Gliding

jedion357's picture
jedion357
April 16, 2011 - 7:09pm
Remaster AD wrote:

Yazirians can glide short distances using the membranies along their sides. A yazirian can glide 1 meter for every meter he is above the ground when he starts. He must start at least 10 meters above the ground. The maximum distance a yazirian can glide depends on the gravity of the planet, as shown below.

Yazirian Gliding Table
 Gravity Max. Glide
 .6G 150m
 .7G 100m
 .8G 50m
 .9G 25m
 1.0G 10m

Yazirians cannot glide on planets with gravities below .6 or above 1.


Question #1: Does the max glide distance make sense? if a yazirian jumped off an 100m building in 1.0G would he only glide 10 meters? Does he suddenly fall to the ground after 10m? I've always interpreted that table as the max glide result is the distance traveled for trading 10m of hieght. (I've argued with a player over this, which was silly since I was the referee and my ruling benefited his character).

Question #2: how far can a yazirian glide in a turn? Or rather, at what speed does a yazirian glide? It doesn't seem right that a yazirian in 1G would only travel 10m while another yaz in .6G would travel 150m in the same time. What I'm getting at is if say gliding speed is 50m per turn then a yazirian in 1G would travel 50m in a straight line while dropping 50m altitude in one turn and a yazirian in .9G will travel 50m horizontally while dropping 20m of altitude in the same turn.

Question #3:Then we have issue of what happens in a steep dive? What if the Yaz opts to drop more distance faster?

Question #4:Then we have what happens if a yaz tries to make an attack while gliding? To glide he must keep his arms and legs out stretched. but to aim a pistol or throw a weapon will cause a loss of glide surface and should result in loss of altitude.
I might not be a dralasite, vrusk or yazirian but I do play one in Star Frontiers!
Comments:

thespiritcoyote's picture
thespiritcoyote
April 16, 2011 - 9:16pm
Players with a deathwish... tsk tsk tsk....

as a quick fix I would say:
1. yes, some unit of elevation is droped, per the distance of glide given on the table,
2. at the speed of a jump/leap per turn, if the 150m a turn is bothersome in 0.6G, but that is quite a difference in gravity, how realistic idk
3. they just need to be able to pull out of the dive, with enough time to regain contol at the new altitude, otherwise they enter an uncontrolled dive in the next round..... *splat*
4. the origional thought was that they didn't have any gliding attack option other than maybe a diving tackle or lace, it also was not suposed to be as graceful as flying by any means.

 "Falling with style!" is probably the best quote for the Yazi's Glide.
 What happens if they are on a 0.6G world and get a good power jump clearing 10m? (possible? how probable?)
 What if they run faster than their falling rate?
 What if on a 1.G world they 'open sail' from a vehicle traveling at twice their falling rate?

 I challenge the believability of the 32foot requirement, minimum of three stories seems extreamly unrealistic to me, especially in lowered gravities. I know it could be explained and hand-waved into fitting, but thats not my point.
Oh humans!! Innocent We discover a galactic community filled with multiple species of aliens, and the first thing we think about is "how can we have sex with them?".
~ anymoose, somewhere on the net...

so...
if you square a square it becomes a cube...
if you square a cube does it become an octoid?

Deryn_Rys's picture
Deryn_Rys
April 16, 2011 - 9:37pm
Why not amend it to have a Yazirian travel said distance and then roll a Dexterity check and if successful they can remain aloft and can travel that distance again before requiring another check but at a penalty of -5/previous check made or they have to land.
"Hey guys I wonder what this does"-Famous last words
"Hey guys, I think it's friendly." -Famous last words
"You go on ahead, I'll catch up." -Famous last words
"Did you here that?" -Famous last words

thespiritcoyote's picture
thespiritcoyote
April 16, 2011 - 11:33pm
feels too much like flying, I like 'falling with style'
very little control after the inital launch,
either glide or fall, distance predictable
turns are wide, catching wind from a
vehicle or using a weapon is dangerous

I do agree with the inital height of glide needing review
a simple extra collum, to give a distance droped over the distance traveled,
an inital speed set by a leap distance,
keep checks to things like pulling out of a dive, useing a weapon, or not having your membranes riped off and eating dirt when launching from a vehicle.
Oh humans!! Innocent We discover a galactic community filled with multiple species of aliens, and the first thing we think about is "how can we have sex with them?".
~ anymoose, somewhere on the net...

so...
if you square a square it becomes a cube...
if you square a cube does it become an octoid?

Georgie's picture
Georgie
April 17, 2011 - 5:03am
I don't see how horizontal speed could be much faster then walking or, at best, running speed. I'd also suggest forgetting the Max Glide table. How far you glide depends on starting altitude, horizontal speed, and gravity (and wind factors too, if you like). Gravity should impart a Fall Speed based on meters per turn. I suggest gravity * 10, i.e. 1g = 10 m/t, .6 g = 6 m/t. Thus you can glide horizontally at 10-30 m/t while falling at 6-10 m/t. It's not perfect, but better.

Also, a yazarian can do nothing else while gliding without plummeting like a human.
The weak can never forgive. Forgiveness is the attribute of the strong.    * Attributed to Mahatma Gandhi

jedion357's picture
jedion357
April 17, 2011 - 5:28am
Heres the thing for me if you can glide 10m why cant you glide 20m? all he has to do is maintian his arms and legs outstretched and continue trading height for distance. 1g is not going to suddenly strip a yazirian of his ability to keep his arms outstretched. air flowing over a wing doesn't suddenly stop flowing- as long as the yaz is trading height for distance there will be air flow.

