With the NASA Space Shuttle retired in July 2011, several different companies have been competing to become NASA’s choice for cargo and crew transportation to the International Space Station, and possibly beyond. In 2006 and 2009, NASA awarded the SpaceX company two contracts totalling more than $2 billion, paving the way for the Dragon capsule to complete its first successful orbit and re-entry in December 2010. 18 months later, on 25 May 2012, the Dragon capsule fulfilled its goal of docking with the ISS on only its second ever demonstration flight.
Powered by a combination of solar panels and an advanced lithium battery, the Dragon capsule is large, with a cargo capacity of almost 10 metric tons. When it becomes human-rated, possibly in the next couple of years, it will able to transport up to seven crew members into orbit. The capsule uses 18 liquid fuel thrusters equipped with nitrogen tetroxide and monomethyl hydrazine to manoeuvre while in orbit. Like NASA’s Orion spacecraft, the conical shape of the Dragon capsule is deemed the best for Earth re-entry, while also allowing for a sizeable interior.
One of its defining features is a variant of NASA’s phenolic impregnated carbon ablator (PICA) heatshield. SpaceX’s PICA-X heatshield advances on NASA’s design in a number of places, notably its significantly reduced cost and added reusability, allowing it to be used hundreds of times, whereas NASA’s currently does not survive its flight. This shield protects the capsule as it re-enters Earth’s atmosphere at several thousand degrees centigrade and keeps the interior close to room temperature.
Three oversized parachutes slow its descent to Earth, although it can operate on only one if the other two happen to fail. However, while the capsule must land in water for now, SpaceX hope to eventually develop thrusters that will one day allow the Dragon capsule to land on the ground as well.
There’s certainly no lack of ambition of SpaceX. Following their successful docking of the Dragon to the ISS, they are pushing on with their 12 contracted cargo flights to the space station, with the next flight scheduled for October this year. They are also continuing to work on the Falcon Heavy rocket, a much larger version of the Falcon 9 rocket that currently takes Dragon into orbit. With a cargo capacity of over 50 metric tons, Falcon Heavy will be the world’s most powerful rocket. It could launch on a test flight as early as next year, further cementing SpaceX’s place as the major pioneer in this new era of private spaceflight.
Images courtesy of NASA and SpaceX.
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