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

53 forward for other repeatable services. These include deploying scientific payloads into orbit or onto other spacecraft, refuelling or maintenance inspections of other vehicles, or correcting the orbits of spacecraft or satellites. Meanwhile, Japan’s Astroscale is also developing technology intended to prevent the Kessler scenario from becoming a reality. It is working on a demonstrator of its solution, called ELSA-d (End-of-Life Service by Astroscale, demonstration), which features two spacecraft stacked together at launch. The first is a ‘servicer’ satellite weighing about 175 kg, while the second is a ‘client’ satellite of around 17 kg. The servicer will be tasked with the safe removal of debris from orbit, and will therefore be equipped with proximity rendezvous technologies and a magnetic docking mechanism. The client satellite meanwhile will be used as a simulated piece of debris, and will be fitted with a ferromagnetic plate that enables the docking. By demonstrating that the servicer can repeatedly dock with and release from the client, Astroscale intends to show that future versions of it will be capable of connecting with defunct satellites and other ferromagnetic debris. Anticipated stages and tasks in the demonstration include searching for the client, inspecting it, rendezvousing with it and performing docking manoeuvres, both non-tumbling and while tumbling. The last of these is particularly significant, since most space debris is already tumbling, and a tumble docking in space has never been accomplished before. The ELSA-d servicer measures 1100 x 660 x 640 mm, and incorporates accelerometers, gyroscopes, magnetometers, star trackers and sun sensors for navigation sensing. Additional sensors such as vision and laser rangefinder systems are installed for rendezvous approaches, which will be key to aligning the servicer with the client when the latter is performing a tumbling manoeuvre. The craft is powered by a double solar array, with main propulsion to come from an eco-friendly chemical propellant system. Both the Skyrora and Astroscale solutions will make life safer and easier for people working in space, such as those aboard the International Space Station (ISS) and on other habitable structures planned for low-Earth orbit (LEO) and lunar destinations in the future. As less space junk will also make routine orbital supply missions safer in the long run, new logistics solutions are being devised to lower the long-term costs of replenishing fuel, food and components to the ISS and other off- world destinations. SpaceX’s reusable rockets are one such solution; lifting craft akin to the now-retired NASA Space Shuttles is another. In terms of the latter, the Dream Chaser from Sierra Nevada Corporation is a spaceplane that has been designed and developed for uncrewed cargo deliveries to LEO, among other missions. This 9 m- long spacecraft’s configuration features a lifting-body design, with small winglets for directional stability during flight and the majority of actual lift being generated by the wide, flat fuselage underbelly. The Dream Chaser returns from LEO by flying down through the atmosphere, allowing a low g -force re-entry that makes it much easier to land than rockets or capsules. The latter have comparably little control and Space vehicles | Insight limits Unmanned Systems Technology | October/November 2021 The ELSA-d will trial the use of a magnetic plate to capture and de- orbit defunct satellites and metallic debris (Courtesy of Astroscale)