As to flying, if you jump off the Pan Gal building in down town Port Loren and its 200 meters then you have 200m distance that you can travel in Gran Quivera's 1g but you are not flying because you can hover or gain altitude- you are going down.
As to diving for speed and pulling out to regain some altitude- the glider will never regain the original altitude. For myself I'd say that in 1g with its 10m for 10m a yaz cannot dive. Then in the other gravities more double the hieght dropped and cut the distance travelled in half. Require a straigtline dive (otherwise DEX control checks must be made). If the yaz never pulls out of the dive he hits hard and takes damage (this could be intentional like a diving tackle to slam an oponent- requiring a Dex check to hit, damage is calculated and both take it and use grenade bounce table to place them a number of meters from the spot the target was standing that is equal to 1 meter/ 10meters of height used in the dive)

If a yaz pulls out of the dive he makes a DEX control check to do it successfully, he'll regain 1/2 the height used in the dive and end up any where within a radius equal to the same ammount of height he's regain. EXAMPLE: a Yaz is gliding a 100m in .7g and initiates a dive trading 50m height for only 75m distance. When he pulls out he will gain 15m height and will end up any where within 15m of the pull out spot.

Interestingly: Hargut in Gruna Garu system has 1.1g nixxing gliding for its population.

for combat: to throw or shoot requires a dex check to do so and a Dex check to not go into an uncontrolled dive but either way making an attempt to shoot or throw something, whether he failled the first Dex Check and wasn't able to perform the attack, the yaz will still loose 10m height.
I might not be a dralasite, vrusk or yazirian but I do play one in Star Frontiers!

jedion357's picture
jedion357
April 17, 2011 - 5:30am
The big question is what would be the speed of unpowered glide?

How fast does the bat man suit travel that was used in that stunt to glide across the English Channel?


I might not be a dralasite, vrusk or yazirian but I do play one in Star Frontiers!

thespiritcoyote's picture
thespiritcoyote
April 17, 2011 - 10:15am
As for gliders never regaining altitude..
two words: Air Currents.

Cities are notoriously full of updrafts and thermal pockets. Best places to go gliding, if only it was considered safe.

A good example of what the Yazi have as a natural advantage are the gliding suits.
http://www.youtube.com/watch?v=UE7i9ycE9PQ
there have been alot of diligent researchers, conducting extensive field experments, on the Yazi gliding potintial in the decades since those rules were printed.
http://www.youtube.com/watch?v=I34oAZ3dH6c&feature=related
The 'science' just wasn't availiable at the time.
http://www.youtube.com/watch?v=l1TJ28ujIi4&feature=related
I still favor a mechanic that keeps a feeling of static falling, stunts and extended air-time checks kept at a miniumum, with serious risk involved in anything other than a simple controlled decent.
http://www.youtube.com/watch?v=VmIDXk2J5_U&feature=related
http://www.youtube.com/watch?v=-TH7asP574k
most of the time, the extreme distances make for extreme speeds, landing becomes more dangerous the more you push the Yazi into exteme potintial.

two points: The Yazi are not as stream-lined as these suits
                 The Yazi may be able to 'glide' on instict, but that instict is concerned with minimizing risk, not maximizing awesomeness.

http://www.youtube.com/watch?v=6cOSF2MGVzc&feature=related
http://www.youtube.com/watch?v=w5gmK-ZXIMQ&feature=related
The Flying Squirrel, and Flying Lemur, are still far better examples of the baseline than the Flying Marine...

My understanding of the Yazi glide:
Any turning is wide, even at low altitude and increases risk of glide fail... tighter the turn far higher the risk...
distance droped is very quick, the 32foot height requirment suggests a minimum of three story drops per turn in 1.0G, distance traveled is not a factor in the baseline here.
Power put behind the launch does increase speed, and thus the 'safe' distance traveled horizontaly in the given time.

The question: should a Flying Lemur (even one 1m tall) be able to launch off a 55-story, 200meter(656ft), building and glide safely to the ground?
Surprised no!
Safely glide to a landing platform say, 60 meters away and 60 metters down? maybe, but not without risk of glide fail and certaintly not the same building!
Diving 60meters down the side of a building to land on another platform? Surprised omg! no!
Control a tight 30m wide spiral around a building?.... un`uh, no way!
fire a gun? or launch a javelin?... nope and nope.

Dive & tackle someone on the ground from 30ft up... sure!
a running target? maybe.
a vehicle moving faster than a leap/jump launch speed? no way!
not realisticly.
want to add anime FX? sure, but not as a guide set for realisim.
want to add elite security gaurds to protect the Emerald City, that defy the risks, with extreme skill and an unhealthy tendency to ignore self-preservation insticts? do that too, but these elite gaurds loose lots of trainees, and quite a few gaurds trying to be the best.  (not that they care, thats what makes them the best, the elite! and everyone else is either weak, or a hero.)
Oh humans!! Innocent We discover a galactic community filled with multiple species of aliens, and the first thing we think about is "how can we have sex with them?".
~ anymoose, somewhere on the net...

so...
if you square a square it becomes a cube...
if you square a cube does it become an octoid?

