In order to be of any use to anyone, a capital ship or space vehicle must at some point slip the bonds of its mother world and head into the heavens. Between the time a craft launches and it either lands or begins superluminal travel, it is considered to be in a state of interplanetary travel (also known as interplanetary transit), ready to move between bodies in a solar system. As with intraplanetary travel, the key questions when moving between two points in interplanetary space are how long it will take to arrive at the destination point and how hard it's going to be to successfully navigate a safe course.
The most general case of interplanetary travel involves movement from one planet to another planet in the same star system. However, interplanetary travel does cover some ground that has nothing to do with moving in between planets. It may be that a vehicle is simply launched into space, orbits the planet from which it launched for a time and then descends back to its surface (as with modern space flight). It may also be that a vehicle is launched for the purpose of traveling between a planet and one of its moons or perhaps between the moons of two different planets. Still other vehicles may be sent on an investigation of some local phenomenon in space such as a comet or asteroid or to patrol the volume of space around a carrier. All forms of movement in space that remain contained within a single star system are considered forms of interplanetary transit in WCRPG and are subject to the same general rules. Since all movement between points in interplanetary space follows the same general model as movement from planet to planet, this general case will be discussed; where any significant differences exist, they will be so noted.
WCRPG has two distinct systems in place for conducting interplanetary travel. The first of these systems assumes that star systems are square grids containing various navigational way-points. These are known in the Wing Commander Universe as nav points; they highlight the most important areas of a star system. The grids containing the nav points are called nav maps. This was the system of navigation utilized in Wing Commander: Privateer and is generally designed to make getting around a star system a much faster and far simpler prospect. The second system utilizes a somewhat realistic solar system model; it is included for the sake of those player groups who want to emphasize realism. This method is seen in some of the novels such as End Run. For purposes of discussion, this method uses the generic term star system to describe itself. Both methods are discussed herein.
Navigation within a star system isn't a whole lot different from anywhere else; in order for a character to get to where they want to go, they have to first know where they are and how to get there, which in turn means having a way of determining where exactly Point A and Point B are in relation to one another and determining the shortest path between them.
A nav map is a one hundred-by-one hundred two-dimensional orthogonal grid; each line along that grid is located approximately ten thousand kilometers from the lines immediately adjacent to it. Consequently, each grid square on a nav map measures out an area of approximately one hundred million square kilometers. To help with referencing the locations of specific grid squares on a nav map, each one has a set of coordinates listed as a two-digit horizontal coordinate-by-vertical coordinate, with 00x00 corresponding to the grid square located in the upper left-hand corner of the map.
The coordinate system employed by nav maps makes finding the distance between any two points on the map almost exactly the same as finding the distance between two sets of coordinates on a planetary surface; the main difference is that there are no hemispheres on a nav map and thus no "negative" coordinates that ever need consideration. As with finding distance on a planet's surface, two methods are available for determining the distance on a nav map: simple count and real count. These two methods have the same sets of advantages and disadvantages as their planetary counterparts.
To employ simple count, a GM simply needs to find the coordinates of the source position and the destination position, subtract the smaller of the two numbers along a given axis from the larger number, add together the resultant amount of both axes and multiply the sum by ten thousand kilometers to get the final distance. For example, a craft moving from grid square 10x42 to 59x37 would move a total of 540,000 kilometers using simple count (59-10 = 49, 42 - 37 = 5, 49 + 5 = 54, 54 * 10,000 km = 540,000 kilometers). Since the smaller number is always subtracted from the larger, there should never be an instance where a negative value is the result; if one appears, GMs should assume that they've made an error in calculation.
As might be expected, real count utilizes the algebraic distance formula. A GM utilizing this method begins as they would simple count by determining the change in position along the x and y axes. These values are squared and then added together. The GM must then take the square root of the result and multiply that result by ten thousand kilometers to find the final answer, which should be rounded to the closest integer. Using the simple count example, the change in x is 49 and the change in y is 5. Adding the square of these changes gives 2,426 (49*49 = 2,401, 5*5 = 25, 2,401 + 25 = 2,426), the square root of which is rounded to 49 (√2426 = 49.254). Taking this result times 10,000 kilometers gives a final distance of 490,000 kilometers.
