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This is a physics question about an in-game world scenario. In Starcraft II, there is a flying unit called "viper". It has the ability to abduct huge, massive enemy units - while remaining stationary in the air. The question is, if one were to apply very basic physics, how much air would that viper need to move to oppose the force of pulling a massive object?

Original problem description found here: http://www.reddit.com/r/starcraft/comments/277xz5/burrowed_ultralisks_can_be_abducted/chys5wx

The game Starcraft 2

Zerg unit: viper

Zerg unit: ultralisk

Demo: a viper pulling a colossus (while itself remaining stationary in the air)

I can do the basic calculations, but I found the more I thought about it the more intricacies I encountered, until the basic problem looked harder than it is. Now I'm looking for people with a clearer head. Or actually, I really think I know how to solve this (can't get more basic as far as the fundamental calculations are concerned) but would still hear your opinion/strategy, mostly for the "edges" of the problem.

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  • $\begingroup$ tangential question: Suppose you use a vacuum and a hydralisk model (there exists such a thing, right?), how would the scaling work? $\endgroup$
    – mart
    Jun 4, 2014 at 9:53
  • $\begingroup$ Physics: bringing reality to games. :D $\endgroup$
    – Alenanno
    Jun 4, 2014 at 9:58
  • $\begingroup$ You say you've already tried some of the calculations? Can you add those to the question? You might find your question is a bit better received then. $\endgroup$
    – Warrick
    Jun 4, 2014 at 19:20

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This is fairly basic newtonian mechanics. The gravitational force has to equal the aerodynamic forces exerted on the air. Just like a helicopter, really, or even a plane.

So, you basically have a column or air which is accelerated downwards. There are limits on how much you can accelerate that - it can't really go supersonic. But 30 m/s downdrafts are achievable, apparently (IIRC a V22 Osprey does that). That's air coming from a standstill.

So, if I accelerate 1 kg of air to 30 m/s each second, the force is 30 N and I could lift 3 kg. If you want to lift 30 tons, you'd have to move 10 tons of air each second. That's about 8000 m3

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  • $\begingroup$ "This is fairly basic newtonian mechanics." No doubt. What about the acceleration. "Abduct" happens in <1s. A lot more force is required compared to slowly lifting the same object, since F=ma. And then there are the calculations for the wings (2nd part of the question) - no longer simple mechanics and/or formulas... $\endgroup$
    – Mörre
    Jun 4, 2014 at 9:48
  • $\begingroup$ So, how much air do moving wings (of birds, for example) move depending on their wing span / frequency? $\endgroup$
    – kutschkem
    Jun 4, 2014 at 9:57
  • $\begingroup$ @kutschkem: Take that helicopter again. Since you need to move 8000 m3 of air per second, and we assume you accelerate it to 30 m/s, that means you need a minimum area of 8000/30 = 267 m2. This is of course an underestimate as you can't get a clearly delineated column of air moving downwards through stationary air, there's a significant loss due to turbulence. $\endgroup$
    – MSalters
    Jun 4, 2014 at 10:02

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