High-Q

I think that was what it was called.. they said (forget who "they" is
but, anyway..) the last flight, the ascent was done under a
lower-stress profile, but this one was done under higher-stress.. how
do they do that, since on tv it looks identical - is it in the ssme
throttling or something else?
I think it was mentioned when someone was talking about the LOX feed
line was flexing more than usual, but it was alright because it was a
result of the higher-stress profile they were flying today...

On Sat, 09 Sep 2006 14:56:45 -0700, john2375 wrote:

I think that was what it was called.. they said (forget who "they" is
but, anyway..) the last flight, the ascent was done under a
lower-stress profile, but this one was done under higher-stress.. how
do they do that, since on tv it looks identical - is it in the ssme
throttling or something else?
I think it was mentioned when someone was talking about the LOX feed
line was flexing more than usual, but it was alright because it was a
result of the higher-stress profile they were flying today...

Hummm, they went back to High-Q already.

Throttle profile during the bucket and the Pitch profile starting right
after tower clear are used to target the desired dynamic pressure, amoung
other things.

--
Craig Fink
Courtesy E-Mail Welcome @

"Craig Fink" wrote in message
news
On Sat, 09 Sep 2006 14:56:45 -0700, john2375 wrote:

I think that was what it was called.. they said (forget who "they" is
but, anyway..) the last flight, the ascent was done under a
lower-stress profile, but this one was done under higher-stress.. how
do they do that, since on tv it looks identical - is it in the ssme
throttling or something else?
I think it was mentioned when someone was talking about the LOX feed
line was flexing more than usual, but it was alright because it was a
result of the higher-stress profile they were flying today...

Hummm, they went back to High-Q already.

Throttle profile during the bucket and the Pitch profile starting right
after tower clear are used to target the desired dynamic pressure, amoung
other things.


--
Danny Dot wrote:

This is correct. The high-q flights don't climb as fast. They are in the
thicker air for longer. This helps NASA carry more into orbit. The truss
on this flight is pretty heavy. I can only assume the high-q profile was
needed to carry the payload into orbit.

Look at my site and see how NASA treats a creative mind!!!
The summary is "Not Very Well" :-)
www.mobbinggonemad.org

--
Craig Fink
Courtesy E-Mail Welcome @

"Danny Dot" wrote in
:

This is correct. The high-q flights don't climb as fast. They are in
the thicker air for longer. This helps NASA carry more into orbit.
The truss on this flight is pretty heavy. I can only assume the
high-q profile was needed to carry the payload into orbit.

That's right. The delta between low-Q and high-Q is in the 900-1000 lbm
range. STS-121 went low-Q since they had an ascent performance margin of
almost 2000 lbm and could afford the hit. STS-115 would have had negative
margin with low-Q.


--
JRF

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

On Sun, 10 Sep 2006 03:26:39 +0000, Danny Dot wrote:


"Craig Fink" wrote in message
news
On Sat, 09 Sep 2006 14:56:45 -0700, john2375 wrote:

I think that was what it was called.. they said (forget who "they" is
but, anyway..) the last flight, the ascent was done under a
lower-stress profile, but this one was done under higher-stress.. how
do they do that, since on tv it looks identical - is it in the ssme
throttling or something else?
I think it was mentioned when someone was talking about the LOX feed
line was flexing more than usual, but it was alright because it was a
result of the higher-stress profile they were flying today...

Hummm, they went back to High-Q already.

Throttle profile during the bucket and the Pitch profile starting right
after tower clear are used to target the desired dynamic pressure,
among other things.


--
Danny Dot wrote:

This is correct. The high-q flights don't climb as fast. They are in
the thicker air for longer. This helps NASA carry more into orbit. The
truss on this flight is pretty heavy. I can only assume the high-q
profile was needed to carry the payload into orbit.


Yes, they don't climb in altitude as fast, but they do accelerate faster
downrange. Accelerating down range (due to lower initial pitch angles),
more thrust during the throttle bucket, and lower vehicle mass (due to
smaller throttle bucket) all contribute to the increased performance
(payload). Staying in the thicker part of the atmosphere and higher
dynamic pressure actually tends to reduce payload.

For Low-Q missions, the trade-off in performance vs Qbar is high. A small
increases in Qbar yield large increase in performance. At Optimal-Q, which
is above high-Q, the trade-off is zero. Increasing or decreasing Qbar
yields zero increase or decrease in performance. High-Q is somewhere in
between Optimal-Q and Low-Q, reducing Qbar doesn't cost very much payload.

Vehicle loads are a different matter.

Prior to DOLILU, the Space Shuttle flew Pitch, Yaw, Throttle I-loads that
were designed months ahead of time using the average or mean wind of the
month. Usually, the month of launch, or for a season with similar winds.
If there were any significant slips, they would have to redesign the
I-loads or fly with ones designed for a different month. One of the
interesting things about the early shuttle flights was effect that real
winds of the day had on these "baseline" I-loads. Headwinds actually had
significantly more performance and tailwind reduced performance. Exactly
the opposite from what one would expect of headwinds and tailwinds. This
had to do with interaction of the real wind and the flight software's
"load relief" function.

