The Space Reviewin association with SpaceNews

NSRC 2023

Stratolaunch illustration
Stratolaunch Systems plans to develop the world’s largest airplane to carry a version of SpaceX’s Falcon 9 rocket for launching medium-class payloads, including perhaps crewed spacecraft. (credit: Stratolaunch Systems)

Stratolaunch: SpaceShipThree or Space Goose?

Bookmark and Share

Take the billionaire cofounder of one of the world’s largest software companies. Add a recently-retired designer of many innovative aircraft and suborbital vehicles. Throw in a former NASA administrator, the president of a low-cost commercial launch company, and a former NASA center director who is now the vice president of a defense contractor. Season with several hundred million dollars in funding. What do you get?

“Since the success of SpaceShipOne, I have thought a lot about how to take the next big step: a private orbital space platform business,” said Allen.

To some, the above is a recipe for an innovative space transportation company, Stratolaunch Systems, which was formally unveiled at a press conference last Tuesday in Seattle. Stratolaunch proposes to develop an air launch system on a scale never before attempted, capable of launching medium-class satellites using a derivative of SpaceX’s Falcon line of rockets and a custom-designed aircraft larger than anything that has ever flown. While some were clearly awed by the concept, others have raised questions about whether the Stratolaunch system makes good technical or business sense.

The Stratolaunch dream team

In space circles, Microsoft cofounder Paul Allen is known as the person who funded development of SpaceShipOne, the suborbital vehicle built by Scaled Composites that won the $10-million Ansari X PRIZE in 2004. Allen had not been openly involved in space ventures after winning the prize, but recently dropped hints that he was getting back into this arena. “I’m just now considering a new initiative with that magical contraption I never wearied of sketching as a boy: the rocket ship,” he wrote at the end of his recent memoir, Idea Man. In interviews associated with the book’s release, he said he was “considering doing further initiatives” in space (see “Paul Allen’s past (and future) in space”, The Space Review, April 25, 2011).

On Tuesday at the Seattle headquarters of Vulcan Inc., the company he established to manage his various ventures, Allen disclosed what that “new initiative” was. The announcement of the press conference itself, curiously, was embargoed prior to the event: notices that went to the media several days beforehand about his “new space travel project” warned that the advisory was “for scheduling purposes only” and was not “intended for broadcast or publication.” Only about an hour before the press conference did the company release the news about this venture.

“With government-funded spaceflight diminishing, there’s a much expanded opportunity for privately-funded efforts,” Allen said. “Since the success of SpaceShipOne, I have thought a lot about how to take the next big step: a private orbital space platform business.”

That business, Stratolaunch Systems, will develop an air launch system on a scale much larger than anything previously attempted. At its heart is the largest airplane ever built: a twin-fuselage behemoth powered by six 747 jet engines and with a wingspan of over 117 meters (385 feet). The plane will carry aloft a shortened version of SpaceX’s Falcon 9 rocket, whose first stage will have four or five engines as opposed to the nine engines of the ground-launched version. That air-launched rocket will be able to place payloads—satellites and, perhaps later, crewed spacecraft—weighing up to 6,100 kilograms (13,500 pounds) into orbit.

“Stratolaunch will build an air launch system that to give us orbital access to space with greater safety, flexibility, and cost effectiveness,” Allen said. He didn’t disclose how much a launch by Stratolaunch would cost, but did say he expected to invest an order of magnitude more into this venture than he did in SpaceShipOne—which implies a development cost of around $300 million or more, as Allen mentioned in his memoir that he spent $28 million on SpaceShipOne.

Stratolaunch reunites Allen with Burt Rutan for the first time since SpaceShipOne. “When it surfaced that Paul wanted to do this, and wanted to work with us, it absolutely warmed my heart,” Rutan, who retired from Scaled earlier this year but will serve on the board of directors of Stratolaunch, said at the press conference. “This guy has been the absolutely perfect team member and customer to work for.”

“This is not a preliminary design at this point,” Rutan said. “This is not a sketch. It exists in hundreds of detailed drawings and it’s relatively close to building as soon as we can get a building big enough.”

