Should We Build Giant Planes to Launch Spacecraft?

January 20, 2012

Microsoft co-founder Paul Allen recently unveiled his plan for a giant six-engine cargo jet -- the biggest plane ever built -- which would carry rockets and spacecraft aloft and launch them from 30,000 feet into space. The idea is to provide a lower-cost private launch alternative to NASA's recently discontinued space shuttle program and the massive multi stage Space Launch System, which detractors complain will be too expensive. But when I saw the news reports, I couldn't help but think that somewhere -- in heaven, or perhaps an alternate dimension -- Howard Hughes is smiling.

After all, the artist mockups of the Stratolaunch, whose 385-foot wingspan will be longer than the length of a football field, bear an unmistakable resemblance to a giant cargo plane that the brilliant but bizarrely compulsive and mercurial Hughes built seven decades ago. I'm talking about the H-4, better known as the "Spruce Goose," an eight-engine prop-driven flying boat -- built out of wood because of wartime metal shortages -- that was envisioned as a way to transport troops and war materiel across the Atlantic during World War II without being vulnerable to Nazi submarine attacks. That project, alas, had an ill-starred history; Hughes perseverated on details such as finding the ideal location of cockpit gauges, and Germany surrendered before the H-4 was finished. After taking the giant plane aloft for a single test flight in 1947, the eccentric billionaire and aviator put it in storage and turned his attention to even more outlandish endeavors. (The latter included making one of the most ridiculously bad films of all time, The Conquerorin which John Wayne -- bizarrely miscast as Genghis Khan -- utters the immortal lines, "Come hither, Tartar woman. I take thee for wife!")

But as usual, I digress. The idea of airborne launch vehicles -- that is, using big aircraft as launching pads for space rockets -- goes back to the early days of space exploration in the late 1950s. NASA's X-15 rocket plane reached the edge of space with the help of a B-52 that carried it aloft and released it at 45,000 feet. In the 1980s, the Soviet Union contemplated attaching the Buran, a reusable spacecraft that was intended as the answer to the space shuttle, to the massive AN-225 Mriya, a giant cargo jet capable of carrying more than 100 tons of freight. (The program, alas, was shelved around the time that the Soviet Union collapsed, and efforts to privatize it were unsuccessful.) Here's a 1993 paper, written by undergraduate students at the University of Michigan's aerospace engineering program, describing an airborne launch vehicle that was intriguingly similar to the planned Stratolaunch aircraft, down to the 1.2 million- pound weight and the six engines. On a smaller scale, in the late 1990s, Orbital Sciences Corp. and partners developed the Pegasus booster, a rocket for transporting satellites into space, which was designed to be ferried aloft by a B-52 bomber. And as this recent MSNBC.com article details, the Pentagon's Defense Advanced Research Projects Agency is spending $164 million to investigate the notion of turning airliners into mobile launch platforms for surveillance and communications satellites.

Using an aircraft to serve as an airborne launch pad has some big advantages over launching a rocket from the ground. As private space pioneer Burt Rutan pointed out in an interview with Popular Mechanics, by ferrying an space rocket aloft and launching it at 30,000 feet, you can reduce the rocket's weight by 5 to 10 percent. That may not seem like much, but when you're trying to reach a speed of 17,500 miles per hour to break free of Earth's gravity and put a payload into orbit, every ounce is crucial. And because a trip into space would no longer require burning up a multi stage rocket, Allen is aiming to offer launch costs well below the current $30 million to $200 million price tag for putting a satellite into orbit. (The current price range comes from this Wall Street Journal article.)

Allen sees the Stratolaunch, which will be built by Rutan's Scaled Composites company and could begin launching manned spacecraft by 2021, as a solution to the embarrassing predicament in which the U.S. space program now finds itself. As Allen explained at a December news conference covered by CNET.com,

For the first time since John Glenn, America cannot fly its own astronauts into space. With government-funded spaceflight diminishing, there's a much expanded opportunity for privately funded efforts ...Today, we stand at the dawn of a radical change in the space launch industry. Stratolaunch will build an air-launch system to give us orbital access to space with greater safety, flexibility, and cost effectiveness, both for cargo and for manned missions.

Initially, the plan calls for the Stratolaunch to ferry the Falcon Heavy, a 120-foot-long two-stage rocket being developed by another private company, Elon Musk's Space Exploration Technologies. The latter reportedly will be capable of boosting 117,000 pounds of payload -- roughly the equivalent of a Boeing 737 loaded with passengers, luggage and fuel -- into a 120-mile-high orbit. Eventually, though, the Stratolaunch could propel powered manned spacecraft into orbit as well. At the news conference, Allen boldly predicted:

By the end of this decade, Stratolaunch will be putting spacecraft into orbit. It will keep America at the forefront of space exploration and give tomorrow's children something to search for in the night sky and dream about.

Before the Stratolaunch can accomplish any of those lofty goals, of course, it actually has to be built. But that may not be as big of a challenge as it might seem. The Stratolaunch apparently will utilize a lot of existing technology, including the same jet engines as the Boeing 747. And the aerospace industry has been looking for a while at the notion of building even bigger aircraft, such as Boeing's proposed Pelican, a massive 500-foot- wingspan prop plane that would be capable of hauling 1,400 tons of cargo at altitudes of 20,000 feet.

A bigger question is whether Allen will be able to control costs enough to compete economically with the "big dumb rockets" that have been the standard mode for putting satellites and astronauts into space for decades. Conceivably, he might also face competition from other, even more exotic ideas, such as the space elevator concept that I wrote about in this blog post back in 2008. One proponent of the latter technology, space scientist and entrepreneur Bradley Edwards, has estimated that the cost of transporting payloads into orbit could be reduced to as little as $100 a pound. And according to this recent New York Times article, Google's mysterious Google X lab, the clandestine skunk works where researchers explore outlandish notions as part of the search engine giant's quest for world domination, reportedly is looking into whether a space elevator might be feasible to build. That means Allen could face a powerful rival with even deeper pockets than his.

So what do you think? Is Paul Allen's giant aircraft for launching spacecraft a good idea? Express your opinion below.

Image Credit: Stratolaunch/Paul G Allen |