Deryn_Rys's picture
Deryn_Rys
April 17, 2011 - 10:30am
The ruling I proposed above reflects that a Yazirian as a natural glider would be able to extend his glide by making a dex check which would reflect his turning his body in such a way to catch an updraft. In game terms it isn't like flying because a flying creature does not have to roll a stat check to keep flying unless conditions change drastically and offer the possibility of the creature falling. Thus a Yazirian jumping from the Pan Gal tower would glide ten meters and make his dex check to continue gliding for ten more meters. after this he rolls a Dex check at -5 to extend his glide another ten meters where he must again rol with a -10 penalty. The penalty reflects that he is not only trying to catch the next thermal, but fighting gravity as well.

I think this system does not negate any of the rules in the cannon books but offers a way to extend a Yazirians flight within the context of those rules, and its simple too which is a plus.
"Hey guys I wonder what this does"-Famous last words
"Hey guys, I think it's friendly." -Famous last words
"You go on ahead, I'll catch up." -Famous last words
"Did you here that?" -Famous last words

jedion357's picture
jedion357
April 17, 2011 - 10:42am
so what I read spirit C making a case for is severe limits and when the table says max glide distance it means it and no other monkey business allowed- so a glide is a 1 turn move? even at .6g?

I'm still with Deryn on this flight time isn't goint to magically end though in 1g an extended glide will likely have high enough speed to hurt on landing. I forget what the falling damage rule is but what if we added a column to the table of max glide that would be the damage suffered per additional 10m drop, Dex control check per additional drop.

The way I'd compute the damage would be 1/2 what you'd get per 10m fall in that gravity.

but then we'd still have to allow the yaz a braking manuever to pull up and dump speed through either a stall climb or speed shedding turns.

This of course brings us back to how much distance a character can glide in 1 turn.

I might not be a dralasite, vrusk or yazirian but I do play one in Star Frontiers!

Deryn_Rys's picture
Deryn_Rys
April 17, 2011 - 10:47am
I also want to state that a Lemur is an instinctual glider, a creature of animal intelligence while a yazirian is a very intelligent higher life form with an understanding of thermals, updrafts, drag, areodynamics etc.  so while the lemur mught instictively wiggle its body and arms in a controlled fall, the Yazirian would know how to calculate his movement to take the most advantage of his glide.
"Hey guys I wonder what this does"-Famous last words
"Hey guys, I think it's friendly." -Famous last words
"You go on ahead, I'll catch up." -Famous last words
"Did you here that?" -Famous last words

thespiritcoyote's picture
thespiritcoyote
April 17, 2011 - 11:17am
I am not suggesting that the flight ends abruptly, but that the speed of the fall ends the life of the poor daring Yaz rather abruptly, and the difficulty in avoiding a fatal-failure after 'safe-glide' is exceeded is severe.

I mentioned that, about instict vs. intelect, over coming a sense of self preservation. and the risks in just attaining the necessary skill to press the envelope.

My over all opinions are based on three points:
Gliding is not flying, and the ability to control a glide is limited to that of controlled falling.
Mechanics should be represented in static form, and rely on few if any dice rolls.
Skills might increase the potintial, but to small effect and at great risk.
Oh humans!! Innocent We discover a galactic community filled with multiple species of aliens, and the first thing we think about is "how can we have sex with them?".
~ anymoose, somewhere on the net...

so...
if you square a square it becomes a cube...
if you square a cube does it become an octoid?

iggy's picture
iggy
April 19, 2011 - 11:03pm
It is not appropriate to compare menbrane gliding to wing gliding.  The membrains are more like a parachute than a wing.  Yazirians are using their membranes to arrest the fall more than anything.  This is the same as what is shown in the videos that spiritC posted.  The vertical distance traveled per turn is much greater than the horizontal distance traveled.  For the human in the wingsuit it was 32 feet per minute vertical for 3 feet horizontal in the same minute.  That's about a ten to one ratio.

As for catching updrafts, the wind speed must exceed the falling speed to gain altitude.  At something not much less than 10 meters per second added speed each second gliding.  The updraft quickly turns into a very strong wing to gain lift.

This physics of this can be figured out.  I just need to do a little study first to understand how to calculate the extra drag of the yazirian wing membranes.
-iggy

thespiritcoyote's picture
thespiritcoyote
April 19, 2011 - 11:37pm
32 feet drop is equivalent to the 10m height requirment,
 which means they get better than 1m horizontal per 10m in vertical at least...
 or within the charts precalculation, they already out-perform a marine in a wingsuit!Surprised
 by around a factor of 10!Foot in mouth
 seeing that alone makes it impressive, and fully settles the 'natural ability' factor, for me.
Oh humans!! Innocent We discover a galactic community filled with multiple species of aliens, and the first thing we think about is "how can we have sex with them?".
~ anymoose, somewhere on the net...

so...
if you square a square it becomes a cube...
if you square a cube does it become an octoid?

iggy's picture
iggy
April 19, 2011 - 11:59pm
As I read the rule and table for 1G a Yazirian can glide a max of 10m horizontal by starting at a 20m height.  I would rather rework the rule to some physics than keep it as is because I don't like the 10m minimum height to start nor the 1 to 1 vertical to horizontal rule after that.  But I need to investigate some about parachute drag or something close to it before I could properly rework the rule.
-iggy

thespiritcoyote's picture
thespiritcoyote
April 20, 2011 - 11:08am
A yazirian can glide 1 meter for every meter he is above the ground when he starts. He must start at least 10 meters above the ground.
 jedion357

I belive that means that a Yazi needs to be 10m up, to gain the 10m max glide, in 1.0G.

