"Scott Lowther" wrote:
Charleston wrote:
"Scott Lowther" wrote:
Charleston wrote:

The data would not fit here well and any subsequent posts would make it
become difficult to read. I will post the raw "as received" STS 51-L
SRB chamber pressure data in its entirety on my website
www.challengerdisaster.info tonight.

I will look forward to that. Since I'll be responsible for analyzing the
ballistics of the two SRB's from the forthcoming launch in May, it should
be interesting to see what you have... and how you interpret it.


Great. It is now posted. Of course I look forward to your insight as
well.

At first glance, after converting the date and time into something Excel
can use and restting T0 to be ignition, the pressure dats looks pretty
normal up until 59 seconds or so, when the right-hand transducers all show
a decrease in chamber pressure compared to the left handers. Not overly
surprising given that there was a hole in the side of the booster, and
total port area was increased.

I put the data up as I received it, adjusting the headers slightly for
clarity, so that anyone familiar with same would recognize that I have
presented it the way NASA first saw it 19 years ago. I too, have set it up
in an Excel spreadsheet to examine it in a number of meaningful ways.

From your read of the data what is the data rate for xducers 1302 and 2302?
How about the other two sets of xducers? They do have data rates IIRC.

I can compare this data to recent RSRM motor firings no sweat, but
performance has changed a little since 86.

By all means please do.

But to first order the overall pressure trace up until T+59 seconds looks
about right.

Following the redesign of the SRBs a higher thrust differential between the
two boosters was allowed. The data I posted reflects rather sensitive
instrumentation with three significant figures right? Given the resolution
of the xducers at 1/1000 of a PSI, what do you suppose the actual accuracy
is in PSI? Don't bother looking in the PC report, you will not find it
anywhere in any of the five volumes. We can come back to the 59 second
issue later. It might be helpful.

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

Not back then, I must agree. Does that make it okay during steady state
burn? Today I sort of doubt you have those spreads between the xducers.
They have been under configuration control *since* STS 51-L. NASA is aware
of some relatively small perturbations in the pressure from reading to
reading, sure.

The data rate from the Xducers is achingly slow to this date

Quality high rate data is three things:

1. Expensive
2. Heavy
3. Processor intensive

Nevertheless, if one is going to stake a report on data like that to which I
have referred, it should be honestly presented, accurate within a tolerance
that makes the data truly relevant, and it should mate with applicable
photographic and related data measurements.

Now one more thing, looking at the data, what interpretive value would you
place on it during the first second following T= 0?

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