Hundreds of budding astronauts have signed up for a $2366-a minute flight that billionaire Sir Richard Branson is promising will be a ride of a lifetime

Branson said that while the flight was "bloody expensive" he hoped to get the price down as more missions were launched.

Eight New Zealanders are among 800 people who have signed up for the two-and-a-half hour flight that will cost US$250,000 (NZ$355,000).

Six passengers will ride in the Virgin Galactic craft at a time.

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Branson told a fundraising dinner he hoped his space ship would be ready for test flying to the outer atmosphere later this year and able to take passengers up some time next year.

Passengers would be weightless for a time during the flight which blasts about 114km into inner space.

During the ship's launch it would accelerate to nearly 5000kph in 7.5 seconds.

He said the programme had taken twice as long as originally thought and had suffered a major setback when co-pilot Michael Alsbury was killed in a crash in 2014.

Branson told about 2000 guests at Vector Arena in Auckland last night that the programme was back on track following the accident involving "brave" test pilots.

He hoped to launch paying passengers further into space in craft capable of orbiting the earth at some time in the future

Virgin Galactic's plan is to use two aircraft to get customers into space. WhiteKnightTwo is a double-hulled plane that resembles a catamaran that carries a smaller space craft SpaceShipTwo to about 50,000 feet.

When at that altitude the smaller craft drops from WhiteKnightTwo, fires a rocket that sends it to the edge of the atmosphere and those on board are weightless for several minutes.

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A feathered tail system that Branson likened to a badminton shuttlecock is deployed and SpaceShipTwo coasts down to earth and lands like a glider.

Branson said he would be on the first commercial voyage.

He is also working on a separate rocket programme to launch about 2500 satellites into orbit to improve internet connectivity around the world.

This would put him in competition with New Zealand-founded Rocket Lab which he said was a ''friendly rival.''

Branson 's wealth has been put at $7.12 billion by Forbes.