The Impossibility of Flying Heavy Aircraft Without Training

00:00:00Hg wrote:
On Fri, 03 Mar 2006 11:57:05 -0800, george wrote:

Gravity seems to work to it's own advantage so it's the
ultimate taxing authority in the universe. That really sucks.

Air resistance is fricticious

I thought resistance was useless.

At least for Dent and Ford.

I've never sistanced even once

I asked first.

Ok, vertical momentum of a wing in level flight is zero.

Jose
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The hovering spacecraft has zero horizontal and vertical momentum.
It has weight, directed downwards. The engine accelerates
mass downward producing an upward force equal in magnitude
and opposite in direction to the weight of the spacecraft. This
imparts an acceleration to the spacecraft equal in magnitude and
opposite in direction from the local acceleration due to gravity.

The flying wing has some horizontal momentum which is secondary here,
and zero vertical momentum.
It also has weight, directed downwards. The wing accelerates
mass downward (mass it finds in the air molecules) producing
an upward force equal in magnitude and opposite in direction to
the weight of the wing (and its presumably attached aircraft. It does
so by finding air in front of it, flinging it downwards and forwards
(which causes the air in front to try to get out of the way by rising).
In the steady state, one can measure high pressure below and low
pressure above, but this is just the macroscopic manifestation of the
greater number of molecular collisions below, and the lesser number of
collisions above. That's what pressure is - we have both agreed on this.

The greater number of collisions below
imparts an acceleration to the aircraft equal in magnitude and
opposite in direction from the local acceleration due to gravity.

Unlike the spacecraft (at least to first order), the wing is actually
supported by the earth, as the pressure below the wing is higher than it
would have been absent the wing's passage, and this higher pressure
(spread out over many square miles) pushes down on the earth with a
force equal to the weight of the aircraft.

Jose
--
Money: what you need when you run out of brains.
for Email, make the obvious change in the address.

Air resistance is fricticious

Resistance is futile.

Jose
--
Money: what you need when you run out of brains.
for Email, make the obvious change in the address.

On Fri, 03 Mar 2006 19:05:18 -0500, Morgans wrote:


"00:00:00Hg" wrote

I thought resistance was useless.

Nah, it's "resistance is fruitile."
g

I think I'll have an apple and see if
eating it will reveal the secrets of
gravity as I gaze at the Moon.

"00:00:00Hg" wrote

I thought resistance was useless.

Nah, it's "resistance is fruitile."
g
--
Jim in NC

"00:00:00Hg" wrote

I think I'll have an apple and see if
eating it will reveal the secrets of
gravity as I gaze at the Moon.

Yeah, but can you tell me the horizontal and vertical components of it's
momentum?

I was thinking apple, but I need two; I'll have a pear, instead. g
--
Jim in NC

On Fri, 03 Mar 2006 21:06:30 -0500, Morgans wrote:

I think I'll have an apple and see if
eating it will reveal the secrets of
gravity as I gaze at the Moon.

Yeah, but can you tell me the horizontal and vertical components of it's
momentum?

Not any more, I'll have to pick another.

Not the Moon... it has no stem.

You are looking here at the basic question of how does the
starting vortex form.

No, I'm also looking at how it is maintained.

You have staked out the position
that a ground is required for the vortex to form.

No, I've staked out a position that the ground is required for there to
be no net momentum change. The ground is ultimately what the air (given
downward momentum) bounces against, either for real or by proxy.
Granted this is not what provides lift, but it does provide the ultimate
support when the wheels themselves leave the ground.

Do we agree or disagree that the "wave" i.e.
starting vortex, however it got started can continue in the
absence of the ground?

We agree. I do not see however how it can continue in the absence of
energy, and I still maintain that in order to cancel out mv^2/2 of the
wing (which otherwise would be falling), there has to be (locally) an
equal mv^2/2 which the air acquires, and spreads out over the surface of
the earth (where it bounces off, keeping the earth away). Like a
dribbler who supports himself by dribbling, there is lots of momentum
transfer (to the ball, back and forth), which, while it nets to zero,
only does so because of the earth. IF there were no earth, the ball
would never bounce back.

That is not the same as what you seem to think I am maintaining:

that without a ground an infinite
wing would require a constant input of infinite energy to
accelerate the air and give it momentum (and kinetic energy)
for the uncanceled downwash.

Jose
--
Money: what you need when you run out of brains.
for Email, make the obvious change in the address.

An object moving through air doesn't cause any significant compression
(change in volume) of the air until its speed gets close to the speed of
sound.

Is there not a (slight) pressure increase in front of any object,
especially a blunt one, moving through the air? (if not, what causes
the air to get out of the way, and what causes the breezes as it goes past?)

Jose
--
Money: what you need when you run out of brains.
for Email, make the obvious change in the address.