The inertial buoyancy displacement convector was a device invented by Dr. Emmett Brown. It enabled solid objects to react as a gas upon being pressurized, allowing them to rise, but without the pressure or conversion from one state to another.
On June 23, 1972, Doc successfully tested the device on his dog, Galileo. When Marty McFly (posing as "Kevin Klein", the son of his 1955 identity, "Calvin Klein") and Joey Baines broke into the home owned by Doc Brown's mother, Joey stole a cigar box, thinking that money was inside, and Marty stole a painting that he had previously seen in 1986. However, they were stopped by Doc, who Marty made every effort to avoid eye contact as he didn't want to be recognized. Joey was stopped by the inertial buoyancy displacement convector, but Marty took the device, which allowed him to leave with Joey, who was still levitating as Marty escaped.
Doc had previously buried money in the woods, after his father died, to protect it when he feared that his mother's new suitor might be solely dating her for her money. As he drew a map on the back of the painting that was stolen, that led to the money, he buried the inertial buoyancy displacement convector instead, to catch the thieves should they ever use the map.
Upon arriving back in 1986, Biff Tannen and Joey Baines realized that Marty had the painting, and took him and Marcus into the woods to use the map to recover the money. Joey revealed that he intended to return the money to Doc, but Biff wanted to keep it for himself; his greed leading to him getting caught in the trap. Switching off the device, Marty, Doc, Marcus and Joey let Biff — who was by now naked and bald — find his own way back home and returned to the McFly residence in Marty's truck.
Doc realized that the inertial buoyancy displacement convector was exactly what he needed to finish his time train, as he could use it to compensate for the limitations present in hover technology from 2017, allowing the time train to elevate efficiently. He then returned to 1893, to fulfill the promise that he made to his wife and sons, that he would take them with him to visit the future.
- Back to the Future Part III (Seen in action when the time train hovers)
- Back to the Future: The Animated Series (Seen in action when the time train hovers)
- Back to the Future (IDW Publishing)