Route Length, Curve Radius and Layout of Evacuated Tube Maglev Space Launch System

Current space launch is expensive and low-efficient because the invalid load----rocket and fuel in it occupies over 80% of the total launch weight. A solution to reduce the space launch cost and increase the launch efficiency is to construct the evacuated tube, pump air out from the tube and have the maglev vehicle loaded with the spacecraft run in it; the spacecraft fly out the tube when the maglev is accelerated to ultra-speed, e.g. 5km/s even 8km/s in the tube. By this way, the first class of the rocket could be saved, so that the launch cost would be low and lead the large scale space exploitation to become reality in the soon future. As for the tube construction, the route layout should be concerned on at first. Because of the engineering restriction, the height at the tube end wouldnt be very high, and the embedding depth wouldnt be very deep, practically about 8km. However, the tube length will be 700km at least, a completely straight tube or a completely curve tube (on a single circle) would lead a too small launch angle. Thus both of them are not feasible. Reasonable tube routes in vertical section will include two or more than two segments, for example, a straight tube segment and a curve tube segment, or two or more than two curve segments in different radius or different curve direction.