Crew Compartment

SpaceShipOne has a space-qualified environmental control system (ECS). Its pressurized cabin has room to fit three people. The pilot sits up front in the nose, and behind him and up against the pressure bulkhead is a row of two seats for the passengers.

The pilot and the passengers sit upright but slightly reclined, as shown previously in figure 4.5. This helps them tolerate the g-forces they face during the boost and reentry phases of the mission. They do not have to wear spacesuits or g-suits, but SpaceShipOne has an oxygen system with oxygen masks for them to wear.

The backseat row is less than 2 feet from the oxidizer tank, but the pressure bulkhead separates the cabin from the oxidizer tank and the rest of the rocket engine. The dome shape of the pressure bulkhead is necessary. “These shapes are real important as pressure vessels,” Rutan said. “And it is pressurized all the way to the nose. There is not another bulkhead up in front.”

For test flights, the pilot pressurized the cabin to 4,000—6,000 feet (1,220—1,830 meters). An airliner sets the pressure inside its cabin to about 8,000 feet (2,440 meters). This means that no matter how high or low it flies, the passengers inside will always feel a pressure equal to what they would feel if they were standing on a mountain with a height above sea level of 6,000 feet (1,830 meters).

The cabin was sealed but did have a small amount of leakage. The pilot watched the cabin altimeter, which was used to measure the cabin pressure, and manually adjusted it as necessary.

SpaceShipOne does not have its own heating or cooling system. During captive carry, however, the vehicle was heated by bleed air from White Knight’s engines, which pumped the hot air to the pressure bulkhead. The cabin temperature did not change by more than 15 to 20 degrees Fahrenheit from the time the door was closed on the ground. Again, the short duration of the mission really played to Rutan’s design principles of simplicity and low construction cost.

At low altitudes, the pilot could get fresh air by opening two 4-inch (10-centimeter) plugs located on either side of the fuse­lage. Similar to the design of airliner doors, the plugs open inward and are beveled, like corks, so that the high pressure inside the cabin helps keep them closed tight and prevents opening at high altitudes. “You didn’t need cooling,” Doug Shane said. “You could keep the airplane cool on the ground with the [external] air con­ditioner. Once you took off, you could wait to put the plugs in until you were at 10,000 to 12,000 feet [3,050 to 3,660 meters], where it is pretty cool.”

The plug on the pilot’s right-hand side has a safety pressure relief valve that could be capped in case it failed. The other plug has a manual ball valve that opens to dump the pressure in the cabin if necessary. This plug also has a big tab riveted to it. In an emergency situation where the crew would have to bail out, they would have to wait for the cabin to depressurize through a small valve. The tab provided the leverage so the pilot could peel off the plug fast, allowing the cabin to rapidly depressurize. Once SpaceShipOne was all sealed up, it was essentially a trapped volume of air. “There’s no exchange of air. So you’ve got to be concerned about humidity and carbon dioxide,” Shane said.

A second hose coming off each oxygen mask collected the exhaled air in order to control the carbon dioxide (C02) levels and humidity. The exhaled air was dried, and a scrubber using an absorbent material was used to remove excess C02. But because of the mission’s short duration and the fact that the cabin was sealed off from the atmosphere

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Fig. 4.11. Looking from underneath into the engine bay, these are the two main spars running perpendicular through the fuselage, one in front of the oxidizer tank and one behind it. These provided the structure to support the fixed and movable sections of the wings. Mojave Aerospace Ventures LLC, photograph by David M. Moore

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Fig. 4.12. SpaceShipOne’s wings had to be very rigid and strong because they not only supported the tail booms and feather mechanism, they also had to withstand the very high forces encountered during boost and reentry. This photograph shows how thick the ribs inside had to be. Mojave Aerospace Ventures LLC, photograph by David M. Moore

V__________________________________________ J for a relatively short time, little C02 buildup occurred, and makeup oxygen (02) was not necessary.

“We actually demonstrated on White Knight that we had adequate control with three people on board for a three – or four-hour flight,” Shane said. “We knew it would be fine for one hour.”