L2 HPR Technical Quiz

#1. Which of Newton’s Laws best describes the behavior of a rocket motor?

a.Newton’s First Law: A 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

b.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

c.Newton’s Third Law: To every action there is always an equal and opposite reaction

#2. How does Newton’s Third Law “To every action there is always an equal and opposite reaction” relate to rocketry?

a.That the blast deflector must be strong enough to push the rocket off the launch pad at ignition.

b.That a rocket flies because the rocket motor “pushes” the rocket in a direction opposite of the exhaust jet.

c.That the thrust of a rocket motor is proportional to the air density at the launch site

#3. What are the three forces acting upon a rocket during flight?

a.Thrust, rocket diameter and finish

b.Nose cone shape, thrust and drag

c.Gravity, thrust and aerodynamic drag

#4. What are the three major factors that determine the maximum altitude of a high-power rocket in vertical flight?

a.Lift-off weight, propellant weight and motor thrust

b.Fin size, propellant weight and motor thrust

c.Motor thrust, rocket weight, and aerodynamic drag

#5. For an inherently stable rocket, which statement about the center of gravity (CG) and the center of pressure (CP) is true?

a.The CG must be behind the CP relative to the desired direction of flight

b.The CG must be forward of the CP relative to the desired direction of flight

c.The CG must move forward (in the desired direction of flight) during the motor burn

#6. 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 rocket likely to be stable?

a.No, the CG should be at least two body diameters behind the CP

b.No, the CP must be behind the CG for the rocket to be stable

c.Yes, the CP is one body diameter in front of the CG

#7. The center of pressure (CP) of a rocket is generally defined as:

a.The balance point of the rocket without the motor

b.The total area of the fins, airframe and nose cone divided by two

c.The point at which aerodynamic lift on a rocket is centered

#8. What is the “rule-of-thumb” for a stable rocket?

a.That the center of gravity should be at least one body diameter in front of the center of pressure

b.That the center of gravity should be very nearly at the same point as the center of pressure

c.The rocket should balance near or at the center of gravity

#9. You are at the launch site and decide to fly your rocket on a heavier motor than you simulated it on. Which statement regarding CG is true?

a.One can install the motor, recovery system and payload and determine the balance point of the rocket as it is ready for flight

b.One can balance the rocket with the motor hardware alone because that is the condition of the rocket after motor burnout

c.It is not necessary to test for the center of gravity when using a heavier motor because it has more thrust

#10. What ordinarily happens to the center of gravity (CG) of a rocket during a solid rocket motor’s thrusting phase?

a.The CG stays the same

b.The CG shifts forward

c.The CG shifts aft

#11. How can a statically unstable rocket be made stable?

a.Using a heavier motor

b.Adding weight to the nose

c.Making the rocket shorter

#12. What are three methods used to shift the center of gravity (CG) of a rocket forward?

a.Add weight to the nose, make the rocket longer, install larger fins

b.Add weight to the nose, make the rocket longer, use a smaller (or lighter) motor

c.Add weight to the nose, make the rocket shorter, use a smaller motor

#13. What are three methods used to shift the center of pressure (CP) aft?

a.Make the rocket shorter, use larger fins, increase the number of fins

b.Make the rocket shorter, use smaller fins, add weight to the nose

c.Make the rocket shorter, change the number of fins, use a longer launch rod

#14. The definition of coefficient of drag (Cd) is:

a.A dimensionless number that represents the effect of gravity and Mach number of the rocket

b.A dimensionless number dependent on the rocket configuration, Mach number and angle of attack

c.The force, in Newtons, exerted on the rocket by the atmosphere

#15. What happens to the coefficient of drag (Cd) as the rocket approaches the speed of sound?

a.The Cd decreases

b.The Cd stays the same

c.The Cd increases.

