When one thinks about space travel, rockets immediately comes to mind. The tall, slender cylinders each loaded with millions of pounds of fuel have launched thousands of satellites into space over the past 60 years, all using the same method: (essentially) explosions. Every rocket that has ever launched have utilized some sort of chemical reaction between its onboard fuel types - usually an oxidizer with a fuel like kerosene or liquid hydrogen - and the resultant reaction generates a huge amount of energy that pushes the rocket upwards and onwards to space.

SpinLaunch is fundamentally different. Instead of launching satellites into space using rockets, the company aims to develop a centrifuge that will essentially catapult payloads to orbit. This will involve spinning the payload up to speeds in excess of 5,000 miles per hour on Earth and then releasing it skywards. While launching things into space via mass acceleration - like with a gun or catapult - had been researched by the U.S. and Canadian military previously in the form of Project HARP, there has been no serious pursuit of the idea for decades. Now, armed with almost $80 million in VC funding from some of the biggest institutional investors such as Airbus Ventures and Kleiner Perkins, SpinLaunch is hoping to prove the feasibility of its potentially revolutionary technology via flight tests in the second half of 2020.

History and the Physics of “Space Gun”

The idea of shooting things into orbit is not new. In fact, Newton’s famous cannonball thought experiment utilized the concept of a mountaintop space gun, positing that any object could be launched into orbit around the Earth if given enough velocity, proving a fundamental aspect of orbital mechanics: things orbit the Earth (and other celestial bodies) due to their velocity and not acceleration. While conventional rockets use chemical combustion engines to obtain the requisite velocity, it is completely physically plausible to reach orbit using other methods (such as using a large gun or artillery).

The space “gun” idea has been pursued in the past, most notably as part of the U.S. and Canadian military’s Project HARP, or High Altitude Research Project, from 1963 to 1967. Brainchild of the Canadian engineer Gerald Bull, the project was conceived to research the feasibility of launching satellites into orbit using giant guns. Bull envisioned the launch method to be much more cost efficient than traditional rockets because in addition to not requiring expensive rocket engines or fuel to be used, gun-launches can also happen in higher frequency and with less waste than rockets. The program was first established on the Canadian island of Barbados and was later expanded to include Highwater Range near McGill University as well as the Yuma Proving Range outside Yuma, Arizona. The largest of the guns tested by the program reached almost 120 feet (40 meters) in length and 16 inches in diameter, weighing in at almost 200 tons each. This was the infrastructure required to propel payloads to near orbital velocity. In particular, the 16-inch gun at Yuma still holds the world height record for highest projectile launched at 179 kilometers, launching a 84kg payload at over 2,000 meters per second that briefly reached space.

While Project HARP proved that it is indeed possible to launch objects into space using a giant gun, it also exposed many drawbacks with such a design. The first and most obvious downside is the payload size - given the slender nature of the gun, only very small payloads could be launched inside the barrel. This is in addition to the immense forces payloads will have to endure during launch, further reducing the type of payloads that could be launched using such methods. Even though Project HARP was cancelled in 1967, a successor to the program - Super High Altitude Research Program, or Project SHARP - was established in 1992 in the Lawrence Livermore National Laboratory. Project SHARP used a two-stage light-gas gun capable of accelerating a 5kg payload up to speeds of 3,000m/s, with a goal of eventually constructing a new gun large enough to launch payloads to space. Unfortunately, the high construction cost of a full-scale gun once again prevented the concept from becoming a reality, with the original test gun relegated to occasional scramjet tests by 1996.

SpinLaunch: Revival of the Space Gun Concept

SpinLaunch continues the decades-long legacy of mechanical launch systems, but with a decidedly modern twist. Instead of the traditional “gun” design, the company is planning on utilizing a centrifuge 100 meters in diameter to accelerate a 100 kilogram payload to orbital velocity within a big vacuum chamber. The payload will then be released into the air at an angle, flying some 150 kilometers into space before igniting its onboard engines to provide the last bit of energy required to enter orbit.

This approach uses the same fundamental principles as the space guns that came before it, but yields several important advantages. The first and most important advantage is payload capacity - the centrifuge design is much more scalable than the gun design and allows larger satellites to be launched. Satellite designers no longer need to fit within the narrow confines of a gun barrel for this design. Another big advantage is its ease of refurbishment, at least in theory. Without the need of explosives or high pressure gas to accelerate payloads, as was needed in traditional gun designs, the centrifuge design promises to be much easier to maintain and can handle much more frequent launches. Both of these advantages are important for SpinLaunch to be commercially competitive with existing rockets, allowing it to bid for traditional satellite launches at much lower prices - CEO Jonathan Yaney aims to offer launches for under $500,000, a cost that is a fraction of most smallsat launchers like RocketLab (~$6 million) and Virgin Orbit (~$10 million). It is these promises that have driven large investors like Airbus Ventures to sink millions into the startup, enabling it to move into a new headquarter in Long Beach, CA, as well as begin construction of a large-scale prototype at Spaceport America in New Mexico. The company aims to begin suborbital test flights later this year.

With all its promises and potential, there is no shortage of detractors of the company either. Many point out the sheer ludicrousness of catapulting satellites from the surface into space, arguing electronics will never survive the immense acceleration from the centrifuge. An aerospace engineer at the University of Southern California commented “no rocket could survive this [method of launch], nor could the electronics inside the rocket.” Yaney has rebuked such concerns by demonstrating to a Wired journalist how an iPhone can survive on its centrifuge with no damage, but questions and concerns remain. Others point to the enormous complexity of building a centrifuge this big and the required vacuum chamber that goes with it; one former employee admitted there is significant gulf between theory and reality. With the ongoing coronavirus pandemic, it is unclear how much cash the company has on hand to weather the storm as well as meet its year-end goal of performing a suborbital test launch as well. Given the immense secrecy surrounding the company - the company website has virtually no information - and that there has only been a single Wired article that provides significant insight into the company, one can only speculate the next steps of this ambitious startup.

Conclusion

Even given the current circumstances and bleak outlook for any startup, SpinLaunch is undoubtedly one of the most unorthodox space startups in existence. It is based on solid science, has significant financial backing, and has a viable business model that can certainly shake up the smallsat launch industry, should it ever progress beyond the drawing board. The company’s future will largely depend upon the success of the large-scale prototype it is currently constructing in New Mexico and whether it will be able to perform a successful suborbital test launch.

What I admire the most about SpinLaunch is not just its ambition but also the practicality that underlines its seemingly crazy idea. Much like Elon Musk’s SpaceX and their reusable rockets, the success of SpinLaunch will largely depend upon unproven technologies that many have called science fiction. However, the technology is theoretically achievable and the potential technical and economical advantages are enormous - the concept promises to dramatically lower launch costs and enable a launch cadence unseen by any other modes of orbital launch systems. With the right people and the right timing, the concept might just work. For now, however, we will just have to wait and see whether the secretive startup survives the economic downturn that has claimed countless startups as victims thus far.

May 2020