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Alternate Space Travel Rules For Science Fiction Settings

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  • Alternate Space Travel Rules For Science Fiction Settings

    Previously I posted a set of optional rules for space travel under a different name (Old rules here: ). After reviewing them I noticed that some of the distance ranks were off and the movement rules were a bit complicated. They also didn't quite mesh with the rest of the M&M system in some areas. I'm posting the cleaned-up version of those rules here, and will probably post a revised and complete version of the setting in a different thread.

    I've split the rules into three sections for ease of reading and in case anyone wants to copy-pasta them.
    Last edited by Ian Wright; 1st March 2016, 02:21 PM.

  • #2
    Re: Alternate Space Travel Rules For Science Fiction Settings

    Space Distance and Speed Ranks

    Speed of Light: 299 792 458 metres per second = Rank 28
    Note: The Speed Powers guide suggests rank 29 for light speed. This is off, probably as a result of the way M&M rounds large numbers.

    Light Second (ls): 299 792 458 metres = Rank 26
    Astronomical Unit (au): 149 597 870 700 metres = Rank 35
    Light Year (ly): 9 460 730 472 580 800 metres = Rank 51
    Parsec (pc): 3.261 ly = Rank 53

    Sol to Alpha Centauri: 4.37 ly (1.34 pc) = Rank 54

    Astronomers use parsecs for interstellar measurements, but the light year is more common in science fiction and better known among the general public.

    Distances in the Solar System
    Mercury: .39 au = Rank 33
    Venus: .72 au = Rank 35
    Earth: 1 au = Rank 35
    (Earth to Moon: 384 400 km = Rank 26)
    Mars: 1.5 au = Rank 36
    Ceres (Largest asteroid belt object): 2.7 au = Rank 37
    Jupiter: 5.2 au = Rank 38
    Saturn: 9.5 au = Rank 39
    Uranus: 19 au = Rank 40
    Neptune: 30 au = Rank 40
    Pluto (Large Kuiper Belt object): ~40 au = Rank 41
    Oort Cloud: ~10 000 au = Rank 49

    When travelling between two objects in the Solar system, use the distance rank of the outermost object.

    Galactic Distances
    Orion Arm: ~3 500 ly across, ~10 000 ly long = Rank 63 across, Rank 65 long
    Sol to edge of Galactic Centre: 26 000 ly/8 000 pc = Rank 66
    Galactic Diameter: 100 000 to 120 000 ly = Rank 68
    Last edited by Ian Wright; 1st March 2016, 02:25 PM.


    • #3
      Re: Alternate Space Travel Rules For Science Fiction Settings

      Space Travel

      Slower Than Light (STL)

      Space Flight: 2 pp per rank
      Most STL space engines can't operate in planetry atmospheres or gravity wells. For space engines that operate both in and out of atmosphere, buy an Alternate Effect.

      Over short distances or in tactical movement, Space Flight operates under the standard M&M movement rules. Over long distances space travel is ruled by acceleration and deceleration time. Determine how long the space ship will spend in acceleration, and add the time rank directly to its Space Flight speed ranks: This gives you the ship's maximum speed. Subtract maximum speed rank from distance rank to determine how long it takes to do a fast fly-by of the destination. If you want to decelerate to stop at the destination, add +1 to the final time rank.

      Example: A ship with Space Flight 5 is going to travel 2 au, distance rank 36. If it spends a day accelerating then it's maximum speed rank is (Speed rank 5 + time rank 14) rank 19. Distance rank 36 - Maximum speed rank 19 = Time rank 17, or roughly one week. This lets the ship do a fast fly-by of its destination without stopping, still moving at speed rank 19. If the ship had also decelerated to stop at the destination the trip would take (Time rank 17 + 1) time rank 18, or roughly two weeks.

      It's easy to track and target spaceships moving all-out along ballistic arcs. All spaceships take on the Defenceless condition during the acceleration, coasting, and deceleration phases of long-distance travel.

      Maximum speed rank is limited by available technology. Using the d20 Progress Level scale re-labeled to 'Tech Levels' to avoid confusion with Power Levels, Tech Level 5 is equal to the present day.

      Tech Level = Maximum Speed Ranks
      TL 5 = 16
      TL 6 = 19
      TL 7= 22 (0.015, ~1.5% speed of light)
      TL 8 = 25 (0.125, ~12-13% speed of light)
      TL 9 = 28 (0.999, ~99+% speed of light)

      These maximums are for the ships typically available in the setting. Experimental high-speed ships or ships backed by massive infrastructures can reach a maximum velocity equal to one TL higher (At TL 9 ships are already up against the fundamental speed limit of the universe, and should probably use a wormhole or other FTL system if they want to go any faster).


