Astronaut John Glenn, the first American to orbit Earth, is shown here in NASA's first spacesuit, designed for the Mercury programme (1958-1963).



The suits were adapted from US Navy pressure suits for high-altitude flights and not designed to be worn on spacewalks. That's because the suits folded in on themselves at the joints, decreasing the volume in the suit. That increased the pressure in the rest of the suit, making it hard for astronauts to bend their legs or arms. As a result, the suits were used only as protection against emergency losses of pressure. (Image: NASA Headquarters)

Spacesuit design took a step forward during NASA's Gemini programme, which featured the agency's first spacewalk on 3 June 1965. To insulate astronauts from the low pressures and temperature extremes of space, Gemini suits boasted extra layers and balloon-like "bladders" filled with gas to maintain pressure, while also maintaining flexibility.



Gus Grissom (left) and John Young, the crew of the first manned Gemini mission, a five-hour orbital flight on 23 March 1965, are shown here in the suits, which are attached to portable air conditioners to keep the astronauts cool. (Image: NASA Johnson Space Center)

The acid test for the Gemini spacesuit came on 3 June 1965, when astronaut Edward White ventured from the capsule for a 23-minute spacewalk - the first such foray for a US astronaut.



White used a gas-powered gun to manoeuvre in space. Oxygen was provided through an 8-metre 'umbilical' cord connected to the Gemini 4 spacecraft. (Image: NASA Johnson Space Center) Advertisement

To allow lunar explorers greater flexibility, the Apollo suits were built with bellow-like rubber joints at the shoulders, hips, elbows and knees.



Here engineer Bill Peterson fits test pilot Bob Smyth in an early incarnation of the Apollo suit in 1964. The dark straps are part of a restraint harness for the Lunar Excursion Module. (Image: NASA Johnson Space Center)

By the time of the first Moon landing in 1969, the Apollo suits boasted a backpack that provided enough oxygen for breathing, ventilation and suit pressure for 7 hours of Moon walking. Astronaut Buzz Aldrin is pictured here exploring the lunar surface during the Apollo 11 mission. Although the suits performed well in the six missions to land on the Moon, lunar dust became a worry. Astronauts reported that sharp, abrasive lunar dust damaged the suits, wearing through layers and infiltrating seals.



The Apollo suit had to be relatively light so that astronauts could move around in the Moon's gravity and weighed about 82 kg (180 pounds), including its backpack. Later space shuttle suits, by comparison, were more than 1.5 times as heavy - but they were worn in the weightless environment of low-Earth orbit. (Image: NASA Kennedy Space Center)

NASA astronauts now use a two-piece spacesuit for spacewalks called the Extravehicular Mobility Unit (EMU). Unlike the Apollo suits, which were custom-made to fit each astronaut, the EMU has interchangeable parts that can be used to accommodate a range of body sizes.



The EMU is pressurised at about a third of atmospheric pressure, so astronauts must camp out in a relatively low-pressure airlock before spacewalks to remove nitrogen dissolved in the blood and tissues. Moving too quickly to lower pressures can cause that nitrogen gas to create bubbles and obstruct blood flow, which can sometimes be fatal. The suit can weigh about 180 kg (400 lb) and operate for about 8 hours in space. It has a lifetime of 30 years. (Image: NASA Johnson Space Center)

NASA's EMU suits are not the only gear used for spacewalks. Here, astronaut Mike Fincke wears a Russian Orlan suit while performing work outside the International Space Station during the six-month Expedition 9 mission in 2004. (He and cosmonaut Gennady Padalka were originally going to use US suits but discovered problems with the suits, including a failed cooling unit.) Unlike NASA's EMU suits, which have separate pants and torso sections, Orlan suits are entered through a hatch at the back. That allows astronauts to get into and out of them quickly without assistance. The suit weighs nearly 110 kg (240 pounds), can spend 7 hours in space and is designed to last for 12 spacewalks. (Image: NASA)

China's Feitan suit had a public debut in September 2008, when one of the astronauts aboard the Shenzhou 7 performed the country's first spacewalk.



The spacesuit is reportedly modelled after Russia's Orlan suit. Here one of the Shenzhou 7 crew members emerges from the spacecraft after landing in north China. (Image: China National Space Administration)

Gloves are possibly the most important part of the spacesuit from an astronaut's perspective. In addition to cranking levers and handling power drills, astronauts use their hands - rather than their feet - as their primary mode of "walking" around their spacecraft during spacewalks. The gloves are pressurised, making it difficult for astronauts to move their fingers.



The Apollo spacesuits used two sets of gloves - an inner layer (left) consisting of cloth-covered pressure bladders, and an outer layer made of cloth, Mylar and a metallic mesh. The outer gloves were used on spacewalks to protect against micrometeorites, scratches and heat. (Image: NASA-JSC)

In May 2007, engineer Peter Homer of Southwest Harbor, Maine, won $200,000 when his design for a spacesuit glove beat NASA's in an agency-sponsored competition. His company, Flagsuit LLC, is building on that design and is working with the firm Orbital Outfitters on spacesuits for suborbital tourist trips.



Homer says that unlike current gloves, which are pleated in a way that causes the fingers to curve like a banana, his gloves bend at the same points where our fingers do. That makes it easier for astronauts to move their fingers - important since spacewalks are so labour-intensive that they often leave astronauts' hands bruised and their fingernails bent backwards. (Image: Flagsuit.com)

For decades, NASA has been working intermittently on a next-generation spacesuit that will offer more flexibility and could be used at higher pressures, to eliminate the need for camping out before spacewalks, or breathing in pure oxygen to avoid decompression sickness, or the bends. The Mark III suit (left), one prototype that began development in the late 1980s, boasts a rear-entry system and bearings at the joints to allow astronauts the ability to kneel and perform other tasks.



In the push to return to the Moon, NASA signed a contract in February 2009 with the firm Oceaneering International, Inc, to develop suits for the crew of the shuttle's replacement, the Orion capsule, which is set to fly as early as 2015. Long-time spacesuit developer Hamilton Sundstrand contested the award, but the two firms now plan to work together on the suits, which are intended to share components with a future suit to be designed for the Moon (right). (Image and illustration: NASA)