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**TECHNICAL QUESTIONS**:

**Which of Newton's Laws best describes the behavior of a rocket motor?**- Newton's First Law: Every body continues in its state of rest or of uniform motion in a straight line unless it is compelled to change that state by forces impressed upon it.
- Newton's Second Law: The rate of change of momentum is proportional to the force impressed and is in the same direction as that force.
- Newton's Third Law: To every action there is always an equal and opposite reaction.

**How does Newton's Third Law "To every action there is always an equal and opposite reaction" relate to rocketry?**- That the blast deflector must be strong enough to push the rocket off the launch pad at ignition.
- That a rocket flies because the rocket motor "pushes" the rocket in a direction opposite of the exhaust jet.
- That the thrust of a rocket motor is proportional to the air density at the launch site.

**What are the three forces acting upon a rocket during the course of its flight?**- Thrust, rocket diameter and finish.
- Nose cone shape, thrust and drag.
- Gravity, thrust and aerodynamic drag.

**What are the major factors that determine the maximum altitude of a high power rocket in vertical flight?**- Lift-off weight, propellant weight and motor thrust.
- Fin size, propellant weight and motor thrust.
- Motor thrust, weight and aerodynamic drag.

**For an inherently stable rocket, what is the relationship of center of gravity (CG) to the center of pressure (CP)?**- The CG must be behind the CP relative to the desired direction of flight.
- The CG must be forward of the CP relative to the desired direction of flight.
- The CG must be in front of the fins of a rocket.

**A 4" diameter rocket with its motor is determined to have the center of gravity (CG) four inches behind the center of pressure (CP). Is this a stable rocket?**- There is insufficient information to answer this question.
- No, the CP must be behind the CG for the rocket to be stable.
- Yes, the CP is one body diameter in front of the CG.

**The center of pressure (CP) of a rocket is generally defined as:**- The balance point of the rocket without the motor.
- The total area of the fins, airframe and nose cone divided by two.
- The point at which aerodynamic lift on a rocket is centered.

**What is the "rule-of-thumb" for a stable rocket?**- That the center of gravity is one body diameter in front of the center of pressure.
- That the center of gravity is at the same point as the center of pressure.
- There is no rule-of-thumb because there are too many variables.

**When determining the center of gravity (CG) of a rocket with a heavier motor at the launch site, one can:**- Install the motor, recovery system and payload and determine the balance point of the rocket as it is ready for flight.
- Balance the rocket with an empty motor because that is the condition of the rocket after motor burnout.
- It is not necessary to test for the center of gravity when using a more powerful motor because it has more thrust.

**What happens to the center of gravity (CG) of a rocket during a solid rocket motor's thrusting phase?**- The Center of gravity stays the same.
- The Center of gravity shifts forward.
- The center of gravity shifts aft.

**How can a statically unstable rocket be made stable?**- Using a heavier motor.
- Adding weight to the nose.
- Making the rocket shorter.

**What are three methods used to shift the center of gravity (CG) of a rocket forward?**- Add weight to the nose, make the rocket longer, install larger fins.
- Add weight to the nose, make the rocket longer, use a smaller (or lighter) motor.
- Add weight to the nose, make the rocket shorter, use a smaller motor.

**What are three methods used to shift the center of pressure (CP) aft?**- Make the rocket shorter, use larger fins, increase the number of fins.
- Make the rocket shorter n use smaller fins, add weight to the nose.
- Make the rocket shorter n change the number of fins, use a longer launch rod,

**What is the definition of coefficient of drag (Cd)?**- A dimensionless number that represents the effect of gravity and Mach number of the rocket.
- A dimensionless number representing the rocket configuration, Mach number and angle of attack.
- A dimensionless number that represents the friction of the launcher and launch velocity.

**What happens to the coefficient of drag (Cd) as the rocket approaches the speed of sound?**- The Cd decreases.
- The Cd stays the same.
- The Cd increases.

**For a subsonic rocket, what major factors affect the coefficient of drag (Cd)?**- Motor thrust, body diameter, nosecone shape and fin shape.
- Speed, airframe dimensions, nosecone shape and fin shape.
- Gravity, airframe dimensions, nosecone shape and fin shape.

**What effect does a boat tail have on a subsonic rocket's coefficient of drag (Cd)?**- No effect, a boat tail is only a cosmetic design feature.
- It increases the Cd by changing the airflow over the fins.
- It decreases the Cd by reducing the base drag.

**The flight of a high power rocket can be separated into three portions; they are:**- Ignition, burnout and peak altitude.
- Powered flight, un-powered ascent and peak altitude.
- Powered flight, un-powered ascent and descent.

**What is the thrust curve of a regressive motor burn?**- A regressive burn has a high initial thrust relative to the ending thrust of the motor.
- A regressive burn has a lower initial thrust relative to the ending thrust.
- The thrust curve is flat.

**What is the thrust curve of a progressive motor?**- A progressive burn has a high initial thrust relative to the ending thrust of the motor.
- A progressive burn has a lower initial thrust relative to the ending thrust.
- The thrust curve is flat.

**Why does a Bates grain have an essentially neutral thrust curve?**- Because core burning motors always have a regressive burn.
- Because the burn area of the motor remains relatively constant.
- Because the core in the motor grain has a uniform burn area over time.

**What is the function of a motor liner and the O-ring seals in a solid rocket motor?**- To hold all of the parts in place prior to ignition of the rocket motor.
- To make the motor easier to clean if it is a reloadable motor.
- To keep the hot gasses of the motor from burning or melting the motor Case.

