Mechanics for Applying Innate Attack (Air Jet) to Physical Maneuvers

[wathorn]

I have created an Innate Attack (Air Jet) for a character template with the following modifiers: Jet (0%), No Wounding (-50%), No Blunt Trauma (-20%), Double Knockback (+20%).

In addition to the obvious knock back ability, I figured this ability could assist in a number of other actions, like maneuvering in free fall, assisting with jumping, slowing a free fall, or even lifting the character off the ground. To represent all of this, I added Aerobatics (Air Jet) to the template.

However, I still have questions on the mechanics of incorporating this ability into physical maneuvers:

• How much would this Air Jet ability increase the length or height of a jump per level?
• How would using this Air Jet ability help in reducing/eliminating damage from a character's fall per level?
• How much thrust force would this Air jet ability have per level so we can determine what is needed for the character to levitate or fly?
• How would Double Knockback figure into all of that?

Has anyone encountered mechanics like this anywhere, or does anyone have any suggestions?

[awesomenessofme1]

Are you talking about physics or game mechanics? For the first, I don't know. For the second, either none at all or as much as the GM is willing to allow. There aren't rules for anything like that as far as I know.

[Anaraxes]

Strictly mechanically, no effect at all. If you want the other abilities mentioned, buy them (say, Flight) as an Alternative Ability* with the air jet Innate Attack.

Even from the realistic side effect point of view, it's not obvious to me that an attack of high-pressure, focused air, is actually going to have any significant volume or momentum. It's not rocket exhaust or a jetpack, hurling hundreds of pounds of air per second -- more like a cutting machine punching holes. So it's like asking if your 9mm auto pistol can lift you off the ground if you fire it downward, or help you maneuver in free fall.

("No" and "sort of" -- just remember that if the bullet carried enough momentum to significantly change your orbit or spot to which you're plummeting, it'd knock you over if you fired the gun while standing on the ground. The effect from something fully capable of killing you in one shot is still tiny compared to the mass of your entire body.)


--
* that is, 1/5th price -- not -80% -- and can only use one of the abilities at a time.

[zoncxs]

Powers page 162. Abilities enhancing skills.

How much would this Air Jet ability increase the length or height of a jump per level?

+2 or +4 to jumping skill, or if you can calculate it, knock back but upwards added to actual jumping distance.

How would using this Air Jet ability help in reducing/eliminating damage from a character's fall per level?

+2 or +4 for acrobatics skill roll. Or Powers, page 173 "Using abilities at Default".

How much thrust force would this Air jet ability have per level so we can determine what is needed for the character to levitate or fly?

Powers, page 173 "Using abilities at Default".


But really, sounds like you should just buy all of these as Alternate Abilities to the air jet.

Air Jet 18 (Jet, 0%; No Wounding, -50%; No Blunt Trauma, -20%; Double Knockback, +20%; PM, -10%) [36]
Flight (PM, -10%) [8*]
Super Jump 4 (PM, -10%) [8*]

[WingedKagouti]

Originally Posted by Anaraxes

Strictly mechanically, no effect at all. If you want the other abilities mentioned, buy them (say, Flight) as an Alternative Ability* with the air jet Innate Attack.

This is based on one of the core rules of GURPS: You get what you pay for.

If you didn't pay for an ability that lets you fly using your own power, you will need outside assistance to fly. Even if you have a different power that technically should let you fly, if you start calculating how it should interact with the real world. In that scenario you "should" have purchased Flight with apropriate modifiers (possibly as an Alternative Ability).

Now, if you have both Flight and an ability that could plausibly be used for maneuvering (and they're not Alternative Abilities of each other), there's nothing rules wise preventing you from trying to convince your GM that the combination would let you pull maneuvers you couldn't with Flight alone.

[wathorn]

Originally Posted by zoncxs

Powers page 162. Abilities enhancing skills.

+2 or +4 to jumping skill, or if you can calculate it, knock back but upwards added to actual jumping distance.

+2 or +4 for acrobatics skill roll. Or Powers, page 173 "Using abilities at Default".

Powers, page 173 "Using abilities at Default".

Thanks, Zoncxs. I'll look through that and see what works.

Originally Posted by zoncxs

But really, sounds like you should just buy all of these as Alternate Abilities to the air jet.

I see your point (and that of others in the thread), but I foresee my players wanting to use the ability in creative ways (not just to circumvent spending points). In my mind, it makes sense that if a player can shoot a stream of air from his hand strong enough to knock someone back at 10 yards away, then that stream of air can be used in other creative ways that don't necessarily mean knocking stuff down, say holding a door shut with the force of the air stream at a distance or dispersing a cloud of smoke. (Perhaps I should change the ability to a cone effect instead?) Anyhow, I don't mind working with them on that a bit, but I agree that it shouldn't fully replace other abilities, such as flight.

