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Question and answers from the advanced study guide.
Which of Newton's Laws best describes the behavior of a rocket motor?
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 a rocket flies because the rocket motor "pushes" the rocket in a direction opposite of the exhaust jet.
What are the three forces acting upon a rocket during the course of its flight?
Gravity, thrust and aerodynamic drag.
What are the three major factors that determine the maximum altitude of a high power rocket in vertical flight?
Motor thrust, weight and aerodynamic drag.
For an inherently stable rocket, which statement about the center of gravity (CG) and the center of pressure (CP) is true?
The CG must be forward of the CP relative to the desired direction of flight
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?
No, the CP must be behind the CG for the rocket to be stable.
The center of pressure (CP) of a rocket is generally defined as:
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 should be at least one body diameter in front of the center of pressure.
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?
One can install the motor, recovery system and payload and determine the balance point of the rocket as it is ready for flight
What ordinarily happens to the center of gravity (CG) of a rocket during a solid rocket motor's thrusting phase?
The CG shifts forward.
How can a statically unstable rocket be made stable?
Adding weight to the nose
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, use a smaller (or lighter) 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
The definition of coefficient of drag (Cd) is:
A dimensionless number dependent on the rocket configuration, Mach number and angle of attack
What happens to the coefficient of drag (Cd) as the rocket approaches the speed of sound?
The Cd increases.
For a subsonic rocket, what factors most greatly affect the coefficient of drag (Cd)?
Speed, airframe dimensions, nosecone shape and fin shape.
What effect does a boat tail have on a subsonic rocket's coefficient of drag (Cd)?
It decreases the Cd by reducing the base drag.
The flight of a high power rocket can be separated into three portions; they are:
Powered flight, un-powered ascent and descent.
Which describes the thrust curve of a regressive motor burn?
A high initial thrust relative to the ending thrust of the motor.
Which describes the thrust curve of a progressive motor?
A general increase in thrust during the burn
A Bates grain has an essentially neutral thrust curve because:
The area of burning propellant remains relatively constant.
What is the function of a motor liner and the O-ring seals in a solid rocket 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
What is NH4ClO4?
Ammonium Perchlorate
A small hole is typically drilled near the top of a high power rocket's airframe, below the nosecone or payload section. Why?
The hole vents internal air pressure as the rocket gains altitude to prevent premature separation.
What happens when the injector orifice in an ideal hybrid rocket motor is made smaller (assuming the oxidizer weight stays the same)?
The total impulse stays the same and the average thrust decreases.
What happens when the injector orifice in an ideal hybrid rocket motor is increased in diameter (assume the oxidizer weight stays the same)?
The total impulse stays the same and the average thrust increases.
What is the oxidizer most commonly used in a commercial hybrid rocket motor?
N2O
What is the nominal tank pressure of a nitrous oxide hybrid motor at 75°F?
750 psi
Above what temperature does pressurized nitrous oxide change to a gas?
97°F
A rocket with a motor cluster consisting of a central composite motor and four black powder motors, using five identical igniters:
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?
The rocket may become less stable
In general terms, the specific impulse of a rocket motor is:
The total impulse divided by unit weight of propellant.
In general terms, the total impulse of a rocket motor can be described as:
The product of the average motor thrust and burn time.
The average thrust of a rocket motor is 100 Newtons and the burn time is 4 seconds. What is the total impulse?
400 newton-seconds.
Which of the motors listed below has the highest total impulse? (J200,J400,K200)
K200
Which of the motors listed below has the highest average thrust?(J200,J400,K200)
J400
What is the difference between a J640 and a J320 high power rocket motor (assume full 1280 Newton-second J motors)?
The J640 burns out twice as fast as the J320.
Which of the following has a total impulse (It) in the J motor range?
It = 1000 Newton-seconds.
What is a Newton?
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 has between 320-640 N-s of impulse, an average thrust of 220 Newtons, with 8 seconds between motor burn-out and ejection.
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?
Rocket B has four times the kinetic energy of rocket A.
Rocket A weighs twice as much as rocket B. Both are descending at 20 feet per second. Which statement is true?
Rocket A has twice the kinetic energy of rocket B
What is the purpose of a launch rod, rail or tower?
Both a and b.
What is the purpose of a launch lug or rail buttons?
To guide the rocket along the launch rod or rail.
For a cluster rocket, which construction technique will minimize the effect of one motor failing to ignite?
Make the holes in the forward centering ring slightly closer to the rocket's centerline than those of the aft centering ring.
What can happen if all the motors of a cluster do not ignite at launch?
The rocket may not fly straight.
What is a shred?
A failure of the rocket air frame during boost resulting in destruction of the rocket.
What is a cato?
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 propellent to assure ignition.
Most APCP (ammonium perchlorate composite propellant) rocket motors are central-burning rather than endburning:
Because most APCP has a burn rate that is too low for useful endburners.
What is the major obstacle in most dual-deployment rockets that use a drogue and a main parachute?
The drogue and the main can easily tangle if not properly arranged.
When using an accelerometer-based altimeter in a rocket that may exceed Mach 1:
Neither a nor b need be done
When using a pressure-sensor altimeter in a rocket that will not reach Mach 1:
One or more holes must be drilled in the electronics bay for atmospheric access.
What is the major issue with accelerometer-based altimeters?
They may not deploy properly if the flight is significantly non-vertical.
What is generally covered in the scope of NFPA 1127?
