Color Coding
Estes model rocket engine packages have
color-coded labels that indicate the engine's applications.
Green Label are single stage engines to
be used with single stage models. They have a time delay with an
ejection charge. Purple Label are upper
stage engines to be used in the upper stage of multi-stage
models. They may also be used in very light single stage models.
They have a time delay and an ejection charge
Red Label are booster stage
engines to be used in the lower stages of multi-stage rockets and
special projects only. They have no delay or ejection charge. Black
Label are special plugged engines for R/C Gliders.
They contain no delay or ejection charge.
Engine Codes
Model Rocket Engines each have a special
designation to describe various parameters of the engine
construction and operation. There are three parts to this
designation. The first part is a letter and indicates the total
impulse range of the engine. The second part is a number and
indicates the average thrust of the engine. The third part is
separated from the second by a hyphen, is numeric, and indicates
the time delay in seconds between the thrust phase and ejection.
We shall use the Estes B6-4 as an example:
B - Total
Impulse
This letter indicates the Total Impulse range of
the engine. Total impulse is the total power the engine produces,
which basically indicates how much propellant it contains. Total
impulse is measured in Newton-seconds. One Newton-second is the
amount of total impulse produced by one Newton of thrust for a
duration of one second. A five Newton-second engine
("B" type) could produce five Newtons of thrust for one
second, ten Newtons for 1/2 second, or any combination that
equals five Newton-seconds when multiplied. The following chart
indicates the total impulse range for the various size engines.
All Estes "½A" through "D" size engines are
produced at the maximum level in each category.
| Type | Total Impulse |
|---|---|
| 1/2 A | 0.63 - 1.25 |
| A | 1.26 - 2.50 |
| B | 2.51 - 5.00 |
| C | 5.01 - 10.00 |
| D | 10.01 - 20.00 |
6 - Average
Thrust
This number tells you the average thrust the motor
delivers during the thrust phase and is measured in Newtons. The
actual thrust varies, and is shown on the time-thrust curve (see
example below). For a particular engine size, let's say
"B", the propellant may be burned quickly, giving high
thrust for a short time, or slowly, giving lower thrust for a
longer time. A higher average thrust engine (B8) is best for
heavier models, while a lower average thrust, longer burn engine
(B4) is more efficient in smaller, lighter models.
4 - Time Delay
The time delay is the number of seconds between
the end of the thrust phase (propellant burning) and activation
of the ejection charge. The time delay allows the model to coast
to its peak altitude before the recovery system is deployed.
B6-4 Time Thrust Profile
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