|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
Full Falcon 1.3 launch video up
The full video of the third launch is up on the Spacex site:
click on the takeoff picture in the launch report: http://www.spacex.com/updates.php The video quality is very good, showing a split screen of the rocketcam and a beautifully clear ground camera view of the liftoff. Stage separation is clearly shown and is pretty quick--too quick as it turned out. The lower stage firmly bumps the upper stage after about a second, which fires up almost immediatly right down into the interstage. This video cuts off at this point and is replaced by a brief segment of the upper stage fairing separating. The planned fix is to increase the 'dead' time before separation to allow the Merlin 1C engine to finish sputtering out. I assume they wanted a very short coasting time to minimize gravity losses, and won't implement first stage retro motors to enhance separation unless it becomes necessary. That decision might not be implemented for several flights if the next launch demonstrates a successful stage separation. I expect NO changes in the Merlin 1C; like most any turbopump liquid engine, it has shutdown transients as warm propellants vent, creating measurable thrust in vacuum. Will SpaceX fly again in the very near future? Seems likely, if their review doesn't turn up any other significant issues. They plan to launch a dummy payload so no customer payload will be at risk until there is a successful launch. I wouldn't be surprised if SpaceX launches two test flights; they need to demonstrate they have a reliable vehicle and to clear all remaining issues before declaring an operational capability. We'll see how it turns out. Exciting, isn't it? --Damon |
#2
|
|||
|
|||
Full Falcon 1.3 launch video up
Damon Hill wrote:
The full video of the third launch is up on the Spacex site: click on the takeoff picture in the launch report: http://www.spacex.com/updates.php Not sure if they are suffering from a mini slashdot effect - load time seems pretty long and I've not seen the video yet. Still, there was some interesting text in the update: http://www.spacex.com/updates.php#Update080608 "The question then is why didn't we catch this issue? Unfortunately, the engine chamber pressure is so low for this transient thrust -- only about 10 psi -- that it barely registered on our ground test stand in Texas where ambient pressure is 14.5 psi. However, in vacuum that 10 psi chamber pressure produced enough thrust to cause the first stage to recontact the second stage." "barely registered" implies that it _was_ seen in the ground testing. And perhaps dismissed? "As it turned out, a very small increase in the time between commanding main engine shutdown and stage separation would have been enough to save the mission." I'm just a lowly member of the peanut gallery, but everytime I see someone talking about waiting just a little longer I think about people using sleep() as a syncronization mechanism in a computer program. Is there no other way to be certain the stages are far enough apart before igniting the next stage? "The only untested portion of flight is whether or not we have solved the main problem of flight two, where the control system coupled with the slosh modes of the liquid oxygen tank." Strictly speaking is that true? Did they test payload separation? How about parachute recovery of the first stage? The planned fix is to increase the 'dead' time before separation to allow the Merlin 1C engine to finish sputtering out. I assume they wanted a very short coasting time to minimize gravity losses, Just how long _can_ one let things coast in these sorts of situations? Or does this: http://www.spacex.com/falcon1.php#second_stage "A single SpaceX Kestrel engine powers the Falcon 1 upper stage. A highly reliable and proven TEA-TEB pyrophoric system is used to provide multiple restart capability on the upper stage." imply that they can already restart after a long coast? I guess that brings-up another thing not yet flight tested - restart of the upper stage engine... We'll see how it turns out. Exciting, isn't it? Frustratingly so. rick jones -- The glass is neither half-empty nor half-full. The glass has a leak. The real question is "Can it be patched?" these opinions are mine, all mine; HP might not want them anyway... feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH... |
#3
|
|||
|
|||
Full Falcon 1.3 launch video up
"Rick Jones" wrote in message ... Damon Hill wrote: The full video of the third launch is up on the Spacex site: click on the takeoff picture in the launch report: http://www.spacex.com/updates.php Not sure if they are suffering from a mini slashdot effect - load time seems pretty long and I've not seen the video yet. Try this link: http://www.nasawatch.com/archives/20...ight.html#more Still, there was some interesting text in the update: http://www.spacex.com/updates.php#Update080608 "The question then is why didn't we catch this issue? Unfortunately, the engine chamber pressure is so low for this transient thrust -- only about 10 psi -- that it barely registered on our ground test stand in Texas where ambient pressure is 14.5 psi. However, in vacuum that 10 psi chamber pressure produced enough thrust to cause the first stage to recontact the second stage." "barely registered" implies that it _was_ seen in the ground testing. And perhaps dismissed? "As it turned out, a very small increase in the time between commanding main engine shutdown and stage separation would have been enough to save the mission." I'm just a lowly member of the peanut gallery, but everytime I see someone talking about waiting just a little longer I think about people using sleep() as a syncronization mechanism in a computer program. Is there no other way to be certain the stages are far enough apart before igniting the next stage? You could solve this with some sort of fancy sensor. Perhaps a space qualified laser range finder similar to the ones used for rendezvous and docking to ISS. But obviously this drives up the cost and is a lot more complex and prone to failure when compared to a simple timer. Jeff -- A clever person solves a problem. A wise person avoids it. -- Einstein |
