Re: flight dynamics of Model Year 2100 Audi (slim Audi content)

["Fred Munro" <munrof@isys.ca>]

Harking back to the beginnings of this thread, we now know, thanks to Mike's
detailed description of space-flight physics, why Lucas shows his space-born
fighters banking and turning like aircraft. Imagine how boring a realistic
representation of a space dogfight would be. You get one pass and wait a few
hours (or days depending on initial speed) to slow down, stop, and come
back. Either that or all parties stop and pound each other until one side
blows up. Success depends on initial strategy and technology, not the
inherent hand/eye co-ordination of the hero(ine). Hardly the stuff of great
theatre!

Fred Munro

----- Original Message -----
From: Mike Arman <armanmik@n-jcenter.com>
To: <quattro@audifans.com>
Sent: Friday, September 03, 1999 8:33 AM
Subject: flight dynamics of Model Year 2100 Audi (slim Audi content)


>
> The comment about no noise in space generated a startling amount of
> speculative e-mail, so I figured I'd summarize the flight characteristics
> of the model year 2100 Audi S-500 interstellar runabout.
>
> For the sake of simplicity, we will assume a vehicle with a front, a back,
> a top, and a bottom (none of which are really necessary in space) moving
> "north", which I have chosen as an arbitrary direction.
>
> It is desired to turn "east", or change the direction by 90 degrees, and
> maintain the same velocity as we already had.
>
> Even though there is no air in space (hence no noise), the vehicle and its
> contents still have inertia. We have to roll the vehicle along its
> longitudinal axis so that when we change direction, the inertial forces
act
> "downward" in the vehicle. Otherwise, anything and anyone not fastened in
> place will slide across the floor as the vehicle changes direction.
> Therefore, the first part of the maneuver is to roll the vehicle so the
> roof faces the new direction, and then pull the nose "up".
>
> (Fighter pilots do this now: They call it "bank and yank", but this only
> works in AIR-planes. There's no air in space, remember?)
>
> Unfortunately, we are not done. The vehicle continues to travel "north" at
> the same speed as it was previously, but now it is in a "belly first"
> attitude instead of a "nose first" attitude.
>
> We need to cancel out all our "northward" velocity - if we originally ran
> the engines for two hours to get to 100,000 mph (for instance), we would
> need to reverse them for two hours to get back to 0 mph. Simply running
the
> engines for two more hours with the spaceship pointed in the new direction
> we want to go ("east") would result in us moving northeast instead of
east,
> since we are still moving 100,000 mph to the north, and now are also
moving
> 100,000 mph to the east. The result is a 45 degree change from our
original
> course, not a 90 degree change. Two more hours would result in us now
> moving east at 200,000 mph, but we are STILL moving north at 100,000 mph,
> so our path is NNE (60 degree change). We MUST cancel all velocity in the
> old direction, or we will continue to go that way, no matter where the
> "nose" is pointed.
>
> (Comparison: A ball rolling on a frictionless pool table. It rolls "north"
> at two inches per second. If we apply a thrust pushing it to the "east" at
> two inches per second, the new direction is "northeast", at 2.83 inches
per
> second. Draw a diagram - In one second, the ball travels two inches north,
> and also two inches east, and thus traverses the hypotenuse of the
> triangle, which is 2.83 inches long. A squared plus b squared equals c
> squared.)
>
> This means burning a LOT of fuel, or it means carefully planning where we
> want to go before we hit the "launch" button, and sticking to that. In
> solar systems, it is possible to "slingshot" around moons or planets (or
> even a sun, but you better get that EXACTLY right) to change direction,
but
> in deep space, changes in direction or velocity can only be accomplished
> with fuel.
>
> And that's why the new 2100 Audi s-500 has a hundred thousand gallon fuel
> tank! And with 100,000 gallons of fuel, you better believe you'll need
> cupholders - you'll be out there for a LONG time.
>
> Best Regards,
>
> Mike Arman
>
>
>
>
>