#16. For a subsonic rocket, what factors most greatly affect the coefficient of drag (C d)?

a.Motor thrust, body diameter, nosecone shape and fin shape

b.Speed, airframe dimensions, nosecone shape and fin shape

c.Gravity, airframe dimensions, nosecone shape and fin shape

#17. What effect does a boat tail have on a subsonic rocket’s coefficient of drag (C d)?

a.No effect, a boat tail is only a cosmetic design feature

b.It increases the Cd by changing the airflow over the fins

c.It decreases the Cd by reducing the base drag

#18. The flight of a high-power rocket can be separated into three portions; they are:

a.Ignition, burnout and peak altitude

b.Powered flight, un-powered ascent and peak altitude

c.Powered flight, un-powered ascent and descent

#19. Which describes the thrust curve of a regressive motor burn?

a.A high initial thrust relative to the ending thrust of the motor

b.A lower initial thrust relative to the ending thrust

c.The thrust curve is flat

#20. Which describes the thrust curve of a progressive motor?

a.A general decrease in thrust during the burn

b.A general increase in thrust during the burn

c.About the same thrust at ignition as at burnout

#21. A Bates grain has an essentially neutral thrust curve because:

a.Core burning motors always have a neutral thrust curve

b.The area of burning propellant remains relatively constant

c.The core is centered in the propellant grain

#22. What is the most common function of a motor liner and the O-ring seals in a solid rocket motor?

a.To hold all the parts in place prior to ignition of the rocket motor

b.To make the motor easier to clean if it is a reloadable motor

c.To keep the hot gasses of the motor from burning or melting the motor case

#23. What is the most common oxidizer in commercially available high power composite solid rocket motors?

a.Ammonium Perchlorate

b.Ammonium Nitrate

c.Ammonium Chlorate

#24. What is NH4ClO4?

a.Ammonium Perchlorate

b.Ammonium Nitrate

c.Ammonium Chlorate

#25. A small hole is typically drilled near the top of a high-power rocket’s airframe, below the nosecone or payload section. Why?

a.This hole vents excessive ejection charge pressure, reducing shock cord stress

b.The hole permits on-board altimeters to obtain air pressure readings

c.The hole vents internal air pressure as the rocket gains altitude to prevent premature separation

#26. How do you convert Newtons of thrust to pounds of thrust?

a.Add 4.45 to the number of Newtons

b.Multiply Newtons by 4.45

c.Divide Newtons by 4.45

#27. What is a Newton?

a.1 kg*m/s

b.1 kg*m/s^2

c.1 kg*m

#28. What is the oxidizer most commonly used in a commercial hybrid rocket motor?

a.N2O

b.N2O4

c.NO2

#29. For a rocket with a much less than 10:1 “length to diameter” (L/D) ratio, such as spools and pyramids, what type of drag contributes significantly to stability and makes it possible to fly without much, if any, nose weight?

a.Nose drag

b.Base drag

c.Surface drag

#30. When doing an air-start of an L class motor, which of the following would be considered the safest configuration?

a.A single computer driving a single initiator

b.Two computers each driving one initiator with a 0.5 second delay between firing the two initiators

c.Two computers each driving one initiator with no delay between them

#31. A rocket with a motor cluster consisting of a central composite motor and four black powder motors, using five identical igniters:

a.Will result in all motors starting about the same time

b.Will result in the composite motor starting first followed by the black powder motors

c.Will result in the black powder motors starting first followed by the central composite motor

#32. What typically happens to a marginally stable rocket with a hybrid motor during the thrusting phase?

a.Nothing

b.The rocket may become more stable

c.The rocket may become less stable

#33. In general terms, the specific impulse of a rocket motor is:

a.The total thrust force of a motor throughout its action time

b.The total impulse divided by a unit weight of propellant

c.Inversely related to the diameter and length of the propellant grain

#34. In general terms, the total impulse of a rocket motor can be described as:

a.The product of the average motor thrust and burn time

b.The product of the propellant weight and burn time

c.The product of the propellant weight and the motor thrust

#35. The average thrust of a rocket motor is 100 Newtons, and the burn time is 4 seconds. What is the total impulse?

a.25 Newton-seconds

b.400 Newton-seconds

c. 400 Newtons

#36. Which of the motors listed below has the highest total impulse?

a.J200

b.J400

c.K200

#37. Which of the motors listed below has the highest average thrust?

a.J200

b.J400

c.K200

#38. What is the difference between a J640 and a J320 high power rocket motor (assume full 1280 Newton-second J motors)?

a.There is no difference between the motors, the numbers are manufacturer reference only

b.The J320 burns out twice as fast as the J640

c.The J640 burns out twice as fast as the J320

#39. Which of the following has a total impulse (It) in the J motor range?