And the chart works out such that:
Yazirian Gliding Table
 Gravity Max. Glide
 
Vertical Start/Horizontal Glide
 .6G 150m
1m:9m
 .7G 100m
1m:7m
 .8G 50m
1m:4m
 .9G 25m
1m:2.5m
 1.0G 10m
1m:1m

The base line given thus:
 For the human in the wingsuit it was 32 feet per minute vertical for 3 feet horizontal in the same minute.
 iggy
   Is equivalent to a 10m drop for every 1m horizontal, per minute, in 1.0g...... and suggests the drop per minute is calculated on a flat ramp, in 0.6g a 1m drop for every 9m horizontal distance....
  further suggesting that in 0.6g only 1m start height achieves a 9m glide, and in 1.0g a 1m start height would acheive a 4 inch glide, better to jump/leap for lower altituides than 10m anyway.

   I don't think a Yazi (especially, and specifically, an untrained Yazi as the base chart is want to reflect), should be considered capable of out-performing a trained marine in a wingsuit, focused on pushing the envelope, for research into daredevil extreme-jump conditions.
   However, a hard-corp trained, highly dedicated, and somewhat insane Yazi, in the Hentz Planetary Defence Marine Corp, out perfroming everyone else, I wouldn't argue with, I like my arms in their sockets.

check my math Foot in mouth please! My slide-rule is in the shop....Laughing
Oh humans!! Innocent We discover a galactic community filled with multiple species of aliens, and the first thing we think about is "how can we have sex with them?".
~ anymoose, somewhere on the net...

so...
if you square a square it becomes a cube...
if you square a cube does it become an octoid?

TerlObar's picture
TerlObar
April 20, 2011 - 3:35pm
"AD rules" wrote:
Yazirians can glide short distances using the membranies along their sides. A yazirian can glide 1 meter for every meter he is above the ground when he starts. He must start at least 10 meters above the ground. The maximum distance a yazirian can glide depends on the gravity of the planet, as shown below.

Yazirian Gliding Table
 Gravity Max. Glide
 .6G 150m
 .7G 100m
 .8G 50m
 .9G 25m
 1.0G 10m

Yazirians cannot glide on planets with gravities below .6 or above 1.


Here's my 2 centicredits worth. 

I take that to mean that for any type of gravity, the glide path is a forty-five degree angle, i.e. 1 meter distance for 1 meter dropped.  So on a 1.0g planet, you climb up 10 m and jump and you end up 10m away from your starting point.  If you climb up 10m on a 0.6g planet and jump, you will still end up 10m away.  However, on that 0.6g planet, you could climb up 150m and jump and travel 150m away and still not be going too fast when you hit the ground.  If you tried the 150m jump on a 1.0g world, you might still travel the 150m but you would go splat at the end.

I defnintely don't think it means that you could jump from 10m altitude on a 0.6g planet and travel 150m.

I also agree that there should be a more sensible mechanic that would allow you to define what the effects would be if you did make that 150m jump on a 1g world.  Yazirians are bigger and lighter than humans so even without their wing membranes, they'd have a higher drag coefficent and therefore a lower terminal velocity in a straight fall.  The wing flaps would server to increase the drag and therefore slow them down.  Hence the gliding ability.  I'm interested in seeing what iggy comes up with on the parachutes and such.

At 1.0g it takes ~1.43 seconds to fall 10m in a vacuum.  Air resistance on the human body would make that take fractionally longer.  The wing flaps would make it take longer still.  So I'd say as a guess off the top of my head, the 10m drop on a 1g planet for a Yazirian gliding would take about 2 seconds at most (subject to iggy's findings), or a third of a turn.  I'll use two seconds for the following:

For a two second drop, that means that the wing flaps reduce the effective acceleration from 10m/s^ to 5m/s^2.  i.e. cutting the effect of gravity in half.  Assuming it is the same for the other gravities (and I'm not sure it is, I'll have to dig out my physics books and look up drag) we get the following table:

 Gravity 
 Distance 
 Time 
 Final Speed 
 0.6 150m10.0 s
 30 m/s
 0.7 100m 7.6 s 26.5 m/s
 0.8 50m 5.0 s 20 m/s
 0.9 25m 3.3 s 15 m/s
 1.010m
 2.0 s 10 m/s

Even 10m/s is pretty fast (about 22 mph) but 30 m/s would definitely not feel good.  To keep the landing speed to 10 m/s the maxium distance would just scale inversely with gravity.  The maximum distance would just be 10m divided by the gravity.  So on an 0.8g planet the max distance would be 10m/0.8 = 12.5m.

Now I need to go look up drag and see what the real math would be.
Ad Astra Per Ardua!
Webmaster - The Star Frontiers Network & this site
Founding Editor - The Frontier Explorer Magazine
Managing Editor - The Star Frontiersman Magazine

thespiritcoyote's picture
thespiritcoyote
April 20, 2011 - 4:27pm
That actually makes A LOT more sense, but is counter intuitive to the way the chart is written, the chart seems to suggest at a glance, that you get an exponential distance increase in a lower gravity.... yea that seems wrong to the physics, tho' I supose it makes sense to someone.

I admit to getting that totally wrong.

