SpaceShipOne to SpaceShipTwo: A Bigger Leap Than They Thought?

I’ve been reading through a review copy of Dan Linehan’s fine book, “SpaceShipOne: An Illustrated History,” which the folks at Zenith Press kindly sent over to me. It’s a fascinating volume that includes more than 230 photos and illustrations chronicling every stage of the vehicle’s evolution. However, the most interesting illustration comes at the very end in the section that looks to the future.

The graphic shows SpaceShipOne to scale with its successor, SpaceShipTwo, and other well-known aircraft such as the Bell X-1, Spirit of St. Louis, and Boeing 747. The interesting comparisons are the ones between the X-1 and Scaled Composites’ two space planes.

SpaceShipOne and the X-1 are very similar in size and shape. The former is 28 feet long, the latter 30 feet. They both have the same bullet style design. The Scaled Composites craft has a number of enhancements – pivoting wings, a lighter airframe, and a more powerful engine – that allowed it to reach speeds and heights that Chuck Yeager could only have dreamed about. SpaceShipOne’s tiny cabin also had three seats instead of one – although it never carried more than a single pilot.

At 60 feet long and nearly twice as tall, SpaceShipTwo is a behemoth by comparison. It will carry two pilots and six millionauts in a spacious cabin with the same interior space as a Gulfstream IV corporate jet. Passengers will be able to float around during their five minutes of weightlessness, much people do on parabolic aircraft flights today.

That’s a big leap – maybe too much of a leap. Scaling up a small experimental rocket plane — and its carrier aircraft, the WhiteKnightOne — seems to have proven to be a bigger challenge than they thought. Larger airframes, more powerful engines, stronger landing gear…it’s all very complicated — and expensive.

A tragic explosion in July 2007 that took the lives to three Scaled Composites employees and injured three others lengthened the schedule considerably. Designer Burt Rutan has said that tragedy and subsequent investigation resulted in significant design changes for WhiteKnightTwo and froze SpaceShipTwo’s development for at least a year.

All these challenges help to explain why SpaceShipTwo has yet to fly even as we approach the fifth anniversary of its predecessor’s first flight into space on June 21. The new vehicle is not even close to carrying paying passengers; if a report this week out of Sweden is accurate, the first commercial flights may still be about two years away.

In addition to scaling and safety issues, Linehan’s book is an interesting question relating to SpaceShipOne’s development. It details a total of 17 test flights. Four were captive fights with the carrier aircraft; another seven were unpowered glide tests.

That leaves a total of six powered flights, only three of which flew suborbital. After Scaled Composites captured the Ansari X PRIZE on October 4, 2004, the company stopped flight testing completely. The only place SpaceShipOne now flies is in the Smithsonian.

Three suborbital flights doesn’t sound like a very large number for testing a new, all-composite vehicle in the harsh conditions of space. It seems as if you would want to ring it out a bit more at altitude before trying to build something much larger.

Of course, they’re going to fly SpaceShipTwo on suborbital test flights, but the design is based on something that flew didn’t fly in space very much. It makes you wonder whether problems will pop up that might have been identified with more testing of the prototype.

The decision to move on to SpaceShipTwo made sense from a commercial standpoint. You want to beat your rivals to market. You want to fly as many millionauts as possible to maximize your profits. And people paying 200 Gs for five minutes of zero G want to be able to float around, not stay strapped to their seats in a cramped cockpit.

All of these considerations dictated a significantly scaled up space plane. The question is whether it has proven to be too much of a leap forward. Time will tell.