a.It = 600 Newton-seconds

b.It = 1000 Newton-seconds

c.It = 1290 Newton-seconds

#40. What is a Newton?

a.The amount of force required to accelerate one pound one foot per second per second

b.The amount of force required to accelerate one kg one foot per second per second

c.The amount of force required to accelerate one kg one meter per second per second

#41. What does the motor designation I220-8 mean?

a.The motor has between 320-640 N-s of impulse, an average thrust of 220 Newtons, with approximately 8 seconds between motor ignition and ejection

b.The motor has 220 N-s of impulse, an average thrust of 220 Newtons, with 8 seconds between motor burn-out and ejection

c.The motor has between 320-640 N-s of impulse, an average thrust of 220 Newtons, with approximately 8 seconds between motor burn-out and ejection

#42. Rocket A is descending at 10 feet per second, rocket B weighs the same but is descending at 20 feet per second. Which statement is true?

a.The two rockets have the same kinetic energy

b.Rocket B has two times the kinetic energy of rocket A

c. Rocket B has four times the kinetic energy of rocket A

#43. Rocket A weighs twice as much as rocket B. Both are descending at 20 feet per second. Which statement is true?

a.The two rockets have the same kinetic energy

b.Rocket A has two times the kinetic energy of rocket B

c.Rocket A has four times the kinetic energy of rocket B

#44. What is the purpose of a launch rod, rail or tower?

a.To keep the rocket pointing in the right direction prior to flight

b.To control the rocket’s flight long enough to allow aerodynamic stability

c.Both a. and b.

#45. What is the purpose of a launch lug or rail buttons?

a.To add drag to the rocket at launch

b.To guide the rocket along the launch rod or rail

c.Both a. and b.

#46. For a cluster rocket, which construction technique will minimize the effect of one motor failing to ignite?

a.Make the holes in the forward centering ring slightly closer to the rocket’s centerline than those of the aft centering ring

b.Space the centering rings precisely one motor length apart

c.Use four smaller fins instead of three larger fins

#47. What can happen if all the motors of a cluster do not ignite at launch?

a.Nothing, if the rocket is inherently stable

b.The rocket may not fly straight

c.The rocket will shred

#48. What is a shred?

a.A failure of the rocket air frame during boost resulting in destruction of the rocket

b.A failure of the recovery system during boost

c.A failure of the motor causing early ejection

#49. What is a Cato?

a.A failure of the rocket resulting in failure of the air frame during boost

b.A failure of the recovery system during boost

c. A failure of the motor causing flight termination

#50. What is the primary requirement for a rocket motor ignitor?

a.It must transfer sufficient heat to the propellant to assure ignition

b.It must produce hot, high velocity gasses to assure ignition

c.It must have a high resistance to be reliable

#51. Most APCP (ammonium perchlorate composite propellant) rocket motors are central- burning rather than end-burning:

a.Because most APCP has a specific impulse that is too low for end-burning motors

b.Because most APCP has a burn rate that is too low for useful end-burners

c.The premise is incorrect; most APCP motors ARE end-burners

#52. Which of the following is most likely in dual-deployment rockets that use a drogue and a main parachute?

a.The drogue and the main can tangle if not properly arranged

b.The drogue slows the rocket too much and it drifts too far

c.The drogue does not slow the rocket enough and it lands hard

#53. When using an accelerometer-based altimeter in a rocket that may exceed Mach 1:

a.A “Mach delay” must be built into the altimeter to avoid deployment of the recovery system at Mach

b.One or more access holes must be drilled in the electronics bay to permit access to the atmosphere during flight

c.Neither a. nor b. need be done

#54. When using a pressure-sensor altimeter in a rocket that will not reach Mach 1:

a.One or more access holes must be drilled at the base of the nose cone to permit access to the atmosphere during flight

b.A timer, but not a motor delay, may be used as backup for deployment

c.One or more holes must be drilled in the electronics bay for atmospheric access

#55. What is the major issue with accelerometer-based altimeters?

a.They are larger, and usually much more expensive, than pressure-sensor altimeters.

b.They do not have multiple capabilities such as dual deployment, ignition of air-starts, etc.

c.They may not deploy properly if the flight is significantly off-vertical

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