LIVE: SpaceX - Falcon I (Mk.II) NET March 20 (Attempt 2)

[marsavian]

Mike should have asked Scott to cross his digits too ;-)

http://www.space.com/missionlaunches/070320_spacex_falc1_test2.html

[meiza]

Cheap COTS would help NASA hugely budget-wise...

[Danderman]

FWIW, the SpaceX launch manifest has been updated to show the next launch for NRL at Q3.  The two prior tests have been dropped from the manifest, so it may be that this is an up-to-date manifest.

[ETEE]

Sky News (for the discerning British viewers) just ran the SpaceX launch.  Unbelieveable if you knew Sky News is usually more interested in Who Killed Diana!

[edkyle99]

Greg Zsidisin has analyzed the video and has determined what went wrong, at SpaceDaily.  :/

"Falcon 1 Video Suggests Stage Collision"

http://www.spacedaily.com/reports/Falcon_1_Video_Suggests_Stage_Collision_999.html

 - Ed Kyle

[Captain Scarlet]

ETEE - 22/3/2007  3:23 PM

Sky News (for the discerning British viewers) just ran the SpaceX launch.  Unbelieveable if you knew Sky News is usually more interested in Who Killed Diana!

Rubbish.
Sky News covers nearly every launch, from Shuttle (extensive) to even Atlas launches. They always have an interest in space flight.

[Jim]

Real experts suggest a slowly blossoming limit cycle present on both the yaw channel and the pitch channels, which lead to coning and propellant sloshing

[kevin-rf]

Jim - 22/3/2007  10:56 AM

Real experts suggest a slowly blossoming limit cycle present on both the yaw channel and the pitch channels, which lead to coning and propellant sloshing

And the 360 degree roll was caused by? Stuck RCS thruster?

The extra 15 seconds on the youtube vid is very interesting as it does a full roll then cuts off.

I wonder if there was a software issue where it would terminate the flight if it rolled more than 360 degrees. You know a roll over error ;-)

[ETEE]

Captain Scarlet - 22/3/2007  4:55 PM

ETEE - 22/3/2007  3:23 PM

Sky News (for the discerning British viewers) just ran the SpaceX launch.  Unbelieveable if you knew Sky News is usually more interested in Who Killed Diana!

Rubbish.
Sky News covers nearly every launch, from Shuttle (extensive) to even Atlas launches. They always have an interest in space flight.

Must be a different Sky News from the one I see then

[Jim]

kevin-rf - 22/3/2007  12:33 PM

Jim - 22/3/2007  10:56 AM

Real experts suggest a slowly blossoming limit cycle present on both the yaw channel and the pitch channels, which lead to coning and propellant sloshing

And the 360 degree roll was caused by? Stuck RCS thruster?

The extra 15 seconds on the youtube vid is very interesting as it does a full roll then cuts off.

I wonder if there was a software issue where it would terminate the flight if it rolled more than 360 degrees. You know a roll over error ;-)

Cross coupling.  tumble check could have saved the mission, shut down the engine, null rates and restart

[edkyle99]

kevin-rf - 22/3/2007  11:33 AM

Jim - 22/3/2007  10:56 AM

Real experts suggest a slowly blossoming limit cycle present on both the yaw channel and the pitch channels, which lead to coning and propellant sloshing

And the 360 degree roll was caused by? Stuck RCS thruster?

The extra 15 seconds on the youtube vid is very interesting as it does a full roll then cuts off.

I wonder if there was a software issue where it would terminate the flight if it rolled more than 360 degrees. You know a roll over error ;-)

I'm guessing here, but one possibility is that the attitude control system ran out of helium, since it would have been "firing" constantly to correct for the unplanned coning motion.  Another possibility is that the motion simply grew too large for the attitude control system to correct.

