By Dr David Whitehouse
BBC News Online science editor
The world's first private spacecraft, SpaceShipOne, is an impressive feat of engineering - an advanced rocket and aircraft system that is fundamentally simple.
Yeager's Bell X-1 broke the sound barrier; SpaceShipOne should exceed Mach 3
Its importance is that it has been made by relatively small private companies not by the aerospace giants under government contracts, as has been the case with the other craft that have reached space.
SpaceShipOne uses a hybrid rocket motor which is a mixture of solid fuel (in this case a form of rubber) and a gas (nitrous oxide also known as "laughing gas").
The rocket has been built by SpaceDev and the rest of the soon to be spacecraft by Scaled Composites, a company with an impressive aerospace track record.
It was behind Voyager, which in 1986 became the first aircraft to fly non-stop around the world without refuelling.
Rocket-powered aircraft are nothing new. In 1947, Chuck Yeager became the first person to break the sound barrier in the rocket-powered Bell X-1 aircraft.
In 1963, the US X-15 rocket plane was dropped from beneath the wing of a B-52 bomber, firing its rockets to make a sub-orbital hop reaching 107km (66 miles) and "officially" entering space.
One engine, one pilot
SpaceShipOne is going for the Ansari X-prize worth $10m. Looking back, prizes have played a major role in spurring feats of aviation. The Ansari X-prize is just the latest.
In the early years of the last century, the UK's Daily Mail newspaper offered a series of aviation prizes including $50,000 for the first non-stop crossing of the Atlantic.
The first crossing was made by Captain John Alcock and Lt Arthur Whitten Brown.
They used a modified Vickers Vimy, a night-bomber with two powerful Rolls Royce engines. They flew 3,500km (2,170 miles) in 16.5 hours, crashing into a bog in Ireland.
Shortly afterwards, Winston Churchill presented them with Lord Northcliffe's prize.
Another challenge, another prize. In 1919, the Frenchman Raymond Orteig offered a prize of $25,000 for a non-stop flight between New York and Paris in either direction.
He said his offer was good for five years. No attempt was made. In 1926, he extended his offer and it was taken up by Charles Lindberg.
Many considered that a multi-engined aircraft was essential to fly the Atlantic, but Lindberg disagreed; maintaining that the more engines, the more was the risk of failure.
Yuri Gagarin: The first government-funded spaceman
One engine, one pilot, and a lightweight aircraft carrying extra fuel, was Lindberg's solution.
In 1927, the "Spirit of St Louis" was built in just a few months. It incorporated a 220-horsepower air-cooled 9-cylinder Wright J-5C "Whirlwind" engine. It was built to run for 9,000 hours - an impressive beast.
Two days before Lindberg set off two Frenchmen attempted to make the journey from Paris to New York. They and their aircraft were never seen again.
Lindberg achieved the landing at Le Bourget field after a 5,790-km (3,600 miles) flight in 33.5 hours.
Aviation records fell regularly over the next few decades but the next great leap, into space, required a technology other than the internal combustion engine or jet engine.
When the first astronaut - Yuri Gagarin - went into space on 12 April, 1961, he sat atop a converted intercontinental ballistic missile.
His Vostok A1 rocket was a modified SS-6 missile with an extra stage added. It was fuelled with liquid oxygen and kerosene developing a million pounds of thrust.
The X-15 set an altitude record of almost 108km
It needed so much thrust because Gagarin was to go into orbit. The first American in space - Alan Shepard on 5 May 1961 - was only going on a sub-orbital trip. His Mercury-Redstone 3 rocket produced 78,000 lbs of thrust - all he needed for a trip up to 186km (115miles).
When the space shuttle first flew into space in April 1981, it used a combination of liquid-fuelled rockets and two strap-on solid fuelled boosters. Together they developed an enormous 7.8 million lbs of thrust.
SpaceShipOne is a very different spacecraft from all that have gone before it. It is the first time that a manned spacecraft will have used a hybrid rocket motor and the first time a person has gone into space without government help.
A new era in spaceflight has arrived.