CHIRON4 booster for two-stage rocket.

The CHIRON4 booster is ready for testing on the 22nd of September. This 6 grain 21000Ns booster is inspired on previous 8 grain CHIRON motors with several enhanced safety features:

1. The core was increased to 45mm to reduce mass flux erosive burning.
2. The multi nozzle design allows for smaller graphite inserts, reducing the risk of nozzle cracking. In addition, multiple nozzles may reduce the risk of nozzle blockage.
3. The diameter of the grain was slightly decreased to allow for a full layer of insulating EPDM, reducing the thermal stress on the casing.
4. Radial bolts were replaced by a circlip ring to improve strength.

New inside liner for propellant casting tubes

To allow for effective bonding of the sugar propellant to the aluminium casting tubes, tubes were sanded with grain 60 and degreased. Subsequently, a 0.5mm layer of plain cotton cloth was glued on the inside of the retainer.

The cotton cloth is an improvement over the previously used kraftpaper, as the kraftpaper could be easily split into two separate layers. Furthermore, airpockets can be easily removed underneath the cotton layer.