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Advanced Certification Study Guide TRIPOLI ROCKETRY ASSOCIATION, INC.
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Which of Newton’s Laws best describes the behavior of a rocket motor?
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Newton’s Third Law: To every action there is always an equal and opposite reaction
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How does Newton’s Third Law “To every action there is an equal and opposite reaction” relate to rocketry?
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That a rocket flies because the rocket motor “pushes” the rocket in a direction opposite the exhaust jet
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What are the three forces acting upon a rocket during the course of its flight?
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Gravity, thrust and aerodynamic drag
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What are the major factors that determine the maximum altitude of a high power rocket in vertical flight?
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Motor thrust, weight, and aerodynamic drag
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For an inherently stable rocket, what is the relationship of center of gravity (CG) to the center of pressure (CP)?
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The CG must be forward of the CP relative to the desired direction of flight
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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?
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No, the CP must be behind the CG for the rocket to be stable
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The center of pressure (CP) of a rocket is generally defined as:
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The point at which aerodynamic lift is centered
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What is the “rule of thumb” for a stable rocket?
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That the center of gravity (CG) is one body diameter in front of the center of pressure (CP)
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When determining the center of gravity (CG) of a rocket with a heavier motor at the launch site, one can:
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Install the motor, recovery system and payload and determine the balance point of the rocket as it is ready for flight
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What happens to the center of gravity (CG) of a rocket during a solid rocket motor’s thrusting phase?
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The center of gravity (CG) shifts forward
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How can a statically unstable rocket be made stable?
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Adding weight to the nose
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What are the three methods used to shift the center of gravity (CG) of a rocket forward?
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Add weight to the nose, make the rocket longer, use a smaller (or lighter) motor
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What are three methods used to shift the center of pressure (CP) aft?
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Make the rocket shorter, use larger fins, increase the number of fins
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What is the definition of coefficient of drag (Cd)?
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A dimensionless number representing the rocket configuration, Mach number, and angle of attack
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What happens to the coefficient of drag (Cd) as the rocket approaches the speed of sound?
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The Cd increases
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For a subsonic rocket, what major factors affect the coefficient of drag (Cd)
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Speed, airframe dimensions, nosecone shape and fin shape
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What effect does a boat tail have on a subsonic rocket’s coefficient of drag (Cd)?
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It decreases the Cd by reducing the base drag
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The flight of a high power rocket can be seperated into three portions; they are:
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Powered flight, un-powered ascent and descent
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What is the thrust curve of a regressive motor burn?
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A regressive burn has a high initial thrust relative to the ending thrust of the motor
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What is the thrust curve of a progressive motor?
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A progressive burn has a lower initial thrust relative to the ending thrust
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Why does a bates grain have an essentially neutral thrust curve?
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Because the burn area of the motor remains relatively constant
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What is the function of a motor liner and the O-ring seals in a solid rocket motor?
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To keep the hot gasses of the motor from burning or melting the motor case
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What is the most common oxidizer in commercially available high power composite solid rocket motors?
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Ammonium Perchlorate
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What is NH 4 ClO 4 ?
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Ammonium Perchlorate
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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?
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The hole vents internal air pressure as the rocket gains altitude to prevent premature seperation
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What happens when changing to smaller or fewer injector orifices in an ideal hybrid rocket motor (assume the oxidizer weight stays the same)?
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The total impulse stays the same and the average thrust decreases
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What happens when changing to more or larger injector orifices in an ideal hybrid rocket motor (assume the oxidizer weight stays the same)?
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The total impulse stays the same and the average thrust increases
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What is the oxidizer most commonly used in a commercial hybrid rocket motor?
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N 2 O, Nitrous Oxide, commonly called NOX
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What is the nominal tank pressure of a nitrous oxide hybrid motor at 75* F?
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750 psi
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Above what temperature does pressurized nitrous oxide change to a gas?
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97*F
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A rocket with a motor cluster consisting of a central composite motor and four black powder motors using thermalite igniters or electric matches:
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Will result in the black powder motors starting first followed by the central composite motor
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What typically happens to a marginally stable rocket with a hybrid motor during the thrusting phase?
