Re: SRB motion in 51L

[Herb Schaltegger]

In article >,
"Jon Berndt" > wrote:

> Given an SRB attached at the forward end at zero velocity and
> unaccelerated, how fast would it rotate about its forward attach point?
>
> Any guesses?

Well, there's your answer right there, Jon - if it's at rest (zero
velocity) and unaccelerated (= zero force), it will not rotate at all.

Next question, please.

--
Herb Schaltegger, B.S., J.D.
Reformed Aerospace Engineer
"Heisenberg might have been here."
~ Anonymous

[John Maxson]

Here comes the 'junk science' team. Give Herbs some
invalid assumptions, and he'll waste no time generating
'junk' argument, just for the sake of arguing. However,
he will scrupulously avoid the evidence he cannot refute.

--
John Thomas Maxson, Retired Engineer (Aerospace)
Author, The Betrayal of Mission 51-L (www.mission51l.com)



Herb Schaltegger > wrote in message
...
> In article >,
> "Jon Berndt" > wrote:
>
> > Given an SRB attached at the forward end at zero velocity and
> > unaccelerated, how fast would it rotate about its forward attach point?
> >
> > Any guesses?
>
> Well, there's your answer right there, Jon - if it's at rest (zero
> velocity) and unaccelerated (= zero force), it will not rotate at all.
>
> Next question, please.
>
> --
> Herb Schaltegger, B.S., J.D.
> Reformed Aerospace Engineer
> "Heisenberg might have been here."
> ~ Anonymous

[Jon Berndt]

"Jon Berndt" wrote:

> Just how fast could an SRB rotate about its forward attach point should it
> have come loose at the aft end? It's a massive object. Let's do a static, 2D
> analysis. Given an SRB attached at the forward end at zero velocity and
> unaccelerated, how fast would it rotate about its forward attach point?
>
> Any guesses?

Er ... let me elaborate.

The SRB is also thrusting. How fast would the SRB rotate about the
forward attach point if it was thrusting and the aft attachments were
severed suddenly? Ignore the effects of translational acceleration
under thrust and also aerodynamic effects (thus the caveats: at zero
velocity and unaccelerated).

Jon

[Jon Berndt]

"Herb Schaltegger" > wrote in message
>
> However, we don't really need to: we have video/film of what DID happen,
> remember? ;-)

Yep.

[Jon Berndt]

"Herb Schaltegger" > wrote in message

> I'm playing along at home, Jon, and I'm pretty sure I know where you're
> going with this. However, doesn't any rotation about the forward attach
> point depend to some extent on the gimbal angle of the nozzle at the
> time the aft end broke loose? In addition, the SRB has a steadily (and
> rapidly) decreasing mass and changing moments of inertia about it's own
> yaw/pitch axes. I can't do a simple calculation without more data.

The moment of inertia about the forward attach point (about an axis parallel
to the Z axis) at t+73 sec. is about 90,000,000 slug-ft^2. Angular
acceleration is defined:

a = M/I

M is the moment, which is the sum of the forces times the moment arm. The
moment arm is the SRB radius - about 6 ft. The total force is the thrust
minus the weight. (for our purposes in this example we are assuming the
shuttle is fixed in space in a vertical orientation). Let's say that the
thrust minus the weight of the SRB at this point in time is 2,200,000 lbs.
That gives a moment of about 13,200,000 ft.lbs. We can now calculate angular
acceleration as:

a = 13,200,000/90,000,000 =~ .15 rad/sec or ~8.4 deg/sec^2

How far would the SRB rotate in 0.75 seconds?

0.5*a*t^2

2.4 degrees.

How would being in accelerated flight and in high dynamic pressure affect
this?

This calculation also assumes that the nozzle was canted at zero degrees. In
all likelihood it was canted slightly in, so the rotational acceleration
would have been smaller.

The point is, without a moment to roll the stack, the stack would not have
rolled. Without the SRBs tilted in equal but opposite directions in the XZ
plane, there would be no moment. The SRB could not have moved so quickly as
to roll the stack in the time frame being referred to.

