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The Midget has become one of my favorite rocket
types. As a kid, my original Midget was
my only two stage rocket. As a BAR, that same rocket gave me my first
two-stage flight, and it was thrilling. Both the booster and then
the sustainer seemed to burn forever - the rocket just climbed and climbed...
Since that magical flight ended with a zipper, I decided I'd better
build a replacement for regular use and retire my precious original. |
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| Several minor changes were made to the basic K-40
to make the rocket better. I used 3/32" balsa for the fins (instead
of 1/16"), and extended the body tube from 4" to 5" to provide a little
more space for the recovery system - hence the name Stridget for Stretched
Midget.
To save some effort, I planned to use the same booster I had already
made for my old Midget. One minor improvement
was extending the booster body tube just enough to accomodate an aft engine
block which ensures proper separation of the booster. Alas, this
booster (shown above on the left) met an untimely end; it was damaged beyond
repair while attempting to remove a stuck (bulging) booster motor.
The yellow booster on the right was built to replace it.
Another important detail of the Stridget is that the tailcone was changed
to taper from BT-50 down to BT-5 (instead of BT-50 to BT-20). This
makes for a more abrupt transition, and requires changing the fin template
slightly, but provides an unstepped connection to the booster.
I got a little carried away sanding the fins, and ended up rounding
the tips, but the basic shape of the Midget still comes through clearly.
It has made many successful flights, but a few bad ones, too. A booster
CATO sent the rocket on a short, unpowered flight. Fortunately, my
daughter got a hand on it on its way down, breaking its fall and leaving
it unscathed. Later, at another launch, the sustainer failed to ignite
- clay in the nozzle of the 1/4A3-3T - and the rocket lawndarted in the
street. Ouch! The nosecone was flat-spotted and swallowed by the
body tube, and the fin tips were a little chipped. But a replacement
nosecone was found and the forward 3/8" of body tube cut off to provide
a clean connection to the new nosecone. The Stridget would fly again.
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Tridget - Three Stage Midget
Motivated to fly a three-stage rocket, I decided to build a second,
intermediate booster (shown at right) for the Stridget. I scaled
the booster fins down somewhat, and, using Rocksim, was able to determine
the new three-stage configurate would be stable.
On its first three-stage flight, two bad things happened: Since there
was no aft engine block on the second booster (nor could there be), the
rocket spit the 2nd stage motor when the upper stage lit, but the 2nd stage
stayed stuck onto the tip of the sustainer motor. The exhaust from
the upper stage motor fried the 2nd stage and blistered its paint.
To add insult to injury, the sustainer failed to completely eject the
laundry, and the rocket took a core sample. Ugghhh!
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After the rocket had sat on my workbench for several weeks with a status
of FUBAR, my neighbor was studying it and declared that it could be repaired.
After I studied it, I realized that although its body tube was wrinkled,
that it was still straight. The rocket could continue to fly albeit
with a dingy complexion.
One more successful two-stage flight was performed. Then I decided to
try another three-stage flight. The 2nd booster was sanded out and
CA soaked to repair the burn damage. Much more care was taken in
preparing the stack of three motors. This time I put as much tape
on the 2nd motor as possible to get the best friction fit in its stage.
It flew at DARS' NTHP two weeks ago (circa Feb 2002). It drew positive
comments from the LCO, then successfully flew with both boosters separating
as desired.
It's still dingy, but I'll keep flying it. Even if it's not the
best looking rocket in my fleet, it still brings me great joy.
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Epilog: The rocket was lost just before Christmas
in 2002. While I had several kids helping track it, I had an inexperienced
boy on the upper stage, and I failed to coach him and to back him up -
my bad. While I was supporting the 2nd stage tracker, he lost track
of the upper stage. Man, I was bummed. But it was my fault.
I should have backed him up or let him track another stage.
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Tridget 2 - Another Three Stage Midget |
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After the first Tridget was lost, the boosters were recycled.
They had both seen several flights and were getting ragged, so I cut off
their fins and built new boosters along with an all new sustainer.
Here it is, ready to go.
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Below
are a couple of recent shots of the Tridget on the pad. In
neither case did I get a liftoff shot - all I got was smoke 
Sept 20, 2008

November 22, 2008
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12-21-2008
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