The 31st century time travel pod was a small craft, first encountered by the Enterprise NX-01 in 2152. The craft was approximately six meters long, but, due to the advanced application of an unknown spatial phenomenon, was actually bigger on the inside than on the outside.
According to information retrieved by Captain Archer and Subcommander T'Pol from Daniels, database, the pod originated almost nine hundred years in the future, and was powered by a temporal displacement drive. The pod also had the ability to absorb electromagnetic radiation, allowing it to remain undetected by the sensor technology of the 22nd century. The pod was equipped with organic circuitry, much more advanced than the technology known to the Enterprise crew, and had no visible means of propulsion. The hull of the pod was composed of a number of materials, one of which was in a semi-fluidic state.
While in the 22nd century, the pod apparently suffered some sort of critical disaster, leaving it heavily damaged by the time it was discovered by Enterprise. Investigating, the crew discovered the lone pilot of the craft, killed by the accident. It was also discovered that the pod was emitting a form of temporal radiation which had time-distorting and disorienting effects on crewmembers in close proximity to the craft. Although the pod's ultimate function was a mystery to the crew of Enterprise, Captain Archer surmised that the pilot may have been an historian, based on an earlier conversation with Daniels which indicated that, in the future, historical studies will be carried out using time travel.
Unfortunately, both the Suliban Cabal and Tholian Assembly also learned of the pod's existence and sent vessels to retrieve it. Their plans were thwarted, however, when Commander Tucker managed to reactivate the ship's temporal beacon. Within seconds of the beacon being activated, the pod, the dead pilot, and the beacon itself, all vanished, presumably having been retrieved by operatives from the future. (ENT: "Future Tense")