After the third consecutive launch failure of Falcon 1, SpaceX CEO and CTO Elon Musk promised they will achieve their goal eventually, and announced Falcon 1 Flight 4 was already in the making. That was less than 2 months ago, and on September 28 SpaceX reported its launch success with Flight 4 of the first privately developed liquid fuel rocket to orbit the Earth.

“This is a great day for SpaceX and the culmination of an enormous amount of work by a great team,” Elon Musk said in a statement. “The data shows we achieved a super precise orbit insertion – middle of the bull’s-eye – and then went on to coast and restart the second stage, which was icing on the cake,” he further explained.

Falcon 1 is a two stage, liquid oxygen and rocket grade kerosene (RP-1) powered launch vehicle. The Merlin engine, which powers Falcon 1 in its first stage, is based on a pintle style injector which was also used in the Apollo Moon program. This engine has been developed internally by SpaceX, but it is based on a formula that has been supporting space missions for years.

On September 28, at 4:15 p.m. (PDT) or 23:15 (UTC), Falcon 1 lifted off from the Reagan Test Site (RTS) on Omelek Island at the U.S. Army Kwajalein Atoll (USAKA) in the Central Pacific, and according to preliminary data, Falcon 1 achieved an elliptical orbit of 500 km by 700 km, 9.2 degrees inclination, just as planned.

On Flight 4, Falcon 1 carried a payload mass simulator of 165 kg (364 lbs), designed and built specifically for this mission, consisting of a hexagonal aluminum alloy chamber 1.5 meters (5 feet) tall. The payload remains attached in the second stage of the Falcon 1 mission, which is orbiting the Earth.

SpaceX is the winner of the NASA Commercial Orbital Transportation Services competition (COTS). Its mission is to conduct three flights of the Falcon 9 launch vehicle and Dragon spacecraft, which will culminate with Dragon’s berthing with the ISS.

According to the agreement with NASA, SpaceX will provide solutions for spaceflights to the International Space Station (ISS) after the Space Shuttle retires in 2010, as the only COTS contender with capabilities to return pressurized cargo and crew back to Earth.

In August this year, Falcon 1 suffered its third consecutive mission failure, after reaching an altitude of 217 km. According to SpaceX, a problem encountered after stage separation prevented the second stage from reaching the intended orbit.

The investigation on the matter revealed that the problem originated due to the longer thrust decay transient of the Merlin 1C regeneratively cooled engine, which had some unburned fuel in the cooling channels. This, combined with a small amount of residual oxygen, led to a thrust powerful enough to overcome the stage separation pusher impulse.

Despite all that, SpaceX engineers reported that the Merlin 1C engine had an excellent performance during the first stage. Furthermore, the second stage of Flight 3 ignited and achieved normal chamber pressure and the fairing separated correctly, which gave great hope for a successful Flight 4 attempt.

Nine minutes into the Falcon 1 Flight 4 mission, Falcon 1’s second stage engine shut down, and Falcon 1 became the first privately developed liquid fuel rocket to orbit the Earth. The success took even Elon Musk by surprise, as he promised he will return with a more complete post launch statement, “as right now I’m a bit of a daze and need to go celebrate.”