I would like to see a resolve that takes a baseline account of what is possible before training and stuntman attitudes. Then add the attitude and skill factors, to bring it up to reflect a Trained Yazi Planetary Marine or Paratrooper. So that the basic rules need little moding to reflect an average Yazi ability, assuming that the base chart can even be considered that realistic.
Oh humans!! Innocent We discover a galactic community filled with multiple species of aliens, and the first thing we think about is "how can we have sex with them?".
~ anymoose, somewhere on the net...

so...
if you square a square it becomes a cube...
if you square a cube does it become an octoid?

TerlObar's picture
TerlObar
April 20, 2011 - 6:55pm
Okay, now I've looked up the physics and math and think I have a pretty good working model.  There are two questions that remain.

First, is what is the working surface area for a gliding Yazirian?  For a human it is something on the order of about 0.6-0.7 square meters.   Now Yairians are taller plus they have the wing membranes, all of which contribute to increase the surface area.  So the question is, how much surface area do we give the wing membranes?

The second question is how fast can you be going and safely land?  Military paratroopers are trained to land at a speed of 6 m/s which translates to about 13.4 mph.  This is the speed of jumping off a 6 ft wall.  That seems like a reasonable value.

If we really want to make this work, I think we'll have to come up with a reason to allow for a faster landing speed.  Limiting the landing speed to 6 m/s and even giving them a surface area of 3 m^2 which seems high, on a 1.0g planet you get a distance of just under 2 meters and on a 0.6g planet you get a distance of 3.5m.  The fall time is just around one second in both cases (0.64 and 1.11s respectively) and the extra drag from the wings in only starting to take effect at those velocities.

This assumes that we are just talking about increased drag (i.e. falling with style) and that no lift is generated by the wing membranes.  I'll look in to that some more as well but my gut feeling is that on this short timescales and distances, it's not going to have much effect.

As a side note, the wing membranes seriously decrease the terminal velocity.  For humans on earth terminal velocity is around 50 m/s.  For a Yaz on a 1.0g world and a 3 m^2 surface area, terminal velocity is only 14.75 m/s


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thespiritcoyote's picture
thespiritcoyote
April 21, 2011 - 12:10am
What is the patagia/body ratio of a lemur? The spread they have seems suitably realistic, and somewhat better formed, and larger than the wingsuit.

Measuring directly from the pictures, I am getting, about 2.5 times the height in width, and approximately equal height to length. I can not find an official measurement. Thats a flat total square area of around 8m to 12m, adult Yaz, by a direct size comparison. Considering the pictures of the Yazi patagia hanging loose around them, and the efficiency of an organic compacted patagia, it isn't entirely unthinkable that it could extend considerably.

  Keeping it at around 6m/s landing speeds sounds good, allowing daredevil skills to increase that some would be fine. Stunt checks to trade drop speed for distance and visa-versa would also work ok. *splat* damage can be easily worked out for failed rolls from there. Kinetic-suits and screens will make up for a considerable amount of the difference, after that.
  That tech being accountable for PC heroics, there is no need to feel like the basic calculations need to side on the survivability of Yazi with a self destructive urge.
  Altho' my earlier imagery of a Yazi launching from the back of a fan-cycle is Epic-Awesome, if every Yaz in a skiensuit could fearlessly do it, it would be rather tame...

Question on this so far, are we not assuming a six-second glide? Personally I think six seconds combat actions are too long, and I prefer 3sec actions. But what is the idea about that part of OP - Q#1 and #2listed max-glide in one combat round, or something else?
Seems that if the 10m glide is intended to be 6sec long and not 2sec long, the drop and final speed, would be slower than whats on your chart. Also wouldn't the decreased gravity decrease final speed?
Oh humans!! Innocent We discover a galactic community filled with multiple species of aliens, and the first thing we think about is "how can we have sex with them?".
~ anymoose, somewhere on the net...

so...
if you square a square it becomes a cube...
if you square a cube does it become an octoid?

iggy's picture
iggy
April 21, 2011 - 2:16pm
I think we have to take into account the change in air density that happens with lower gravity.  I guess we assume 1 atmospheric pressure for a 1g planet and then do the equivalent standard atmospheric pressure for each planetary g we are interested in.  Then ignore the differences created by weather and altitude on the atmospheric pressure.
-iggy

TerlObar's picture
TerlObar
April 21, 2011 - 3:32pm
Yes, I was ignoring the decreased density for now.  That actually makes it harder to glide on the lower gravity planets.Smile  i.e. you fall fasters as there is less drag and less lift for the same velocities.
Ad Astra Per Ardua!
Webmaster - The Star Frontiers Network & this site
Founding Editor - The Frontier Explorer Magazine
Managing Editor - The Star Frontiersman Magazine

jedion357's picture
jedion357
April 21, 2011 - 4:12pm
RE: landing velocity and pushing it higher, I would be for allowing a yaz a dex check to perform the yaz equivelant of a PTF (Parachute landing fall) to displace the energy of the landing over the whole of one side of his body rather than just on his feet.
I might not be a dralasite, vrusk or yazirian but I do play one in Star Frontiers!

thespiritcoyote's picture
thespiritcoyote
April 21, 2011 - 8:07pm
I could see that also, dex is a good base for reduction of damage, a little like a tumble, but skill should still factor for success. It does often require a considerable amount of training to pass that part of the class, to the satisfaction of an instructor. Base dex to reduce damage, skill to properly execute the manuver and reduce further, say half-damage without skil,l increased to nearly nothing with a high skill, seems appropreate. That way it isn't a pure 'hit or miss' but rather still shows that the skilled know how to eleminate the risks.... but might still fumble and snap a leg.

