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20 In conversation | Dr Jenny Kingston of atmosphere in low-Earth orbits (LEOs), causing the orbit to decay more quickly. These include the Icarus-3 sail built in only three months for Surrey Satellite Technology’s Carbonite-1 technology demonstration satellite and the DOM on the ESA’s European Student Earth Orbiter spacecraft. International guidelines say satellites should be removed from a LEO within 25 years of the end of the mission. LEOs are one of the protected regions of near-Earth space, the other being geostationary Earth orbit. That 25-year de-orbit deadline might seem very generous, but Dr Kingston says it was chosen for pragmatic reasons based on the risk of collisions creating more debris. “Simulations have been done to look at how debris will propagate, and then this is balanced against what’s realistic,” she says. “If you have a spacecraft with a propulsion system you can de-orbit it immediately. But for that to work, your propulsion still has to be working properly at the end of the mission, and you have to decide to terminate it while everything is still healthy.” By contrast, all the drag sail needs is a command from the ground and a little power from the satellite. The sail is made from lightweight Kapton film supported by tubular aluminium booms, all of which are folded up in a frame fitted around one of the spacecraft’s panels. The booms fold at copper-beryllium tape spring hinges that store the energy used to deploy the sail. They are held inside the frame with Kevlar cords, which are severed on command with pyrotechnic cutters. “Once those cords are cut, the tape springs unfold, the booms come out, pulling the sail with them and then you’ve got a fairly rigid structure supporting the sail.” Icarus-3 is conservatively expected to bring the spacecraft down in less than 15 years, comfortably inside the 25-year deadline. Without the sail, the expected lifetime would be nearly 40 years. Guiding students As director and module leader on the MSc course at Cranfield, Dr Kingston is responsible for recruiting students, administering the technical aspects of the course and ensuring its content is relevant. She also strives to ensure students have a rewarding and enjoyable experience, and that they get good jobs in the space sector. As a module leader, in addition to teaching and assessing the students, she also supervises those working on their Master’s theses, which she says is probably her favourite part of the job. “I get paid to spend time talking about things like designing an ‘aerobot’ for a mission to Titan, with clever and enthusiastic young engineers,” she says. This hypothetical mission is the subject of an MSc thesis proposed by a former student. Titan, Saturn’s largest moon, has a thick, hydrocarbon atmosphere without free oxygen, and lakes of liquid hydrocarbons. One idea to take advantage of this that Dr Kingston explored with students was to build an internal combustion engine that works in reverse, taking in fuel from the atmosphere and burning it with oxygen stored on board the robotic air vehicle. “We decided it was a bit far-fetched,” she says, “but you’re thinking about a completely alien place, and it’s fascinating.” Representing about 900 hours of effort, such theses are substantial pieces of work and can be useful to companies wanting preliminary research on a new mission idea, she says. On-orbit servicing Another of her research areas is on-orbit servicing of satellites. Initial studies showed that it is difficult to make a business case based only on repairing failures because spacecraft are too reliable, so business models being proposed now are much more on a planned basis. This might involve launching a satellite with less fuel and more revenue-generating payload, which is scheduled for refuelling after six or seven years, she says. “Then, if you have these vehicles in space that are doing that job, you can make them multipurpose so they can go and inspect things, and see what’s happened if there’s been a problem. If a solar array hasn’t deployed, for example, they can give it a poke and release something,” she says. “It makes sense to me that you should try to make the best use that you can of this equipment in orbit, and try to make it last as long as possible.” December/January 2019 | Unmanned Systems Technology Dr Kingston, 44, is a senior lecturer at Cranfield University’s Centre for Autonomous and Cyberphysical Systems, director of the astronautics and space engineering MSc course at Cranfield, and a consultant for the space insurance industry. She attended Yateley School in Hampshire, England, then took a Bachelor’s degree in physics with space science and technology at the University of Leicester. That was followed by a Master’s degree (MSc) in astronautics and space engineering, then an engineering doctorate in spacecraft design, both at Cranfield. After finishing her MSc, she worked as a graduate trainee at the European Space Agency from 1996 to 1998 and then for small satellite manufacturer Space Innovation from 1998 to 2000 while studying for her doctorate. Dr Jenny Kingston