Rutan is familiar with air launch from both SpaceShipOne and SpaceShipTwo, but he said last week he had been thinking about air launch concepts long before those suborbital projects. He said in 1991 he had been invited to join a small group of “pillars of the space business” to quietly examine air launch systems. At the time they were looking at concepts that involved modifying 747 aircraft. “I remember thinking, ‘Gee, that’s a stupid idea,’” he said. Any sort of large air launch system, he concluded, required a place designed specifically for that task.

While Rutan was hailed as the designer of the concept, he said that credit for the plane belongs to the team at Scaled. “I’m not the responsible designer. I’ve actually retired. I don’t show up at work any more,” he said.

The Stratolaunch plane is specially designed for air launch (and, potentially, for carrying other large cargos), but will take advantage of many existing technologies and components, like the jet engines and other components from 747s. “We’re using proven technology as the components,” Allen said. “It’s different from programs where you have to start from scratch.”

Stratolaunch is already starting work on the aircraft concept, including construction of a new hangar at the Mojave Air and Space Port in California large enough to accommodate the giant plane. “This is not a preliminary design at this point,” Rutan said. “There are detailed structural analyses, detailed CAD drawings… this is not a sketch. It exists in hundreds of detailed drawings and it’s relatively close to building as soon as we can get a building big enough.”

The plan is to start flying the plan in 2015, with the first launch of the system planned for 2016. Initially the company will go after launches of satellites, noting that its capacity is similar to that of the Delta II rocket now on the verge of retirement. “There’s a lengthy history in commercial, defense, and civil space markets for payloads in this payload class that we think this vehicle can address,” former NASA administrator Mike Griffin, another member of the company’s board of directors, said at the press conference.

Griffin noted that he has been critical of what he termed “so-called commercial efforts” that required support by government programs. That wasn’t the case here, he said. “I think the critical factors for any putative commercial space venture are the necessary financial wherewithal to sustain what will inevitably be a lengthy development process, relative to other typical market items, and the vision and the resolve to fly through the developmental failures which inevitably occur,” he said. “I think Paul Allen has demonstrated already, through his personal history, both of those qualities.”

Joining Rutan and Griffin on the company’s board are Gwynne Shotwell, president of SpaceX; and Dave King, the former director of NASA’s Marshall Spaceflight Center who is now a vice president of Dynetics. Scaled, SpaceX, and Dynetics (who will provide a “state-of-the-art mating and integration system” to attach the rocket to the aircraft) are all suppliers to Stratolaunch, and not investors, said Allen.


This combination of technical experience and financial support attracted a lot of largely laudatory attention from the industry and the general public. However, the project has generated skepticism from some quarters, not so much because of doubts about the team’s ability to develop the system, but instead about whether it made that much sense from an operational and business standpoint.

Much of that skepticism revolves around the aircraft itself, to which some have attached the moniker “Birdzilla” and others “Space Goose”, a play on Howard Hughes’s giant “Spruce Goose” plane that flew only once. Given the talents of Scaled and their record of innovation, there’s every reason to believe they can build what would be the world’s largest airplane. But at what cost?

Even Stratolaunch board members admit that air launch has both strengths and weaknesses. “I don’t know that it’s a better way” to launch payloads, Griffin said. “It has its pluses and minuses.”

Large aircraft come with large price tags: estimates of the development cost of both the Airbus A380 and Boeing 787 jetliners—both large aircraft yet significantly smaller than the Stratolaunch plane—are well in excess of $10 billion. Of course, those costs include setting up the infrastructure for manufacturing hundreds of thousands of similar planes, as well as costs particular to manufacturing and marketing passenger aircraft, neither of which would apply to Stratolauncher’s plane. However, can those costs be reduced to a level that fits into Allen’s suggested budget of $300 million? Given that the full SpaceShipTwo system, including the WhiteKnightTwo airplane and rocket motor, also has cost on the order of $300 million, it suggests Stratolaunch may need additional funding beyond Allen’s current commitment to complete development of the system.

