SPACEFLIGHT Space in 2030

Commence ignition

The UK may not be a centre for large rocket engine design and development but it is developing unique niches for space propulsion that could pay off in big ways. TIM ROBINSON FRAeS reports.

Half a century ago, the lift-off of the final Black Arrow rocket from Woomera in Australia in October 1971 seemed to close a chapter in Britain’s ambitions for outer space and with it the need for large rocket engines from companies, such as Rolls-Royce and Bristol Siddely. Launches were to be left to the US, Europe and Russia – with the UK focusing its efforts instead on satellites and payloads. Ten years after Black Arrow, another attempt to get the UK back into the launcher business via British Aerospace’s HOTOL, which would have been powered by a Rolls-Royce RB545 ‘Swallow’ air-breathing rocket, came to naught.

Fast forward to 2021 and, while the UK still lacks the kind of giant rocket engines developed for NASA, ESA and Roscosmos heavy launchers, it is now carving out new innovative niches in space propulsion.

Reaction Engines

Key among these is Reaction Engines, which sees Alan Bond’s HOTOL concept tweaked and improved with its SABRE air-breathing rocket that allows 0mph to Mach 5+ operations. Unlike traditional jet engines that cannot cope as the speeds and heat builds up, Reaction Engines’ precooler cools the incoming air in a blink of the eye, tricking the engine into essentially thinking it is travelling slower than it actually is. The benefits and applications of this technology are many, with some describing it as the biggest advance since the jet engine in the 1940s – from hypersonic flight, to increasing the efficiency of standard jet engines or for use in industrial power applications.

WE’VE GOT A GREAT TECHNOLOGY BASIS NOW. SO THE REAL ART NOW IS HOW WE PUT THIS TOGETHER IN AN AFFORDABLE WAY WITH THE RIGHT PARTNERS WHO CAN MOVE WITH PACE
MARK THOMAS CEO Reaction Engines

This concept is not a paper study either, with ground tests of the HX3 precooler and technical validation by other aerospace bodies in the US and Europe that the engineering is viable. Mark Thomas, CEO at Reaction Engines, says that the company has now completed major tests of critical subsystems “which allows us to now put our thought towards bringing those technologies together in some form of demonstrator, and proving the core of a SABRE engine.” Thomas is coy on concrete timelines for a demonstrator engine but says that it “would be within the next couple of years and not more remote than that”.

For spaceflight, though, a SABRE-powered spaceplane would allow single or two-stage-to-orbit operations by removing a large chunk of the oxidiser that traditional rockets have to take with them to burn as they ascend through the thickest part of the atmosphere. Instead, SABRE takes off as a traditional jet engine, before using its precooler to accelerate to hypersonic speeds. Once at the altitude where oxygen can no longer be drawn from the atmosphere, it then switches to internal oxygen tanks for the final part of the ascent. Using a SABRE-powered mothership in a two-stage-to-orbit, flying higher and faster than say the Virgin Orbit 747, means the second stage launcher can be smaller and cheaper. A SABRE-powered spaceplane would also “offer a higher payload capability than some of the systems that are going to be deployed in this first wave here in the UK,” says Thomas.

QinetiQ’s T6 electric thruster for BepiColombo under test. ESA

He describes any SABRE-powered spaceplane as a “next or next-next generation of future launchers. We are not trying to compete head-on or directly with anything that’s in the marketplace today”. The flexibility of a SABRE-powered space vehicle means a two-stage system could potentially fly everyday, just like an aircraft, from existing runways, as well as relocate to. In addition to putting satellites and payloads into orbit, a spaceplane also has a unique advantage in that it can also bring payloads back to Earth. Thomas, however, notes that flexibility is not enough: “There’ll be that continual pressure to drive down the launch costs. People will pay for capability and flexibility but fundamentally you would have to beat the best out there in the marketplace in terms of launch costs.” – a reference to the market disruption posed by SpaceX. Asked if a SABREpower launch system could beat Elon Musk’s price to orbit, Thomas said “Yes. That would be the intent”.

Interestingly, as well as big and bold ventures like spaceflight, the SABRE technology (particularly the precooler) may also be spun off into ancillary markets, such as electric vehicles, fuel-cell hybrid-electric aircraft and anywhere where heat management is needed. Says Thomas: “It’s land, sea and air – so everything from cooling technology for electric vehicles, through to fuel cell-powered aircraft and waste heat recovery systems for clean energies.”

Reaction Engines may also play a key role in helping the UK to rebuild post-Brexit relations with the rest of Europe as worries about the launcher dominance of SpaceX stalk European capitals. There is now widespread concern that Europe’s next rocket, Ariane 6, will not be able to compete with the resuable behemoth that is SpaceX. Thomas explains: “We’re doing a large amount of studies with both space agencies and industry partners to understand the utility of a SABRE engine and how that opens up the new space economy through reusable launches.”

Rolls-Royce – next stop Mars?

Meanwhile, Rolls-Royce is thinking further beyond Earth orbit and is now partnering with the UK Space Agency to investigate the feasibility of nuclear power for long duration space missions. On Earth, R-R already provides nuclear reactors for Royal Navy submarines and is working on the feasibility of small modular nuclear reactors (SMR) which would provide safe, affordable mini-power stations to plug into the electrical grid of tomorrow – providing local power for the zero-carbon economy.

Long duration spaceflight may need to rely on nuclear propulsion. Rolls-Royce

While nuclear propulsion concepts were popular in the early years of spaceflight, worries about safety on launch meant that nuclear power in space has been confined to radioisotope thermoelectric generators (RTG), a type of nuclear battery that NASA has used on Martian rovers and on the Voyager space probes.

However, the shift to looking at longer duration missions, such as Mars, Jupiter and the outer planets, along with increased power requirements for say human-crewed spaceflight, means that nuclear propulsion concepts are now undergoing a renaissance. Particularly attractive would be the capability of nuclear engines, with the potential to shorten flight times to Mars from around eight months (when orbits permit) to just three or four months. A reduced flight time would thus mean reduced radiation exposure and zero-gravity for the crew and also would mean fewer supplies of food and water would be needed for transit, potentially opening up longer missions on the surface.

Electric propulsion

The UK has also developed a niche in low-thrust but highly efficient electric propulsion that is especially suitable for satellite station keeping or long duration exploration missions. Thales in Belfast, for example, is the UK’s newest space engine facility for the Xenon Propulsion System (XPS) developed for the all-electric Thales Alenia Spacebus Neo satellite. QinetiQ, too, has been a UK centre for excellence for electric space propulsion since the late sixties, with four of its 5kW T6 Ion thrusters providing the power for ESA’s BepiColombo Mercury probe. The most powerful electric propulsion system ever flown, the T6 thrusters will propel the probe to arrive in Mercury’s orbit in 2025. QinetQ is also working on larger (T7) and smaller (T5) ion thrusters, building on experience with the T6.

Summary

The UK’s long absence from the space launcher sector, and therefore its missing capabilities in larger chemical rockets over the past decades, could perhaps be seen as a missing piece of the puzzle. However, while chemical rockets will still be important, Britain has forged some unique capabilities in space propulsion that can help unlock the ‘Space 2.0’ economy, particularly in affordable, resusable, high-frequency space access but also in engines and power solutions for more long duration and sustained exploration of the Solar System itself. The match on the UK’s blue-touch paper has now been lit, with Reaction Engines’ Thomas saying: “We’ve got a great technology basis now. So the real art now is how we put this together in an affordable way with the right partners who can move with pace.”