Issue 40 Unmanned Systems Technology October/November 2021 ANYbotics ANYmal D l AI systems focus l Aquatic Drones Phoenix 5 l Space vehicles insight l Sky Eye Rapier X-25 l FlyingBasket FB3 l GCS focus l AUVSI Xponential 2021

58 Insight | Space vehicles The probe’s payload will therefore integrate an imager, a magnetometer and a gamma-ray spectrometer, in order to study Psyche for clues as to how the metallic inner worlds of our Solar System formed. It is due to arrive there in 2026-27. Future propulsion Given the array of autonomous systems due to be launched to the Moon, Mars and elsewhere over the next few years alone, new propulsion technologies that can lower the eye-watering costs of sending spacecraft and equipment into the Solar System are invaluable to creating a viable off-world economy. One approach to this being touted is microwave-based energy transmission. A recent experiment in Japan used microwaves to directly power the flight of an AR Drone 2.0 UAV from Parrot in real time. It used 28 GHz beams to lift the 0.4 kg aircraft to about 0.8 m from the ground for roughly 30 seconds. If scaled up sufficiently, and paired with sufficiently accurate beam-tracking to avoid missed shots, the technology could one day remotely provide the many megawatts of power needed to launch a rocket, while sparing much or all of the excessive weight and sub-optimal efficiency of liquid fuels. Over the next few years, numerous missions are also set to launch that will trial new iterations of solar sail propulsion. These include the Near- Earth Asteroid Scout this November, the Advanced Composite Solar Sail System next year, and the Solar Cruiser in 2025. Sailing spacecraft could also test some form of Earth-based laser transmissions, to see how concentrated blasts of light energy might accelerate sail-based propulsion compared with sunlight. In the nearer term, UK-based Reaction Engines has unveiled its SABRE (Synergetic Air Breathing Rocket Engine) propulsion system, which features numerous design innovations aimed at improving the efficiency of spaceplanes and other star-bound craft over traditional engines. These include an air intake designed to capture and slow air coming in at speeds of just over Mach 5, a pre- cooler that lowers the air’s temperature to enable SABRE’s superior speeds compared with existing engines (up to Mach 25 for space access) and recycles heat absorbed to power the engine, significantly lowering fuel consumption. A ramjet also serves to use excess air to generate added thrust, and the main nozzle (along with the rest of the system) is optimised for working in the Earth’s atmosphere as well as space. Summary It is heartening that sustainability is among the factors being accounted for in the latest wave of uncrewed space systems. Not only are spacecraft being developed with the express purpose of reducing orbital litter, but better use of fuel and battery energy is being touted across the board. Future off-world plans will inevitably include the construction of energy extraction infrastructure. For example, once the Moon’s (suspected copious) hydrogen and helium-3 deposits can be tapped, UGVs and autonomous spacecraft could operate with full autonomy, as self-recharging craft do on Earth. The real endurance of such vehicles will be enhanced enormously, eliminating the need to replace them except at the end of their useful life, and the availability of unmanned survey missions and power supplies for lunar or orbital construction plants will eventually become plentiful. All of this means that using rockets – and consuming the Earth’s finite resources to build and fuel them – to launch autonomous systems into space will eventually become a thing of the past. October/November 2021 | Unmanned Systems Technology The Synergetic Air Breathing Rocket Engine is poised to enable considerable fuel efficiency improvements for spaceplanes (Courtesy of Reaction Engines) One experiment used microwave beams to directly power the flight of a UAV, lifting it to about 0.8 m above the ground for about 30 seconds