[RocketsNW] stresses on a rocket

[Scott Berfield]

Thanks!

I can guarantee that I want nothing whatsoever to do with partial differential equations. I have managed to avoid them so for and am pretty sure I am immune to them anyway.

What I am trying to do is to clarify in my mind how much of what we build into these things is really required. In general, for smaller rockets, the structure and the aerodynamic skin are pretty much the same thing -- we have a motor mount tube, centering rings, and a tube all tied together into a fairly rigid structure. As thing scale up, it seems like most projects maintain this basic design. What I am thinking about is how much I can divorce the structural/strength part from the aerodynamic skin part. The overall rocket must be able to take the abuse of takeoff and acceleration, and that part I feel fairly confident about since it is pretty straightforward to see how the force gerts applied and is transferred. Where I am less certain is in how much requirement there is for the outer skin to be strong and/or rigid. An area I am particularly dumb about is what happens at the transition to supersonic flight.

My goal is to see what I can do to come up with larger rockets that are lighter and use less material yet still can handle the forces on them. Hopefully mostly without having to learn more math :)
-----Original Message-----
From: Eric Albrecht [mailto:blakbird11 at comcast.net]
Sent: Wednesday, May 13, 2009 11:32 PM
To: 'Rockets Northwest'
Subject: Re: [RocketsNW] stresses on a rocket

I'm a reference you can point at..... at which you can point. I analyze mechanical stresses on aerospace structures for a living. My major in college was in hypersonic flow dynamics. I can say in advance that the answers are significantly longer than the length of the question. ;-) I can also say that most reference books are fairly useless compared with the real world. Fire away with some questions or find me at FITS. If you REALLY want some deep reading, try "Analysis and Design of Flight Vehicle Structures" by Bruhn or "Airframe Stress Analysis and Sizing" by Michael Niu. If you just want some formulas to solve for stresses, the bible is "Roark's Formulas for Stress and Strain". If you want to dig into aerodynamic forces, any of John Anderson's books are good. "Introduction to Flight" is a good start, "Fundamentals of Aerodynamics" is heavier, and "Hypersonic and High Temperature Gas Dynamics" is heavy enough to sink the Titanic. These are all pretty expensive so if you'd like to borrow one I could probably send one your way. But asking me is way easier unless you are masochistic enough to dream about partial differential equations. As long as we're talking fun subjects, one of the important fields that lots of rocketeers don't think too much about is parachutes and their design. I highly recommend "Parachute Recovery Systems" by T.W. Knacke. He literally wrote the book on chutes and was the Head of Technical Staff of the team which designed the Apollo and Gemini recovery systems. I was lucky enough to take this class from him in college. Eric Albrecht On May 13, 2009, at 10:13 PM, Scott Berfield wrote: > I am looking for information on the mechanical stresses on a rocket > at launch and through boost at both subsonic and supersonic speeds. > Any of you engineer types have any references you could point me at? > _______________________________________________ > Rockets mailing list > Rockets at rocketsnw.com > http://mx1.blastzone.com/mailman/listinfo/rockets _______________________________________________ Rockets mailing list Rockets at rocketsnw.com http://mx1.blastzone.com/mailman/listinfo/rockets
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Thanks!
 
I can guarantee that I want nothing whatsoever to do with partial differential equations. I have managed to avoid them so for and am pretty sure I am immune to them anyway.
 
What I am trying to do is to clarify in my mind how much of what we build into these things is really required. In general, for smaller rockets, the structure and the aerodynamic skin are pretty much the same thing -- we have a motor mount tube, centering rings, and a tube all tied together into a fairly rigid structure. As thing scale up, it seems like most projects maintain this basic design. What I am thinking about is how much I can divorce the structural/strength part from the aerodynamic skin part. The overall rocket must be able to take the abuse of takeoff and acceleration, and that part I feel fairly confident about since it is pretty straightforward to see how the force gerts applied and is transferred. Where I am less certain is in how much requirement there is for the outer skin to be strong and/or rigid. An area I am particularly dumb about is what happens at the transition to supersonic flight.
 
My goal is to see what I can do to come up with larger rockets that are lighter and use less material yet still can handle the forces on them. Hopefully mostly without having to learn more math :)
-----Original Message-----
From:
Eric Albrecht [mailto:blakbird11 at comcast.net]
Sent:
Wednesday, May 13, 2009 11:32 PM
To:
'Rockets Northwest'
Subject:
Re: [RocketsNW] stresses on a rocket
I'm a reference you can point at..... at which you can point. I analyze mechanical stresses on aerospace structures for a living. My major in college was in hypersonic flow dynamics. I can say in advance that the answers are significantly longer than the length of the question. ;-) I can also say that most reference books are fairly useless compared with the real world. Fire away with some questions or find me at FITS. If you REALLY want some deep reading, try "Analysis and Design of Flight Vehicle Structures" by Bruhn or "Airframe Stress Analysis and Sizing" by Michael Niu. If you just want some formulas to solve for stresses, the bible is "Roark's Formulas for Stress and Strain". If you want to dig into aerodynamic forces, any of John Anderson's books are good. "Introduction to Flight" is a good start, "Fundamentals of Aerodynamics" is heavier, and "Hypersonic and High Temperature Gas Dynamics" is heavy enough to sink the Titanic. These are all pretty expensive so if you'd like to borrow one I could probably send one your way. But asking me is way easier unless you are masochistic enough to dream about partial differential equations. As long as we're talking fun subjects, one of the important fields that lots of rocketeers don't think too much about is parachutes and their design. I highly recommend "Parachute Recovery Systems" by T.W. Knacke. He literally wrote the book on chutes and was the Head of Technical Staff of the team which designed the Apollo and Gemini recovery systems. I was lucky enough to take this class from him in college. Eric Albrecht On May 13, 2009, at 10:13 PM, Scott Berfield wrote: > I am looking for information on the mechanical stresses on a rocket > at launch and through boost at both subsonic and supersonic speeds. > Any of you engineer types have any references you could point me at? > _______________________________________________ > Rockets mailing list > Rockets at rocketsnw.com > http://mx1.blastzone.com/mailman/listinfo/rockets _______________________________________________ Rockets mailing list Rockets at rocketsnw.com http://mx1.blastzone.com/mailman/listinfo/rockets