Here's every spacesuit NASA astronauts have worn since the 1960s — and new models that may soon arrive

• NASA gave astronauts their first operational spacesuits in the early 1960s. Since then, the designs have evolved considerably.
• Recently, astronaut Anne McClain encountered an issue with a suit that was introduced in 1983, leading NASA to cancel what would have been the first all-female spacewalk.
• New spacesuits are in development for exploring the moon, Mars, and beyond.

Space may be the final frontier, but it's wildly inaccessible and downright deadly to any plucky human without a great spacesuit.

Fit also matters a lot — too much room can make the work more strenuous or even dangerous. That reality was especially clear last Friday, when astronauts Anne McClain and Nick Hague moved 300-lb batteries outside the International Space Station (ISS).

McClain believed that a large torso section was the best fit for her on Earth, but after her roughly 7-hour spacewalk (also called an extravehicular activity or EVA) in orbit on March 22, she changed her mind.

"Anne had thought she could use the large and decided after her EVA that she needed the medium," Bob Jacobs, NASA's deputy associate administrator for communications, told Business Insider in a tweet.

McClain was teed up to perform the first all-female spacewalk with Christina Koch this Friday, but Houston found a problem: Koch also needs a medium torso piece. Unfortunately, as NASA said on Monday, only one is ready for the event.

"There are additional medium size spacesuit segments on ISS," Jacobs added. "It's the configuration that would force a spacewalk delay."

The spacesuit model in question is called an Extravehicular Mobility Unit, and it was first introduced in 1983. But the very first operational spacesuits were introduced in the early 1960s to protect high-flying astronauts as they risk their lives in the name of space exploration.

From the silvery suits of the Mercury program to future commercial and government designs, here's how astronauts' spacesuits have evolved over six decades.

If all goes well, the next generation of spacesuits just might revolutionize human exploration of other worlds.

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Mercury Suit (1961-1963)

Project Mercury marked the first time US citizens ventured into orbit around Earth.

To protect the first astronauts from sudden pressure loss, NASA modified high-altitude jet-aircraft pressure suits from the US Navy. Each space suit had a layer of neoprene-coated nylon on the inside and aluminized nylon on the outside (to keep the suit's inner temperature as stable as possible).

Six astronauts flew into space wearing the suit before NASA retired it from service.

Gemini Suit (1965-1966)

Gemini was NASA's second space program — and one with more ambitious goals. The Gemini capsule carried a two-astronaut crew into space, and had one (uncomfortable) mission that lasted two weeks.

The David Clark Company designed Gemini suits to be flexible when pressurized, and took extra steps to make them more comfortable than Mercury suits. For example, they could be connected to a portable air conditioner to keep the astronauts cool until they could hook up to the spacecraft's lines. These suits weighed 16-34 pounds.

Gemini Spacewalk Suit (1965-1966)

One type of Gemini suit, called G4C, was designed with NASA's first spacewalks in mind. Astronauts would open the hatch during these ventures and leave the safety of their vehicle to work in the vacuum of space.

To withstand the harsh space environment, the suit connected the astronauts to the spacecraft via a hose, which supplied them with oxygen. In case there was a problem, though, some variants of the suit provided up to 30 minutes of backup life support. The heaviest variant weighed about 34 pounds.