During the 1960s, the militaries, space administrations, and design bureaus of the most powerful nations on Earth created the first thumpers, a type of spacecraft that rides the blast from a nuclear bomb to thrust forward at an incredible rate of acceleration. After discovering the planets were habitable, and the subsequent Space Race, governments saw the technology as a temporary evil that could leapfrog mankind to a new era of space travel.

An effort to replace thumpers with a safer technology would never come. Eventually, thumpers became largely operated by three military organizations in the Solar System: the Ministry of Colonization, Heavenbreaker Initiative, and Hikari Energy & Telecom. On top of their defense duties, these organizations took on the additional responsibility of maintaining the backbone of interplanetary civilization, much like the Roman legionaries of the ancient era. Thumpers became a critical part of transportation infrastructure, as civilian vessels and spaceplanes docked with these powerful and dangerous towers to reach other destinations in the Solar System.

The atomic threat that thumpers created would remain as well. Along with sleeper missiles, thumpers maintained the perpetual dread of nuclear annihilation looming over man, emphasized by the occasional horrific disaster or near-midnight scenario.

Even after humans vanished during the Unexpected Interrupt, the remaining thumpers and their automated navigation systems continue to circulate the System in a futile attempt to maintain the backbone of civilization, failing to recognize their efforts are pointless. Mankind would not come back.