Virgin Galactic crash: Experts raise finger at use of 'unconventional, unstable fuel' to fire spacecraft

As 15 federal United States investigators started investigating the Virgin Galactic crash site in California's Mojave Desert, speculations are rife about the unconventional fuel propulsion used to fire the craft up to space.

The Virgin Galactic spacecraft used nitrous oxide and plastic fuel in contrast to the carbon-based fuels that have powered most rockets for decades, reported The Guardian.

Carolynne Campbell, a rocket engineer who is the lead expert on hybrid propulsion systems for the International Association for the Advancement of Space Safety (IAASS), described nitrous oxide as "benign" and "stable" but added that the gas caused an explosion in 2007 at the Virgin Galactic spaceport killing three workers.

Campbell said that the space tourism company was aware that three people were killed by "this stuff" and yet they continued to present it as "safe stable and benign."

Geoff Daly, a US-based British rocket scientist, who has been highly critical of the Virgin Galactic space tourism project, said that Nitrous Oxide is "still very poorly understood" in large quantities and that the temperature of the fuel is critical.

The SpaceShipTwo, which went down over Mojave Desert due to an in-flight breakup," was believed to be carrying 11,000-12,000 lbs of the gas.

Daly also claimed that there were "fundamental design flaws" in the rocket system whose delivery system was solid and the motor was bolted to the fuel tanks without any flexibility. Even a small amount of vibration could have resulted in the fracture and failure of the engine system, he said.

He had sent several emails to the Federal Aviation Authority (FAA) last year warning the organization of another disaster if test flights were approved.

Virgin Galactic's chief executive George Whitesides had earlier claimed in an interview that the new hybrid of nitrous oxide and plastic fuel had passed the crucial ground test and was undergoing the qualification tests to prove it would perform predictably.