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Interstellar Boostbeams

Mass-beam based system used to accelerate or decelerate spacecraft to interstellar speeds without the use of onboard reaction mass.

Boostbeam
Image from Steve Bowers
When the boostbeam first leaves the emitter station it is clearly visible, even in the vacuum of space, since the mass particles are radiating heat

Interstellar Boostbeams

Interstellar boostbeams use mass stream technology consisting of high velocity streams of microscopic smart pellets, called beamlets, to transfer momentum to ships, allowing them to accelerate or decelerate over interstellar distances without the use of propellant. These ships may be small shuttles that rendezvous with the larger cycler vessels of the Beamrider Network, or they may be complete starships that travel directly to their destination. The beamlets themselves consist of microscopic loops of smart matter with a specialised superconducting sheath and a small amount of internal propellant.

Interstellar boostbeams are larger and more powerful versions of interplanetary boostbeams, which are shorter rage systems usually integrated into a so-called Impulse Grid.

Momentum recycling

Boostbeam Recycler (2)
Image from Steve Bowers and Liam Jones
In the Current Era, momentum beams are usually recycled by reflecting the beamlets back towards the rear of the craft, where the momentum can be reused by other vessels
Modern interstellar boostbeams utilise momentum recycling to maximise efficiency. The kinetic energy and momentum of a decelerating ship is captured by the beam, then transferred across space where it can be used to accelerate another ship.

Momentum recycling represents a tremendous engineering challenge. Incoming beamlets are decelerated to match the velocity of the ship, then accelerated back out in the opposite direction. During this process, the majority of beamlets must survive accelerations to a significant fraction of lightspeed within the space of only a few hundred kilometres. In fact, a small proportion of the beamlets are vapourised. However, some of the resulting plasma can be captured by the ship and used as feedstock to manufacture new beamlets, which are added to the outgoing beam. With plasma capture, 87% of the momentum can be successfully recycled.

There are three different configurations of momentum recycling in common use.

In the central station configuration, incoming and outgoing ships are each linked directly to a central beam emitter station. The station emits a high-velocity beam to accelerate outgoing ships; the ships return a low velocity beam which the station captures and stores. This process as a whole consumes energy. For incoming ships, the station emits a low-velocity beam, and the ship returns a high velocity beam, which the station captures. This process allows the station to capture the kinetic energy of the incoming ship, store it, and use it to accelerate the next outgoing ship. If the ship is accelerating away from the emitter station, the return beam has less energy (in the emitter station's frame). But if the ship is decelerating into a system, the return beam aquires more energy, which can be captured and used to power another beamrider vessel, or can be used for other purposes.

In the loop configuration, incoming and outgoing ships in a given direction are linked by a single pair of beams. A high-velocity beam moving in the forwards direction accelerates an outgoing ship. The outgoing ship absorbs the beams's kinetic energy and returns a low velocity beam, which travels backwards until it meets an incoming ship. It absorbs the incoming ship's kinetic energy, decelerating the ship and resulting in an a high-velocity beam moving forwards. Due to losses in the beams, a central emitter station is still necessary to maintain the beam.

In the switchback configuration, outgoing ships leave behind a beam that is approximately stationary with respect to the local system. An incoming ship travelling in the opposite direction can then fly into this beam to decelerate, thereby returning the beam to a central emitter station where its energy can be captured.

Each of these configurations have various trade-offs. The central station configuration is the most flexible, and used in the majority of cases. The closed loop requires ships to arrive and depart on a specific schedule, but reduces the infrastructure requirements for busy systems.


Boostbeam recycler (configuration)
Image from Steve Bowers
One configiration for a beamlet momentum recycling system consists of four balanced funnels which divert the mass-stream backwards for potential reuse; this configuration also includes four balanced payload vessels evenly spaced around the outer edge of the largest loop

Range extenders

Modosophont interstellar boostbeams have a functional range of just over half a light year, due to dispersion of the beam. Beyond this range, while the beam can still be used, its performance degrades considerably.

In cases where a greater range is needed, the beam is used indirectly to accelerate a stream of small beam emitters, each with a mass of several kilograms. These mini-emitters have more advanced targeting systems, larger mass reserves for course correction, and are less subject to thermal fluctuations. Therefore they can reach ships over much greater distances — up to tens of light years.

The range-extenders absorb and store the beamlets used to accelerate them. When they are close enough to the ship, they link to it with a small boostbeam loop, thereby accelerating the ship and decelerating the range extender.

Range extenders are rare, only being useful when a particularly massive ship needs to brought up to a high velocity.

Transapientech Boostbeams

Boostbeams are widely used among transapients, especially as a supplement to the less advanced reactionless drives. While the basic physical principles of momentum transfer are the same, transapient boostbeams are far more powerful and efficient. Notably, the use of magmatter beamlets vastly increases the range of the beam and the momentum it can carry. Beamlets may have microscopic conversion drives, giving them much great manoeverability.

History

The earliest precursors to modern boostbeams date to the SolSys Golden Age. During this period, it was broadly accepted that beamed momentum was the most effective means of accelerating interstellar vessels, but there was no consensus on the details. Consequently, a huge variety of different techniques were experimented with and used to accelerate a great many small probes and, later, a small number of large colony ships. Attempts were made using lasers directly, small light sails accelerated by lasers, ferromagnetic grains focused by shepherd electromagnets, and optically-focused plasma, along with other techniques and many combinations thereof.

Still, these early methods were unable to accelerate large vessels to much more than 0.1c, which were usually supplemented by antimatter rockets.

The birth of the Beamrider Network ensured that boostbeam technology continued to develop during the SolSys Dark ages. Given the power and range limitations of early boostbeam technology, it was ideally suited to a system of small shuttles accelerated to match the velocity of larger cycler ships. A variety of momentum beaming techniques were used here too, but over the following centuries, increasing experience led to a more standardised technology that used smart microscopic dust grains.

Technological improvements during the Federation era increased the range and power of boostbeams to the point where they could be used to accelerate large interstellar ships to a considerable fraction of the speed of light.

Momentum recycling only became available to modosophonts in the the Age of Consolidation, when various disseminated ultratech designs allowed the construction of more robust beamlets and more precise magnetic capture systems. While these early forms only had a momentum capture rate of 40%, they resulted in significant energy savings and were widely adopted across the Beamrider Network and soon after across all boostbeam systems. A series of improvements across the following centuries led to modern momentum recycling systems with plasma capture being developed by the early ComEmp, and boostbeam technology has changed little since.
 
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Appears in Topics
Interplanetary TransportInterstellar TransportPropulsion Technology
Ships
 
Development Notes
Text by Liam Jones
from an original article by Todd Drashner
Initially published on 29 April 2013.

Completely revised by Liam Jones 16/9/25
 
 
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