Jon

[Herb Schaltegger]

In article >,
"Jon Berndt" > wrote:

> "Herb Schaltegger" > wrote in message
>
> > I'm playing along at home, Jon, and I'm pretty sure I know where you're
> > going with this. However, doesn't any rotation about the forward attach
> > point depend to some extent on the gimbal angle of the nozzle at the
> > time the aft end broke loose? In addition, the SRB has a steadily (and
> > rapidly) decreasing mass and changing moments of inertia about it's own
> > yaw/pitch axes. I can't do a simple calculation without more data.
>
> The moment of inertia about the forward attach point (about an axis parallel
> to the Z axis) at t+73 sec. is about 90,000,000 slug-ft^2. Angular
> acceleration is defined:
>
> a = M/I
>
> M is the moment, which is the sum of the forces times the moment arm. The
> moment arm is the SRB radius - about 6 ft. The total force is the thrust
> minus the weight. (for our purposes in this example we are assuming the
> shuttle is fixed in space in a vertical orientation). Let's say that the
> thrust minus the weight of the SRB at this point in time is 2,200,000 lbs.
> That gives a moment of about 13,200,000 ft.lbs. We can now calculate angular
> acceleration as:
>
> a = 13,200,000/90,000,000 =~ .15 rad/sec or ~8.4 deg/sec^2
>
> How far would the SRB rotate in 0.75 seconds?
>
> 0.5*a*t^2
>
> 2.4 degrees.
>
> How would being in accelerated flight and in high dynamic pressure affect
> this?
>
> This calculation also assumes that the nozzle was canted at zero degrees. In
> all likelihood it was canted slightly in, so the rotational acceleration
> would have been smaller.
>
> The point is, without a moment to roll the stack, the stack would not have
> rolled. Without the SRBs tilted in equal but opposite directions in the XZ
> plane, there would be no moment. The SRB could not have moved so quickly as
> to roll the stack in the time frame being referred to.
>
> Jon
>
[/ASIDE] I *LOVE* it when the Prof walks the class through the answer!
Thanks, Jon! :-) [/END ASIDE]

Now if only either Mr. Maxson (the Elder or the Younger) would provide
us with their mathematical proofs that the SRBs were even CAPABLE of
crossing.

--
Herb Schaltegger, B.S., J.D.
Reformed Aerospace Engineer
"Heisenberg might have been here."
~ Anonymous

[Jon Berndt]

"Herb Schaltegger" > wrote in message
> >
> [/ASIDE] I *LOVE* it when the Prof walks the class through the answer!
> Thanks, Jon! :-) [/END ASIDE]
>
> Now if only either Mr. Maxson (the Elder or the Younger) would provide
> us with their mathematical proofs that the SRBs were even CAPABLE of
> crossing.

But wait, there's more!

[reference Figures 60, 71, Volume 3, Appendix N of the Presidential
Commission report:
http://history.nasa.gov/rogersrep/v3n44.htm,
http://history.nasa.gov/rogersrep/v3n50a.htm,
]

Two actuators on each SRB control the gimballing of the SRB nozzle, one for
"rock" and one for "tilt". [reference
http://history.nasa.gov/rogersrep/v3o238.htm]. The actuators are placed at
locations 90 degrees apart circumferentially about the SRM nozzle. If one
views the stack from the bottom such that the orbiter is on top, the left
SRB is on the left, and the right booster is on the right, the actuators are
placed as follows:

Left Booster
------------
Rock actuator is located 45 degrees clockwise from the line extending from
the left SRB center out to the left. The Tilt actuator is located 45 degrees
*counter* clockwise from the line extending from the left SRB center out to
the left. A positive extension of the actuator pushes the bottom of the
nozzle away from the actuator, and roughly towards the ET.

Right Booster
------------
Rock actuator is located 45 degrees clockwise from the line extending from
the right SRB center out to the right. The Tilt actuator is located 45
degrees *counter* clockwise from the line extending from the right SRB
center out to the right. A positive extension of the actuator pushes the
bottom of the nozzle away from the actuator, and roughly towards the ET.

As one can see, the actuators are located on the outside of the SRB, and the
right SRB is like the left SRB except rotated 180 degrees (as far as the
actuators go).

The Accident
--------------

Armed with this knowledge, we can gain some more insight on the forces and
moments acting on the SRBs at detachment at or about 73.3 seconds. When the
right SRB became detached at the lower aft attachment it pivoted about the
new hinge line created by the aft upper attachment and the forward
attachment. You can see what appears to be the SRB breach plume rotation in
the E207 movie. When this movement happened it caused a rolling moment to
the stack. Given that the stack was in a "heads down" attitude as it climbed
towards orbit, the right SRB would have imparted a left wing down (towards
the ocean) moment, i.e. producing a positive rolling moment.

