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Old 09-20-2019, 09:12 PM   #1
awesomenessofme1
 
Join Date: Mar 2016
Default Fall damage and Super Jump

What happens when you have enough Super Jump to have a substantial maximum high jump, but fall from high enough to reach terminal velocity? Logically, you should mitigate that damage somewhat if you're adapted to landing after very high jumps, but as far as I can tell, things like this are never addressed anywhere in the rules.

One idea I had is to determine what height it would take to reach terminal velocity and treat that as an absolute cap when it comes to fall height, and subtract any modifiers you have from that height for the purposes of fall damage.
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Old 09-21-2019, 09:50 PM   #2
zoncxs
 
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Default Re: Fall damage and Super Jump

Falls from less than your high jump distance results in no damage.

To reach terminal velocity requires falling about 70 yards. So if your High jump is less than that, good luck! :D
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Old 09-21-2019, 09:58 PM   #3
awesomenessofme1
 
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Default Re: Fall damage and Super Jump

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Originally Posted by zoncxs View Post
Falls from less than your high jump distance results in no damage.

To reach terminal velocity requires falling about 70 yards. So if your High jump is less than that, good luck! :D
Well, for one, that's quite possible. With Basic Move 8 and Super Jump 6 (or maybe 5, the syntax is a bit unclear), you have a maximum high jump of 68 yd. But also, in such a situation, even though you could fall from a height high enough to reach terminal velocity, if you look just at the RAW, if you fell from a much higher height, you'd still take full fall damage. That doesn't make sense. If you can survive terminal velocity, you should be able to survive terminal velocity, period.
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Old 09-22-2019, 10:50 AM   #4
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Default Re: Fall damage and Super Jump

Quote:
Originally Posted by awesomenessofme1 View Post
What happens when you have enough Super Jump to have a substantial maximum high jump, but fall from high enough to reach terminal velocity? Logically, you should mitigate that damage somewhat if you're adapted to landing after very high jumps, but as far as I can tell, things like this are never addressed anywhere in the rules.

One idea I had is to determine what height it would take to reach terminal velocity and treat that as an absolute cap when it comes to fall height, and subtract any modifiers you have from that height for the purposes of fall damage.
You're presuming facts not in evidence. You are not necessarily adapted to landing from very high jumps just because you have Super Jump. Consider Super Jump with Switchable. If you fall from a distance over your maximum normal high jump distance but within your maximum Super Jump high jump distance with Super Jump switched off, you are going to take the relevant falling damage. In a particular instance, Super Jump might be described as being adapted to making and landing from very high jumps but it's not a given. You might be landing safely because your velocity mystically decreases as you get closer to your landing and that would be just as acceptable an explanation. All Super Jump promises is that you won't hurt yourself by falling your maximum high jump distance.

Terminal velocity depends on several factors including your position while falling. In a random position (such as with arms and legs spread-eagled), terminal velocity for an adult human being is somewhere between 110 mph and 125 mph. For my calculations, I used 120 mph because it simplifies the arithmetic. If you were to be in a tucked, bullet-like position, terminal velocity would be about 210 mph.

210 mph is about 103 yd./sec. and is reached in about 10 seconds, meaning a fall distance of about 533 yards. Long jump distance is always greater than high jump distance for any given iteration of Super Jump and Basic Move, so maximum speed is given as the greater of Basic Move or (Super Jump long jump distance/5). A Move of 103 can be reached with Basic Move 5 and Super Jump 8.

120 mph is about 59 yd./sec. and is reached in about 6 seconds, meaning a fall distance of 192 yards. Using the same reasoning, Basic Move 6 and Super Jump 6 will give a Move of 59.

Here are two notes about capping damage at terminal velocity. First, it's possible, if unlikely, to start out at greater than terminal velocity. If you jump out of a plane that's in a 600 mph power dive, you're going 600 mph straight down until you slow to terminal velocity. If you meet the ground before you're at terminal velocity, well, good luck with that. Second, if you're capping damage at terminal velocity, you should probably cap Super Jump so that (Super Jump long jump distance/5) doesn't exceed terminal velocity.

Last edited by Curmudgeon; 09-22-2019 at 11:09 AM.
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Old 09-22-2019, 10:51 AM   #5
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Default Re: Fall damage and Super Jump

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Originally Posted by awesomenessofme1 View Post
Well, for one, that's quite possible. With Basic Move 8 and Super Jump 6 (or maybe 5, the syntax is a bit unclear), you have a maximum high jump of 68 yd. But also, in such a situation, even though you could fall from a height high enough to reach terminal velocity, if you look just at the RAW, if you fell from a much higher height, you'd still take full fall damage. That doesn't make sense. If you can survive terminal velocity, you should be able to survive terminal velocity, period.
Well, I doubt it will break your game if you rule that being able to avoid damage from terminal velocity means you can fall from any height without taking damage, unless your game has people who rely on dropping enemies from vast height to kill them as a regular feature.
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Old 09-22-2019, 07:46 PM   #6
awesomenessofme1
 
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Default Re: Fall damage and Super Jump

