I'm afraid you'll have to scold your physics teacher. In order for you to go upward, you need a force vector in the upward direction that is greater than the force vector caused by gravity (downward). A glider only generates lift (the upward vector) when it is falling through the air. The lift of a glider is never (ever) greater than the force of gravity. When you tilt a glider upward, its surfaces stop being at the proper angle to generate lift, so you actually lose lift.

To illustrate: I performed the experiment I suggested earlier in this thread.

Conclusion: pointing a glider upwards will not help land it. If it did, you would see it in real glider landings.

By the Bernoulli principle, the specific job of the wings is to convert forward force into upwards force. By shifting the airfoil, you shift the details of that conversion. I don't know any part of that equation, which is just built on having less air pressure below than above, which requires active acceleration, rather than just velocity, to work.

The paper airplane experiment doesn't compare because you're always looking at a craft with the desired wing shape during acceleration. The question is, how does changing wing shape during unpowered flight alter your ability to gain lift or bleed speed. Since aircraft are capable of landing unpowered (usually under emergency landing conditions), I fail to see how one can argue that you can do it with a plane, but not with a glider. The glider probably needs modifications from the prototype on the show, but that isn't really a showstopper.

Well, you're actually both sort of wrong.

The squirrel suit doesn't generate lift in the same way as a plane does via having the top and bottom of the wing shaped differently (Which only requires velocity, not acceleration).

You can actually go up in a glider for brief moments, but it requires you to fall more than you went up (Go into a nose dive and pull up, you'll end up higher than your lowest point, but below where you started the dive), but you can generate lift (upward force) in a glider/squirrel suit by tilting so that the wings are pointing up. It'll slow you down (falling), and cost you alot of forward momentum, and is actually how planes and gliders land.

I'm no physicist, but I'm a big fan of science. Bernoulli's principle only takes the acceleration due to gravity into account, and then only as potential energy for intrafluid dynamics, not pressure effects. The lift formula doesn't have acceleration at all. See Bernoulli's Principle and lift.


The problem is that you can increase drag, sure, but in a glider, increased drag means lower airspeed means decreased lift, and now you're plummeting again. The best you can do is decrease your glide ratio, which decreases your forward velocity but increases your downward velocity.

As for climbing, gliders don't accelerate without a downward component vector. If we could change a glider's wing to generate a stronger lift than gravity, we'd be able to fly anywhere in the world without power. As cool as that might be, it would be adding energy into a system, not transferring it, and so violate the laws of thermodynamics (first and second, I think).

Gliders can fly upward, but only with thrust supplied by an outside source (there is a different name for gliders with internal sources of thrust) or by generating enough airspeed, usually by shedding altitude for speed (with no net gain -- pesky laws of thermodynamics again). I found an example of a glider that takes off with a winch launch, climbing with the thrust provided by the pull of the winch. However, after the winch releases (you can see it in the video), the pilot keeps trying to climb and ... well, you can see it in the vid.

I believe you'll find that these two articles by a manufacturer of wingsuits disagree with this assertion. As a bonus, the first article discusses landing a wingsuit without a parachute.

Of course squirrel suit generates lift like a plane, by having lower pressure on top than below. This is caused by the different shape that causes air to flow faster on top than below.

What other mechanism could be responsible?



Are you sure about that? Since lift is generated by air going over the wing, by tilting upwards, you would lose lift. When you flare a parachute, you lose lift, but reduce forward speed. Do it too early, and you land hard. I think that's the same with gliders, when you're at very low altitude, your concern is to brake. Planes have flaps that increases lift at low speeds, so they can land slower without stalling - they don't have the luxury of flexible human legs that can absorb impact.

Since we're talking about wingsuits having no inherent thrust capacity, I thought this would be appropriate:

http://www.youtube.com/watch?v=eS2rjcVcaqQ





-karma

Hmm, weird, the design didn't really look like it would act like a foil, so I figured it relied on simple increased air resistance to decrease terminal velocity.

Yeah, but it is going to be a temporary thing. If you want, make a paper airplane and make some flaps on it. Throw it and see if it doesn't do a loop that sends it flying upwards for a bit. That would be the same as if you went into a dive and then pulled up. If you throw well it can even do multiple loops which will further prove that a gliding object can go up, if only for short periods of time.

