Low-Q, High-Q, and 'Normal-Q' Ascent Profiles -- Clarification Needed

"Craig Fink" wrote wisdom

Perfectly sensible!

Now, did we go to Hi-Q on account of the need to
recover some lost performance on high-inclination
missions -- in other words, was Hi-Q developed
and implemented in order to do 51.6 degree orbits?

=?ISO-8859-15?Q?Jan_Vorbr=FCggen?= wrote
in :

1000 lbs is about right for the loss from high-Q to low-Q. 121
could spare
it because they had around 1900 lbs margin. 115 and other
performance- critical flights will need some other solution.

The other quesions is: What problem does this solve? OK, so there is
less aero stress on the orbiter including its TPS.

You're missing half the picture. There is also less aero stress on the
tank.

How does that
influence the chance that any foam from the tank actually impacts the
TPS? It seems to me the mechanism could actually work in the other
direction: higher Q could mean less chance of hitting the orbiter with
debris. So what's actually the case and the rationale?

Less stress on the tank means lower probability of foam coming off in the
first place.

The recent wind tunnel tests on the ice/frost ramps show foam liberation is
only a problem above 735 psf. Low-Q will stay under 700 psf.


--
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check "Organization" (I am not assimilated) and
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Craig Fink wrote in
news
On Tue, 09 May 2006 17:47:40 -0500, Jorge R. Frank wrote:

Craig Fink wrote in
news
On Mon, 08 May 2006 14:06:24 +0000, Jim Oberg wrote:

Low-Q, High-Q, and 'Normal-Q' Ascent Profiles -- Clarification
Needed

In recent discussions about lowering the Q on the
121 ascent profile, to the 'Lo-Q' trajectory (and
accepting the performance penalty), I saw some
remarks that the current ascent trajectory is
actually an innovation introduced for Mir and ISS
orbital inclinations, to regain some performance
lost by the higher inclination. Is that true -- and
what were the performance consequences?

As for the performance gain, they should have been quoting a
performance loss in their presentations.

I think Jim knew that - the "regain some performance" was in
reference to the switch *to* high-Q.

Well, the performance gain from a "Nominal" Q to High Q probably would
have been something like 300-400 lbs.

Thanks for the confirmation.

But, you say, all the ISS mission have zero margin.

No, I didn't. They *do* all have low margins, compared to what NASA has
historically carried for non-ISS flights.

--
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check "Organization" (I am not assimilated) and
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On Wed, 10 May 2006 09:25:01 -0500, Jorge R. Frank wrote:

Craig Fink wrote in
news
On Tue, 09 May 2006 17:47:40 -0500, Jorge R. Frank wrote:

Craig Fink wrote in
news
On Mon, 08 May 2006 14:06:24 +0000, Jim Oberg wrote:

Low-Q, High-Q, and 'Normal-Q' Ascent Profiles -- Clarification
Needed

In recent discussions about lowering the Q on the
121 ascent profile, to the 'Lo-Q' trajectory (and
accepting the performance penalty), I saw some
remarks that the current ascent trajectory is
actually an innovation introduced for Mir and ISS
orbital inclinations, to regain some performance
lost by the higher inclination. Is that true -- and
what were the performance consequences?

As for the performance gain, they should have been quoting a
performance loss in their presentations.

I think Jim knew that - the "regain some performance" was in
reference to the switch *to* high-Q.

Well, the performance gain from a "Nominal" Q to High Q probably would
have been something like 300-400 lbs.

Thanks for the confirmation.


Rhetorically But, you say, all the ISS mission have zero margin.


They *do* all have low margins, compared to what NASA has
historically carried for non-ISS flights.

Humm, makes me wonder how much margin has been thrown away in the Pacific
Ocean on all the Space Station Launches. 10,000.lbs? 20,000.lbs?

Launching on time with zero margin would have been a much better
performance enhancement than high-Q.

Best Performance Enhancement - Aluminum Lithium Tank

Smartest Performance Enhancements - Small Software related ones like
thrust paralleling, Staging pitch rate.

Ok Performance Enhancement - OMS assist burn.

Missed Performance Enhancements - Launch on Time, DOL Zero Margin
Ballasting.

Worst Performance Enhancement - High-Q first stage

--
Craig Fink
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On Wed, 10 May 2006 14:09:27 +0000, Jim Oberg wrote:


"Craig Fink" wrote wisdom

Perfectly sensible!

Now, did we go to Hi-Q on account of the need to
recover some lost performance on high-inclination
missions -- in other words, was Hi-Q developed
and implemented in order to do 51.6 degree orbits?

They never lost performance on high- inclination missions, it would be
better to just say that they didn't have the required performance to build
a space station in a high inclination orbit. That is, until they made some
performance enhancing changes. I'd say that you are correct with respect
to all the performance enhancements implemented after the decision was
made to place the Space Station in a high-inclination orbit.

With respect to the MIR Space Station missions, the Space Shuttle had all
the performance it need to complete those missions without any additional
performance. Additional performance was and always is nice, but not
necessary. They weren't taking large pieces of structure to the MIR.

