recent launch and Challenger question (two topics)

Greetings,

I have two questions I need help with;

Regarding the recent launch of the shuttle, it appeared to me that upon
liftoff the three challenger 'main' engines were off and remained off
throughout. My knowledge of past launches ("three at a hundred") is
these engines are started first before igniting the boosters as all
five are necessary to acheive desired result. The huge tank inbetween
the SRMs holds the Hydrogen and Oxygen for which is used by the three
shuttle main engines. Huge tank, three engines .. and all three were
off in the launch and subsequent footage of ascent.

What did I miss ????

......
Number two. A good while back I reviewed the Challenger disaster
and found it peculiar that, when approaching the zone of maximum
dynamic pressure, the three main engines were brought up to full power
(some 10 or 20 seconds before crossing (?)). I would think that one
does not approach maximum dynamic loading at full throttle, and though
'they' (the computer that actually flys it) did reduce the power,
resumption to 100% occured well in advance of max-Q, which has the
appearance of being an error or a hazardous shortage of intelligence.


What did I miss ??

We send astronauts into space without a means of escape, fail to tell
the people that those astronauts died hitting the water, and under the
cover of a space program, madly pursue the weaponization of space as
though being an evil empire were somehow a good deed.

Ain't that America.

Agent X

On Tue, 02 Aug 2005 22:21:28 -0700, grunt wrote:

Greetings,

I have two questions I need help with;

Regarding the recent launch of the shuttle, it appeared to me that upon
liftoff the three challenger 'main' engines were off and remained off
throughout. My knowledge of past launches ("three at a hundred") is
these engines are started first before igniting the boosters as all
five are necessary to acheive desired result. The huge tank inbetween
the SRMs holds the Hydrogen and Oxygen for which is used by the three
shuttle main engines. Huge tank, three engines .. and all three were
off in the launch and subsequent footage of ascent.

What did I miss ????

The three large hydrogen-oxygen flames coming out the engine nozzles.
They're very very pale blue, and were swamped out by the plumes
from the SRBs, and washed-out by the blue sky background. IOW, they
were going full-throttle for the whole ascent.

Hope This Helps!
Rich

On 2 Aug 2005 22:21:28 -0700, "grunt" wrote:

Greetings,

I have two questions I need help with;

Regarding the recent launch of the shuttle, it appeared to me that upon
liftoff the three challenger 'main' engines were off and remained off
throughout.

What did I miss ????

That the three Main Engines were in fact up and running at liftoff.
"http://images.ksc.nasa.gov/photos/1986/high/KSC-86PC-0081.jpg"

Brian

Rich Grise ) writes:
On Tue, 02 Aug 2005 22:21:28 -0700, grunt wrote:

Greetings,

I have two questions I need help with;

Regarding the recent launch of the shuttle, it appeared to me that upon
liftoff the three challenger 'main' engines were off and remained off
throughout. My knowledge of past launches ("three at a hundred") is
these engines are started first before igniting the boosters as all
five are necessary to acheive desired result. The huge tank inbetween
the SRMs holds the Hydrogen and Oxygen for which is used by the three
shuttle main engines. Huge tank, three engines .. and all three were
off in the launch and subsequent footage of ascent.

What did I miss ????

The three large hydrogen-oxygen flames coming out the engine nozzles.
They're very very pale blue, and were swamped out by the plumes
from the SRBs, and washed-out by the blue sky background. IOW, they
were going full-throttle for the whole ascent.

Not quite. Approaching Max Q, about 55 seconds up, the shuttle main
engines throttled back to about 65% thrust. As they were coming out
of that short time and flight period, they were throttled back up.

The SRBs, of course, cannot be throttled up or down.

Andre
--
" I'm a man... But, I can change... If I have to... I guess. "
The Man Prayer, Red Green.

Thanks.. Now I think I wasn't paying attention. I've been making
simple solid rocket motors for the past year and the jet is always
visible.

Re; "they were going full-throttle for the whole ascent" ... um, that
would be dangerous, past practice was to throttle back the main engines
to a tad less than 70 part way up, then resume full throttle after
passing through the max dynamic load altitude. I'm inclinded to think
this practice hasn't changed.

Why this was not done correctly, as my original question (part 2)
asked, for the challenger, remains a mystery to me .. and there is a
shade of doubt as to whether or not there was a coverup so typical of
this wretched government.

"grunt" ) writes:
Thanks.. Now I think I wasn't paying attention. I've been making
simple solid rocket motors for the past year and the jet is always
visible.

Indeed. If you look up footage of Titan 2 launches, such as in the
gemini flights, you'll also see very little visible exhaust in the
first stage's firing.

Different engines using different fuels may create different exhausts.

Re; "they were going full-throttle for the whole ascent" ... um, that
would be dangerous, past practice was to throttle back the main engines
to a tad less than 70 part way up, then resume full throttle after
passing through the max dynamic load altitude. I'm inclinded to think
this practice hasn't changed.

Correct. It has not.

