The RepulsorTech is a Stark Industries technology developed by Tony Stark. It powers the Iron Man armors with the Arc Reactor's energy.
The RepulsorTech was built and developed by Tony Stark after using the Mark I armor in his escape from the Ten Rings. He used the RepuslorTech to power up his advanced Iron Man armors and their weapons,shields and flight systems, including the Mark I's he rebuilt later.
Some few years,he sells S.H.I.E.L.D. with the RepulsorTech that powered up their own weapons systems on their guns,suits,vehicles,including the Helicarrier,but later pulled out in the weapons systems after realising their misuse.
When HYDRA launched a raid on the United Nations,Iron Man had arrived and apprehended all HYDRA agents before taking on three Dreadnoughts which were upgraded with RepulsorTech. Realising that HYDRA,too,had stolen his tech,he gone mad and beaten all three of them,before the S.H.I.E.L.D. Helicarrier had arrived on the scene and sent a squad of Mandroids with Iron Man. After scanning the Mandroids' armors,he was shocked and angered that S.H.I.E.L.D. had made his inventions to make war machines.
After destroying the last Dreadnought with a unibeam,he boarded the Helicarrier and argued with Fury about all this and reminded him that HYDRA had hacked their database to aquire the RepulsorTech to upgrade their forces. Then Stark had decided to get his tech back on his own.