 is the first engine of its type developed to fly.

The company also is focusing on modifications to adapt the baseline engine to the upper-stage BE-3U variant. “We demonstrated very high efficiencies on the core injector and that allows us to put on different nozzles including a short design for deep throttling for landing, and a large expansion ratio nozzle design for the upper stage, which will give the higher performance and efficiency you need for that,” Meyerson says. “But we are also looking at other things we can do for that in terms of expendables and lower cost manufacturing.”