Orbits, Quadrants, and Calculating Distances in Star Systems
As with nav maps, characters utilizing the more realistic solar system model will still need to have a way of determining where exactly Point A and Point B are. In the case of the realistic model, a quasi-polar coordinate system is used to determine the positions of objects within the system; this coordinate system uses quadrants and orbits to determine the locations of objects within the system.Star systems are divided into four quadrants, each of which represents exactly one quarter of the system's total volume. These quadrants meet up at a common point in the exact center of the system's barycenter and are placed along its invariable plane. Quadrants are designated numerically from one to four (or first to fourth, following the terminology used in this discussion) counterclockwise around the orbital plane, with one quadrant arbitrarily designated as first quadrant. As with planetary prime meridians, the designation and boundary planes of a system's quadrants were determined arbitrarily at the time the system was first cataloged; by convention the first quadrant is always located on the upper right-hand side of the system map. Travel time in the system is dependent upon which quadrant(s) the source and destination points are located as is the difficulty of the piloting Check needed to move between them.
All objects that orbit the barycenter in a star system are located within their own orbital lane. Orbital lanes are located at a number of astronomical units from barycenter, which is usually the system's primary (for more details on star system creation, see Chapter 10.2.2). When combined with information regarding the quadrant in which the object is currently located, the orbital lane defines its overall position. Objects in the system that orbit objects other than the primary (such as moons or planetary ring belts) will also have a planetary orbital lane, the purpose of which is also to determine the object's location; the origin point simply changes from the system's barycenter to the center of the object it is orbiting. These objects inherit positional information from their primary object. For example, a planet is located in the third quadrant at a distance of 1.009 AU from its primary. If there is a moon at 1.3 times that planet's Roche Limit (let's say the limit is 54,000 km for the sake of this example), the moon's position is in the Third Quadrant, 1.009 AU from the primary and orbiting at a distance of 70,200 km.
Once again, calculating the distance between two points using the Star System model in WCRPG can be done in one of two ways: a simple way and a realistic way. As usual, the trade-off between the two methods is ease of calculation versus travel difficulty and fuel/time consumption. The GM should prior to the onset of their adventure select which method they'd like to employ.
To use the simple method, the GM must begin by finding the orbital distance of the desired destination and the orbital distance of the vehicle from the destination's primary (if applicable). Subtract the larger amount from the smaller amount. If the destination point is in the opposite quadrant, double the result; if it is in the same quadrant, halve the result (round up). The final result of these calculations is the distance to be traveled in AUs.
The realistic system makes a general assumption about the positions of an object; it is always at the exact midpoint of its orbit through its current quadrant. Similarly, moons are always at the exact midpoint of their journey through the "planetary quadrant" in which it is orbiting. This assumption is made to simplify the trigonometry involved; the realistic method involves translating the coordinates of the object from the polar coordinate system into a Cartesian coordinate system (i.e. into an orthogonal grid). To do this, the value of the cosine and sine of 45 degrees (0.707 in both cases) is multiplied by the value of the orbital distance; the result is the magnitude of the planet's location along both the x and y axis. Depending on the quadrant in which the object is located, the individual values of x and y can be either positive or negative. In Quadrant I, both x and y are positive values. In Quadrant II, x is negative while y is positive. Both values are negative in Quadrant III, while in Quadrant IV x is positive and y is negative. For example, a planet is located in the third quadrant at 1.009 AU. 1.009 times the sine of 45 is roughly 0.713. Since it's located in the third quadrant, the planet's coordinates are at (-0.713, -0.713) within the system. Once the Cartesian coordinates of both the source and destination planets have been determined, the Pythagorean Theorem (√(source x - destination x)2 + (source y - destination y)2) can be employed; the final result should be rounded to the nearest whole integer to get the final distance.
It's generally assumed that the amount of time required to travel to a moon from its primary and vice versa is insignificant compared to the time it would take to travel to the planet; for cases where a craft wants to visit a moon orbiting another planet, the GM may simply use the same travel time it would take to get to the planet. If the vehicle should happen to be orbiting a source moon orbiting another planet, use the travel time from the source planet to the destination planet. The only time that planetary orbital lanes are used is if the craft is going from moon to moon around the same planet. In that case, the same methods that apply for traveling between planets can be employed for travel between them; the planet acts as the primary in this case.
