Full Falcon 1.3 launch video up

"Dale Harris" wrote:

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

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.

If you do that, you don't need accelerometers or wires or rangefinders
or other complicated **** - a simple timer works just fine.

Keep in mind the Falcon was lost because SpaceX ****ed up their
design, not because of an unexpected and/or unknown basic problem.

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

http://derekl1963.livejournal.com/

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

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?


Release Scotty's ashes so that his magic can fix the problem I think. :-D

Pat

On Aug 8, 6:52*am, "Jeff Findley" wrote:
"Fred J. McCall" wrote in messagenews:1mhn94dlnpoe03hvclk3hhm8ht0sprnkf4@4ax .com...



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.

That's what Delta has done forever. It works fine, SpaceX just needed
to wait until the shutdown transient finished. According to its
payload planners guide, the Delta II (and Delta IV, and Atlas IV)
waits 8 seconds from MECO to separation; the Falcon waited 1.5
seconds.

-jake

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?

I'm probably not wording things well. I was initially asking if there
would be a problem with starting the second stage engine after a
"long" coast. I noticed that the second stage engine is supposed to
be restartable, so I was asking if the functionality they have there
to enable restart (which would be ostensibly after a coast) meant that
there was also then no real issue with the initial start after a
coast.

I am not sure how you read my thinking that collisions were OK into
that, but if you did, that isn't what I was trying to ask.

rick jones
--
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feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH...

Rick Jones wrote in
:


I'm probably not wording things well. I was initially asking if there
would be a problem with starting the second stage engine after a
"long" coast. I noticed that the second stage engine is supposed to
be restartable, so I was asking if the functionality they have there
to enable restart (which would be ostensibly after a coast) meant that
there was also then no real issue with the initial start after a
coast.

The only issue with the initial start is gravity losses; a significantly
delayed start results in payload loss as the stage's trajectory falls.
A delay of more than a few seconds begins to eat into that margin, which
is presumably why SpaceX attempted to make staging so quickly.

Must be some interesting plumbing issues to prevent bubbles forming
in the liquid oxygen lines to the pressure-fed engine. That's a
potential problem with any cryogenic propellant. I don't know how
SpaceX handles it in the Kestrel design, but there's certainly an
upper limit in coast time (tens of minutes to a couple of hours?)
before loss of oxidizer ends a useful mission.

--Damon

wrote:
I believe they have said this was an ~ 10 psia cooling
passage/chamber pressure as seen in flight. Given the ground test
has an atmospheric pressure of 14.7 psia imposed on it, please
illuminate us on the fluid mechanic/gas dynamic situation where this
would be seen in a ground test of the engine system.

FWIW, Elon Musk's words as presented in:

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. "

I only ever spun backup tapes for fluid dynamicists, so have no
concrete idea how it could have been seen, but that is what the
wording from SpaceX seems to imply.

How quickly after the engine stops, and the exhaust pushing against (?
out?) atmosphere is no longer being replenished, before atmosphere
will get back into the chamber at ambient pressure? Might there be
enough momentum in the exhaust to allow a sub-atmospheric condition in
the thrust chamber?

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...

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

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?

Damn right.

I'll take a Falcon 1 failure over an Ares I non starter any time.

Quoting Carl Sagan : $Billions and $Billions!