The problem came to light when a Propulsion Drive Electronics (PDE) control unit picked up a difference in pressures between the oxidiser and the fuel going through one of the ATV's four "propulsion chains".

BBC: NEWS | Science/Nature | Space truck orbits despite fault

The system is tiny but has a grand name - Warp Drive (Water Alcohol Resisto-jet Propulsion De-orbit Re-entry Velocity Experiment).

BBC: Strand-1 'phone-sat' ready for orbit

Conventional hybrids use mainly the gasoline engine for propulsion, drawing on the electric drive and batteries only occasionally to (impressively) improve gasoline efficiency.

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