STS51L Accident Questions

D Schneider wrote:

Acutally, I'm finding Scott's discussion of the data to be pretty
interesting.

Woo hoo!

I'm hoping also that Mary will chime in, as the data streams
she has dealt with undoubtedly have artifacts and other details that
must
be dealt with before interpreting the data.

The Shuttle flight data is not what you might hope for. It was
restricted in its capabilities by 1970's computer capabilities, and it
just never got updated. This is partially due to inertia (getting the
new, far higher sample rate xducers approved is a rather time- and
taxpayer-dollar-consuming enterprise), and partially due to the fact
for a motor that runs for 2 minutes, 12.5 samples per second is
adequate for post-flight reconstruction. As mentioned before, it's not
really what you want for brief events, blips and initiation; but in 220
or so flights, there has never been an issue with any of the motors
except for Challenger... and that was hardly a ballistics problem. You
can not reasonably expect a motor to have a perfectly normal pressure
trace if you open a second port in the side...

The problem with interprettign the given Challenger data is due to some
goofy but explainable phenomena. For starters... the xducers *are* 25
samples per second, but only every other one is read, leading to 12.5
sps. Then there's the fact that there are two other, slower xducers...
and 5 does not go into 12.5, so you have to decide how you're going to
present these different data streams. The data given here presents them
all with a single time axis; the way we get the data from static tests
(again, haven't been here long enough for a flight...) is that each
xducer has it's own time *and* pressure column. So when we have xducers
of different rates, it can be difficult to work with. If you just want
to plot them together, that's easy, leav ethe data alone, they'll plot
just fine. But if you want to compare moment-by-moment performance, you
need to pick a sample rate, and then interpolate the others to fit that
data rate. This works, but it's not the data you were originally given,
and you have to be careful with that.

What was done with the Challenger data is not what we'd do today. What
they did Way Back Then was, it seems, to include every time point
recorded from all three xducer streams. That's good for plotting, but
it gives you some weird variability in percieved data rate. And then,
instead of interpolating between pressure data points, they simply
repeated the data between relevant time points. An odd way of going
about it, but an honest one, and one that can be easily interpretted if
you know how... and easily *mis*interpretted if you don't know how.




And so long as I'm on about the Shuttle SRB's... I think using the
single SRB/neo-S-IVb stage for a CEV launcher is a decent option
(insert disclaimer about working for the people who *make* the RSRM
here). Again, in 220 flights, there was not a single catastrophic event
within the SRBs... not many other propulsion systems can claim that.
Also, look at the Challenger: yes, the SRB caused that disaster... but
the SRB's *survived.* The ET and the Shuttle got converted into
confetti by the aero loads when the one SRB punched into the ET... but
the SRB's had to be blown up from the ground. Them suckers is *tough*.

Herb Schaltegger wrote:

Given Scott's current job and his experience with solid rockets
generally, his comments are very interesting. I further appreciate
his willingness to suspend any urge towards editorializing to discuss

the information actually available rather than shooting the
messenger.

In this case, the primary issue under discussion... the matter of
sample rates and the determination thereof... really is a
straightforward matter of numbers and knownign generally how the system
works. There is no real area for debate... the data is what it is, and
it appears fully consistent with what it's *supposed* to be.

Now, as for what happens with the data around 59 seconds, when the two
SRB's begin to diverge, THAT would be an area where interpretation and
debate can come in.

On Mon, 07 Mar 2005 14:29:16 -0600, Herb Schaltegger
wrote:

I have downloaded Daniel's spreadsheet...

....So did I. I fail to see what's interesting about his gambling
debts.

OM

--

"No ******* ever won a war by dying for | http://www.io.com/~o_m
his country. He won it by making the other | Sergeant-At-Arms
poor dumb ******* die for his country." | Human O-Ring Society

- General George S. Patton, Jr

"D Schneider" wrote in message
newspsm9990gdemtzlb@d3h1pn11...
OM om@our_blessed_lady_mary_of_the_holy_NASA_researc h_facility.org
wrote:

[...]
Again, kids, please. Just killfile every M***** and put them out of
our misery. Don't waste your time on them.

Acutally, I'm finding Scott's discussion of the data to be pretty
interesting.

Same here. Though it's bringing back some disturbing memories of working
with some 1980s era Perkin Elmer A/D converters (I want to say 3090, but I'm
sure that's just the IBM mainframe from college creeping in.)

Scott makes a point about voltages and all.

The work I was doing on was on software for thermal analysis. Easy enough
when the temperatures in the unit varied a few hundred degrees. Easy to add
correction factors. Then some smartasses (well ok, they had PhDs so they
were at least smart :-) started doing ceramics work over a thousand or more
degrees. That meant all our correction factors had to be extended, etc.


