The Rockets

Errthum-T

For testing purposes, I use a Errthum-T series rocket. It is simply a 16oz bottle with the top of another taped on for the noze. There is no chute and water is added into the nose to make it top heavy and more stable. This rocket is only used for pressure testing and launch mechanism testing. It is shown here on the launch pad during a test.

Errthum-1

I had built a rocket that was to be my primary rocket, the Errthum-1. But it had several flaws and only survived 1 launch. It was very unstable due to the low surface area and placement of the fins. The fins did not cut enough air and were not far enough behind the center of gravity. Upon lift off it veered before stabilizing. This put in an arching flight path. Normally this is not critical, but the Errthum-1 utilized a parachute deployment system called a speed flap. This is a hinged flap along the body that hooks into the nose which is sprung by a rubber band. As the rocket moves, the air stream holds the flap in place which in turn hold on the nose. But when the rocket slows, the flap flips up releasing the nose and popping the chute. However, in my case it never slowed until it hit the ground. Some claim it is the best low tech solution for deploying a chute, but I don't agree with them at this time. :) Click for image on the launch pad, speed flap in activated position, nose cone hanging to side.

Errthum-2

The Errthum-2 series was originally built for my twin boys so they would leave my rocket alone. However, they ended up being the better designed rocket. The rocket's core is a 24 oz bottle and it is held together with duct tape. Some don't advise using duct tape as it is heavy, but I am not going for any records and it is great for modifications in the field. This rocket is very stable with the cylindrical fin well behind the center of gravity. On one launch the nose cone had fallen off early and I saw the rocket actually tumble once and then re-stabilize and continue straight up. It uses the simplest of all parachute deployment systes, FOAA (Falls Off At Apogee). The nose containing the chute just sits on the top of the rocket. When the rocket reaches its full height and turns it's nose towards the earth, the cone falls off and the slip stream pulls out the chute.

In early flights of this rocket (mod-1 and mod-2) the nose cone would fall off prematurely in mid flight from the effects of the blast off. Dispite this they regurally obtained 150 feet. The chute itself is made out of material I highly advise using. It is a fabric typically used in the making of prom dresses. It is light weight, doesn't soak up water and naturally tries to flatten. Also, it is bright and shiny and thus easy to spot. The Errthum-2 differs in most rockets in that the parachute is connected to the tail. This allows the nose and stronger point of the rocket to take the brunt of landing. On this rocket, the parachute is connected to a ring that acutally slides down the fin support so that when stowed there is less shroad exposed. The nose after deployment separates completely and falls to the ground. This is the most sure way that the thing won't disrupt the chute in anyway.

The mod-3 design has improved on the early deployment problem. Mod-1 just had the nose sitting on top while mod-2 added duct tape around the base in an attempt to hold it there longer. Mod-3 takes that a step further and uses a rigid shroud that the nose fits in made from pop bottle plastic. It has a slit that allows the parachute shroad to be connected to the fin support (so it can slide to the back). A ribbon was added to the nose cone to assist in finding it after launch since it is not connected to the rocket. This design has worked well and is the pinnicle of this model.







Errthum-3

The Errthum-3 is designed to test a theory that may give more boost to water rockets with the same pressure and amount of water. The core of the design is a removeable venturi chamber. The venturi mixes the air and water before it leaves the rocket. I came up with this after studying the 4 stages effecting the rocket's flight. The first describes the launch as the rocket slides up the booster rod. The second and longest stage is when the water is being forced out. The third and shortest stage is when the water is about to run out and the remaining air vaporizes it as it leaves the rocket. The final push comes when the remaining air pulses out. As it turns out, the third stage offers the most push. Remember that our force is derived from throwing mass backwards quickly. The vaprized water leaves the rocket faster than when it is liquid. So, the hope is that we will ge more boost by mixing pressurized air with the water, vaporizing it as it leaves. As stated the veturi chamber is removeable, so we can compare results to a traditional launch.

This rocket is still in development as of Spring 2004. After its intial flights this summer, I'll post some pictures.


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