There’s also the question of operational flexibility of the system. One advantage of air launch is that it allows a system to use many different airports. However, Stratolaunch’s requirement for a 3,650-meter (12,000-foot) runway, and a range of 2,400 kilometers (1,500 miles), will limit the airports it can fly out of and still reach a launch range (as the rocket apparently isn’t designed to be reusable, it will likely be limited to launches over open ocean.) Moreover, while air launch systems eliminate the need for dedicated launch pads and related infrastructure on the ground, Stratolaunch will still have some unique requirements, like a hangar large enough to accommodate the aircraft and boosters, and equipment to mate the rocket to the aircraft and the payload to the rocket. It’s little surprise that the press release announcing the company highlighted the Kennedy Space Center—which has a long runway in the form of the Shuttle Landing Facility and easy access to the Eastern Range for launches—as one potential site for the system.

Even Stratolaunch board members admit that air launch has both strengths and weaknesses. “I don’t know that it’s a better way” to launch payloads, Griffin said. “It’s an approach which offers some very substantial operational flexibility, much reduced range requirements, freedom from a lot of the limitations that come from launching with land-based ranges,” among other benefits, he said. He added, though, it has limitations, including difficulty accommodating payload growth given how much the aircraft can carry. “So it has its pluses and minuses,” he concluded.

Rutan added air launch has a bigger performance benefit for suborbital systems than orbital systems. “If you’re going to orbit, the performance advantage is only about five or ten percent,” he said. That small increase, through, justified the expense of building a carrier aircraft, though, he argued. “It’s a small advantage for going to orbit to air launch, but it’s in a world where a small advantage is actually big.”

Then there’s the case of the markets this system could address. Griffin said there’s a “thriving communications satellite market for small to medium-class communications satellites,” but a system like this, similar in performance to orbit to the Delta II, could likely launch only geosynchronous orbit communications satellites weighing no more than a couple thousands kilograms. Such satellites constitute only a very tiny fraction of the market, and Stratolaunch will have to complete with existing systems like Soyuz and Land Launch’s Zenit-3SLB for such missions.

On the government side, there is a more robust market from NASA and the Defense Department; Griffin estimated the demand at about a half-dozen payloads per year that previously flew on Delta II. However, by the time Stratolaunch enters service it will face competition from Orbital Science’s Taurus II (renamed “Antares” by the company last week), slated to make its inaugural launch in early 2012, as well as SpaceX’s own larger Falcon 9.

Gary Wentz, a former NASA Marshall official who is now the CEO of Stratolaunch, said he felt confident about the vehicle’s market. “We’ve done a market analysis and we believe that we will be able to offer an affordable solution for medium-class payloads,” he said at the press conference. He added he wasn’t concerned about competition from the larger Falcon 9. “From a SpaceX perspective, this is actually a complementary capability to their existing design,” he said.

“Someone, after all, is going to have to get behind SpaceShipThree,” Allen wrote at the conclusion of his memoir this year.

However, these questions have created speculation that there is a missing requirement—the need for rapid, even first-orbit rendezvous with a space station or other orbiting facility after launch, or even covert operations—that is driving the design towards this particular air launch solution. That’s especially the case given the limited success smaller air launch systems have had in the market: Orbital’s Pegasus system, which technically successful, has found limited interest in recent years, while other ventures, like Space Launch Corporation and AirLaunch LLC, failed to get off the ground.

It may be that Rutan, Allen, and others see this approach as a long-term solution for orbital human spaceflight, allowing flights from a somewhat wider range of facilities than current spaceports, and perhaps being safer than conventional vertically-launched spacecraft. Rutan hinted as much at the press conference when he mentioned there was “an almost unlimited number of payloads that are easily produced by unskilled labor at home”—that is, people. “I don’t think there’s any limit to the number of payloads that would be in that category.”

Is, Stratolaunch, then, in effect SpaceShipThree, the hypothesized orbital follow-on to SpaceShipTwo? Perhaps, if one believes the last line of Allen’s memoir, immediately after mentioning his rekindled interest in “the rocket ship”: “Someone, after all, is going to have to get behind SpaceShipThree.”