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Full Falcon 1.3 launch video up



 
 
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  #1  
Old August 7th 08, 04:10 PM posted to sci.space.policy
Damon Hill[_4_]
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Posts: 566
Default 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  
Old August 7th 08, 07:51 PM posted to sci.space.policy
Rick Jones
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Posts: 685
Default 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?"
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  #3  
Old August 7th 08, 09:16 PM posted to sci.space.policy
Jeff Findley
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Posts: 5,012
Default 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  
Old August 7th 08, 10:31 PM posted to sci.space.policy
Damon Hill[_4_]
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Posts: 566
Default 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  
Old August 7th 08, 10:41 PM posted to sci.space.policy
Rick Jones
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Posts: 685
Default 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  
Old August 7th 08, 11:33 PM posted to sci.space.policy
Jochem Huhmann
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Posts: 606
Default 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  
Old August 8th 08, 01:58 AM posted to sci.space.policy
Jorge R. Frank
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Posts: 2,089
Default 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  
Old August 8th 08, 02:00 AM posted to sci.space.policy
Jorge R. Frank
external usenet poster
 
Posts: 2,089
Default 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  
Old August 8th 08, 02:08 AM posted to sci.space.policy
Rick Jones
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Posts: 685
Default 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  
Old August 8th 08, 02:16 AM posted to sci.space.policy
Rick Jones
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Posts: 685
Default 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...
 




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