The Large Space Simulator (LSS) is one of the test facilities located at the European Space Research and Technology Centre (ESTEC), used by the European Space Agency (ESA) to test their satellites before launch. It has been in operation since 1986, and although there are comparable simulators at NASA and Rosaviakosmos, the LSS is easily the best facility within Europe (and arguably more user-friendly and economical than its counterparts).

From here on in, I will avoid introducing any more acronyms…

The LSS (often referred to as 'space in a can') does exactly what it says on the label - it is a very large structure that aims to simulate the conditions of space. Since these conditions are so extreme, it is important to know whether a satellite will withstand them before spending millions to place it into orbit. Of the four major requirements for satellites to function in space the LSS can realistically reproduce three: operating in a vacuum, withstanding extreme cold and withstanding direct heat and radiation from the Sun (sadly, it is unable to reproduce microgravity…). It should be pointed out that this testing facility is only used for unmanned spacecraft, since there is no way a human being could survive the conditions produced within the main test chamber.

All conditions created in the LSS are controllable by the engineers carrying out the testing. The satellite itself is also fitted with a plethora of sensors, which relay information concerning its conditions back to the engineers. This means that the testing procedure can begin gradually, and be quickly halted if there appears to be any problems with the satellite. The engineers can also control the movement of the satellite within the main chamber, thus recreating the orbit of the satellite. This is essential to accurately reproduce the conditions that different parts of the satellite will have to withstand during the mission.

The big room…

The main chamber of the LSS has an area of 2150m3, arranged in a cylindrical fashion (with a height of 15 metres and a diameter of 10 metres). The satellite enters the chamber through a hinged roof, which allows for very large spacecraft to be placed in the LSS. On the ground, there is also a 5m high door, which can be used to bring equipment into the chamber. Finally, within the large door is an ordinary, human-sized door, to allow for the day-to-day movements of engineers in and out of the chamber.

The walls of the chamber are littered with testing equipment and sensors of every imaginable kind, including photographic equipment. The photographic equipment is mainly used to measure any deformations on the satellite that occur as a result of the extreme conditions, although it also comes in very handy for public relations purposes.

Once in the chamber, the satellite is placed on a platform in the centre, which is insulated from rest of the building and the surrounding facility for stability. When testing in these extreme conditions, even slight instability could cause a disaster. Technically, the platform has a mechanical noise level of less that 10-3 g.


To reproduce vacuum conditions, the LSS is sealed and depressurised using two pumps (a turbo-molecular pump and an LHe cryo-pump). The pressure can be reduced to 3x10 mbar if necessary. Returning the chamber to normal pressure is a somewhat more complicated affair, since all equipment must be shielded to prevent contamination, and air must be pumped in very slowly to avoid damaging anything. This process can take up to 24 hours if necessary.

Extreme cold

By pumping liquid nitrogen across the walls of the test chamber, engineers are able to reduce the temperature to -196 degrees Celsius.

Extreme heat

To reproduce the temperatures reached in space when the satellite is in direct sunlight, 19 Xenon lamps (usually powered at 20 kW each) are available within the LSS. Using 12 of these lamps creates a heat and radiation intensity equivalent to 1 solar constant. The extra lamps allow the tests to be carried out over long periods, without fear of blowing a bulb. In fact, the lamps can also be turned up to 32 kW each, to give even more extreme conditions (for example, if a satellite is intended to travel very near the Sun).

Clean Conditions

The entire LSS is, not surprisingly, a designated clean room. This means that all air in the building is filtered, and engineers need to wear clean suits (plastic lab coat, hair net and shoe covers) whenever they enter. The build-up of static electricity is reduced using grounding pads at the entrance. It is also forbidden to bring any food, drink or other non-essential items into the building. Vacuum conditions, temperatures over 100 degrees Celsius and a room containing a satellite spinning at high speeds are all dangerous enough, without introducing the crumbs of your sandwiches into the mix.

For more technical specifications, see

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