Angry Birds Space Come to Life: The Skyhook

If you were born in the 2000s, you likely know about Angry Birds: the viral game that grew into a multimillion-dollar series — complete with merchandise, board games, and of course, a terrible movie. In Angry Birds, players fling birds in a catapult across the screen to score points. Angry Birds Space, a spinoff of the original, featured gravity and a galaxy-themed interface. What if I told you Angry Birds Space could become a reality in the coming years? Except instead of launching a falcon bird, the “slingshots” will be launching Falcon Heavy rockets.

HASTOL System Diagram — Photo by Space StackExchange

The Hypersonic Airplane Space Tether Orbital Launch System, or the Skyhook, is an incredibly complex structure with the potential to become a transportation tool for future inter-planetary systems and space exploration.

Boeing explains that the Skyhook captures a spacecraft and spins with the object on one end and a counterweight on the other (Boeing). As it spins, the Skyhook quickly gains momentum, picking up speed as it rotates. It then lets go of the spacecraft, propelling it away from Earth with much more momentum than before. Essentially, when a spacecraft attaches to the Skyhook, it is flung into space by the momentum collected by the rotation — almost like a space catapult. To keep spinning, we would also need to use the Skyhook in the opposite direction — except instead of flinging a spacecraft into Earth, it would be slowing down the craft and charging its thrusters.

However, in order to work, the Skyhook needs to have perfect calculations. A few centimeters of error could mean the difference between sending a spacecraft to Mercury or into the Sun. Accuracy is perhaps the most challenging problem scientists will face when implementing the Skyhook.

X-43 Aircraft — Photo by NASA

For example, the spacecraft has to attach to the tether — the speed and trajectory must perfectly align with the tether’s rotation and position — or else the craft will entirely miss it. According to Boeing, the tether will be at its lowest speed at about 185 km above sea level, moving at Mach 10, or 12,000 km/h (Boeing). That means that the spacecraft must reach 12,000 km/h when it reaches the Skyhook — for reference, the Falcon 9 requires nine engines and 1.7 million kilonewtons of thrust to reach around 12,250 km/hr by the time it reaches lower earth orbit (SpaceX and NASA). However, the Skyhook’s advantage is that the spacecraft in question does not require tons of fuel, and therefore is much lighter. In fact, the NASA Hyper-X program in 2004 featured the X-43 aircraft, which reached speeds of Mach 9.6, or 10,240 km/hr (NASA). Although just under the 12,000 km/hr barrier for the Skyhook, this was almost 17 years ago, so recent technological developments will most likely solve this problem. For example, Germany is currently developing the SHEFEX II, which has reached Mach 11, or 13,582.8 km/h (AstroNews). Hypersonic airplanes may be the biggest hurdle to overcome, but once a reliable supersonic jet is released, the Skyhook will look far more attractive for space travel.

At first glance, the Skyhook seems extremely expensive to transport and produce. However, consider that even with decades of innovation on rockets’ development, one of the cheapest rockets to date, the Space-X Falcon Heavy, costs $90 million per launch — undercutting its competition by over $100 million (Space News). Furthermore, seeing as Boeing cites a possible 2000 annual uses per Skyhook, the price looks a lot more appealing (Boeing). Additionally, according to Isaac Arthur, an expert on physics, over 86% of the Falcon Heavy consists of fuel to help the payload reach its destination (Isaac Arthur). That means that Skyhooks could make the $90 million Falcon Heavy launch a staggeringly low price of $12.6 million without the requirement for nearly as much fuel. This massive reduction in cost will only magnify as infrastructure develops — making space travel far more accessible. Arther explains that “the Skyhook is cheap to construct and launch, the main cost being in the development and production of a fleet of hypersonic airplanes.”

Skyhooks could become the airports of the future — if implemented correctly, a pair of Skyhooks would make for easy transport between destinations, whether that be Earth and the Moon, the Moon and Mars, or future destinations we haven’t discovered yet. No longer would there be a need for a multi-billion dollar spaceport nor upwards of $50 million worth of fuel. With Skyhooks, only a hypersonic plane is necessary — this level of convenience is unrivaled in the space industry.

Space is the new frontier, and any discoveries making it more efficient to transport spacecraft are invaluable for our future. For interplanetary systems to ever be humanity’s future, a fast and cheap way to travel between planets is a prerequisite.

Mars — Photo by Forbes

Mars, like Earth, is in the Goldilocks zone, meaning it may be our best bet for a new habitable planet (Science News). Science is at a peak right now — the Skyhook not only represents incredible physics and engineering, but a new age of innovation with unconventional thinkers and unique approaches to problems. Although the Skyhook is in its early stage, more research and development will prove its feasibility, and perhaps one day, it will send the first commercial spacecraft to the Red Planet.

Hey! I'm Saurav, and I am a student from the Bay Area. I love physics, astronomy, and computer science, so I periodically write articles about concepts I like.