Using a core with an end burner has many draw backs for 'launching' a rocket,
here are a few:1) the core needs to be long enough to lift off the rocket (at
least a 3-1 thrust to weight ratio).2) the nozzle throat needs to be large
enough to prevent a CATO with the higher core burning pressure.3) that larger
size throat does not produce much thrust during the low pressure end burning
portion of the motor burn. and any nozzle throat erosion increases that
effect.4) the extra weight of the end burning propellant (just how long is it
to be?) means the core needs to be longer to lift off the rocket the end
burning portion of the motor turns out to be more smoke tracking than usable
thrust.
I've experimented with pouring multiple times on top of previously cast sugar
propellant with success. I've also made sugar grains with a > 2.5 cm/second
burn rate, something that could cause more thrust with an endburner but you
begin to realize simply using a larger diameter motor has the same effect. Here
is an example of a 'RaD' AP motor we made a few years ago with different
propellants in the same motor to reach different burn characteristics, in this
case, not so much burn rates but different colors:
RaD multicolor rocket propellant static test
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RaD multicolor rocket propellant static test
First test of the 'RaD' multicolor APCP solid propellant Bates grains. This
version produces Red-to-Whit... | |
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On Wednesday, September 6, 2017 12:58 PM, Richard Nakka
<richard.rocketry@xxxxxxxxx> wrote:
I've never attempted to make a sugar propellant end burner but I have often
given it thought. Here are some of my thoughts:
1) A conical propellant surface, rather than a flat surface, would greatly
increase burn area at no expense to the burn time.
2) PVC casing may be the ideal choice. I would expect ablation of the casing
surface would keep it reasonable cool, and bearing in mind at low pressure, a
thin wall is all that's needed so you can afford to ablate away much of the
wall. Also, PVC is very lightweight.
3) Brown iron oxide may be the key to getting sufficiently fast burn rate to
produce useful thrust.
http://www.nakka-rocketry.net/oxidex.html
Richard
On Wed, Sep 6, 2017 at 8:14 AM, Nikolai Nielsen <nielsen.nikolai86@xxxxxxxxx>
wrote:
has anyone dabbled with end burner motors? i know that it would cripple the
thrust that the quantity of fuel could produce but it seems like it should work.
Nikolai Nielsen
