Design Specification of
Nose cone or Coiffe
What tasks do we expect a coiffe/capsule module to perform.
Capable of coping with 60>400g launch acceleration loadings without deforming plastically.
The use of a stable ‘shock plate’ base is recommended for the foundation of the coiffe module
In all weather conditions: rain, snow / ice sub zero temperatures and sunshine/heat.
In the overall objective of keeping rocket mass to a minimum the specification of parachute diameter and cord support system should be kept to a minimum.
The decision to use multiple parachutes for coiffe and launcher will set the size or volume of coiffe required.
The memory and packing volume of the parachute material needs to be quantified.
This can be done simply by taking the parachute and folding it as you would before placing it in the capsule /coiffe and recording the time it takes to expand.
Determine the packing volume before and after folding by placing the folded parachute into the base of a plastic bottle with the neck part removed.
Then leave it for the time you would normally take to pressurise and launch the rocket after installing the parachute and add the expected flight time say 2minutes plus 5seconds Checking the change in packing volume with time.
A direct comparison can be undertaken by folding two similar parachutes made of different materials and compressing them one in each hand. Then release them simultaneously and compare which extends first.
Some materials have good memory and straighten out almost immediately after being folded.
Whilst others will remain folded without too much spring back after they are placed into the coiffe.
Test fold and install the parachute into the nose cone/coiffe and see if it expands beyond the opening of the coiffe once released. Cut off the bottom of the bottle to the height you think will be adequate for a coiffe volume and place the cord system and folded parachute in position. Test until you are satisfied that the coiffe volume is correct and enables the d’coiffe angle required.
This will determine the volume of coiffe required.
Another more precise measurement is to make a simple d’coiffe angle meter .
This is simply made by sticking the cioffe module base to a ruler or suitably rigid strip of material and measuring the rotation angle/ height to which one end is raised before the coiffe and parachute releases from the base.
Different methods of parachute folding can be tried and compared.
Similarly the position of the balance weight within the nose/coiffe can be varied to see how it affects the release angle.
Always make sure that the parachute is clean and dry. Before lightly sprinkling with talcum powder prior to folding and installing into the rocket nose cone.
Relative mass. mass of coiffe mc relative to launcher mL. Relative momentum during flight.
Animation of Soyuz MetOp satellite launch and de-coiffe release.
Video of timer release system Variable timer set at 2 seconds,
Pressure release system with location collar bonded to shock plate with pressure compensation holes linking the interior of the nose cone to ducts formed by deformations in bottle base.
This site was created on the 15th April 2003
©John Gwynn and sons2003
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as long as you give us proper credit (by referring to "The Water-Rocket Explorer" http://waterocket.explorer.free.fr).