When you picture a test pilot or astronaut wearing a pressure suit and strutting to their sleek ship, the mental image is not complete without them toting along a little metal briefcase connected to their suits via hoses. This yellow box is a portable liquid oxygen converter and serves the all important function of cooling the human inside the suit. Without cooling, the heavy layers of a pressure suit would cause the crew member to overheat within a matter of minutes.
The simple device has no moving parts or electronics. It contains a small tank full of super cold liquid oxygen, constantly heating up and boiling away into a gas. The cold gas expands through the coil of tubing surrounding the tank, then travels through a hose into the suit where it’s distributed through the crew member’s cooling garment throughout the suit. Some of the oxygen is directed to the crew member’s helmet, allowing them to breathe 100% pure oxygen prior to the flight, purging their blood of nitrogen, thus avoiding decompression sickness, otherwise known as the bends.
When the pressure suited individual sits in the cockpit, a supporting crew member will disconnect the portable system and connect the ship’s integral oxygen system which serves the same purposes during flight. Equipment identical to this was used during the Blackbird program. This interesting little artifact lies on display at Blackbird Airpark in Palmdale, California.