Anyone familiar with this 'claim' at Aulis.com?

[JayUtah]

D'oh! Why didn't wind occur to me?

Because you're a scientist, not an engineer.

[ka9q]

The report also says the winds at launch were 3.3 m/s from the south at the 18.3 m level. (The tower was on the north side of the vehicle.)

Best explanation I can see for the direction of the vapor trails.

And it certainly explains the need for the yaw maneuver. The Saturn V took about 10 seconds to clear the tower, and I think it was a lot closer to it than 33 meters.

[Donnie B.]

The report also says the winds at launch were 3.3 m/s from the south at the 18.3 m level. (The tower was on the north side of the vehicle.)

Best explanation I can see for the direction of the vapor trails.

And it certainly explains the need for the yaw maneuver. The Saturn V took about 10 seconds to clear the tower, and I think it was a lot closer to it than 33 meters.

Well, the stack wouldn't have immediately begun moving north at that speed as soon as the holddowns released.  That was a lot of mass to accelerate!

It was not, as it were, a leaf on the wind.

[smartcooky]

Thank you all for the replies.

I never knew about the yaw movement to take the stack away from the tower, though it does make sense; the stack is awfully close to that tower.

Nothing about it in the lunch part of the Apollo 11 journal

[Echnaton]

That was interesting. I'd noticed the yaw in launch videos but was always unsure if it was real or an illusion of the video.

[Noldi400]

Another frequent astronaut simile is a runaway freight train going down an old, poorly maintained track.

That's a simile I like better.  No need to bring the "woman driver" stereotype into things!

Substitute "nervous driver", then. Hey, I don't make 'em up, I just quote 'em. Actually, I thought that particular stereotype was dead and buried - I think Danica pretty firmly hammered the last nail in the coffin Sunday.

Speaking of Aulis claims, I was poking around some of their links the other day (entertainment is where you find it, I guess) and found some documents from 2010 written by a Greg Alexander in which he questions the validity of the law of Conservation of Energy and the formula for kinetic energy, among other things.

What caught my attention was that he used an example for kinetic energy that sounded awfully familiar:

"Consider two identical space rockets in the vacuum of space well away from the effects of any gravitational field. Both, in parallel, burn their engines at full power on two separate occasions of exactly equal duration. However the second rocket, immediately after its first burn does an about turn such that its engine is pointing in exactly the opposite direction just in time for the second burn. In such a situation it is obvious that the first rocket will continue accelerating with the second burn while the first will start to decelerate, losing the velocity it had gained from the first burn. It is also apparent that by the end of the second burn the second rocket will have lost all the velocity it had gained from the first burn while the first rocket will have exactly doubled the velocity it had gained after the first burn.

... Each rocket can be considered as a closed system and both have had the same amount of energy supplied to it by its engine.... Even though the first had all its power from its engine transformed directly into kinetic energy, the second rocket is now stationary compared with the first, relatively speaking, and has zero kinetic energy...  It would appear that as the two burns were directed precisely counter to one another, the kinetic energy from both has exactly cancelled out. Such a destruction of energy is completely counter to the laws of conservation."

I wonder if this is where our maritime engineer friend got his ideas or if it's just a parallel case of someone else who didn't pay attention in high school physics and thinks you can just toss mass/energy out of a closed system and pretend it just disappeared.

Oh, if anyone wants a chuckle, this is the link:
http://www.webspawner.com/users/gjalex

[cjameshuff]

Another stunning consequence is found in the world of astronomy in that meteorites no longer explode on impact.

Why stop there? More stunning conclusions...bullets don't hurt. Cars bounce harmlessly off trees and other cars. Etc...

[grmcdorman]

"Consider [snip]... Both, in parallel, burn their engines at full power on two separate occasions of exactly equal duration. [snip]... However the second rocket, immediately after its first burn does an about turn such that its engine is pointing in exactly the opposite direction just in time for the second burn.  [snip]... by the end of the second burn the second rocket will have lost all the velocity it had gained from the first burn while the first rocket will have exactly doubled the velocity it had gained after the first burn.