I'm hoping also that Mary will chime in, as the data streams
she has dealt with undoubtedly have artifacts and other details that must
be dealt with before interpreting the data.

/dps


--
Using Opera's revolutionary e-mail client: http://www.opera.com/m2/

OM om@our_blessed_lady_mary_of_the_holy_NASA_researc h_facility.org wrote
in :

On Mon, 07 Mar 2005 14:29:16 -0600, Herb Schaltegger
wrote:

I have downloaded Daniel's spreadsheet...

...So did I. I fail to see what's interesting about his gambling
debts.

You fail to see a lot of things.

--
JRF

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

Henry Spencer wrote:

In article .com,
wrote:


...During calibration, a "X millivolts = Y
psi" factor is worked out for each xducer. So even though you might see
a reading with numerous decimal points... 892.347 psi, say, what you
are actually seeing is what the conversion factor makes of, say, 68
millivolts. There's a lot of psi between 68 and 69 millivolts, so you
don't get the pressure readings between them. And yet you still wind up
with all those decimal points.



Only if the software doesn't judiciously round off the value to reflect
the limited precision of the original data. Keeping all those decimal
places is simply silly -- a waste of bytes and (as we've seen) a boobytrap
for incautious analysts -- but carelessly-written software *is* common.


Take a look at the data presented in the Excel file under discussion. In
particular, make a chart from it, using jsut the date points in a
scatter plot (no lines) and focus in on the first, say, 2 seconds.
You'll see horizontal bands of data points. If you look at the first 2
seconds and between 875 and 925 psi, the issue becomes clear. You have,
for instance, a number of readings for the 2302 xducer at 903.504 psi,
and some more at 905.493... and none in between. There is a quantum step
there. The readings are down to the milli-psi, but there is a difference
of nearly 2 psi in resolving power. It's precise, but not accurate.

On 08 Mar 2005 01:28:09 GMT, "Jorge R. Frank"
wrote:

OM om@our_blessed_lady_mary_of_the_holy_NASA_researc h_facility.org wrote
in :

On Mon, 07 Mar 2005 14:29:16 -0600, Herb Schaltegger
wrote:

I have downloaded Daniel's spreadsheet...

...So did I. I fail to see what's interesting about his gambling
debts.

You fail to see a lot of things.

....What I *do* see is a lot of good people around here falling into
yet -another- M***** family trap. And it's a ****ing shame, Jorge.

OM

--

"No ******* ever won a war by dying for | http://www.io.com/~o_m
his country. He won it by making the other | Sergeant-At-Arms
poor dumb ******* die for his country." | Human O-Ring Society

- General George S. Patton, Jr

Herb Schaltegger wrote:

So am I. I have downloaded Daniel's spreadsheet but I've done nothing
more than glance through the data; paying work beckons and all that.
Given Scott's current job and his experience with solid rockets
generally, his comments are very interesting. I further appreciate
his willingness to suspend any urge towards editorializing to discuss
the information actually available rather than shooting the messenger.





Pat read what Herb had written...Pat then looked out the window....but
surprisingly, there wasn't a lunar eclipse going on.
Pat then knew what the explanation was...if he concentrated very hard
like the book had taught him to, Loni Anderson would indeed appear naked
at his apartment door, and the rest of the dream would get even better. :-)

Pat

OM om@our_blessed_lady_mary_of_the_holy_NASA_researc h_facility.org
wrote in :

On 08 Mar 2005 01:28:09 GMT, "Jorge R. Frank"
wrote:

OM om@our_blessed_lady_mary_of_the_holy_NASA_researc h_facility.org
wrote in :

On Mon, 07 Mar 2005 14:29:16 -0600, Herb Schaltegger
wrote:

I have downloaded Daniel's spreadsheet...

...So did I. I fail to see what's interesting about his gambling
debts.

You fail to see a lot of things.

...What I *do* see is a lot of good people around here falling into
yet -another- M***** family trap. And it's a ****ing shame, Jorge.

It's even more of a ****ing shame that you fail to see your own culpability
in continuing it. You *know* that P4u1 M4x50n is a paranoid guy who
constantly Googles his own name to see if anyone's talking about him, and
yet you *insist* on continuing to bait him. How ****ing stupid is that, OM?
Let me spell it out for you: *You* are largely responsible for the repeated
return of the M4x50ns to this group. Or had you not noticed that they
mostly post in sci.space.history - not coincidentally your home group - and
for the most part leave the other sci.space.* groups alone? If you'd
****ing shut up instead of playing your little sadistic games, the M4x50n
infestation would have ended long ago.

Scott Lowther is handling this the right way. Watch, and learn.

