Table of Contents

Living inside a Spacesuit

Temperature

In addition to allowing astronauts to move freely in order to carry out their tasks, the suit must also provide them with a comfortable temperature in which to work. Given the attributes of the space environment and the airtight nature of the spacesuit itself, many challenges must be overcome.

Protection Against Direct Radiation

We must protect astronauts from solar radiation. The Sun’s rays can heat objects to temperatures exceeding 150 °C.

The effect of solar radiation can be compared to that of a grill. In an oven, two processes are responsible for cooking. Consider the way in which a pizza is prepared. First, there is warm air that ensures equal cooking, even under the dough. Then, there is the direct radiation of heat from the stove’s upper element that makes the cheese golden. If we want to keep the cheese from burning, the pizza is covered with a layer of aluminium foil, protecting it from the radiated heat.

The same principle is used for spacesuits. Its outer layers are made of insulating materials, such as neoprene, Gore-Tex and Dacron. The outermost layer is white to reflect the maximum radiation and is generally made of Mylar. As for the visor, it is covered with a gold film. This metal is very a effective means of protecting the face, and especially the astronauts’ eyes, against solar radiation.

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Heat Distribution

The layers of insulation composing the outer layers of the suit are perfect for protecting astronauts against the heat emitted by solar radiation and the extreme cold to which they are exposed in the shade. The insulation, however, also causes the heat and humidity given off by the astronauts’ body to remain captive in the suit. If no method existed to remove this heat, the visor would quickly fog up and the astronaut would become dehydrated.

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To avoid these problems, the suit relies on two distinct cooling systems. The first system is integrated into the Spandex undergarment worn by astronauts. This “long underwear”, called the LCVG, is interlaced with tubes in which cold water circulates. The heat given off by the astronauts’ body is transferred to the water which, once heated, is sent to a cooling element located in the PLSS, the unit worn on the back of the suit containing most of its survival systems.

The second system consists of a heat exchanger and a ventilator that work together to cool the environment and eliminate the humidity caused by perspiration. The humidity recovered using this method is processed in a water separator. The resulting water is then sent to the tank that feeds the LCVG.

To ensure that the inside surface of the helmet does not fog up, an antifogging compound is applied before all outings.

Rapid Changes in Temperature

In space, the temperature of an object can go from -120 °C “in the shade” to more than 150 °C when placed directly facing the Sun.

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Spacesuits can therefore undergo extreme changes in temperature (in the order of 270 °C and sometimes even more) when, for example, astronauts move from one side of the orbiter to the other.

This phenomenon is even more noticeable when astronauts are in an area where they are truly exposed to the Sun’s rays. The front of the suit can reach 150 °C, whereas the back may reach -120 °C.

The shuttle performs a complete orbit around the Earth in ninety minutes. Since extravehicular activities last from six to seven hours, suits are subject to many extreme variations in temperature, even if the astronauts remain at the same place on the orbiter. Positioning the shuttle so that astronauts can work primarily in the shade reduces these sudden changes in temperature.

Humidity and Convection

The sequence of things we take for granted on Earth is not necessarily the same in space. For instance, the absence of gravity affects the behaviour of objects, which sometimes creates challenging situations.

Let’s take perspiration for example. In the suit, a drop of sweat, rather than dripping or streaming downward, stays in place. Even worse, if it leaves the astronaut’s body, it could remain suspended in the suit’s atmosphere. This situation would obviously be bothersome to astronauts who have no way of using their hands to remove droplets that “float” between their helmet and their face.

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In microgravity warm air no longer has the ability to rise above cold air. These rising and falling air streams make up the phenomenon called convection. This process helps maintain a balanced temperature in a given environment. The absence of convection in a microgravity environment causes cool zones and warm zones to meet, causing increased levels of humidity. This situation would be very uncomfortable if there were no ways of preventing it.

The sophisticated cooling and ventilation systems in the suit are designed to prevent these problems, or at least reduce them.

Relationship Between Temperature and Pressure in a Spacesuit Temperature

French physicists, Jacques Charles and Joseph Gay-Lusac, determined that the volume of a gas is directly proportional to its temperature if the pressure is held constant. Therefore, at a given pressure, the warmer a gas, the more space it fills. Gay-Lussac’s Law (also called Charles’ Law), when considered with Boyle’s Law, allows us to assert that for a given volume, the pressure is directly proportional to the temperature. This is an important notion as we consider the effects of this relationship inside a spacesuit.

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The suit is a closed, airtight environment in which the volume is quite constant despite its flexibility. Without the control systems mentioned earlier, an increase in the temperature inside the suit would cause an increase in the internal pressure and its stiffness, making all the astronauts’ movements that much more difficult.

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