Acceleration-Based Sub-Light Movement

[Reality]

I was re-reading Star Hero last night and wound up writing the attached PDF. I decided that I really preferred acceleration-based movement for my starships rather than velocity-based movement, so instead of Flight I created the Propulsion Power. It costs exactly as much as Flight but has different effects. If a GM wants to use the Propulsion Power but doesn't want to rewrite his existing ships he can apply a +0 Advantage to the Flight Power: Acceleration-Based. That effectively turns Flight in to Propulsion.

 

I haven't play-tested it yet (heck, I just wrote it last night and really haven't taken a step back to see the flaws). Maybe I'm wrong and the RAW for Star Hero work better. I'll leave that up to all of you.

 

[ATTACH]n45074[/ATTACH]

[Christougher]

It's...interesting. Could really use an example with G force(s) and especially a comparison/contrast to doing the same things with Flight. Going to have to read it a couple more times before I can make better comments.

 

Chris.

[bigbywolfe]

I'm pretty sure Terracide had acceleration based movement. Might want to check it out, it's a great setting.

[Xavier Onassiss]

There were early (pre-publication) versions of Terracide in which I experimented with the approach in Reality's pdf, although I didn't get into as much detail. In the end, I found the Hero System had enough optional rules (including those in various supplements) to make the Flight power function the way I needed it to. For simplicity, I took the necessary optional rules (IIRC: Segmented movement, Cumulative flight, Modified turn modes, Fuel dependency) and bundled them into a single -0 limitation. I might have included Side Effects (rocket exhaust) as well.

 

One thing I never got around to was relativistic flight, since it was pretty much unheard of in Terracide. Nice work on that!

[NuSoardGraphite]

Gonna pull this one out of cryo.

 

I did much the same as the topic creator back in the 4th edition days. frankly i'm disappointed that HERO has never done this themselves.

 

I called it Thrust and had it cost the same as flight. in an atmosphere, the noncombat multiplier represented the maximum velocity in an atmosphere. i usually based the non combat multiplier on the type of streamlining the ship possesed. in space however, there was no maximum speed ceiling, unless you count the speed of light. usually fuel limits reduced the max distance it can travel.

[L. Marcus]

I think that Cumulative Flight is the way to go, since this is potentially very much powerful -- a Move Through at orbital velocities ought to be worth more than just a +0 Advantage.

[Cancer]

Umm ... yeah. In Earth orbit, if two orbiting bodies (whose orbits are not nearly identical) collide, the energy yield is Large. Not quite at nuclear weapons blast yield (in terms of energy released per kg of weapon), but getting there.

[NuSoardGraphite]

I think that Cumulative Flight is the way to go, since this is potentially very much powerful -- a Move Through at orbital velocities ought to be worth more than just a +0 Advantage.

Cumulative Flight doesn't really work for me.  Non-combat Flight is already cumulative.  It's just that in space, the non combat multiplier is whatever sets your maximum speed to C.

[Zeropoint]

5e Star Hero had an option wherein hexes of Flight represented acceleration, all ships in space had infinite NCM for free, and some conversion factor from amount of Flight to gravities. "Combat movement" represented how fast the ship could go and still have reasonable real-time control over its motion (obviously not fast enough for interplanetary travel).

 

It seemed pretty good to me, but then, I never actually tried playing or running a game like that.

[L. Marcus]

Cumulative Flight doesn't really work for me.  Non-combat Flight is already cumulative.  It's just that in space, the non combat multiplier is whatever sets your maximum speed to C.

But then, by the rules, you would be under the penalties for NCM -- 0 OCV, ½ DCV. And if you use Velocity-Based DCV, a halving is felt very hard -- from 23 DCV for 8 km/s to 12.

 

I like Cumulative in conjunction with Fuel Charges to represent rockets. Granted, I do use a reactionless thruster in my campaign that has no Fuel Charge, but I arbitrarily capped Cumulative out at +4, which I deemed hefty enough.

[Christopher]

But then, by the rules, you would be under the penalties for NCM -- 0 OCV, ½ DCV. And if you use Velocity-Based DCV, a halving is felt very hard -- from 23 DCV for 8 km/s to 12.