Before a space vehicle breaks planetary orbit or launches from a space station, its crew will need to plot a course to its destination. This destination can be any point in space whether it is in the same star system or not; most destinations will be in the same system unless the vehicle is from an advanced Industrial Age society or if it is preparing a Morvan hop (for more details, see Chapter 8.4). The coordinates of the destination can be compared with the coordinates of the ship's present position (i.e. the source position) to get information on how far away it is using one of the distance formulas discussed earlier in this chapter and how much fuel it will take to get there as discussed in Chapter 8.1. In adventures where the plot requires the characters to go to a specific destination, the GM can have all this information prepared ahead of time. In situations where a GM is running a more open campaign, the players will tell them where they'd like their characters to go; they will then have to calculate the necessary information as rapidly as possible.
To travel within a star system, a vehicle's pilot will either need to make a Vehicle Piloting or Starship Piloting Check depending on whether or not the craft in question is a capital ship. The DC of the Check will be adjusted based on the estimated amount of time required to reach the destination and any "terrain" the GM may be incorporating.
The amount of time it takes to move between two points in a star system depends solely upon the speed of the craft regardless of what system is used to determine the distance. To determine the amount of time required, the GM simply needs to take calculated distance and divide it by the craft's maximum speed; if using the star system model, the distance in AU should be multiplied by 150,000,000 first to convert it into kilometers. The final result will be the time of transit in either hours or seconds, depending on whether the vehicle's top speed is rated in kph or kps; should it be rated in kps, the result should be divided by 3600 in order to convert it into hours. Space vehicles from Starfaring societies may be operated with or without Impulse Engines; a space vehicle may attempt to enter interplanetary space without an Impulse Engine, though if the star system model is being used the amount of time needed to reach another planetary body will be quite significant; the chart in Chapter 8.0 will provide an idea of just how long.
Terrain phenomena may also have an impact on interplanetary transit. Aside from asteroid fields and nebulae, interplanetary terrain phenomena were not part of the original Wing Commander games; a GM may add them to an adventure if they wish either for more realism or to spice things up a bit. The following table lists the potential effects of terrain on the difficulty of a journey through interplanetary space. Unless a phenomenon is listed as having a "system-wide" effect, its effects only come into play if the GM determines that the vehicle will pass within close proximity to the phenomenon (e.g. while a star may have both a Stellar Corona and a Stellar Photosphere, a vehicle doesn't have to worry about either of them unless it gets too close; a Neutron Star located in the same system is going to cause problems even if the vehicle doesn't go anywhere near it.)
|Terrain Name||DC Modifier||Additional Effects / Notes|
|Dust Belt – Diffuse||0||Easy Terrain. Micro-meteoroid damage is possible for each diffuse dust belt the vehicle passes through. In the event of a failed transit Check, the vehicle takes 1d10 points of damage in addition to all other effects from the failed Check.|
|Dust Belt – Dense (Rings)||2||Moderate Terrain. 5d10 points of micro-meteoroid damage occur for each dense dust belt the vehicle passes through regardless of the success or failure of the transit Check.|
|Asteroid Belt||2||Difficult Terrain. Corresponds to a Dense dust Belt (causes 5d10 points of micro-meteoroid damage regardless of the result of the transit Check). In the event of a failed transit Check, a larger rock strikes the vehicle for 8d10 points of damage.|
|Radiation Belt||5||Easy Terrain. Exposes an unshielded crew to interstellar radiation (Armor counts as shielding in this instance); the crew must all roll Fortitude Saves to avoid the effects of radiation poisoning. The radiation can be set to various exposure levels; see Chapter 12.3 for details.|
|Stellar Corona||10||Moderate Terrain. In addition to behaving as a Radiation Belt, 2d10x10 points of thermal damage occurs regardless of the result of the transit Check. If shielding is reduced to zero as a result, an additional 2d10x10 points of thermal damage occurs and the effects of the Radiation Belt are doubled.|
