NASA has had to delay the launch of the Antares private spacecraft following the premature disconnection of a second-stage umbilical.

Thankfully, it wasn't a catastrophic launch failure. Antares has missed its launch window, and will need 24 to 48 hours to be returned to “nominal state”, and at the time of writing, NASA was still trying to understand what caused the umbilical to separate from the upper stage while launch preparations were taking place.

Antares, a private launcher built by Orbital Sciences, was to launch from the Wallops Flight Facility for its inaugural flight. The A-ONE mission is the first of two Antares demonstration missions scheduled for 2013 to demonstrate the launcher's ability to service the International Space Station; presuming that A-ONE is successfully rescheduled, a second launch later in the year will complete the demonstration schedule.

Once proven, Antares is scheduled for eight ISS resupply missions during 2013 under a $1.9 billion contract.

NASA says that the umbilical separated around 12 minutes before the preferred launch time, which “immediately led to a scrub of the launch attempt for the day”.

Close-up of the troublesome umbilicals. Source: Nasaspaceflight.com

Antares uses components from a variety of suppliers: its tank assembly and fuselage come from the Ukraine, and its motors were built to power Soviet lunar launches before being bought as a job lot of 30 by Aerojet, which has rebuilt the NK-33 motors as its AJ26 rockets.