Popular Articles

terraclips TerraClips 3D Terrain

Last year, World Werks Games launched a new product called “Terra Clips”. The line features three separate products, Sewers of Malifaux, Streets of Malifaux and Buildings of Malifaux. While the sets are...

mid-power-rockets Mid Power Rockets Part One

When Estes announced their entry into mid power last year I was ecstatic. Partnering with Aerotech Consumer Aerospace, Estes launched their Pro Series II line this spring. The Pro Series motors are...

eurofighter-typhoon Revell Eurofighter Typhoon

The Eurofighter Typhoon is a very unique project as companies from three different countries took part in designing it. The twin engine, multirole Typhoon is in service in 6 different countries including...

ecx boost rc buggy ECX Boost Review

I bought the ECX Boost expecting a fun, not too serious little buggy. Since I am a seasoned RC hobbyist and this is a vehicle primarily aimed at newcomers to the hobby, this review was done...

skyhawk model kit Hasegawa Skyhawk Model Kit Review

The 1:32nd scale Hasegawa "Collectors Hi Grade" series OA-4M was released in 1987. Normally, I would not review a model kit that has been out close to 25 years but there is so little information out there...

rocket motors Black Powder Rocket Motors

How on earth do we get our rocket up in the air? What do all those codes mean on the rocket motor? When should I use a bigger rocket motor? With this article, I will answer all these questions...

advanced guide to miniature figures Advanced Miniature Construction Techniques

In this tutorial, we will be learning an advanced building technique called "pinning". We will also learn how to make seams disappear using Green Stuff. In order to build our dragon friend, we will need...

model rocket maintenance Model Rocket Maintenance

You've built a rocket and flown it several times and you are starting to notice some wear and tear on both your rocket and launch equipment. How do you keep your rocket gear looking good while performing at a high level and staying safe?

gundam model kit Gundam Model Basics

Welcome to the fun world of Gunpla. Gunpla is short for "Gundam Plastic Models" (In Japan, it's just a fad if it doesn't have some weird word to describe it's fanbase). Gundam models are perfect kits...

Recovering Your Model Rocket After Launch

Article by Paul Nortness

You've just spent the weekend building your new model rocket and it's time to fly. The last thing you want to do is have all that time and hard work come crashing into the ground. So, let's talk about rocket recovery.

I will also talk about several ways to keep your recovery devices safe from the hot gases that are expelled from the motor's ejection charge.

Featherweight Recovery

There are several forms of rocket recovery. The most basic is called "featherweight". With this method, the motor is expelled from the rocket and the rocket falls safely down to earth unscathed thanks to its extreme light weight. The downside to this method is the models are often very small and tend to come down ballistic rather than tumbling. When this happens, the rocket tends to embed itself into the ground making it very hard to find. This little 220 Swift is a typical featherweight rocket.

featherweight rocket

Streamer Recovery

Another form is the streamer. You will typically find streamers on rockets with bodies too narrow to fit a parachute though in some cases streamers will be used to bring a high altitude rocket down with minimal drift. Streamers are usually attached directly to the shock cord. When the ejection charge blows the nose cone, the streamer will unravel and slow the rocket with drag.

streamer

Parachute Recovery

The most widely used form of recovering model rockets is the parachute. Parachutes come in all sizes and materials. In low powered rocketry, parachutes tend to be made from plastic sheet. In fact, rocket makers like Dr. Zooch actually use plastic trash bags for parachutes. In the bigger higher powered rockets, you will find rip stop nylon parachutes. Whatever the material, the principle remains the same. The main part of the parachute is called the canopy. The canopy has shroud lines that connect it to the rocket. The nose cone blows off, pulling the parachute with it.

parachute

The parachute then unfurls as it fills with air and slows the descent. The trouble with parachutes is they are susceptible to cross winds which can cause the rocket to drift. This of course adds the problem of rockets getting eaten by the dreaded tree monster and the even worse Evil Doctor Power Lines. That last one is a real drag because you can still see your rocket waving at you but you can't get it. Drifting can be lessened by adding a slip hole in the parachute canopy. To add a slip hole, simply cut out a circle in the center of the canopy.

Other Forms Of Recovery

Other methods include glide, where the model ejects the motor casing at apogee and glides down. Blown nose is yet another form of recovery. Much like featherweight, blown nose recovery tends to be used on small rockets. The nose cone is attached to the rocket via an elastic shock cord, when the nose is blown off at ejection it breaks the rocket's aerodynamic profile and causes it to tumble to Earth.

Keeping It Safe

Ok, so we've talked about some of the basic forms of model rocket recovery. Now how do we keep it all safe from those hot gases? One of the worst feelings in the world is the kick in the gut you feel after the recovery device of your special rocket fails. A failure is often caused by the ejection gases coming in direct contact with the recovery device and melting it. To prevent this, you pack the body tube with recovery wadding.

recovery wadding

Wadding looks a little like toilet paper, but it has been treated with chemicals that make it fireproof. Just crumple up a few sheets of wadding and pack it into the body prior to putting it in the chute. Estes is very good about telling you how many sheets you should use based on the size of the rocket. After a while, you will just be able to gauge how much to use based on previous experience. Recovery wadding works great, but it can get a bit expensive. The other problem is it tends to get blown all over the place. Being a good person, you always want to try to gather up as much of it as you can after your launches. Remember, other people use these fields and parks too! A great alternative to wadding is "dog barf", so named because... well, I'm not really sure why. Dog Barf is a fancy name for Cellulose Fiber Insulation. This product is used to insulate houses and is "blown in" to the house with a large hose.

insulation

It is made entirely from recycled newspaper that has been chemically treated to be fire proof. I purchased a large bale for $11.00 and don't think I will live long enough to see half of it gone. Just pack it into the body as you would standard recovery wadding, and off you go. The best thing about dog barf is it breaks apart into fine pieces as it ejects and doesn't make the mess that wadding does, and anything that does make it to the ground is biodegradable so it will break down into the soil naturally.

Baffles

For bigger diameter rockets, it isn't feasible to use wadding sometimes. That is when the use of a baffle makes sense. A baffle is a device that is put into the rocket during construction. I find a good place for a baffle is just forward of a coupler, some people even build a baffle around the coupler. Baffles have two bulkheads and a "trap" of some kind that will trap the hot gases and debris from the ejection charge, cool them and expel them out the top to blow the nose cone. Here is an example of a baffle from Semroc. This particular baffle fits a BT-80 body tube.

baffle

The hot gases enter the baffle through the hole in the bottom bulkhead. Debris is deflected off the bulkhead and stays away from the recovery device. As the hot gas enters the hole, it goes up the tube and is trapped between the two bulkheads. The gas is cooled as it travels up the second tube and out through the hole in the top bulkhead. This results in the nose cone being blown and parachute deployed safely. Even though it is safe to use a baffle on its own, I still prefer lining the top of the bulkhead with wadding or dog barf for just a little extra protection.

Have fun and happy flying!

blog comments powered by Disqus