It will be one of the most significant achievements in the nation’s modern engineering history. Sutherland spaceport in the Scottish Highlands has planning permission, with construction set to begin in 2021. Secondary legislation enabling flights is expected to go through parliament later this year.
The most important ingredients in the equation, however, are the rockets. Two Scottish firms lead the pack – Orbex, which aims to launch satellites from Sutherland with its Prime ‘micro-launcher’, and Skyrora, which is developing a suite of rockets for launches from the UK and elsewhere in northern Europe.
Printed rockets
Orbex already has six launch contracts, with the first planned for late 2022. Launches will ramp up “gently”, said Chris Larmour, CEO of Orbex – one or two in the first couple of years, reaching full ‘cadence’ by 2024 or 2025.
Additive manufacturing plays a key part in the company’s vision, and it commissioned the largest industrial 3D printer in Europe earlier this year. Known for rapid prototyping and flexibility, the technique might not seem like the most obvious choice for rocket engine manufacturing, but Larmour said it offers big cost and time savings.
“It’s not the best for every job. So for some jobs CNC or manual fabrication is still the best way,” said Larmour. “But for rocket engines, in particular, 3D printing offers cost and time savings, because they’re very complex, particularly the chambers… they contain internal ducts that duct the fuel around the engine to cool it. And, with 3D printing, we can build all these features in without having to do additional processing steps that take up inordinate amounts of time and money in a more traditional process.”
With a bit of post-processing, cleaning and flattening of surfaces, the company should be able to produce an engine a week. It aims to build 35 a year, with seven engines per rocket. Using conventional techniques could take two to three months, said Larmour.
Orbex also aims to recoup some costs by building reusability into its micro-launcher. SpaceX-style reusability – requiring landing legs and extra fuel – would negate mass savings made by the choice of energy-dense renewable bio-propane, so the firm has taken a different approach.
Larmour said he is unable to give any details, for fear of it being copied, but added: “We’ve come up with a way that’s a lot smarter than that, that allows us to do it with almost no additional mass on the rocket. If that works, in practice, we’ll be able to get back significant chunks of the economic value of the rocket in a relatively mass-inexpensive way.”
Sustainability credentials
Skyrora aims to launch its sub-orbital single-stage Skylark L technology demonstrator this year, followed by a launch of the three-stage orbital satellite launcher Skyrora XL towards the end of next year.
Reusability is also a focus for Skyrora, but in a slightly different way – the firm hopes its vehicles, once in space, could accomplish other tasks, such as cluster launches or debris removal.
This will be possible thanks to a “very versatile” upper stage, said head of launch Robin Hague. Hydrogen peroxide will be forced through a silver-coated mesh, causing it to fall apart, releasing oxygen and reaching 600ºC. This will then light Ecosene, Skyrora’s kerosene equivalent made from recycled plastic.
“Essentially, to light the engines, all we have to do is open the valve gently,” said Hague. “It’s so conveniently relit, which is what offers the possibility of these stages doing further jobs.”
Such multi-purpose use and recycled fuel show that Skyrora is serious about its sustainability credentials. The polar and geosynchronous orbits within reach of its vehicles are also well-suited for Earth observation, and so should boost understanding of environmental challenges.
“We want our access to space to be available without significant environmental costs,” said Hague.
This is not how space has been done previously. Cost to the environment, and billions of dollars of national investment, were seen as the inevitable price of launching technology into space. The fresh approaches taken by Skyrora and Orbex show another way forward.
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Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.