 

I like Cumulative in conjunction with Fuel Charges to represent rockets. Granted, I do use a reactionless thruster in my campaign that has no Fuel Charge, but I arbitrarily capped Cumulative out at +4, which I deemed hefty enough.

Are you certain Velocity based DCV is even affected by NCM halving?

The rules speak of Velcoity giving you "base DCV" so it would be affected, but I always asumed hat since it is velocity based (not on active defense like normla DCV), it would be unaffected by DCV halving.

 

Edit:

As I am not certain about that last part, I asked the question in the Rules Questions:

http://www.herogames.com/forums/index.php?/topic/87634-velocity-based-dcv-and-dcv-modifiers/

 

Edit 2:

We got a ruling now. The DCV modifier for NCM does not affect Velocity Based DCV, but all other modifiers do.

[NuSoardGraphite]

But then, by the rules, you would be under the penalties for NCM -- 0 OCV, ½ DCV. And if you use Velocity-Based DCV, a halving is felt very hard -- from 23 DCV for 8 km/s to 12.

 

I like Cumulative in conjunction with Fuel Charges to represent rockets. Granted, I do use a reactionless thruster in my campaign that has no Fuel Charge, but I arbitrarily capped Cumulative out at +4, which I deemed hefty enough.

But with cumulative flight, you end up with ridiculously high combat movement which allows you to stop on a dime.  Essentially going from 10 g's of acceleration to 0 in a single phase.  That's too much for my purposes.  I want my vehicles to have a limited amount by which they can accelerate and decelerate each phase.

 

And with space vehicles, I use either dogfight or intercept combat.  I don't worry about the halving of DCV due to non-combat movement.  I'm only concerned with the relative velocity, the faster vehicle usually gaining a bonus to the combat piloting roll for determining position on the dogfighting table.

[L. Marcus]

If you stop accelerating, your velocity is still there. That's what Cumulative Flight does, as per 5th ed Star Hero; no dime-stopping, just shutting down the thrusters.

 

And as per Steve's ruling to Christopher's question, Velocity-Based DCV should not be halved for NCM (with leeway for GM call, I suppose).

 

As for the positioning table, if you aren't trying to accelerate away from a foe, a spacecraft ought to be able to present any facing it wants to an opponent.

[NuSoardGraphite]

If you stop accelerating, your velocity is still there. That's what Cumulative Flight does, as per 5th ed Star Hero; no dime-stopping, just shutting down the thrusters.

 

And as per Steve's ruling to Christopher's question, Velocity-Based DCV should not be halved for NCM (with leeway for GM call, I suppose).

 

As for the positioning table, if you aren't trying to accelerate away from a foe, a spacecraft ought to be able to present any facing it wants to an opponent.

I was actually referring to braking, not merely stopping acceleration.

 

With cumulative flight, you can use your now huge Flight movement to essentially stop instantly.  And while this is consistent with some UFO reports and might work well to represent a Reactionless Drive, for a reaction based flight system like a Plasma rocket, it doesn't feel right (to me).

 

a vehicle with a Flight movement of 100" and a Speed of 4 after accelerating for 1 turn has an effective velocity of 400" per phase.  However in order to stop, it would take that vehicle effectively 4 phases to decelerate  to zero.  With cumulative Flight, the same ship would have an acceleration of 400" after 1 turn, but then would be able to exert all 400" of movement to decelerate to 0 in 1 phase and thus, stop on a dime.

 

Thanks for the exercise though.  I now know how I'm going to differentiate between Reaction-based and Reactionless drives.  Cumulative vs non-cumulative.  Awesome.

[Christopher]

With cumulative flight, you can use your now huge Flight movement to essentially stop instantly. 

I know I might be missing the rulebook that Mention Cumulaive for Movement Powers, but at no point would I ever have consdiered that.

 

I mean all we do is Talk about different way to do Newtonian Movement in Space using the Hero System. And one of the core rules of Newtonian movement is that you have to break using your thrust to stop.

[L. Marcus]

I was actually referring to braking, not merely stopping acceleration.

 

With cumulative flight, you can use your now huge Flight movement to essentially stop instantly.  And while this is consistent with some UFO reports and might work well to represent a Reactionless Drive, for a reaction based flight system like a Plasma rocket, it doesn't feel right (to me).