What about the max-glide per combat round? The way it reads it is vauge on that, but seems to Imply, that the intent had a Yaz start and end the combat-round on some surface, and not in mid-air.
Oh humans!! Innocent We discover a galactic community filled with multiple species of aliens, and the first thing we think about is "how can we have sex with them?".
~ anymoose, somewhere on the net...

so...
if you square a square it becomes a cube...
if you square a cube does it become an octoid?

iggy's picture
iggy
April 22, 2011 - 12:10am
OK.  I am now studying drag and lift to understand the relationships to falling Yazirian style.  In the simplest this is just balancing forces to the point that the Yazirian does not hit the ground too hard.  I swipped the following from a website on parachutes for Estes rockets.  We compute the force of drag FD and balance it with the force of gravity FG.

FD = ½ r Cd A v2

Where
FD is the drag force
r (Greek letter "rho") is the density of air = 1.22 kg/m3
Cd is the drag coefficient
A is the area of the chute
v is the velocity through the air

Meanwhile, the weight of the rocket, otherwise known as the force of gravity (FG), is computed to be

FG = m g

Where
m is the mass of the rocket
g is the acceleration of gravity = 9.81 m/s2

Let's find when they're equal:

FG = FD
m g = ½ r Cd A v2

Basically this is the terminal velocity calculation reorganized.  We need to calculate the drag coefficient for a Yazirian with spread wing membranes.  Then substitute for gravity and the density of air at the given gravity.  The result of this will be a table of Yazirian terminal velocities when naturally parachuting straight down.  We can then go back and calculate what max safe drop heights are for each gravity.

I said that I am now studying lift because the above approach does not account for it.  It assumes stagnate air and that the surface of the falling object does not act as an airfoil.  I think that most players don't want their Yazirian characters to be slaves to the wind and expect their Yazirians to actually glide a bit even in stagnant air.  Thus I am assuming that a Yazirian can configure his wing membranes to act as an airfoil.  How much of an airfoil (how efficient) depends on how far we all feel that a Yazirian should be able to glide for a given height in a 6 second turn.  While we are agreeing on this I will research lift and then we can work the equations backwards to determine the natural Yazirian lift that produces the agreed upon horizontal glide distance.

Following that then we can tweak the results to account for special training, high dex, etc. to increase the horizontal distance.

I am really interested in what TerlObar comes up with on this topic too.

Final note.  I would think that this natural ability of Yazirians would have given them an edge on developing gliders.  Powered flight might have been more on par with our Human history as the source of power (gasoline engine) would hamper the change from glider to powered flight like our history did.  The Yazirians however are likely to have had gliders for possibly hundreds of years before powered flight.
-iggy

TerlObar's picture
TerlObar
April 22, 2011 - 6:12am
I followed basically the same path as Iggy (Although I grabbed my college physics books instead of the internet).  Using just drag, I came up with the results in my earlier post.  I then looked into lift but realized I set it up wrong on my first attempt so I'm redoing that now and balancing the forces properly.  If I get a chance I'll get it all worked out tonight (I was chasing kids around to activities all night last night).  BTW, iggy, for a "falling" yazirian with its wings extended, I considered it, to first approximation, to be equivilent to a flat plate perpendicular to the air flow.  In this case Cd is 1.28.

The force from lift is given by (using iggy's notation) L=rAKv2 where K is a proportionality constant that describes the efficency of the airfoil (typical values around 0.12), r is the air density, A is the wing area and v is the speed of the gliding yazirian.

I also grabbed a paper (Aerodynamic force generation, performance and control of body orientation during gliding in sugar gliders [a type of flying squirrel]) that has a bunch of information and charts on a real life gliding creature to provide some context and sample values.  I haven't had a chance to read it yet but it looks like it will provide some good information.

In any case, the main problem I'm seeing in the calculations, is that since both drag and lift are proportional to velocity squared, you need to be going really fast to get any benefit and by that time you've already splatted or are going too fast to be safe.  More to come after reading about flying squirrels.
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iggy's picture
iggy
April 22, 2011 - 9:49am
I too ended up researching sugar gliders, flying squirrels, and then colugos http://en.wikipedia.org/wiki/Colugo trying to find some basis for a creature to model from.  Flying squirrels are better than sugar gliders and it seems that colugos hold the record.  TerObar's Cd of 1.28 seems to line up pretty good with numbers I was seeing for squirrels but I would think that Yazirians would do better than squirrels.

Terobar, I would like to read the same paper your reading about sugar gliders.  I'm heading to my parents in Vegas this week end and need some on the road reading.  I'm bringing my physics book.
-iggy

TerlObar's picture
TerlObar
April 22, 2011 - 5:00pm
Sent you the paper via e-mail.  I'm not so sure they would have a higher Cd since that seems to be about the limit for a flat surface against an air flow.  Most other things have smaller coefficients.  I guess the other thing to compare it to is a parachute.  Any idea what the drag coefficient is for one?
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thespiritcoyote's picture
thespiritcoyote
April 22, 2011 - 7:45pm
It isn't apparent in the frontal view given with the Yazirian, close inspection, and proportional measurements, of all the concept art, including the one in the species wirte-up, shows that it is the Philippine Flying Lemur that is the basis of the structure and coloration, not a chimpanzee.

http://en.wikipedia.org/wiki/Philippine_Flying_Lemur

Since I don't have the physics books to determine the aerodynamics to such a precice calculation, I have studied the visible anatomy more closely, and concluded that the frontal views shown in the 'disected Yaz' are in fact the result of a anthropomorphized Kagwang in parallel projection.

