Thrust Oscillation Issue Threatens Ares I Design, Aviation Week

"Pat Flannery" wrote in message
...


George wrote:
"Pat Flannery" wrote in message
...

George wrote:

I'm certainly not a rocket scientist by any stretch, but it would
appear that some type of dampening needs to occur between the solid
rocket motors and the Orion. Can this be accomplished by placing the
Orion in some kind of dampening skid, possiibly made of vulcanized
rubber? It might even solve the problem of what to do with all those
defective Firestone tires. :-)

It would be best if the dampening occurred between the SRB stage and
the LOX/LH2 upper stage.
If these were hooked together by warren truss girders the way the
Russians attach the upper stage of the Soyuz booster to the basic R-7
lower stage, it might be possible to incorporate some sort of shock
absorbers into that support structure and isolate the vibrations
created by the SRB from the whole upper part of the vehicle... this
would be ideal, as you don't want high frequency vibrations going
through the lightly built cryogenic upper stage either.

Pat


Good points. I wasn't sure where exactly the isolation should occur,
but isolating the SRBs from the rest of the stack altogether seems to me
to be the best remedy.

On Ares I (the one with the vibration problem) there's only a single SRB
forming the first stage:
http://images.spaceref.com/news/2006/ares.1.chart.jpg


Sorry about that. I didn't mean to imply that there was more than one SRB
on Ares.

Good idea. I like the truss girder idea. Probably cheaper and less
impact on mass as well. Possibly they could be constructed from
vibration-absorbing composite materials. I think the second vehicle
from the left in the drawing at the link below may be something like
what you are describing:

http://www.friends-partners.org/part...l/lktksles.jpg


That's the lunar landing stage for the Chelomei UR-700 direct ascent
manned Moon mission from the 1960's USSR.
In that case the truss girders are to cut weight down rather than using a
solid cylindrical structure to join the two bottom stages to the landing
section of the spacecraft.
On the Soyuz core stage (which bears a uncanny resemblance to Ares 1 once
the four strap-on boosters are jettisoned):
http://esamultimedia.esa.int/images/...2A_08182_H.jpg
The upper stage is attached by the girders so that its engines can be
ignited while still attached to the core stage, and their exhaust can
escape from the spaces between the girders prior to separation of the
upper stage. In this manner there are no ullage rockets needed to keep
the propellants in the upper stage seated during staging, as the rocket
is under trust during the whole ascent (we used the same technique on the
Titan II). Some Russian model rocket builders did a detailed metal model
of the truss frame that holds the core and upper stages of a Soyuz
boosters together, so you can see it's structural design:
http://www.rocket.aero/soyuz2big.jpg http://www.rocket.aero/soyuz4big.jpg
If you look to the right of the second photo, that's the end that hooks
to the upper stage. If you were to install some sort of vibration
dampening devices in those short cylinders that attach to the upper stage
base ring (shown detached in the first photo)
that would allow the vibrations to be isolated to the first stage.

Or possibly something like this:

http://www.friends-partners.org/part...r/r7ur5cut.gif

I believe the Soviet N-1 also used such trusses.


Yes, that shows Chelomei's Proton (UR-500), and both it and Korolev's
N-1 used the same "engine firing while stages still attached" technique
as the Soyuz Korolev designed. It was a very common feature on Soviet
space boosters and missiles.
I don't know if any had any sort of vibration dampening system
incorporated into the attachment trusses.
Its use on the RT-2 (NATO code name SS-13 Savage)
http://www.fas.org/nuke/guide/russia/icbm/rt-2.htm
Is interesting, as this was a solid-fueled ICBM... so it wouldn't need
any ullage rockets on it.
In this case one can wonder if its primary use was some sort of vibration
dampening.

Pat

Sounds like a plan to me.

George

"George" wrote in message
. ..

"Pat Flannery" wrote in message
...


George wrote:
"Pat Flannery" wrote in message
...

George wrote:

I'm certainly not a rocket scientist by any stretch, but it would
appear that some type of dampening needs to occur between the solid
rocket motors and the Orion. Can this be accomplished by placing the
Orion in some kind of dampening skid, possiibly made of vulcanized
rubber? It might even solve the problem of what to do with all those
defective Firestone tires. :-)

It would be best if the dampening occurred between the SRB stage and
the LOX/LH2 upper stage.
If these were hooked together by warren truss girders the way the
Russians attach the upper stage of the Soyuz booster to the basic R-7
lower stage, it might be possible to incorporate some sort of shock
absorbers into that support structure and isolate the vibrations
created by the SRB from the whole upper part of the vehicle... this
would be ideal, as you don't want high frequency vibrations going
through the lightly built cryogenic upper stage either.

