The Catacombs The Continuity Guide
by Martin Willey

Ring Around The Moon

Real life spacesuits are of at least two types- IVA (intravehicular activity), worn inside the spaceship, and EVA (extra vehicular activity), worn in space or on the moon. The latter require more protection from radiation and micrometeoroids, so are much more bulky. The Alphan spacesuit is a compound suit, worn while piloting Eagles and walking on the moon.

The Alphan spacesuit is, apparently, a single-layer suit. This is very unusual. Real life spacesuits have multiple layers to a spacesuit, which are difficult to incorporate into a single garment. There is a liquid cooling layer, worn next to the skin, because the body cannot properly regulate heat through sweat. Then there is the pressure suit, and outside that a restraint layer which compresses the body to stop it ballooning up. Outside this an EVA suit requires a Thermal Micrometeoroid Garment (TMG), normally made of several layers, to protect against radiation and small high velocity debris. These outer layers may be secured and tightened with Velcro and zippers, like those seen on the Alphan suits.

Fabric suits are usually ribbed around the joints, in a "tomato worm" design, to allow them to bend. The Alpha suits follow this convention, suggested by stitching. This is more challenging for EVA suits, which often include rigid hard shell sections, with mechanical joints.

Finally EVA suits require a Portable Life Support System (PLSS), worn on the back, to provide oxygen and remove carbon dioxide. IVA suits may be tethered to the spaceship, and may not require a PLSS. The single tube between the PLSS and the helmet is not realistic, for reasons that The Bringers of Wonder part 2 makes clear. NASA's Extravehicular Mobility Unit (EMU) suit has about 8 hours of oxygen.

The front pack is called a Display and Control Module (DCM), and has switches to adjust pressure and temperature, communications including a press-to-talk button and warning indicators. It is challenging to view the DCM by looking down in a helmet, so the astronauts carry a small wrist mirror, and all the text is written in reverse. The Alphan suits clearly identifies the astronaut with a large number; NASA's EMU has coloured stripes on the suit.

There are several elements of spacesuit design that are never shown in Space:1999, or any science fiction. Spacesuits, particularly for EVA, take time and care to put on and take off, because of the multiple layers. Usually this will require astronauts helping each other to get suited and unsuited. No astronauts take time to put on their Maximum Absorbency Garment (MAG), an adult diaper. Recent designs like NASA's Z-1 spacesuit are quicker to put on, because the astronaut climbs in through a hatch in the back, like a spaceship with legs and arms rather than clothing.

Spacesuits are typically pressurised to 30%-40% of sea level pressure, using pure oxygen. To avoid decompression sickness, astronauts must pre-breathe pure oxygen for between 45 minutes and 12 hours before putting on a spacesuit, depending on the initial spaceship pressure.

The orange spacesuit used by Moonbase Alpha resembles the orange Advanced Crew Escape Suit (ACES, also known colloquially as the "pumpkin suit"), a full pressure suit worn by US Space Shuttle crews for the ascent and entry portions of flight since 1988. The colour of the cover material is "international orange" (hex #FF4F00), and is intended to make crew easily seen in the event of bailout in the sea. The same logic would apply to the use of the colour on Moonbase Alpha. EVA suits are typically white, to maximally reflect sunlight and control temperature, but have coloured stripes to identify individuals.

Real spacesuit helmets are often fixed, with limited lateral vision. The Alphan suits have a neck ring which gives them more mobility. Real helmets have external visors to reduce glare. Unlike the Alphan helmets, none would open directly to the skin; even in the series, this was impractical, with visors frequently opening during fight sequences.

Spacesuits on the lunar surface are exposed to moon dust. No atmosphere or water have eroded the edges, so, while small, the particles are jagged and extremely abrasive. The dust clings with electrostatic charge, thanks to the intense radiation. During the Apollo 17 mission, the spacesuit joints became immobile because of accumulated dust, while the dust wore through three layers of Kevlar covering the boots. The dust transferred from the exterior of the spacesuits to the crew and interior of the pressurised spaceship. It will probably be extremely dangerous if breathed in.

Copyright Martin Willey