A crowd of engineers, dignitaries and space enthusiasts gathered inside a hangar in the Mojave Desert in California for the unveiling of WhiteKnightTwo "Eve".
Virgin Galactic has contracted the innovative aerospace designer Burt Rutan to build the mothership and spacecraft at his Scaled Composites factory in California.
But some hurdles remain before Virgin Galactic customers can experience zero gravity.
WhiteKnightTwo must undergo a rigorous flight testing programme, beginning in the autumn.
The mothership is a white, four-engined jet designed to cradle SpaceShipTwo under its wing and release it at 50,000 feet (15,200m) in the air.
Once separated, SpaceShipTwo will fire its hybrid rocket and climb some 60 miles (100km) above the Earth.
Engineers still need to finish building SpaceShipTwo, which is now about 70% complete, according to Virgin Galactic.
Sir Richard said the name of the WhiteKnightTwo reflected the pioneering spirit of his space tourism venture.
"We are naming it Eve after my mother, Eve Branson, but also because it represents a first and a new beginning, the chance for our ever-growing group of future astronauts and other scientists to see our world in a completely new light," he said.
Rutan and Branson have high hopes for WhiteKnightTwo, and its carbon composite technology, that go beyond merely lofting SpaceShipTwo to its launch altitude.
Scaled and Virgin have set up a new joint venture, called The Spaceship Company, which will exploit the wider capabilities of the aircraft.
Richard Branson on the likely timetable for space tourism
The capabilities of this mothership are unbelievable," Sir Richard told the BBC. "For instance, we could put satellites in space at a fraction of the price that satellites are currently put up there. It has enormous weight capability, so if there were a [humanitarian] crisis in Africa it could carry enormous loads [for aid]."
SpaceShipTwo should be finished in about a year's time. Sir Richard said he intended to take his family into space but would not fly them until a thorough testing programme had "been completed and every box has been ticked".
Longer-term, Sir Richard envisages many tens of thousands of people taking holidays in space.
"Let's go 20 years forward, if all of this goes to plan, I hope that we will have a hotel in space; and in that hotel I hope we will have small spaceships that can go around the Moon - an excursion," he explained.
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