The flight control system sensed this incorrect motion and commanded the
SRBs appropriately to return to normal flight. Subsequent to the commands
sent to the left SRB actuators, the reported positions of the actuators
showed that the left SRB nozzle was angled away from the orbiter wing and
slightly inward. The result of this SRB orientation would be to provide a
negative rolling moment - i.e. it was moving to arrest the unexpected roll.

When the SRBs were suddenly "liberated" from the stack, the left SRB was
seen to angle off towards a lower trajectory - EXACTLY what would be
expected given the last reported position of the SRB nozzle: a nose outward
and SRB tail upward dynamic movement. The SRB nozzles would almost
certainly have moved to the center (null) position shortly after being
separated from the stack.

The SRB nozzle positions were certainly not oriented to produce a high rate
crossing maneuver.

Coupled with the knowledge of the high inertia of the SRBs, it is plainly
obvious that not only could the SRBs NOT move quickly enough to set the
stage for a subsequent crossing, but the positions of the nozzles were
commanded to arrest the right roll error present at the time of the
disintegration. The positions of the nozzles at this point explains fully
the resulting trajectory of each SRB after the disintegration.

Jon

[Charleston]

"Jon Berndt" > wrote:

> The Accident
> --------------
>
> Armed with this knowledge, we can gain some more insight on the forces and
> moments acting on the SRBs at detachment at or about 73.3 seconds.

Does the PC report tell us when telemetry from the SRBs ceased being
received by the orbiter? Was it the same for both SRBs or is that an
assumption? I think you would need to know that before going to far down
the path you discuss.

http://history.nasa.gov/rogersrep/v1ch3.htm see page 37-39. Amazingly it
is not there Jon. Telemetry from both SRBs ceased coming into the orbiter
at 73.09 seconds actually and I suspect that is when they really separated.
It may be important info and it can be found in the Range Safety Report,
IIRC.

--

Daniel
Mount Charleston, not Charleston, SC

[Jon Berndt]

"Charleston" > wrote in message

> Does the PC report tell us when telemetry from the SRBs ceased being
> received by the orbiter? Was it the same for both SRBs or is that an
> assumption? I think you would need to know that before going to far down
> the path you discuss.
>
> http://history.nasa.gov/rogersrep/v1ch3.htm see page 37-39. Amazingly it
> is not there Jon. Telemetry from both SRBs ceased coming into the orbiter
> at 73.09 seconds actually and I suspect that is when they really
separated.
> It may be important info and it can be found in the Range Safety Report,
> IIRC.


39:13.134 RH SRM pressure 19 psi lower than LH SRM 73.124 B47P2302C

which corresponds to 73.124 seconds MET.

The video evidence leads me to believe the no earlier than 73.3 second
figure.

Jon

[Jon Berndt]

"Charleston" > wrote in message

> I believe SPS means samples per second in this instance. I realize the
> difference is small when compared to the overall incident but it may be
> significant. It might be interesting to run whatever simulation you are
> running with both sets of data to see the difference.

There is also sample rate to consider. If the signal is sent at 12.5 Hz,
just because the most recent value for a parameter was sent at time X:XX.XX
doesn't mean that that's when the signals stopped. I also wonder if there
isn't some lag associated with packing/unpacking the signal into a standard
format for transmittal from the SRB data acquisition device to the orbiter.
Not sure about how the data flow works, there. That's one reason why I'd use
both the data and video. In any case, the last reported positions of the
actuators could very well be taken to be the positions at disintegration.
Both tilt and rock seemed to be changing at a similar rate in the final
fractions of a second. How far can the actuators move in a tenth of a
second? I don't know, but there's probably a value for that around
somewhere.

Jon

[Bob Jones]

"Charleston" > wrote in message news:<XNa2b.18455$cj1.18091@fed1read06>...
> >
> > which corresponds to 73.124 seconds MET.
>
> Interesting because a Range Safety Report document says that
>
> "Right SRB data on 25 SPS terminated at 73.093
> Left SRB data on 25 SPS terminated at 73.093
> ET data at 25 SPS terminated at 73.093"

Like what, the .02 second difference is enough time for a crossing in
the fireball?

Refer back to Jon's analysis of mass, motion, etc. to see that it's
impossible for a crossing to have happened in that amount of time.

Duh.

Bob

[Kent Betts]

"John Maxson" > wrote in message >...

John Maxson
> 'junk' argument, just for the sake of arguing.

John Maxson
>However,
> he will scrupulously avoid the evidence he cannot refute.

John Maxson
"You have no data from 51-L to provide...other than BS.
What you two have to offer are baseless allegations and
insidious interrogatory, designed to deflect and distort."

