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CRMcNeill
Director of Engineering
Joined: 05 Apr 2010
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Location: Redding System, California Sector, on the I-5 Hyperspace Route.
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 Posted: Sun Feb 17, 2013 9:18 am Post subject: Effects of Gravity on Starship Performance |
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I brought this up in another topic, but it got ignored. However, I'm still interested in hearing people's tak on this:
How should gravity wells affect Acceleration and Maneuverability? Increased acceleration on approach to a planet, and decreased on departure? Bonus to Maneuverability when making a turn in the direction of the gravity well? Varying bonuses based on the size of the gravity well? I know the concept of using gravity slingshot maneuvers has been used in the EU, and I have my ideas for it, but I would appreciate some input.
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jmanski
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| Posted: Sun Feb 17, 2013 10:45 am Post subject: |
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Personally I don't think gravity is worth the time; Star Wars vessels, even the weak ones, are powerful enough to easily overcome gravity even in atmosphere.
Even if it did apply a bonus to maneuver, if in a dogfight both ships would receive it. Unless you're dodging fire from a relatively static ship like a Star Destroyer or something.
I don't know. Gravity is pretty weak, to be honest. Give me some time to think about it.
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atgxtg
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| Posted: Sun Feb 17, 2013 12:28 pm Post subject: |
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Yeah, since they ships can produce a few thousand G's of acceleration, they can easily overcome most gravitational effects.
The exceptions would be things like black holes or when the ship has been severely damaged.
I once ran a black hole in a adventures, and what I did was have the balck hole move all objects 1 space unit towards itself every so often. Just how frequently depending upon how close the object was. For the most part it was just a minor annoyance, Yeah, the players were bothered a little by the black hole and worried about getting sucked in, but since they were far enough out to be pulled in very slowly (like 1 SU per minute or so), it was really a non-issue. At least until they made it one. They got chased by some old a slow fighters and decided to lead them a bit closer to the black hole, and then got a bit clever with a tractor beam, and slowed the fighters down enough so that they got dragged in. |
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garhkal
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Location: Reynoldsburg, Columbus, Ohio.
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| Posted: Sun Feb 17, 2013 1:41 pm Post subject: |
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Well we do know that in the Bacta war novel, the grav well that was raised in the direction of the Lusynkya (the ssd) caused some issues.
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Naaman
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| Posted: Sun Feb 17, 2013 1:46 pm Post subject: |
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| I would say that gravity should only matteer in proxiimity so a significant source, such as a star or massive planet, and then it would always be a penalty, never a bonus, since the gravity is messing with the behavior of the craft, making it more difficult to control. |
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thedemonapostle
Commander
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| Posted: Sun Feb 17, 2013 2:00 pm Post subject: |
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as i recall from some where, gravity's pull is based upon the mass of the object and not their size. though larger objects tend to be heavier, though not always.
now this can be an issue as we dont really know the mass of most ships in the swu, only their cargo capacity.
in truth i think this would seriously slow down game play. as the gm would need the mass of the ship, or equivalent, the strength of the gravity well, the area of effect, the minimum strength and speed to escape the gravity well, and so much more that i cant think out right now because im tired that it would be less of a new game mechanic and more of an exercise in star wars physics.
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Darth Ginzain
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Joined: 25 Oct 2007
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| Posted: Sun Feb 17, 2013 7:21 pm Post subject: |
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| Could always build in gravity into the movement roll. The closer to the planet you are and making combat maneuvers the more the gravity effects the difficulty. And a mishap could make for some fun times as you loss control of your vessel and plunge into the atmosphere. I hear that get's kind of warm if not done at the proper angel. |
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atgxtg
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| Posted: Sun Feb 17, 2013 7:25 pm Post subject: |
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| thedemonapostle wrote: | | as i recall from some where, gravity's pull is based upon the mass of the object and not their size. though larger objects tend to be heavier, though not always |
Yup. Larger object tend to have a higher mass because they ususally are made up of more "stuff". But it's the mass that counts.
