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Jul 9, 2012

LEM EDS, Lunar Module Explosive Devices Subsystem (Part 6, Apollo Control Systems)

Lunar Module Explosive Devices Subsystem (EDS) and its control was duplicated as most LM systems were.

Lunar Module (LM) EDS devices locations

The EDS was controlled from the cockpit controls via EDS relay box shown in the next pictures.

Explosive Devices control panel in LM cockpit

Inside EDS relay box there were General Electric relays

Heavy duty wires and connectors in the LM EDS relay box

12 explosive duplicated device connectors but probably only 11 was used

All wiring and explosive charges were duplicated as shown here.

Lunar Module Explosive Devices Subsystem (EDS) simplified block diagram

Both sides were used for the wiring

EDS did not use the LM batteries but had its own batteries, one in the ascent stage and one in the descent stage. Here is the small battery shown and where they were located in LM.

 EDS had its own batteries

EDS parts placement in LM

All together there were several different types of explosive devices. Maybe the most interesting is the guillotine which job was to cut the ascent stage free from the descent stage before separation.

Interstage Umbilical Cutter (Guillotine)

Here are all the rest of the device types.

 Reaction Control Helium Isolation Valves

Ascent Propulsion Compatibility Valves 

Interstage Structural Connection - Nut and Bolt Assembly (4 places) 

 Photo of the Landing Gear Uplock

Landing Gear Uplock (4 places) 

 Circuit Interrupters

Drawing of the Descent Propulsion Helium Isolation Valve

Photo of the Descent Propulsion Helium Isolation Valve

Photo of the Descent Propulsion Helium Isolation valve

Descent Propulsion Helium Isolation valve

Maybe the most important and complex job of the EDS was to do the "ABORT STAGE" sequence. It was possible to abort the whole descent stage (drop it on the moon or where ever) and fly back to the CSM (Command Service Module). Actually at least Apollo 10 did this since it did not land on the moon.

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