In what is probably the year’s most exotic approach to space launch, billionaire entrepreneur Paul Allen and aircraft designer Burt Rutan aim to use the equivalent of two Boeing 747-400s to carry a Falcon 9-derivative rocket to 30,000-35,000 ft. for an air-drop launch of satellites or humans into low Earth orbit.

Their two-fuselage design brings to mind the Model 76 Voyager developed by Rutan that circled the world without stopping or refueling Dec. 14-23, 1986, or, more recently, the WhiteKnight mother ship for SpaceShipOne that won the Ansari X Prize in 2004 as the first privately funded, human-rated spaceship. But this time the carrier aircraft is to have a wingspan stretching 385 ft.—a 747-400’s is 212 ft.—and a takeoff weight of 1.2 million lb., which rivals an Airbus A380’s.

“Since the success of SpaceShipOne, I have thought a lot about how to take the next big step, a private orbital system,” Allen says of his new venture, Stratolaunch Systems, part of Vulcan Inc., the business and philanthropic holding company he owns in Seattle. Funding the venture will be “an order of magnitude beyond SpaceShipOne,” he acknowledges. Stratolaunch aims for the first test flight of its “carrier aircraft” in 2015 and an initial rocket launch in 2016.

Allen and others associated with the venture—including Rutan, former NASA Administrator Michael Griffin as a company board member, and Gary L. Wentz Jr., former chief engineer of science and mission systems at NASA’s Marshall Space Flight Center who is now Stratolaunch’s chief executive and chairman—declined to provide many specifics about the program’s design, specifications or costs during a briefing in Seattle last week. Rutan says their reluctance stems from a need to protect proprietary data.

The Stratolaunch enterprise is scattered across the country. Scaled Composites, the company Rutan founded that is now part of Northrop Grumman, will build the composite carrier aircraft in a new hangar it is constructing at Mojave Air and Spaceport in California. The Falcon launch vehicle is being developed at the campus of Space Exploration Technology (SpaceX) in Hawthorne, Calif., and the 40,000-50,000-lb. mating and interface system needed to suspend the rocket from the carrier’s center wing is being developed by Dynetics Inc., an aerospace and engineering company in Huntsville, Ala.

Wentz says Stratolaunch is in the process of purchasing two used 747-400s that will be cannibalized for engines, avionics, flight deck, landing gear and other proven systems that can be recycled to cut development costs. One task is to design the launch control system, which will be handled entirely from the carrier aircraft, he says.

Dynetics’s mating and interface system will be required to hold a launcher weighing up to 490,000 lb. “We’ll be integrating the mission planning stuff associated with the drop and the launch, and building the hardware that will allow the drop,” says David A. King, a Stratolaunch board member and executive vice president of Dynetics.

For that work, Dynetics will apply its experience as prime contractor on the U.S. Air Force’s GBU-43/B Massive Ordnance Air Blast (Moab) bomb, and with Boeing on the GBU-57A/B Massive Ordnance Penetrator (Mop) bunker buster, which weigh 20,000 and 30,000 lb., respectively.

“We’ve got a fair amount of experience dropping big, heavy stuff, too, both aerodynamically and from a mechanical perspective,” King says.

Aerodynamic considerations probably will require a shorter version of the Falcon 9 launch vehicle than the one SpaceX is using in its bid to supply cargo and eventually crew to the International Space Station. That in turn will likely drive the air-launched Falcon to fewer than the nine Merlin kerosene-fueled engines SpaceX uses in its ground-based first stage. King says those trade-offs are still being worked out, as is the timing for moving from unmanned payloads to crew vehicles.

“We’ve been providing Vulcan with a lot of information about what we believe the market to be, at least in the [Defense Department]/NASA world,” says King, a former director at Marshall. “Obviously, we don’t know as much about the commercial world or the tourism world, but we’re talking with them now about how we’re going to stand up the right kind of team to go do that.”

Dynetics has been under contract to Vulcan for almost a year and has some 40 employees on the project so far. SpaceX joined more recently, and the overall team is still working through details of how to progress toward its 2016 first launch.

“This is a development program, and development programs take five to seven years to get through,” King says. “A lot of that depends on funding and funding profiles and how well you do and how much existing technology you’re putting in place. I don’t think we’re developing any new technology here, but this is a very complex system that we have to optimize, and we have to optimize it just right to make it work and get the kind of payload capability that we need. We’ve got a lot of work to do, but we see this as a fairly typical development program.”

The result, he says, will be a Delta II-class launch vehicle able to compete with anything in that class worldwide. “Anything there and south of there—we’ll be taking a look at those markets,” King says.

Among the details still to be nailed down are where the Stratolaunch System will operate from. Potential sites include Florida’s Kennedy Space Center, Edwards AFB near Scaled Composites’ headquarters in Mojave, or Hickam AFB in Hawaii, Wentz says. The carrier will require a 12,000-ft.-long runway and the capability for fueling the two-stage liquid-fueled Falcon rocket.

While Rutan began sketching out such an air-launch system 20 years ago, he emphasizes that today he is retired and it is the younger engineers at Scaled Composites doing the detailed work.

Also yet to be determined is the venture’s revenue stream, says Griffin. “Initially, there is a thriving communications satellite market” for small comsats suitable for the Falcon. The Defense Department and NASA’s scientific community have similar needs.

“There’s also a huge demand for payloads produced by unskilled labor at home that would like to go into orbit,” Rutan jokes of humans eager to orbit the Earth.

Because satellites are the easiest payloads to launch, the companies that want to send them into orbit are most likely to be Stratolaunch’s initial paying customers, Griffin says. Spacecraft weighing up to 13,500 lb. will be carried by the unmanned Falcon.

“At some point, we will have the capability to loft up to six people,” Griffin says. Beyond the need to assure their safety during launch, the question arises as to what passengers will do once they are in space. One obvious answer is that they will be space tourists on missions lasting no more than a few days.

Griffin says it is too early to say whether the Stratolaunch can service the International Space Station, although Rutan says it is shameful that the U.S. no longer has the capability to carry its own astronauts to the station.

“It’s become more expensive to put people in orbit with the systems this country has [now] than it was in the very first year of the very first decade” of U.S. manned spaceflight, Rutan says.

“I believe there have to be several really big breakthroughs to make [spaceflight] more affordable and safer so we have access to orbit,” Griffin adds. “I believe using air launch may be one of several breakthroughs to do that.”

Asked if he would like to be among the first passengers, Allen demurred, saying he is inherently cautious—even if he is apparently willing to risk $200 million or more as the backer of Stratolaunch.