These tutorials show you how to build some of the components we use on our rockets. While it may not always be possible to reproduce these components exactly, many of the designs can be customized based on the materials you have available.

For a full list of all construction tutorials go to the Construction Index.

This tutorial describes a simple parachute deployment mechanism for multi-stage rockets or rockets with boosters. This mechanism is activated by the staging event and therefore only appropriate for the lower stages and boosters. This mechanism can be used with virtually any staging mechanism. For a parachute deployment mechanism for the upper most stage see the side deploy mechanism.

How it works

The parachute on the lower stage is held in place by two doors made of PET plastic. The doors are kept locked with a pin in a similar way a hinge pin holds the two halves of a hinge together. A wire connected to the upper stage is threaded into the doors and holds them together. When staging occurs the wire is pulled out and the doors are free to open and release the parachute.

Tools and Materials

- 1 x PET bottle
- Wire
- Paper clip
- Tape
- Craft knife
- Scissors
- Long nose pliers

Procedure

	1.	Wash out a PET bottle and remove the label. You can remove the label glue with a little bit of mineral turpentine.
	2.	Cut about a 5 cm wide strip from the middle section of the bottle. Discard the top and bottom of the bottle. The width of the strip is not really important, it just needs to be wide enough for your parachute.
	3.	Cut it into two halves. The length of these again isn't very important and will depend on the size of your parachute.
	4.	Straighten the strips out by bending them backwards. This will help them spring open when released. They don't have to be perfectly straight. You can also reverse them so that they will spring open even more. Bend the end of each of the strips back about 90 degrees about 1 cm from the end.
	5.	Now bend the ends over to make a small loop. The tighter you make this loop the better. It can be a little tricky so take your time. Using pliers to shape the plastic makes this a lot easier. Tape the ends down temporarily and mark out a set of points near the loop. Also mark out where to make the cuts in the loops. How many cuts you have will depend on the width of your strip, but the cuts should be about 1cm apart. The points next to the loop should be about 5mm apart.
	6.	Straighten out a paperclip and then heat the end over a flame. Make sure you use pliers when you do this as the paperclip will get too hot.
	7.	Now use it to drill holes in the marked positions near the loop. Don't make the paperclip too hot otherwise it will make the holes too big. The paperclip cools down quickly so you have to heat it repeatedly.
	8.	Now tightly weave a piece of wire through the holes and twist the ends together. This will secure the loops well and prevent them from coming apart. Usually the tape itself is not strong enough to do this. Do this to both strips. You can remove the tape at this point if you like.
	9.	Use a Stanley knife to cut through the loop at the marked positions. Carefully cut away every alternating loop. Also be careful not to slice too far when cutting in between the loops.
	10.	When you cut out the loops make sure they alternate on each of the strips. This allows them to mesh together. Make sure they can come apart freely.
	11.	Attach the parachute to the lower stage. Where you attach it will depend on your design.
	12.	Tape one strip to the bottle where you would like to position the parachute. Use a strong piece of tape either side of the join. The tape will act as a hinge for the door to open. In the photos on the left you can see how the tape is attached to both sides of the strip.
	13.	Insert the paperclip into the loops between the two strips to keep them aligned. Now tuck the parachute under the strips to make sure it will fit snugly. You can pack the parachute flat to make it more streamlined. Now while holding the parachute down with the strips, tape on the other strip down with another piece of tape. Again add tape to both the inside and outside of the strip.
	14.	Fit the upper stage/sustainer to the booster and tie a piece of wire around the nozzle of the sustainer. A piece of solid core copper telephone wire works best.
	15.	Pack the parachute and insert it under the two strips, and bring the loops together. Now thread the wire from the sustainer through the loops. This will hold the parachute in place. The wire should poke out about an inch on the other side. Make sure the wire is nice and smooth and that there aren't any kinks in it so it slides out of the loops freely.
	16.	When the staging mechanism activates and the sustainer flies off, it will pull the wire out of the loops and the strips will spring open to release the parachute. The mechanism is now ready to fly.
	17.	Although the parachute above is fitted to the side of the rocket, there are other places where it can be mounted. On the left is an example of the mechanism used on a bigger booster. The parachute is recessed into the space between the bottles which reduces the drag on the parachute. Here is an example of the parachute fitted to the top of a booster. http://www.youtube.com/watch?v=xeXA2VY445M

Notes

1. We have used this design on close to 50 flights so far with successful deploys on all of them.
2. Because this mechanism deploys the parachute at the staging event and hence the rocket can be travelling fairly fast it can be a less than ideal time to deploy a parachute. However,  the staging event will usually slow down the lower stage considerably and by the time the parachute is fully inflated, the stage has also slowed down considerably. Lower stages also don't tend to fly very high, so you want to deploy the parachute fairly soon after staging anyway.
3. This method can be applied to multi-staged rockets with each successive stage pulling out the parachute on the stage below.