28. Procedures for space travel and ship-to-ship combat

While I don't want to design a specific rules system for Asteroids23 (yet...) I feel it might benefit from some guidelines on how to handle space travel and navigation in the implied Belt setting. These rules are supposed to be as minimal as possible while covering those things that I feel are interesting to model in a game with this focus. Handling ship damage, navigation and fuel economy should create tension and interesting scenarios!

Ships

Most vessels that the PCs will have access to are either corvettes or frigates; ranging from 50 m to 100 m in lenght. They are frequently powered by fusion reactors, situated at the base of the ship. Most fusion reactors are toroid-shaped tokamaks, and therefore the reactor module looks bulky, often spherical, from the outside. The reactors power the ship systems and accelerate a stream of purplish, superheated plasma through nozzles under the reactor module. 

In addition to the reactor, large fuel containers filled with frozen hydrogen (50% deuetrium, 50% tritium) have to be located either above the reactor or as tanks affixed to the sides of the ship. The reactor produces a significant amount of radiation, which is harmful to any crew. Therefore, the reactor module is usually separated from the living quarters by some sort of shield, often shaped like an upside-down parabola. 

The living quarters are often a series or a cluster of cylindrical modules, imagine something like a current-day space station. There is no gravity aboard such a ship, beyond the brief tug of acceleration at the beginning of a burn. In order to get gravity, some larger vessels have rotating carousel modules, with the oblong main body of the ship acting as the axis of rotation.

The reactor generates a lot of heat too, and that heat has to be somehow radiated away from the ship, which is easier said than done in a vacuum. To that end, many ships have large wing-like structures, resembling black solar panels.

In terms of rules, a ship could be construed as consisting of a rocket enginge, a reactor, fuel tanks, radiation shield, living quarters and heat radiators. In addition to this, most vessels have a comms and sensors array. You may consider each module to have three possible states intact, damaged and destroyed. Damaged modules reduce their performance and function in some suitable way. Destruction has more serious implications.

• A damaged rocket engine requires an additional brake to correctly exit a trajectory. A destroyed rocket engine makes the ship immobile.
• A damaged reactor doubles fuel usage. A destroyed reactor shuts down all systems, including propulsion, computers and life support.
• A damaged fuel tank leaks one unit of fuel each day; a destroyed fuel tank prevents reactor operation.
• A damaged radiation shield results in radiation damage to the crew, which could be simulated by requiring a fortitude save every day to avoid light damage, with two failed saves in a row leading to deadly sickness. A destroyed radiation shield causes harm much quicker.
• Damage to living quarters has little practical effect beyond inconvenience: cold, heat, bad air and radiation hazards all abound. Destroyed living quarters have the obvious effects of no longer being able to support a living crew. These are probably easier to replace than any of the prior modules.
• Damaged heat radiators reduce the state of the reactor by one step every day of operation, destroyed heat radiators reduce the state of the reactor each time the engines are fired at all. 
• Damage to comms and sensors  reduces their range (as discussed below). A destroyed comms and sensors array means communication becomes impossible and only allows simple, near-range navigation by eye. Flying anywhere far away is impossible as well. 

Travel

Divide the belt into 12 segments, and each segment into 30 subsegments or minutes. Traversing one segment typically requires one day. Just traversing one minute, not as a part of a longer journey, requires one hour. In order to travel from one known point to another, the crew has to plot a trajectory using the ship computer and the sensors array, then expend one unit of fuel in order to accelerate into the trajectory. This is known as a burn. Once the destination is almost reached, the ship has to flip (which is known as performing a tack, or tacking) and fire the engines again. This requires another unit of fuel and is known as a brake. Usually this works, but if something goes wrong (for example, if the sensors array or rocket engine is damaged) another brake (and hence expenditure of another unit of fuel) is required. 

In order to abandon the trajectory or to perform any kind of complex manoeuvre that is not cruising or travelling at least across minutes, only a single burn is required. This is often true for ship-to-ship combat as well. Slow travelling between nearby sites requires basically no fuel expenditure at all.

Travelling blindly in order to find an unkown destination is basically hopeless. Coordinates have to be at least roughly known; intact sensors can typically only find “hot” sites and ships in the present minute or in the two adjacent ones. “Hot” sites are ships or installations that produce a lot of heat, such as a ship firing its engines or an active mine. Damaged sensors can only locate things in the currently occupied minute. “Cold” sites, such as empty asteroids or ordinary habitats, are all but impossible to find by chance. Arriving at the rough coordinates of a site and making a suitable check may allow finding the site, depending on circumstances and proximity.

Combat

Space combat is usually far from the intense dog fights portrayed in fiction; instead ships usually spot each other (due to heat radiation) from adjacent minutes and proceed to fire torpedoes. If a hit is scored (using some relevant check), a random module is damaged. Powerful, expensive, torpedoes can cause more damage or hit several modules. Critical successes can target specific modules.  

Each fired torpedo is subject to countermeasures, if such are available. Therefore, opposed rolls between gunners are encouraged if your system supports them. A torpedo targeted by countermeasures is usually harmlessly destroyed.

Only when the enemy vessel is sufficiently crippled is it time to swoop in and claim any spoils. Beware however, as ships can be equipped with additional, close range weaponry such as turrets. The most common weapons are large machine guns, firing slugs. Powerful lasers and rail guns also exist. These weapons require huge energy expenditure, roughly corresponding to the loss of one unit of fuel. A laser can act as a countermeasure or destroy a module at short range, while a rail gun can precisely target modules at long range.

Ship stats

No ship is built equal, and they may have varying properties. For example, they can traverse segments faster or slower, hold more or less fuel, have more powerful sensors, be equipped with additional weaponry or have armored modules which can take one more step of punishment. All such upgrades should be suitably expensive.