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Glossary of Rocket Terminology
Ammonium Perchlorate
Ammonium Perchlorate is used as an
oxidizer in
many composite rocket fuels. It is also the oxidizer which is used in
the Space Shuttle's solid rocket boosters (SRB's). 68% of the of the space shuttle's SRB
propellant is ammonium perchlorate, 17% of it is aluminum powder,
and the rest is a combustible compound which holds the whole
mixture together and gives it a sort of "rubbery"
texture so that the propellant grains can be molded into the
required shapes.
CAR (Canadian Association of
Rocketry)
CAR is the Canadian Association of
Rocketry and it's essentially the Canadian version of the NAR and Tripoli Rocketry Association all
rolled into one.
Center of Gravity (CG)
The center of gravity is the
balance point of an object. For example, if you throw a stick, it
will rotate around this point.
Center of Pressure (CP)
The center of pressure is the
point in an object at which all forces acting upon it are
centered. In the case of a model rocket, forces acting upon it
include gravity, the thrust of the motor, and aerodynamic drag.
Centuri
Centuri was Estes' main competitor in the model rocket
business until Estes bought them out in the early eighties. They
made a number of very interesting designs, the plans for many of
which can be found at JimZ's web
site.
Composite rocket motor
A composite rocket motor is any
rocket motor which doesn't use black powder as it's propellant.
Often, they require hotter igniters to light and potent oxidizers to
burn the fuel, but they offer higher performance than the
standard black powder rocket motors. Since they offer about twice
the performance of black powder motors, composite propellant for
an "E" motor would fit inside a 24 x 70 mm casing
normally designed for a black powder "D" motor.
Estes
Estes is one of the first
companies that started it all way back in 1959 when they
introduced the Scout, a tumble recovery rocket which was this
company's (and the world's) first model rocket. A large number of
plans for older Estes rockets can be found at JimZ's web
site. Estes is currently the largest manufacturer of model
rockets in the world at this time.
Igniter
An igniter is a small device which
is used to ignite the propellant of a rocket motor. It's usually
made of nichrome wire tipped with a combustible solid compound.
When an electrical current is fed through the igniter, the
nichrome wire heats up, ignites the combustible material which in
turn ignites the propellant.
NAR (National Association of
Rocketry)
NAR is the National Association of
Rocketry which is the organization which regulates the industry
by setting standards for safety in the field as well as rules for
competitions. They test and safety certify rocket motors which
meet their stringent safety requirements. CAR is the Canadian Association of Rocketry
and is essentially the Canadian version of the NAR except that
the CAR also provides certification for high power rocketry which
in the U.S. is handled by the Tripoli Rocketry Association.
Newton
The Newton (named after Sir Isaac
Newton) is a measure of force and is used to indicate the thrust
of a rocket motor. One pound of thrust equals 4.45 Newtons.
Newton-Second (N-s)
The Newton-second is a measure of
total impulse and is the product of applied force multiplied by
time.
Oxidizer
All things need oxygen to burn.
When a pile of wood burns in an open fire, it sucks in oxygen
from the surrounding air. When rocket fuel burns, it can't suck
in oxygen from the surrounding air because the fuel is in a
closed environment. For this reason, rocket fuels need oxygen to
burn in and they get it from an oxidizer which may be in the form
of liquid oxygen for liquid propellants in the big NASA rockets
or ammonium perchlorate for solid propellants. Also, many rocket
fuels require more oxygen to be present in a smaller space per
amount of fuel for it to burn properly or even at all.
SRB (Solid Rocket Booster)
Solid Rocket Boosters are boosters
which are strapped onto the side of a rocket to assist in liftoff
which then fall away from the rocket once the solid propellant
has burned out. Examples of NASA rockets which use these types of
boosters are the Space Shuttle, Titan III, and Delta II. In model
rocketry, these are used for a staging technique called parallel
staging.
Specific Impulse
Specific impulse refers to the power per unit of propellant. For instance,
when Aerotech says that their propellant delivers nearly three times the power
of the equivalent amount of black powder propellant, they're referring to the
specific impulse.
Total Impulse
The total impulse of a rocket
motor is the measure of its power which is measured in Newton
seconds. In model &
high power rocketry, the total impulse of a motor is indicated by
a letter. The table below lists the power ranges for each class
of motor.
| Model Rocket Motor Power Ranges | High Power Rocket Motor Power Ranges |
||
| Class | Total Impulse in Newtons | Class | Total Impulse in Newtons |
| 1/4A | 0.312 - 0.625 | H | 160.01 - 320.00 |
| 1/2A | 0.626 - 1.25 | I | 320.01 - 640.00 |
| A | 1.26 - 2.50 | J | 640.01 - 1280.00 |
| B | 2.51 - 5.00 | K | 1280.01 - 2560.00 |
| C | 5.01 - 10.00 | L | 2560.01 - 5120.00 |
| D | 10.01 - 20.00 | M | 5120.01 - 10240.00 |
| E | 20.01 - 40.00 | N | 10240.01 - 20480.00 |
| F | 40.01 - 80.00 | O | 20480.01 - 40960.00 |
| G | 80.01 - 160.00 | ||
