The Challenges of a Successful Rocket Flight
The most challenging aspect of flying hobby rockets is the successful recovery of the rocket. The problem is not that the rocket will not come down, it will come down, and come down successfully. The challenge is to have everything in place to recover the rocket without a scratch so you can enjoy that beer at the end of the day and tell flight stories of fancy. Now is the time to choose a recovery method to safely return your rocket from the wispy white clouds. There are basically four acceptable recovery methods to do this. The fifth method, ballistic recovery, is not acceptable, even though it might seem popular at launches sometimes. The acceptable recovery methods are tumble, glide, streamer, and parachute which all can utilize single or duel deployment. Most rocket kits come with some type of recovery method. However, the imagination is the limit when designing and building your own rocket.
Tumble recovery is used for very strong and/or very light rockets. In tumble recovery, the engine is ejected at apogee thus making the rocket unstable and it tumbles as it descends. Tumble recovery has the advantage of landing close to the launch pad. Tumble recovery is very rarely used in High Power Rockets. It is more common in Estes rockets such as the old Scout and Mosquito and in various stages of smaller multistage rockets.
Glide recovery is a lot of fun. Depending on the rocket, the engine is usually ejected at burnout and the rocket simply glides back to earth. The old Estes Sky Dart was a delta wing rocket with glide recovery that would seemly glide forever, sometimes into oblivion. Also, ScissorsWing Transport has made a recent come back. SissorsWing Transport ascends as a rocket and at apogee, the wings unfold and the rocket starts its long glide back to earth. Again, glide recovery is not frequently utilized in high power rockets but can be extremely satisfying in smaller rockets.
Streamers are more popular and as the name suggests, utilizes streamers as the recovery method. The streamers are ejected at apogee and create drag during the descent that slows the rocket to a safe landing. Streamers can be made of paper, plastic or Mylar. Mylar is strong and preferred for high altitude flights as it will reflect the sun, making the rocket’s descent easier to track. Also, streamers are less affected by the wind, leading to closer landings and less walking. Unlike the previous two recovery methods, streamers are sometimes used for apogee recovery in duel stage recovery to provide some control during the descent or to make the rocket easier to spot.
Deployment charge failed leading to tumble recovery. Not Good!
The most popular recovery method is parachutes. There is nothing more majestic then watching a rocket slowly descend on a colorful parachute. There are many types of parachutes to choose from. The purpose of the parachute is to slow the rocket enough to land without damage. The size depends on the rocket but usually a parachute that allows the rocket to descend at about 25 feet a second is good. Rockets with large fins protruding past the body tube will require larger parachutes to prevent fin damage upon landing. Rockets recovered by parachute are easily influence by the winds. For this reason, most high power rocketeers utilized different deployment strategies.
Utilizing a single deployment method is called single deployment. Single deployment usually deploys the recovery mechanism at apogee and usually out of the main body tube. Duel deployment utilizes two recovery mechanisms usually at different times during the rocket’s recovery. Duel deployment requires electronics of some sort, usually an altimeter or a timer. The electronics will have an apogee deployment where a small drogue parachute or streamer is deployed at apogee. Many rocketeers will deploy nothing at apogee. The apogee event is used to simply separate the rocket. If the rocket halves are of equal drag, they will tumble down connected via the shock cord. A small drogue parachute can be used to help prevent the two rocket halves from bumping into each other and scratching the finish.
The second part of duel recovery is to deploy the main recovery mechanism, preferably at a lower altitude. This allows the rocket to be recovered closer to the pads and reduces the affects of the wind. Usually altimeters have a range of altitude settings. Common main deployment altitudes are 400-1000 feet. Too low and the parachute might not have time to deploy and too high, the rocket might float away.
Now that the recovery system is designed and implemented, we can move on to Simulating Your Rocket
Excessive deployment charge caused separation. Not good!
January 6, 2009 4:31 PM
By Peter E. Abresch Jr.
Choosing your Recovery Method