Orbital Mass Driver

Orbital mass drivers (OMD) are electromagnetically driven launch systems. They are divided into two types - passenger and cargo. OMDs are typically seen on worlds with little to no atmosphere, or in space. Space OMDs are known as Linear Drive Systems (LDS).

OMDs are a series of rails and accelerators which accelerate a payload fast enough to enter, or even exit, orbit. Typically, low orbit drivers accelerate a payload into a parabolic trajectory and the payload itself circularizes the orbit. Interplanetary drivers may use tugs at the destination to catch and decelerate payloads.

While not as simple as traditional rocketry, OMDs are a fairly cheap and consistent method to launch cargo into orbit, requiring little to no metamaterials. OMDs are typically a stepping stone to constructing space elevators for developing colonies.

Cargo drivers are OMDs built specifically to deliver non-living materials into orbit. Since there are fewer G restrictions, cargo drivers are typically high speed linear accelerators. Payloads can experience anywhere between 10-100gs of acceleration depending on the design of the driver.

Cargo drivers were first trialed on Luna in the 21st century to deliver cargo from the surface to low Earth orbit.

Passenger drivers are large and complex launch systems meant to deliver living beings into orbit without killing them. This is typically achieved through extremely long linear drivers or huge circuits that accelerate the payload at a constant 3-5gs until up to speed. Passenger drivers have extra safety requirements which include emergency braking zones, escape vehicles, and multiple redundant systems.

OMDs become less efficient relative to the atmosphere's thickness. Thicker atmospheres introduce issues such as heating through drag, the need to build the exit higher, and compensation for poor weather. These issues can be mitigated by enshrouding the entire track in a vacuum tunnel, which introduces more cost and complexity to the system.

In little to no atmosphere, OMDs cannot rely on air cooling, and as such, requires large active cooling systems or long downtime to dissipate heat on the rails and in the system.

OMD launch rails wear down over time and must be replaced. Since each system is custom built, replacement rail sections may be time consuming to produce. The GHI-Express design was introduced as a way of standardizing mass driver components.

OMDs have a secondary use as an interplanetary siege weapon and as an orbit denial weapon. Payloads can consist of starfighters, missiles, solid mass, and mines. In a strategic sense, OMDs are less important than mobile launchers since they are static and typically quickly destroyed via long range orbital bombardment. Military mass drivers are typically built underground.