Using the inclined plane (tilt angle) test regularly to quantify launch acceptability of the nose cone module helps eliminate a lot of those parameters that could contribute to poor reliability.
Test the capsule and find the release angle, then rotate 90degrees and retest etc. Until you return to starting point. This will highlight any asymmetry within the assembly .Record the date and the results in a capsule launch readiness table.
For assemblies that do not conform then they can either be repaired and re-tested or scrapped. Be ruthless , a valuable payload could be at risk.
Number each base plate and nose cone. We tie the nose to the base assembly using an external link made from fine nylon fishing line. To keep the tested assembly together.
Note: This tie could also replace the need for a secondary parachute for the capsule recovery.
or alternatively use two strips of 'sellotape' placed across joint .
We have explained both how to manufacture and measure the capability of our small cone module that is good for a parachute up to and including 70cm in diameter. Although we have successfully deployed larger parachutes of 90cms. Reliability is very dependent on precise folding of the parachute.
To be quite honest the size of a recovery parachute should be just big enough to recover the rocket or its payload safely.
If , like me you prefer design optimisation of rocket performance. Then you should try to minimise everything including parachutes.
Tilt test procedure:
Take a ruler or a suitably straight piece of plywood and attach the parachute module base to it close to one end.
Coil parachute cords and fold parachute before installing the nose cone.
Then rotate the end of the ruler/plywood strip pivoting the free end about the fulcrum.
Slowly increase the angle and record the angle or height of the free end above the start datum at which nose cone seperation occurs.
To carry larger parachutes if required or special mission payloads.
The main consideration when launching any special payloads is that the payload mass m3 must be kept to a minimum.
Any large increase in M2 will radically affect the rocket performance. (Refer to performance parameters and Tsiolkovski's table.)
So for instance if we would like to record flight data that is representative of normal flight dynamics then m3 has to be small..
Some ideas for special payloads:
These all have to be installed in a modified nose cone module.
Electronic Flight data recorder.
A small electronic flight data recorder can be easily installed within the base adapter of the small nose cone module. These can weigh as little as 20gms and operate from small batteries. We have developed our own that operates from a 3v watch battery.
These can record pressure variation with time during the rocket flight with a sample frequency of 10 sample readings a second.
Full installation mass of data logger with battery holder and electrical harness 21gms.
Prototype nose module Sept 2002.
We have developed an aerodynamic pressure release system that initially sucks the capsule onto the shock plate at launch and later releases the nose cone when the rocket slows as it reaches apogee and the pressure drop between the exterior and the interior of the capsule tends to zero.
Note: Normally we launch near vertical within a cone of 15 degrees.
At launch, the pressure compensation helps retain the nose module in place and helps avoid severe deformation under pressure.
During our initial launches we failed to prevent large volume nose cones( parachute modules) from seperating immediately after launch. Within the first 20m after launch.
Even with a drilled nose cone we encountered the same difficulties. This is how we came to developed our nose module and shock plate.
It really depends on the initial launch acceleration loading's to which the rocket is subjected.
Note: We now know that the rocket experiences over 4000m/s2 during the initial acceleration phase. Thanks to research carried out at Leeds University2004
Use the guide to nose cone development
This site was created on the 15th April 2003
ŠJohn Gwynn and sons2003
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