DI meaning in Space Science ?

A distributor is an enclosed rotating shaft used in spark-ignition internal combustion engines that have mechanically timed ignition. The distributor's main function is to route secondary, or high voltage, current from the ignition coil to the spark plugs in the correct firing order, and for the correct amount of time. Except in magneto systems and many modern computer controlled engines that use crank angle/position sensors, the distributor also houses a mechanical or inductive breaker switch to open and close the ignition coil's primary circuit.

The first reliable battery operated ignition was the Delco ignition system developed by Dayton Engineering Laboratories Co. (Delco) and introduced in the 1910 Cadillac Model 30. This ignition was developed by Charles Kettering and was considered a wonder in its day. Atwater Kent invented his Unisparker ignition system about this time in competition with the Delco system. By the end of the 20th century mechanical ignitions were disappearing from automotive applications in favor of inductive or capacitive electronic ignitions fully controlled by engine control units (ECU), rather than directly timed to the engine's crankshaft speed.