Pat


Good points. I wasn't sure where exactly the isolation should occur,
but isolating the SRBs from the rest of the stack altogether seems to me
to be the best remedy.

On Ares I (the one with the vibration problem) there's only a single SRB
forming the first stage:
http://images.spaceref.com/news/2006/ares.1.chart.jpg


Sorry about that. I didn't mean to imply that there was more than one SRB
on Ares.

Good idea. I like the truss girder idea. Probably cheaper and less
impact on mass as well. Possibly they could be constructed from
vibration-absorbing composite materials. I think the second vehicle
from the left in the drawing at the link below may be something like
what you are describing:

http://www.friends-partners.org/part...l/lktksles.jpg


That's the lunar landing stage for the Chelomei UR-700 direct ascent
manned Moon mission from the 1960's USSR.
In that case the truss girders are to cut weight down rather than using a
solid cylindrical structure to join the two bottom stages to the landing
section of the spacecraft.
On the Soyuz core stage (which bears a uncanny resemblance to Ares 1 once
the four strap-on boosters are jettisoned):
http://esamultimedia.esa.int/images/...2A_08182_H.jpg
The upper stage is attached by the girders so that its engines can be
ignited while still attached to the core stage, and their exhaust can
escape from the spaces between the girders prior to separation of the
upper stage. In this manner there are no ullage rockets needed to keep
the propellants in the upper stage seated during staging, as the rocket
is under trust during the whole ascent (we used the same technique on the
Titan II). Some Russian model rocket builders did a detailed metal model
of the truss frame that holds the core and upper stages of a Soyuz
boosters together, so you can see it's structural design:
http://www.rocket.aero/soyuz2big.jpg http://www.rocket.aero/soyuz4big.jpg
If you look to the right of the second photo, that's the end that hooks
to the upper stage. If you were to install some sort of vibration
dampening devices in those short cylinders that attach to the upper stage
base ring (shown detached in the first photo)
that would allow the vibrations to be isolated to the first stage.

Or possibly something like this:

http://www.friends-partners.org/part...r/r7ur5cut.gif

I believe the Soviet N-1 also used such trusses.


Yes, that shows Chelomei's Proton (UR-500), and both it and Korolev's
N-1 used the same "engine firing while stages still attached" technique
as the Soyuz Korolev designed. It was a very common feature on Soviet
space boosters and missiles.
I don't know if any had any sort of vibration dampening system
incorporated into the attachment trusses.

I seriously doubt it. The way you fix a pogo problem is you stick a pogo
suppressor in the fuel feed to the engine (essentially a space where the
fuel pressure variations are damped out, similar to the suppressors used on
water lines to prevent "water hammer".

Its use on the RT-2 (NATO code name SS-13 Savage)
http://www.fas.org/nuke/guide/russia/icbm/rt-2.htm
Is interesting, as this was a solid-fueled ICBM... so it wouldn't need
any ullage rockets on it.
In this case one can wonder if its primary use was some sort of vibration
dampening.

Pat

Sounds like a plan to me.

Except that I don't think that the Ares I design has mass margin available
to deal with this problem in the way you propose.

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

Jeff Findley wrote:
Yes, that shows Chelomei's Proton (UR-500), and both it and Korolev's
N-1 used the same "engine firing while stages still attached" technique
as the Soyuz Korolev designed. It was a very common feature on Soviet
space boosters and missiles.
I don't know if any had any sort of vibration dampening system
incorporated into the attachment trusses.


I seriously doubt it. The way you fix a pogo problem is you stick a pogo
suppressor in the fuel feed to the engine (essentially a space where the
fuel pressure variations are damped out, similar to the suppressors used on
water lines to prevent "water hammer".


They didn't know about that early on, as it was the water hammer effect
that caused all the plumbing to the central six engines on the N-1 first
stage to rupture when the engines were shut down late in the first stage
burn on the last flight to prevent over-stressing the vehicle due to too
much acceleration while low on propellants.
One of the hypothesized problems related to manned launches on the
Proton was supposed to be that its long thin design would lead to
excessive vibration at the top where the manned capsule would be just
from the normal firing of the six first stage engines.

Its use on the RT-2 (NATO code name SS-13 Savage)
http://www.fas.org/nuke/guide/russia/icbm/rt-2.htm
Is interesting, as this was a solid-fueled ICBM... so it wouldn't need
any ullage rockets on it.
In this case one can wonder if its primary use was some sort of vibration
dampening.

Pat

Sounds like a plan to me.


Except that I don't think that the Ares I design has mass margin available
to deal with this problem in the way you propose.


