By Dr. Gary L. Deel, Ph.D., J.D.
Faculty Director, School of Business, American Military University
This is the third article in a four-part series on the history of spaceplanes and modern iterations of spaceplane technology.
SpaceShipTwo is a craft originally developed by a company called Scaled Composites, but it is now under the ownership of The Spaceship Company, a subsidiary of billionaire Sir Richard Branson’s Virgin Galactic.
When discussing SpaceShipTwo, one really must also discuss WhiteKnightTwo, the mothership which carries SpaceShipTwo before its ascent into space. This combination of aircraft and spacecraft was designed to eliminate some of the inefficiencies with the one-vehicle design.
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For example, as discussed in the previous article, the XCOR Lynx lacked any propulsion other than rocket motors, so it had to be towed onto the runway before flights. It also had to carry enough fuel to make the entire ascent into space on its own. With the WhiteKnightTwo-SpaceShipTwo marriage design, limitations like these were overcome.
SpaceShipTwo is a small, single-hull space plane capable of seating six passengers and two pilots. It sports a single liquid rocket engine powered by hydroxyl-terminated polybutadiene (HTPB). When it is ready for flight, , which is essentially two airplane fuselages with one long wing connecting them and powered by four conventional jet turbine engines, two on each outer wing. SpaceShipTwo is hung between the two fuselages.
WhiteKnightTwo Takes Off Horizontally like a Normal Airplane Using its Jet Engines
For flight, WhiteKnightTwo takes off horizontally like a normal airplane using its jet engines. Then, when it reaches an altitude of approximately 15 km (9 mi), SpaceShipTwo detaches from WhiteKnightTwo and ignites its rocket engine. Even though the rocket engine only burns for just over a minute, the space plane reaches supersonic speeds in just eight seconds.
After engine cutoff, the space plane coasts to its apogee, just like the XCOR Lynx. However, SpaceShipTwo has reached altitudes as high as 112 km (69.5 mi), more than 10 percent higher than the Kármán line. Although the total trip is estimated to last two and a half hours, the few minutes of weightlessness in space would be about the same as that which was projected for the flights on the XCOR Lynx. Passengers would experience four Gs to five Gs of force during ascent and reentry, also similar to the Lynx.
SpaceShipTwo Has a Unique and Interesting Design called a ‘Feathered’ Re-Entry System
When SpaceShipTwo is ready for descent, it has a unique and interesting design called a “feathered” re-entry system. What this means, essentially, is that the rear wing assembly of the rocket articulates vertically at a hinge-point about midway in the fuselage of the plane. This allows the wings to tilt upward and the hull of the plane to tilt back, exposing the flat underbelly of the plane for atmospheric drag.
Through this innovative design, SpaceShipTwo is able to naturally adjust the amount of atmospheric deceleration it experiences based on the amount of drag on the craft itself: With more air resistance, the plane naturally orients into a glider position, but with less air resistance the feathering wings articulate up and allow the belly of the plane to drop down to increase drag. At about 24 km (15 mi) in altitude, after the plane has descended into the density of the atmosphere, the feathering wings lock back into the fixed glider position, and the craft descends to a normal runway landing.
The feathering system also has the apparent benefit of natural stability control. Virgin Galactic has stated that SpaceShipTwo pilots don’t have to actively steady the craft on re-entry with any kind of rudder or flaps because the feathering system has a shuttlecock-style stabilization effect that ensures the craft will always maintain a proper orientation. According to its designers, the plane could conceivably re-enter the atmosphere at any angle — from a straight nose dive to the most gradual descent — and any orientation, even upside down, and the feathering system will ensure the craft rights itself.
However, the feathering re-entry system would not be a workable model for orbital craft because of the significantly higher speeds at which they would collide with the atmosphere. In fact, in late 2014 the first iteration of SpaceShipTwo, the VSS Enterprise, broke up in flight and one of the two pilots was killed in the crash. A premature deployment of the feathering system while the craft was still on its powered ascent is believed to have been responsible for the in-flight failure. This seems to be real and tragic proof that the feathering system has its vulnerabilities.
SpaceShipTwo’s original design was estimated to cost around $108 million in 2007. However, as of 2011 the total investment in the space plane had eclipsed $400 million. That is in addition to the $200 million+ spaceport that was built in New Mexico to be the exclusive launch site for Virgin Galactic’s commercial space tourism flights. The spaceport was partially funded by the New Mexico state government.
Delays Haven’t Tempered Interest from the Public for Space Tourism
When development began on SpaceShipTwo, Virgin originally estimated that commercial flights would begin as early as 2014. Obviously that did not happen. However, the company has the strong financial backing of Richard Branson, one of the world’s wealthiest entrepreneurs, and these delays haven’t tempered interest from the public for space tourism.
In 2007, Virgin Galactic had already received payment in full of the $200,000 ticket price from 200 eager enthusiasts. Six years later in 2013, that number had grown to nearly 600 would-be space passengers. Virgin has since increased the ticket price for new reservations to $250,000, and new bookings still seem to be rolling in.
The company’s January 2020 update about the new SpaceShipTwo vehicle “said nothing about the status of VSS Unity,” SpaceNews reported. “That vehicle made its last suborbital test flight in February 2019, after which the company said it would then outfit the spacecraft’s cabin for commercial flights and make other upgrades.”
In the final article, we will look at the Sierra Nevada Space Systems Dream Chaser spaceplane.
About the Author
Dr. Gary Deel is a Faculty Director with the School of Business at American Military University. He holds a J.D. in Law and a Ph.D. in Hospitality/Business Management. Gary teaches human resources and employment law classes for American Military University, the University of Central Florida, Colorado State University and others.