Acoustic Powered Tether Elevators Keith Lofstrom keithl@launchloop.com http://launchloop.com/AcousticClimber http://launchloop.com/SE2017 (both pages work in progress) Space elevator climbers require an external power source to climb from ground to GEO. Early designs assumed an electrically powered track. The Edwards design assumed laser power to a super-efficient photovoltaic array, while the assessment design assumes huge gossamer photovoltaic arrays powered by sunlight. Lifting a 20 tonne climber at 60 m/s in full Earth gravity requires 12 megawatts of thrust power. PV systems that deliver this much power will be massive. They belong in weightless zero gee, not in full gravity and 12 hours of darkness. Fortunately, super-stiff carbon nanotube tethers can deliver more than 20 megawatts power mechanically, directly to an acoustic climber, one tonne of spars, vibration-resonant wheels, electric motors, and power electronics that convert vibration energy directly into climb power, powering the rapid 24x7 lift of a 15 tonne climber/payload vehicle. Longitudinal (along the length) vibrations of a super-stiff ( 1 TPa ) carbon nanotube tether can carry enormous amounts of power. A 130 kN sinusoidal vibration stores an average of 400 joules of spring energy and 400 joules of kinetic energy per meter of 13.65 gram/m tether; the longitudinal wave velocity is more than 27 km/s. A solar powered "shaker" at geosyncronous altitude can transmit 22 MW of acoustic power down the tether all the way to the surface, past intermediate stage climbers tuned for low gravity and high speed. This permits near-surface climb rates exceeding 100 m/s and high altitude climb rates exceeding 1000 m/s, where gravity is lower and a fatter tether can carry more acoustic power. Alternately, somewhat less power can be delivered from a shaker at the bottom, to lift the materials to construct the shaker at GEO. Descending climbers can convert kinetic energy back into tether vibration, powering other climbers below. Multiple climbers can cycle up and down between staging points, with each climber stage optimized for the gravity load and available power. Upbound climbers can rendezvous at speed and "forklift" payloads from lower to upper climbers withour stopping. A 120 MW shaker at GEO can lift more than 60 tonnes of payload per day, more than 4 times the 2013 IAA assessment design in less than 20% of the transit time. Climb rates of the first upper stage climber can be optimized for fastest passage through the van Allen belts. Acoustic climber technology may have nearterm application for construction projects in challenging environments, using Kevlar tethers to lift materials and personnel up narrow towers or cliff faces, for example. Commercial computer-aided design tools do not exist for modelling acoustic tether systems. The presentation will show drawings and animations generated by software written in the C programming language, the libGSL math package, and the libGD graphics package.