I'll be attempting a full 3d model based on these measurments soon, to see how closely I can reprodunce the parallel projection view, and the various conceptual artworks, from the same base model.

Question #1: Does the max glide distance make sense? if a yazirian jumped off an 100m building in 1.0G would he only glide 10 meters? Does he suddenly fall to the ground after 10m? I've always interpreted that table as the max glide result is the distance traveled for trading 10m of hieght. (I've argued with a player over this, which was silly since I was the referee and my ruling benefited his character).

Question #2: how far can a yazirian glide in a turn? Or rather, at what speed does a yazirian glide? It doesn't seem right that a yazirian in 1G would only travel 10m while another yaz in .6G would travel 150m in the same time. What I'm getting at is if say gliding speed is 50m per turn then a yazirian in 1G would travel 50m in a straight line while dropping 50m altitude in one turn and a yazirian in .9G will travel 50m horizontally while dropping 20m of altitude in the same turn.

Question #3:Then we have issue of what happens in a steep dive? What if the Yaz opts to drop more distance faster?

Question #4:Then we have what happens if a yaz tries to make an attack while gliding? To glide he must keep his arms and legs out stretched. but to aim a pistol or throw a weapon will cause a loss of glide surface and should result in loss of altitude.
 

A1: As a max-glide for 10m of height it would be somewhat extreme. Allowing such a 1 to 1 drop ratio without any difficulty accrued from starting height, would in my oppinion be very unrealistic... I wouldn't be entertained with such a stunt given a common-place attitude in a movie, even less thrilled with such a stunt being common-place in an rpg. My chart from earlier was based on the same 45 degree drop, however it does seem that a Yazerian still gliding after the six-second combat round, would need to attempt some sort of check to maintain a safe glide. On this it is still of my favor to keep some sort of static-mechanic base chart, and not a dice roll-every-round dynamic, and leaving skill rolls to the dare-devil stunts and envelope-pushes, where risk is of even more concern.
  On a skiing trip someone once said to me "Amateurs tend to make a fall look like they survived a fatal accident, while experts tend to apear to make minor mistakes that put them in traction."

A2: It would 'seem' that the intent of everything in the book was a simple distance in six-seconds glide, but 150m does appear to be an unrealistic speed, if I am understanding the effects of a 0.6g atmosphere and rate of fall. This part is of concern to ma, because I was in a game where the GM ruled that the entire glide must begine and end in one combat-round, that you can not 'end your turn in the air' as it were, and I argued that this made no sense, and in a game I ran I had a player insist that his non-milita, basic street plebe, Yazirian could jump from a 200m building without any risk.

A3:
I cover this one as a stunt, a roll to enter a controlled dive, a role to pull out and stabalize, or properly cushion before impact on a target. This isn't something I see the typical Yazi doing withot a special skill to reflect the ability, and is dangerous enough that most sane Yazi wouldn't try without good reason and training. Inate bravery and 'battle rage' be damned to the obvioulsy suicidal, I don't equate bravery with stupidity, and I believe the Yazi brave, not insane.

A4: Again I consider this a stunt, but with less difficulty inherent than the former, as it is only a momentary attempt to sight a target from the current position and condition, I would allow one attempt to stabilize for an oportunity of a shot, and heavier penelties to the shot if failed.
A critical failure to properly stabalize for the shot being rare enough, the attempted shot with severe penelty can still be made, as the Yaz enters an uncontroled fall, resolved in the next round, one chance to cushion or stabalize, after a severe decent, in that case.
A simple non-combat skill in glide-stunts would cover this, but not necessarily the dive. The dive being in most cases combined with a tackle, rake, or air-lance type attack in practice, or considered simply too dangerous and unnecessary for simple movment effects, should be considered a seperate, more advanced, skill in glide-aerobatics.

This is my opinion for what it's worth, I am interested in what others might come up with, while I like realisim, some room for theatrics is still appreciated.
My gut says the gravity influence shown in the chart is either a bit backwards, or simply over-simplified and lacking any realisim.

http://climbpeak.blogspot.com/2011/02/what-is-philippine-kagwang.html
Spit'n'image of a Yazi cub.Cool
Oh humans!! Innocent We discover a galactic community filled with multiple species of aliens, and the first thing we think about is "how can we have sex with them?".
~ anymoose, somewhere on the net...

so...
if you square a square it becomes a cube...
if you square a cube does it become an octoid?

TerlObar's picture
TerlObar
April 29, 2011 - 11:12am
Okay, here's an update.  (You're going to get a bit of a physics lessonSmileKiss)

I was able to produce a model that (very nearly) reproduced the flight characteristics of the flying squirrels and sugar gliders using basic physics so I'm fairly confident it is correct or at least close enough.

