Exploring the Moon, however, required tore independence from the spacecraft. The backpack portable life support system, a self-contained supply of breathing and pressurizing oxygen, filters for removing carbon dioxide, and cooling water, gave Apollo crewmen the independence they needed.

The PLSS supplied oxygen at 3.5 to 4 psi of pressure while circulating cooling water through the liquid-cooling garment worn under the spacesuit. Lithium hydroxide filters removed carbon dioxide from the crewman's exhaled breath, and charcoal and Orlon filters sifted out odors and foreign particles from the breathing oxygen. Metabolic heat was transferred from the cooling water loops to space through a water evaporator system in the PLSS.

Mounted atop the PLSS was an emergency 30-minute supply of oxygen and communications equipment for talking with fellow crewmen on the lunar surface and with flight controllers in Mission Control Center in Houston. Additionally, the communications systems relayed back to Earth biomedical data on the crewmen.

The Apollo lunar surface spacesuit and PLSS weighed 180 pounds on Earth, but only 30 pounds on the Moon because of the difference in gravity.

With the advent of the space station program, work outside the spacecraft will be expanded to provide numerous unique on-orbit service capabilities not fully achieved in previous space program operations. Currently, scientists and engineers at two NASA facilities are working on a new generation of spacesuits for use during activity in space.