Other Diaries

Jeff Duntemann

Michael Covington

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ARCHIVES

• Comet McNaught
• First images w/ Vixen scope
• Apollo 11 landing site imaged
• Excellent Saturn image

Oct - Nov - Dec 2006

Technical tangent: that means it has a total impulse somewhere between 20 and 40 Newton-seconds; for you non-rocket-scientists, that means if it's rated at 20 Ns, it kicks for, say, 20 Newtons for one second, or 2 Newtons for 10 seconds, etc. What's a Newton? It's the metric unit of force. A Newton is 0.224 pounds force. So think of 20 Ns as 4.5 lbf-sec. The Estes E engines are listed as E9-4, the E is the impulse class (each letter class has twice the impulse of the one before. Normally Estes engines fall at the top of the impulse range for each letter, but according to these specs from the National Association of Rocketry, this E falls midrange, and puts out about 28.5 Ns. (The D engines are 10 to 20 Ns, the Cs are 5 to 10, etc). The "9" in E9-4 is the average thrust in Newtons for whatever time they burn; so we can get the total burn time as 28.5/9 ~ 3 sec. The "4" designates the delay before it fires its ejection charge to pop the parachute. Now back to our regularly scheduled programming.

The old, smaller, original Estes "Interceptor" was the model rocket that every kid wanted when I was in high school – but few of us ever saw one, much less built or fired one. It was produced from 1971 to 1980. At its introduction, it was prominently featured on the cover of the 1971 Estes catalog, which I still have and treasure in mint condition. (Mine's in much better shape than that). Estes recently re-issued the original Interceptor, and it was such a hit that they came up with a supersized version. I mean, that ship has more pointy appendages and razor-edged things than Sigourney Weaver's "Alien" in a butcher shop. It's a dramatic contrast to most of Estes' current offerings, which look pretty generic. Not many scale models to speak of in the bunch, much less fantasy ships like this.

We had our hands full getting the things built between Christmas and the launch date, Dec. 31. And Jeff had other things to worry about so he didn't get his finished, but we concentrated on mine. As it was, we finished epoxying the fins on the night before, and there just wasn't time to apply the incredible decals (three sheets of markings!) before launch. As a token gesture to the spirit of "scale" modeling I painted the "cockpit glazing" black and the molded styrene wingtip pods dayglo red, and left it at that.

Here's the finished rocket

And here's Jeff holding it to give some sense of how big this is.

For a sample of what the pros can do with this kit, have a look at the prototype, built by an Estes employee months before it was released. There was a lot of chatter on the Ye Olde Rocket Forum bulletin board, and this Estes employee, using the handle "Roguepink," chimed in. His detailing hints are in post #30, on p. 3. And positively spectacular photos of his own prototype rocket are can be seen in top view, bottom view, nose detail, and wing detail.

Enough yak. How does it fly? Well, the short version is, just fine. Jeff already reported on the events of the day on his own web site. I used up three Estes E9-4 engines and had perfect flights every time. The last one just seemed to go straighter and higher, and it seemed to take a lot longer before the 'chute popped, then the wind carried it way out beyond the highway that runs near the launch site. I checked it on Google Earth later, it drifted about a quarter mile. But, the rocket was undamaged by any of this. I really thought the plastic pods were begging to snap off, but they were fine.

Here's the rocket on the launching pad, and a view of Ernie's launch control panel.

Here's a typical scene of a landed rocket.

I also brought out some rockets from California: my old (circa 1990?) Estes semi-scale "Phoenix" air-to-air missile, powered by a D12-3 motor (the Phoenix was the reason for the Navy's F-14 Tomcat – a big missile with more than 100 mile range against anything that might try to attack a carrier group), and a re-creation of my very first rocket built back in 1969, an Estes Astron Beta (two stage, but I only flew it single stage on this windy day, successfully as I had all those years ago with the original). In comparison, the Beta looks tiny today, but back then, we had a lot more two-stage rockets, and a much larger selection of zero-delay engines for first stages.

I didn't have a chance to film the Interceptor launches, since I was the one pushing the button, but I did record the Phoenix. Here it is on the pad

and post-flight. One lower fin cracked, but that has since been fixed with Elmer's yellow wood glue.

I spliced two of the videos together using AVIDemux 2.4 to convert the .mov files to .avi, and the older Zwei-Stein, V3.01, to do some elementary editing. I don't like the Zwei-Stein interface, but I tried to install Microsoft's Movie Maker for Win 2K and it is total junk. (It may work just fine, and with more features, in XP and Vista, but I won't allow those on my system). Click on the thumbnail below to start a .wmv video in a new window. That's Ernie nearest the camera, Jeff with his finger on the button, and, later, playing the role of recovery helicopter.

Fortunately, a couple of other members of COSROCS got word of the short-notice launch and came out on this sunny, cold, blustery Colorado day, so Jeff and I didn't feel quite so guilty about talking Ernie into coming out. All told, the crew had a total of about a dozen launches, all successful, all rockets recovered, none lost or wrecked. It's a good thing we moved the date up from the previous Friday, because I just plain would not have had the Interceptor done.

And what am I doing now in the way of rockets? Building a replica of the Estes parachute-recovery Boeing Bomarc.And after that, probably the Nike-Ajax on that same page. Someday, I might pop for the big Madcow Rocketry Bomarc. I like scale models.

The problem is, I have to go to Colorado to launch these. In California, "security theater" has become "theater of the absurd." I used to launch from the schoolyard down the street, and higher-power rockets from Mile Square Park in Fountain Valley, but that's now YAGC (Yet Another Golf Course; Orange County needs more golf courses!) The people who control these things promised an alternative site for the rocket, R/C cars, and R/C planes that had used the old abandoned runways at Mile Square, but thanks to 9/11, they no longer have to keep their promises. "Well, the whole world has changed, don't you see..." No, I don't. For an example of what the many would-be rocket amateurs among ten million or so people in the Los Angeles Basin have to put up with, see this site and this flyer.

Field will accommodate up to a single G motor (* except during April, May & early June). There are trees and a lake down wind from our launch and recovery area, so you should use the lowest power motors possible to recover your model rockets safely. * During April, May and early June, because of the smaller launch and recovery area, the power limit will be very low. You ONLY be allowed to use the lowest power motor that can be safely used in any model up to a C motor maximum for large and heavy models. Medium sized models will be limited to A or B motors. Small models will typically use 1/4A, 1/2A or A motors. The intent is to limit the maximum altitude to about 500 feet for streamer recovery models and about 350 feet for parachute recovery models.

With those restrictions – use smallest possible motor, 350 ft. max – what's the point? Catapulting lawn darts with a rubberband slingshot would be more rewarding.

Model Rocketry links

Lately, I've been busy building model rockets. Some of the results may be seen on Jeff Duntemann's web pages. (I hope to add more of my own on this "happening" but I've been too busy to process the videos etc.)

But, in the course of reliving my pre-adolescent pursuits of launching model rockets, I assembled a large number of useful links for the similarly afflicted. Tech info, vintage Estes catalogs, plans, and parts lists, modern sources for building materials... just go here or click on the navigation box at left.