I don't know how good the suits are, but I'd imagine that if you were skilled (and suicidal) you could glide till you are close to your target, then dive and pull up near the ground to create as much lift as possible. If you can go up then the fall would only be the same as whatever high you stalled out from (Maybe a bit less thanks to extra air resistance), and if you just reduce your falling speed, then you'll be hitting the ground alot softer. It would require a great deal of skill and nerve though, as you'd likely have to dive bomb to within a few dozen meters of the ground before pulling up to make it work properly, and if you wait too long then you face plant into the ground at max speed.

And that's the point - if our suit is gliding, it's because it's already done the fall part to get up speed. Now you still have the option of tilting upwards again. You can't get back to your starting point, but that was never the goal.




I think you're agreeing with me here, yes?



You get lift as a function of airspeed, but also as a function of the curvature of the wing (a flatter wing generates less lift than a curved one, for instance). Altering the curvature does sacrifice speed, but it should increase lift from curvature more than it loses lift from speed loss - as long as you don't hit stall speed. Once you hit stall speed, you fail to generate lift at all, obviously.

[quote]
As for climbing, gliders don't accelerate without a downward component vector. If we could change a glider's wing to generate a stronger lift than gravity, we'd be able to fly

Double post.

Post frenzy!

TP for the win
Yeah, never said you could get back to your original point, just that you could temporarily generate enough lift to go upwards, but it will never get you higher than your starting point.


But we can generate a stronger lift than gravity, we just can't sustain it for more than a few moments. Like I said, go make a paper airplane with flaps and throw it hard. It'll do loops. It'll even go above where you originally threw it from, but that is because you start it at a higher velocity than it can obtain just gliding (Without dive bombing).

Got to read what I'm writing carefully. I'm not saying a glider can fly, simply that it can, for a short time, generate enough lift to go upwards, and it is easily provable if you have a piece of paper and several feet in which to throw a paper airplane (And, I guess, working arms).

When you're talking about a wingsuit, you're talking about something that is incapable of level flight, much less actually climbing. The best wingsuit in the world has a glide ratio of 2.5 or maybe 3. Hang gliders are more like 18 or 19, and they can't climb steeply and loop by stalling.


I don't think so. You seemed to be saying that lift was generated by acceleration. I'm saying it's velocity [edit: more accurately airspeed]. They're two different things.


That's why I provided links to documents talking about the high stall speed of wingsuits. You did read them, right? In case you didn't, I'll summarize: wingsuits have a minimum air speed that varies according to the body it's wrapped around, but according to the calculations provided in those articles the average stall speed is probably around 57.7 mph (92.8 kph, 25.8 m/s). More for an ork, less for an elf.

Okay, but that's a limitation of the technology as it stands. We have 50 years to improve it, thanks to smart materials and yes, short-burn rockets and such. I find the argument that the suit now can't land safely, and therefore in 2050 it can't land safely dubious (and that was my original point). But regardless, our goal still isn't technically to go up - it's to hit a given target at a speed slow enough to land. Aiming up is a good way to bleed off airspeed because it increases forward drag, while slowing your actual descent. The question is simply, can we make a suit that can use this method in order to land safely (using 2050 technology).



I think you must be responding to someone else there. I never said that - in fact, I was arguing specifically against it, saying unpowered craft can go up.



But that's okay, if we're only stalling for a few moments. Let's say we're coming in at 60 mph. We pull up and create enough drag to decelerate say 20 mph/s (which is fast, but not deadly fast). We start dropping, but the standard rate of 9.8 m/s^2 doesn't apply, because we still have the airfoil decreasing our rate of descent. Any physicist should be able to calculate the point at which our forward motion + descent is at its lowest point, and aim to put down then.

Combine that with a targeting computer to do the calculations for you, smart materials that let out fabric as necessary or turn rigid or soft or into particular shapes, secondary chutes and short-burn rockets and the idea of landing on a small, pre-selected point seem quite achievable.

