"We want to make sure the average citizen can not only endure, but also enjoy a spaceflight," Vanderploeg said.
The FAA study is still underway, but Vanderploeg says preliminary results are promising -- contrary to what a lot of people thought.
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"For the most part, just about any medical condition that is well-controlled we think can fly safely," he said.
Those on the no-fly list including "individuals with significant heart disease that is not correctable either with surgery or medication and individuals who might have an aneurysm in their aorta we don't want to put through the stress of g-profiles," Vanderploeg said.
People who have mobility problems that prevent them from getting in and out of the vehicle without major assistance would be a challenge, he added.
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So far, about 630 people have signed up to ride on SpaceShipTwo, a six-passenger, two-pilot, air-launched vehicle now being tested at manufacturer Scaled Composites' facility in Mojave, Calif.