Except that the first wouldn't be at a standstill, and the second wouldn't be at exactly 2x velocity, either, would they? (Tsiolkovsky's equation - unless you have, um, magic).

[gillianren]

Substitute "nervous driver", then. Hey, I don't make 'em up, I just quote 'em. Actually, I thought that particular stereotype was dead and buried - I think Danica pretty firmly hammered the last nail in the coffin Sunday.

Oh, sure.  It's just one of the interesting side notes of studying the Space Race.  There's an awful lot of casual sexism thrown about, and you can always assume that the people making decisions are men and seldom be contradicted.  And, no, I know a lot of people who still believe that.  Many of them are men who are themselves terrible drivers.

[ka9q]

Well, the stack wouldn't have immediately begun moving north at that speed as soon as the holddowns released.  That was a lot of mass to accelerate!

Yeah, I guess you're right. I estimate the cross sectional area of the three stages of the Saturn V (excluding the LM adapter, CSM and LES) as almost exactly 800 m². I can't find its drag coefficient, but assuming it's 1.0, the force from a 3.3 m/s wind at sea level (1.2 kg/m³) would be 5227 N. That will accelerate 2800 tonnes at a rate of 1.9 mm/sec²...

[Donnie B.]

Well, the stack wouldn't have immediately begun moving north at that speed as soon as the holddowns released.  That was a lot of mass to accelerate!

Yeah, I guess you're right. I estimate the cross sectional area of the three stages of the Saturn V (excluding the LM adapter, CSM and LES) as almost exactly 800 m². I can't find its drag coefficient, but assuming it's 1.0, the force from a 3.3 m/s wind at sea level (1.2 kg/m³) would be 5227 N. That will accelerate 2800 tonnes at a rate of 1.9 mm/sec²...

I don't suppose there are any ka9q correction T-shirts available... 

[Not Myself]

Except that the first wouldn't be at a standstill, and the second wouldn't be at exactly 2x velocity, either, would they? (Tsiolkovsky's equation - unless you have, um, magic).

No, but you can fix that one - just have the one that turns around fire until it stops, and the other one fire in the same direction for the same time as the other rocket.

The big issue is that it ignores the kinetic energy of all that hot glowing stuff shooting out the nozzle.  The stuff that makes the rocket go in the first place.

[Noldi400]

"Consider [snip]... Both, in parallel, burn their engines at full power on two separate occasions of exactly equal duration. [snip]... However the second rocket, immediately after its first burn does an about turn such that its engine is pointing in exactly the opposite direction just in time for the second burn.  [snip]... by the end of the second burn the second rocket will have lost all the velocity it had gained from the first burn while the first rocket will have exactly doubled the velocity it had gained after the first burn.

Except that the first wouldn't be at a standstill, and the second wouldn't be at exactly 2x velocity, either, would they? (Tsiolkovsky's equation - unless you have, um, magic).

True, but the point is still valid - after doing two burns each, identical except for vector, the two spacecraft would have very different velocities relative to their starting point.  He's made the exact mistake as Heiwa; he's ignoring the kinetic energy of the particles of ejected propellant, which is still part of the "closed system" he started with, even though physically separated from the spacecraft.

[Sus_pilot]

Thank you all for the replies.

I never knew about the yaw movement to take the stack away from the tower, though it does make sense; the stack is awfully close to that tower.

Nothing about it in the lunch part of the Apollo 11 journal

Here's a quote from W. David Woods' How Apollo Flew To The Moon that you might like:

As 3,000 tonnes of metal and volatile propellant rose past the umbilical tower, it could be seen to lean disconcertingly away as though it were about to go out of control. This was an entirely planned yaw rotation designed to manoeuvre the rocket away from the launch tower as a precaution in case a swing arm were to fail to retract or a gust of wind were to push the vehicle back towards the unyielding tower.

[JayUtah]

1.0 is a reasonable estimate for a smooth cylinder, except at some very high Reynolds numbers where it's much lower.  It certainly won't get much higher than 1.0.  The Saturn V is not especially smooth, since the stringers are arranged transverse to ideal wind flow, but this shouldn't increase the overall drag much since it affects only skin drag.