Object 790 "Lunar Tank"
Fictional Historical Background:
In the early 1960s, the Space Race became the strategic high ground of the future. When the Soviet Union learned that the United States was secretly planning for lunar combat resources, it issued a top-secret directive: not only to be the first to land on the Moon, but also to be the first to establish a military defense system on the Moon to protect future Soviet lunar bases and outposts. "Object 790" came into being—this special tank was a heavy combat vehicle specifically designed for long-range patrolling, base defense, and fire support missions on the low-gravity, extremely harsh lunar surface.
Considering the low-gravity environment of the Moon, the design of Object 790 had to be redefined. The recoil of traditional tanks would severely affect shooting accuracy or even cause the vehicle to flip over. Furthermore, conventional fuel and oxygen are extremely precious resources on the Moon. The propulsion system posed the greatest challenge. The engineering bureau creatively abandoned internal combustion engines, opting instead to deploy a closed-cycle small nuclear reactor power unit named "Vostok-Atom-1" inside the hull. This compact hull was completely occupied by this nuclear power core, which not only provided a continuous stream of electricity for the tank's track propulsion, life support, and fully sealed turret operating systems, but also ensured the tank had a theoretically infinite operational range, eliminating dependence on costly fuel resupplies.
To maximize crew protection from radiation and extreme lunar temperature differentials, all three crew members (commander, gunner, and driver) were housed inside a fully sealed, heavily armored spherical turret. The driver operated the vehicle from within the turret via a specially designed remote electronic viewport located in the hull. The core weapon of Object 790 was a specially developed 110mm recoilless gun. By venting the counterforce of the propellant gases directly backward upon firing, it completely neutralized the forward recoil, allowing for omnidirectional firing in low gravity without compromising the hull's stability. Since all crew members were inside the turret, an autoloader was equipped at the rear of the turret to solve the loading issue. The front of Object 790 could withstand shells with 200–300mm of penetration, and the rear reactor was surrounded by vertical armor averaging over 250mm, designed to better protect the reactor core. The specialized track system was optimized specifically for the rugged rocks and low-traction environment of the lunar surface.
Object 790 underwent several successful trials at a secret underground testing ground within the Soviet Union that simulated the Moon's low-gravity and low-pressure environment. Although it demonstrated the robust power of its nuclear propulsion system and the precise firepower of its 110mm recoilless gun, it also possessed obvious drawbacks: the track system exposed the issue that repair and maintenance could not be performed as easily in a space environment as on Earth. However, with the postponement and ultimate cancellation of the Soviet lunar landing program in the late 1960s, the Object 790 project was shelved. In the end, it never set foot on the Moon.