Ion Drivers are an exterior modular based flight system. They attach on back of that user's legs through reinforced “stalks” that affix themselves to the user's legs. Early versions were simply held onto user's legs by high pressure suction generated by the ion drivers themselves with light cables that clicked in to draw power.
Later versions use nanobinding. (Using nanomachines to affix the stalk to the user and insert a control/power line.)
The actual Ion Driver body themselves are typically silver and look a bit like old fashioned jet engines. They have a body that tapers down at the bottom to focus energy through to increase thruster output. The top is closed and dome shaped to allow air to flow around it. Though other models tend to look different depending on version.
Ion Drivers are capable of outputting a significant amount of thrust, easily able to lift most reploids. They draw their power from the user themselves so there is no fear of running out of power (most times)… Though this use of power from the reploid means that they are limited to how much power that reploid can output for their maximum speed and agility.
Ion Drivers work for most reploids… But those with special surface coatings (like water/oil) can't use these (because they cannot be affixed). Similarly they are not designed for activation under water. Attempting to use them underwater can cause them to fail.
Fire based reploids may be unable to use the Ion Drivers if they can completely cover their body in flames (heat causes the Ion Drivers to fail quickly). Heat is one of the primary issues with the Ion Drivers. Excessive use of full speed causes them to get hot quickly and need time to cool off (or risk permanent damage and failure).
Though one aspect of using a reploid's internal power supply is that using flight while in Hypermode or using special techniques does cause an accelerated drain on that reploid's fuel supply.
Ion Drivers were first introduced in 2175 ( the Chaos Advent incident ) by Hunter R&D specialists. The initial prototypes were used by Rookie team 66 when they were forced to engage in aerial dogfights against aircraft en route to Giga City while construction was in progress. They eventually engaged Soar Squirrel in high altitude environments to great success.
Unfortunately a pair of them was stolen by the rogue reploid Dynamo. They were later sold and reverse engineered on the black market. Though these illegal copies are fairly expensive to acquire still so their distribution has been limited. That hasn't stopped some criminals from acquiring and using them though.
The Ion Drivers were deemed a successful bench test and Team 66 was allowed to keep using them. Additional field data was gathered from further use.
Since then they have undergone many revisions and alterations. Some changes have been purely aesthetic while others have added boost functions (uses more power and generates more heat but gives a temporary speed boost), cooling fins and cooling systems (to enable higher speed travel for longer).