Tuesday, July 27, 2010

Additional launch Photos

As usual, my good friend James took some nice photos on launch day. I really like this one looking down the launch tower. You can see a few more photos on his blog.

Sunday, July 18, 2010

Launch Day

I had a lot of fun at the launch. The new motor performed really well . The flight went well and the chute was deployed at apogee. Unfortunately the parachute separated from the rocket and it came in ballistic. The good news is that most of the motor survived and may give some clue as to what caused the recovery failure...more on that later. I don't think many of the AIAA members had ever seen a "sugar" motor before and I think a lot of them were surprised and impressed.
Many of the competing teams seemed to have a tough time of it with several launch pad mishaps and a few in flight failures. By the afternoon though there had been some nicely executed flights. Overall it was a good day and it was pretty cool to see so many people participating. There are a handful of other photos here.

Tuesday, July 13, 2010

Launch update

Change of plans. Once I started looking into what actually had to be done to prep the camera rocket for this weekends launch, I realized that there was actually more to do than I had anticipated. Coupled with the fact that I'm not going to be able to go out early to cast the the propellant for that larger motor it became apparent that I needed a plan B. I quickly decided that I could modify an older/retired aeroshell to fit the 2.375" motor that I have been working on. The initial static test of that motor ended abruptly, but I modified the design and it's been ready to be re-tested for some time now. Finding the time has been the issue so plan B seems like the way to go; I get to fly something and test the motor. I still need to document the changes to the 2.375" motor, but basically three things changed: I went back to a propellant formulation that I know well (60/40 KNSB), I redesigned the core to be stepped to help address any erosive burning issues, and I'm using a smaller igniter. I chose the 60/40 ratio to help reduce the chamber pressure as KNSB has a higher burn rate then the KNERSB formulation that the original motor test used. At least in theory. While the ambient burn rate that I measured fell in between KNSB and KNER, I'm not convinced that the burn rate at operating pressure behaved the same way. The initial testing of the KNERSB propellant didn't seem to exhibit some of the same characteristics of KNER propellant, namely difficulty with ignition or slow start up. The failure mode was over pressurization which resulted in the forward bulkhead being blown out. I felt that the last test had too many new things going on: new propellant formula, High L/d. Having made changes to address both, I feel confident enough to try a flight test. Hey, that's why they call it experimental rocketry!
Anyway, I chopped the black and orange rocket into pieces. Once I get the pieces put back together it should look basically the same from the outside. It's kind of exciting refurbishing an old rocket that probably last flew in 2002-2003. The largest motor that boosted this aeroshell was a K-class motor and the 2.375" motor is an L-class motor, so it's a bit of a step up in thrust. Parachute deployment will be handled with a timer. I'm leaving out the more expensive altimeter because of the untested nature of the motor, but I am going to include a video camera because you want video even if things go wrong. Pictures of the new rocket to come soon.

Tuesday, July 6, 2010

Upcoming rocket launch

The Reaction research Society's next launch is scheduled for the 17-18th of this month. This particular launch is specifically set up for the American Institute Aeronautics and Astronautics (AIAA) Young Engineers competition. I found this description of the competition online. In addition to the competition, members are encouraged to participate in the launch with their own projects. My latest motor project (the high L/d motor) is ready for another static test, but I really feel like flying something. Once I read a description of the vehicles they are planning to fly (four inch diameter with an expected altitude of 15,000 ft), I decided to fly the latest version of my camera rocket (four inch vehicle with an expected altitude of 18,000 ft). You can see the latest version here and the camera and overall configuration here. My intent was to fly this quite a while ago, but things got busy and I never launched it.

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". OK...so 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!