Design and construction of commercial high power rocket motors, high power rocket vehicles and launch operations.
The design and construction of high power rocket motors, high power rocket vehicles and launch operations is detailed in what code?
NFPA 1127 and the Tripoli Safety Code.
Who is exempt from NFPA 1127?
Federal, state and local government, colleges, universities and licensed for-profit businesses engaged in high power rocketry activities.
Individuals, firms, partnerships, joint ventures, corporations or other business entities engaged in high power rocketry activities are exempt from NFPA 1127 until what point?
When selling to qualified users in conformance with NFPA 1127.
What is the purpose of NFPA 1127 and the Tripoli Safety Code?
To provide safe and reliable motors, establish flight operations guidelines and prevent injury
What is the Authority Having Jurisdiction?
The organization, office or individual responsible for approving equipment, an installation or a procedure.
What is a complex high power rocket?
a. A rocket having more than one stage. b. A rocket having a cluster of rocket motors.
Either a or b.
What are the minimum criteria that defines a high power rocket?
a. 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.
b. A rocket with a single motor having an average thrust in excess of 80 Newtons.
Either a or b.
What is the lower weight limit of a high power rocket? (Maximum weight of a model rocket with motors installed)
A rocket weighing more than 53 ounces
When is a recovery device not necessary in a high power rocket?
A recovery device is always necessary.
A high power rocket may be constructed of what materials?
Paper, wood, fiberglass or plastic with a minimum amount of metallic parts
What is a high power rocket motor? (At what total impulse and average thrust does a motor become a high power?)
A rocket motor with more than 160 Newton-seconds of total impulse or 80 Newtons average thrust.
What are the structural or load-bearing parts of a high power rocket?
Nose cone, body tube and fins.
Who may operate a high power rocket?
A person that is a certified user
What operating clearances must be complied with for flying high power rockets?
NFPA 1122, NFPA 1127 and Federal Aviation Administration Regulation Part 101.
What criteria apply to the construction of a high power rocket?
Use suitable materials to withstand operating stresses and retain structural integrity in flight
When must the stability of a rocket be determined?
If the safety monitor requests it and whenever the rocket is prepared for flight.
What is the maximum weight of a high power rocket?
Less than maximum liftoff weight recommended by the motor manufacturer for a given motor
When is it permissible to catch a high power rocket?
It is never permissible to catch a high power rocket
What payloads are NOT permitted in a high power rocket?
Payloads that are flammable or explosive or intended to cause harm and vertebrate animals.
When must a high power rocket launching device incorporate a blast deflector?
When necessary to prevent the rocket motor's exhaust from impinging on flammable materials
What is the maximum launch angle from vertical for a high power rocket?
20º
What are the elements of an ignition system?
Remotely controlled, electrically operated, a launch switch that returns to OFF when released and a removable safety interlock in series with the launch switch.
When shall the motor ignitor(s) be installed in a high power rocket motor?
At the launcher or a designated area
When shall firing circuits be armed?
When the rocket is in the launching position (After rocket inspection at the pad or other designated range area as indicated by the launch director)
What is the Launch Site Dimensions Table used for?
As the standard for minimum launch site dimensions
What is the launch site criterion?
No less than 1500 feet and No less than one-half the maximum altitude expected or granted by the FAA
What is the minimum distance from an occupied building or public highway for a launch site?
1500 feet
How close can spectators be to a high power rocket launch?
At the distance defined by, and behind, the Safety Monitor
What is the maximum altitude allowed for flying high power rockets if there is a cloud ceiling of 3000 feet?
Up to the cloud ceiling (3000m)
What is the limit of surface wind for launching a high power rocket?
20 MPH
When may a high power rocket be launched?
After informing and getting permission and attention from the safety monitor
Ammonium perchlorate composite propellant (APCP) reload modules and APCP high power rocket motors shall be stored in what type of container?
A container that provides reasonably safe storage for non-explosive flammable material
What is the minimum distance for smoking (or open flames) from high power rocket motors, motor reloading kits and pyrotechnic modules?
25 feet
What quantity of high power rocket motors, motor reloading kits and pyrotechnic modules may be stored in an indoor magazine?
There is no limit.
According to NFPA 1127, who is permitted to produce for sale a solid propellant high power rocket motor?
A commercial manufacturer
A commercial manufacturer of high power rocket motors may produce what kind of motors?
Either Expendable, solid propellant high power rocket motors or Reloadable non-expendable solid propellant high power rocket motors
What variation is permitted in the certified total impulse and delay time of commercial high power rocket motors?
20%
When may a solid propellant high power rocket motor be shipped and stored with the ignitor installed?
It is never permissible to ship or store a solid propellant high power rocket motor with the ignitor in place
What is the key prerequisite for certification of a solid propellant high power rocket motor?
Prior classification by the U.S. Department of Transportation as a UN Division 1.3 or 1.4 explosive or written acknowledgement of the motor or reload kit as a flammable solid
When must the manufacturer report changes to the authority that originally certified the certified high power rocket motor?
Within 30 days of the change
Who may receive a solid propellant high power rocket motor?
A certified user
What is the age limit Tripoli recognizes for a certified solid propellant high power rocket motor user?
18 years of age
When may a high power rocket motor be used for spectacular displays of color, light and/or sound?
They may not be used for this application
When is the sale, offering for sale and/or exposing for sale of uncertified motors permissible?
It is never permitted
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