Why does the shuttle throttle on ascent?

John wrote:

That pictures seems to show a land launch from Launch Complex 25 at
Cape Canaveral Air Force Station, which might . . . I emphasize might
. . . suggest that the initial non vertical climb is how the vehicle
is designed to perform . . . interesting *S*

Blue skies




That's what I thought also.
This photo of another land launch, shows the same antenna in the
background, although this time the missile is ascending vertically:
http://www.bomb-shelter.net/images/s...ub_missile.jpg
You really want to see one starting at a angle, check this photo:
http://www.spacegatewaysupport.com/i...trident4sm.jpg
This one, on the other hand, seems to be going more vertical as it
climbs: http://www.sciprods.com/images/trident_ll_02m.jpg
I think I know what's going on here; If you are attacking a target
that's well under the missile's maximum range, you don't have to worry
about getting the optimal trajectory for low air drag, but can fire it
on a depressed trajectory so that it stays fairly low in altitude and
can get nearer its target before detection by enemy radar, making any
attempt to intercept it more difficult.
That's probably what the inclined launches are testing; they're trading
altitude and range for speed, and operating more like a field gun than a
howitzer.

Pat

That's what I thought also.
This photo of another land launch, shows the same antenna in the
background, although this time the missile is ascending vertically:
http://www.bomb-shelter.net/images/s...ub_missile.jpg
You really want to see one starting at a angle, check this photo:
http://www.spacegatewaysupport.com/i...trident4sm.jpg
This one, on the other hand, seems to be going more vertical as it climbs:
http://www.sciprods.com/images/trident_ll_02m.jpg
I think I know what's going on here; If you are attacking a target that's
well under the missile's maximum range, you don't have to worry about
getting the optimal trajectory for low air drag, but can fire it on a
depressed trajectory so that it stays fairly low in altitude and can get
nearer its target before detection by enemy radar, making any attempt to
intercept it more difficult.
That's probably what the inclined launches are testing; they're trading
altitude and range for speed, and operating more like a field gun than a
howitzer.

Pat

IIRC (I'll check with my co-worker that was on boomers), but I believe the
vertical launch tubes the hold the ICBMs are "tilted" slightly outboard and
are not truly vertical. I believe this was done so if the rocket motor did
not light, it would not come back down onto the boat.

Jason C

Pat Flannery wrote:
John wrote:

That pictures seems to show a land launch from Launch Complex 25 at
Cape Canaveral Air Force Station, which might . . . I emphasize might
. . . suggest that the initial non vertical climb is how the vehicle
is designed to perform . . . interesting *S*

Blue skies




That's what I thought also.
This photo of another land launch, shows the same antenna in the
background, although this time the missile is ascending vertically:
http://www.bomb-shelter.net/images/s...ub_missile.jpg
You really want to see one starting at a angle, check this photo:
http://www.spacegatewaysupport.com/i...trident4sm.jpg
This one, on the other hand, seems to be going more vertical as it
climbs: http://www.sciprods.com/images/trident_ll_02m.jpg
I think I know what's going on here; If you are attacking a target
that's well under the missile's maximum range, you don't have to worry
about getting the optimal trajectory for low air drag, but can fire it
on a depressed trajectory so that it stays fairly low in altitude and
can get nearer its target before detection by enemy radar, making any
attempt to intercept it more difficult.
That's probably what the inclined launches are testing; they're trading
altitude and range for speed, and operating more like a field gun than a
howitzer.

Pat
\
Pat,

The second pic seems to support Henry's thought that what we have been
seeing is a transient and that as the missle climbs it pitchs to a more
typical vertical ascent. I saw one or two of these from a long way off
.. . . and more importantly . . . a very long time ago . . . and to be
honest and I simply cannot remember what they looked like.

Now STS-1 . . . that I will always remember . . . after a steady diet
of Titan II's and Saturn V's, I remember being amazed at how fast the
shuttle left the pad (in a comparative sense)

Take care . . .

John

In article ,
Pat Flannery wrote:
No, I've seen films of the launch; it comes out of the water straight,
then immediately pitches over and climbs at a steep angle;
There's a video of a launch he
https://wrc.navair-rdte.navy.mil/war...bs/trident.mpg

Actually, on that video it looks like it does *both*: comes out of the
water more or less straight, pitches over fairly steeply, and then
gradually straightens out as it climbs -- not all the way to vertical, but
to a considerably less dramatic tilt than the initial pitchover produced.

Could be an engine-startup transient that the guidance system then sorted
out (in particular, transient flow separation during startup is not at all
rare, and can briefly produce large unwanted thrust vectoring), some sort
of guidance/control-startup transient, or a deliberate "get a bit of
horizontal distance from the sub immediately" maneuver.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

In article ,
Pat Flannery wrote:
I would have loved to have been there when the crew of sub saw film of
this for the first time:
http://hometown.aol.com/sdrcgeru/ima..._cartwheel.jpg :-)

Of course, the crew that *really* didn't want to hear/see anything like
that were the folks aboard the Ethan Allen in May 1962, when she did the
only US SLBM test ever with a live warhead...
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

Pat Flannery wrote:

http://www.abo.fi/~mlindroo/SpaceLVs/Slides/sld053.htm

A 747 with an SSME in the tail...

[Note to r.a.p. - that's a Space Shuttle Main Engine]

Brian Thorn wrote:
Coincidentally, History Channel this morning ran a show about the ICBM
Race and included Polaris launch footage. That roll was damned
impressive!

Is this the show that has the footage of the solid-fueled Minuteman
launch identified as a Titan II?

Pat

Mary Pegg wrote:
A 747 with an SSME in the tail...
The _New_ Boeing SST proposal! ;-)
It makes sense though... since you're storing LOX and LH2 on the 747
anyway for pumping into the ET at altitude, you might get some use out
of them to up its maximum release altitude at the same time.

Pat

In article ,
Pat Flannery wrote:
I'm really surprised that the small air-launched orbiter with giant drop
tank concept didn't get anywhere- both we and the Russians thought the
idea had enough merit to do designs of the concept...

Or without drop tank. Grumman's proposal to the SDIO SSTO competition
(won by McDD with DC-X) was a no-drop-tank orbiter, air launched from a
747, that used existing engines and quite ordinary structures.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

Henry Spencer wrote:

Of course, the crew that *really* didn't want to hear/see anything like
that were the folks aboard the Ethan Allen in May 1962, when she did the
only US SLBM test ever with a live warhead...


Frigate Bird! Hardly anyone knows we ever did that one:
http://www.navy.mil/navydata/cno/n87...igate_bird.htm
Where I'd have been a little queasy about being is on the Carbonero or
Medregal at twenty-five miles from the aim point, and thinking to
yourself "I sure hope that thing's guidance system works right." :-)

Pat