The main engine simulator is designed to represent key engine operating principles, producing output factors such as thrust, plasma exhaust and magnetic field emissions as accurately as possible.

The main engines are the primary source of propulsion for the vessel and generate thrust to provide the propulsion from the creation and acceleration of high-temperature plasma. As such, main engine operation involves similar plasma management principles to those in the vessel’s fusion reactor, except in this case the plasma, once at a sufficient energy level, is designed to escape containment as quickly as possible.

Operating the main engines requires that enough plasma is created at a sufficient level of energy to replace plasma exhausted through the impulse regulator to create thrust.

Achieving this requires the correct amount of fuel to be introduced into the plasma excitation stage and sufficient energy from the heating system to generate sufficient levels of plasma energy. The more plasma in the chamber, the greater the heating energy that must be introduced to achieve a given level of excitation (although not directly in proportion – plasma particles will increasingly transfer energy between themselves as density increases).

If too little high-energy plasma is available for the required thrust, the engine will stall (a condition where plasma has too little energy to exit the engine regulator).

If too much high-energy plasma is generated, it will increase temperature and pressure within the chamber eventually causing damage or a catastrophic failure as the plasma escapes magnetic containment.

plasma creation

Hydrogen fuel gas must be heated to a minimum temperature in order to create a plasma that can be successfully contained by a magnetic field strong enough to withstand temperatures generated by subsequent stages. The target temperature for this ‘cold’ temperature is 60,000 degrees kelvin. Plasma cooler than this can only be partially contained, with un-ionised gas escaping containment. The cooler the temperature, the greater the rate of fuel gas escape.

The rate of fuel gas released to the plasma excitement stage is controlled by the engine’s throttle.

plasma excitement

Once cold plasma has been created it becomes trapped inside a magnetic containment field. Additional heating (or excitation) is applied to the cold plasma to create a hot plasma (target temperature of 50 million degrees kelvin).

The aim of the excitation process is to ensure that the plasma that enters the impulse acceleration stage produces useful thrust as it transitions and that the plasma is of high enough energy for the acceleration field to be most effective. Thrust is a reflection of plasma energy levels, although over a certain level diminished returns are experienced.

Exciting plasma to these temperatures is an energy-intensive procedure. Unlike a fusion reactor, the plasma does not reach a self-sustaining temperature – energy must constantly be supplied to excite new cold plasma as high-energy plasma is exhausted to generate thrust.

The containment field is configured as a gradient with a higher output towards the end of the excitation stage. This prevents cold plasma distributing too widely throughout the stage, reducing the efficiency of the excitation process and the ability to generate pressurised plasma. Only plasma with sufficient energy will be able to penetrate further into the stage against the higher containment field output.

The containment field gradient can be configured depending on operational requirements. The two key parameters impacting engine performance and efficiency are the amount of fuel gas required to generate thrust (specific impulse) and the amount of energy required to excite the plasma to required energy levels. A higher plasma energy level will reduce the amount of additional energy needed for excitation as high-energy plasma particles collide and transfer energy between them. The lower the energy level of the existing plasma, the more energy and time required for excitation. For this reason, plasma excitement typically continues even after plasma has stopped being exhausted for thrust (a process called ‘idling’ – see below).

An optimal ‘cruising’ configuration has plasma temperature at 50 million degrees kelvin at a plasma beta of x.

The release of excited plasma into the impulse acceleration stage is controlled by the engine’s regulator.

engine idle

The engine is only required to provide thrust when acceleration, deceleration or manoeuvring is required or where environmental conditions (such as gravity fields) introduce speed entropy.

Particularly for FTL travel, where an increase in actual speed has no impact on relativistic speed, the engines are not required to produce thrust. However, thrust must be available when required and plasma takes time to reach necessary energy levels, so the engines must effectively ‘idle’.

High-energy plasma movement beyond the regulator is limited so that plasma excitation is applied to existing plasma in the chamber rather than new plasma. Left sufficiently long in idle mode, all plasma in the chamber attains target temperature. When thrust is gain required, sufficient plasma is immediately available for high levels of thrust with minimal lag caused by the need for excitation of replacement plasma (although the amount of plasma available at target temperature will drop due to the lag).

plasma diversion

In the vacuum of space, the vessel’s forward movement will only be stopped by a countervailing force. The ability to slow or stop the vessel is provided by forward facing impulse acceleration systems. Plasma is diverted from the excitation stage using a series of magnetic diverters, which allow the plasma to be exhausted forward, providing reverse thrust.

The forward impulse acceleration systems, although a pair, are less efficient than the main systems, due to plasma energy lost during transit through the diverters and the smaller size of the forward thrust systems.

impulse acceleration

High-energy plasma release from the excitation stage is reactive to magnetic fields. The impulse acceleration stage uses a series of magnetic field generators to create a magnetic field pattern that accelerates the plasma further. The field pattern is based on alternating high and low energy magnetic fields, creating an impulse effect. The exact pattern is variable depending on the type of thrust required: some patterns provide optimised thrust from low-flow, lower-energy plasma to minimise power and fuel consumption for cruising, other patterns provide maximum thrust from high-flow, high-energy plasma for rapid vessel acceleration.

Impulse fields can also be used to control the direction of plasma exhaust, thereby providing manoeuvring capability.