Boeing [BA] beat out Ball Aerospace & Technologies Corp. [BLL] to win a $799.5 million avionics instrument unit for the Ares I upper stage rocket that someday will lift the Orion crew exploration vehicle into space, NASA leaders announced in a news conference yesterday.

That completes the major contract awards for the Constellation Program effort to design the next-generation U.S. spacecraft to replace the troubled space shuttle fleet. Lockheed Martin earlier won the contract for the Orion space capsule.

The Ares I upper stage avionics instrument unit contract competition began with five rival companies vying for the prize, which NASA then downselected to just Boeing and Ball.

Officials at the news conference declined to detail precisely why Boeing won, because that will have to be disclosed to the bidders in post-award conferences.

But officials’ comments indicated that Boeing had an edge in several ways, such as the fact that Boeing several months ago won the $514.7 million NASA contract for the Ares I upper stage, beating out ATK [ATK] and teammates Lockheed Martin [LMT] and Pratt & Whitney Rocketdyne, a unit of United Technologies [UTX]. That means Boeing already is involved, deeply, in that part of the overall Orion-Ares system.

Also, Boeing will use a computer assisted design (CAD) software to design the just-awarded avionics instrument gear, which will be the “brains” of the vehicle. That CAD system is a technological capability that Boeing has used for years, notably on designing the 777 airliner.

Boeing as well has extensive experience with rockets, especially with its Delta lifters that now are marketed through United Launch Alliance, a joint venture with Lockheed Martin.