SpaceX's Falcon 9 booster roared back into service today over four months after a disastrous launch pad explosion threw its future into doubt. At 9:54 am PST (17:54 GMT), the reusable rocket lifted off from Space Launch Complex 4E at Vandenberg Air Force Base, California carrying the 10-satellite constellation of the Iridium-1 mission. According to the company, this is the first of a series of launches that will eventually form the 81-satellite Iridium NEXT global communication network.

They say that once you fall off a horse, you should get straight back on, but for Falcon 9 getting back in the saddle only came after a four-month investigation into the cause of a catastrophic launch pad explosion on September 1. The accident occurred during a fuelling exercise when the supercooled liquid oxygen used in the second stage apparently interacted with the graphite fiber cladding of one of the helium bottles used for propellant pressurization. The oxygen froze and caused the cladding to fail or ignite, resulting in a catastrophic failure of the oxygen tank and an explosion that destroyed both the rocket and the Israeli satellite payload.

With the investigation completed about 12 days ago and FAA approval given for flight on January 6, SpaceX was cutting things fine, but the company has made it clear that it intended the Falcon 9 to return to service as soon as possible.

After lifting off from Vandenberg, the Falcon reached its point of maximum stress or Max Q one minute and nine seconds into the flight. First stage engine cutoff was at two minutes, 24 seconds with second stage separation three seconds later and second stage engine firing eight seconds after that.

After firing for six minutes and 34 seconds, the second stage shut down successfully and coasted on a southward trajectory until 52 minutes and 32 seconds into the flight, when the Merlin engine fired a second time for three seconds. About one hour into the flight, the first of 10 Iridium satellites were deployed with the last going into polar orbit at one hour and 14 minutes since lift-off.

Meanwhile, the first stage carried out a series of engine burns that returned it to Earth to make a powered landing on the "Just Read the Instructions" drone ship on station in the Pacific Ocean. At the six minute 57 second mark, the first stage made a reentry burn and guided itself through the Earth's atmosphere using a set of hypersonic vanes. At seven minutes and 45 seconds, a landing burn was initiated and the rocket touched down dead center on the sea barge at eight minutes and 15 seconds after launch.

The video below recaps the launch.

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