John Maxson
"How pathetic! How utterly pathetic!"

[jimmydevice]

Kent Betts wrote:

> "John Maxson" > wrote in message >...
ACK!!!!!

Greetings and hello!!!
Please do not feed or tap on the glass while observing the maxson.
The maxson feeds on supposition and innuendo and grows hostile when
presented with logical evidence. Please, Keep your hands in your
pockets and your tongue in your mouth. If you must speak while
observing the maxson exibit, please DO NOT say the following words:
CROSSING, BAND, SHUTTLE, SRB, MORON, KOOK
If a maxson attacks you during your visit, immediately use your
news readers "filter" mechanism. Most, if not all readers support
this function ( note: Not supported in MS Outlook and AOL )
This will protect you and allow you to enjoy the wild world of SSS.
Thank You and have a wonderful Day!!!

The staff of the maxson asylum.

[Alan Erskine]

Ken, either ignore JTM and the other nutcases from that family (his two
sons) or I will killfile you for a month.

--
Alan Erskine
alanerskine(at)optusnet.com.au
"This is a time to try men of force
and vision, and not be confined
exclusively to those who are judged
thoroughly safe by conventional standards."
Winston Churchill, October 19, 1940

"Kent Betts" > wrote in message
om...
> "John Maxson" > wrote in message
>...
>
> John Maxson
> > 'junk' argument, just for the sake of arguing.
>
> John Maxson
> >However,
> > he will scrupulously avoid the evidence he cannot refute.
>
> John Maxson
> "You have no data from 51-L to provide...other than BS.
> What you two have to offer are baseless allegations and
> insidious interrogatory, designed to deflect and distort."
>
> John Maxson
> "How pathetic! How utterly pathetic!"

[Kurt W. Wagner]

MS Outlook menubar>message>block sender seems to work to shield me from the
offensive. I prefer, however, to see the posts and simply ignore (or laugh
at) them.
Kurt

"jimmydevice" > wrote in message
...
> Kent Betts wrote:
>
> > "John Maxson" > wrote in message
>...
> ACK!!!!!
>
> Greetings and hello!!!
> Please do not feed or tap on the glass while observing the maxson.
> The maxson feeds on supposition and innuendo and grows hostile when
> presented with logical evidence. Please, Keep your hands in your
> pockets and your tongue in your mouth. If you must speak while
> observing the maxson exibit, please DO NOT say the following words:
> CROSSING, BAND, SHUTTLE, SRB, MORON, KOOK
> If a maxson attacks you during your visit, immediately use your
> news readers "filter" mechanism. Most, if not all readers support
> this function ( note: Not supported in MS Outlook and AOL )
> This will protect you and allow you to enjoy the wild world of SSS.
> Thank You and have a wonderful Day!!!
>
> The staff of the maxson asylum.
>

[Charleston]

"Jon Berndt" > wrote:
> "Charleston" > wrote:
>
> > I believe SPS means samples per second in this instance. I realize the
> > difference is small when compared to the overall incident but it may be
> > significant. It might be interesting to run whatever simulation you are
> > running with both sets of data to see the difference.
>
> There is also sample rate to consider. If the signal is sent at 12.5 Hz,
> just because the most recent value for a parameter was sent at time
X:XX.XX
> doesn't mean that that's when the signals stopped. I also wonder if there
> isn't some lag associated with packing/unpacking the signal into a
standard
> format for transmittal from the SRB data acquisition device to the
orbiter.

The time tags used by NASA throughout the five volumes of the Roger's report
are clearly described as the time relative to liftoff and therefore are
Mission Elapsed Time or MET. Please do not confuse others here about this
most basic "given" There is no magic there and you are just confusing the
issue.

> Not sure about how the data flow works, there. That's one reason why I'd
use
> both the data and video.

If you do not know how the data flows...?

Perhaps that is why NASA used a variety of sources for their information if
we can believe the Rogers Report which clearly indicates the source upon
which the time of each event is based.

> In any case, the last reported positions of the
> actuators could very well be taken to be the positions at disintegration.

That is an assumption with nothing to back it up since the vehicle
disentegrated only after the SRB data stopped. Whatever happened to the
SRBs' data happened simultaneously and preceded what NASA calls structural
break-up.

> Both tilt and rock seemed to be changing at a similar rate in the final
> fractions of a second. How far can the actuators move in a tenth of a
> second? I don't know, but there's probably a value for that around
> somewhere.

