Influence of a Small End Mass on Tether-Mediated Orbital Injection

Abstract

The tether-assisted slingshot injection allows raising the apogee up to about 14 tether lengths, depending on the angular speed, whereas the perigee only rises by one tether length. With a two-cut procedure, the tether departs with the satellite at the e rst cut and is discarded close to the apogee, so that the momentum transferred by the tether provides an additional raising of the perigee. This results in a longer lifetime. The disadvantages are that typical tethers are light and can transfer little momentum at the second cut and that libration with a free end is highly unstable. With zero tension at the tip, perturbations easily propagate and the rectilinear shape is lost. A modie cation is proposed that improves on both counts, leaving a mass attached to the free end of the tether. It can be part of the deployer assembly, so that no additional weight is needed. This increases themomentum transferred at the second cut, thus raising drag-sensitive perigee. Even small masses appreciably increase in lifetime. Tether tension is higher, so that libration is more stable and the rectilinear shape is preserved for a longer time. The new mass distribution changes the frequencies of the tether oscillations and can be used to avoid resonances. Nomenclature a = semimajor axis of the orbit of G, km as = semimajor axis of the e nal orbit of S, km as1 = order one term of the expansion of as B = tether end opposite to S E.?/ = time evolution of out-of-plane oscillations e = eccentricity of the orbit of G es = eccentricity of the e nal orbit of S es1 = order one term of the expansion of es