Video coverage sure has improved.

My favorite new camera is the ET cam, amazing watching the plasma coming
off the Tank and Orbiter before and after MECO. The RCS jet firings and +x
manuver post MECO too. The roll after liftoff with overshoot is pretty
dramatic, with the Cape below. SRB Sep, and the roll to heads up
great shots.

http://mfile.akamai.com/18565/rm/eto...s121_etcam.ram

http://anon.nasa-global.edgesuite.ne...ep_cc_real.ram

Now if they can just figure out how to keep the moisture off the lens.

--
Craig Fink
Courtesy E-Mail Welcome @

Craig Fink wrote:
My favorite new camera is the ET cam, amazing watching the plasma coming
off the Tank and Orbiter before and after MECO. The RCS jet firings and +x
manuver post MECO too. The roll after liftoff with overshoot is pretty
dramatic, with the Cape below. SRB Sep, and the roll to heads up
great shots.

http://mfile.akamai.com/18565/rm/eto...s121_etcam.ram

http://anon.nasa-global.edgesuite.ne...ep_cc_real.ram

Now if they can just figure out how to keep the moisture off the lens.

--
Craig Fink
Courtesy E-Mail Welcome @

WOW, I have neever seen (or perhaps noticed) the overshoot during roll
program. Does anyone know if this is common or why it happens?
Although I never gave it a lot of thought and given the precision of
guidance needed to hit the desired orbital targets, I would have
thought the guidance would be solid enough to nail the desired amount
of roll without overshooting. Is guidance in a"brute force" mode
during the early part of ascent? Also, the PAO noted after SRB sep
that the guidance was converging. What process is taking place?

Thanks in advance and blue skies to you all

John

On Fri, 07 Jul 2006 06:41:33 -0700, John wrote:


Craig Fink wrote:
My favorite new camera is the ET cam, amazing watching the plasma coming
off the Tank and Orbiter before and after MECO. The RCS jet firings and +x
manuver post MECO too. The roll after liftoff with overshoot is pretty
dramatic, with the Cape below. SRB Sep, and the roll to heads up
great shots.

http://mfile.akamai.com/18565/rm/eto...s121_etcam.ram

http://anon.nasa-global.edgesuite.ne...ep_cc_real.ram

Now if they can just figure out how to keep the moisture off the lens.

--
Craig Fink
Courtesy E-Mail Welcome @

WOW, I have neever seen (or perhaps noticed) the overshoot during roll
program. Does anyone know if this is common or why it happens?
Although I never gave it a lot of thought and given the precision of
guidance needed to hit the desired orbital targets, I would have
thought the guidance would be solid enough to nail the desired amount
of roll without overshooting. Is guidance in a"brute force" mode
during the early part of ascent? Also, the PAO noted after SRB sep
that the guidance was converging. What process is taking place?

Thanks in advance and blue skies to you all


It does it every time, it just not as noticeable from cameras on the
ground. The perspective of the on board camera really brings it out, as
it's the ground that is doing the moving instead of the vehicle.

Really, there is no "Roll Program", what occurs after tower clear is a
step function in the guidance commands. From an attitude hold, pointed
straight up, to what should be the final pitch, yaw and 180 degree roll
headed down attitude. So, guidance commands a completely different
attitude, and the flight control maneuvers the stack at maximum rates to
get it there. Really saturated in roll. From control theory, the quickest
way to get from on state to another is to overshoot slightly.

I wish NASA had included the second stage roll to heads up in the ET cam
footage. The "Engineering" footage had this shot in it, but it wasn't
included in the archive footage.

After SRB sep, second stage guidance called "PEG" kicks in. It runs once
every two seconds computing what the current attitude needs to be
right now to hit the MECO targets later in flight. It takes several
iterations to converge on a correct solution, with each pass being a
better than the last.

--
Craig Fink
Courtesy E-Mail Welcome @

Craig Fink wrote:
On Fri, 07 Jul 2006 06:41:33 -0700, John wrote:


Craig Fink wrote:
My favorite new camera is the ET cam, amazing watching the plasma coming
off the Tank and Orbiter before and after MECO. The RCS jet firings and +x
manuver post MECO too. The roll after liftoff with overshoot is pretty
dramatic, with the Cape below. SRB Sep, and the roll to heads up
great shots.

http://mfile.akamai.com/18565/rm/eto...s121_etcam.ram

http://anon.nasa-global.edgesuite.ne...ep_cc_real.ram

Now if they can just figure out how to keep the moisture off the lens.

