Elon Musk's goal of achieving the first powered landing of a reusable booster had a close brush with success today as a SpaceX Falcon 9 rocket narrowly failed to survive a touchdown on the deck of a drone barge off the US east coast. The third landing attempt by the company came after the launch of the CRS-6 mission, which sent an unmanned Dragon cargo spacecraft to the International Space Station (ISS).
CRS-6 lifted off at 4:10 pm EDT from Launch Complex 40 at the Cape Canaveral Air Force Station, Florida, after its original Monday launch time was cancelled due to bad weather. According to SpaceX, the launch went off without incident with the first stage separating three minutes into the flight, the second stage separating at the ten-minute mark, and the solar array deployment at 12 minutes.
Meanwhile, the first stage Falcon 9 booster executed a series of engine burns that sent it back into the atmosphere, steered it toward the drone barge called "Just Read the Instructions," and slowed it down from hypersonic velocity before making a landing attempt.
In a series of tweets, SpaceX founder and CEO Elon Musk confirmed that the Falcon 9 touched down unsuccessfully on Just Read the Instructions in the Atlantic Ocean. "Ascent successful," tweeted Musk. "Dragon enroute to space station. Rocket landed on drone ship, but too hard to survive."
He subsequently amended this, saying: "Looks like Falcon landed fine, but excess lateral velocity caused it to tip over post landing."
In later tweets, Musk compared the maneuver to a lunar lander, but one operating in six times the Moon's gravity. He also speculated that either there was not enough thrust in the nitrogen thrusters on the top of the rocket to keep it upright or a landing leg failed. The exact cause, he added, will be known when more data is available.
Today's launch is the sixth of at least 12 commercial missions by SpaceX to the ISS. The Dragon is carrying 4,300 lb (1,950 kg) of supplies and payloads, including the first espresso machine in space, as well as critical materials for 40 scientific experiments. The cargo ship is currently executing a series of orbital corrections to align it with the space station and is scheduled to rendezvous in about two days. It will stay at the ISS for about five weeks before returning to Earth for a parachute-assisted splashdown off the coast of southern California.
The SpaceX video of the CRS-6 launch is below.