"Seemed to be changing" must be a new engineering term I am unfamiliar with.
Please elaborate. Can you provide any evidence as to what an SRB nozzle
position will be or do when it loses contact with the orbiter which has
control authority over the nozzles?

--

Daniel
Mount Charleston, not Charleston, SC

[Jon Berndt]

"Charleston" wrote:

> The time tags used by NASA throughout the five volumes of the Roger's
report
> are clearly described as the time relative to liftoff and therefore are
> Mission Elapsed Time or MET. Please do not confuse others here about this
> most basic "given" There is no magic there and you are just confusing the
> issue.

Two time standards are used in the PC Report, GMT and MET. MET is most
convenient to us, of course.

You may be missing my point, though. If an SRB Pc value (for instance) was
sampled at 12.5 Hz (every 0.080 seconds), for the *final* Pc value
*transmitted*, the time at which that data sample was taken doesn't
necessarily reflect the exact time at which telemetry ceased. The data could
cease to be transmitted perhaps because the SRBs comm to the stack was lost
(through the upper aft attachment strut), or the orbiter had detached. The
data could have ceased to be transmitted at either the time associated with
the last frame of data sent, or that time *plus* just under 0.080 seconds.
Also, there is a time lag between the time when the sensor data is acquired
and when the data is actually transmitted by the orbiter. I don't know how
big that lag is. What I was getting at is this: The last frame of data
associated with the SRBs (according to the PC Report) was sent at 73.124
seconds. However, that only means that SRB data acquisition (from both SRBs)
ceased working sometime between 73.124 seconds and 73.204 seconds (73.124 +
0.080). However, one also needs to consider that perhaps there was a, say,
0.04 second lag between when the frame (set) of data was sampled and when it
had been processed, packed, and transmitted from the orbiter. So, it is
conceivable that the communication paths in the stack were intact until (for
example) 73.244 seconds.

> That is an assumption with nothing to back it up since the vehicle
> disentegrated only after the SRB data stopped. Whatever happened to the
> SRBs' data happened simultaneously and preceded what NASA calls structural
> break-up.

Look at the data traces for the actuator positions. The traces show that the
SRBs were moving at the highest rate shown on the plot. They were trying to
arrest an unexpected roll that was still in progress (because of the
detached right SRB). It is likely that the nozzle continued to gimbal even
farther, but we do not know this for sure because the data link is lost. It
is likely that the SRB nozzle positions are even more extreme than shown,
and it was very shortly after this that they detached.

> Please elaborate. Can you provide any evidence as to what an SRB nozzle
> position will be or do when it loses contact with the orbiter which has
> control authority over the nozzles?

Sure. You can see that the left SRB (the undamaged one) is climbing out
fairly stable several seconds after it flies out of the propellant cloud,
with a few head-over heels manuevers. That means the nozzle is at or very
near its null position, with the end-over-end being due to neutral aero
stability. If it had stuck somewhere at a significant angle other than zero,
it would have been tumbling much more severely.

The *maximum* commanded rate of the SRB nozzle is hardware limited at 7
deg/sec.

Jon

[John Maxson]

Jon Berndt > wrote in message
...
> "Charleston" wrote:
> > The time tags used by NASA throughout the five volumes
> > of the Roger's report are clearly described as the time relative
> > to liftoff and therefore are Mission Elapsed Time or MET.
> > Please do not confuse others here about this most basic
> > "given" There is no magic there and you are just confusing
> > the issue.
>
> You may be missing my point, though. If an SRB Pc value
> (for instance) was sampled at 12.5 Hz (every 0.080 seconds),
> for the *final* Pc value *transmitted*, the time at which that
> data sample was taken doesn't necessarily reflect the exact time
> at which telemetry ceased. The data could cease to be transmitted
> perhaps because the SRBs comm to the stack was lost (through
> the upper aft attachment strut), or the orbiter had detached. The
> data could have ceased to be transmitted at either the time
> associated with the last frame of data sent, or that time *plus* just
> under 0.080 seconds. Also, there is a time lag between the time
> when the sensor data is acquired and when the data is actually
> transmitted by the orbiter.

Berndt, when it suited him:

"Anyhow, I think the timeline as stated in the Rogers'
Commission report is carefully reconstructed and the only
thing the lag Roger B. was referring to is germaine to is that
the Flight Controllers were six seconds behind in what they
saw"

--
John Thomas Maxson, Retired Engineer (Aerospace)
Author, The Betrayal of Mission 51-L (www.mission51l.com)