      Fades: This flaw can represent rockets that are fueled by tanks of compressed gas. Cold gas thrusters may also have the Subtle extra, since their extremely low infrared signature makes them hard to spot.

      Unreliable: The 5 Uses Only variant represents a ship with extremely limited reserves of reaction mass. Each 'use' represents one time rank for purposes of acceleration and deceleration. A ship with this flaw can accelerate for a maximum of 5 time ranks, but if it wants to stop at its destination it should accelerate for 2 time ranks, decelerate for 2 time ranks, and reserve the rest of its fuel for orbital or docking manoeuvres.

      Faster Than Light (FTL)

      FTL Move costs the same as Flight: 2 pp per rank. In almost all settings it doesn't function at all in atmosphere or within a certain distance of a planetary mass, but this doesn't count as a Limitation. It's just a feature of the setting.

      Some FTL drives work by jumping a ship between two linked points. For jump drives that instantly transport a starship from Point A to Point B, only one rank in FTL Move is needed. Settings that use this option include Lois McMaster Bujold's Vorkosigan Saga or Jerry Pournelle's CoDominion/Empire of Man stories.

      In other settings ranks in FTL Move give the starship a very high effective speed, but typically only for travel between star systems. Often starships need secondary engines to move around within star systems. The effective speed of Rank 1 FTL Move is set by the GM according to the scale of the campaign. Some sample effective speeds for Rank 1 FTL Move are given below:

      1 ls/year = Effective speed Rank 3
      1 ls/month = Effective speed Rank 7
      1 ls/week = Effective speed Rank 9
      1 ls/day = Effective speed Rank 12
      1 ls/hour = Effective speed Rank 16

      1 au/year = Effective speed Rank 12
      1 au/month = Effective speed Rank 16
      1 au/week = Effective speed Rank 18
      1 au/day = Effective speed Rank 21
      1 au/hr = Effective speed Rank 26

      1 ly/year = Effective speed Rank 28
      1 ly/month = Effective speed Rank 32
      1 ly/week = Effective speed Rank 34
      1 ly/day = Effective speed Rank 37
      1 ly/hour = Effective speed Rank 42

      1 pc/year = Effective speed Rank 30
      1 pc/month = Effective speed Rank 34
      1 pc/week = Effective speed Rank 36
      1 pc/day = Effective speed Rank 39
      1 pc/hour = Effective speed Rank 44

      Some settings have FTL drives that are slowed as they approach planetary or stellar masses. The effective speeds in light seconds and astronomical units are presented for those settings. The 2300ad RPG setting has 'stutterwarp' drives that function at FTL speeds in deep space (FTL Move Rank 1 = Effective speed 33), drops to slower-than-light in the outer reaches of a star system (FTL Move Rank 1 = Effective speed 17), drops again in the inner reaches of a system or approaching a planet (FTL Move Rank 1 = Effective speed rank 8), and is completely disabled for orbital manoeuvres or take-off and landing.

      Other settings have FTL drives that pick up speed as they approach massive objects. Star Trek's warp drives get a speed boost from stars and black holes. In cases such as these give the starship a +2 environmental bonus to effective speed at the outer edge of a system and a +5 within the inner system. Neutron stars of black holes may be worth up to a +10 bonus if you get really close, but coming anywhere near such objects can be incredibly dangerous. In settings like this, major lanes of traffic centre around massive stars where cargo vessels can take advantage of the speed bonus to reduce travel times and costs.

      In the examples above the bonuses or penalties to stardrive effective speed are worth no points. They're a common feature of the game setting and every starship is subject to the same rules. Some settings have more than one way to travel faster than light, and each drive has its own advantages and disadvantages. In those settings each drive has its own cost and some drive technologies might be secret, recently discovered, or owned by megacorporations or restricted by governments.


      Activation: Drives that take time to kick in after being powered up can have this flaw.

      Check Required: A good option for finicky starship engines. A drive might need a Technology or Expertise: Stardrive Engineering check to activate its full speed, or it might need an Expertise: FTL Navigation check to bring it close to the proper destination.

      Distracting: Starships that travel through a dangerous hyperspace or require constant monitoring to avoid running into sublight debris might have this flaw.

