Jim Oberg wrote:

"Even if the engines never work, they are only a backup to propulsion
capability usually provided by visiting vehicles docked to the aft port," he
explained in an e-mail. "The loss of these engines has no impact on station
operations - the Russians were just curious if they would work after so
long, and they have their answer."

Losing a backup system has always got to be a Bad Thing (although Mir
spent nearly its entire life in the same situation, but for a different
reason).

It makes you wonder what other long-term dormant systems no longer work.
The failure of P6's array extension/retraction system would be extremely
bad, for example.

--Chris