Orbital Siege Breaker

An OSB (Orbital Siege Breaker) is a category of ultra-heavy tank, designed to be a mobile anti-orbital combat platform.
OSB platforms tend to be extremely large mobile fortresses sporting one or more weapons capable of engaging with orbital targets, and being mobile enough to avoid detection for as long as possible. However, their sheer size makes them vulnerable targets in ground operations, and as such are also sufficiently armed to fend off smaller assaults without any direct support.
Many worlds with static orbital defense systems will also have multiple OSB batallions to help in fending off orbital sieges. Smaller worlds will sometimes prefer using exclusively OSBs for planetary defenses.
OSBs can be used in terrestrial warfare directly, where they can be put to use as long-range artillery pieces.

Power Generation

Most OSBs utilize Two fusion generators. One generator powers the weapons and shields, and the other generator powers the anti-grav drive, force projectors, and forward kinetic drivers. A third generator is a common failsafe, intended to keep the OSB operational in case of catastrophic failure of one of the two remaining drives.

Propulsion

OSBs use 4 to 6 dedicated anti-grav engines to hover over terrain. Siding the tank are arrays of force generators, which can be pivoted to provide omnidirectional thrust, allowing the OSB to turn without significant friction, and allowing for the OSB itself to move in any direction without having to turn. For rapid forward acceleration, OSBs are often fitted with large kinetic drives, which are capable of propelling the vehicle forward at considerable speeds.

Weapons & Armament

Every OSB is equipped with at least one anti-orbital weapon, most often a Gauss Cannon, Railgun, or other Mass Driver.
Examples with two main guns are less common but do exist. Additionally, the sheer size of an OSB makes it an extremely easy target in terrestrial warfare, and as such OSBs tend to carry an arsenal of other weapons to counter aerial, naval, and ground assault.
Many OSBs are equipped with automated flak cannons to defend against aerial assault, as well as arrays of long range missiles. Some even carry one ore more Vertical Launch Systems for precision strikes.
Oftentimes they are fitted with multiple autocannon turrets.

Armor and defense

OSBs are vast mobile fortresses, clad in thick and heavy armour. But the primary defensive measure is the shield unit, comparable to the shielding system of interstellar vessels. Usually this shield itself is enough to defend the OSB against most terrestrial assaults, though no shield can survive under constant duress. The shield is nonetheless strong enough to withstand at least a few direct hits from spaceship-mounted weapons.
OSBs feature camouflage technology that is designed to complicate detection of the vehicle from orbit. These systems will try to make the OSB blend into its environment by adaptive camouflage from the top (against optical detection), anti-radar plating (against radar or environmental scanning), and ambient temperature matching (avoiding thermal detection).
None of these technologies have ever been shown to work perfectly, however they give the OSB a big enough edge to engage in guerilla tactics for long periods of time.

Communication Tools & Systems

OSBs have integrated AI Systems to help ease operation by a minimal crew of a Commander, a Pilot/Driver, a Gunner, and an Engineer. The OSBs systems are heavily automated, and in extreme circumstances, can make autonomous decisions without a crew.
OSBs are equipped with standard radio and communications systems, but primarily rely on sub-atmospheric communication systems to avoid detection by vessels in orbit. OSBs and other ground vehicles can communicate directly via laser communication, provided they have sufficient line of sight.

Sensors

OSBs are fitted with radar systems to keep track of their environments and detect incoming threats. Due to their purpose of anti-orbital systems, they have long range detection systems which are constantly scanning the skies for potential targets. Additionally, they often carry a small complement of scout drones which augment its detection range.

Beam

36m

Length

60m

Height

12m

Weight

4500 tonnes

Speed

110 km/h

Complement / Crew

4