#4
|
|||
|
|||
Full Falcon 1.3 launch video up
Rick Jones wrote in
: I'm just a lowly member of the peanut gallery, but everytime I see someone talking about waiting just a little longer I think about people using sleep() as a syncronization mechanism in a computer program. Is there no other way to be certain the stages are far enough apart before igniting the next stage? That's not exactly the problem--the separation impulse imparted by the pneumatic pusher/springs/whatever is supposed to do it. Here the first stage unexpectedly caught up with the second--it wasn't supposed to do that. And the fix will be simply to let the whole, unseparated, rocket coast a second or three longer before separation. They do know the separation mechanism works from the second flight, but in both cases misbehavior of the first stage caused unwanted post-separation contact which led to mission failure. Stay tuned, this drama may not be over yet...I certainly hope that the Merlin engine doesn't require modifications to minimize shutdown misbehavior. Strictly speaking is that true? Did they test payload separation? How about parachute recovery of the first stage? Apparently the payload separation mechanism was tested on the second flight and worked, despite tumbling. No joy on parachute recovery in any of the flights; this time the parachute apparently was toasted by the second stage engine "fire in the hole". I'm curious as to how recovery is going to be feasible with the engine having to endure splashdown impact and exposure to salt water... Initially I think SpaceX just wants to see how the system works in practice and to get some of the hardware back for post-flight analysis. Actual reuse may take some practice... The planned fix is to increase the 'dead' time before separation to allow the Merlin 1C engine to finish sputtering out. I assume they wanted a very short coasting time to minimize gravity losses, Just how long _can_ one let things coast in these sorts of situations? Or does this: I'd guess many seconds, but if the first stage engine cutoff roll torque and/or shutdown 'burp' causes rolling/tumbling, this could be an issue in safe separation and trajectory correction. I don't think the second stage RCS has the control authority to manage the whole stack. Adding a retro pack or RCS to the first stage seems counterproductive. The idea is to keep things as simple as possible. http://www.spacex.com/falcon1.php#second_stage "A single SpaceX Kestrel engine powers the Falcon 1 upper stage. A highly reliable and proven TEA-TEB pyrophoric system is used to provide multiple restart capability on the upper stage." imply that they can already restart after a long coast? Good question, could be slightly useful if the LOX boiloff and venting isn't an issue. --Damon |
#5
|
|||
|
|||
Full Falcon 1.3 launch video up
Jeff Findley wrote:
Try this link: http://www.nasawatch.com/archives/20...ight.html#more Fascinating typo on their part. I'm just a lowly member of the peanut gallery, but everytime I see someone talking about waiting just a little longer I think about people using sleep() as a syncronization mechanism in a computer program. Is there no other way to be certain the stages are far enough apart before igniting the next stage? You could solve this with some sort of fancy sensor. Perhaps a space qualified laser range finder similar to the ones used for rendezvous and docking to ISS. But obviously this drives up the cost and is a lot more complex and prone to failure when compared to a simple timer. After I thought about it a little more I realized there is still the issue of just what the heck one does when the sensor says "stages too close" - presumably you try to push away harder, but in that case, might as well push away that hard in the first place I should think, unless I'm missing something. rick jones -- portable adj, code that compiles under more than one compiler these opinions are mine, all mine; HP might not want them anyway... feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH... |
#6
|
|||
|
|||
Full Falcon 1.3 launch video up
"Jeff Findley" writes:
I'm just a lowly member of the peanut gallery, but everytime I see someone talking about waiting just a little longer I think about people using sleep() as a syncronization mechanism in a computer program. Is there no other way to be certain the stages are far enough apart before igniting the next stage? You could solve this with some sort of fancy sensor. Perhaps a space qualified laser range finder similar to the ones used for rendezvous and docking to ISS. But obviously this drives up the cost and is a lot more complex and prone to failure when compared to a simple timer. Put a length of thin wire between the stages and don't fire the upper stage engine as long as this wire hasn't snapped. The russian method of avoiding instead of solving this problem by connecting the stages with a lattice structure and igniting the second stage before separation seems better, though... Jochem -- "A designer knows he has arrived at perfection not when there is no longer anything to add, but when there is no longer anything to take away." - Antoine de Saint-Exupery |
