Hydroflite Altitude Measurement

Click here for the Hydroflite altitude records.

Rocket Altitude Determination Using the Apogee Method

These instructions outline how to determine the maximum altitude that your rocket flies. It takes two people; a sighter and a reader. To determine the maximum altitude, follow these three simple steps.

First, make a HYDROFLITE Angle Determination Device as shown in Figure 1. You can use a yardstick or 3 foot length of 1.5" PVC pipe or anything long and straight to make the sighting piece. Mount the protractor page to a piece of cardboard. Fasten the cardboard to the sighting piece. (Note: make sure the top horizontal line is parallel to the sighting piece. Poke a hole through the cardboard where it says “String Through Here”. Tie a weight to one end of the string and put the other end of the string through the cardboard and fasten. (Note: when the string is fastened, you should have about 13" of string between the hole in the cardboard and the top of the weight.)

Figure 1. Angle Determination Device

Second, launch a water rocket. A sighter and a reader are positioned a known distance from the launch point. The sighter points the sighing device to the rocket and holds the Angle Determination Device at the position of maximum altitude (or apogee) of the rocket trajectory. (Note: this will take some practice!!) The reader reads the angle off of the Angle Determination Device where the string crosses the angle indicators. (Note: make sure the weight is not swinging. The sighter must hold the Angle Determination Device very still while the reader takes the reading.)

Third, determine the maximum altitude using this simple formula:

Max Altitude = Known Distance times tan(Observed Angle)

Figure 2 shows the triangle formed between the Apogee of Rocket Flight, Launch Point, and Observer Position. Since tan(θ) = sin(θ)/cos(θ), tan(Observed Angle) =Max Altitude / Known Distance. This formula assumes that the launch point and observer position are the same elevation.

Figure 2. Relationship Triangle

Here is a PDF file of the Angle Determination Device.
Open it in Adobe Acrobat and print it out.

About Hydroflite	Hydroflite Altitude Measurement Click here for the Hydroflite altitude records. Rocket Altitude Determination Using the Apogee Method These instructions outline how to determine the maximum altitude that your rocket flies. It takes two people; a sighter and a reader. To determine the maximum altitude, follow these three simple steps. First, make a HYDROFLITE Angle Determination Device as shown in Figure 1. You can use a yardstick or 3 foot length of 1.5" PVC pipe or anything long and straight to make the sighting piece. Mount the protractor page to a piece of cardboard. Fasten the cardboard to the sighting piece. (Note: make sure the top horizontal line is parallel to the sighting piece. Poke a hole through the cardboard where it says “String Through Here”. Tie a weight to one end of the string and put the other end of the string through the cardboard and fasten. (Note: when the string is fastened, you should have about 13" of string between the hole in the cardboard and the top of the weight.) Figure 1. Angle Determination Device Second, launch a water rocket. A sighter and a reader are positioned a known distance from the launch point. The sighter points the sighing device to the rocket and holds the Angle Determination Device at the position of maximum altitude (or apogee) of the rocket trajectory. (Note: this will take some practice!!) The reader reads the angle off of the Angle Determination Device where the string crosses the angle indicators. (Note: make sure the weight is not swinging. The sighter must hold the Angle Determination Device very still while the reader takes the reading.) Third, determine the maximum altitude using this simple formula: Max Altitude = Known Distance times tan(Observed Angle) Figure 2 shows the triangle formed between the Apogee of Rocket Flight, Launch Point, and Observer Position. Since tan(θ) = sin(θ)/cos(θ), tan(Observed Angle) =Max Altitude / Known Distance. This formula assumes that the launch point and observer position are the same elevation. Figure 2. Relationship Triangle Here is a PDF file of the Angle Determination Device. Open it in Adobe Acrobat and print it out. Altitude Records We are collecting high altitude records from Hydroflite customers who have measured their launches. If you measure your maximum altitude, send us (altitude@hydroflite.net) your launch data and computed high altitude. If it is a record, you will be added to the list of record holders. The data to include in your email is: your name, city of launch, temperature at time of launch, size of bottle, approximate volume of water, distance between launcher and observer, measured angle, and computed altitude. Good luck.
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