Next HTV to ISS Is TBD


You may recall Japan's third H-II Transfer Vehicle (HTV-3) made an early and rather hasty retreat from the International Space Station (ISS) last fall when the unmanned cargo capsule executed an unplanned abort maneuver about one minute before it was supposed to begin the first in a sequence of departure burns.

Since then ISS Manager Michael Suffredini has explained the abort was triggered when HTV-3 detected an off-nominal trajectory that resulted when the station's Canadarm2 released the grapple fixture on HTV-3, causing friction as it backed away from the tug.

The abort maneuver sent HTV-3 speeding away from the space station at 1.2 meters (4 feet) per second rather than the much slower 8 feet per minute planned for the departure burn.

Although SpaceX's Dragon cargo capsule uses Canadarm2 in a different departure configuration thanĀ  HTV, the Orbital Sciences Corp. Cygnus vessel does not, which means the problem will need to be resolved before Cygnus flies. At the moment, the NASA consolidated launch manifest shows Cygnus making its first cargo run to the ISS in May.

In the meantime, NASA spokesman Joshua Byerly says the next HTV mission to the station has yet to be scheduled, though it is likely to occur this summer. So far he has not responded to questions about whether the friction problem has been resolved.

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