#7
|
|||
|
|||
Full Falcon 1.3 launch video up
Rick Jones wrote:
Damon Hill wrote: The full video of the third launch is up on the Spacex site: click on the takeoff picture in the launch report: http://www.spacex.com/updates.php Not sure if they are suffering from a mini slashdot effect - load time seems pretty long and I've not seen the video yet. Still, there was some interesting text in the update: http://www.spacex.com/updates.php#Update080608 "The question then is why didn't we catch this issue? Unfortunately, the engine chamber pressure is so low for this transient thrust -- only about 10 psi -- that it barely registered on our ground test stand in Texas where ambient pressure is 14.5 psi. However, in vacuum that 10 psi chamber pressure produced enough thrust to cause the first stage to recontact the second stage." "barely registered" implies that it _was_ seen in the ground testing. And perhaps dismissed? I believe there was an earlier report stating it was seen on the test stand. Don't know if I would classify it as "dismissed" based on the little I know. "As it turned out, a very small increase in the time between commanding main engine shutdown and stage separation would have been enough to save the mission." I'm just a lowly member of the peanut gallery, but everytime I see someone talking about waiting just a little longer I think about people using sleep() as a syncronization mechanism in a computer program. Not quite - the GNC software is still cycling through and doing all its other computations; typically they either put a countdown timer in the loop, or schedule a separate task to kick off at the appropriate time. Is there no other way to be certain the stages are far enough apart before igniting the next stage? There are other ways, but a timer is the simplest and least prone to other failures. (e.g. if you use a sensor, what does the software fall back on if the sensor fails?) The planned fix is to increase the 'dead' time before separation to allow the Merlin 1C engine to finish sputtering out. I assume they wanted a very short coasting time to minimize gravity losses, Just how long _can_ one let things coast in these sorts of situations? Depends on the rocket (in particular, the conditions at staging), but I've heard some other rockets wait as long as eight seconds. Can't find my source at the moment. The concern is not just gravity loss but also controllability. Or does this: http://www.spacex.com/falcon1.php#second_stage "A single SpaceX Kestrel engine powers the Falcon 1 upper stage. A highly reliable and proven TEA-TEB pyrophoric system is used to provide multiple restart capability on the upper stage." imply that they can already restart after a long coast? The firing after staging is the first start, not a restart. |
#8
|
|||
|
|||
Full Falcon 1.3 launch video up
Jochem Huhmann wrote:
"Jeff Findley" writes: I'm just a lowly member of the peanut gallery, but everytime I see someone talking about waiting just a little longer I think about people using sleep() as a syncronization mechanism in a computer program. Is there no other way to be certain the stages are far enough apart before igniting the next stage? You could solve this with some sort of fancy sensor. Perhaps a space qualified laser range finder similar to the ones used for rendezvous and docking to ISS. But obviously this drives up the cost and is a lot more complex and prone to failure when compared to a simple timer. Put a length of thin wire between the stages and don't fire the upper stage engine as long as this wire hasn't snapped. The russian method of avoiding instead of solving this problem by connecting the stages with a lattice structure and igniting the second stage before separation seems better, though... Fine for expendables, but Musk has higher goals. |
#9
|
|||
|
|||
Full Falcon 1.3 launch video up
Jochem Huhmann wrote:
Put a length of thin wire between the stages and don't fire the upper stage engine as long as this wire hasn't snapped. What does one program the stage(s) to do when the wire hasn't snapped after N units of time? rick jones -- web2.0 n, the dot.com reunion tour... these opinions are mine, all mine; HP might not want them anyway... feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH... |
#10
|
|||
|
|||
Full Falcon 1.3 launch video up
Jorge R. Frank wrote:
Rick Jones wrote: Or does this: http://www.spacex.com/falcon1.php#second_stage "A single SpaceX Kestrel engine powers the Falcon 1 upper stage. A highly reliable and proven TEA-TEB pyrophoric system is used to provide multiple restart capability on the upper stage." imply that they can already restart after a long coast? The firing after staging is the first start, not a restart. I am afraid I'm not grasping the distinction. Coasting is coasting isn't it? rick jones -- oxymoron n, commuter in a gas-guzzling luxury SUV with an American flag these opinions are mine, all mine; HP might not want them anyway... feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH... |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Falcon 1 launch video | Pat Flannery | History | 32 | August 9th 08 03:40 PM |
Falcon launch delayed again | Pat Flannery | History | 2 | February 9th 07 04:33 PM |
Live from Omelek (live video of Falcon 1 launch) | Damon Hill | History | 3 | March 25th 06 01:58 AM |
Full dome video or good Fisheye images | Ricardo | Misc | 0 | December 31st 05 05:29 AM |
Saturday Falcon 1 launch and weather? | Neil Halelamien | Policy | 37 | December 2nd 05 05:44 PM |