Why does the shuttle throttle on ascent?

On Tue, 9 Jan 2007 08:44:27 -0600, Jeff Findley wrote
(in article ):

and like almost all of my (poorly built) models from that era, it was likely
destroyed by fire crackers.

We loaded pellets into our Crossman airguns, but the principle was the
same. :-)

--
Herb Schaltegger
"You can run on for a long time . . . sooner or later, God'll cut you
down." - Johnny Cash
http://www.angryherb.net

Jeff Findley wrote:
I didn't have a transparent UH-1, but the one I did their regular UH-1 model
(at least I think it was a Monogram). I modified so that it would spin the
top rotor via an electric motor and a couple of LEGO gears. Luckily on this
model the fuselage cover easily slid on and off, so everything was hidden.
Boy that thing would spin that main rotor *fast*. ;-)

Yes, they also did a non-transparent version, minus some of the inner
framework parts.
Unfortunately, my painting skills weren't that great at the time, so the
overall appearance was rather shabby and like almost all of my (poorly
built) models from that era, it was likely destroyed by fire crackers.

I've seen some pretty shabby looking real ones over the years.
Monogram also did a 1/48 scale Huey and Huey Cobra.
Revell did a 1/32 scale Huey ( in fact they did at least two versions of
it) in 1/32 scale, and also did a 1/32 scale Cobra.
These all were around at the time of the Vietnam War, so Hueys were well
known.
Want to see my favorite Vietnam-era weapon?
The farm tractor company, Allis-Chalmers, goes to war in a big way in a
tiny tank:
http://en.wikipedia.org/wiki/Ontos_tank

Pat

Jeff

Jeff Findley wrote:
"Pat Flannery" wrote in message
...

The really amazing model was the transparent Monogram 1/24th scale Bell
UH-1 "Huey" helicopter.
It took forever to spin up to full speed, but God help you if that main
rotor ever hit you at full RPM. :-D

Iirc, this was the 'copter with what my Dad called the "Jesus Nut", that
one nut that allegedly held the whole craft together and, when hit by
enemy fire, gave all aboard just enough time to yell "Oh, JESUS!".



--

..

"Though I could not caution all, I yet may warn a few:
Don't lend your hand to raise no flag atop no ship of fools!"

--grateful dead.
__________________________________________________ _____________
Mike Flugennock, flugennock at sinkers dot org
"Mikey'zine": dubya dubya dubya dot sinkers dot org

"Dudley Henriques" wrote in message
...

Glad you liked the report.
The Mustang is really very easy to fly. It does require constant attention
and doesn't suffer fools gladly however. Like any high performance
airplane, it has to be flown by the book and fooling around on the left
side of the envelope can get you killed in a hurry. Other than that....a
piece of cake.
Dudley Henriques


Always interested in reading warbird flying reports.

It always strikes me how amazing it must have felt in WW2 to be a fresh
young pilot entrusted with such a high performance machine, especially
relative to other transport in the 40's.

I wonder how many found it too much and came to grief - were there any
trainer versions of the P51D or was the first flight always the first solo
as well?

"Henry Spencer" wrote in message
...
In article ,
Blueskies wrote:
: The 3 Gs is at the backs of the occupants (and along that same axis for
the
: vehicle.) This is the same if they are heads up or heads down.
: If you lie with your back on the floor, you feel the same 1 G if your
head
: is facing north or south.

Not talking about facing north or south, they're talking about hanging
from your feet or standing upright...

When all the forces (engine thrust and air drag) are from your back to
your chest or vice versa, being head-up or head-down is precisely the same
as being head-northward or head-southward while lying on your back on
Earth, i.e. it makes not the slightest difference in what you feel.

The shuttle in ascent is in free fall except for thrust and drag. The
ascent path, and the shuttle's orientation during ascent, are carefully
chosen to *avoid* having the wings generate lift. The wings are not
strong enough to provide any useful amount of lift during ascent, and
the dominant concern is to avoid tearing them off by overloading them.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |


That's interesting, I'd wondered about that.

Is it also the case that the zero-lift trajectory you describe is very
similar to the optimum flight path for orbital insertion? Or is a lot more
fuel used because of it?

MichaelJP wrote:
I wonder how many found it too much and came to grief - were there any
trainer versions of the P51D or was the first flight always the first solo
as well?


