Final Examination 2015

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Dominic Banks
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1 THE UNIVERSITY OF SYDNEY School of Aerospace, Mechanical and Mechatronic Engineering AERO 2705: Space Engineering 1 Final Examination 2015 READ THESE INSTRUCTIONS CAREFULLY! Answer at least 4 (four of the following 6 questions. If you answer more than 4 questions in total, your final result will be averaged over all questions attempted. All questions are worth equal marks. Explanation of assumptions and accuracy of results will form a major component of the assessment of each question.

2 Question 1. A chemical rocket is to be used to launch a 1000Kg satellite to a geostationary earth orbit (altitude 37,800Km. It is proposed to use currently available engines with Kerosene fuel and O 2 oxidizer with a specific impulse of approximately 260sec. The rocket will be designed to operate in 3 separate stages, each using the same motor system. Stage 1 weights 348,000 Kg, structural efficiency 9%, stage 2 is 88,000 Kg, structural efficiency 9% and attached to the upper stage is a stage 3 GTO transfer/geo synchronization motor and the payload. The rocket is launched from the Earth's surface (Earth's radius = 6370 Km, from the Cape Canaveral Space center in Florida, USA (Latitude 28.5 o The structural efficiency of the third stage can be estimated to be around 10%. a Calculate the required final velocity of the satellite in GEO. b Calculate required changes in velocity during each stage of the launch and transfer to final orbit. c Calculate the required mass of fuel for the GTO transfer motor Question 2. Your university team is planning to construct and launch a single unit cubesat. It is proposed that the launch will be done using the UCLA Ppod system along with a set of other satellites on a Falcon 9 vehicle from Vandenberg Air Base in California. Give details of all licensing that will need to be obtained before launch. Give details of any manufacturing requirements or testing requirements that would need to be completed before launch. Question 3. A small satellite uses 2 extended solar panels total area 2 m 2. Each panel is made up of a sequence of solar cells that are 28% efficient. The cells are connected in series and parallel in order to suit the requirements of the power conditioning unit that they are connected to. Each cell produces 5V and has an area of approximately 0.11m 2 These solar panels are used to charge a battery system through a 98% efficient power conditioning unit. The conditioning unit has a maximum limit of 5 Amps for any of the power bus lines that are connected to it and has a maximum of 12 regulated power connections. These can be programmed for independent voltages in the range 5V to 50 V. The battery pack operates at 30V and has a nominal 12.5AmpereHour capacity. It has a 5000 cycle recharge life. The main power consuming unit on the satellite power bus is a 100 Watt X-band transmitter (connected on a 28 Volt bus line. The transmitter is designed to run continuously in order to supply the required data to relay satellites and ground stations. The remaining power consumption of all other satellite components can be be assumed to be on average 10 Watts a sketch a connection layout for the solar cells on the panels that would be compatible with the power conditioning unit specifications. b what is the expected life of the power system. c verify that power is available for the transmitter under all conditions encountered in a low earth orbit. Note : solar radiation in LEO is 1366 Watts/m 2 Question 4. Assuming a vehicle and attached boost motor are currently in an equatorial low earth orbit at 700km altitude. The vehicle, not including boost motor weighs 102,000Kg. Estimate the fuel and structural mass required for the boost motor (ISP 320 if the satellite is to be delivered to a solar orbit that would reach the orbit of Mars. Entry to Mars will be done by atmospheric braking. As human passengers are to be on board, the time for the transfer should be no longer than 8 months Comment on the sort of transfer orbit that could be used.

Question 5. A small scientific satellite has been positioned as shown for a sling-shot boost to its orbit. The satellite will sling-shot around Venus.

3 Question 5. A small scientific satellite has been positioned as shown for a sling-shot boost to its orbit. The satellite will sling-shot around Venus. The velocity of the satellite relative to the sun is 7.07km/s radially toward the sun and tangentially 27.93km/s. Assume that the satellite is positioned so that its closest approach to Venus will be at 1000 km altitude. Sketch the satellite's predicted path around Venus. Estimate the change in magnitude of the satellite's velocity from before to after this encounter with Venus.

4 Question 6. The circuit shown in the diagram contains a measurement element Rx which is used to measure temperature. The device is a peizo-resistive material whose resistance changes in proportion to temperature. 10 Ohms for 15 o C, 10.5 Ohms for -30 o, 9.5 Ohms for 60 o C. Predict the variation in output voltage (Vo for the range of temperatures -20 o to +50 o. If the output voltage is to be sent to an Analogue to Digital converter (12 bit accuracy, input range +-1 V, sample rate 100 Hz, specify any additional analogue components that would be required to ensure a good sample is received by the attached computer. What is the average current drawn from the battery by this circuit?

5 OTHER RELEVENT INFORMATION. Gravitational acceleration at any distance from earth can be calculated as, g= GM r 2 Where G is the gravitational constant X Nm 2 /kg 2, M is the mass of the earth 5.98 X kg and r is the radial distance from satellite to the center of the planet. For an ideal rocket motor : Velocity in an Earth orbit is, Circular : Properties of Elliptical Orbits, V periapsis = Δ V =Isp. g 0. ln( M initial M final V = GM r 2GM ( + 2( Elliptical : V 2 =2g 0 R 1 r 2a 1, V apoapsis = 2 GM ( + = ( 2GM 2 R perispsis V periapsis 1, = ( 2 GM 2 V apoapsis 1 Average planetary data.. Distance from Mecury to Sun = 57,900,000,000m. Mass relative to Earth = Radius = 2440Km Distance from Venus to Sun = 108,500,000,000m. Mass relative to Earth = Radius = 6000 Km Distance from Earth to Sun = 149,597,892,000m. Distance from Mars to Sun = 249,200,000,000m. Mass relative to Earth = Radius = 3390 Km Distance from Jupiter to Sun = 779,000,000,000m. Mass relative to Earth = 317 Radius = 69,900 Km Distance from Saturn to Sun = 1,433,000,000,000m. Mass relative to Earth =95 Radius = 58,200Km Period of Earth Orbit = sec Earth's velocity in orbit around Sun = 29,785 m/s Mar's velocity in orbit around Sun = 23,077 m/s Density of Earth atmosphere is approximately ρ=10 ( 7. altitude(km/150 kg/m 3

LAUNCHES AND LAUNCH VEHICLES. Dr. Marwah Ahmed

LAUNCHES AND LAUNCH VEHICLES. Dr. Marwah Ahmed LAUNCHES AND LAUNCH VEHICLES Dr. Marwah Ahmed Outlines 2 Video (5:06 min) : https://youtu.be/8t2eyedy7p4 Introduction Expendable Launch Vehicles (ELVs) Placing Satellite into GEO Orbit Introduction 3 Introduction