We are certainly getting very near the edge of what it can do without
lightening up Orion; but if the vibration problem is as severe as some
studies indicate, it's either lighten up Orion, or ditch the whole Aries
I booster.
Of course...maybe there is a way to lighten it up overall and still keep
Orion at full weight.
Now we know how reliable the SRB is - damn near 100%. And if the upper
stage fails the Orion will be at high enough altitude to just separate
from it and do a reentry. So I'm thinking we ditch the LES...it's
unnecessary...the vehicle's as safe as a airliner, so why should it need
as LES anyway? ;-)
You just wait, sooner or later someone at NASA will propose exactly that.

Pat

"Jeff Findley" wrote in message
...

"George" wrote in message
. ..

"Pat Flannery" wrote in message
...


George wrote:
"Pat Flannery" wrote in message
...

George wrote:

I'm certainly not a rocket scientist by any stretch, but it would
appear that some type of dampening needs to occur between the solid
rocket motors and the Orion. Can this be accomplished by placing the
Orion in some kind of dampening skid, possiibly made of vulcanized
rubber? It might even solve the problem of what to do with all
those defective Firestone tires. :-)

It would be best if the dampening occurred between the SRB stage and
the LOX/LH2 upper stage.
If these were hooked together by warren truss girders the way the
Russians attach the upper stage of the Soyuz booster to the basic R-7
lower stage, it might be possible to incorporate some sort of shock
absorbers into that support structure and isolate the vibrations
created by the SRB from the whole upper part of the vehicle... this
would be ideal, as you don't want high frequency vibrations going
through the lightly built cryogenic upper stage either.

Pat


Good points. I wasn't sure where exactly the isolation should occur,
but isolating the SRBs from the rest of the stack altogether seems to
me to be the best remedy.

On Ares I (the one with the vibration problem) there's only a single
SRB forming the first stage:
http://images.spaceref.com/news/2006/ares.1.chart.jpg


Sorry about that. I didn't mean to imply that there was more than one
SRB on Ares.

Good idea. I like the truss girder idea. Probably cheaper and less
impact on mass as well. Possibly they could be constructed from
vibration-absorbing composite materials. I think the second vehicle
from the left in the drawing at the link below may be something like
what you are describing:

http://www.friends-partners.org/part...l/lktksles.jpg


That's the lunar landing stage for the Chelomei UR-700 direct ascent
manned Moon mission from the 1960's USSR.
In that case the truss girders are to cut weight down rather than using
a solid cylindrical structure to join the two bottom stages to the
landing section of the spacecraft.
On the Soyuz core stage (which bears a uncanny resemblance to Ares 1
once the four strap-on boosters are jettisoned):
http://esamultimedia.esa.int/images/...2A_08182_H.jpg
The upper stage is attached by the girders so that its engines can be
ignited while still attached to the core stage, and their exhaust can
escape from the spaces between the girders prior to separation of the
upper stage. In this manner there are no ullage rockets needed to keep
the propellants in the upper stage seated during staging, as the rocket
is under trust during the whole ascent (we used the same technique on
the Titan II). Some Russian model rocket builders did a detailed metal
model of the truss frame that holds the core and upper stages of a
Soyuz boosters together, so you can see it's structural design:
http://www.rocket.aero/soyuz2big.jpg
http://www.rocket.aero/soyuz4big.jpg
If you look to the right of the second photo, that's the end that hooks
to the upper stage. If you were to install some sort of vibration
dampening devices in those short cylinders that attach to the upper
stage base ring (shown detached in the first photo)
that would allow the vibrations to be isolated to the first stage.

Or possibly something like this:

http://www.friends-partners.org/part...r/r7ur5cut.gif

I believe the Soviet N-1 also used such trusses.


Yes, that shows Chelomei's Proton (UR-500), and both it and Korolev's
N-1 used the same "engine firing while stages still attached" technique
as the Soyuz Korolev designed. It was a very common feature on Soviet
space boosters and missiles.
I don't know if any had any sort of vibration dampening system
incorporated into the attachment trusses.

I seriously doubt it. The way you fix a pogo problem is you stick a pogo
suppressor in the fuel feed to the engine (essentially a space where the
fuel pressure variations are damped out, similar to the suppressors used
on water lines to prevent "water hammer".

Its use on the RT-2 (NATO code name SS-13 Savage)
http://www.fas.org/nuke/guide/russia/icbm/rt-2.htm
Is interesting, as this was a solid-fueled ICBM... so it wouldn't need
any ullage rockets on it.
In this case one can wonder if its primary use was some sort of
vibration dampening.

Pat

Sounds like a plan to me.

Except that I don't think that the Ares I design has mass margin
available to deal with this problem in the way you propose.

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


Well, they have to attach the 1st stage to the second stage somehow. Why
not attach it using a truss with dampening shocks? How much more could
that weigh?

