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NERO Projects   Hx Rockets   Pyrotechnics

The pyrotechnical devices of the Hx series rockets

For the Hx rockets a number of pyrotechnical devices have been used. The design team deliberately chose for pyrotechnical devices since they are very reliable. The pyro systems which have been implemented are given in the following table:
Function Operation Re-usable
Ejection of parachute hatch Pyrotechnical bolt No
Release of main parachute (de-blocking device) Pin puller Yes
Stage 1/2 separation Pin pusher Yes

Pyrotechnical bolt

The pyrotechnical bolt is in principle a hollow bolt sealed with a screwable cover and filled with an pyrotechnical charge. A V-shaped notch is machined in the centre of the bolt. Upon ignition of the pyrotechnical charge, the bolt will fracture at the location of the notch and both parts of the bolt will fly away with considerable velocity. This makes this type of bolt very well suited for applications such as the release of the parachute hatch. Our experience is that the hatch will be blown  several meters away from the rocket, thus enabling a clear path for the drogue parachute to eject and deploy.

De-blocking device

The drogue parachute is attached to the main parachute by means of a cord. This cord is initially (during the flight phase of the drogue parachute) restrained or blocked by the de-blocking device. As soon as the de-blocking device is operated, the cord is released and the drogue parachute will pull the main parachute out of the parachute compartment. Within the de-blocking device, a pin is attached to a piston which can be moved. The piston is assembled in the 'hold' position. An pyrotechnical charge of about 0.1 grams will produce the gas pressure required to move the piston into the 'release' position. The shock caused by the moving piston is absorbed by a crushable honeycomb disk.

Photograph of the pyro5technical bold from the H8. The cap of the parachute compartment will be attached on to this pyrotechnical bold with a bold. The gap for this bold can be easily seen.
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A design drawing of the de-blocking device (Dutch annotations only).

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A picture of the de-blocking device (shown on the left).
Blue=new Red=Visited H7 separation mechanism Find out how the separation mechanism of the H7 and H10 operates.