Ye Olde Rocket Forum

Go Back   Ye Olde Rocket Forum > Weather-Cocked > Mission Control
User Name
Password
Auctions Register FAQ Members List Calendar Today's Posts Search Mark Forums Read


Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 06-17-2018, 06:40 PM
A Fish Named Wallyum A Fish Named Wallyum is offline
BP Mafia
 
Join Date: Mar 2005
Location: Ft. Thomas, KY
Posts: 8,596
Default Bo-Mar Spartan Saturday flight

I guess I should have expected some bad Juju with this rocket after it sat on the pad for six cycles over two launches, four two weeks ago, then two more yesterday before finally launching on the seventh cycle. (Not just me. Quite a lot of sitting on the pad those two launches.) The flight was an A8-3 shakedown flight, low level because I expected to try it at B6-4 Field on my vacation, but that never happened. Instead I took it already loaded to Dayton to the WSR launch. Flight itself was perfect, straight up with ejection as forward motion slowed. The Spartan started acting odd as it descended. It would fall flat, then turn nose down, back to flat, then again to nose down. As it picked up speed the flat disappeared completely, and it whacked the ground hard in the nose down position. I thought that maybe I had packed the streamer too tight or possibly tangled it, but I never considered what I found as a possibility. Apparently the ejection charge caused a rebound. Also apparently the nose cone snapped back in the sideways position, embedding itself into the top of the body tube. The Kevlar, elastic and streamer were all clear of the body tube when I found it. The photos tell it better.
Attached Thumbnails
Click image for larger version

Name:  Bo-Mar Spartan glamour shot YORF.jpg
Views: 61
Size:  190.8 KB  Click image for larger version

Name:  Bo-Mar Spartan odd landing YORF.jpg
Views: 63
Size:  322.2 KB  Click image for larger version

Name:  Bo-Mar Spartan.jpg
Views: 74
Size:  40.3 KB  
__________________
Bill Eichelberger
NAR 79563

http://wallyum.blogspot.com/

I miss being SAM 0058

Build floor: Centuri Design Contest F-150 Hurricane Estes - Low Boom SST Semroc - Gee'Hod, Shrike, SST Shuttle

In paint: Canaroc Starfighter Scorpion Estes F-22 Air Superiority Fighter, Solar Sailer II Semroc Cyber III

Ready to fly: Estes - Multi-Roc, Solar Sailer II Semroc - Earmark, Snake Jumper
Reply With Quote
  #2  
Old 06-17-2018, 07:11 PM
erik442's Avatar
erik442 erik442 is offline
The Alpha Kid
 
Join Date: Mar 2012
Location: central PA
Posts: 419
Default

I've had some crazy mishaps on the flying field but that's a new one. I've never seen anything like that before.
Reply With Quote
  #3  
Old 06-17-2018, 09:31 PM
luke strawwalker's Avatar
luke strawwalker luke strawwalker is offline
BAR
 
Join Date: Dec 2007
Location: Needville and Shiner, TX
Posts: 6,134
Default

Ah... the dreaded "Estes dent" (as I've heard it called...) the shock cord stretches out to the limit due to inertia of the cone being BLASTED off the nose of the rocket from the powerful ejection charge, then the elastic snaps it back at Mach Chicken into the end of the tube, embedding the side of the nosecone onto the tube (if you're lucky and it doesn't just carve out a huge chunk from the side of the nosecone...

Basically it's caused by the shock cord being too short for the power of the ejection charge... it stretches to the limit, storing SO much energy that when it snaps back it does will FULL POWER and slams the parts together energetically enough to damage stuff...

I always harden my balsa cones with CA, and I've STILL had it happen. Worst I've had was on a Dr. Zooch "Friendship 7" anniversary kit, where the conical transition and Mercury spacecraft/tower nosecone recollided with the upper end of the BT-60 at ejection-- the cone actually struck on the shoulder, but off center, *almost* missing the tube entirely, but *not quite*... the tube struck the end grain off center and carved about a half-inch wide "smiley face" into the base of the cone shoulder, which then split up the grain and popped a chunk completely out of the side of the transition halfway up it's length, and about a quarter inch deep... I had to do "major reconstructive surgery" on the transition and repaint it to correct the damages...

It was my mistake in using the factory shock cord "as advertised"... Dr. Zooch had put a kevlar leader in there, *just short* of the end of the tube (since longer kevlar cords can EASILY cause tube zippers)-- just short enough that the end of the kevlar cord couldn't bear on the upper edge of the tube after ejection-- only the elastic cord that was tied onto the end of the kevlar leader that went out to the nosecone. Of course I was beta-building the kit at the time, and lengthening the shock cord would be "changing the design" so I didn't do it when I built it and flight tested it... It was probably a one in a million "bad hit" but that's still too high an odds IMHO, so after I fixed it (long after the testing phase for Wes was over) I removed the old elastic section of the shock cord and replaced it with one 3x longer than the original... Problem solved...

Later! OL J R
__________________
The X-87B Cruise Basselope-- THE Ultimate Weapon in the arsenal of Homeland Security and only $52 million per round!
Reply With Quote
  #4  
Old 06-17-2018, 11:29 PM
LeeR's Avatar
LeeR LeeR is offline
Retired with Way Too Many Kits
 
Join Date: Jun 2007
Location: Colorado
Posts: 3,222
Default

Quote:
Originally Posted by erik442
I've had some crazy mishaps on the flying field but that's a new one. I've never seen anything like that before.


My thoughts exactly. The only thing that comes to mind is what you surmised — that it must have been an overly strong ejection charge to blast the nose cone out so hard as to stretch the shock cord out to its limit, and have the nose cone then get retracted so strongly that it gets embedded in the tube. Sideways is odd!
__________________
Lee Reep
NAR 55948

Projects: Semroc Saturn 1B, Ken Foss Designs Mini Satellite Interceptor
In the Paint Shop: Nothing! Too cold!
Launch-Ready: Farside-X, Maxi Honest John, Super Scamp
Reply With Quote
  #5  
Old 06-18-2018, 12:47 AM
A Fish Named Wallyum A Fish Named Wallyum is offline
BP Mafia
 
Join Date: Mar 2005
Location: Ft. Thomas, KY
Posts: 8,596
Default

Quote:
Originally Posted by LeeR
My thoughts exactly. The only thing that comes to mind is what you surmised — that it must have been an overly strong ejection charge to blast the nose cone out so hard as to stretch the shock cord out to its limit, and have the nose cone then get retracted so strongly that it gets embedded in the tube. Sideways is odd!

Well, part of the depth is surely attributed to it coming in hot and landing straight on the side of the cone, but it after the ejection charge the nose cone never moved, so it was likely in there pretty well even before the contact.
__________________
Bill Eichelberger
NAR 79563

http://wallyum.blogspot.com/

I miss being SAM 0058

Build floor: Centuri Design Contest F-150 Hurricane Estes - Low Boom SST Semroc - Gee'Hod, Shrike, SST Shuttle

In paint: Canaroc Starfighter Scorpion Estes F-22 Air Superiority Fighter, Solar Sailer II Semroc Cyber III

Ready to fly: Estes - Multi-Roc, Solar Sailer II Semroc - Earmark, Snake Jumper
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump



All times are GMT -5. The time now is 06:13 AM.


Powered by: vBulletin Version 3.0.7
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Ye Olde Rocket Shoppe © 1998-2024