Graviton inverter

The graviton inverter was Professor Alice Dubrovnik's "life's work". Alice also referred to it as the judo drive, and the Twelfth Doctor described it as a jazz engine due to the shifting tempo it made. It turned gravitational force back in on itself, and prevented the Pollyanna from being "squished" by the Sun's gravity. After modifications were made to fight the Umbra were made, the Twelfth Doctor set up the final link to the graviton inverter on the hull of the Pollyanna, allowing Alice to briefly boost the inverter and create a secondary gravity envelope, which inverted the gravity and the heat by "just the right degree", freezing the Umbra on the ship to death. (COMIC: The Eye of Torment)