Low-Cost Propellant Launch to Earth Orbit from a Tethered Balloon - an Update

As previously reported [1], it may be possible to launch payloads into low-Earth orbit (LEO) at a per- kilogram cost that is one to two orders of magnitude lower than current launch systems, using only a relatively small capital investment (comparable to a single large present-day launch).11 An attractive payload would be large quantities of high-performance rocket propellant as required for the exploration of the moon, Mars, and beyond. The concept is to use small mass-produced rockets that can reach orbit with modest atmospheric drag losses because they are launched from high altitude (e.g. 22 km). These small rockets launch from this altitude by being winched up a tether to a balloon. The drag losses on a rocket are strongly related to the ratio of the rocket launch mass to the mass of the atmospheric column displaced as the vehicle ascends from the launch site to orbit. By reducing the mass of this atmospheric column to a few percent of what it would be launching from sea level, the mass of the rocket can be proportionately reduced while maintaining the drag loss at an acceptably small level.