One thing else to ask, though: I just mentioned that the stream of air shoots from the hand, as opposed to, say, the elemental power the character is invoking just manifests in front of him. Aside from finalizing the description, there is nothing in Innate Attack that really says if that should/could be a modifier of some kind. Any suggestions on that?

Originally Posted by zoncxs

Air Jet 18 (Jet, 0%; No Wounding, -50%; No Blunt Trauma, -20%; Double Knockback, +20%; PM, -10%) [36]
Flight (PM, -10%) [8*]
Super Jump 4 (PM, -10%) [8*]

Can you please tell me what the "PM" modifier abbreviation is, please? Thanks

[zoncxs]

Originally Posted by wathorn

I see your point (and that of others in the thread), but I foresee my players wanting to use the ability in creative ways (not just to circumvent spending points). In my mind, it makes sense that if a player can shoot a stream of air from his hand strong enough to knock someone back at 10 yards away, then that stream of air can be used in other creative ways that don't necessarily mean knocking stuff down, say holding a door shut with the force of the air stream at a distance or dispersing a cloud of smoke. (Perhaps I should change the ability to a cone effect instead?) Anyhow, I don't mind working with them on that a bit, but I agree that it shouldn't fully replace other abilities, such as flight.

Easy fix, the pages I mentioned talk about how to do just that. You are looking specifically at using abilities at default. OR! I just remembered, in Supers page...41! Wildcard powers!

Wildcard powers is simple: Define base ability, x4 final cost. Done. Anything they can convince you (the GM) that their underlining power can help do (like you examples of Air jet helping with flight/super jump/falling) works.

Originally Posted by wathorn

One thing else to ask, though: I just mentioned that the stream of air shoots from the hand, as opposed to, say, the elemental power the character is invoking just manifests in front of him. Aside from finalizing the description, there is nothing in Innate Attack that really says if that should/could be a modifier of some kind. Any suggestions on that?

If you want it to shoot from the hand, then that is it. If you want it to shoot from their hands AND them not being able to shoot it from their hands if said hands are bound, then it is worth no more than -5%.

Originally Posted by wathorn

Can you please tell me what the "PM" modifier abbreviation is, please? Thanks

Power Modifier. its what you would tack onto abilities that come from the same Power. For example if the Air Jet was a "Spell" it would have Magic as the PM. Chi Power? Chi as the PM. Elemental? etc.

[WingedKagouti]

Originally Posted by wathorn

One thing else to ask, though: I just mentioned that the stream of air shoots from the hand, as opposed to, say, the elemental power the character is invoking just manifests in front of him. Aside from finalizing the description, there is nothing in Innate Attack that really says if that should/could be a modifier of some kind. Any suggestions on that?

One thing to note is that almost every Power has minor "cosmetic" effects that dictate how they interact with the world outside what is defined by stats and descriptions.

A Crushing IA with the modifiers you give could have different minor cosmetic effects depending on what it is. For an Air Jet, that would likely include interacting with gasses, dust etc., but as a Jet the area affect is fairly small. If the very same (mechanical) ability was instead a Psychic Force manifestation it could potentially react differently to various environments and forces.

Another thing to note is how the Power is used. Does it have to be a specific hand? Eye blasts? Super breath? A shoulder mounted gun that can rotate? Or does the character use some other way to activate it? This is generally not worth any points unless it actively limits (or improves) what the character can do with the ability. Super breath can be used while hands are tied, but will likely be useless if the character is gagged (though it may dislodge/destroy the gag).

[Anaraxes]

Originally Posted by wathorn

Can you please tell me what the "PM" modifier abbreviation is, please? Thanks

It's a placeholder for "Power Modifier". GURPS Powers introduces the concept to try to help give a unified feel to any given source of power -- magic may always have certain limitations like magic words and gestures, chi powers may always need some sort of ritual behavior like mediation or kata, etc., and most abilities have some sort of countermeasures ("dispel magic" stops magic of any sort).

A PM bundles those traits together into a single modifier so you can easily slap that on any ability of a given kind of power.

For no reason other than sheer convenience, GURPS Powers also makes their example PMs all come out to -10%. The book lists a lot of example abilities. But any given ability might reasonably come from any number of different power sources. And just to keep the book a reasonable length and save the team's sanity, all example PMs use that -10% value so that you can just swap out the PM in any example ability to make it a different power source without having to redo all the math. Make up your own powers and associated PMs, and you can have the PM come out to whatever value you like. But you'll usually see an assumption of -10% on the forums, following the trend set by the Powers book.

[AlexanderHowl]

I concur that alternate abilities make the most sense. Of course, you could also justify DR (Physical Only, -20%) by making a temporary shield, Super Throw by using the jet to push a thrown object, and TK by bouncing air streams off nearby objects.