A New Way of Traveling in Space: The Skyhook

Imagine a future in which all of our solar system’s planets, asteroids, and moons are interconnected through a mega-highway of space infrastructure. Imagine a future in which civilians can travel to places like Mars or Saturn on a whim. Imagine a future in which we can easily link planet-scale civilizations with a cheap, rapid, and efficient method of celestial transportation. This is the future that the Skyhook holds.

Conventional methods of space travel usually require a great deal of time and money to implement, execute, and maintain. The massive, gas-guzzling rockets of our day need huge investments and resources just to carry a few kilograms of payload to the Moon or Mars. The underlying reason for the massive cost of space travel is the overwhelming pull of Earth’s gravity. In order to propel a spacecraft into space, engineers need to ensure that the vehicle reaches a certain threshold called the escape velocity, which is the speed an object needs to be moving at in order to escape the influence of Earth’s gravity and fly into outer space. The economic problem with payload-heavy, fuel-reliant rockets lies in the battle to overcome the escape velocity every time one blasts off in an eruption of smoke and flame.

If rocket scientists and engineers add a kilogram of payload to a traditional vehicle, extra fuel is required to carry that added weight. However, the fuel itself adds a certain amount of weight, which the rocket needs even more fuel to carry. The end result is a positive feedback loop in which more and more weight is added to the rocket just to carry a few kilograms of material into outer space. Rocket scientists must find an optimal mass that serves as a ceiling for how much the payload can weigh, a mathematical problem dubbed the “rocket equation.” This task is complicated and always riddled with budgetary and intellectual constraints. The rocket equation, quite simply, is one of the reasons why rocket science is so hard.

To overcome this problem, scientists and engineers are proposing a revolutionary new way of space travel: the Skyhook. The concept of the Skyhook involves attaching a massive tether to a counterweight that orbits around the Earth. This tether would be located above the upper edge of the atmosphere and would rotate around a center of mass as it travels through the atmosphere. At one end of the tether would be a launch station for high-speed aircrafts or spacecrafts. The tether would then rotate around its center of mass, gradually gathering momentum and spinning at increasingly high speeds, until the craft detaches and is flung at an extremely rapid velocity into outer space. To put it bluntly, the Skyhook is a massive slingshot made for space travel.

At the spacecraft’s destination point would be another rotating Skyhook waiting to receive the spaceship. This receptor station would “catch” the craft at a docking station of its own and slow it down to a manageable speed. At this point, the vehicle would detach and make its own way down to the surface.

The Skyhook would drastically reduce the amount of fuel and money needed to travel to places like the Moon or Mars. Some NASA representatives even described it as “the first idea [they] have seen that offers a believable path to $100 per pound to orbit.” Most of the fuel that a spacecraft would need is simply for flying to the Skyhook’s docking station in the upper atmosphere, which is much easier than escaping the gravitational influence of Earth. Skyhook launch stations could potentially be constructed in the atmosphere all around Earth, allowing all of humanity to travel to extraterrestrial worlds. Going to Mars would become significantly easier, and traveling to Saturn or even Neptune would be a simple task considering the energy that could be saved through the construction of Skyhooks.

The concept of such a technology has already been backed by Boeing and NASA. Boeing has conducted a study on Skyhook-like infrastructure under NASA funding, titled “Hypersonic Airplane Space Tether Orbital Launch System” (HASTOL). This study has confirmed the viability of the idea, stating that the “fundamental conclusion of the Phase 1 HASTOL study effort is that the concept is technically feasible” and that “the systems are completely reusable and have the potential of drastically reducing the cost of Earth-to-orbit space access.”

In order for spacecrafts to safely land on the docking stations of Skyhooks, positioning system technologies would be used. These positioning technologies would use optical sensors to pinpoint the precise location of the Skyhook at a certain time; then computerized guidance systems would slow down the spacecraft and calibrate its movement to properly land at the docking station. These technologies have been used in the past for missions to the Moon and Mars and can easily be modified for Skyhook navigation systems.

However, the materials needed to construct Skyhooks are not available yet. The material used would need to withstand impacts and collisions from atmospheric debris and meteorites and still be lightweight enough to not slow down the craft’s motion through space. While both lightweight and durable carbon fibers exist today, they cannot currently be mass-produced due to exorbitant costs and logistical problems.

Skyhooks are not completely without risks. If a Skyhook miscalculates the correct timing to release a spaceship into space, the spaceship can go completely off track and end up floating forever into the cosmos. The landing platform at a spaceship’s destination site could also malfunction and miscalculate when the craft will arrive, causing the tether to fail to catch the vehicle and potentially trigger a crash.

While Skyhooks need to overcome multiple obstacles in order to be feasible and useful for space travel in the future, they still offer incomparable benefits to today’s fuel rockets. Their massively increased efficiency would eliminate the ever-present rocket problem and propel humanity toward exploring the next frontier of space. The concept of a Skyhook is relatively simple, but it is one with huge untapped potential for humanity’s future among the stars.