Falcon 1 Staging Recontact - Engine Burp

Likkle vernier rockets pointing upwards?

Brian

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"Alan Erskine" wrote in message
...
"richard schumacher" wrote in message
...

Or something as simple as thrust created by gas exhausting from the
(new) cooling system. Geez Louise. Does Falcon 1 use anything other
than explosive bolts and springs for stage separation? How many more
basic errors can they afford to re-discover?

Other than the two mentioned, what can be used for stage sep?

Alan Erskine wrote:
One word for both Pat and Derek on this: mass. Surely a shaped charge, even
a small one,

No, it need not be heavy at all, just a thin strip of Det Cord in a
housing to focus the blast somewhat.
Total weight would probably be in the ten pound range, and since it can
be activated from any point on the ring and sever the two stages in a
millisecond or two you save a lot of wiring weight as well compared to
multiple explosive bolts.

would be fairly heavy. Explosive bolts are used regularly on
spacecraft, and only fail once in a while. I think the old addage of
"Better the devil you know..."

In this case it's a known quantity; it's used in solid-fuel missiles to
separate stages and vent the casing when thrust termination is desired.
The concept goes clean back to WW II when the Germans were going to use
cord-type shaped charges to cut apart Wasserfall SAMs that missed their
targets to prevent large pieces of them falling onto German cities.
The self-destruct system on both liquid and solid-fueled boosters
generally use a shaped charge down the length of the rocket to rip it
open in case it goes out of control.

Pat

Brian Gaff wrote:
Likkle vernier rockets pointing upwards?


That's been done many a time, up to using upward pointing solid engines
to slow down the Saturn V first stage, as the other ones on the
interstage push the second stage away from it.
Another technique is to ignite the second stage just before the first
stage shuts down, and let its thrust carry it away from the first stage
as its trust decays
In that case you also avoid the need for ullage motors to seat the
propellants in the second stage after first stage shut down.
The Russians are particularly fond of using that technique, which is why
on a lot of their rockets the stages are connected by trusswork so that
the exhaust of the stage being started can escape until the stage below
it separates.
We used the same idea on the Titan II missile.

Pat

"Alan Erskine" wrote:

"Pat Flannery" wrote in message
hdakotatelephone...

You could sever them using a linear shaped charge around the body of the
vehicle.

One word for both Pat and Derek on this: mass. Surely a shaped charge, even
a small one, would be fairly heavy.

Explosive bolts and all the associated hardware (bolt retainers and
catchers) aren't exactly light either. Shape charges and zip tubes
have the advantage of a hell of a lot less wiring.

Explosive bolts are used regularly on spacecraft, and only fail once in a
while. I think the old addage of "Better the devil you know...".

The methods I described are regularly used as well and also only fail
once in a while.

D.
--
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http://derekl1963.livejournal.com/

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

On Aug 5, 7:09*am, Pat Flannery wrote:
Brian Gaff wrote:
Likkle vernier *rockets pointing upwards?

That's been done many a time, up to using upward pointing solid engines
to slow down the Saturn V first stage, as the other ones on the
interstage push the second stage away from it.
Another technique is to ignite the second stage just before the first
stage shuts down, and let its thrust carry it away from the first stage
as its trust decays

Wouldn't that damage the first stage, which is supposed to
be recovered for re-use?

In that case you also avoid the need for ullage motors to seat the
propellants in the second stage after first stage shut down.
The Russians are particularly fond of using that technique, which is why
on a lot of their rockets the stages are connected by trusswork so that
the exhaust of the stage being started can escape until the stage below
it separates.
We used the same idea on the Titan II missile.

Pat

wrote:
Another technique is to ignite the second stage just before the first
stage shuts down, and let its thrust carry it away from the first stage
as its trust* decays


Wouldn't that damage the first stage, which is supposed to
be recovered for re-use?


* That should be "thrust" BTW. :-)
The total time between ignition and stage separation wouldn't be that
long, a couple of seconds probably.
You could put some sort of thin ablative cap over the top of the first
stage that would cover the parachutes and be jettisoned after stage
separation had occurred.
Although the core stage isn't recoverable, the Russians used a cap
shaped like a blast deflector between the core and upper stage of the
Vostok booster: http://en.wikipedia.org/wiki/Image:V...et_drawing.png
You can see it inside of the trusswork and under the upper stage engine
nozzle in that drawing.

