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Dear Evil Engineer: Could I launch satellites, and a new career, with the help of a space cannon?

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Is launching satellites (via a space cannon) a promising path to a lucrative Nasa contract and invitation to the Met Gala?

Dear Evil Engineer,

Having spent 15 years working my way into the petty ranks of the millionaires with my dodgy data analytics company, I am keen to move on to the next stage in my career. I aspire to become a fashionable oligarch making a splash in the commercial space sector, which is where all the other oligarchs seem to be having the most fun.
I’m interested in providing an alternative to commercial rocket launch services: to launch satellites into orbit using a cannon large enough to double up as an execution device. Is this a promising path to a lucrative Nasa contract and invitation to the Met Gala?
Yours,

An entrepreneurial villain

 

Dear villain,

If you can offer a convincing alternative to rocket launches for propelling satellites into orbit and beyond, you may well have it made in the commercial space sector. Rockets are expensive (with launches to low Earth orbit costing at least $2,000/kg), polluting, and more prone to exploding than is typically considered ideal for multimillion-dollar vehicles. Their sheer cost means that there is already a lot of interest in replacing – or even just assisting – rocket launches with alternatives. This is probably necessary to reduce launch costs enough to make feasible large-scale space projects which remain limited to the realm of science fiction (such as space-based geoengineering, space-based solar power, and establishment of space colonies).

‘Space cannons’ are perhaps the most feasible alternative to rockets. They use explosives and enormous cannon-like structures to launch objects into space, either with a view to entering orbit (requiring speeds of at least 7,800m/s) or to escape Earth’s gravitational pull and travel to other parts of the Solar System (requiring speeds of at least 11,200m/s).

The concept goes back at least as far as Newton’s ‘Principia Mathematica’. The idea was detailed in Jules Verne’s 1865 novel ‘From the Earth to the Moon’, which described a 274m-long cannon capable of launching crewed lunar missions. In 1926, early space pioneers Max Valier and Hermann Oberth designed a cannon for firing tungsten steel projectiles to the Moon. This concept involved a 900m-long barrel containing a near-vacuum, built into a mountain with its muzzle near the top of Earth’s atmosphere to minimise drag losses.

It was not until the latter half of the 20th century that practical attempts were made at a space cannon. The first major project was Project HARP, supported by the US and Canadian departments of defence and led by real-life evil engineer Gerald Bull. In 1966, the HARP gun launched an 84kg projectile briefly into space, reaching a record altitude of around 180km. After Project HARP was cancelled, Bull continued to work on the concept for, er, Saddam Hussein’s regime, until his assassination in 1990. The work of Project HARP was continued through the 1990s and early 2000s with Project SHARP (Super HARP) at the Lawrence Livermore National Laboratory in California, which produced the world’s largest gas cannon.

With the growth of the commercial space sector in recent years, the idea of space cannons as alternatives to rockets has seen renewed interest. For instance, Project SHARP alum John Hunter is COO of Green Launch, which aims to cut the cost of orbital launches by a factor of 10 with a gas-based space cannon. The company hopes the service may be preferable to rocket launches for risk-averse companies launching satellite constellations; a single failed rocket launch can destroy hundreds of satellites at once. Green Launch has built a proof-of-concept cannon and hopes to reach the Kármán Line later this year.

There are many alternatives to rocket launches other than employing explosives in imitation of a traditional cannon. Other approaches could involve ram accelerators or electromagnetic acceleration; start-up StarTram hopes to make the latter a reality. Meanwhile, SpinLaunch is due to launch a Nasa payload later this year using a fascinating mechanical system with a spinning arm and huge vacuum chamber.

It is worth asking why a space cannon has never successfully put a satellite into orbit after all these decades of hard work. Well, it is undoubtedly a challenge to build a cannon large and powerful enough to kick a projectile into orbit, but there is no one insurmountable problem that has prevented this approach competing with rocket launches.

This is not to say that there are not major shortcomings to this approach; there are. For one, while rockets accelerate their payloads gradually, a space cannon causes accelerations so extreme as to crush conventional satellites (certainly beyond what a crew could endure). This could be lessened by building a longer barrel, but, even with a 60km barrel extending through Earth’s crust and troposphere, an acceleration beyond 500m/s2 would be required to reach orbital velocity. Entering the atmosphere at extreme speed, the payload would then suffer severe aerodynamic heating. Space cannon launches, then, are inherently unsuitable for all but the most rugged payloads.

The other major complication is that a space cannon alone cannot launch a payload into orbit; an uncorrected projectile will strike Earth’s surface before it can complete a full orbit, unless it reaches escape velocity. So, the payload will require some help to be nudged into a stable orbit, most likely from a small rocket.

These problems are non-trivial, but rocket launches as they are today are far from perfect, so the opportunity to innovate is there. I would advise you to approach this venture with certain expectations, such as about the limitations on the types of payloads you could offer to launch without destroying them. It may be that the most successful space cannon service is one which complements rather than replaces rocket launches. At any rate, space cannons are having another ‘moment’, so it seems a sensible path to becoming the sort of space-hobbyist oligarch who gets invited to the Met Gala.

Yours,

The Evil Engineer

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