RATT - 4 Motor Cluster - Flight Report

Well I finally quit talking about it and did it. I built a 3 inch
rocket in April for clustering RATT Hybrids. The "Better RATT Trap"
is a 3 inch airframe that is about 100 inches in length. She is built
to fly on 4 I90's. I was going to fly her at LDRS but was one I90
short of a full load.
Saturday's Launch with the Jackson Model Rocket Club was held at our
winter venue...A farm field with about a square mile of recovery area.
It was high time to let her loose. I arrived at the field with the
bird fully prepped and waited until early afternoon for the wind to
die down. She was loaded with 2 I90's and 2 H70's. I had Doug Pratt
whip me up a manifold that allows me to fill all 4 motors at the same
time....worked like a charm.
After waiting a while we walked her out to the pad in about a 12 MPH
wind. We used an extended rail.....which blew over as we were walking
back to the LCO desk. The wind had picked back up... Popped both Acme
Rail Guides off of the airframe...Thought it was all over at that
point. However in true JMRC fashion I was assisted in installing rail
buttons at the pad....good friends...rail buttons and CA glue....what
a combination. She was ready to go...AGAIN!!!!
We walked back to the LCO desk and tanked her up. The H70's began to
vent after about 8 seconds followed closely by the I90's after a 5
count the LCO (Scott Miller of SFSM Industries) pushed the "GO"
button. 2 of the motors came to life immedietely and she beggan to
crawl up the rail.....Whats up! Then she shifted gears....post flight
analysis of the video shows the 6 feet of "fill tube umbilical"
stretching until all burned through. She lept off the rail and at 300
feet ....the second I 90 and kicked in to full thrust and she shifted
gears again and dissapeared into the clear blue sky going 3980 feet
per the Adept ALT S25.
Post Flight analysis:
- Get all 4 motors to light at once:
All 4 lit but slightly more "sequencial" than I would have liked.
planning to use 2 igniters per motor paint the igniter grain with
Pyrogen or use dipped ematches....
- provide a mechanical means of freeing the bird:
looking at a static jig to cut fill tube at point of initial
thrust...it's clear in my mind but translating to paper at this point
is somewhat muddled.
- Need a good support team:
couldn't have done it with out the help of Scott Miller and the
encouragement (and video) provided by Todd Moore (Sky Ripper Systems).
There is an entire cast of supporting characters including Clayton,
Roger, Shawn and the entire JMRC Club.
- Do it again REALLY SOON:
Get my hands on 2 more I90 cases for the November Michigan Team1 launch
at Three Oaks and do it like I meant to when I designed her....
- Try Something New:
Need a "check valve" system...I want to airstart some RATT motors!!!!
Your comments and suggestions are appreciated.
Mark A Palmer
"Ratt Lover"
"Gas Passer"
TRA 08542 L3
Reply to
Mark A Palmer
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That was a great flight. I think I managed to snap off a picture just as it paused halfway up the rail. That was a scary moment. Glad she finally got going.
Do it again! Do it again!-- Tony Haga NAR #81532 L2
Reply to
Tony H.
Yeah...I'm working on that Stall thing....I would have thought that the RSO who signed off on that flight would have been a little more critical ;-).....what was his name!!!!
Congrats on your L2! You put in some pretty flights with pretty rockets....as usual!!!!
I hope to do it again real soon.
Mark A Palmer TRA 08542 L3
Reply to
Mark A Palmer
All that will do is move the sequential thrust problem to the other end of the flight as the slow igniting motors dump their NOX on the ground. Would a bit of pyrogen on the top end of the fill tube, or wrapping an ignitor around the tube, help make sure it burns through quickly?
Reply to
Eric Pederson
This is the first priority....I want them all to light on the pad. I am not sure about the moving the igniter any closer to the fill tube. I don't know the relationship between the ignition of the preheater, to the ignition of the fuel grain and the burn through of the fill tube.. Any body have any insite on whether the timing of the burn through to the ignition of the plastic fuel grain is critical?
Would a bit of pyrogen on the top end of the fill tube,
See above...I just want a contingency. I had 2 motors light immediately providing a 6 to 1 thrust ratio....more than enough to assure flight...but she went into slow motion 6 feet up a 12 foot rail. I want to be sure that she doesn't get hung up because a fill tube didn't burn through .
Mark A Palmer TRA 08542...L3
Reply to
Mark A Palmer
Wayne of Now Hybrids and myself have been doing ratt clusters for about 3 years now. The best bet is to use dipped davy fire 28 Fs and the manifold needs to be attached to the rail to prevent the rocket from taking off with out all the motors being lit. If you have a copy of LDRS XX video by extreme rocketery you can see the set up on my 3 ratt K-240 cluster. Wayne has successfully fired a cluster of 7 29mm ratt motors using this method, and wait until you see his next project. A hyper Tec center M with air starting 2 ratt M's and 2 Aerotec J-350s, we are working on a special manifold for air starting ratt hybrids.
Dave ~~~~~~~~~~~~~~~~~~~~~ Dave Griffith NAR 14156 The R.A.T.T.-works Monterey Machine Products 1504-A Industrial Park Street Covina, CA 91722 U.S.A.
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Reply to
What can I say? I wasn't thinking clearly at the time. But I can see that I will have to give your work much more scrutiny in the future ;) (and copy every bit of it...)
Reply to
Tony H.
OOOOOO....COOOOL....I want one....I want one.....
Great motors and great fun....The I90's just disappear ....Before they are done burning..... Thanks for the input....I will use dipped eMatches the next time around
Mark A Palmer TRA 08542 L3
M>>- Get all 4 motors to light at once:
Reply to
Mark A Palmer

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