American Scientist

June 3 marks the 50th anniversary of the first American space walk, or Extravehicular Activity (EVA) in NASA terms. Astronaut Ed White took the first American steps into space from the Gemini 4 capsule on this date (below). Soviet Cosmonaut Alexi Leonov holds the title of the first space walk, performed on March 18, 1965.

Much has been learned about space suits in the harsh environment of outer space since those early days—for example, during his space walk, Leonov’s suit puffed up so much that he couldn’t operate his camera, and he had to deflate it some to get back inside the airlock. (See more about his experiences here.) The technology and design of space suits—called Extravehicular Mobility Units in NASA parlance—has also evolved greatly over the past 50 years.

In the September-October 2015 issue of American Scientist, we will feature an article from Dave Cadogan, Director of Engineering at ILC Dover, the only company that currently makes US space suits.

Here’s a preview of that article:

Space suits, as most people refer to them, are single occupant spacecraft. They consist of an articulated anthropomorphic pressure vessel that conforms to the wearer, known as the space suit assembly, and a portable life support system that typically looks like a backpack.

They appear simple at first glance, but there is a level of complexity beneath a space suit’s layers that yields an articulated spacecraft that matches human motion and protects its occupant from the harsh environment of space.

The suit consists of three major layers. Together a total thickness of less than one-tenth of an inch protects the astronaut from space.

Hundreds of space walks have been conducted since the beginning of human space exploration, including those on the surface of the Moon, from the Space Shuttle, and from the International Space Station. Over the past 50 years more than 2,877 hours of space walks have been conducted in US space suits.

The creation of an effective space suit begins with a fundamental understanding of the environments in which the suit will be used and the mission or performance capabilities the suit will need. This information is used to develop a set of requirements that engineers and technicians use to guide the selection of materials, design of components, test protocols, and overall configuration of the space suit system.

In low Earth orbit, the astronaut must be protected from and operate in the vacuum of space, thermal extremes ranging from 120 to -150 degrees Celsius, microgravity, rapid changes from intense Sun to absolute darkness as the Earth is orbited every 90 minutes, and micrometeoroids and orbital debris travelling at speeds ranging from 8 to 16 kilometers per second. In other words, it is a very dangerous and difficult place to live and work, so a space suit has to function flawlessly.

The environmental challenges increase on the Moon or planetary bodies. The Moon is covered with fine particles of lunar dust, which clog bearing joints and render a suit ineffective. The Mars atmosphere may include chemical oxidants that can degrade polymeric materials.

The suit needs to be able to mirror every human motion involved in these activities and do so in a way that limits fatigue on the wearer.

As with most protective equipment, the requirements are at odds. A strong suit is needed to withstand all the loads and environmental stresses, but at the same time the wearer does not want to feel like he or she is wearing a space suit.

All suit components must be able to withstand hundreds of hours of pressurization and typically over 100,000 cycles for each motion, such as flexion and extension of the elbow, that represent the suit's use over 25 space walks.

Wearing a space suit is an incredible experience because it provides an appreciation for what the astronauts experience, and for how much work it is. You get a feeling of how claustrophobic it is, how you have to learn to move in a certain way to work with the suit, how quickly your body makes heat during work, and where all the pressure points are.

The space suit has a number of mobility joints and bearings that enable it to mirror human motion, and creating them isn’t as easy as it looks. Imagine trying to bend a football in half. This is essentially what space suit joints do and with virtually no resistance.

Future space suits might incorporate powered exoskeletons for superhuman strength or simply fatigue reduction by using advanced robotics technology. Other actuation technologies that use flexible materials in the place of rigid robotic elements are also under study. Considerable advancements are being made in robotics, prosthetics, and soft robots that will help shape a path to realizing space suits with powered exoskeletons that move the suit for the wearer and enhance strength. However, these advancements will be difficult to realize until the problem of creating small portable power units is solved and astronauts will not have to carry tens of pounds of batteries with them to make the suit function.

Look for the full article in the September-October American Scientist to read more about the future of space suit design.