|Stellar Photosphere||12||Extremely Difficult Terrain. In addition to behaving as a Radiation Belt, 5d10x10 points of thermal damage occurs regardless of the result of the transit Check. If shielding is reduced to zero as a result, an additional 10d10x10 points of thermal damage occurs and the effects of the Radiation Belt are quadrupled.|
|Nova||15||System-wide effect; Moderate Terrain. A Nova behaves like a Stellar Corona. It causes 10d10x10 points of damage from the shockwave if the vehicle is in the system when it occurs. On a critical failure of the transit Check in this event, the vehicle is destroyed.|
|Supernova||37||System-wide effect; Very Difficult Terrain. A supernova behaves like a Stellar Corona. It causes 20d10x10 points of damage from the shockwave if the vehicle is in the system when it occurs. On any failure of the transit Check in this event, the vehicle is destroyed. Post-supernova systems may either have a White Dwarf, a Neutron Star or a Black Hole in place of the supernova on subsequent visits to the system.|
|Neutron Star||18||System-wide effect; Difficult Terrain. Extremely Difficult terrain in proximity. A Neutron Star behaves like a Stellar Photosphere; gravitational effects add 1d2 AU to the length of the transit. On any failure of the transit Check, the vehicle is destroyed.|
|Black Hole||50||System-wide effect; Very Difficult Terrain. Impossible terrain in proximity. A Black Hole behaves like a Stellar Photosphere; gravitational effects add 1d10 AU to the length of the journey. On any failure of the Starship Piloting Check, the vehicle is destroyed.|
|Hypernova||N/A||Being in a star system when a hypernova occurs results in the instant destruction of the vehicle under all circumstances. Post-hypernova star systems have a Black Hole in place of the hypernova on subsequent visits.|
|Nebula||N/A|| System-wide effect; Moderate Terrain. Shields will be non-functional while a vehicle is located inside a nebula. +25 DC to all Stealth Checks; +1 Range Increment penalty. A nebula may have additional effects at GM's discretion; suggestions include:
Once the time to the destination has been calculated in hours, the amount of any modifier from terrain features and the amount of any Engine damage the craft has sustained should be added to it; this final amount is subtracted from the Check's DC. Any decimal remainder from the time to destination should simply be truncated. When an Impulse Drive is being used, time does not factor into any DC modification of the Check.
If the transit Check succeeds, the vehicle proceeds to its destination without incident; if it fails, the vehicle will take an additional amount of time to reach its destination equal to the degree of failure in minutes. The Check has critical potential: in the event of critical success, the vehicle will arrive at its destination early by an amount of minutes equal to the degree of success (to a minimum of ten minutes). In the event of critical failure, the Navigator gets the vehicle Lost and as a result the journey takes twice as long as it should have; the vehicle will also have one encounter which cannot be negated by the pilot's Stealth score (see below).
Here are a couple of examples of how interplanetary transit works. Let's say we have a capital ship moving from a planet at coordinates 96x87 on a nav map to a jump point clear across the system at 27x27. Let's further say this ship has a Sixth Class Engine with a top speed of 100 kps and that its Navigator has a Navigation score of 100 (for a +10 DC bonus to all underlying skills) with 25 points specifically in Starship Piloting; this gives us a total DC of 35 for their Starship Piloting Checks. To prepare for the transit, the GM calculates the distance between the two points; the destination is 69 units away along the x-axis and 60 units away along the y-axis. Using simple count, the total distance would be 129 units or 129,000 kilometers; with real count, the distance is reduced to 91,439 kilometers. At 100 kps, it would take 1,290 seconds to reach the jump point using simple count (0.35 hours; 21 minutes and 30 seconds). Similarly, it would take 914 seconds (15 minutes and 14 seconds) to reach the destination with real count. In both cases, since the transits take less than one hour and since we haven't specified any system-wide terrain effects, the DC of the Check would not be modified at all; the final DC would be 35. It would take 26 fuel points to make the journey on simple count and 18 fuel points with real count. Let's say real count was utilized. The dice are rolled; the result is a 04. This is just out of critical success range but most definitely a success, so the ship will proceed to its destination without incident.
