Monday, September 29, 2014

Dextrose Testing

So the TR-1 didn't go the way that I had hoped but it wasn't all bad.  It reinforced the idea that making even a small change to your plan should be very carefully considered.  A lesson worth reinforcement.  The damage was not nearly as bad as it could have been and was, for the most part,  limited to the casing, pressure gauge , and the bulkhead.  The bulkhead will need to be re-drilled and tapped but there is enough space left to do that.  The Casing is relatively easy to fabricate and I have already procured new stock.  The nozzle surprisingly was relatively unscathed and after removing a few bolts that had been sheared off in it, it's good to go.   I have continued going through all of my boxes of rocket and rocket related stuff in an effort to organize my workspace and found that I actually have enough sorbitol on hand to cast this motor.  I will take a more stepped approach geared towards a full scale test before proceeding with another full on motor test.  Hopefully this winter around December or January.  The first step is a smaller single grain test motor sized for the 4" diameter grain segment.

In addition to prepping the TR-1 motor for another test I will be doing some smaller scale testing utilizing Dextrose.   I plan to use the 2.375" motor that designed, tested, and flew back in 2009/10.

Originally this motor was designed for sorbitol based propellant.  Ultimately it was fired with KNSB based propellant and a 50/50 sorbitol/Erythitol mix based propellant.   I have constructed a four segment casing for this motor which would produce a low MEOP of 600psi with KNSB and 950psi with KNDX.
SRM screen grab


Monday, September 22, 2014

TR-1 Cato

Theo and I tested the TR-1 motor on Saturday and unfortunately suffered a cato.  It was an impressive sounding motor for that first few milliseconds though.  Apparently I should have rethought my decision to use Dextrose in place of Sorbitol.  On paper the change seemed fine but I had limited experience with Dextrose and never in something of this size.  The actual casting of the grain segments went fine but I experienced some slumping in two of segments that I cast.  At the time I decided that the slumping was due to having removed the segments in question too soon from the mould.  I believe that segment slump either contributed to or was the direct cause of the cato.  Fortunately I had cast an extra segment and at the end of the day, long after the firing, that segment which had been stored in the same conditions as some similarly sized Sorbitol segments that Rick had cast had slumped.  The sorbitol segments remained fine.  The dextrose segment had slumped so severely that the core was essentially gone.  I know of many folks that have use dextrose based propellants with no reports of slumping so I’m unclear of the reason, maybe the size of the segments?  For now I will switch back to Sorbitol in the TR-1 motor and save the dextrose for some much smaller scale motor testing.  We had a good time regardless.  The guys at FAR were very helpful, and the site had grown quite a bit since our last visit there some three years or so ago.  Rick Maschek also provided lots of assitance and camera work.  Rick also had a nice firing of a KNSB motor with a Double-D grain configuration.  The third photo is of Rick's firing.  The last photo is af an  AP motor firing that anomther FAR member (Erik, I think) conducted.


Thursday, September 18, 2014

Loki Booster

I got this Loki booster a while ago.  It's a little banged up (the fins are slightly bent) but overall it's in pretty good shape since it's probably around 60 years old.  This one was never fired or filled with propellant. The transition section doesn't have the roll pins installed and can be removed to revel the interior of the motor.  It is also possible to see the rubber liner that protects the thin aluminum motor casing from the heat of combustion.  The black spots seen at the base of the motor and on the nozzle retaining ring seem to be the same material as the liner.  I'm not sure what the pin on the top of the transition section is for; it's spring loaded and maybe it's meant to help ensure a clean dart separation. The pin on the side was, I believe, to keep the dart from spinning as the rocket was spin stabilized.  It's cool to think that this small booster was capable of getting a dart up to 34 miles...

Monday, September 15, 2014

TR-1 Test Fit

Tested the fit of the nozzle and bulkhead with o-rings installed.  Everything fit together nicely and no adjustments were made.

Thursday, September 11, 2014

TR-1 Casting Stuff

Delrin coring rods are cut to length and everything fits together nicely.

Wednesday, September 10, 2014


The Dextrose from Lucky Vitamin has arrived.  I want to do a little testing with it since I don't have a lot of experience with Dextrose.  At least not nearly as much as with Sorbitol or Sucrose. 

Tuesday, September 9, 2014

TR-1 Motor Update

McMaster-Carr order arrived yesterday and included the o-rings, Delrin rod, screws, and pressure gauge.  I didn't get a chance to assemble the motor for a final test fit, but now that I have the o-rings that's next on the list of things to do.  The Delrin rod for casting the core in the propellant segments was a perfect fit in the casting base, so I'll just need to cut to length.  Delrin would be an ideal choice for the casting bases too, but the stock I need would be around $60 for two bases, so I'll stick with wood for now.