Why this was not done correctly, as my original question (part 2)
asked, for the challenger, remains a mystery to me .. and there is a
shade of doubt as to whether or not there was a coverup so typical of
this wretched government.

I don't recall your specific question 2, but there are several good
books available on the topic of the Challenger and it's loss and the
investigation into that, so you can easily find out what you want
to know. The Rogers Commission Report is a good place to start.

Andre



--
" I'm a man... But, I can change... If I have to... I guess. "
The Man Prayer, Red Green.

On Wed, 3 Aug 2005 14:20:35 -0500, grunt wrote
(in article . com):


Why this was not done correctly, as my original question (part 2)
asked, for the challenger, remains a mystery to me

It shouldn't "remain" a mystery, because there's no mystery at all.
Challenger had passed Max-Q before throttle-up; the call wasn't to go
to throttle up at Max-q. The call is an acknowledgment of the
throttling event after the fact.

.. and there is a
shade of doubt as to whether or not there was a coverup so typical of
this wretched government.

There's no doubt at all about a cover-up. There was none. Park your
paranoia at the door to s.s.* please. See the following sites for all
you need to know in order to understand STS-51L:
http://home.austin.rr.com/sts51lvideo/
and
http://home.houston.rr.com/fancijon/conspiracy.pdf

--
"Fame may be fleeting but obscurity is forever." ~Anonymous
"I believe as little as possible and know as much as I can."
~Todd Stuart Phillips
www.angryherb.net

"Andre Lieven" wrote in message
...

Not quite. Approaching Max Q, about 55 seconds up, the shuttle main
engines throttled back to about 65% thrust. As they were coming out
of that short time and flight period, they were throttled back up.

The SRBs, of course, cannot be throttled up or down.

But their thrust level does vary over the course of their burn. You can
control the thrust versus time curve of a core burning solid rocket booster
by changing the cross section of the hole (core).

Here's a quote:

The thrust profile over time can be controlled by grain geometry. For
example, a star shaped hole down the center of the grain will have greater
initial thrust because of the additional surface area. As the star points
are burned up, the surface area and thrust are reduced.

This is from: http://en.wikipedia.org/wiki/Solid-propellant

You'll note that reducing thrust as time goes on helps to limit the
acceleration of the launch vehicle, which corresponds to the g-load that the
payload and/or crew feels. On the shuttle, this is limited to something
like 3 g's, if I remember correctly.

Jeff
--
Remove icky phrase from email address to get a valid address.

"Jeff Findley" ) writes:
"Andre Lieven" wrote in message
...

Not quite. Approaching Max Q, about 55 seconds up, the shuttle main
engines throttled back to about 65% thrust. As they were coming out
of that short time and flight period, they were throttled back up.

The SRBs, of course, cannot be throttled up or down.

But their thrust level does vary over the course of their burn.

Throttling is a statement that direct and timely control of such is
possible. With the SRs, as it's NOT, the statement is wrong.

You can
control the thrust versus time curve of a core burning solid rocket booster
by changing the cross section of the hole (core).

Here's a quote:

The thrust profile over time can be controlled by grain geometry. For
example, a star shaped hole down the center of the grain will have greater
initial thrust because of the additional surface area. As the star points
are burned up, the surface area and thrust are reduced.

This is from: http://en.wikipedia.org/wiki/Solid-propellant

You'll note that reducing thrust as time goes on helps to limit the
acceleration of the launch vehicle, which corresponds to the g-load that
the payload and/or crew feels. On the shuttle, this is limited to
something like 3 g's, if I remember correctly.

All of which has AbZero to do with active throttling...

Andre


--
" I'm a man... But, I can change... If I have to... I guess. "
The Man Prayer, Red Green.

On 3 Aug 2005 12:20:35 -0700, "grunt" wrote:

Why this was not done correctly, as my original question (part 2)
asked, for the challenger, remains a mystery to me .. and there is a
shade of doubt as to whether or not there was a coverup so typical of
this wretched government.

FYI... here is the STS-113 launch timeline...

T+0:00 Launch
T+0:11 Start Roll
T+0:18 End Roll
T+0:32 Throttle-Down
T+0:48 Throttle-Up
T+1:01 Max Dynamic Pressure
T+2:03 SRB Separation

Here's the relevant passage from the STS News Reference (1988)...

http://science.ksc.nasa.gov/shuttle/...f/sts_mes.html

"During the first 90 seconds of flight, the flight control system
provides load relief by making adjustments to reduce vehicle loads at
the expense of maintaining a precise trajectory profile. A special
schedule of elevon position with respect to velocity is followed to
protect the wings from excessive loads and to hold the body flap and
rudder/speed brake in place. The surface position indicator displays
the position of the aerosurfaces. To keep the dynamic pressure on the
vehicle below a specified level, on the order of 580 pounds per square
foot (max q), the main engines are throttled down at approximately 26
seconds and throttled back up at approximately 60 seconds. This also
reduces heating on the vehicle. Because of the throttling at this
time, the term ''thrust bucket'' evolved. Maximum dynamic pressure
occurs shortly after throttle up."