The second example will use the System Quadrants image above. In this scenario, a capital ship is at planet "A", which is at 0.177 AU from the system's primary and in the first quadrant. Three other planets are in the system: "B" (0.504 AU, second quadrant), "C" (1.009 AU, third quadrant) and "D" (32.056 AU, fourth quadrant). Using the realistic method for determining distances in the solar system model, this works out to a distance of 0.534 AU between planets A and B, 1.186 AU between A and C and 32.067 AU between A and D. Assuming the ship has a Sixth Class Engine with a normal top speed of 100 kps, it would have a top speed of 7,000 kps when its Impulse Engine is engaged. Doing the math for each of these potential destinations, the transit from Planet A to Planet B will take 3.179 hours, from A to C will take 7.058 hours and from A to D will take 190.783 hours (a little less than eight days). Since an Impulse Drive is being employed, no modifications will be made to the Check DC in all of these cases.
Let's say the ship's captain has been ordered to drop off some listening buoys around the distant planet D. The ship's Navigator has a DC of 36 for the transit Check. The dice are rolled; a 38 results, a minor failure but a failure nonetheless. Two minutes are tacked onto the transit for a final transit time of 190.816 hours (or 7 days, 22 hours, 48 minutes, and 57.6 seconds). With no weather and Extremely Easy terrain, the fuel efficiency will be 1 fuel point per three navigational distance units, 1 fuel point per 0.3 AU in this case. At a distance of 32.067 AU, the ship will need 107 fuel points to make the transit; capital ships have 140 at a minimum, so it definitely has enough fuel to make the journey easily. Once there, it will need three hours and eighteen minutes to refill its tanks back to maximum (or less if planet D happens to be a gas giant and it's equipped with ramscoops).
Encounters in Star Systems
For every hour a craft is in an interplanetary transit, the GM will make a concealed Check of its pilot's Stealth Skill. If this Check fails, the vehicle will have a random encounter in space. If the Navigator fails the initial transit Check critically, one encounter is automatic during the transit; the GM may conduct the encounter at their discretion in this case even if one is not indicated for the hour. These Checks affect the possibility of random encounters only; a GM may always conduct a planned encounter at any point in transit in accordance with the plot of their adventure at their discretion.
If a random encounter is indicated during the course of a transit, the GM will need to determine who or what has been encountered; this needs to be a logical decision based upon the territory in which the craft is currently located. Information on the territorial holdings of various Starfaring Age races can be found in the various sub-chapters of Chapter 2.2. Should the encounter happen in a frontier, unexplored or neutral system, the GM may choose who has been encountered at their discretion; this is a good opportunity to roll out some of the rarer and more unusual craft (such as a Steltek Drone). The GM may also choose to ignore a random encounter at their discretion, though there's not as much fun in doing so.
When setting up an encounter, the GM should consider the current SI of the vehicle and quickly compose a group of encountered craft that come close to matching it. It's generally okay to go under or over the SI as long as the encountered group comes within 100 points either way; any amount substantially below that may be too easy of an encounter while any amount substantially above that may be too difficult. Encounters do not necessarily require combat; an encounter may simply entail hailing and talking to the crew of another craft for a while (a good opportunity to advance a story and get in some good role-playing). Encounters can also simply involve a situation where either vehicle just jets off without bothering to open communications without the other party giving pursuit; there may not be much as much fun in that but occasionally this sort of encounter is appropriate. Of course, depending upon who is encountered, combat may very well be an automatic result (e.g. a Terran craft can pretty much be assured that there will be some shooting going on if it encounters any Kilrathi craft). In case combat ensues, the GM can refer to the combat rules in Chapter 9. During the course of the encounter, Technology Checks may be made as appropriate to determine any vital stats on the opposing group (for more on the Technology Skill, see Chapter 3.8). Encounters terminate when there is sufficient space between all encountered craft or when one group is completely destroyed as a result of combat.
Orbiting, Launching and Landing
Most space vehicles at some point or another will have to return to a safe haven to rotate its compliment, refuel and replenish vital supplies such as oxygen, food, water and carbon dioxide scrubbers. While some species have orbital facilities that can handle these functions, most space vehicles can only accomplish all of these tasks on the surface of a planet. It's therefore important to know what's involved in descending to a planet's surface and what's involved in ascending from the surface.
Orbiting an object in space object such as a star, planet or moon is as simple as keeping a vehicle moving fast enough to compensate for the pull of its gravity. If the vehicle is moving too quickly, it will break its orbit and shoot out into space; too slowly and its orbit will decay. Maneuvering into orbit has been factored into the Check for arrival at a planet or moon after interplanetary transit; orbit is established automatically. Orbit is also factored into the Check for a launch and is also automatically achieved after a successful launch from a planet or moon (as described below).