**What is the most common oxidizer in commercially available high power composite solid rocket motors?**- Ammonium Perchlorate.
- Ammonium Nitrate.
- Ammonium Chlorate.

**What is NH**_{4}ClO_{4}?- Ammonium Perchlorate.
- Ammonium Nitrate.
- Ammonium Chlorate.

**A small hole is typically recommended near the top, but below the nosecone or payload section, of a high power rocket's booster section. Why?**- This hole allows excessive ejection charge pressures to vent to reduce shock cord stress.
- The hole is used to give air pressure readings for on-board altimeters.
- The hole vents internal air pressure as the rocket gains altitude to prevent premature separation.

**What happens when changing to smaller or fewer injector orifices in an ideal hybrid rocket motor (assume the oxidizer weight stays the same)?**- The total impulse decreases and the average thrust increases.
- The total impulse stays the same and the average thrust increases.
- The total impulse stays the same and the average thrust decreases.

**What happens when changing to more or larger injector orifices in an ideal hybrid rocket motor (assume the oxidizer weight stays the same)?**- The total impulse decreases and the average thrust increases.
- The total impulse stays the same and the average thrust increases.
- The total impulse stays the same and the average thrust decreases.

**What is the oxidizer most commonly used in a commercial hybrid rocket motor?**- N
_{2}O - N
_{2}O_{4} - NO
_{2}

- N
**What is the nominal tank pressure of a nitrous oxide hybrid motor at 75°F?**- 100 psi
- 750 psi
- 1500 psi

**Above what temperature does pressurized nitrous oxide change to a gas?**- 97°F
- 75°F
- 37°F

**A rocket with a motor cluster consisting of a central composite motor and four black powder motors using thermalite igniters or electric matches:**- will result in all motors starting about the same time.
- will result in the composite motor starting first followed by the black powder motors.
- will result in the black powder motors starting first followed by the central composite motor.

**What typically happens to a marginally stable rocket with a hybrid motor during the thrusting phase?**- Nothing.
- The rocket may become more stable.
- The rocket may become less stable.

**In general terms, the specific impulse of a rocket motor is:**- The total thrust force of a motor throughout its action time.
- The total impulse divided by unit weight of propellant.
- Dependent on the diameter and length of the propellant grain.

**In general terms, the total impulse of a rocket motor can be described as:**- The product of the average motor thrust and its burn time.
- The product of the propellant weight and its burn time.
- The product of the propellant weight and the motor thrust.

**The average thrust of a rocket motor is 100 Newtons and the burn time is 4 seconds, what is the total impulse?**- 25 Newton-seconds
- 400 Newton-seconds
- 400 newtons

**Which motor has a higher total impulse?**- J200
- J400
- K200

**Which motor has a higher average thrust?**- J200
- J400
- K200

**What is the difference between a J640 and a J320 high power rocket motor (assume full 1280 Newton-second J motors)?**- The J320 burns out twice as fast as the J640.
- There is no difference between the motors, the numbers are manufacturer reference only.
- The J640 burns out twice as fast as the J320.

**Which of the following has a total impulse in the J motor range?**- It = 600 Newton-seconds
- It = 1000 Newton-seconds
- It = 1290 Newton-seconds

**What is a Newton?**- The amount of force required to accelerate one pound one foot per second per second.
- The amount of force required to accelerate one kg, one foot per second per second.
- The amount of force required to accelerate one kg, one meter per second per second.

**What does the motor designation I220-8 mean?**- The motor is in the I impulse range with an average thrust of 220 Newtons and an 8 second delay from motor ignition.
- b. The motor is in the I impulse range, having a total impulse of 620 Newton-seconds with an average thrust of 220 Newtons and an 8 second delay from motor burn-out.
- The motor is in the I impulse range with an average thrust of 220 Newtons and an 8 second ejection delay from motor burn-out.

**What is the difference in kinetic energy between two identical rockets, one descending at 30 feet per second, the other descending at 60 feet per second?**- Cannot be determined without the weight.
- Two times as much energy.
- Four times as much energy.

**The equation for determining the energy of a moving body (such as a rocket) is:**- E = 1/2 mv
^{2} - E = ma
^{2} - E = mv
^{3}

- E = 1/2 mv
**What is the purpose of a launch rod, rail or tower?**- To keep the rocket pointing in the right direction prior to flight.
- To control the rocket's flight long enough to allow aerodynamic stability.
- Both a and b.

**What is the purpose of a launch lug?**- To add drag to the rocket at launch.
- To guide the rocket along the launch rod or rail.
- Both a and b.

**A rocket with a motor cluster consisting of a central composite 54mm J415 motor and four 29mm G80 composite motors using thermalite igniters or electric matches:**- will result in all motors starting about the same time.
- will result in the J415 motor starting first followed by the G80's.
- will result in the G80's starting first followed by the J415.

**What can happen if all the motors of a cluster do not ignite at launch?**- Nothing, the rocket is inherently stable.
- The rocket may not fly straight.
- The rocket will shred.

**What is a shred?**- A failure of the rocket air frame during boost resulting in destruction of the rocket.
- A failure of the recovery system during boost.
- A failure of the motor causing early ejection.

**What is a cato?**- A failure of the rocket resulting in failure of the air frame during boost.
- A failure of the recovery system during boost.
- A failure of the motor causing flight termination.

**What is the primary requirement for a rocket motor ignitor?**- It must transfer sufficient heat to the propellant to assure ignition.
- It must produce hot, high velocity gasses to assure ignition.
- It must have a high resistance to be reliable.
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