Dale.Amon@FAS.RI.CMU.EDU (01/08/86)
I will not go into great detail, but people have certainly considered using railguns and such from the surface of the earth, and I seem to remember a factor like 5% or 10% ablation loss. The acceleration can be any number you like, it needn't be at the maximum. The only limiting factor is the length of the rail. High mountains at the equator are preferable. Since you can keep acceleration down a bit, you needn't worry about destroying transfer and insertion engines. I would also like to note on the use of the atmosphere. The atmosphere, in conjunction with much smaller burns than required otherwise, is very useful for making aerodynamic orbital plane changes. Such maneuvers are critical for a near term military TAV or a cheap equatorial to polar OTV. Aerodynamic braking is also useful for discarding excess energy from interplanetary flights. Remember the movie 2010? Remember the worries about returning Apollo CM's skipping too shallowly and going into solar orbit? Old fashioned rocket delta vee is still needed, but not nearly as much. In one case you use wings to change your orbital vector by actually banking, then you add back the slight dv used to dip into the edge of the atmosphere plus the dv lost to heat, plus a recircularization burn. IN the other case, you use the energy loss in the atmosphere to replace retroburns, and then simply circularize.