Element 115 was a transnumeric compound that featured in 7 Days.
Element-115 was salvaged from the Roswell crash and was a trasuranic element that allowed for the generation of a time distortion field around the Chronosphere which was part of Project Backstep. This was the key in the process that allowed a ship to be displaced through time and space.
Serving as a fuel source, the compound generated the gravity way which was pumped through a waveguide conduit connected to the reactor of the Chronosphere. However, only a limited amount of Element 115 was recovered which is used only sparingly.