--
Craig Fink
Courtesy E-Mail Welcome @

WOW, I have neever seen (or perhaps noticed) the overshoot during roll
program. Does anyone know if this is common or why it happens?
Although I never gave it a lot of thought and given the precision of
guidance needed to hit the desired orbital targets, I would have
thought the guidance would be solid enough to nail the desired amount
of roll without overshooting. Is guidance in a"brute force" mode
during the early part of ascent? Also, the PAO noted after SRB sep
that the guidance was converging. What process is taking place?

Thanks in advance and blue skies to you all


It does it every time, it just not as noticeable from cameras on the
ground. The perspective of the on board camera really brings it out, as
it's the ground that is doing the moving instead of the vehicle.

Really, there is no "Roll Program", what occurs after tower clear is a
step function in the guidance commands. From an attitude hold, pointed
straight up, to what should be the final pitch, yaw and 180 degree roll
headed down attitude. So, guidance commands a completely different
attitude, and the flight control maneuvers the stack at maximum rates to
get it there. Really saturated in roll. From control theory, the quickest
way to get from on state to another is to overshoot slightly.

I wish NASA had included the second stage roll to heads up in the ET cam
footage. The "Engineering" footage had this shot in it, but it wasn't
included in the archive footage.

After SRB sep, second stage guidance called "PEG" kicks in. It runs once
every two seconds computing what the current attitude needs to be
right now to hit the MECO targets later in flight. It takes several
iterations to converge on a correct solution, with each pass being a
better than the last.

--
Craig Fink
Courtesy E-Mail Welcome @

Thank you Craig, great answer. This is an example of why I enjoy this
group so much, despite the Signal to Noise Ratio :)

Blue skies

John

"John" wrote:
WOW, I have neever seen (or perhaps noticed) the overshoot during roll
program. Does anyone know if this is common or why it happens?
Although I never gave it a lot of thought and given the precision of
guidance needed to hit the desired orbital targets, I would have
thought the guidance would be solid enough to nail the desired amount
of roll without overshooting. Is guidance in a"brute force" mode
during the early part of ascent?

Yes - it's far more concerned with managing aerodynamic loads than
hitting it's orbital parameters at that point. Roll control, while
important for managing those loads - is the least important term for
hitting your orbital target. Those parameters are *EXTREMELY*
sensitive to pitch and yaw - and virtually not at all to roll.[1]

Also, the PAO noted after SRB sep that the guidance was converging.
What process is taking place?

As I said above, during the early part of the ascent - the emphasis is
on managing aerodynamic loads on the airframe.[2] This almost
certainly deviates from the 'ideal' trajectory for reaching a desired
orbital target. Generally you want to ascend more-or-less straight up
to get out of the atmosphere (and minimize drag) during the early
portion of the launch - but obtaining orbital velocity actually means
you need to thrust more-or-less parallel to the earths surface.

Thus, once above the sensible atmosphere, you can start steering your
velocity vector[3] from where your aerodynamic steering profile left
it, towards the 'ideal' trajectory - this process is called
convergence.

[1] Though roll may effect your ability to steer in those planes - it
doesn't actually appear in the idealized ballistic equations.

[2] Even traditional (I.E. cylindrical) rockets have to worry about
this to some degree. You can here the same call during Apollo
liftoffs for example.

[3] An important concept to note: What you are managing is the
spacecrafts velocity in various axes - not the spacecrafts actual
position. The neat little diagrams on the wall of the MCC and in
various books, etc... lead you to incorrectly believe the opposite.

D.
--
Touch-twice life. Eat. Drink. Laugh.

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL

NASA-TV replayed footage from ET-207 (Playalinda Beach DOAMS) which is
the camera your talking about. In Addition, NASA-TV also showed footage
from ET207-1 which was the same angle but with a wider shot.

http://www.youtube.com/watch?v=VKEcSryENu8

-Dusty


snidely wrote:
What I really liked, though, was the fantastic shots of the engine
bells just before Max Q and just after "Go for throttle up". In the
other thread, Dusty said they were UCS-10, but the Sep 2004 RTF imaging
doc shows UCS-10 being deleted, and it is a film camera anyway. That
doc shows the HD cameras at North Beach (EH222), UCS-5 (EH224), UCS-9
(EH225), and UCS-15 (EH220). Long-range trackers are shown at UCS-3
(EH214), D5R67 (EH216), Ponce Inlet (EH211) and Apollo Beach (EH217).

/dps

Dusty wrote:
NASA-TV replayed footage from ET-207 (Playalinda Beach DOAMS) which is
the camera your talking about. In Addition, NASA-TV also showed footage
from ET207-1 which was the same angle but with a wider shot.

http://www.youtube.com/watch?v=VKEcSryENu8



Beautiful -- that's it! Thanks for the link!

/dps