The main parameters that affect the gliding are:
g - gravitational accelration (I used 1g=10 m/s^2)
m - mass of the glider (AD states that this is 50kg on average for a male Yazirian)
p - atmospheric density (I used 1.2 kg/m^3, a typical value for earth).  This should probably decrease with decreasing gravity but I ignored that for now (reducing it makes the Yaz fall faster)
A - The wing area.  If you look at the picture in the AD rules for a Yaziran make measurements off that, you get at best a 2 square meter total body area.  I decided to go with 3 square meters and assume that they billow out just a bit more than depicted.
CD - The drag coefficient.  This is a measure of how unaerodynamic the body is.  For the flying squirrels this was between 0.98 and 1.07 so I just took a value of 1 for the Yazirians seeing as they are basically the same body shape.
CL - The lift coefficent - This is how much lift is produced by the wing structures.  The flying squirrels had values between 1.48 and 2.12.  Since the Yazirians have gaps between their bodys and the wings (which the squirrels don't), I strongly suspect that in truth they wouldn't be as effiecent but I was generous and used a value of 2.1

The problem the Yazirians have is that they are too massive.  The mass to wing area ratio of the flying squirrels is about 3.  For Yazirians with a mass of 50 kg and a wing area of 3 m^2, you get a ratio of 16.67.  This means that they are going to fall faster and at a steeper angle and require a lot more speed to sustain gliding.

Due to the mechanics of gliding, you have three forces, gravity, lift and drag.  Gravity pulls you down. Lift acts to propel you forward and lift you up opposing gravity, and drag acts to lift you up, also opposing gravity, and also retards the forward acceleration due to lift.  Now the force from gravity is just gravity times mass and is constant, regardless of what is going on.  The forces from lift and drag, however, are proportional to the square of the velocity and both have functional forms of F=0.5*p*A*C*v^2 where C is either the lift or drag coefficent.  So the faster you go the more lift and drag you have.  Practically, this means at the beginning of a glide, you have almost no lift and drag forces to oppose gravity and a yazirian falls just like a human, i.e. quickly.  It is only after falling a bit that the lift and drag forces actually start to help.

The other sticky question is what speed can a Yazirian safely land at?  The flying squirrels had speed of about 5m/s or about 11 mph.  Military paratroopers are trained to safely land at speeds of 6m/s.

So, if you assume a maximum landing speed of 6 m/s (about 13.5 mph), and you assume that a Yaz doesn't just drop into a glide but "pushes off" with an initial velocity of 3.5 m/s, thus getting a little bit more help from the lift of its wings, a wing area of 3 m^2, and drag and lift coefficents of 1 and 2.1 respectively you get the following table (assuming no change in atmospheric density).

 Gravity 
 Vertical distance 
 Horizontal distance 
 Time 
 1.0 1.44 m 2.00 m
 0.57 s
 0.9 1.60 m
 2.25 m
 0.64 s
 0.8 1.86 m
 2.60 m
 0.74 s
 0.7 2.18 m
 3.06 m
 0.87 s
 0.6 2.61 m
 3.70 m
 1.05 s

Now if you assume some sort of a "flare out" maneuver at the end, that serves to kill some of the horizontal velocity, and thus reduces the total velocity, you can extend this out.  If you assume that a gliding Yazirian has some way to kill half of its forward velocity at landing, you get the following distances before you hit the 6 m/s landing speed.

 Gravity 
 Vertical distance 
 Horizontal distance 
 Time 
 1.02.12 m
2.50 m
0.70 s
 0.92.44 m
2.86 m
0.80 s
 0.82.85 m
3.34 m
0.93 s
 0.73.48 m
4.06 m
1.12 s
 0.64.46 m
5.19 m
1.41 s

However, I don't see any reason a Yaririan can't make a very long sustained glide, especially on the lower gravity planets (although here we may want to look at the effect of decreased atmopheric pressure).  On the higher gravity planets the landing may be painful but I would think definitely survivable.  Here are some numbers:

 Gravity 
 Minium
Vertical distance 
 Horizontal distance
at vertical min. 
 Minimum
Time 
Total
Velocity
"Landing"
Velocity
Glide Ratio
(h to v)
 1.049.85 m
87.28 m
9.64 s
10.93 m/s
6.8 m/s
2.12
 0.949.68 m
87.48 m
10.16 s
10.37 m/s
6.45 m/s
2.12
 0.845.45 m
87.67 m
10.77 s
9.78 m/s
6.08 m/s
2.12
 0.744.09 m
77.16 m
10.21 s
 9.18 m/s
5.73 m/s
2.12
 0.636.52 m
62.54 m
9.07 s
 8.46 m/s
 5.33 m/s
2.12

So, if you assume the "flare out" maneuver at landing, you get the "Landing" velocity in the table.  Given that, and assuming a Yazirian has at least 50m of height, it should be able to glide indefinitely (or at least until its arms get tired).  On a 1.0 or 0.9 g planet I'd require a DEX check or take 1d10 points of damage since they are landing a bit fast (> 6 m/s) but otherwise the gliding is sustainable for long distances.  Also for the long glides it would be 2m horizontal distance traveld for every meter fallen vertically.

Decreasing the atmospheric pressure would do the following:
1) increase the height and time needed to get a sustainable glide
2) increase the terminal velocity and landing speed

Anyway, there's a bunch of food for thought.
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jedion357's picture
jedion357
May 4, 2011 - 5:32am
I wish that I had not dropped out of AP Physics in my seinor year of high school.

Thanks Terl Obar.
I might not be a dralasite, vrusk or yazirian but I do play one in Star Frontiers!