I'll repeat what several other people has have said this week: space is hard. Getting to space requires harnessing enormous energies with very light hardware. The Space Shuttle high pressure fuel pumps
each produced about 71,000 hp, equal to 15 large diesel locomotives, yet they were not much bigger than an automobile engine. They had a power to weight ratio of over 100 hp/pound: .5 hp/pound is typical for an automobile engine.
Ed Kyle puts it well:
Modern rocketry is a frightening balancing act. To accelerate from a dead stop to more than seven times faster than a rifle bullet in a few minutes, an orbital launch vehicle must create, contain, and endure extreme pressures, temperatures, and forces. All it takes to trip up the process is one loose connection, one small piece of sand or rust, a bad bit of metal or insulation, a misplaced bit in a control program, or an unexpected vibration.Suborbital is technically a lot easier. 2,500 mph is probably enough to reach space briefly on a suborbital flight, compared to about 18,000 for orbital. And six times the velocity requires 36 times the energy, and much better shielding on reentry.
SpaceShipOne had the enough volume and payload to carry three humans to at least 100 km in altitude. SS1 was less than four metric tonnes, fully loaded. It was launched from the White Knight One carrier aircraft, probably similar in mass fueled but not including the SS1 payload.
The closest orbital comparison is the Soyuz launcher and manned spacecraft, over 300 metric tonnes fully fueled and capable of carrying three humans to orbit and back. And that's for an expendable launcher, while SSI and WK1 were reusable except for the SS1 motor.
But. While suborbital space flight is technically a lot easier than orbital, its economics are far more challenging. Commercial satellites are so profitable that their owners are willing to pay tens of millions of dollars to get one launched. The most capable launchers can charge over $100 million for an orbital payload.
If Virgin Galactic fills six passenger seats on SS2 per flight at their announced price of $250,000, that's only $1.5 million. A brief suborbital flight measured in minutes is simply a lot less valuable than an orbital flight that can last as long as you have supplies for.
And building a reusable rocket plane capable of speeds in excess of Mach 2 is not a trivial task at all.
One that carries six passengers is even harder. SS1 had a theoretical capacity of only two passengers. The supersonic X-planes carried only a pilot.
Compare the Orteig prize to the Ansari X Prize.
The first offered a prize of $25,000 in 1919, worth about $340,000 in 2014, for "the first aviator of any Allied Country" to fly nonstop from New York to Paris, or vice versa. To win required an aircraft that could fly the required distance at about 100 mph. Lindbergh won, but there were several other entrants that could have won if history had been somewhat different. They included a Wright-Bellanca WB-2 and a Fokker C-2 Trimotor, both of which became successful commercial aircraft, although operating in an environment of subsidized mail transport.
Linbergh's plane was a unique variant designed for the stole purpose of winning the Orteig Prize, but still part of a successful family of Ryan monoplanes.
In contrast, when SpaceShipOne attempted the Ansari X Prize in 2004, there were no rivals remotely ready to fly, Building a rocket-powered airframe that can fly to the edge of space at over twice the speed of sound and return safely is much, much harder than flying nonstop from New York to Paris.
When only one company has shown that they can fly a reusable rocket capable of carrying passengers into space, if that company blunders in building their operational vehicle, there's no one to provide an alternative.
Yes, there's XCOR and their Lynx spaceplane. I wish them well, but they haven't flown it yet.
I believe the people responsible for SpaceShip Two have made at least major mistakes. The first was in making a jump to a spaceplane twice the size of the one that one went to the Smithsonian, instead of following it with a SpaceShip 1.1 for further flight tests followed by operational flights. The second is choosing and sticking to the immature technology of hybrid rocket motors.
I think it's fair to say that entrepreneurs like Branson are rather more prone to hubris than the average mortal. But it's a mistake to think that NASA administrators are quite free of hubris: pre-Challenger estimates of Space Shuttle reliability and the decision to launch Challenger in 1986 would both seem to qualify.
And government space agencies have their own unique failure modes: particularly, making important technical decisions influenced by jobs at stake in key Congressional districts, or the non-US equivalent.
I believe that some version of SpaceShip Two can be made operational, perhaps with significant modifications, and be relatively safe by the standards of dangerous pursuits like climbing Everest. Unless the investors lose faith in the project.
But remember: space is hard.