--
Craig Fink
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We are in agreement re Mir, there was no performance issue because
so little payload was being carried.

But for ISS, I state again that 'performance was lost' due to the
switch from 28 to 52 degrees -- about 30% of deliverable weight
was lost because of energy factors getting into the desired orbit.

This was made up for, by using various techniques such as the
light-weight tank and, I'm now realizing, the 'Hi-Q' ascent that
increased dynamic loads on the ET foam and on the Orbiter TPS.

My point re the 'cost' of the inclination change is that these same
enhancement techniques would also have worked at 28 degrees,
and could have raised 'nominal payload' there from the baseline
100% of the mid-1990's planning, to about 135% (with the same
techniques that raised the 52 degree performance from the 70% figure
to about 100%).


"Craig Fink" wrote
They never lost performance on high- inclination missions, it would be
better to just say that they didn't have the required performance to build
a space station in a high inclination orbit. That is, until they made some
performance enhancing changes. I'd say that you are correct with respect
to all the performance enhancements implemented after the decision was
made to place the Space Station in a high-inclination orbit.

With respect to the MIR Space Station missions, the Space Shuttle had all
the performance it need to complete those missions without any additional
performance. Additional performance was and always is nice, but not
necessary. They weren't taking large pieces of structure to the MIR.

We're in agreement, just arguing over a nit in the connotation of the word
"lost". Lost implies something you had, which the Shuttle didn't have to
high inclination orbits, but did for 28.5 degrees. So, your right, it was
lost with the decision to change inclinations.

Your right, for 28.5 degree inclination, the performance enhancements
would have translated into far fewer flight to assemble the space station.

To some extent, both Challenger and Columbia Disaster had performance
issues related to their causes.

With Challenger, NASA focusing on filament wound SRBs to improve high
inclination performance instead of working on implementing an improved SRB
field joint that was on the drawing board. A design that probably wasn't
as good as the one implemented after the accident, but better than the one
that caused the accident.

And Columbia, Frank Jorge pointed out recent foam shedding studies wrt
dynamic pressure and High-Q design. That would be an interesting study to
look at. When I heard about High-Q it made me shake my head thinking about
what a poor way to get a tiny bit of performance at the expense of
increasing loads on the entire vehicle. One of those touchy feely things
that you know just can't be a good idea.

I'd guess the Shuttles design point in 70s was probably 28.5 degree
inclination orbit, requiring a huge post facto effort to change it to a
higher inclination.

Personally, I like the higher inclination orbit of the Space Station.
Looking out the window, the astronauts get to see much broader view of the
Earth. And on a clear night, everyone gets to look up and see a bright and
shinny symbol of "peaceful" international cooperation in space. Quietly
crossing all the boundaries we've created back here on Earth.


On Mon, 15 May 2006 10:06:24 +0000, Jim Oberg wrote:

We are in agreement re Mir, there was no performance issue because so
little payload was being carried.

But for ISS, I state again that 'performance was lost' due to the switch
from 28 to 52 degrees -- about 30% of deliverable weight was lost
because of energy factors getting into the desired orbit.

This was made up for, by using various techniques such as the
light-weight tank and, I'm now realizing, the 'Hi-Q' ascent that
increased dynamic loads on the ET foam and on the Orbiter TPS.

My point re the 'cost' of the inclination change is that these same
enhancement techniques would also have worked at 28 degrees, and could
have raised 'nominal payload' there from the baseline 100% of the
mid-1990's planning, to about 135% (with the same techniques that raised
the 52 degree performance from the 70% figure to about 100%).


"Craig Fink" wrote
They never lost performance on high- inclination missions, it would be
better to just say that they didn't have the required performance to
build a space station in a high inclination orbit. That is, until they
made some performance enhancing changes. I'd say that you are correct
with respect to all the performance enhancements implemented after the
decision was made to place the Space Station in a high-inclination
orbit.

With respect to the MIR Space Station missions, the Space Shuttle had
all the performance it need to complete those missions without any
additional performance. Additional performance was and always is nice,
but not necessary. They weren't taking large pieces of structure to the
MIR.

--
Craig Fink
Courtesy E-Mail Welcome @

Craig Fink wrote:
Your right, for 28.5 degree inclination, the performance enhancements
would have translated into far fewer flight to assemble the space station.

To some extent, both Challenger and Columbia Disaster had performance
issues related to their causes.
[...]
And Columbia, Frank Jorge pointed out recent foam shedding studies wrt
dynamic pressure and High-Q design. That would be an interesting study to
look at. When I heard about High-Q it made me shake my head thinking about
what a poor way to get a tiny bit of performance at the expense of
increasing loads on the entire vehicle. One of those touchy feely things
that you know just can't be a good idea.

I'm not sure I follow. Neither Challenger nor Columbia were flying in
high-inclination orbits on their final flights. Columbia's STS-117 was
39 degrees (about the same as STS-1 at 40 degrees). Challenger's
STS-51-L was at 28.5 degrees.

This thread seems to be hinting that the Russian involvement with their
51 degree inclinations had something to do with what happened. I see
no connection at all.