The key factors in maintaining an orbit are the density of a space object's atmosphere at the altitude of the orbit and its gravitational pull. Space terrain such as rings in the path of the vehicle's orbit can also cause an orbit to degrade prematurely; micrometeoroid impacts will gradually slow an object to sub-orbital velocity if given enough time. To determine how long a vehicle can maintain a stable orbit around an object, a GM may subtract the planet's gravity from 28. From this result, an additional amount is subtracted depending on atmospheric density; for each subsequently thicker atmospheric density category, the GM should subtract the square of an increasing increment (i.e. None=0, Very Thin=1, Thin=4, Moderate=9, Thick=16, Very Thick=25). Finally, if the vehicle was launched from the object in question, the GM must halve the remaining amount. The final result is a number of years that an orbiting vehicle can maintain a stable orbit before it finally decays to re-entry. Orbital decay can be prevented by occasional thrusts of the vehicle's maneuvering thrusters; this is accomplished using a Vehicle Piloting or Starship Piloting Check as appropriate. If the Check is successful, the vehicle returns to stable orbit with its time until re-entry reset to full. Should the Check fail, nothing happens. Only one attempt at a boost may be made per 24-hour period.
Attempting to land a vehicle on the surface of a space object is always a risky proposition; there are many things that can go wrong during the course of a landing, some of which can be quite fatal. A successful landing is never a given. When a vehicle's crew decides that they would like to land, they must first inform the GM of the specific planetary coordinates (see Chapter 8.2) at which they'd like to set down. A transit Check must then be made for the vehicle's descent; the DC of the Check is modified based upon both the object's atmospheric density and its gravity. The modifiers for atmospheric density are listed in the table below; the GM must add to the amount indicated in the table an amount equal to the object's gravity rounded to the nearest whole gee. If the vehicle has any Engine damage, add the amount of the damage to the amount as well. The final result is subtracted from the DC of the Check. If the vehicle is attempting an uncontrolled descent, the DC should be halved (round down).
|Atmospheric Density||DC Modifier|
If the Check succeeds, the vehicle makes a successful descent to the coordinates indicated; an intraplanetary transit begins at that point (see Chapter 8.2). The vehicle may go ahead and land at the coordinates indicated or fly to another position on the planet's surface if it has atmospheric maneuvering capabilities. Should the Check fail, a descent still occurs but the vehicle will take damage in the process. The amount of damage will equal the degree of failure, which may be multiplied if the atmosphere of the object in question is particularly thick; damage is doubled for Moderate atmospheres, tripled for Thick atmospheres and quadrupled for Very Thick atmospheres. This damage is applied to all combat arcs simultaneously and can be absorbed by Shields if they are raised at the time. The Check has critical potential: in the event of a critical failure, a successful descent does not occur and the overall damage from the attempt is doubled.
Launching from the surface of a space object entails a lot of the same risks as landing. The procedure for launching from a space object is the same as attempting to land; only a few of the particulars are different. Launching requires a transit Check with the final DC determined in the same manner as for landing. A successful Check indicates that the vehicle has successfully transitioned into a stable orbit around the object; a failed Check indicates a successful transition to orbit but some damage occurs in the process. The amount of damage is determined the same way as for a failed landing Check. The orbit is also not entirely stable; it will decay to re-entry after one hour. The Check has critical potential: in the event of a critical failure, a successful ascent does not occur and the overall damage from the attempt is doubled. If the vehicle survives the damage, it will be in a Stall in the atmosphere (for details on stalling, see Chapter 9.3); the vehicle will have to successfully recover from the Stall before any subsequent attempt at a re-launch is made.
Launching and landing both burn a fair amount of a vehicle's fuel, usually much more than one can expect to consume during the course of travel between planets. Fuel consumption during launch and landing is solely dependent upon the object's gravity; a launch or landing will consume 1 fuel point per full quarter-gee (e.g. it costs 4 fuel points to take off from the Earth, which has a gravity of one gee exactly). Any vehicle that attempts takeoff without sufficient fuel automatically critically fails the launch attempt; any vehicle attempting to land without sufficient fuel may make the attempt at an uncontrolled entry.