A lift to space, is that a realistic idea? Engineers were already dreaming about this in the 19th century. The website Scientias.nl set out which plans have already passed the revue and whether there is ever a possibility of building a lift to space.
The idea of a lift to space is anything but new. In fact, we can go all the way back to Russian rocket engineer Konstantin Tsiolkovsky. In his 1895 essays entitled Dreams of Earth and Sky, he already talked about the idea of a 'space castle', which is very similar to the modern idea of a space lift. He drew inspiration for this from the Eiffel Tower in Paris. According to him, this structure should be about 36,000 kilometres high from the Earth's surface, just above the so-called geostationary orbit. Unfortunately, Tsiolkovsky did not yet go into the details, such as what kind of material would be needed for the cables, how the lift would function and what about the use of a counterweight. He was followed by other bright minds who explored the plan in a little more detail, according to Scientias.
Materials
A space lift could be a nice and affordable alternative to travel to space. But the fact that the idea has not yet received actual implementation has everything to do with the materials. Even the most modern strong and super-lightweight materials are not yet good enough to support a lift to space. Think of a cable. This will have to withstand enormous pressure regardless. It is estimated to be around 65 GPa, while steel can handle less than 1GPa. In addition, because of the different forces acting on the cable, it will have to be at its thickest at geostationary altitude and become narrower as gravity becomes more dominant, i.e. the closer we get to the platform on Earth, Jurjen de Jong, master's student in Space Studies at KU Leuven, describes on Scientias. 'This immediately makes it impossible to move the cables.' There are also ideas to make the lift climb upwards. The systems that go up and down are usually called 'climbers'. However, the huge distance to space requires some creativity. 'Simple solutions such as electronic propulsion seem to be impossible. A laser could be used that provides the kinetic energy to make a lift climb up. Making the climber go back down could be done by disconnecting the lift and using gravity or by going down the same way one goes up. A Japanese idea is to use alternating magnetic fields. One can also think of generating energy using (some kind of) solar panels or who knows, stored nuclear energy. Another recent idea is making a rotating system, also called an RSE (Rotating Space Elevator).'
Gravity
Of course, making a space lift has its share of challenges. Consider the earth's gravity, which gets weaker and weaker the closer you get to space. On the other hand, the earth undergoes rotation, creating a centrifugal force. The altitude Tsiolkovsky had already calculated is approximately the altitude at which the earth's gravity and centrifugal force balance each other out. This is also why many satellites are currently hovering at 35,786 kilometres from the equator. De Jong: 'This is because these rotate exactly along with the earth's rotation, making them appear to be hanging still from earth. Very favourable for weather and telecommunication satellites. The higher we get in space, the greater the horizontal velocity becomes. This results in an apparent force against the direction of Earth's rotation, which in physics we call the coriolis force. This force increases the higher we are. This would thereby cause the space lift to swing slightly back and forth.' In addition, of course, we also have to deal with the gravity of the moon and the sun that can pull on space lift. Lurching satellites and space debris also create collision hazards.
Platform
A space lift has to start somewhere on Earth. Ideas have already been floated for both a floating and a fixed platform. The floating platform could float on the sea or in the air. The convenience of this is that the space lift can move if a storm, meteorite, space debris or other external source is lurking. 'A fixed platform, on the other hand, is better because no energy has to be wasted in moving it. Besides, if one were to build it at a high altitude, you would also have to overcome less gravity right away. It is best to build the platform on the equator, because here you have the least impact from hurricanes and tornadoes and the coriolis force. Also, this is the best location to take a lift up to geostationary orbit.'
The 2015 documentary Sky Line explores why the idea for a space lift has persisted despite huge technical obstacles. HIerin says, among other things: 'The space lift is the only way to actually open up space to humans. There is no other way.' According to experts who speak in the film, current methods through rockets are reaching their limits in terms of performance.
The International Academy of Astronautics (IAA) stated in a 2014 study that if current technologies, where carbon nanotubes is a very important one, are further explored, a pilot project in 2025 could in all likelihood deliver packages up to an altitude of 1,000 kilometres (621 miles). With continued research and the help of a successful LEO (low Earth orbit, somewhere between an altitude of 100 and 1,200 miles) lift, they predict that a successor could reach 100,000 kilometres (62,137 miles) a decade later, well beyond geostationary orbit.
By: Kelly Bakker
Source: Scientias.co.uk/Smithsonian.com/Sky Line
