I tried the link on about page 6 of space business and technology. This rotating tether tip travels 2.5 kilometers per second = 150 kilometers per minute = 9000 kilometers per hour, and takes 3? hours per revelution (90 minute attachment oportunities).<br />3 hours means the circumfrence is 3000 kilometers/ divide by 6.28 = 478 kilometers long = 956 kilometers in diameter. If the low end dips to 94 kilometers altitude, when an attachment is desired, the top is at 1050 kilometers altitude. My guess is tether gets shorter and crooked (S shaped?) without a pay load at the tip. 1050 - 478 = 572 kilometers for the altitude of the mass center, assuming the tether is tapered and symetrical. The center orbits at about 27,000 kilometers per hour = 7.4 kilometers per second - 2.5 = 4.9 kilometers per second - 0.4 (Earth's rotation relative to a semipolar orbit) = 4.5 kilometers per second which is the speed of the delivery vehicle, if I didn't make a wrong assumption or arithmetic error. We likely need some technology advances to make this tether, which can likely flip 4 tons anywhere in the inner solar system. The tip speed relative to Earth's surface needs to be reduced to avoid large air friction losses at less than 94 kilometers altitude. Lower and slower is better for the attachment vehicle, but puts more strain on the tether and payload. Neil