Most Ph.D.s focus on niche topics in a very specific field (see here) and Hilary Costello's research project is no different. Her ongoing Phd looks into the properties of aerodynamic stability of very long tethers for very high balloons or vew deep offshore oil and gas platforms underwater. Understanding tether dynamics is extremely complex with numerous factors effecting the behaviour of a cable - from the shape and aerodynamics of the tether to the elasticity, bending and torsion of the materials used not to mention the chaging wind speed and temperature at heights of up to 20km. Testing the cable dynamics of new tether designs in the real-world is a crucial part of the research process and by modelling and testing cables in isolated sections, it is possible to better understand and model how these may operate together in a larger system. With limited access to mile-high balloons, Hilary can often be found in the green pastures of Cambridge University flying kites! Join her as she explains her quest to design an aerodynamic, stable tether that will reduce tension and, ultimately, lessen the risk of large-scale failure. This film is part of a project funded by the Royal Academy of Engineering to develop the on camera communication skills of engineers across the UK. The Ri is on Twitter: http://twitter.com/ri_science and Facebook: http://www.facebook.com/royalinstitution and Tumblr: http://ri-science.tumblr.com/ Our editorial policy: http://www.rigb.org/home/editorial-policy Subscribe for the latest science videos: http://bit.ly/RiNewsletter