Continuous Earth-Moon payload exchange using motorised tethers with associated dynamics

TL Motor vehicles. Aeronautics. Astronautics;TJ Mechanical engineering and machinery

Murray, Christopher ; Cartmell, Matthew P.

University:University of Glasgow

Department:School of Engineering

关键词: motorised momentum exchange tethers, tethers, continuous Earth-Moon payload exchange, tether dynamics;   

Others  :  http://theses.gla.ac.uk/2686/1/2011cmurrayPhD.pdf

来源: University of Glasgow

【 摘 要 】

A means of conducting continuous payload exchanges between the Earth and Moon would allow materials to be transported between them on a regular basis and could be used to supply vital resources to a permanent lunar colony. In addition to this, it could provide a means of returning materials, extracted from the mineral rich lunar surface, back to Earth. The use of symmetrically laden motorised momentum exchange tethers would allow these transfers to be conducted free of any conventional propulsion, purely by the exchange of momentum between the payloads, and without the subsequent loss of orbital altitude experienced by asymmetrical tether configurations. Although this is an exciting prospect it is not without its challenges, for example, if the Moon orbited a spherical Earth adhering to Kepler's laws, the transport of materials would be conducted with clockwork precision and the colonisation of the Moon would already have taken place. However, Kepler's laws are idealised to the two body motion of perfectly spherical bodies and are applicable only in the most simplified of circumstances. The Moon's motion is in reality complex and the establishment of such a system is made even more so by the oblateness effects of a non-spherical Earth acting on the tether system in Earth orbit. Adding to this complexity is the less significant but noticeable effect of the Moon's oblateness acting on a tether in lunar orbit. Other challenges include the design of a device to capture the payloads at the tether's tips at orbital velocity in addition to effecting their release at the correct instant; and the tether system's reaction to mechanical shocks which are a real possibility if velocity mismatches between the tether tips and payloads are significant. Restricting the scope of this investigation, the aim of the following is: to determine whether such a system can be realistically established when taking into account the complex nature of the Moon and resulting opportunities for payload exchanges; to establish the logistical design of the system required to conduct these regular two-way exchanges; to determine suitable configurations of the Earth and Moon orbiting tethers for conducting these exchanges when planetary oblateness effects are taken into account in addition to the complex motion of the Moon about Earth; to configure the trajectory design of the payloads between these tethers such that the logistical requirements are satisfied; and finally to investigate an anomaly observed whilst conducting simulations of the motion of a symmetrically laden tether in orbit about Earth which relates to the theory behind the concept of gravity gradient stabilisation.