Tag: rocketry

Postal Express

Josh writes . . .

My uncle has been getting into and enjoying high-power rocketry for a while now, and I guess I’ve been a little inspired by his enjoyment. In hanging out with him, I got interested in it, too, and raided his scrap bin for some parts and ideas. While most people interested in rocketry would probably begin with any of the high-quality kits that are available, things seemed to line up for a scratch build for me.

I started with a standard 3-inch mailing tube from Office Depot. We wrapped it with a layer of fiberglass for strength. I built a motor mount out of a piece of “blue tube,” which is high-strength paper composite tubing made specifically for rocketry, and some rings cut out of plywood. Fins I cut from a composite called G10 (aka Garolite). The recovery harness was made from Kevlar and nylon webbing. I found an inexpensive surplus parachute online, and added a plastic nose cone. The whole thing was assembled with epoxy, and a little spray paint I had around prettied it up some.

In between work and other obligations, it took several build sessions over the course of six months or so to get the whole thing ready to fly, but finally I was both ready and available on the club’s regularly scheduled launch day. My uncle and I went out to the club’s launch site in the desert, and we saw several flights despite the conditions, which were on the windy side. One rocket, launched to about 2000 feet, drifted more than a mile on its parachute before touching down again. I was a little nervous, but I knew that my comparatively large, heavy rocket would not be flying as high, especially given that I was planning to fly on a comparatively small motor, so I decided to go for it.

The motor I had chosen was an H-238, and the simulation software estimated it would boost my rocket to about 980 feet. The delay packaged with the engine was rated for ten seconds, so we cut a little hole in it with a drill bit to shorten that a bit. The launch looked good, although the rocket seemed to wiggle a bit just after it cleared the launch rod – perhaps because a crosswind caught it. While I have seen lots of rockets go completely out of sight, the comparatively high weight and low power kept mine in sight the whole time. It had a smooth climb to apogee, then turned and started down again. I had a terrible moment or two when the rocket was clearly pointing toward the ground and falling, but the ejection charge finally did go off. The chute deployed, and the rocket came down smoothly after that. It touched down only a few hundred yards from the pad, and when I caught up to it, I could see by grooves in the sand that it had been dragged about eight feet by the wind. There was no damage, though, and the rocket is ready to fly again.

Plans are already under way for future flights and projects. This rocket, although it flew well, does have some design flaws that aren’t fixable, so the next one will benefit from what I learned in building and flying this one. I also have plans to install an electronic altimeter in the next one to control the ejection charge (actually, charges, plural, for dual deployment) and avoid the possibility of a bad landing. I also want to install a GPS receiver and radio beacon so I can find it if I lose sight of it. An on-board camera looks interesting, too.

Meanwhile, Out in the Desert . . .

Josh writes . . . 

All right, here are some pictures from yesterday’s (the 23rd) rocket-flying trip. It was breezy tending to windy at the launch site, but we did see several successful launches and recoveries. We also saw some suboptimal flights.

The desert southwest. This is pretty much it, for miles and miles. Remember the scene from The Right Stuff, when all the pilots moved to Edwards AFB to fly X-planes? That overstated the beauty of the area. This is near the lovely towns of North Edwards and Aerial Acres and California City.

This will become my uncle’s Level 3 certification rocket. The body tube is a 12″ concrete form, and the motor mount is the 4″ tube in the middle.

Here are the nose cone and the motor casing for the body tube above. The motor casing is 4″ in diameter and the nose cone is three feet long from tip to shoulder – that is, not including the portion that will fit inside the body tube.

Here’s the nose cone stacked on top of the body tube. Assembled height is about 7 feet. This will fly on a strong M motor. The expected thrust is about 750 pounds for something like 4 seconds. That’s my uncle with the ball cap in the background, assembling an I motor for his first launch of the day.

This is the first rocket of the day – a Sidewinder model built by another club member. The engine used in this one did not provide a lot of thrust early, so it did not clear the tower with enough speed to fly stably. As a result, it turned into the wind and proceeded roughly parallel to the ground for several thousand feet before crashing, shattering the body tube.

The second launch of the day – a Patriot model. This was the first high-power launch by the builder, and flew beautifully. The rocket was recovered successfully and undamaged. The builder earned his L1 certification.

This is my uncle’s I-powered rocket ready for its first launch. He had a J he could have used, but the I seemed like a better idea given the wind. According to the altimeter, this got to about 3600 feet. A perfect flight and recovery. This rocket is rigged for a dual deploy, with one charge firing at apogee to deploy the drogue and another firing at about 1200 feet AGL to open the main chute.

After recovery, he set this one up for a second launch, which was less successful. Although the drogue fired just fine, the main did not deploy and the rocket made a hard landing. There was some damage to the nose cone and the altimeter, but the rocket was otherwise unscathed and will fly again.

Another rocket from another builder on the pad. This one was rigged for a time delay, motor-based ejection. Launch was beautiful, but the ejection charge did not fire in time, and the rocket hit the ground nose first at high speed. Impact was maybe 1000 yards from the pad, and it hit so hard it was clearly audible.

And this is another way they come back to earth.