Skyhook: A 1,000 km Cable to the Stars

Going to space involves many difficulties, but the real problem is going to space with all the equipment and raw materials we need to begin our true adventure as an interplanetary species. Cheaper and reusable rockets are taking us in the right direction, but there is another alternative: The Skyhook concept. At first glance, it looks like another variant of the space elevator, with the difference that it would be much simpler to build, using real materials that don't belong to the field of science fiction.

Consider a rocket like the Falcon 9 Full Thrust. 549 tons of mass, 22.8 tons of payload to LEO, 8.3 tons to GTO. Mars? Just over 4 tons. 549 tons to move 4 to another planet. This is the essence of the space challenge. We need something better, much more efficient, and above all, economical. The idea behind reusable rockets is to increase launch frequency, but in the end we must break the equation, placing more payload in space while consuming less fuel. The question is... how?

Once again, the people at Kurzgesagt shared an excellent video explaining the Skyhook concept, a "hook in the sky" that captures suborbital ships and transfers enough energy to send them to other regions of the solar system. The most surprising aspect of the Skyhook is its apparent simplicity: a cable about 1,000 kilometers long, a hook at one end, and a weight at the other. The entire system works even better if it is spun. The hook of a Skyhook decreases its speed relative to the Earth's surface, and then accelerates, shooting its load like a catapult.

The final result is a transfer equivalent to twice the rotation speed of the Skyhook. And the best part is that it is within our capabilities. Undoubtedly, the cable will be subjected to extreme forces, but compatible materials like Zylon already exist, and with a good layer of redundancy, it could survive external threats (microimpacts, etc.). Furthermore, the Skyhook would pass over the same area several times a day, so these "launches" into space would be much more frequent.

Logically, there are other difficulties. Atmospheric friction prevents us from placing the Skyhook "too low", and the anchoring maneuver would be extremely complex, at a speed of Mach 12. In other words, we would have to redesign our spacecraft, but all this would be safer and more economical than continuing to launch giant missiles full of fuel at 40,000 kilometers per hour.

Restoring the Skyhook's energy also has a solution, as it acts as a kind of "orbital battery". On one hand, we could apply chemical or electric propulsion systems, but there is another option: receiving energy from ships coming from other planets during their deceleration. That's where the huge potential of the Skyhook emerges: it works even better outside Earth.

Mars is an extraordinary candidate thanks to its low gravity and thin atmosphere (Earth's "Mach 12" reduces to just 1,000 kilometers per hour). Mars would also enable access to the asteroid belt and the riches that await us there, and the closed orbit of Phobos (just 6,000 kilometers from the Martian surface) would allow us to turn that moon into a super-Skyhook. We have the technology, only will is missing.