Momentum Exchange Tether as a Hypersonic Parachute During Reentry for Human Missions

摘要

The use of tethers in space shows promise in future astronauticsl applications, with the strong possibility of providing more sophisticated functionality to satellites and spacecraft One particular application of significant promise includes using a momentum exchange tether to deorbit a reentry capsule while simultaneously orbit-raising a base station. A possible consequence of this technology includes using the attached tether as a hypersonic parachute during reentry, effectively exploiting a momentum exchange tether as a drag device to reduce heat loads on the capsule. To quantify these benefits, the authors have investigated how various tether parameters would affect the system's performance in terms of reduced convective (aerothermal) heat fluxes and reduced temperatures on the capsule's leading edge, including the effect on the capsule's ballistic coefficient Modeling the system as a series of lumped masses and rigid rods (links) in conjunction with Lagrange's equations, software was developed that is capable of generating the equations of motion for any arbitrary number of links. The resulting heat loads on the capsule were calculated using a one-dimensional multilayer heat transfer model based on the system's reentry dynamics. For certain cases, the presence of a tether can reduce the convective heat flux by almost 60% and the surface temperature by just over 20% when compared with an equivalent untethered system, which would be equivalent to an 80% reduction in capsule mass or a 60% increase in capsule diameter. Moreover, the ballistic coefficient for a tethered capsule may be reduced to almost 60 kg/m~2 as compared with an untethered system value of 701 kg/m~2.