Pat

"Pat Flannery" wrote in message
dakotatelephone...


Alan Erskine wrote:

Other than the two mentioned, what can be used for stage sep?

You could sever them using a linear shaped charge around the body of the
vehicle.
This would have a advantage over multiple explosive bolts in that the whole
thing would fire at once from a single detonation point, improving
reliability.
The odd stage separation of flight two makes it look like one explosive bolt
fired late or not at all, causing the engine bell to hit the interstage
structure as the first stage fell away.


In the flight 2 report they said the bump was due to using a wrong
fuel mixture curve. Too lean at low altitude, so reduced thrust
and the staging took place at a much lower altitiude than planned.
Which means the staging happened while still under aerodynamic
forces...and...while the space craft wasn't aligned with the wind.







Pat

In article ,
(Derek Lyons) wrote:

Or something as simple as thrust created by gas exhausting from the
(new) cooling system. Geez Louise. Does Falcon 1 use anything other
than explosive bolts and springs for stage separation? How many more
basic errors can they afford to re-discover?

Other than the two mentioned, what can be used for stage sep?

FLSC - flexible linear shaped charge, used to cut through the skin of
the bird. Or 'zip tubing' (I forget the exact term) which is a thick
walled pipe/tube filled with fiberglass and a low explosive, when
fired the tube expands and fractures the skin.

One could also use tension ties or cables with the appropriate
cutters. (As Apollo did to retain both the CM and the LES.)

Those are methods for cutting the stages apart. Then you need something
to ensure that they continue moving away from each other: thrusters on
the first stage to slow it, or firing the second stage just before
separation.

richard schumacher wrote:

:In article ,
: (Derek Lyons) wrote:
:
: Or something as simple as thrust created by gas exhausting from the
: (new) cooling system. Geez Louise. Does Falcon 1 use anything other
: than explosive bolts and springs for stage separation? How many more
: basic errors can they afford to re-discover?
:
: Other than the two mentioned, what can be used for stage sep?
:
: FLSC - flexible linear shaped charge, used to cut through the skin of
: the bird. Or 'zip tubing' (I forget the exact term) which is a thick
: walled pipe/tube filled with fiberglass and a low explosive, when
: fired the tube expands and fractures the skin.
:
: One could also use tension ties or cables with the appropriate
: cutters. (As Apollo did to retain both the CM and the LES.)
:
:Those are methods for cutting the stages apart. Then you need something
:to ensure that they continue moving away from each other: thrusters on
:the first stage to slow it, or firing the second stage just before
:separation.
:

Or maybe just some strong springs compressed between the stages and
some pop-out drag brakes on the first stage. Not much air up there,
but you're already moving pretty fast so maybe just a little drag is
enough...

--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw

That is what I was thinking, hence my thought on the deceleration motors,
but this is weight taken away from payload, I suppose.

Whichever way you look at it, you cannot just assume that the two bodies
coasting for a short time will give the desired separation. If you coast
too long, in order to protect your first stage from plume damage, you run
the risk of sloshing in the upper stage suddenly released from thrust with
no continuation within the time you have before it goes float about in the
tank.
Brian

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wrote in message
...
On Aug 5, 7:09 am, Pat Flannery wrote:
Brian Gaff wrote:
Likkle vernier rockets pointing upwards?

That's been done many a time, up to using upward pointing solid engines
to slow down the Saturn V first stage, as the other ones on the
interstage push the second stage away from it.
Another technique is to ignite the second stage just before the first
stage shuts down, and let its thrust carry it away from the first stage
as its trust decays

Wouldn't that damage the first stage, which is supposed to
be recovered for re-use?

In that case you also avoid the need for ullage motors to seat the
propellants in the second stage after first stage shut down.
The Russians are particularly fond of using that technique, which is why
on a lot of their rockets the stages are connected by trusswork so that
the exhaust of the stage being started can escape until the stage below
it separates.
We used the same idea on the Titan II missile.

Pat