What is a skyhook? A skyhook is a proposed momentum exchange tether that aims to reduce the cost of placing payloads into the Low Earth orbit. It is a hypothetical spinning tether, extending from the higher earth orbit, dipping 80-150 kilometres into the earth’s atmosphere, and no lower. If we lower it too much, then it will start to burn up due to the air friction. To match this, we would also need specialised aircrafts. It would be difficult, but it’ll be way easier than having a huge rocket that costs a fortune, running at a speed of about 40,000 km/hr.
Catching the tip will also be a challenge. We would only be having a time window of about 60-90 seconds to find the tip of the skyhook that would be moving at Mach 12. To make this easier we could also have some sort of fishing line, a kilometre long, with a navigation drone to help the spacecraft lock in with the skyhook. We must remember that a skyhook is not the same as a space elevator. A skyhook would require a suborbital launch vehicle to reach its lower end, while a space elevator would not. The momentum of the skyhook, however, will not last for long. It will eventually stop spinning after sending several payloads into space, and would crash and burn in the atmosphere. In order to keep the momentum going, there will be a second tip which will connect to incoming rockets from outer space. This way the momentum will keep going, and the arriving space-crafts give energy to the tether to send space-crafts into space. The more we use it the cheaper it gets.
If, in case, we are still losing energy, we can recover it by using small electric or chemical engines that constantly correct the tether’s position. A set of tethers, one around Earth and one around Mars, could make trips between the planets significantly faster, straight forward and low cost compared to rockets.
These tethers shorten trips between the planets from 9 months, down to 5 or even 3 months; and reduce the scale of rockets by 84-96%. This could be a potential stepping stone for space travel as a luxury! Tethers around Earth and Mars could provide a swift and cost-efficient transportation backbone that could make space travel more affordable.
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