Laser Launch Bus

For technologically advanced cultures, there are numerous ways to get a payload into orbit depending on the local environment, the mission profile, and the resources available. The Cobalt Protectorate Core region on Evermorn prefers to use minimal-cost systems, like launch loops, because they have such an extensive presence in space that they are exchanging cargo and crew on a nearly continuous basis. Still, the equatorial loops have only so much throughput capacity, so alternative launch sites are necessary in order to maintain the desired launch tempo and occasionally send payloads into orbit on an immediate basis (i.e. rescue missions). Furthermore, on planets in the Protectorate Periphery region, such launch loop infrastructure might not yet be constructed or might not be feasible to construct. For the Protectorate, then, the niche of immediate, minimal cost launch services is filled by ground-based laser launch systems paired with modular propulsion busses.

Power Generation

One of the advantages of a laser launch bus is that it requires only minimal machinery to operate - a 'big dumb plug' will work almost just as well as a technically advanced system with adaptive optics and regenerative cooling, the additional systems only improving efficiency at the expense of payload mass. For this reason, laser launch busses, to the extent that they are powered at all, typically mount a small bank of charge-foliated capacitors for power which will only last long enough for the bus to launch, separate, and guide recovery teams to its landing location.

Propulsion

A laser launch bus is generally a first stage for another vehicle that sits atop it, referred to here as the 'vehicle' or 'payload.' The engine of a laser launch bus is essentially a ring-shaped parabolic mirror that concentrates laser light provided by ground-based laser batteries into a toroidal region of space beneath the vehicle. A small utility module above the mirror assembly holds consumables and equipment required for the system's operations. Atmospheric gasses and gasses vented from the bus as a part of active cooling are flashed into plasma by the intensely focussed light, the expansion of which propels the vehicle upwards. Vents along the forward extent of the mirror admit more air into the chamber once the bus is underway. Manipulating the vent apertures, laser pulse rate, and focus location of the lasers grant a degree of thrust control and vectoring, though only one of these factors is under the control of the vehicle's operator during launch.
Once the vehicle moves over the horizon or exits the atmosphere, the bus separates from the rest of the vehicle and is recovered for reuse. After first stage separation, the onus is then on the vehicle to change orbit using its own engines - preferrably something that has a high specific impulse in vacuum, as the bus itself has limits on the weight it can loft into orbit. One advantage of the laser launch bus is that it needs not carry much in the way of its own consumables. The air itself constitutes the great majority of the bus' reaction mass, and coolant can be something as simple as distilled water; clever manufacturers sometimes eschew obvious model designations like 'firefly,' 'torch,' or 'star' in favor of ones like 'steam line' or 'locomotive' that evoke romantic images of the luxury travel of old while also acknowledging this inclusion of water vapor.
The intense laser light used to launch these vehicles into orbit is so bright that its reflections can cause eye damage to onlookers even miles away. For this reason, laser launch facilities are typically located in isolated regions, often amidst forests to provide the canopies as blinds, between mountains to ensure that the vehicle has reached a significant altitude before its reflections can be seen, or on remote islands to minimize the number of onlookers. An arid climate is preferable, but not necessary, for the operation of laser launch complexes because this reduces the chance of clouds or inclement weather interfering with launch operations. Wherever possible, multiple of these environmental conditions are preferred when choosing a location for a new launch site.

Weapons & Armament

Like many propulsion systems, the powerful lasers at a laser launch facility may also be pressed into service as weapons against air- or space-based threats which happen to traverse the sky above them. Multispectral scopes normally used for tracking and guidance can analyze the composition of a threat as the concentrated beams of light from the launch laser flash the target into plasma.

Armor and defense

Because weight is not a concern for the ground-based laser facilities, each laser bank is typically ensconced in an armored turret similar to that used to protect telescopes. This turret protects the lasers from inclement weather, dust, falling debris, and bombardment. The remote, well-shaded locations where these facilities tend to be located (see Propulsion) also provides a degree of physical protection.
For the vehicle itself, the laser launch propulsion bus is durable, simple in construction, heat-resistant, and highly reflective. Damage or debris on the lasing surface can present a problem, however, as these will generate regions of uneven heating during launch that can eventually burn through. Ground crews take production quality control, inspections, and repairs on propulsion busses very seriously for this reason. New busses are notorious for arriving from manufacturers in huge, protective clamshell packages that make them look like hygiene products for giants, complete with integrated crane hook loops that look like the holes where point-of-sale racks would interface with them.

Additional & auxiliary systems

Laser launch busses typically deploy parachutes or ballutes shortly after separation to facilitate soft landings, though there is some variation in the specific recovery method across manufacturers. On low-gravity worlds, a set of airbags to cushion the landing would suffice. Once landed - typically in a body of water - a geolocation beacon activates to help guide recovery crews to the bus. There are ongoing experiments on bus systems that execute a skew turn after separation and are subsequently 'caught up' by laser batteries at the original site - or another along the flightpath - in order to execute a powered landing.
As a laser-thermal propulsion system that manipulates plasma, the laser launch bus is a distant technological relative to engines like the pulse plasmoid engine found on older spacecraft like the Starsong of Tales from the Dish fame. The bus could be used for further propulsion in space with the provision of propellant to use in lieu of atmospheric gasses, but fusion magnetohydrodynamic drive systems have largely supplanted laser-thermal systems in vacuum propulsion roles due to their superior utility across multiple roles (i.e. power production).

Related Technologies

• Launch Loop