Sonic Rocket Locators

By Phil Stein - L3, NAR# 78514, TRA# 9311

This is intended to provide information on the use of devices that provide an audible means of locating a rocket in a field or wooded areas where the rocket cannot easily be located visually.

First off I must mention that a sonic locator will get you close to your rocket but, you still need to see it.  Use a bright colored parachute.  Also the color of the rocket can make it much easier to see or, for it to hide from you.  Don't expect that camouflage paint job to be easy to spot.  Some people have mentioned that metallic streamers can make it easier to spot a rocket I haven't tried this but it makes sense..

There are devices made specifically for audibly locating rockets made by Pratt Hobbies and Adapt Rocketry.  I'll leave it to the manufacturers to describe their products.  I do own a Pratt Microbeacon.  I have not had the chance to use it.  I had it for two years before I tried to use it.  When I did, it didn't work.  I saw Doug Pratt at a launch and gave it to him to check out.  I received a new one shortly there after in the mail.  That's what I call excellent service!  Since up until this point, I've only used products sold as personal alarms, that's what I'll be discussing.

Any of these devices will output significantly less sound if you cover the speaker with duct tape or anything else.  Keep this in mind when you are attaching them to your rocket.  If your device has a power switch, tape it to the on position so that it doesn't accidentally get turned off during deployment.  Also, if the speaker is pointing towards the ground after landing, the noise level will be reduced.  I like make sure that I have a way to turn off the noise when I go to recover the rocket.  That way if whatever turns off the noise gets lost during the flight, I can still silence it.  These things are very loud and irritating and you will want to turn it off ASAP after you find it. 

The device in the upper left is sold at home centers as a Window Alarm.  The device in the middle is a Pratt Microbeacon.  The rest are Personal Alarms that are activated by pulling the cord out of the unit.

The photo above shows what is inside of each of the products (except the Microbeacon.)  In  the picture, are two devices that are comprised of the only parts necessary from their corresponding original device to perform the task.  They have been placed in close proximity to the device that they originated from.  As you can see, it is possible to repackage the guts of these products to come up with a much smaller device.

This shows how to use a personal alarm.  The photo above shows a personal alarm before the cord is pulled out.  The picture below is after the cord was pulled out.  Pulling the cord out of the alarm starts the noise.  Notice that the speaker is not covered with duct tape.  The cord gets pulled out of the alarm when the shock cord gets stretched out by parachute deployment.  Be sure to attach the alarm securely to the shock cord.  I have seen the alarm come loose because the tape tore.  It is best to have the receptacle for the pull cord as close to the shock cord as possible.  That is so that it is as close to being pulled straight out as possible.  The top photo does not illustrate this.

This shows how to use a window alarm.  The window alarm is controlled by the magnet in the smaller of the two pieces.  If the magnet is far enough away from the other piece, a magnetic switch inside trips the alarm.  The photo above shows a window alarm in the quiet position.  The picture below is after the magnet was moved away from the switch which sets off the alarm.  Notice that the speaker is not covered with duct tape.  The cord  pulls the magnet away from the alarm when the shock cord gets stretched out by parachute deployment.  Be sure to attach the alarm securely to the shock cord.  I have seen alarms come loose because the tape tore.  When this occurred, it was easier to find the alarm than the rocket.

Happy hunting!

Phil Stein