Beginner's
Guide to Rockets
Gas Density
Answers
- Prediction of
mass of gas molecules in this classroom. Answers
will vary.
- A.
Mass of gas molecules in the classroom.
Answers will vary.
B.
Materials List:
One meter stick per group.
Density of air = 1.229 kg/meters cubed. (Info in BGR Air Properties
Definitions slide.)
D. Procedure:
Answers will vary but students should
list their steps in an orderly fashion and have ready a place to record
their measurements. Their procedure should demonstrate their understanding
of density = mass/volume.
E. Teacher Check:
The instructor should check that students
have thought out their steps before they proceed.
- A.
Answers
will vary. If their variable is the gas density, it should decrease with
increasing altitude.
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Altitude
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Your Variable ______________kg/m3
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What is the
relationship between altitude and your variable, ________________?
Answers
will vary.
B.
How does this relationship relate to air density and to the functioning
of a rocket engine? Answers
will vary. Students should become aware that a rocket engine
carries its own propellants and the thrust depends on the nozzle design.
Unlike a jet engine, the thrust generated by a rocket engine actually increases
with altitude because the gas density decreases and there is less "back
pressure" on the nozzle. There are two terms to the rocket thrust equation,
one is the mass flow times the exit velocity, the other is a pressure
times area correction. Increasing altitude increases the pressure times
area term.
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C.
Reflection: Which atmospheric factors affect air density?
Altitude, temperature, and air
pressure.
D.
Start RocketThrust to test your prediction. [Record the results
of your test in the table provided below.] Answers
will vary but the trend should be increasing thrust with altitude.
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Altitude
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Engine
Performance
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Related Sites:
Teaching Standards
Activity
Worksheet
Rocket Index
Rocket Home
Exploration Systems Mission Directorate Home
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