I don't think I've ever seen a trainer P-51, in fact most U.S. WW II
fighter didn't have a trainer version.
I assume that after you had done enough hours in a Texan trainer they
assumed you were ready to take on a Mustang, although I have heard of
some pilots training stateside in P-39s before moving up to P-47s or
P-51s overseas.
(Chuck Yeager for instance)

Pat

"Herb Schaltegger" wrote in
message .com...
We loaded pellets into our Crossman airguns, but the principle was the
same. :-)

My brother and I used to sink battleship models that way. Once surfaced and
dried out again, a piece of paper coated with glue made it seaworthy again.
We had many models that started with styrene and ended with paper mache.

On Wed, 10 Jan 2007 18:58:43 -0600, Scott Hedrick wrote
(in article ):


"Herb Schaltegger" wrote in
message .com...
We loaded pellets into our Crossman airguns, but the principle was the
same. :-)

My brother and I used to sink battleship models that way. Once surfaced and
dried out again, a piece of paper coated with glue made it seaworthy again.
We had many models that started with styrene and ended with paper mache.



We also used to use bags full of those green plastic army men as BB
targets. I will never forget my favorite lucky shot. You remember
that guy who was standing up, arm hauled back with grenade in hand
ready to throw? I once managed to hit one of those guys dead-center in
the head, causing the plastic to extrude into a perfectly circular ring
around the guy's brand-new copper face. :-D


--
Herb Schaltegger
"You can run on for a long time . . . sooner or later, God'll cut you
down." - Johnny Cash
http://www.angryherb.net

Scott Hedrick wrote:

My brother and I used to sink battleship models that way. Once surfaced and
dried out again, a piece of paper coated with glue made it seaworthy again.
We had many models that started with styrene and ended with paper mache.


There is a group of ship modelers who build radio controlled warships
out of balsa wood, plywood, and Silkspan fabric that are themselves
equipped with remote control BB guns and go out sailing around sinking
each other.
The radio gear is kept in a BB protected waterproof container so that
it doesn't get damaged when the ship goes down.
http://www.modelwarshipcombat.com/
This must be a _lot_ of fun! :-)

Pat

In article ,
MichaelJP wrote:
chosen to *avoid* having the wings generate lift. The wings are not
strong enough to provide any useful amount of lift during ascent, and
the dominant concern is to avoid tearing them off by overloading them.

Is it also the case that the zero-lift trajectory you describe is very
similar to the optimum flight path for orbital insertion? Or is a lot more
fuel used because of it?

Yes and no. :-)

If memory serves, the ascent trajectory is pretty close to what a wingless
rocket with similar mass and propulsion characteristics would fly. Flying
even slightly sideways at supersonic speeds is very hard on lightweight
structures; even jet fighters, built for violent maneuvering, can handle
only a very little bit of this. Rockets normally take considerable pains
to fly pretty much(*) straight "into the wind" until clear of most of the
atmosphere. The shuttle trajectory isn't *exactly* what a wingless rocket
would use, because the trajectory that minimizes loads on the orbiter
wings isn't exactly the trajectory that would minimize structural loads in
general -- the wings have priority. But the penalty for this is small.

(* There are minor exceptions, in which lift can be of some use after the
air thins out, plus some complications for air-launched rockets like
Pegasus. But this is still basically correct. )

*However*, there is a more general caveat: even the wingless-rocket
trajectory actually isn't optimal. For one thing, an optimal ascent would
tip over toward the horizontal much more quickly. On Earth, the early
ascent has to be close to vertical, to get the rocket up out of the
atmosphere before the speed builds up too much. For another thing, even
disregarding that, the straight-into-the-wind trajectory isn't exactly
optimal, although it's not too far off.

The only rocket ascent that was ever able to use a truly optimized
trajectory was the Apollo LM ascent stage's departure from the Moon. On
Earth, you inevitably pay some price for the necessities of getting clear
of the atmosphere quickly and pointing straight into the wind while you
do. It's not huge, but it's significant. This is one of the two big
technical advantages of air launch -- starting from even 30,000ft means
you're dealing with considerably thinner air, reducing the price tag
noticeably. (The other is also related to thinner air: rocket engines
are more efficient with less back pressure. The forward speed of the
aircraft is a relatively minor gain by comparison, unless it's a pretty
unusual aircraft.)
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |