A sounding rocket carries cargo to a tube orbiting the Earth. The rocket enters the tube and is accelerated by friction to the orbital velocity. Half of the orbital energy of the electrotube is transferred to cargo, while the other half is wasted as heat. Electrodynamic tethers replenish orbital energy and straighten the electrotube. The tube is divided into loosely fitting telescoping segments to prevent buckling. No bibliography. The minimum mass is only 100 tons.
The rocket and its cargo are enclosed in a cylindrical container. A thick coating of silicon rubber (e.g., Dow Corning 3-6077 RTV) protects the container from heat and vibration. The electrotube is tapered to compensate for the ablation of the rubber.
When cargo velocity matches the speed of sound in the tube, it generates a shock wave which may damage the tube. To minimize the effect, electrotube segments are made of two different alloys having different speeds of sound.
The electrotube is similar to the orbital loop and can be used for the same purpose. It cannot be used in a Moon orbit because electrodynamic tethers are useless outside the ionosphere. The orbital loop is more massive, but it can accelerate cargo carried by unguided gun projectiles.