Chute Release

 Chute Release is a small electronic device that holds your rocket parachute closed until it drops to an altitude that you choose. This is great for windy days and small fields when normally your rocket would drift too far while descending under parachute.

Simply wrap the elastic around your folded parachute and snap it into the other side of the release, then set the altitude from 100 to 1000 feet (30-300 meters) and you are ready for launch.

How Does It Work?

Chute Release uses an elastic band which wraps around the parachute and has a pin which snaps in place on the other side of Chute Release. Chute Release can sense altitude using a highly accurate atmospheric pressure sensor. When the rocket descends to the chosen altitude, an electronic servo releases the pin and lets the parachute open. Chute Release is powered by a built-in rechargeable battery that can be recharged from any USB port (cable included).

Chute Release is constructed of incredibly strong polycarbonate plastic to stand up to ejection charges and impacts. The mechanicals are constructed of precisely-machined aircraft aluminum, Teflon coated so that they need no lubrication.

What’s Included

Chute Release
USB recharging cable
Two(2) pins (primary and spare)
Ten(10) regular elastic bands 1-3/4 x 1/4″
Five(5) large elastic bands 3-1/2 x 3/8″
Two(2) tethers, 200 lb strength

How to Use It

Before launch, you fold your parachute up, attach the tether, and wrap Chute Release’s elastic band around the parachute, clipping the pin into the other side of Chute Release. Your parachute will now stay folded until Chute Release lets it go.

Your parachute is ejected at the top of your flight as usual by your motor’s ejection charge, but Chute Release holds your parachute closed until your rocket falls to the altitude that you chose as the release altitude.

Shown below is a typical flight recorded by an AltimeterThree which was riding along in the rocket. You can see from the altitude graph that the flight reached 880 feet and then fell until Chute Release released the parachute at 200 feet. Notice that it took about 50 feet after release for this parachute to fully open and slow the rocket to final landing speed which it reached at about 150 feet above the ground.

It typically takes 50 to 150 feet (15-45 meters) to slow your rocket to landing speed, but this depends very much on how your fold your chute. An instrument like AltimeterThree is a valuable tool for examining and improving your techniques, because it shows clearly what happened during flight.

Interesting fact: the release altitude does not affect the landing speed. In other words, imagine a rocket that opens its main chute at 800 feet on one flight, then 200 feet on the next flight. Both flights will land at the same speed. In both cases, the rocket quickly slows to landing speed within a second or two of opening, then drifts at landing speed until it touches down. Higher release altitudes give you more time to spot your parachute, and sometimes you want the rocket to drift to a certain spot on your field to avoid obstacles. Lower release altitudes (once you are confident in your folding techniques) can reduce wind drift.

Tips for Parachute Folding

Proper parachute folding and loading is always critical to a successful flight, and you probably already have a favorite technique. Chute Release introduces two new factors that you have to consider:

Chute Release takes up space
Chute Release can help hold your chute in a tight bundle

There is no “one way” to fold and pack your chute. It depends too much on the chute you’re using and the amount of space you have in your rocket. For instance, if you are packing your chute for a smaller rocket that is < 41 mm in diameter (such as a Big Bertha size rocket), you will not be able to wrap Chute Release around your entire parachute. Instead, you’ll have to just wrap it around the bottom of your chute, and then fold or roll the rest of your chute up outside of Chute Release.

You should experiment before you to go a launch, and practice packing and loading your rocket at home. For smaller rockets, load the chute and then see if you can eject it using your own breath by blowing in the engine mount.
Shown here is a video demonstrating a folding approach that wraps the parachute around the shroud lines to avoid tangling.