Sure, there's an advance in technology, but we'll be using the same physics. Aiming up doesn't bleed off airspeed in a wingsuit, because it ain't got enough wing. It's also not a way to generate lift, since the airfoils are pointed the wrong direction. The best you can get is a wing load situation, like a parachute only not as good. It's in the documents I linked, but I'm done summarizing links; read it or argue from ignorance.


Again, it's about wingload. There's only so much you can do with the wing you have. To do what you propose, you need more wing. Maybe that means a complicated system of braces and expanding fabric, but then you have a hang glider (a la the Shadowrun video game), not a wing suit. There's another way of getting the right wing load that would be far cheaper, easier, more reliable, and less prone to failure or hacking: a parachute.

Air resistance? Seriously? It only looks to about double your surface area.



You can't really compare a wingsuit to a paper airplane. A wingsuit has over 10lbs per sq feet of wingload. A paper airplane has what, 1/10 sq foot surface area? So if you put a 1 lbs weight on that paper plane (use some of that weight to reinforce the wings), then you have a proper balance between lift, air resistance and gravity. Then try your flaps experiment.

By the way, no one said that a gliding object can't ever go up. It can dive to build speed enough to have sufficient lift to momentarily go upwards. Wingsuits can't generate enough lift to do that though.

Ok, I'm going to take this personally for a moment.

See, but now you're changing arguments (or at least not presenting the same argument Smokeskin did earlier). When I brought up the idea, people were complaining that no, gliding objects can't go up, you can only do that with powered thrust.

Now, if you argument is that the wingsuit specifically can't do this because the surface area of the wings is too small to generate significant lift OR breaking power, then just state that plainly.

I got the same impression as you Nezumi. Sudden shift from 'impossible to generate enough lift to go up' to 'can't do it with a squirrel suit specifically'

I'll bite. Sure, I was wrong about gliders climbing in all instances. I failed to account for aerobatic flight in my arguments. However, I think we all agree that while aerobatic flight is climbing instantaneously, a glider doesn't get to keep the altitude for very long without an updraft. Doing a wingover by diving doesn't help land a glider unless you can dip underground when you do it. Has there been a suggestion that aerobatic-type flight should be considered for landing procedures?

My failure to be comprehensive about an aircraft we were not actually discussing doesn't negate all of my points, though, and certainly not about wingsuits. None of these point have been addressed or refuted (or even mentioned when the poking started in #67).

And I've never insulted nezumi's knowledge of physics. I may have insinuated that his or her physics teacher needs some scolding, but unless I am mistaken, his or her description of Bernoulli's principle and airfoil mechanics were mistaken, and have not been refuted on that point. I've engaged nezumi's arguments, not him or her personally, offering substantive sources from knowledgeable third parties. I did suggest that he or she may be arguing from ignorance (which may have crossed the line and if so I apologize), but his or her arguments were refuted directly by the material I linked prior to his or her post.

I've refrained from listing the individual fallacies in the arguments of other posters, and I see no reason why I should start. I certainly try to refrain from piling on.

I think that sorts things. Any other issues that we should have taken to private messages, or shall we continue talking about wingsuits?

Yeah, aerobatic-type flight is exactly what I was suggesting, and even detailed doing a dive bomb to within a few dozen meters of the ground, then pulling up, almost skimming the ground before getting enough lift to go up several meters, killing all forward momentum in doing so, and then falling back down the however many meters of height you got. Not something doable today, because even a 2-3 meter fall can be dangerous, and you couldn't skim that close safely, but with good hydraulic system and some specialized software to tell you when to pull up, you could maybe get it to to where you are only falling about 10m or so, which is within the ability of the hydraulics to absorb.

What I don't know is if wing/squirrel suits can actually manage a maneuver like this or not, but I do know that a glider and even (edit: paper) airplanes can.

And I stated in almost every one of my posts that the height gained followed the laws of physics (indirectly), as it couldn't bring you higher than the highest point you started at, but simply higher than the lowest point of your dive.

So yeah, I was just noting that I too saw a sudden shift of 'cannot happen' to 'cannot happen with a wing suit', the latter of which may be valid. I really don't know enough about the physics involved to say for sure. I would however imagine that such a maneuver could at least bring you to a near stop as far as falling is concerned while bleeding off all your forward speed, thus allowing you to land safely with hydraulic systems and nerves of steel at getting so close to the ground in a dive bomb.

