Thursday, January 7, 2010

MISSILES: Up on Solid Fuel

MISSILES: Up on Solid Fuel

I came across this short article from 1958 about Thiokols entry into the field of rocketry. I like this sentence "By 1953 Thiokol had produced solid-fuel engines, ie., basically cylinders packed with the fuel, for the first full-scale Army test missiles."

Wednesday, January 6, 2010

New Sugar

I ordered a new batch of Erythritol. The previous brand that I used was Zsweet and the new stuff that I ordered is NowFoods. I have used Sorbitol from NowFoods before with very good results. It'll be interesting to see if there are any differences in the casting of the two different brands. I'll start by trying a straight KN/ER segment per the original design and see how that casts.

I've also made a new bulkhead and motor casing. The casing is identical, but the bulkhead is slightly different in that it has provisions for both the igniter and the pressure port. I had some concerns about the amount of wire that was in the motor at the last firing. Initially I thought that maybe the igniter had gotten bunched up and wasn't able to clear the nozzle thereby causing the over pressurization. We found the igniter shortly after the test though and it was clear that it hadn't plugged the nozzle and had been cleanly ejected from the motor. But why take any chances.

Monday, January 4, 2010

Amateur Experimental vs High Powered Rocketry

The other day someone that knew I was "into" rocketry said, "I saw this show on TV where these guys put rocket motors onto a ten foot mock up of Dorothy's house from the Wizard of Oz and shot it into the air". I saw this show, it was entertaining, but that's not the type of rocketry that I'm "into". The above example falls into the High Powered Rocketry or HPR category for me. To be fair, it is at one extreme end of the HPR spectrum. I'm not at all against HPR, it's just doesn't really excite me. Assembling a kit, commercial motor, propellant, and flying it doesn't teach you the engineering of rocketry or at least it doesn't take you very far below the surface. I know that some HPR launches have "experimental" days that allow people to fly motors that they have made with propellant that they have cast themselves, but even at those launches most of the motors are of a very similar design and most of the propellant is just a slightly different variation of the same stuff.
The photo above is of a two stage vehicle built and flown by Bill Claybaugh at the RRS last October. The booster is a cluster of four RRS "class" motors and the sustainer is a single "class" motor. The class motor was developed by the RRS to use for their introductory solid propellant class that they've taught for a number of years. It's been a while since I took the class, but as I recall the motor produces around 300lbs. of thrust for three seconds, so the booster propelled this thing out of the tower with 1200lbs. of thrust. I don't think this is the most interesting amateur rocket that I've seen, but it would certainly look right at home in the pages of Richard Morrow's "Small Sounding Rockets". I can't help but think that the same five motors at a HPR event would be lazily propelling a scaled-up version of some Estes model rocket to three or four hundred feet.
It's not unusual to go to a launch at the RRS or FAR and see half a dozen rockets fly, far fewer than you would see at a typical HPR event. The difference is that those six rockets would likely be completely different from each other. Solids, liquids, Lox/Kerosene, Hydrogen Peroxide, Steam, Zinc/Sulfur, Sugar, HTPB, and on and on. Now that, I'm into!