A comparison of probability of survival for round and tape tethers against debris impact. Shaker Bayajid Khan 1 and Juan R. Sanmartin 2 E.T.S.I Aeronauticos, Universidad Politecnica de Madrid, 28040 Madrid, Spain The current space environment, consisting of a huge population of man-made debris in addition to natural micrometeoroids, poses a serious risk to safe operations in space, and the situation is continuously deteriorating due to in-orbit debris collisions and to new satellite launches. Bare electro-dynamic tethers can provide an efficient mechanism for rapid de-orbiting of satellites from Low Earth Orbit at end of life. A tether, however, might itself be victim of fatal damage by orbital debris. Due to its particular geometry (length very much larger than cross-section dimensions), a tether may have a relatively high risk of getting severed by the single impact of small debris. The rates of fatal impact of orbital debris on both round and tape tethers of equal length and mass, evaluated with an analytical approximation to debris-flux modeled by NASA’s ORDEM2000, shows much higher survival probability for tapes. A comparative numerical analysis using debris flux models ORDEM2000 and ESA’s MASTER2005 validates the analytical result and shows that for a given time in orbit a tape has a probability of survival about one-and-half orders of magnitude higher than a round tether of equal mass and length; since de-orbiting from a given altitude is much faster for the tape due to its larger perimetre, its probability of survival in a practical sense is well over two orders of magnitude. ORDEM, which predicts debris flux one order of magnitude higher than MASTER at the critical millimeter range of debris size, allows for a particularly simple approximation to the fatal impact rate of a tape. 1 Ph.D student, Department of Applied Physics, e-mail: bayajid.khan@upm.es 2 Professor, Department of Applied Physics, e-mail: juanr.sanmartin@upm.es, Senior Member AIAA. 1