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Originally Posted by Curmudgeon View Post
Here are two notes about capping damage at terminal velocity. First, it's possible, if unlikely, to start out at greater than terminal velocity. If you jump out of a plane that's in a 600 mph power dive, you're going 600 mph straight down until you slow to terminal velocity. If you meet the ground before you're at terminal velocity, well, good luck with that. Second, if you're capping damage at terminal velocity, you should probably cap Super Jump so that (Super Jump long jump distance/5) doesn't exceed terminal velocity.
Care to explain that last part? I don't really see any reason for it. The horizontal component of Super Jump (afaik) doesn't give you any special resistance to damage from collisions, so I don't see the connection.
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Old 09-22-2019, 07:49 PM   #7
awesomenessofme1
 
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Default Re: Fall damage and Super Jump

Also, I thought of a slightly alternative version that might make more sense. Rather than capping damage as damage at terminal velocity, calculate velocity at maximum jump height and subtract that velocity from the velocity with which you hit the ground for the purpose of fall damage. Since you accelerate as you fall, this would be somewhat less effective and would mean that if you started at a higher speed, you'd still get some benefit.
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Old 09-22-2019, 09:42 PM   #8
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Default Re: Fall damage and Super Jump

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Originally Posted by awesomenessofme1 View Post
Care to explain that last part? I don't really see any reason for it. The horizontal component of Super Jump (afaik) doesn't give you any special resistance to damage from collisions, so I don't see the connection.
No, the horizontal component of Super Jump doesn't give any special resistance to damage from collisions, but that's also not particularly relevant. The connection is that you are capping damage at terminal velocity. Damage is related to impulse, i.e. how rapidly the energy changes. GURPS pretty much bakes in impulse as landing on soft or hard ground, leaving energy as the chief variable. Energy is the derivative of momentum, i.e. the rate at which both mass and velocity are changing. In most cases we assume mass is a constant, so energy reduces to 1/2 mv^2. Capping damage at normal terminal velocity is saying that the character cannot, under his own power, exceed normal terminal velocity. If the character can exceed normal terminal velocity, then "if he can jump at 300 mph, his terminal velocity is 300 mph and physics be demned, sir!" The question then becomes "what is his velocity?"

Super Jump says that the speed with which a jump is made is the greater of Basic Move or long jump distance/5. Neither a long jump nor a high jump takes longer than 5 seconds with Super Jump. Assuming a Basic Move of 4, any jump up to 20 yards or 60' is made at Basic Move. For any distance greater than 60' the jump gets faster as well as longer/higher. If terminal velocity is 210 mph, that's slightly less than 103 yds./sec. or Move 103. A Move of 103 yds./sec. puts the maximum long jump distance at 515 yards or 1545'. Any Super Jump exceeding 1545' would also force the character to exceed terminal velocity, thereby violating the damage cap.

It should be added that using Super Jump long jump distance/5 does somewhat underestimate the velocity achieved. Terminal velocity would actually be achieved when the arc length (actual path travelled) reaches 1545' rather than accepting the flat path distance of 1545', which would accordingly shorten the flat path distance.

You can play around with the figures for Basic Move but that's the argument in a nutshell. If you insist on scraping every inch of distance you can out of jumping, you might try substituting Basic Speed for Basic Move in the Jumping formulas. It won't make a huge difference but it won't break anything if you don't mind the fractional calculations.
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Old 09-23-2019, 11:58 PM   #9
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Default Re: Fall damage and Super Jump

I know that I personally can be hurt falling even from 0 ft in the sky, much less getting airborne and adding that additional gravitational potential energy into the mix.

It makes 100% sense to not take damage from falls equal to your max jump height... if you have your feet correctly under you. If you fall onto some other body part, or your feet aren't correctly aligned under you... problems should be possible.
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Old 09-24-2019, 08:14 AM   #10
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Default Re: Fall damage and Super Jump

GURPS already has a mechanic for landing properly - the Jumping/Acrobatics roll that reduces the effective height of the fall. Work out how that compares to jumping height for a Move 5 character (or Move 6 or 7 if you assume things are geared more toward a “heroic average” character), and you’ll see how it should apply to someone with Super Jump (just plug in the character’s actual high jump). I’d do it myself, but I don’t have access to my books currently.

Note this requires a roll to avoid the damage - it doesn’t matter that your legs can handle an “instant” deceleration of 200 mph if you land on your back. Being immune to falling should probably use a modified Walk on Air. Note I’d allow (indeed, require outside something like 4-color Supers) a properly-oriented Super Jump landing to deal slam damage to whatever was landed on, but not to the landing character. As the legs are obviously really good at absorbing the impact, I’d use half slam damage. Note landing on an irregular surface, like a person, probably calls for a retroactive penalty to the Jumping/Acrobatics roll (or perhaps a penalized reroll). If going for gritty realism of some flavor, I’d probably have the surface jumped off of take similar damage (which can be rather problematic for the jumper if the surface can’t handle the jump).

Doing such damage without hurting yourself when landing on your back or similar would require sufficient DR and/or IT:DR to soak the slam damage.
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