Pressurized cylinders for charging the side hatch opening actuator, called the counterbalance.
Originally pressurized with gaseous nitrogen at 5,000 psi.
Enabled a fully suited astronaut inside the Command Module to open the 350 pound weight of the combined side hatch and outer cover in 3 seconds.
NASA photo shows the counterbalance at the lower
of Apollo 17 during recovery operations, with cylinders indicated by the arrow.
One cylinder was opened prior to launch, with the ground crew closing the hatch against the counterbalance pressure after astronaut ingress.
The second cylinder was available for in-flight use if needed.
on the cylinders record the part and serial numbers, date, weight, quality control inspections, and caution notes.
One cylinder is dated 7-22-69, filled as Apollo 11 was returning from the first lunar landing.
Ref. “Apollo Command Module Side Access Hatch System,” N70-21447.
0.41 lbs. (0.19 kg) (empty)
Historic Space Systems at www.space1.com