There are other technologies that can produce contactless forces between a spacecraft and a target. Coulomb forces have been shown to produce useful interactions between two charged spacecraft as long as the distance between them is less than a Debye length. \cite{coulombtether} A number of different systems produce contactless forces with magnetic interactions among controlled dipoles on both the spacecraft and the target. \cite{dipoleplanning} All such approaches place requirements for specific hardware on both the chaser and the target (that is, the target must have launched with certain features already in place.) However, no spacecraft currently in orbit meet these criteria, to the authors’ knowledge.
Laser tweezers can produce contactless forces on an uncooperative target. \cite{lasertweezers} However, the tweezers are best at manipulating micron- scale particles, a size restriction that no spacecraft beyond about TRL 1 can meet. \cite{lasermirrors} Thruster plumes can also produce forces between a spacecraft and a target. However, typically the combustion products from thrusters carry significant risk of contaminating optical instruments and solar panels, among other disadvantages. We conclude that current technology is limited to direct mechanical contact as the only other option to create forces on a target that has not been designed for an interactive mission.