      Feedback: Some settings require one or more people (Usually psychics, sometimes mystics in magitech settings) linked to the engines. These people may be subject to feedback if the ship is attacked or otherwise damaged.

      Slow: A Quirk worth a flat -1 pp, this flaw restricts the starship to the low end of its speed rank range. This is typically only 50% faster than the top range of the next speed rank down.

      Example: At effective speed rank 34, a starship can normally travel up to 125 000 000 km per week. With this Quirk it would be restricted to a maximum of 96 000 000 km per week, 50% faster than effective speed rank 33.

      Unreliable: Extremely finicky drives with a habit of failing often might have this flaw. If a stardrive requires exotic materials such as metastable hydrogen or antimatter to power it, then a starship with limited fuel tanks could have the 5 Uses Only variant. Refueling can usually only be done at specialized facilities and may be expensive, a possible Complication if the PCs are too broke to afford the docking and fueling costs.


      Expensive: These stardrives have high fuel costs or maintenance costs, or possibly both. Often they require exotic materials to act as fuel, or have extremely high power requirments that require frequent powerplant repairs. PCs will usually struggle to keep their ships flying.

      Fuel Required: A less restrictive form of Unreliable: 5 Uses Only. In some settings stardrives need fuel or some sort of mass to convert into energy fields. Usually this mass is something like water or hydrogen, which is generally easy to find but time-consuming to pump into fuel tanks. If the material is costs more than simple water, see Expensive below.

      Hazardous: The drive might produce dangerous levels of radiation when in use or require toxic materials, forcing anyone working around the drive to wear protective gear. Alternatively the drive might create an environmental hazard, posing a threat to anyone near the ship.
      Last edited by Ian Wright; 4th March 2016, 01:10 PM. Reason: Cleaned up the acceleration rules


      • #4
        Re: Alternate Space Travel Rules For Science Fiction Settings

        Ship Design and Major Systems

        In space-oriented campaigns spaceships and starships should be designed as constructs, since those rules offer more flexibility than the standard vehicle rules. See the Gadget Guide entry for mecha for more detail. Gargantuan (Size rank 1) or larger ships can also have Rooms, like headquarters.

        For very detailed settings, or in settings where the difference between freighters and fast or heavily armed ships is a major factor, use the Major Systems option. Under this option each major system reduces the ship's carrying capacity by one rank, representing the extra mass and volume of the system (If the ship has rooms like a headquarters, each pp spent on rooms counts as a major system). A ship with Strength 20 has a carrying capacity of 25 kilotons, but if it had 3 major systems the carrying capacity would only be (20 - 3) rank 17 or 3.2 kilotons. A cargo freighter and a warship might both have Strength 25, but the freighter has minimal facilities onboard (and could even be completely automated) reserving most of its capacity for 100 kilotons of cargo while the warship is loaded with weapons and defences and only has capacity for 800 tons of cargo.

        Exactly what makes up a major system depends on the GM and the details of the setting. As a rule of thumb any system that requires a significant portion of the ship's volume or mass is a major system. Rooms are always major systems, taking up one point of capacity per pp. Other possible major systems include:

        Weapons with Damage greater than series PL
        Weapons that require ammunition supplies (Missiles, guns, attack drones)*
        Active defences (Force fields, point-defence systems, ECM)
        Impervious passive defences (Hardened armour or heavy deflectors)
        Survey or other extreme-range sensors, ECM counter-measures
        FTL Move^
        Space Flight*
        High-capacity supercomputers
        Anything the GM feels should take a lot of space in their setting

        * Weapons at or below series PL that are limited to 5 uses are too small to take up any significant space except on the tiniest of ships. Space Flight with ranks below 1/2 series PL and that are limited to 5 uses also take up no space.
        ^ In some settings FTL drives are extremely compact regardless of power, while in others faster systems take up more space. It depends on the campaign setting.
        Last edited by Ian Wright; 2nd March 2016, 08:39 AM.


        • #5
          Re: Alternate Space Travel Rules For Science Fiction Settings

          I like this, although, I probably wouldn't use it in a heroes game set in space, as its too involved.