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The rocket may become less stable
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In general terms, the specific impulse of a rocket motor is:
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The total impulse divided by unit weight of propellent
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In general terms, the total impulse of a rocket motor can be described as:
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The product of the average motor thrust and its burn time
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The average thrust of a rocket motor is 100 Newtons and the burn time is 4 seconds. What is the total impulse?
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400 newton-seconds
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Which motor has a higher total impulse? J200 J400 K200
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Which motor has a higher average thrust? J200 J400 K200
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J400
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What is the difference between a J640 and a J320 high power rocket motor (assume full 1280 Newton- second J motors)
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The J640 burns out twice as fast as the J320
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Which of the following has a total impulse in the J motor range? I t = 600 Newton-seconds I t = 1000 Newton-seconds I t = 1290 Newton-seconds
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I t = 1000 Newton-seconds
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What is a Newton?
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The amount of force required to accelerate on kilogram one meter per second per second
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What does the motor designation I220-8 mean?
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The motor is in the I impulse range with an average thrust of 220 newtons and an 8 second ejection delay from the motor burn-out
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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?
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Four times as much energy
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The equation for determining the energy of a moving body (such as a rocket) is:
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E=1/2mv 2
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What is the purpose of a launch rod, rail, or tower?
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To keep the rocket pointing in the right direction prior to flight AND to control the rocket’s flight long enough to allow aerodynamic stability
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What is the purpose of a launch lug?
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To guide the rocket along the launch rod or rail
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A rocket with a motor cluster consisting of a central composite 54mm J415 motor and four 29mm G80 composite motors using thermalite igniters or electrical matches:
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Will result in the G80s starting first followed by the J415
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What can happen if all the motors of a cluster do not ignite at launch?
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The rocket may not fly straight
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What is a shred?
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A failure of the rocket airframe during boost resulting in destrtuction of the rocket
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What is a cato?
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A failure of the motor causing flight termination
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What is the primary requirement for a rocket motor igniter?
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It must transfer sufficient heat to the propellant to assure ignition
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What is covered in the scope of NFPA 1127?
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Design and construction of commercial high power rocket motors, high power rocket vehicles and launch operations
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The design and construction of high power rocket motors, high power rocket vehicles and launch operations is detailed in what code?
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NFPA 1127 and the Tripoli Safety Code
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Individuals, firms, partners, joint ventures, corporations or other business entities engaged in high power rocketry activities are exempt from NFPA 1127 until what point?
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When selling to qualified users in conformance with NFPA 1127
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Who is exempt from NFPA 1127?
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Federal, state and local government, colleges, universities and license for-profit businesses engaged in high power rocketry activites
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What is the purpose of NFPA 1127 and Tripoli Safety Code?
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Provide safe and reliable motors, establish flight operations guidelines and prevent injury
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What is the Authority Having Jurisdiction?
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The organization, office or individual responsible for approving equipment, an installation or a procedure
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What is a complex high power rocket?
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A rocket having more than one stage AND a rocket having a cluster of rocket motors
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What are the rocket motor criteria (minimum) that defines a high power rocket?
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A rocket with a single motor with more than 160 Newton-seconds total impulse or an installed impulse of 320 Newton-seconds and no more than 40,960 Newton- seconds AND a rocket with a single motor having an average thrust in excess of 80 Newtons
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What is the lower weight limit of a high power rocket?
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A rocket weighing more than 53 ounces
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When is a recovery device not necessary in a high power rocket?
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A recovery device is always necessary
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A high power rocket may be constructed of what materials?
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Paper, wood, fiberglass, or plastic with a minimum amount of metallic parts
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What is a high power rocket motor?
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A rocket motor with more than 160 Newton-seconds of total impulse or 80 Newtons average thrust
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What are the structural or load bearing parts of a high power rocket?
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Nose cone, body tube, and fins
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Who may operate a high power rocket?
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A person that is a certified user
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What operating clearances must we be in compliance with for flying high power rockets?
