ISS ammonia leak may require spacewalk for repair

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An ammonia leak aboard the International Space Station (ISS) threatens to disrupt an electrical channel that may require a spacewalk to repair.

The ammonia leak was spotted on 9 May in the form of frozen ammonia flakes drifting away from the P6 Truss. Ammonia is used as a heat exchanger, dissipating heat generated by the solar arrays and machines running on the ISS.

The leak is caused by a rupture thought to measure between 1-3cm (0.39-1.18in), and originates from the P6 Truss.

One of the eight electrical channels, Channel 2B, has been shut down, and power rerouted through other channels, causing the loss of 12.5% of the station's electricity-generating capacity.

A small rupture in the same area has been slowly leaking ammonia. But the loss is in such small quantities that it is considered safe, requiring only an occasional fill-up. That leak expanded in 2012, requiring a spacewalk to install a spare radiator. The new, larger leak appears to originate from the same area.