The Vigilante stiffened. Rose stared at them, confused. "What's that?" The Doctor turned to face her, his face white. "It's an extremely illegal type of ship. Even having the schematics for one is a direct violation of the Shadow Proclamation."
"Okay, so what's so bad about it?" Now the Vigilante answered. "Do you know how a conventional rocket works?"
"Yeah."
"Well, an L.F.L.A. ship works in much the same way, but instead of burning fuel to provide thrust, it pulls the energy out of absolutely every living thing around it. L.F.L.A. stands for Launch by Forced Life Absorption. It kills living beings to achieve take-off." He turned back to the Doctor. "What's the required intake for optimal thrust?"
"Thirteen point seven tetra-hertz."
"An engine that large would need to absorb...millions. Maybe more." The Vigilante's eyes widened. "That's their plan. Make the Romans build the ship, the set it off, and kill everyone. They remove all of the evidence. If the Descart activate that ship, every living thing in Rome will die."