Joe Carroll has worked since 1981 on advanced space transportation, mostly involving long tethers. He led the development of the Small Expendable Deployment System (SEDS), which demonstrated controlled deorbit without rockets in 1993 and also flew successfully on SEDS-2 in 1994, and TiPS in 1996. He also developed the deployer and wire for the Plasma Motor Generator (PMG), which demonstrated electrodynamic thrust in orbit. He has also worked on unmanned and manned reentry vehicle concepts for NASA and several startups. His main current work is on electrodynamic tethers.