          Question though, can you give some examples of tactical combat with STL drives? It looks like either most ships would have perception range weapons, or this system would end up with the problem of 'combat is one round long as the two enemies whip past each other' unless they are fighting VERY shortly after starting to fly through space.
          Ragtop, Autobot! And Zeanthara, Are You a God?
          Fenix, in the Merge, and Alicia DeVries, in the Cosmic Merge
          Supe of the Justice League Academy


          • #6
            Re: Alternate Space Travel Rules For Science Fiction Settings

            I'm still crash-testing my ideas for space combat. In general the solution to the whole 'zoom past one another at high speeds' problem is to have sensors and weapons with very long ranges. Perception-range attacks are a possibility, but they feel a bit too accurate for most SF-adventure settings. I need to sit down and game out a few rounds of combat though.

            And yeah, for a superheroes game or any other game where space travel is a minor point, these rules are definitely too involved.


            • #7
              Re: Alternate Space Travel Rules For Science Fiction Settings

              I'd be interested in helping you with that if you're looking for help. Also, have you read any David Weber? He (and his fans online) discuss that problem in great depth, and come up with a variety of solutions. However, those solutions are based around a novel, with a lot of control over all characters. For a game with players, you may want to lay out a particular version of space travel that works better for combat (probably based on jump technology).
              Ragtop, Autobot! And Zeanthara, Are You a God?
              Fenix, in the Merge, and Alicia DeVries, in the Cosmic Merge
              Supe of the Justice League Academy


              • #8
                Re: Alternate Space Travel Rules For Science Fiction Settings

                I'd definitely welcome any thoughts on this. Part of my problem is I've made so many notes about ranges, times to close, and extended ranges, that they're all starting to run together in my head. Even the notes that contradict each other. Especially the notes that contradict each other.

                My thought about Perception ranges being too accurate is mainly a gaming concern. Weapons in some visual media do seem to be Perception attacks: Shoot and hit, with only armour or forcefields to save you. But in those shows the main characters are protected by the writers. PCs have no such plot armour, and it's not a fun game experience when your opponent can autokill you because they have one more rank in extended sense than you.

                ETA: I haven't read Weber, but I know his stuff. It's a little too specific for a set of generic options, but it's a good example of how to pick your technobabble to get the feel you want.


                • #9
                  Re: Alternate Space Travel Rules For Science Fiction Settings

                  Okay, looking through my notes what follows was the simplest solution to the problem.

                  In a cluttered environment ranges, movement, and combat work exactly as presented in M&M. Cluttered environments include dogfights, the tactical space around space stations or major asteroids, or orbital space around planets. Movement is confined by the environment and there's lots of other junk flying around to deal with, and the pilot and targeting computer are struggling to deal with everything. So weapons are restricted to extremely short ranges (Standard M&M ranges) by environmental overload.

                  In open space weapon ranges are all increased by 1000 (+10 on the ranks table) due to improved tracking and targeting opportunities. So weapons that previously had ranges measured in metres now have ranges measured in kilometres. In open space combat takes the shape of fly-by attacks: Ships open up on one another from long range, briefly zip by one another as they exchange broadsides, and then continue to exchange fire until they move out of range. This is basically a +0 pp modification, since it only applies in one limited environment and it's more of a setting feature than an extra on the attack.

                  A weapon with Ranged Damage 12 and 2 ranks of extended range has standard ranges of 400/800/1 600 metres. In open space that increases to 400/800/1 600 kilometres.

                  You can combine the two environments as well. Example: As a fleet approaches a military platform the ships and platforms open fire at extreme ranges, continue to fire as the fleet flies past and drops fighters and boarding craft, and then go back to briefly shooting at one another until the fleet is out of range. The focus then shifts to the small craft in the cluttered space around the platform, with attacking and defending fighters blasting at each other at close range while the fleet manoeuvres to turn around. The fleet will then come back for another pass, either taking control of or destroying the military platform (Depending on its orders) or picking up the surviving small craft it dropped off earlier.

                  Like I said, this is the simplest (and most consistent) approach to the problem I came up with. I haven't had a chance to test it yet though.


                  • #10
                    Re: Alternate Space Travel Rules For Science Fiction Settings

                    Follow up question: on a planet, in a cluttered environment, there is a practical limit to extended range/perception. However, in space, especially the uncluttered variety, it would be very easy to have a VERY long range.

                    Any suggestions on how to avoid that, or just a big warning to GMs to have some sort of guideline so one side doesn't have a huge range advantage?
                    Ragtop, Autobot! And Zeanthara, Are You a God?
                    Fenix, in the Merge, and Alicia DeVries, in the Cosmic Merge
                    Supe of the Justice League Academy


                    • #11
                      Re: Alternate Space Travel Rules For Science Fiction Settings

                      Offhand, I'd say that the warning/guideline approach is the simplest and most in line with M&M's design philosophy: "Yes, you can do this. Bear in mind doing so will almost certainly wreck your game."