--
JRF

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

"Scott Lowther" wrote:
Charleston wrote:

If you look at the first second of data again you will see that there are
25 data points.
That is an artifact of presentation. There are multpile xducers reading at
different rates. In order for Excel to plot them all on the same graph,
whoever compiled the data chose to give all three xducer readings a single
"time" column. As a result, every Xducer had it'd data repeated. In the
case of the 12.5 sps xducers, that meant repeatign each data poitn twice.
Note that in the first second, when pressure was ramping up, the data for
1302 and 2302 was paired.

No it is not an artifact of presentation. I believe it was a
misrepresentation by NASA. Please let me explain. The original data I
received was in Minitab format http://www.minitab.com/. IIRC, it was
recovered for me from a VAX computer tape at MSFC after an interesting and
laborious phone conversation involving a NASA lawyer, an SRM project
engineer, a Public Affairs FOIA officer, and on my end a longtime personal
friend, myself, two pens, and two steno pads. Subsequently I received the
data. You can now review a portion of that data in one of the many ways I
have reviewed it. In my job I look for patterns and lack thereof.

http://www.challengerdisaster.info/s...r1_t=0-t+1.xls
(Excel) or

http://www.challengerdisaster.info/s...r1_t=0-t+1.htm
(HTML for the Microsoft impaired)

My review of the data as posted at the above URL, led directly to a
subsequent phone call to the above engineer and an admission by him that for
the timeframe T+0 to T+1 second, no "real" data was available for STS 51-L
and therefore "theoretical trajectory based data was substituted instead".
When I asked him why I had not been told this fact upfront, no answer was
given, just silence. When I asked why there were two separate sets of data
embedded in the samples with contradictory data he again had no answer.


That first second of data is farcical

No. It's just presented poorly. Take out every other data poitn for 1302
and 2302. This is the result of having different sample rates and trying
to smash them all on the same graph.

Please graph the above two sets of data I have added to my website for that
first second on the same graph and let me know if you still think your
explanation works.

Which set of data points would you have me take out? When you separate the
two distinct streams of data as I have, they contradict themselves. Please
tell me which stream you would choose and why. Also, before anyone
overinterprets the data, you need to understand that there are at least two
more additional data sets for STS 51-L and neither of those data sets match
this one. I was careful to indicate that the data I presented was "raw" and
that it was just one version. It turns out to one of at least three
different versions. I also have the data for the first 24 flights and have
reviewed it as well.

So again I ask what is your read of the data rate for the STS 51-L flight
data on my website?

1,5, and 12.5 (not 12, as I said before). Again, look at the initial
ramp-up, and note the repeated readings.

Okay we disagree on whether the second one is 2 or 5 s/s. Is there any
particular reason you believe the second one is five? I only know what I
was told by the NASA engineer at the time they filled my request. Can you
explain the variable data rate? Do you need a few examples?

Ah yes precision and accuracy, first year chemistry, thanks. Accuracy is
indeed another matter. I expect that NASA would have a standard and
indeed they did. The CEI requirement was +- 15 PSI but there was no
requirement to actually calibrate the pressure transducers.
That seems massively unlikely. Did you look at the specifications for the
*transducers?* How about the work processes?

Massively unlikely? I'll tell you what, you can call it "unlikely" if you
want to, but you can always read the CEI document I was referring to for
yourself. I have posted one particular page from that document to
substantiate my claim. I have reviewed the entire document. As I stated
earlier the figures and tables were all missing.

http://www.challengerdisaster.info/h...c_page_5-2.doc

snip

Yes for the ignition transient, the data rate for STS 51-L was wholly
useless.

Not *wholly*, just annoyingly lean.

Yeah it was useless. You can't make any sense of it and what I was given
turned out to be a farce anyway. You can not get that first second of data.
I have tried several ways and have failed every single time.

To this day NASA can not definitively state what really happened
pressure-wise in that first 600 milliseconds other than the boosters did
ignite and pressurize.
And they did so nominally. Thing is, somethign goes funny at ignition,
funny enough to cause trouble, and it'll show up. Motors like the Shuttle
SRM are pretty stable... mess with them, and they'll settle back down. To
mess with them enough to cause trouble, you'd *really* have to mess with
them. Block the throat with a car-sized chunk of propellant, that sort of
thing. And that shows up.

Nominally? Show me the data.

As I said, I only really looked at the data for the first secodn or two.
Where do you see variability in the data rate?

That comment is quite frustrating. You have made comments vouching for this
data like.

"The data presented looks to be fully in compliance with what would have
been actually recorded. You can't present data that *wasn't* recorded."

"Neither the spread in readigns from Xducer to Xducer not the very jagged
appearance of the data are unusual."

All I ask of you or anyone here is that before you comment to the facts,
that you give at least one serious examination of all the data I have
provided. Only then can we continue this conversation with anything
resembling common ground.

Daniel
Mount Charleston, not Charleston SC
www.challengerdisaster.info