If your rocket attains any great altitude and does not have a recovery system of some sort, it will probably do itself serious damage on impact. To avert this sort of disaster, you can employ some sort of parachute (circular, parafoil, X-form) or other device that will slow down the decent of the rocket from an appropriate point in the flight. The computer model assumes a parachute is used although there is no reason why you should not use a helicopter type recovery or some other device.

If you checked the Parachute in use checkbox in the Rocket section, you will be able to edit the following values (Parameters marked * do not appear in the Novice version) . . .

Diameter opened out flat (m) For the sake of simplicity and ease, the computer uses the diameter of the parachute opened out flat. This can be measured on the floor or ground and is a great deal easier than trying to estimate the diameter of the parachute when opened out fully in a decent.

* Parachute Coeff of Drag Typical values are given for circular and x-form parachutes. The coefficient of drag for the parachute works the same as the coefficient of drag for the rocket - the drag increases proportionally to the square of the speed and the square of the diameter. In the Novice version, the coefficient of drag is the value for a circular parachute unless a file is loaded that had a different value saved

	* Deploy The model allows for two methods of parachute deployment: Apogee and Timed.
		(*) Apogee. With Apogee, the parachute is deployed at the top of the flight in the way that a Nose Separates at Apogee (NSA) nose cone would work. Selecting this option makes the model behave in that way.
		(*) Timer (s) With a Timer, the parachute is deployed after a particular length of time after launch, regardless of whereabouts in the flight it is. When you select this option, you are allowed to specify the time after the launch at which the chute is deployed.

Delay in opening (m) The delay in opening is the distance that the chute takes to open fully after the chosen deployment method has released it. If you selected Apogee, 5 metres for the delay in opening and was launching near to vertical, the parachute would be fully deployed at approximately 5 metres below the apogee. If you selected timed and 4 seconds with 5 metres again, the chute would start its deployment after 4 seconds and once it had travelled a further 5 metres from that point it would be fully deployed. Note that if it was travelling a curved path, it would be the distance along the path and not the distance in a straight line from the point of initial release.

 

Copyright ©2000 Paul Grosse. All Rights Reserved.