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Apollo Remote Control Unit (RCU)
for the Portable Life Support System (PLSS)
and Extravehicular Mobility Unit (EMU)

Copyright 2006 by Karl Dodenhoff. All rights reserved.
Last revised 1 August 2009.


(Above) Apollo 13 astronaut James Lovell during EVA training.
The blue arrow points to the RCU. The red arrow points to where
the RCU umbilical connected to the PLSS.
Detail from NASA photo AP13-KSC-70PC-12

The RCU was a component of the total Extravehicular Mobility Unit (EMU) space suit system, which also included the Portable Life Support System (PLSS), Oxygen Purge System (OPS), and the suit itself.  The system was added to the EMU after the redesign following the Apollo 1 accident.

Mounted on the chest of the EMU, the system provided simple controls for communications and some EMU functions, as well as warnings and indicators for EMU status.  It had a secondary function as a mounting for the standard Apollo Hasselblad camera and Oxygen Purge System actuator.

(Above) The first operational EMU test.
Apollo 9 astronaut Rusty Schweickart on the porch of LM-3 "Spider".
Note that this early RCU didn't have the warning indicators,
nor the Hasselblad camera mount.
Detail from NASA photo AS9-19-2994


View from left rear
Ref. 1

Ref. 2

Main controls
Ref. 3


Oxygen Quantity
Indicator Legend
Ref. 4

Major Features
Ref. 5

James Lovell
during EVA training
with Hasselblad
mounted on the RCU
Ref. 6

Looking at the top of the RCU (from the rear, as the crewmen did when it was mounted on the EMU), the features are as follows, from left to right:

Top of RCU Fig2-43a

Status Indicators

Status Indicators (Warning Flags): Any one of four problems (high
oxygen flow, low vent flow, low PGA pressure, or low feedwater
pressure) will cause a cylinder to rotate and reveal
the illuminated warning symbol underneath.

On the bottom of the unit are located controls for radio volume, the suit water pump, and a radio push-to-talk switch. The electrical umbilical which connected the RCU to the PLSS was also located here.

On the right side of the unit (again looking from the rear) was mounted the OPS actuator, used to supply emergency oxygen in case of a suit failure

The left side was featureless, except for a bar and strap used to operate the clamps that attached the unit to the EMU.

On the front face of the unit, (as seen standing in front of the crewman) was the Hasselblad camera mount, and the crewman's name tag (in red for the Commander, and in black for the Lunar Module Pilot).

On the rear face was a set of clamps used to attach the RCU to the suit.  Two upper clamps attached to the PLSS shoulder straps, and a 3rd one attached to a bracket on the fornt of the EMU.  A small strap was included to operate the clamps with the bulky lunar gloves on.

Photos by Ulli Lotzmann
Used with permission.
This is a training unit, now in the Smithsonian Institution's Garber Facility
where Ulli photographed it in 2006 with the invaluable aid of Amanda Young.


Beautiful photo of
the overall system
( High-Res link )

Rear face, showing clamps
used to attach the unit
to the EMU
( High-Res link )

Top face of the unit
( High-Res link )

( High-Res link )

Left side/back
( High-Res link )

Left side/bottom
( High-Res link )

Right side - OPS Actuator
( High-Res link )

Front face - the strap used
to work the clamps which
attached the unit to the EMU
( High-Res link )

Side view of plug
to connect RCU to PLSS.
( High-Res link )

End view of the plug.
( High-Res link )



Photos by Paul Kashuk
Used with permission.

Front face.  Note
OPS actuator pull
ring at left

Top view

Left side. Note strap
used to operate clamps
that attched unit to
the EMU

Right side - Note
OPS actuator
bracket & pull ring.

Above: The 3 clamps that attached the unit to the suit are clearly visible here, as well as the parts of the suit they attached to.  The top 2 clamps attached to the horizontal bars on the PLSS shoulder straps, seen just below the helmet cowling.  The bottom clamp attached to the bracket onto which the PLSS shoulder straps are attached, seen just above the small blue circular fitting at the center of the chest




1. Portion of Figure 2-43a, Section 2.5.7 in "Apollo Operations Handbook, Extravehicular Mobility Unit, Vol. 1, System Description, CSD-A-789-(1), Apollo 15-17 Rev. V, March 1971."

2. Portion of Figure 2-43c, Section 2.5.7 in "Apollo Operations Handbook, Extravehicular Mobility Unit, Vol. 1, System Description, CSD-A-789-(1), Apollo 15-17 Rev. V, March 1971."

3. Figure 2.11.5, page 2.11-8 in "Apollo Operations Handbook, Lunar Module, LM-10 and Subsequent, Vol. 1, Systems Data, NAS 9-1100, 1 April 1971."

4. A portion of Figure 2-43b, Section 2.5.7 in
"Apollo Operations Handbook, Extravehicular Mobility Unit, Vol. 1,
System Description, CSD-A-789-(1), Apollo 15-17 Rev. V, March 1971."

5. This is believed to be a Hamilton-Standard illustration.

6. NASA Photo 70-HC-74.



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