yinzer - 23/3/2007 11:18 PMThat is almost certainly false - in order to be space debris, it would have had to reach orbital velocity. It looked to be in serious trouble when control was lost, and still had four minutes left to burn.
JonSBerndt - 23/3/2007 1:23 PMThe point remains: was there a pitch or yaw acceleration at sep, and if so, what caused it?Jon
DaveS - 23/3/2007 6:44 PMQuoteyinzer - 23/3/2007 11:18 PMThat is almost certainly false - in order to be space debris, it would have had to reach orbital velocity. It looked to be in serious trouble when control was lost, and still had four minutes left to burn.It's false alright. Elon did state that it at most travelled half an orbit before falling back to Earth and disintegrated.
Avron - 23/3/2007 6:53 PMHow do you prevent fuel from sloshing in the tanks?What must be done to the control system to prevent the motion we saw before video cutoff.. is it a simple gain control in the system?
Antares - 23/3/2007 7:15 PMQuoteAvron - 23/3/2007 6:53 PMHow do you prevent fuel from sloshing in the tanks?What must be done to the control system to prevent the motion we saw before video cutoff.. is it a simple gain control in the system?Google slosh baffles. They are metal plates or rings inside rocket tanks (on the r-theta plane) that damp liquid motion. Slosh modeling is one of the most complicated aspects of flight control and propellant management. Recall it delayed the Delta IV L-22 launch, though that was more thermal than flight control. Modeling fidelity is key. Subtle changes in input can cause huge changes in output.
Avron - 23/3/2007 6:24 PMWould Spacex have no baffles, that would be crazy .. yes? or did the existing baffles not have enought "area" to control the slosh that must have been created from the "interesting" stage event?
Jim - 23/3/2007 7:05 PMQuoteJonSBerndt - 23/3/2007 1:23 PMIt does have them, in a fashion (see: http://www.spacex.com/falcon1.php#second_stage):"Helium pressurization is again provided by composite over wrapped inconel tanks from Arde. However, in this case the helium is also used in cold gas thrusters for attitude control and propellant settling when a restart is needed."It's not clear by the wording above if second stage ignition (the first time) uses the thrusters for propellant settling. This is the part where I am not clear on whether or not they are needed for the initial ignition.The point remains: was there a pitch or yaw acceleration at sep, and if so, what caused it?JonThey don't have ullage MOTORS, i.e. not solids. All upperstages have aft facing thrusters for ullage control for restarts. But these and most RCS systems are not used during staging since the other forces present (aero, ordnance, spring, etc) are much larger and overwhelm them. LV's rely on the upperstage engine TVC to correct the errors. Much like what was seen on this launch
JonSBerndt - 23/3/2007 1:23 PMIt does have them, in a fashion (see: http://www.spacex.com/falcon1.php#second_stage):"Helium pressurization is again provided by composite over wrapped inconel tanks from Arde. However, in this case the helium is also used in cold gas thrusters for attitude control and propellant settling when a restart is needed."It's not clear by the wording above if second stage ignition (the first time) uses the thrusters for propellant settling. This is the part where I am not clear on whether or not they are needed for the initial ignition.The point remains: was there a pitch or yaw acceleration at sep, and if so, what caused it?Jon
meiza - 24/3/2007 12:54 PMSo, Falcon I staging goes like this?:1. main engine shutdown2. mechanical unlock of second stage, springs push it forwards and the engine bell comes out of the interstage3. the second stage is now separate and practically weightless, it's ullage thrusters fire (the helium ones) to settle the propellant4. the second stage engine lights and aligns the stage right by gimballing the main engine-roll control is achieved by cold gas thrusters too. It is unclear at what point roll control starts to function, probably at 4.
Chris Bergin - 24/3/2007 9:58 PMBeen speaking to Elon and there's an article coming in about an hour with the latest (lots of new info - lots of positives).
halkey - 25/3/2007 3:46 AMWill that be L2 exclusive info or will us moochers on the free site be able to read it also?
Chris Bergin - 24/3/2007 11:20 PMOn site: http://www.nasaspaceflight.com/content/?cid=5056
JonSBerndt - 23/3/2007 6:23 PMThe point remains: was there a pitch or yaw acceleration at sep, and if so, what caused it?Jon
