Pitch and roll

Apollo again. Just after clearing the tower, the SV does a pitch and
roll. The pitch I can see, get on to the correct trajectory. But what
is the roll for? Not like the shuttle with a highly asymetric stack.

--
Paul Repacholi 1 Crescent Rd.,
+61 (08) 9257-1001 Kalamunda.
West Australia 6076
comp.os.vms,- The Older, Grumpier Slashdot
Raw, Cooked or Well-done, it's all half baked.
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wrote:
Apollo again. Just after clearing the tower, the SV does a pitch and
roll. The pitch I can see, get on to the correct trajectory. But what
is the roll for? Not like the shuttle with a highly asymetric stack.


Huh, I'll have to watch some more film (what a great excuse).

Are you talking about the slight, controlled "fall" away from the tower
that the V does at liftoff, in order to avoid knocking into any swing
arms on the way up? You can see it in fotos taken from the proper angle;
iirc, just after liftoff before "tower clear". I thought it was an
optical illusion at first, but, yeah, it really was falling away from
the tower.

I'm wondering if what you're seeing there isn't just the V following the
path it was set on by the slight "falling" away.

I could never figure out the roll, either, for the same reason.

--

..

"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

"mike flugennock" wrote in message
rvers.com...
wrote:
Apollo again. Just after clearing the tower, the SV does a pitch
and
roll. The pitch I can see, get on to the correct trajectory. But
what
is the roll for? Not like the shuttle with a highly asymetric
stack.


Huh, I'll have to watch some more film (what a great excuse).

Are you talking about the slight, controlled "fall" away from the
tower
that the V does at liftoff, in order to avoid knocking into any
swing
arms on the way up? You can see it in fotos taken from the proper
angle;
iirc, just after liftoff before "tower clear". I thought it was an
optical illusion at first, but, yeah, it really was falling away
from
the tower.

I'm wondering if what you're seeing there isn't just the V following
the
path it was set on by the slight "falling" away.

I could never figure out the roll, either, for the same reason.

The "fall" away from the tower is a yaw movement intended to keep the
stack from being blown into the tower due to a sudden gust of wind.
The roll program is to align one of the axes of the S-V
instrumentation unit with the course trajectory to simplify the
computation, as that way the trajectory can be tracked in one axis
instead of two. Think 1960s computers and saving as many memory
locations and cpu cycles as you can!.

-
Jim

James Nowotarski wrote:
The roll program is to align one of the axes of the S-V
instrumentation unit with the course trajectory to simplify the
computation, as that way the trajectory can be tracked in one axis
instead of two.

Also, it puts the astronauts heads down. It would be somewhat
uncomfortable to have to fly to orbit with their seats at 45 degrees to
Earth gravity...

Mark

In article ,
wrote:
Apollo again. Just after clearing the tower, the SV does a pitch and
roll. The pitch I can see, get on to the correct trajectory. But what
is the roll for? Not like the shuttle with a highly asymetric stack.

The roll was done to get the pitch axis of the guidance system
perpendicular to the plane of the intended trajectory, to reduce guidance
to a (largely) two-dimensional problem. It was common for early rocket
guidance systems to need this; in pre-Saturn rockets, especially those
that didn't have computerized guidance, often the pad itself was rotated
to achieve this before launch.

A secondary motive was one the shuttle shares: to ensure the crew a view
of the horizon, for monitoring the ascent guidance. (The Apollo crews,
like the earlier shuttle crews, went up heads-down.)

If I recall correctly, there would have been no roll required for a
due-east launch -- the pads were aligned to the compass directions -- but
few or none of the Saturn V launches went due east.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

In article . com,
wrote:
Also, it puts the astronauts heads down. It would be somewhat
uncomfortable to have to fly to orbit with their seats at 45 degrees to
Earth gravity...

Wouldn't matter in the slightest, actually, apart from the odd view out
the window. The Gemini crews went to orbit heads-sideways (so that if
they had to eject because the vehicle was breaking up, they'd be neither
underneath the debris where it could fall on them, nor above it where they
could fall into it). Once off the pad, they're in free fall except for
engine thrust and aerodynamic forces.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

(Henry Spencer) wrote in :

In article ,
wrote:
Apollo again. Just after clearing the tower, the SV does a pitch and
roll. The pitch I can see, get on to the correct trajectory. But what
is the roll for? Not like the shuttle with a highly asymetric stack.

The roll was done to get the pitch axis of the guidance system
perpendicular to the plane of the intended trajectory, to reduce guidance
to a (largely) two-dimensional problem. It was common for early rocket
guidance systems to need this; in pre-Saturn rockets, especially those
that didn't have computerized guidance, often the pad itself was rotated
to achieve this before launch.

A secondary motive was one the shuttle shares: to ensure the crew a view
of the horizon, for monitoring the ascent guidance. (The Apollo crews,
like the earlier shuttle crews, went up heads-down.)

Arguably, the roll-to-heads-up occurs late enough during a shuttle ascent
that you don't need to qualify that statement with "earlier".

--
JRF

Reply-to address spam-proofed - to reply by E-mail,
check "Organization" (I am not assimilated) and
think one step ahead of IBM.

James Nowotarski wrote:


The "fall" away from the tower is a yaw movement intended to keep the
stack from being blown into the tower due to a sudden gust of wind...

....among other things, iirc from MWEA (at least I _think_ that's where I
read about avoiding a collision with the tower).

The roll program is to align one of the axes of the S-V
instrumentation unit with the course trajectory to simplify the
computation, as that way the trajectory can be tracked in one axis
instead of two. Think 1960s computers and saving as many memory
locations and cpu cycles as you can!.

Well, day-AM. I didn't know that.


--

..

"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

"James Nowotarski" writes:

The "fall" away from the tower is a yaw movement intended to keep
the stack from being blown into the tower due to a sudden gust of
wind. The roll program is to align one of the axes of the S-V
instrumentation unit with the course trajectory to simplify the
computation, as that way the trajectory can be tracked in one axis
instead of two. Think 1960s computers and saving as many memory
locations and cpu cycles as you can!.

Yep, that rings the bell! Having pulled tricks like that myself
with PDP-11 SCADA systems.

And thanks to Henry too.

--
Paul Repacholi 1 Crescent Rd.,
+61 (08) 9257-1001 Kalamunda.
West Australia 6076
comp.os.vms,- The Older, Grumpier Slashdot
Raw, Cooked or Well-done, it's all half baked.
EPIC, The Architecture of the future, always has been, always will be.

Henry Spencer wrote:
Once off the pad, they're in free fall except for
engine thrust and aerodynamic forces.

Ah, good point .

Mark