So, no comment about the link I posted?

I would hazard a guess that strapping jet turbines to your legs might alter the flight characteristics of a wingsuit.



The flight shown in the video is about 30 seconds of level flight. Later iterations of the system have allowed up to two minutes of sustained level flight.

Could one use the additional thrust to create enough of a stall force to make a difference in landing without the parachute?



-karma

but then how do you catch Successful Farming Machinery show? http://www.rfdtv.com/shows/SuccessfulFarmingMach.asp

I am Smokeskin...

I never said that nothing without trust couldn't go upwards. In the earlier post I said that



That's pretty specific.

You then said that pointing upwards made you go upwards, which you claimed was very basic physics, but is frankly nonsense so I responded:



I have a very hard time seeing how the bolded part with "you" could be anything but wingsuit - obviously there are lots of things that can generate lift larger than gravity. Airplanes for example (they generally don't move upwards by pointing thrust down, but by going fast enough to generate sufficient lif).

I explained precisely how the physics of lift work. I don't understand how you can think that is an insult to your knowledge of physics.

I also didn't understand what you meant about changing facing changing your direction of movement, and asked you to explain it.

I feel like I've made this mess, so perhaps I can help straighten some of it out

Smokeskin - most of my last post was in response to Aaron (except for the bit under the edit tag - which I included only in specific response to your comment). Yes, realizing now that the bit about gliders is a completely different discussion, and one that I started because at least I understand how gliders work (but not so much parachutes), your comments make more sense and I understand your point. It might be possible with a wing-suit - if the wingsuit had enough lift area to actually overcome its descent. So that was the source of my confusion there; I was entertaining two separate lines of discussion about two separate devices simultaneously.

Aaron - I do apologize. I did take your physics comment a little personally, because you seem to know what you're talking about, and I came away feeling like if I don't even understand how lift works well, boy am I dumb. So definitely a level of confusion and frustration and a lot of misreading on my part.

So there's my public apology for losing my patience and embarassing myself in public. *sigh*

I'll edit out the reference to posts, since that was specifically aimed at Smokeskin's comment, and I think that's been answered, and edit out the accidental triple post I just noticed.


On the topic at hand - alright, a wingsuit has insufficient wing area to generate lift greater than the fall of gravity. Still, this suit seems awfully convenient - it has a tiny foot print (both when deployed and when in use, physically and on sensors), looks to offer excellent mobility, and requires no heavy fuel or magic to use. So it definitely seems like it can be useful, but that use is limited by it requiring a long landing pad to stop on.

How else might you make landing possible? Perhaps permitting a body-hugging parachute attached at the hands and feet that turns you sort of into a squirrel biplane (or triplane)? A standard parachute? A tail hook? This feels like it should be an almost trivial question to answer, so I'm wondering what I'm missing.

Nezumi, that's a great response. All too often stuff like this ends up in fruitless "but you said" arguments. Bravo for shortcircuiting that and getting the thread back on track.



A standard parachute obviously works. Extending the suit with struts or something just ends up in a paraglider, so that's a bit boring.

Magic? Levitate?

Hydraulic jacks can easily handle the vertical velocity, so we need a way to handle the 60+mph of forward velocity. Inline skates? You still need a fairly long stretch to brake on.

What, uh, is gonna happen to the surface you're landing on if you hit it at the speed that you require the hydraulic jacks?

If I were to write actual, official Shadowrun rules for a wingsuit, I would give it a bit more performance than modern wingsuits (not too much, though; physics is still king). I'd also include a standard parachute (the ram-air parafoil kind in Arsenal) in a special, low-profile pack. I'd also have an optional jet pack to allow for horizontal flight for a certain amount of time.

I might also include a spell or two that could be used to help land a wingsuit without a parachute, although I'm not sure any new ones are needed, as Levitate would work just fine. Of course, that's using magic, so there you go.

If you can install something on the ground, a net would work nicely, I think.

