How SpaceShipTwo Will Work

SpaceShipTwo is a descendant of the SpaceShipOne design. SpaceShipOne was the first privately designed and owned vehicle to fly into space and return. It did this twice within two weeks in 2004, fulfilling the winning criteria for the Ansari X-Prize, a $10 million contest intended to spur private spaceflight. It was designed by Scaled Composites, the company owned by Burt Rutan, and was funded by Paul Allen, one of the founders of Microsoft. (You can read all about the spacecraft in How SpaceShipOne Works.)

SpaceShipOne was flown to a high altitude while attached to a carrier plane, WhiteKnight. It then detached and fired its rocket, propelling it beyond Earth's atmosphere. After briefly climbing to an altitude of more than 62 miles (100 kilometers), the wings swiveled into a feathered position that allowed a safe and smooth re-entry into the atmosphere. The craft then glided down to land at an airport.

SpaceShipTwo will follow a similar flight pattern. It will be much larger than SpaceShipOne, however, with room for six passengers in addition to two pilots for redundancy (in case one pilot is incapacitated, the other can take over). The view will be visible through 17-inch (43-centimeter) windows. The carrier craft, WhiteKnightTwo, will be the largest all-carbon-composite aircraft in the world, with a wingspan of 140 feet (42.7 meters) [source: Space.com]. Powered by four Pratt and Whitney PW308A engines, WhiteKnightTwo will have two separate fuselages, with SpaceShipTwo suspended between them [source: Virgin Galactic]. Each White Knight Two fuselage will be identical to the interior of SpaceShipTwo, making it ideal for training.

Once WhiteKnightTwo carries the craft to 50,000 feet (15,240 meters), it will detach and fire its rocket. It will begin climbing immediately, shooting up for 90 seconds at more than three times the speed of sound. The apogee of the flight, or the point at which it's farthest from the Earth, is 110 kilometers (68.4 miles) above the surface of Earth. Once there, the wings will pivot into feathered position. At the relatively low speeds attained by SpaceShipTwo, re-entry into the atmosphere is pretty benign. Heavy heat shields aren't needed, and the design of the wings automatically slows and aligns the ship for proper re-entry by creating drag. The pilot is barely involved in that aspect. Once it drops down between 70,000 and 60,000 feet (21,336 and 18,288 meters), the wings are returned to their original position for the 30-minute glide back to Earth.

The entire flight will last two and a half hours. Passengers will spend four to five minutes in space (the international boundary between Earth's atmosphere and space is 110 kilometers, or 68.4 miles). Family members aboard WhiteKnightTwo will have the opportunity to watch the flight in person.

Next: how can you get a ride on this rocket?

Getting a ride on SpaceShipTwo isn't quite as simple as buying a boarding pass at the Virgin Galactic ticket counter. The first thing you'll need is a fair amount of money. For the foreseeable future, each flight aboard SpaceShipTwo will cost $200,000. That amount is expected to drop if space tourist flights become a regular, successful venture. The first 100 passengers paid the full price as a deposit, while others on the waiting list paid smaller deposits. These deposits amounted to $30 million in funding for the design of the spacecraft [source: Space.com]. Virgin Galactic claims to have more than 80,000 people signed onto a list of potential spaceflight customers.

When the design for SpaceShipTwo was unveiled in January 2008, it was 60 percent complete. A rigorous series of tests are scheduled to begin in the summer of 2008, and the company hopes to begin commercial flights in 2009. Even if Virgin builds several additional SpaceShipTwo spacecraft (they plan to build five of them in the first few years), those who are on the end of that list could face a wait of several more years before they get their chance to experience space.

Once someone's flight is scheduled, he or she must undergo a medical examination. Virgin Galactic reports that the health requirements won't be especially stringent (saying, "We are making every effort to make space travel as inclusive as possible"), but those with health issues that could put them at risk during flight won't be permitted on the flight [source: Virgin Galactic].

The training regimen for SpaceShipTwo's passengers is still being developed, but will likely include zero-g training and centrifuge training to simulate the g-forces of the rocket burn and re-entry. During the 90-second rocket burn into space, passengers will experience three to four times the force of gravity. During re-entry, they could endure up to six gs for a briefer period. Passengers will also train inside the cabins of WhiteKnightTwo, which duplicate SpaceShipTwo's interior exactly. Virgin hopes passengers will therefore be better able to enjoy their journey since they'll be in more familiar surroundings.

The current safety statistics of manned spacecraft, while admirable for cutting edge technology, aren't acceptable for commercial passenger service. SpaceShipTwo is being designed to reach the safety levels of early 1920s airlines [source: Space.com]. Traveling into space will probably never be routine or perfectly safe, but Virgin Galactic is trying to make it as safe as possible. For example, pressure suits will be available for each passenger in case of emergency. The leading edges of some wing surfaces are covered with ablative thermal protection material -- without it, Scaled Composites believes the craft would survive re-entry, but not without damage [source: Aerospace America Online].

We'll have all the available technical details about SpaceShipTwo in the next section.

SpaceShipTwo will be 60 feet (18.3 meters) long with a wingspan of 27 feet (8.2 meters) and a tail height of 15 feet (4.6 meters). It's about twice the size of SpaceShipOne [source: Virgin Galactic]. The passenger compartment will contain six seats and will be 12 feet (3.7 meters) long and 90 inches (228.6 centimeters) wide [source: Virgin Galactic]. Virgin Galactic plans to make the cabin area as comfortable as possible. It will be pressurized, allowing the passengers to breathe normally without masks or pressure suits (known as a "short-sleeve environment"). Windows in the passenger compartment will be 13 inches (33 centimeters) wide by 17 inches (43 centimeters) tall. The pilots' windows will be 21 inches (53.3 centimeters) wide.

The exact lifting capacity of the carrier craft hasn't been revealed, but it will be greater than the weight of SpaceShipTwo. This means that it could have the capability to carry larger vehicles or unmanned satellite launching rockets for high-altitude launches.

Carbon fiber panels sandwiched around a honeycomb core will give SpaceShipTwo remarkable strength for its weight. Power is provided by a hybrid rocket based on the rocket used in SpaceShipOne. A hybrid rocket burns solid fuel (in the case of SpaceShipOne, a synthetic rubber) with the aid of a liquid accelerant, in this case nitrous oxide. The liquid is stored under pressure, so no fuel pumps are needed. Overall, hybrid rocket systems are considered among the safest types of rockets. They can be throttled down or shut off by cutting the supply of liquid oxidant.

Few details of SpaceShipTwo's systems have been released, but it's assumed they'll be similar to those used by SpaceShipOne. There will be no autopilot or computer control -- the pilots will directly control everything through mechanical and electric-assist controls. Thrusters in the nose are used to alter pitch and yaw when outside the atmosphere, and the wing pivots are pneumatically powered. Navigation is handled by a GPS-enabled LCD screen that displays SpaceShipTwo in relation to a simulated globe [source: American Aerospace Online].

Specifications for the craft's fuel are unknown. However, Richard Branson is dedicated to green technology and claims SpaceShipTwo will generate about as much pollution as a business-class flight in a conventional airplane [source: Space.com].

For more articles on space tourism and other cool space stuff, see the next page.