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NFPA 1127, Federal Aviation Administration Regulation Part 101 and applicable federal, state and local regulations
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What criteria apply to the construction of a high power rocket?
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Use suitable materials to withstand operating stresses and retain structural integrity in flight
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When must the stability of a rocket be determined?
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Whenever the rocket is prepared for flight
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What is the maximum weight of a high power rocket?
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Less than the maximum weight recommended by the motor manufacturer for a given motor
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When is it permissible to catch a high power rocket?
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It is never permissible to catch a high power rocket
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What payloads are not permitted in a high power rocket?
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Payloads that are flammable or explosive or intended to cause harm AND Vertebrate animals
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When must a high power rocket launching device incorporate a blast deflector?
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When necessary to prevent the rocket motor’s exhaust from impingng on flammable materials
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What is the maximum launch angle from vertical for a high power rocket?
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20*
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What are the elements of an ignition system?
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Remotely controlled, electrically operated, a launch switch that returns to OFF when released and a removable safety interlock in series with the launch switch
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When shall the motor igniter(s) be installed in a high power rocket motor?
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At the launcher or designated area
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When shall firing circuits be armed?
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When the rocket is in the launching position
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What is the launch Site Dimensions Table used for?
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As the standard for minimum launch site dimensions
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What is the alternate launch site criteria?
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No less than 1500 feet AND No less than one-half the maximum altitude expected or granted by the FAA
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What is the minimum distance from an occupied building or public highway for a launch site?
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1500 feet
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How close can spectators be to a high power rocket launch?
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At the distance defined by, and behind, the safety monitor
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What is the maximum altitude allowed for flying high power rockets if there is a cloud ceiling of 3000 feet?
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Neither a nor b
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What is the limit of surface wind for launching a high power rocket?
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20 mph
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When may a high power rocket be launched?
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After informing and getting permission and attention of the safety monitor
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High power rocket motors, motor reloading kits and pyrotechnic modules shall be stored in what type of container?
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A Type 3 or Type 4 indoor/outdoor magazine AND a resealable, non- combustible container
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What is the minimum distance for smoking (or open flame) from high power rocket motors, motor reloading kits and pyrotechnic modules?
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25 feet
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What quantity of high power rocket motors, motor reloading kits and pyrotechnic modules may be stored in an indoor magazine?
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50 pounds
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According to NFPA 1127, who can produce a solid propellant high power rocket motor?
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A commercial manufacturer
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A commercial manufacturer of high power rocket motors may produce what kind of motors?
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Expendable, solid propellant high power rocket motors AND Reloadable non-expendable solid propellant high power rocket motors
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How much variation can there be in the certified total impulse and delay time of commercial high power rocket motors?
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20%
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When may a solid propellant high power rocket motor be shipped and stored with the igniter installed?
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Never
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What is the key prerequisite for certification of a solid propellant high power rocket motor?
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Prior to classification by the U.S. Department of Transportation as a UN Division 1.3 or 1.4 explosive or written acknowledgment of the motor or reload kit as a flammable solid
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When must the manufacture report changes to the authority that originally certified the certified high power rocket motor?
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With in 30 days of the change
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Who may receive a solid propellant high power rocket motor?
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Certified users
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What is the age limit Tripoli recognizes for a certified solid propellant high power rocket motor user?
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18 years of age
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When may a high power rocket motor be used for spectacular displays of color, light and/and or sound?
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They may not be used for this application
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When is the sale, offering for sale and/or exposing for sale of uncertified motors permissable?
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It is never permitted
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When is conveying a high power rocket motor to an uncertified person permitted?
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When the person is preparing to certify as a high power user
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When is it permissible to consume alcohol when prepping or launching high power rockets?
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It is never permitted
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What organizations may certify high power rocket motors?
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Tripoli and NAR
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What organization my certify users of high power rocket motors?
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Tripoli and NAR
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What document has been adopted be the Tripoli Rocketry Association as the Tripoli Safety Code?
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NFPA 1127
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