Apollo Command Module Environmental Control Unit (ECU) and CO2 Scrubber

Fifty years ago, today, Houston instructed Apollo 13 how to cobble together a connection between the square CO2 scrubbers in the Command Module ECU to work with the round discs in the Lunar Module lifeboat which was drawn into heroic use beyond its original breathing oxygen budget (designed for a lunar landing of two people, not a round trip to Earth with three). This was one of the finest moments for duct tape… when failure was not an option.

This large artifact in the Future Ventures space museum is an original Apollo Block 2 flight version of the entire Environmental Control Unit (ECU) in the original shipping frame. It is very rare; I have never seen another in private hands. The Airesearch CO2 Cannister holder on the right has date stamps: May 26, 1967 and and Jan 5, 1968 and April 24, 1968 with NASA contract NAS-9-150 stamped on the metal tag. It’s a complex beast performing numerous functions including: air cooling and heating; humidity control; ventilation to suits and cabin; air filtration and critically to Apollo 13, CO2 and odor removal. Here is the NASA writeup on it, and diagrams and close up photos below.

And the Apollo 13 drama as portrayed in the movie was a bit distorted. Astronaut Ken Mattingly (original Apollo 13 flight crew) in The Greatest Space Hack Ever: “The beauty in this whole thing was, these guys were so prepared for even the most implausible things. They knew no one had ever simulated exactly what happened, but they had simulated the kind of stress that could be applied to the system and the people in it. They knew what their options were and had some ideas already in place about where to go. In the movie, they played it like nobody ever thought of this. They dumped a bunch of junk on the table and said, ‘Can you figure it out?’ That was the only way the movie could convey how we got there. In reality, there was total familiarity with the hardware.”

3 responses to “Apollo Command Module Environmental Control Unit (ECU) and CO2 Scrubber”

jurvetson

Apr 16, 2020 at 1:19 am

Water Glycol control panel Here on bottom left:
Left Side: Back Side: Right Side, with dual Lithium Hydroxide CO2 Scrubber Canisters Top:

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jurvetson

Apr 24, 2020 at 4:40 am

From the NASA summary of the ECU:
"The environmental control unit is the heart of the environmental control subsystem. It is a compact grouping of equipment about 29 inches long, 16 inches deep, and 33 inches at its widest point. It is mounted in the left-hand equipment bay. The unit contains the coolant control panel, water chiller, two water-glycol evaporators, carbon dioxide-odor absorber canisters, and suit heat exchanger, water separator, and compressors. The oxygen surge tank, water glycol pump package and reservoir, and control panels for oxygen and water are adjacent to the unit.
The subsystem is concerned with three major elements: oxygen, water, and coolant (water- glycol). All three are interrelated and intermingled with other subsystems. These three elements pro- vide the major functions of spacecraft atmosphere and thermal control and water management through four major subsystems: oxygen, pressure suit circuit, water, and water-glycol. A fifth subsys- tem, post-landing ventilation, also is part of the environmental control subsystem; it provides out- side air for breathing and cooling after the com- mand module has splashed down in the ocean.
The oxygen subsystem controls the flow of oxygen within the CM, stores a reserve supply for use during entry and emergencies, regulates the pressure of oxygen supplied to subsystem and pressure suit circuit components, controls cabin pressure, controls pressure in water tanks and the glycol reservoir, and provides for purging the pressure suit circuit.
The pressure suit circuit provides a continuously conditioned atmosphere. It automatically controls suit gas circulation, pressure, and temperature, and removes debris, excess moisture, and carbon dioxide from both suit and cabin gases.
The water subsystem collects and stores potable water, delivers hot and cold water to the crew, and augments the waste water supply for evaporative cooling. The waste water section of the subsystem collects and stores water extracted from the suit heat exchanger and distributes it to the evaporators for cooling.
The water-glycol subsystem provides cooling for the pressure suit circuit, the potable water chiller, and the spacecraft equipment, as well as heating or cooling for the cabin atmosphere.
The three astronauts in the command module are in their space suits and connect to the pressure suit circuit when they first enter the CM. They remain in the suits at least until after they have attained earth orbit confirmation. They also are in their suits whenever critical maneuvers are performed or thrusting is being applied to the spacecraft.
Cabin atmosphere is 60-percent oxygen and 40-percent nitrogen on the launch pad to reduce fire hazard (fire propagates more rapidly in pure oxygen that in a mixed-gas atmosphere). The mixed atmosphere, supplied by ground equipment, will gradually become changed to pure oxygen after launch as the environmental control subsystem supplies oxygen to the cabin to maintain pressure and replenish the atmosphere."

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K.B.L. Luccia-1.000 pic

May 17, 2020 at 8:41 pm

Very Interesting

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