Thanks for the reply Rick. Lots of good info. I think I asked this a few
years ago on the sugpro list, but in regards to the plug in the dual
pulse motor I was wondering if there was something that would melt/burn
away at a low enough temp that would not start the second grain,
allowing it to be lit by a separate ignition source in the head end like
a regular core burner. Didn't really get any answers to something that
would protect the second grain from the first grain burn, but would
still dissolve/melt/burn away to allow the ignition of the second motor.
I know SS2S experimented with a separate bulkhead but I was thinking
something more along the lines of something melting away.
Shawn
On 2017-09-06 20:46, Rick Maschek wrote:
You are correct Shawn that was an end burner that was over a minute. The
longest core burner we've done so far is 18 seconds.
With the multiple pours of sugar propellant, that started when we cast grains
for Sugar Shot with a bottom plug 3/8" thick and used another for the
compression on top. When the grains were solidified, we pulled off the
compression ring and 'topped off' the grains to get another 1/4-3/8"
propellant in the grains. Testing showed the bond between the previous pour
and the new pour was strong.
We also did some 'Unigrains' made by casting one grain, pulling the mandrel
almost out, adding another casting tube and pouring more propellant on top of
the previous grain, pulling the mandrel almost out, adding another casting
tube and pouring more propellant, etc so that we essentially ended up with
one long grain without the segment gaps of BATES grains.
On the RaD motors, we cast the AP in layers that surrounded the previous AP
both on the two ends and in the core. Imagine what the propellant (web) looks
like in the BATES grain 1 second after ignition. That was the red propellant
that burned away. Now imagine what the propellant looks like after 2 seconds
in the grain. That was the white propellant that just burned away. The
remainder left is the blue propellant. The blue propellant was cast first
using a large core and thick end plug. After that was cured, the large
diameter mandrel was pulled and a medium diameter mandrel inserted into a
medium end plug and the white propellant cast over the blue. That process was
then repeated with a small diameter mandrel and the red propellant was cast
over the white. Needless to say, it was a lot of work. We've done two colors
since but have not done the three colors again.
If you recall how the Sugar Shot 'Dual Pulse' motor worked, I also tried
casting such a motor in a single long tube by pouring one third the length,
pulling the mandrel, inserting a flammable 'plug' that would burn away,
casting another third, pull the mandrel, inserting a second plug on that and
then one last pour on top of that. The desired effect was for a 'pseudo' 3
stage rocket in a single long motor. It didn't work well because after
burning through the flammable plugs separating the sections, the 2nd and 3rd
chuffed from being ignited at the nozzle end.
On Wednesday, September 6, 2017 3:50 PM, "shawn.mchatten@xxxxxxxxxxx"
<shawn.mchatten@xxxxxxxxxxx> wrote:
Rick, below you mention the longest CORE burner you have ever done is one
minute. Did you really mean end burner and if not then how big was that motor
and what was the burn rate of the fuel? That's a LONG burn for a core burner.
In one of your other posts you mention that you have experimented with
multiple pours of sugar into one grain. Did you cast at the end of each grain
or along the length of the grain (either inside the original core or around
the outside? Also did you use any adhesive/glue or just rely on the new batch
of propellant "melting into" and forming a good bond to the earlier cast?
thanks
Shawn
On 2017-09-06 15:13, Rick Maschek wrote:
I've built several for two applications, one is for gliders where you don't
need lots of thrust and the other for a sustainer/dart to give just enough
to keep up the momentum.
If you don't require lots of pressure/high thrust, it can be easier on a
motor case than traditional BATES grains if the burn is less than ten
seconds since it is a single grain and does not have unprotected segment
spaces typical with BATES grains that would requires a liner. Longest core
burner I've done was just over one minute using KNSB.
I tried making sugar endburners for rockets. They require a super light
rocket and a core on the nozzle end for enough thrust to get the rocket
moving that transitions to end burning once the cored area burns away. The
same effect can be done with using cored and non cored BATES grains.
Sometimes I will use a coreless grain next to the bulkhead if I want
tracking smoke from my sugar motor, just make sure to inhibit the end next
to the bulkhead.
Attached is an example of what the thrust profile would look like with a
cored start that transitions to end burning.
On Wednesday, September 6, 2017 6:14 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