Certing Level 2 tomorrow with a CTI K675 Skidmark!! WOOOOOOOOO!!!!

The Rocketry Forum

Help Support The Rocketry Forum:

Mach_Seven

Well-Known Member
TRF Supporter
Joined
Jan 30, 2021
Messages
528
Reaction score
486
Mach, I am sorry for your loss. But I do thank you for the education you, I, and obviously a few others are receiving!

I also thank you all for your comments & inputs on this. This is a good / educational thread, despite the cause.. And that was my (uneducated) guess: the camera shroud causing an unbalance / off-center shock wave..


Mach - think 6-million dollar man: You can rebuild him, you can save him, you can fly him another day.,.
The problem with the Six Million Dollar Man is the six million dollars part.
 

KenECoyote

Well-Known Member
TRF Supporter
Joined
Mar 19, 2015
Messages
3,148
Reaction score
428
Thanks for that last line. I needed it! My confidence is a bit rattled right now.
I just visited the Kennedy Space Center (ROCKETS!!!! 😁🤩😍) as an unplanned last minute rush trip and was so glad I did it. If you're down and need inspiration, go there or Google Apollo missions 1 & 8.
JFK: "We choose to go to the Moon in this decade and do the other things, not because they are easy, but because they are hard, because that goal will serve to organize and measure the best of our energies and skills, because that challenge is one that we are willing to accept..."
 

Chuck Rogers

Well-Known Member
Joined
Jun 7, 2011
Messages
169
Reaction score
96
I asked Chuck Rogers(RASAero) Rogers Aeroscience, to see if he could sim your camera shroud and see if the transonic shock wave was throwing out the CP. The Camera shroud is in line with one of the fins. Certainly with the position and size of this shroud there is a possibility of this shockwave preventing one of your fins being seen by the airflow. Your video shows a wobble before break up at about the point it would have been in that speed region. As you go transonic, your dynamic forces increase dramatically. Also your camera shroud would be giving you quite a kick sideways at the point your airframe was approaching max load and perhaps shielding one of your fins on a longer than normal airframe.

Catching up on Rocketry Forum posts. Had problems with my primary computer, had to use various back-up computers including an iPhone and I got behind on e-mails and reading Rocketry Forum posts.


I quickly went through all the posts. From the preflight simulation, at the failure point at 2.5 seconds, what was the Mach number?


Norm has sent me some shroud geometry data, which I'll take a look at.


Some possible additional effects to those previously discussed:

1) The side area of the camera shroud added CNalpha up at the front of the rocket, moving the CP forward. RASAero II accurately predicts the drag of the shroud, but currently does not predict the CNalpha of the shroud. But the CNalpha from the shroud did move the rocket CP forward. The camera shroud was somewhat large compared to the diameter of the rocket.

2) With the drag of the camera shroud, the rocket flew at a small non-zero angle of attack. This small non-zero angle of attack also moved the CP forward.


Combine 1) and 2) above, and there was a forward movement of the CP, which may have been significant.


Again, RASAero II accurately predicts the drag of the camera shroud. You can run RASAero II with and without the camera shroud, look at the Drag Force output in the Flight Simulation plots, and the difference will be the drag of the camera shroud, which can be quite significant when the camera shroud height above the body tube is a significant fraction of the body tube diameter.


Charles E. (Chuck) Rogers
 

Mach_Seven

Well-Known Member
TRF Supporter
Joined
Jan 30, 2021
Messages
528
Reaction score
486
I just found something interesting when i watched the hd video on a big screen. At the :43 mark, a thin smoke trail can be seen emerging from the right of cloud. Looks like the motor- with or without the fin can - arced over well to the east. I was searching the wrong area. Going up with a friend of mine and his drone Saturday to try and find it.
 

Mach_Seven

Well-Known Member
TRF Supporter
Joined
Jan 30, 2021
Messages
528
Reaction score
486
Well, I’m gonna take some time off to reflect on everything I’ve learned from this fiasco. You guys might not hear from me for a while… just kidding. I’ve got an awesome new kit from Mac Performance on its way. THE SHOW GOES ON!!!
 

Grog6

Well-Known Member
Joined
Jul 19, 2021
Messages
291
Reaction score
183
Location
Oak Ridge TN
The mach shockwave tends to 'pin' on irregularities, and hangup there as it travels down the body.
I used to have a nosecone that was torn into little rings about 1/8 inch wide from where it went thru mach.
The body was confetti, lol.
 

Mach_Seven

Well-Known Member
TRF Supporter
Joined
Jan 30, 2021
Messages
528
Reaction score
486
The mach shockwave tends to 'pin' on irregularities, and hangup there as it travels down the body.
I used to have a nosecone that was torn into little rings about 1/8 inch wide from where it went thru mach.
The body was confetti, lol.
That's wild. Got any pics or vids?
 
Top