Thursday, May 7, 2015

How to Train Your Dragon

Click the arrow to watch the pad abort test. Video source: SpaceX YouTube channel.

SpaceX took one small step for a crash test dummy, but one giant leap for NewSpace, when it conducted a pad abort test Wednesday morning at the Cape's Pad 40.

The NASA press release declared the event “a successful demonstration” although according to a SpaceX pre-launch release the Dragon V2 may have come up short.

The release stated that Dragon at apogee would reach 1,500 meters. A tweet by SpaceX founder Elon Musk stated it reached only 1,187 meters.

Dragon V2 was projected to splash down about 2,200 meters off-shore but according to Musk it landed just 1,200 meters away from the pad.

At about the 16 minute 10 second mark in the above video, you can hear someone on the radio loop say “slightly below nominal.” at about 16:50, someone says, “Hang tight, everyone!” There's some speculation that the Dragon was drifting back to the shoreline due to easterly winds.

In a post-launch media briefing, Musk stated that one of the eight Super Draco thrusters had underperformed due to an abnormal fuel mixture ratio.

The thrusters use nitrogen tetroxide as on oxidizer and monomethyl hydrazine as a fuel. These are known as “hypergolic” in that they burn when mixed together without a heat source. N2O4 and MMH have been used for decades on space vehicles as the thruster propellant of choice, because in a vacuum no ignition source is required. The Space Shuttle orbiter used the same chemicals for its Reaction Control System thrusters and Orbital Maneuvering System engines.

The projected flight test trajectory and sequence of events. Click the image to view at a larger size. Image source: SpaceX.

According to James Dean of Florida Today, after an in-flight abort test this year at Vandenberg Air Force Base, SpaceX will send the Dragon V2 on an uncrewed demonstration flight to the International Space Station sometime in the next year and a half, if all goes well.

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