                      • #12
                        Re: Alternate Space Travel Rules For Science Fiction Settings

                        What about using closing speed to increase range instead of adding 10 ranks?

                        That way, both sides get a huge boost (the same boost). Make your weapons ranges the higher of your normal or that granted by closing speed?
                        Ragtop, Autobot! And Zeanthara, Are You a God?
                        Fenix, in the Merge, and Alicia DeVries, in the Cosmic Merge
                        Supe of the Justice League Academy


                        • #13
                          Re: Alternate Space Travel Rules For Science Fiction Settings

                          Originally posted by Nelphine View Post
                          What about using closing speed to increase range instead of adding 10 ranks?

                          That way, both sides get a huge boost (the same boost). Make your weapons ranges the higher of your normal or that granted by closing speed?
                          At TL 5 (The lowest tech level on the scale) maximum closing speed is rank 23. 23 doublings of a rank 12 weapon gives a close range of 838 800+ kilometres, which is a bit complicated. On the other hand, normal ranges for a rank 12 weapon are 100/200/400 metres or distance ranks 4/5/6. Add 23 to those and you get distance ranks 27/28/29 (1 million km/2 million km/4 million km). That second option is a lot easier, but I'm not sure how to justify adding closing speed to beam weapon ranges. I do like this option for making closing speed matter and for giving a balanced bonus to both sides. Maybe make it 1/2 closing speed + weapon range ranks?

                          What would be entirely realistic is to add closing speed to ballistic weapon damage, but damage 12 + 23 = yikes!


                          • #14
                            Re: Alternate Space Travel Rules For Science Fiction Settings

                            Thinking about it a bit: I'd suggest keeping the range bonus for open space as a flat x1000/+10 for simplicity's sake. It's easy enough to justify that as a combination of ECM and general clutter affecting ranges.

                            For a lethally realistic option, add +1/2 closing speed ranks (round down) to ballistic weapon Damage ranks. The leaders of the opposed forces can make Expertise: Space Tactics checks to see who has the final advantage on closing speed and angle of attack, with the winner receiving a +1 tactical bonus to damage (+2 at 5+ degrees of success). The leader of the fastest force receives a +2 equipment bonus to their Expertise: Space Tactics check. Bearing in mind that Damage bonuses of +11 or higher will turn most armoured spaceships into eggshells trying to withstand sledgehammers...


                            • #15
                              Re: Alternate Space Travel Rules For Science Fiction Settings

                              My reason for doing the either or is game balance:

                              If I buy extended range 4, and you don't, and I have a damage rank 12 vs your rank 6 multiattack, I have 32 times your range. In normal play, that doesn't come up a lot. In space, that could be a LOT of turns you don't fight back. And that level of range doesn't seem threatening to most GMs (I would guess).

                              By making the closing speed range completely independent of the weapon rank/range, you can be sure people can fight back. Only way to outrange people, is to buy very large amounts of extended range, to the point most GMs will notice it on creation.

                              As to why it applies to beam weapons: the extra range is literally your opponent flying into the attack, as opposed to your weapon traveling further. Also remember its closing speed. So your speed might be 23, but your opponents is also 23. That makes both of you have range 24.

                              Hum, without the weapon rank that's really low.

                              Maybe keep the 'add 10' rule in addition.

                              So my gun has extended 4, rank 12. Yours is rank 6. We're both closing at 23.

                              Either I can fire at 400'x12 + 10 ranks (or a little under 1000 miles), or I can fire at rank 34. Similarly you can fire at 25' x 6 + 10 ranks (or ~30 miles) or you can fire at rank 34.

                              Obviously with our closing speeds, just going with +10 ranks still only gives one round of combat, since we're closing at around a speed 64 times my range.

                              Ugh. So, +10 ranks doesn't come close to the speeds we could reach, but +10 ranks on closing speed means fight to the death because once in range it'll take us 3 hours to get out of range.

                              Last edited by Nelphine; 1st March 2016, 06:48 PM.
                              Ragtop, Autobot! And Zeanthara, Are You a God?
                              Fenix, in the Merge, and Alicia DeVries, in the Cosmic Merge
                              Supe of the Justice League Academy