Nothing more than if you dropped from 1m or so. The hydraulic jacks work by slowing the decent right at the last moment (Kind of like catching an egg from a good height), so you don't experience more deceleration than you can handle. This also means that the ground doesn't really experience much more force than a short fall.

At least, I'm fairly sure that is how it would work out, been a while since I've done physics and don't feel like working it all out on paper.

Not alot of point in using the suit if you can just levitate in anyway.

Of course that rather defeats the purpose of being able to stealth glide into a place if you have to sneak in and set up a net first

Physics is not my strong point. I thought hydraulic jacks bled off the kinetic energy of the impact so you didn't break a mass of bones by hitting the ground at 30 mph, but it's gotta go somewhere, right?

But it does so 'gradually'. So instead of applying all your force to the ground over a period of 4 milliseconds, you do so over (lets say) 40 miliseconds, which means you and the thing you are landing on suffer 1/10th as much harm. This is why hard objects hurt more when they hit you. They transfer all their energy to you in just a couple miliseconds, while the soft thing does it over several miliseconds (They also tend to be lighter).

Not if you want to come in at about 100 meters per Combat Turn. Unless you're accustomed to getting ten hits on a Force 10 Levitate spell, of course.

The way hydraulic jacks work (in armor or cyberlegs) is that they reduce the effective height of a fall. It does so by taking off (rating x 2) meters from the fall. Unfortunately, given the acceleration of falling, this is taken off the end of the fall, rather than the beginning, and so the farther you fall, the more effective the jacks are (weird, but it's a role-playing game, so we run with it).

Doing some math and physics things, and trusting in the manufacturer's articles and assuming a stall speed of 57.7 mph, I get the impact with the ground being about 27.2 m/s, the equivalent of a fall of about 38 meters. Subtract 12 for Rating 6 hydraulic jacks, and you get to soak 26P, half Impact armor.

I begin to think that hydraulic jacks are ... insufficient.

Is there any other way to cast levitate?

And yeah, hydraulics are insufficient from a freefall, which is why I suggested the acrobatics, so that you come to a dead stop at maybe something like 15m or so, then start the fall again from that height.

Toss in a spirit's movement power. But really, yes, magic makes this less than ideal. It requires an expensive mage to sustain at least one spell on you, and it lights you up on the astral the whole way.

Would a tail hook on a dynamic line work?

But that stall speed is the forward velocity, not the vertical one. The jacks handle the vertical one. Unless you were looking into braking on the side of a concrete building .

Okay, it's completely crazy, but I'd allow a player to attempt it. Bring a grapple gun, nail something tall-ish as you go by, and swing around until you're at a sane speed. Then you can lower yourself down.

Of course, you can't really aim because your arm is attached to a wing, so maybe not.

External gun mounts!

Or, how about simply having a smartlinked grapple gun attached to your chest or belt? You don't really need to aim, just go by at the right distance and altitude (maneuver) and fire at the right time (mental command).

Moving at 30 m/s and doing it with a 20 meter cable, you're looking at a centripetal force of F = m * v^2 / r = 45 N on a 1kg weight, or 4.5g. That's tolerable, both in terms of physiology and cable strength.

You're still going to be dropping at 10 m/s, so you can't swing around forever, can you?

Someone mentioned a dynamic rope - how about doing it with one of those and going for not swinging around, but when it has braked you and is just about to pull you back, the cable is cut - you're at 0 forward velocity, and the hydraulic jacks handle the fall.

I was imagining more like letting out your grapple line, which is attached to a harness and comes off your back perhaps, let it hit the side of the building and drag up to catch the steel wires or siding they oftentimes put up (for things like keeping people from jumping off, aluminum flashing, grounding the lightning rods, aerial antennas and so on). Yes, half of those would generally snap off with the force, so it would require some pre-planning, but just giving examples. Shooting it could work, I'm just worried it's chancier than dragging it.

The best part is you get the one PC who doesn't understand physics, hits an antenna, and swings around it, reducing the radius of the rope as he goes and thereby increasing his rotational speed, whipping around and around and around.

Sorry for missing this one before.

I didn't calculate forward velocity, I calculated the total velocity vector that a character would experience when landing, including both the forward and downward vectors. This is because a person is very inelastic until the bones hit, and by that time, the damage is done.