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now this can be an issue as we dont really know the mass of most ships in the swu, only their cargo capacity. |
Yup,. although this should give us a decent range to work within. It is very unlikely that a ship's mass would be much less than twice the payload (cargo+crew+food+fuel+air+etc.). It just wouldn't be very sound structurally. On the other hand, it doesn't make sense for a ship to mass more than about ten times it's payload, unless it is a fighter, as it would be fairly inefficent and costly to be moving around all that dead weight. So a reasonable guess would be somewhere in the 2x-10x cargo space.
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in truth i think this would seriously slow down game play. as the gm would need the mass of the ship, or equivalent, the strength of the gravity well, the area of effect, the minimum strength and speed to escape the gravity well, and so much more that i cant think out right now because im tired that it would be less of a new game mechanic and more of an exercise in star wars physics. |
Only in certain special cases. Since the official acceleration for the ship's we've seen has been in the 2000G-6000G range, and that is taking into account what the ship's mass is. Now a Earth-like planet has a gravity of about 1G, and a Sun-like star has a gravity of about 28G, so a ship in Star Wars should be able to easily overcome the gravity of moist object in space. Only black holes and other special cases might cause a significant problem. |
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CRMcNeill
Director of Engineering
Joined: 05 Apr 2010
Posts: 16320
Location: Redding System, California Sector, on the I-5 Hyperspace Route.
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| Posted: Mon Feb 18, 2013 1:46 pm Post subject: |
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But isn't a ship's speed already a measurement of its ability to accelerate its mass? In the case of a high gravity field like a black hole, a simple Move penalty (scaling up by proximity) would be a good measurement of the challenge of calculating the effects of heavy gravity in game terms. Perhaps even make the penalty high enough that some ships would have to use All-Out speed just to off set the penalty. Something like a stock YT-1300 would have to steer well clear (16 SU maximum at All-Out) while something almost all engine, like an A-Wing (48 SU maximum at All-Out) could dive almost all the way down to the event horizon and still have enough power to escape.
There is also the gravity sling-shot to consider. Should a ship receive a bonus to perform a tight turn or a boot-leg when the turn is made around a gravity well? Bonus units or skill bonuses applied against the piloting difficulty when traveling All-out?
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"No set of rules can cover every situation. It's expected that you will make up new rules to suit the needs of your game." - The Star Wars Roleplaying Game, 2R&E, pg. 69, WEG, 1996.
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atgxtg
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| Posted: Mon Feb 18, 2013 4:02 pm Post subject: |
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| crmcneill wrote: | | But isn't a ship's speed already a measurement of its ability to accelerate its mass? |
Yes, exactly.
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In the case of a high gravity field like a black hole, a simple Move penalty (scaling up by proximity) would be a good measurement of the challenge of calculating the effects of heavy gravity in game terms. Perhaps even make the penalty high enough that some ships would have to use All-Out speed just to off set the penalty. |
That's pretty much what I did. The black hole would pull all objects towards it at a rate based on the proximity. At long range, the pull might be 1 SU per hour, day, week, year, whatever. In other words so small it didn't matter to a working ship.
But as you got closer the pull increased to 1 more more SU per game turn, and then it got nasty. An error in judgment could (and did) prove fatal.
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Something like a stock YT-1300 would have to steer well clear (16 SU maximum at All-Out) while something almost all engine, like an A-Wing (48 SU maximum at All-Out) could dive almost all the way down to the event horizon and still have enough power to escape. |
MAybe. I depends on just how fast we consider 1 SPACE movement, and how large 1 SPACE UNIT is. For those who think the Millennium Falcon can make "point five past lightspeed" in realspace then an A-wing might be able to go past the event horizon.
They key is woprking out what type of scale you want. Right now, I'd probably do in according to acceleration in G forces but to me that's easy.
The basic progression is gravity drops off with the square of the distance. So the drop off is pretty quick. I think I set it up as 100 SU pull at 1 SU. So 25 @ 2SU, 11 @ 3 SU, 6 @ 4 SU, 4 @ 5 SU, 3 @ 6 SU, 2 @ 7-66 SU, 1@ 67-200 SU, and so on.
