NEFAR launch
January 13, 2007
Sugar Rush goes to Heaven

After it's demise in August, the Sugar Rush has risen from its ashes.   Actually, from its fins, the only parts left after it's geoterminal recovery.  

It is a ghostly white, for no reason other than I ran out of time.  The primer is white, and I did't get a chance to spray it pink again.  

I have finally gotten it together to give the long smoke grain another try.  When Jon offered to build this motor for me, I made an odd request - to have a 2-1/4th inch well to allow the use of an extra-long smoke grain.  It was tested once, back in April when Jon was here, and failed.  The smoke grain was inserted into the cavity with a number of O-rings to support it.  Getting it in was a bit of a struggle, since the O-rings were holding the pressure of the air in front of the grain, and trying to push it back out.  During the motor burn, the grain came out and partially blocked the nozzle.  Motor casing was belled a little at the head end, but otherwise undamaged.  Jon repaired the casing and sent it back to me, but I realized I needed a positive way to retain the smoke grain.

So I sent Jon the header and he cut a snap-ring groove in it.  At the hardware store, I found a snap ring and a bushing that fits well, and we are in beeswax.  

The smoke grain itself is molded in a 38mm casting tube, which fits the delay well nicely.  It is filled with dark, slow rcandy the same batch used as propellant in this load, but catalyzed with 0.5% RIO and 10% fine Ti flakes to help it keep burning.  Burn rate at 1 atmosphere is 10 seconds per linear inch.  So this 2-inch grain should offer about 15 seconds of smoke - the "discount" because the first web-thickness (about 9/16ths inch) of the smoke grain will be burning under pressure, thus much faster than it's 1-atmosphere rate.  It will go away in the time it takes the primary propellant to burn, about 1.3 seconds.  

smoke grain before flight

The end of the grain is covered with a layer of aluminum foil duct tape, to keep it sealed against the air.

Cutting through foil tape to expose propellant

I simply cut through the tape and remove most of it, to expose the smoke-grain propellant to the primary propellant flame.

Foil-tape packaged propellant load

I've packed the propellant load in a foil package too.  Click Here to see a movie of how nicely it unpacks to go into the motor casing.

The propellant for this load is an assemblage of remnants and scraps from previous batches, some dating back to 2004.  One of the larger remnants was a very dark, slow-burning batch, from which the assemblage took its character.  Burn rate was 20 seconds per linear inch at one atmosphere, barely continuous.  I did not endeavor to speed it up for the main propellant, thinking that it would just make for a longer-burning motor than usual.  It did. I was sure it would be slow to ignite, so I made a fuse paper ignitor with a good bit of Ti in it.  Also packed the lower grain core with fuse paper out at the launch pad, to help it build up pressure.  Ignition was slow anyway.  But eventually it got going and the rocket flew well.

Teresa at launch pad

I'm sure you are tired of seeing me at the pad.  So here is Teresa!

Sugar Rush Liftoff

Click Here for a video of this launch (5 meg .wmv file, 37 seconds of video)

Ignitor fires -first smoke seen   0 seconds
Liftoff   1.8 seconds (a rather long ignition delay, probably due to slow-burning propellant)
Burnout1.8 seconds after liftoff (estimated from video)
Apogee10 seconds after liftoff?  (I'm really not sure - hard for me to judge these things, especially when rocket arcs over in wind.)
Drogue ejection12 seconds after liftoff
Smoke ends27 seconds after liftoff
Landing 53 seconds after liftoff.

She's down!

Fortunately, the drogue fired at apogee or a little after.  The main did not deploy.  The rocket landed hard, but was not badly damaged and can be easily repaired.  The G-Wiz altimeter reported an apogee of 5400 feet, which I think is incorrect.  Looks like it might have gone to 2500, maybe 3000 feet, but not much more.  Peraps the altimeter bumped its head on landing.

But why the failure?  

Ejection charge packet,  Ejection Charge Packet

Upon opening the main parachute compartment, I noticed that the ejection charge packet what puffed up like a little balloon, but not opened.  What gives?

This was a field-improvised ejection packet.  I'd forgotten to make one the night before the launch, but had everything at the launch to assemble one.  It is not unlike those I've used in many previous launches.  

Opened, I see that the powder has not burned.  

Opened ejection charge packet

But the e-match which was inside that packet shows definite signs of heat

E-match  E-Match, opened

Opened, it is clear that the e-match fired, but failed to ignite the packet powder.

Here is is, all 2 grams of it:

Unburned ejection powder

So what to do, what to do...

First, I am astonished that the e-match could have fired and failed to ignite the powder in the packet.  (That seems as unlikely as the Gators winning a football championship : )  But I've been astounded before, and chances are good I'll be astounded a few more times before my life is up.  I hope so, anyway.  

Most folks will say "just use black powder."  Well, that is a very kind suggestion, and I like black powder.  I often make it myself.  But I want to develop smokeless powder ejection to work effectively.  This is experimental rocketry.  Red Dot has worked with good reliability up to this point, as seen in several series of ground tests (2001) (2002) (2004) and in several dozen flight tests over the last three years.  

Smokeless powder offers several advantages over black powder.  It doesn't burn up parachutes or shock cords, for one thing.  It doesn't smell bad for another.  It doesn't corrode metals or electronics either.  It has inexhorable power, but exerts it gently.  And black powder is getting difficult to find in many spots, where smokeless powders are readily available.   So I believe that smokeless powder ejection is worthy of development, and am willing to endure a little risk in that regard.

On with the show.  The most obvious solutions are to increase the amount of powder in the e-match so that it spits out more fire, and to make the packet smaller and tighter, so that the main charge is held in close proximity to the e-match.  Ted Novak and Jon Carter were kind enough to send me articles relevant to this - Scott Alexson's page on smokeless powders, and Tony and AJ's page on high-altitude deployment, with some clever ideas for holding things together long enough for ignition to happen.

 There are many other options that occur to me, but it seems to me that giving the e-match a little more powder, and putting the main charge in a tighter package should do the trick, at least for the low-altitude flights I do.  I'd rather stay with the simplest thing that works reliably, so I'll test these first.

What did work well was the long smoke grain.  It produced smoke to apogee and well afterward.  

smoke grain after launch

So the moral of this story?  Some things work and some don't.  And sometimes things that don't do, others that do, don't.  I hope to get this all straightened out one day soon, and would appreciate any assistance, or interesting distractions.

Jimmy Yawn
Recrystallized Rocketry