A price for my used struts

[Guest]

Re: A price for my used struts

I'll give Wag a call tomorrow and see what their prefered method is. If the world doesn't fall apart tomorrow I will post their answer. They are going to try and launch the Ares 1X again between 8 and 12 Eastern. Not my project, but it will have a major impact if it breaks up at Max Q on all the MSF projects (including mine).
Hank

What happens at high resonance?

oh yeah I forgot to ask this; When does the highest resonance occur?

[Hank Jarrett]

Re: A price for my used struts

Ares 1X uses the solid rockets that were used on Shuttle as a first stage (the solid rockets that are strapped to the sides of the external tank). Solid rocket motors don't burn from the bottom to the top, they are hollow down the center and burn from the middle to the edges. Think of them like a big organ pipe that plays at a very low frequency. They are also VERY LOUD and the sonic vibration from that long organ pipe shakes everything really hard. On the shuttle there is a HUGE orange tank filled with liquid hydrogen and liquid oxygen, as well as the mass of the shuttle and the attach hardware that flexes to absorb all that vibration. Even then if you watch a launch from the crew area everyone is banging around like mad.
On Ares the capsule is right on top of the booster and all that vibration passes right up the stack to the capsule and crew. It has been a BIG problem with lots of design "work around" designs. There was a weak spot in the design at the frustrum (where the small diameter first stage transitions to the larger diameter second stage. It has been really beefed up to take the loads. Those loads peak close to the point of max dynamic pressure (if you are listening to the launch you will hear a "Max Q" or "Point on Maximum Dynamic Pressure" call from Mission Control (it was right after that call at throttle up that the shuttle blew up). If it is going to fail, that is probably where it will happen.
I guess you asked what time it is and I just told you how to build a clock. High resonance is when the vibration in the vehicle hits the natural vibration frequency of a part, causing it to fail. You really try to design all your parts AWAY from that frequency of the engine to keep them from breaking up. I'm not sure they have moved the natural frequency of the parts far enough away from the resonant frequency of the engine.
They are in hold right now at 4 minutes. If anyone wants to watch it is on their computer it is streaming at http://www.nasa.gov/multimedia/nasatv/index.html
Looks like 9:00 Eastern at the earliest for a launch (got to check for lightning damage. Sometimes it doesn't hit the towers near the vehicle like it's supposed to).
Hank

[Guest]

Re: A price for my used struts

Ares 1X uses the solid rockets that were used on Shuttle as a first stage (the solid rockets that are strapped to the sides of the external tank). Solid rocket motors don't burn from the bottom to the top, they are hollow down the center and burn from the middle to the edges. Think of them like a big organ pipe that plays at a very low frequency. They are also VERY LOUD and the sonic vibration from that long organ pipe shakes everything really hard. On the shuttle there is a HUGE orange tank filled with liquid hydrogen and liquid oxygen, as well as the mass of the shuttle and the attach hardware that flexes to absorb all that vibration. Even then if you watch a launch from the crew area everyone is banging around like mad.
On Ares the capsule is right on top of the booster and all that vibration passes right up the stack to the capsule and crew. It has been a BIG problem with lots of design "work around" designs. There was a weak spot in the design at the frustrum (where the small diameter first stage transitions to the larger diameter second stage. It has been really beefed up to take the loads. Those loads peak close to the point of max dynamic pressure (if you are listening to the launch you will hear a "Max Q" or "Point on Maximum Dynamic Pressure" call from Mission Control (it was right after that call at throttle up that the shuttle blew up). If it is going to fail, that is probably where it will happen.
I guess you asked what time it is and I just told you how to build a clock. High resonance is when the vibration in the vehicle hits the natural vibration frequency of a part, causing it to fail. You really try to design all your parts AWAY from that frequency of the engine to keep them from breaking up. I'm not sure they have moved the natural frequency of the parts far enough away from the resonant frequency of the engine.
They are in hold right now at 4 minutes. If anyone wants to watch it is on their computer it is streaming at http://www.nasa.gov/multimedia/nasatv/index.html
Looks like 9:00 Eastern at the earliest for a launch (got to check for lightning damage. Sometimes it doesn't hit the towers near the vehicle like it's supposed to).
Hank

Hi Hank,
Perfect explanation, thanks.

I am familiar with "Q" wondered what happens (on a rocket) at peak q and what cuases it. That was perfect, thanks, Dave.

[Hank Jarrett]

Re: A price for my used struts

Max Q is actually where Dynamic Pressure is at a peak. Dynamic pressure is the combination of the forces from atmospheric density and velocity through the atmosphere. At liftoff, pressure is highest and velocity is lowest. At MECO (Main Engine Cut Off) velocity is highest and pressure is lowest. At Max Q the combination is highest. On a Shuttle launch they actually throttle back and fly the Max Q curve. When you hear Mission Control say "you are GO for throttle up" on a shuttle shot they are saying that the shuttle has climbed high enough for the air to thin out so they can increase velocity with more thrust. It's all a balancing act.
On Ares the loads that can kill a booster are usually the lift the "tube" is generating because it doesn't actually fly along it's longitudinal axis. The air is hitting it at an angle that causes the rocket body to try and bend. If the booster fails, it would probably be in bending at the weakest point (in bending) which I think is at the frustrum.
Many don't agree with me. ;-) I hope it has been reinforced enough.
Hank

[Hank Jarrett]

Re: A price for my used struts

If you saw the launch you know what happened.
Don't count on ever seeing the whole video again.
On the shipping of struts, I talked to John Armes at Wag today and he says they HAVE gotten struts in a 6" PVC tube and they ARE heavy. He suggested a crate might be lighter with all 4 struts standing up on edge and locked into the box. Got to see what the weight will look like.
They get a lot of their parts shipped in through D.B. Schenker (used to be called Bax Global) so I will try and contact them. Other companies they have used are Common Carrier, Consolidated Freight and Tax Air. If anyone has had really good or bad luck with any of these shippers give a yell and let the rest of us know.
Hank

[Robert Lees]

Re: A price for my used struts

If you saw the launch you know what happened.
Don't count on ever seeing the whole video again.

It tumbled...was that the plan? (just watched it on your link).

[Hank Jarrett]

Re: A price for my used struts

No, it should have flown a parabolic arc (lawn dart style) all the way to the water.
There were several "HOLY C**P! DID YOU SEE THAT!" statements among the people who saw it. One of the cameras showed at least four full spins of the second stage before they cut the video link. Made my hair stand up.

Hank

[Hank Jarrett]

Re: A price for my used struts

To be fair, the test was of the FIRST STAGE FLIGHT only. Once the stages separated, the dynamics were all changed.
Hank