 

a vehicle with a Flight movement of 100" and a Speed of 4 after accelerating for 1 turn has an effective velocity of 400" per phase.  However in order to stop, it would take that vehicle effectively 4 phases to decelerate  to zero.  With cumulative Flight, the same ship would have an acceleration of 400" after 1 turn, but then would be able to exert all 400" of movement to decelerate to 0 in 1 phase and thus, stop on a dime.

 

Thanks for the exercise though.  I now know how I'm going to differentiate between Reaction-based and Reactionless drives.  Cumulative vs non-cumulative.  Awesome.

It seems you've got it backwards -- with Cumulative, Flight basically becomes the Power Acceleration. As per Star Hero, the Flight you buy with the Advantage is the amount with which you can change your velocity per phase --add or subtract.

 

F'rex, I'm building a ship right now, that I want to have fusion torch thrusters with a 1 G (10 m/s) acceleration -- that amounts to 120 meters per phase. The ship has SPD 3, so I buy 40 m of Flight. I want it to have a delta-V of 20 km/s, so I buy it with a Fuel Charge (hydrogen, about half an hour's worth) and Cumulative x500. Now I can accelerate from stand-still to 20 km/s, or get up to 10 km/s and then decelerate back to 0, or any combination.

[L. Marcus]

I know I might be missing the rulebook that Mention Cumulaive for Movement Powers, but at no point would I ever have consdiered that.

 

I mean all we do is Talk about different way to do Newtonian Movement in Space using the Hero System. And one of the core rules of Newtonian movement is that you have to break using your thrust to stop.

There are many ways to skin a cat, as they say, and many ways have been written up in Hero System.

 

The Cumulative for Flight is in Star Hero 5Ed, and I think in Ultimate Vehicle as well.

[NuSoardGraphite]

It seems you've got it backwards -- with Cumulative, Flight basically becomes the Power Acceleration. As per Star Hero, the Flight you buy with the Advantage is the amount with which you can change your velocity per phase --add or subtract.

 

F'rex, I'm building a ship right now, that I want to have fusion torch thrusters with a 1 G (10 m/s) acceleration -- that amounts to 120 meters per phase. The ship has SPD 3, so I buy 40 m of Flight. I want it to have a delta-V of 20 km/s, so I buy it with a Fuel Charge (hydrogen, about half an hour's worth) and Cumulative x500. Now I can accelerate from stand-still to 20 km/s, or get up to 10 km/s and then decelerate back to 0, or any combination.

I just read the section on adding Cumulative in Star Hero.  This makes no sense, because that's how normal Flight works by default.  Check the text of Flight again (or rather, movement in general).  It will tell you that a character (or vehicle) can only accelerate using its Movement in Inches (meters in 6th) in a single phase, so it may take multiple phases to reach its maximum (based on Non-combat multiplier) and that they can only decelerate a number of hexes equal to their movement per phase.  Adding the Cumulative advantage as per Star Hero basically does nothing! (note: unless you are using non-combat Combat Value modifiers for non-combat movement, then the Cumulative advantage allows you to accelerate to high speeds without incurring the penalties)

 

How I would have Cumulative work with movement (which is inherently cumulative, up to a limit of the NCBT multiplier) is The combat move is added to itself, and that becomes your new combat move including acceleration, deceleration etc.  For example, a starship that had 100" of cumulative Flight and a speed of 4 would first accelerate at 100" the first phase.  Then would accelerate at 200" (it's new combat move) the second phase.  The 3rd phase it could accelerate at 400" and the 4th phase it would accelerate at 800".  After the 4th phase, 800" is the vehicles combat movement.  It can add another 800" to its velocity if desired, or it could brake and remove 800" of velocity from it's speed. (stopping on a dime)  That is actually rather perfect for simulating the ridiculous acceleration characteristics of reactionless drives without the need to slap Megascale on it. (though Megascale would probably make the math easier), because otherwise, adding cumulative to Flight doesn't do a damned thing for you...

[L. Marcus]

Hmh. Never thought of it that way. Anyway, my major beef with using Extra NCM Multiples for Newtonian space movement was that NCM has that pesky ½DCV thing attached. But now that Steve has nixed that for Velocity-Based DCV, it might be more convenient all-round to use that instead of Cumulative ...