With respect to the low margin on this current flight, there are many
things that go into determining how much payload can be taken to the Space
Station. As the mission is designed, extra margin is booked on the flight
to account for unknowns. Flight performance reserve, launch window... and
even some margin to account for headwinds. All these thing must be taken
into account and performance set aside and not used. But. on the Day of
Launch, some of these things actually move from the “unknown” category
into the known category and it is to late to add or remove payload. In
particular the winds, they are measured and now become a known quantity.
Headwinds reducing performance, and tailwinds adding performance. So, on a
High-Q mission with a large tailwind, there is plenty of performance
margin to pitch the vehicle up and throttle back a little to reduce Q-bar
and loads. Also, on High-Q missions a little bit of day of launch planned
performance reduction would yield a large reductions in Qbar and loads.

--
Craig Fink
Courtesy E-Mail Welcome @

On Sun, 10 Sep 2006 02:41:59 -0500, Jorge R. Frank wrote:

"Danny Dot" wrote in
:

This is correct. The high-q flights don't climb as fast. They are in
the thicker air for longer. This helps NASA carry more into orbit. The
truss on this flight is pretty heavy. I can only assume the high-q
profile was needed to carry the payload into orbit.

That's right. The delta between low-Q and high-Q is in the 900-1000 lbm
range. STS-121 went low-Q since they had an ascent performance margin of
almost 2000 lbm and could afford the hit. STS-115 would have had
negative margin with low-Q.

It's not a switch, low-Q to high-Q. The Shuttle can fly anywhere in
between or even lower than low-Q. High-Q is just the upper constraint that
is closest to the performance optimal, and still contains the necessary
reserves to account for dispersions.

--
Craig Fink
Courtesy E-Mail Welcome @

"Danny Dot" wrote in message
...


This is correct. The high-q flights don't climb as fast. They are in the
thicker air for longer. This helps NASA carry more into orbit. The truss
on this flight is pretty heavy. I can only assume the high-q profile was
needed to carry the payload into orbit.

Look at my site and see how NASA treats a creative mind!!!
The summary is "Not Very Well" :-)
www.mobbinggonemad.org


I believe that this was the heaviest payload ever carried to orbit by
shuttle (STS)

gb

On Sun, 10 Sep 2006 07:52:51 -0500, wrote:

"Danny Dot" wrote in message
...


This is correct. The high-q flights don't climb as fast. They are in the
thicker air for longer. This helps NASA carry more into orbit. The truss
on this flight is pretty heavy. I can only assume the high-q profile was
needed to carry the payload into orbit.

Look at my site and see how NASA treats a creative mind!!!
The summary is "Not Very Well" :-)
www.mobbinggonemad.org


I believe that this was the heaviest payload ever carried to orbit by
shuttle (STS)

A misconception, here is a thread on the subject

http://groups.google.com/group/sci.s...2d363f66cfbf5a


--
Craig Fink
Courtesy E-Mail Welcome @

"g. beat" @spam protected wrote in
:

"Danny Dot" wrote in message
...


This is correct. The high-q flights don't climb as fast. They are
in the thicker air for longer. This helps NASA carry more into
orbit. The truss on this flight is pretty heavy. I can only assume
the high-q profile was needed to carry the payload into orbit.

Look at my site and see how NASA treats a creative mind!!!
The summary is "Not Very Well" :-)
www.mobbinggonemad.org


I believe that this was the heaviest payload ever carried to orbit by
shuttle (STS)

If by "this" you mean the P3/P4 truss, it's been labeled as such but it's
not. By a very slim margin, it's the heaviest ever carried to ISS orbit.


--
JRF

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

On Sun, 10 Sep 2006 07:52:51 -0500, "g. beat" @spam protected
wrote:

I believe that this was the heaviest payload ever carried to orbit by
shuttle (STS)

No, it is seventeenth heaviest.

All of the Shuttle missions that used the Inertial Upper Stage booster
to send payloads to high orbit or escape velocity were much heavier,
as were a few other missions...

STS-93 Chandra/IUS 50,212 lbs.
STS-51L TDRS-B/IUS 48,633 lbs.
STS-43 TDRS-E/IUS 46,712 lbs.
STS-6 TDRS-A/IUS 46,662 lbs.
STS-54 TDRS-F/IUS 46,540 lbs.
STS-41 Ulysses/IUS 46,173 lbs.
STS-34 Galileo/IUS 45,905 lbs.
STS-30 Magellan/IUS 45,823 lbs.
STS-29 TDRS-D/IUS 45.316 lbs.
STS-44 DSP-F16/IUS 44,637 lbs.
STS-26 TDRS-C/IUS 44,601 lbs.
STS-61B 3 Comsats 42,788 lbs.
STS-51 ACTS/TOS 42,637 lbs.
STS-92 ITS Z1 & PMA 41,952 lbs.
STS-41D 3 Comsats 41,382 lbs.
STS-97 ITS P6 41,314 lbs
STS-115 ITS P3/P4 40,743 lbs.

Souce: Jenkins, and Jonathan's Space Reports

While there have been several news references to STS-115 and P3/P4
being the heaviest payload send to ISS on the Shuttle so far, I can't
find data even close to corroborating that. By these numbers, it is
third.

Brian