You can see that most ships can maneuver fairly easily even as close as 7 SU.
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There is also the gravity sling-shot to consider. Should a ship receive a bonus to perform a tight turn or a boot-leg when the turn is made around a gravity well? Bonus units or skill bonuses applied against the piloting difficulty when traveling All-out? |
I think it would be a higher difficulty to make the piloting roll, but the pilot would get the extra movement as the reward. |
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garhkal
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| Posted: Mon Feb 18, 2013 5:17 pm Post subject: |
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Yup.. though what would the penalties be for failing the 'gravity sling shot' piloting roll?
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Quetzacotl
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| Posted: Mon Feb 18, 2013 5:29 pm Post subject: |
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1: Entering the Atmosphere of the Planeten at high speed, which leads to damaged systems (maybe 2 controls ionized)
2: Leaving the Orbit to early, resulting in a high velocity in a wrong direction
Well, thats all that comes to mind right now....
Maybe 3: Crash Landing on the Surface because of overheated Engines (or something like that) |
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atgxtg
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| Posted: Mon Feb 18, 2013 7:07 pm Post subject: |
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Sounds about right. You either pull the turn too tight and get caught in the gravity well or don't hold it tight enough and go off in the wrong direction.
For a quick and dirty method, how about +5 (one level) to the maneuver difficulty per SPACE UNIT you want to pick up, and just use the normal mishap table?
One of the perks of this method is that it would allow the pilot to accelerate a bit faster than usual. |
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CRMcNeill
Director of Engineering
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Location: Redding System, California Sector, on the I-5 Hyperspace Route.
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| Posted: Tue Feb 19, 2013 9:09 am Post subject: |
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| atgxtg wrote: | Sounds about right. You either pull the turn too tight and get caught in the gravity well or don't hold it tight enough and go off in the wrong direction.
For a quick and dirty method, how about +5 (one level) to the maneuver difficulty per SPACE UNIT you want to pick up, and just use the normal mishap table?
One of the perks of this method is that it would allow the pilot to accelerate a bit faster than usual. |
Personally, I would use a lower ratio than 5/1. Considering the rarity of a gravity well of sufficient size would be, I would want the pay-off to be a bit higher.
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"No set of rules can cover every situation. It's expected that you will make up new rules to suit the needs of your game." - The Star Wars Roleplaying Game, 2R&E, pg. 69, WEG, 1996.
The CRMcNeill Stat/Rule Index
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atgxtg
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| Posted: Tue Feb 19, 2013 12:38 pm Post subject: |
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| crmcneill wrote: |
Personally, I would use a lower ratio than 5/1. Considering the rarity of a gravity well of sufficient size would be, I would want the pay-off to be a bit higher. |
You could have it apply BEFORE adjusting for speed (cautious, cruising, high, all out). That way a ship that is moving faster would get more out of it.
The thing is, as you can see by looking at the drop off on the black hole, you have to get fairly close to get enough speed to matter in game terms. All well and good until a PC fails a roll and gets caught in the gravity well.
In play, I saw this demonstrated when a ship got destroyed due to ionization. A droid fighter was after the PCs freighter and should have been able to outmaneuver the PC's ship easily, as it has about twice the maneuverability and SPACE. But the ionization hits messed the ship up just enough so that it was dead in space way too close to the black hole.
Something GMs will have to consider is when to apply the black hole movement. It makes a big difference. If it is applied first, then ships can't get very close no matter how good thier engines. If applied second there is still some worries due to sequencing. A GM might just combine them but not worry about where the ship is until the end of the turn, or alternating movement.
Another possilbity might be to trat black holes and other big gravity wells as tractor beams. THe only drawback to this is that tractor beams are resisted by the target's hull in the RAW. Resisting by maneuverability might work here.
For a tractor beam effect, rate the black hole at 1D STR per 400G of pull, and drop the STR in half per doubling of distance.
And, since SPACE units vary in size according to proximity of gravity, you could justifty simplifying the progression a little. |
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