George

George wrote:

Well, they have to attach the 1st stage to the second stage somehow. Why
not attach it using a truss with dampening shocks? How much more could
that weigh?

You realize of course that the second stage is a fully fueled SSTO
capable core stage with a 60,000 lb. manned payload sitting atop it?

Am I imagining things, or is stupidity strictly an American trait?

"George" wrote in message
. ..

"Jeff Findley" wrote in message
...
Except that I don't think that the Ares I design has mass margin
available to deal with this problem in the way you propose.

Well, they have to attach the 1st stage to the second stage somehow. Why
not attach it using a truss with dampening shocks? How much more could
that weigh?

A lot more than you might think. You not only need shock absorbers, but
some sort of spring mechanism that can operate over the range of G loads
expected for first stage (especially later in the burn where the vibrations
from the SRB's is supposedly the highest).

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

Jeff Findley wrote:
A lot more than you might think. You not only need shock absorbers, but
some sort of spring mechanism that can operate over the range of G loads
expected for first stage (especially later in the burn where the vibrations
from the SRB's is supposedly the highest).


Somebody suggested car tires... and you know, that might not be too far
off-target. The engine in your car rests on rubber gaskets to isolate
its vibrations from the frame, as does the interior machinery on atomic
submarines to prevent noise propagating into the hull.

Pat

Pat Flannery wrote:



Jeff Findley wrote:
A lot more than you might think. You not only need shock absorbers, but
some sort of spring mechanism that can operate over the range of G loads
expected for first stage (especially later in the burn where the
vibrations from the SRB's is supposedly the highest).


Somebody suggested car tires... and you know, that might not be too far
off-target. The engine in your car rests on rubber gaskets to isolate
its vibrations from the frame, as does the interior machinery on atomic
submarines to prevent noise propagating into the hull.

It's not a new problem. NASA is reinventing the wheel, or forgot what it
looks like. My car has a dampener on it too, called shocks, or struts.
Engine mounts, you mentioned, usually they don't go bad for twenty years or
so, most people hardly ever think of them. It's the late date of the
discovery that is questionable.

NASA should be freed from it's Monopoly status and allowed to compete in the
private sector for Launch/Landing services. Then if they think really like
the solids, they can get their own funding instead of taxes and build it.
The would could see if solids were the right choice. Oh, Yeah, that goes
for the Post Office too. They should be allowed to compete too.

"Jeff Findley" writes:

Well, they have to attach the 1st stage to the second stage somehow. Why
not attach it using a truss with dampening shocks? How much more could
that weigh?

A lot more than you might think. You not only need shock absorbers, but
some sort of spring mechanism that can operate over the range of G loads
expected for first stage (especially later in the burn where the vibrations
from the SRB's is supposedly the highest).

You would also need to make sure that the shock absorbers don't form a
kind of springy joint between the stages. Because if they do this will
make controlling the stack almost impossible. In fact Ares I is already
very hard to control (heavy but narrow first stage, light but wide upper
stage -- this thing will try to turn into its only aerodynamically
stable position, which is bottom-up) and having it wobble around an
elastic joint between the stages would be a very bad thing. You would
have to make sure the shock absorbers are springy only in the long axis
and at the same time very stiff against any kind of bending.

I'm quite sure the control people would turn very pale if someone wanted
to integrate shock absorbers or any kind of vibration dampening between
the stages. This thing has to be as stiff as possible if you want to
keep it going straight.


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

Jochem Huhmann wrote:
"Jeff Findley" writes:

Well, they have to attach the 1st stage to the second stage somehow. Why
not attach it using a truss with dampening shocks? How much more could
that weigh?
A lot more than you might think. You not only need shock absorbers, but
some sort of spring mechanism that can operate over the range of G loads
expected for first stage (especially later in the burn where the vibrations
from the SRB's is supposedly the highest).

You would also need to make sure that the shock absorbers don't form a
kind of springy joint between the stages. Because if they do this will
make controlling the stack almost impossible. In fact Ares I is already
very hard to control (heavy but narrow first stage, light but wide upper
stage -- this thing will try to turn into its only aerodynamically
stable position, which is bottom-up) and having it wobble around an
elastic joint between the stages would be a very bad thing. You would
have to make sure the shock absorbers are springy only in the long axis
and at the same time very stiff against any kind of bending.

I'm quite sure the control people would turn very pale if someone wanted
to integrate shock absorbers or any kind of vibration dampening between
the stages. This thing has to be as stiff as possible if you want to
keep it going straight.

I thought this thing was a done deal, Michael Griffin said he was going
to pump the big dick thing up with steroids and viagra and stuff.

Apollo on Steroid! And this man is in charge of your inestimable
scientific institutions. Good luck America, you're going to need it.