• Fly on both attempts in an orbit with a perigee sufficient for two full orbits and an apogee over 400 km (implying a perigee of at least 100 km)
• Carry a total of five crew and passengers. For the first attempt, flight of just test pilots and equivalent mass for passengers was allowed, but a minimum of five persons had to be aboard the second flight.

• Be able to dock with a Bigelow Aerospace inflatable space station
• Be capable of remaining docked to that station at least six months
• No more than twenty percent of the spacecraft mass may be composed of expendable hardware

• Be American in location and ownership
• Not use government funding to develop the spacecraft (except use of government test facilities was allowed)
• Be a private enterprise, without any government ownership

Even prior to Bigelow's announcment, Burt Rutan hinted that an orbital follow-on to his SpaceShipOne was being designed. Although no contestants were announced immediately, the X-Prize contestants listed were American and their designs had the technical potential for upgrade to an orbital spacecraft.

	Black Armadillo	X-Prize suborbital ballistic spacecraft concept of Armadillo Aerospace, Mesquite, Texas. Reached the stage of engineering tests by 2003.
	Crusader X	X-Prize suborbital ballistic spacecraft concept of Micro-Space, Inc of Denver, Colorado.
	Eagle X-Prize	X-Prize suborbital ballistic spacecraft concept of Vanguard Spacecraft of Bridgewater, Massachusetts.
	LB-X	X-Prize suborbital spaceplane concept of Kelly Space & Technology, San Bernardino, California.
	Liberator	X-Prize suborbital ballistic spacecraft concept of HARC, Huntsville, Alabama.
	Lucky Seven	X-Prize suborbital ballistic spacecraft concept of Acceleration Engineering, Bath, Michigan.
	Mayflower	X-Prize suborbital seaplane-spacecraft of Advent Launch Services of Houston, Texas. Reached the stage of engineering tests by 2003.
	Michelle-B	X-Prize suborbital ballistic spacecraft concept of TGV Rockets, Bethesda, Maryland. As of 2005, flight testing of the Michelle-B was expected to begin no earlier than 2007.
	Pioneer XP	X-Prize suborbital spaceplane concept of Pioneer Rocketplane, Solvang, California. No backing forthcoming.
	Rubicon	X-Prize suborbital ballistic spacecraft concept of STC.
	Solaris X	X-Prize suborbital ballistic spacecraft concept of Interorbital Systems of Mojave, California.
	The Space Tourist	X-Prize suborbital flying saucer concept of Discraft Corporation of Portland, Oregon.
	The Spirit of Liberty	X-Prize suborbital ballistic spacecraft concept of American Astronautics Corporation, Oceanside, California.
	Tier Two	After the successful win of the X-Prize for the first suborbital flight by Burt Rutan's Tier One / SpaceShipOne, the designer hinted a follow-on orbital spacecraft was being designed. No details were forthcoming... the enlarged SpaceShipOne/Tier One planned for commercial suborbital flights was dubbed Tier 1b.