Virgin Galactic Crash- What led to the crash of Virgin Galactic LLC's experimental rocket ship? The incident has killed one pilot and seriously harmed another during a test flight in the Mojave Desert, California on Friday.

According to Carolynne Campbell-Knight, rocket propulsion expert at the International Association for the Advancement of Space Safety (IAASS), about four years ago she called the attention of Virgin Galactic to warn them about the use of nitrous oxide in its rocket ships.

Prior to the crash, Knight recalled she notified Richard Branson's company in 2009 or 2010 about their safety regulations after three engineers were killed in 2007 due to explosion. The accident happened during testing of the Virgin Galactic's prototype space tourism rocket engine on the grounds.

She adds the chemical compound could cause detonation anytime. "My view is from my own engineering experience which I shared with them - they obviously took the position that they knew better." Knight has urged the company to stop launching commercial space travel.

Some speculations from experts also reveal that the Virgin Galactic crash may have been caused by possible violent structural failure and not because of engine blast. Although the National Transportation Safety Board's investigation is just preliminary, they are focusing on the chance that aerodynamic forces were the reason for the death of one pilot and injuring another.

Virgin Galactic company could still conduct test flights while the investigation for the SpaceShipTwo crash is ongoing, says Christopher Hart, acting chairman of the National Transportation Safety Board. He also added that the investigation may take a year due to heavy documentations.

During the Virgin Galactic crash, the SpaceShipTwo split up after its take off. It readily killed 39-year-old Michael Alsbury and seriously wounded the co-pilot Peter Siebold, 43. Siebold has been reportedly 'alert' as he talks to his family and doctors.

Even after the Virgin Galactic crash incident, the company is still launching its second spacecraft which is under construction for the last three years. It is reported to be 65 percent done and will be ready for testing on grounds next year, George Whitesides, CEO of Virgin Galactic stated.