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The sign by the Descent Propulsion System engine. It reads

NASA Lunar Module Descent Engine

This engine was attached to the lower portion of the Apollo Lunar Module (descent stage). Once the Lunar Module (LM) had undocked from the Command Module (CM), the engine was fired to slow the LM and place it into a trajectory towards the lunar surface. Engine thrust could be varied (throttled) by the astronaut pilot to ensure a safe landing. Weighing only 1,600 Newtons (370lbs) on Earth, this engine could generate enough thrust to hover the 160,600-Newton (36,100-lb) LM much like a helicopter prior to touchdown, tanks to the moon's reduced gravity (one-sixth the gravity of Earth). To increase reliability, the engine used hypergolic propellants, which ignite on contact with each other. This eliminated the need for ignition systems, which could fail at critical moments.

Thrust Range: 1,050-9,870lbs (4,670-43,900 Newtons)

Contractors: Space Technology Laboratories, Inc.