 - Ed Kyle

[imcub]

Jim - 22/3/2007  8:56 AM

Real experts suggest a slowly blossoming limit cycle present on both the yaw channel and the pitch channels, which lead to coning and propellant sloshing

Coning?  Would this be a controller induced 'wobble' in the spacecraft where the nose makes wider and wider circles about the flight path ...

Thanks.

[Zond]

Does anybody know what the black blocks on top of the interstage that are visible in the T+00:02:52 picture are? Are they simply connectors or are they part of the stage release mechanism? If they are part of the stage reales mechanism, the direction of travel of the second stage would suggest that the third release mechanism lagged the two that are visible.

[Jim]

edkyle99 - 22/3/2007  12:58 PM

kevin-rf - 22/3/2007  11:33 AM

Jim - 22/3/2007  10:56 AM

Real experts suggest a slowly blossoming limit cycle present on both the yaw channel and the pitch channels, which lead to coning and propellant sloshing

And the 360 degree roll was caused by? Stuck RCS thruster?

The extra 15 seconds on the youtube vid is very interesting as it does a full roll then cuts off.

I wonder if there was a software issue where it would terminate the flight if it rolled more than 360 degrees. You know a roll over error ;-)

I'm guessing here, but one possibility is that the attitude control system ran out of helium, since it would have been "firing" constantly to correct for the unplanned coning motion.  Another possibility is that the motion simply grew too large for the attitude control system to correct.

 - Ed Kyle

Usually,  only roll control is active during the engine burn with pitch and yeaw actuators providing TVC.  The pitch and yaw thrusters are disabled

[lbiderman]

From your experience Jim, do you believe fixing this second stage problem is too costly? Of course it depends of the failure type, but I imagine you already have your theory on that.

[edkyle99]

Jim - 22/3/2007  12:11 PM

edkyle99 - 22/3/2007  12:58 PM
I'm guessing here, but one possibility is that the attitude control system ran out of helium, since it would have been "firing" constantly to correct for the unplanned coning motion.  Another possibility is that the motion simply grew too large for the attitude control system to correct.

 - Ed Kyle

Usually,  only roll control is active during the engine burn with pitch and yeaw actuators providing TVC.  The pitch and yaw thrusters are disabled

Right, but wouldn't the coning/propellant sloshing motion have induced some roll moment too (probably an oscillating moment due to sloshing) that would have had to be countered?  (I'm sloshing my Diet Pepsi (TM) right now, and it sure feels like some roll torque is  being induced.)

 - Ed Kyle

[blueguitarbob]

For those that want to know more about POGO:

http://www.engineeringatboeing.com/articles/pogo.htm

This might be a little _more_ than you want to know about the subject... but it's good reading, anyway.

[aero313]

lbiderman - 22/3/2007  1:32 PM

From your experience Jim, do you believe fixing this second stage problem is too costly? Of course it depends of the failure type, but I imagine you already have your theory on that.

I'll jump in and offer that if the problem is simply gains in the control system, the fix is easy.  The VALIDATION that the fix is correct is the hard part.

"...But it worked in the simulation..."

[JIS]

hyper_snyper - 21/3/2007  10:22 PM

I'd venture so far as to say F1 won't be flying nearly as much as soon as F9/Dragon gets up and running.  Maybe the occasional small sat, but F9 is the meat and potatoes of what SpaceX is trying to do.

Agree

[Tschachim]

blueguitarbob - 22/3/2007  9:35 PM
For those that want to know more about POGO:
http://www.engineeringatboeing.com/articles/pogo.htm

I'm absolutely not the expert here, but it doesn't look like pogo for me. Pogo are lengthwise oscillations, typically around 10 Hz, in the video I see divergent pitch and yaw oscillations and the roll motion at the very end of the video, I also suspect that the roll control cannot countersteer the roll motion anymore, which is probably induced by coupling of the pitch and yaw motion, or the roll control just failed.

But I also wonder what caused these pitch and yaw oscillations. Resonances in the guidance loop sound silly for me nowadays, perhaps the experts around here can enlighten me?  

Cheers
Tschachim