TECH TIPS AND OTHER ASSORTED ROCKETRY TRICKS

Tech Tip #1 - Prevent Rocket Crashes by Recovery System Upgrades

All rocket kits are designed with a price point in mind. For most manufacturers that means elastic cord harness, cotton string and bin-liner parachute material. You can be almost certain to get one perfect flight out of the standard recovery setup. With care and luck you can get two, three or more. With a lot of care and luck!

Excuse the pun but the down side of a recovery problem often means the loss of the rocket. Gravity is a cruel mistress.

We just hate to see kids cry (or grown ups either!) but that's exactly what happens when the rocket that they slaved hours over assembling and painting falls out of the sky because:

• The knicker elastic shock cord fried resulting in a lost nose cone and a core sample of the local field.
• The plastic parachute melted because the paper wadding wasn't sufficient. They are inelegant to watch and smell bad.
• Weak chute and line materials couldn't handle the shock of an early or late deployment. If you want to fly a streamer, fit one!

We want all Rocket Shop customers to be happy customers so we have created four Recovery Upgrade Kits to minimise the chances of a crashed rocket due to recovery trauma. We can't help much with lawn darts (where the nose cone didn't come off because it was too tight or the motor ejected), but a Recovery Upgrade can reduce the chances of the other three common recovery mishaps: core sample, recovery by smoking wad and bungie bruising.

A core sample happens when the nose cone and chute sail off over the horizon and the body returns open end first into the flying field. Recovery by smoking wad is where the extremely flamable plastic chute was torched by a vigorous ejection charge unimpeded by sufficient wadding. A bungie bruise results from an elastic shock cord recoiling and smacking the nose cone into the body tube, damaging the finish, the BT, the nose cone or all three.

The reduce the chance of an unhappy ending we propose that you upgrade your recovery system.

• For rockets 18mm in diameter or below use Kit A. A includes a quality 10 or 12 inch nylon chute with strong nylon lines, a fireproof Nomex ejection shield, a swivel link and a length of 100 pound test Kevlar cord. You can substitute a competition Mylar streamer if your BT is very tight.
• For rockets 18 to 24mm in diameter use Kit B. B includes a quality 14 or 15 inch nylon chute with strong nylon lines, a fireproof Nomex ejection shield, a swivel link and a length of 100 pound test Kevlar cord.
• For rockets 24 to 42mm in diameter, Kit C's for you. C includes a quality 16 or 18 inch nylon chute with strong nylon lines, a fireproof Nomex ejection shield, a swivel link and a length of 100 pound test Kevlar cord.
• Kit D is for BIG rockets. D includes one or two chutes with strong nylon lines to suit the model, a large fireproof Nomex ejection shield, a swivel link and a length of 100 pound test Kevlar cord.

These kits are quick to fit and will go a long way towards preventing the most frequent causes of recovery mishaps. Basically, you use the Estes technique of a plaster that traps the end of the shock cord and provides a large bonding surface. Only for the upgrades we advise using epoxy glue for strength. A complete pictorial for the process will be inserted here soon. Promise!

Here are some more tips for a successful flight and recovery every time:

• Make sure that the motor is secure and doesn't eject instead of the parachute. If you are flying 24mm motors or above, check out Rowes Retainers.
• Check that the nose cone isn't jammed on too tight or isn't loose as a goose either.
• Fold the chute properly and put it in the rocket, then the lines then the nose cone. If you have to jam it in, it won't come out!
• To make sure the chute can slide out easily when it gets the nudge, use a liberal shake of talcum powder.
• Put a dab of glue (CA or epoxy or white glue) on your knots to keep them knotted.
• Inspect your chute harness attachment points after every flight.
• Use masking tape "frangible" links to absorb deployment shock. This is vital for the Recovery Upgrade Kits as the Kevlar doesn't stretch to absorb the initial chute deployment stress!

Whenever you modify your rockets, check that they are still safe and stable with SpaceCAD.

© Hesperis Technology, 2004

Tech Tip #3 - Build or Buy - Deployment Pistons