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Overview of Hobby Rocketry

Chisholm Trail Middle School

November 30, 2010

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TopicsIntroductionsRocketry BasicsRocket MotorsMaterials of ConstructionElectronics

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http://www.aarg.org/ http://groups.yahoo.com/group/rocketry-austin/

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What Can We Learn from Rocketry?Physics – Newton’s Laws & Laws of MotionAerodynamics – Stability, DragElectronics – Flight Computers, GPS, TelemetryMeteorology – Wind, Air PressureComputers – Data Collection, Flight SimulationMathematics – Calculus, TrigonometryEngineering – Problem Solving, MaterialsCraftsmanship, Teamwork & Safety

… and we can have fun too!

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12“L” Motor – 2,560 to 5,120 N-sec

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Rocket MotorsGeneral Types of Rocket Motors

Black powder (A though E motors)APCP (Ammonium perchlorate composite propellant)

“Composite” means a mixture of fuel, oxidizer & binder Hydrocarbon binders & metals are the fuel Ammonium perchlorate - NH4ClO4 - is the oxidizer

Hybrid motors with PVC fuel & N2O oxidizer

Liquid-fueled motors

APCP Motors are made with Multiple “Grains”Grain configuration controls the burn characteristics

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Rocket Airframe MaterialsIn Order of Increasing Strength:

CardboardPhenolic cardboardFiberglassCarbon fiberMetal (aluminum)

Fiberglass with Epoxy and Carbon Fiber with Epoxy are Examples of “Composite” Materials

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Rocketry ElectronicsAltimeters

Detect apogee & break rocket apartDeploy main parachute at low altitude Ignite other motors (multi-stage motors & “air-starts”)

Telemetry & Rocket “Finding” DevicesBuzzers & beepersRadio signals for directional trackingTelemetry & GPS

PayloadsScience & meteorology experimentsWhatever else you can imagine!

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Example GPS Flight Profile

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Altimeter “Apogee” Detection MethodsBarometric Detection

Barometric sensor measures air pressureApogee is sensed when air pressure increasesAdvantages – Measures actual apogeeDisadvantages – Prone to error (e.g., pressure spikes)

Accelerometer CalculationAccelerometer measures positive “G’s” during motor

burn & negative “G’s” during coast phaseApogee is calculated when integral of positive G’s

over time is equal to the integral of negative G’sAdvantages – Not sensitive to pressure variationsDisadvantages – Non-vertical flight profile

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Barometric Pressure vs Altitude

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Altimeter “Apogee” Detection MethodsBarometric Detection

Barometric sensor measures air pressureApogee is sensed when air pressure increasesAdvantages – Measures actual apogeeDisadvantages – Prone to error (e.g., pressure spikes)

Accelerometer CalculationAccelerometer measures positive “G’s” during motor

burn & negative “G’s” during coast phaseApogee is calculated when integral of positive G’s

over time is equal to the integral of negative G’sAdvantages – Not sensitive to pressure variationsDisadvantages – Non-vertical flight profile

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Example Flight Data

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Calculating Apogee from Acceleration Data

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Jim’s Highest Flight (So Far!)TooCarbYen:

Two-stage rocket Booster motor – N4000 Sustainer motor – M1350

Maximum Speed – Mach 2.3 (About 1,740 mph)Altitudes:

Booster motor burnout – 5,000 feet Sustainer motor start – 10,000 feet Sustainer motor burnout – 20,000 feet Maximum altitude – 55,000 feet

Recovered 3 Miles from Launch Site (via GPS)

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TooCarbYen Before Launch