Full Falcon 1.3 launch video up

Rick Jones wrote in news:g7g6p1$c2i$4
@usenet01.boi.hp.com:

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?

Context: we're discussing the first ignition of the upper stage, after
stage separation. The planned separation occured but was compromised
by the unanticipated acceleration of the first stage, which subsequently
rammed the second stage.

THAT WAS NOT SUPPOSED TO HAPPEN UNDER ANY CIRCUMSTANCE. Collisions are
bad, okay?

ONCE AGAIN: the "fix" is to let the rocket coast long enough for the
first stage engine to finish sputtering out, and with it, any residual
acceleration. Then normal staging occurs, the second stage moves away
to a safe distance and the second stage engine fires.

What's not to understand?

--Damon

Rick Jones wrote:

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?

They shouldn't have had to rely on detecting transients on the test
stand - this is something that should have been calculated from
analysis of the shutdown.

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

http://derekl1963.livejournal.com/

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

"Jeff Findley" wrote:

:
:"Rick Jones" wrote in message
...
:
: 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.
:

Surely you wouldn't need anything that fancy, would you? I'd think a
simple lanyard would be sufficient. Make it long enough so that if it
gets pulled (or have a wire that breaks) you know the trailing stage
is far enough away so that it won't be "catching up".

It's really kind of scary that all this is done by simple timers. I
would think even cheap accelerometers would give you much better
assurance that the stage was actually separated.

--
"Insisting on perfect safety is for people who don't have the balls to
live in the real world." -- Mary Shafer, NASA Dryden

Rick Jones wrote:

: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?
:

You use redundant wires. If *none* of them show as having snapped,
then you do whatever you do for an absolute separation failure.

--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn

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?


How about watching the accelleration of the rocket (i.e. the first stage
engine)? If it stops accellerating or starts to deccellerate then you start
the seperation procedure and ignite the second stage after an x amount of
time (2 seconds) to allow the stages to drift apart.


** Posted from http://www.teranews.com **

"Dale Harris" wrote:

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?


How about watching the accelleration of the rocket (i.e. the first stage
engine)? If it stops accellerating or starts to deccellerate then you start
the seperation procedure and ignite the second stage after an x amount of
time (2 seconds) to allow the stages to drift apart.

Works fine for solids. Sucks rocks for liquids which you typically
want to shut down in a more controlled fashion.

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

http://derekl1963.livejournal.com/

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

"Derek Lyons" wrote in message
...
"Dale Harris" wrote:

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?


How about watching the accelleration of the rocket (i.e. the first stage
engine)? If it stops accellerating or starts to deccellerate then you
start
the seperation procedure and ignite the second stage after an x amount of
time (2 seconds) to allow the stages to drift apart.

Works fine for solids. Sucks rocks for liquids which you typically
want to shut down in a more controlled fashion.

You would obviously first send a control signal to the liquid engine to shut
down and then follow the above procedure.


** Posted from http://www.teranews.com **

In message
Rick Jones wrote:

"barely registered" implies that it _was_ seen in the ground testing.
And perhaps dismissed?

No, allowed for in the delay that *was* set in the procedure, which
turned out to be not quite long enough.

Is there no other way to be certain the stages are far
enough apart before igniting the next stage?

Nothing to do with how long you wait for ignition, it's how long you
wait after main engine shutdown before seperating the stages.

Strictly speaking is that true? Did they test payload separation?

Payload separation worked on flight 2.

Anthony

Jochem Huhmann wrote:
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...


They have another neat idea on the Proton third stage; when it fires up
its four external vernier/trajectory control engines towards the end of
second stage burn, their exhaust burns through wiring mounted just below
them that causes the second stage to shut down.
At least I assume it's wiring... the translation I read of this
described it as "plumbing", but that seems a little too odd to do.

Pat

"Fred J. McCall" wrote in message
...

Surely you wouldn't need anything that fancy, would you? I'd think a
simple lanyard would be sufficient. Make it long enough so that if it
gets pulled (or have a wire that breaks) you know the trailing stage
is far enough away so that it won't be "catching up".

That would be a simple solution.

It's really kind of scary that all this is done by simple timers. I
would think even cheap accelerometers would give you much better
assurance that the stage was actually separated.

True. Without talking to the engineers involved it's hard to say what their
overall design philosophy is for stage separation. I'm not sure I like
their combination of a regen first stage engine with pneumatic cylinders (I
think that's what I read) to separate the stages.

Jeff
--
A clever person solves a problem.
A wise person avoids it. -- Einstein