Understanding Orbits Orbit Facts Morehead State University Morehead
Understanding Orbits Orbit Facts Morehead State University Morehead, KY Prof. Bob Twiggs RJTwiggs@gmail. com 1
Understanding Orbits This aircraft is flying across the • Longitude country. • Latitude The ground controller radios the • Altitude pilot and wants to get all of the • Horizontal velocity parameters that determine it’s flight, etc. ) what are they? • Heading ( north, south, • Velocity (ascending or descending) SSE-120 Page 105 -6 2
Understanding Orbits Understanding Longitude and Latitude 3 SSE-120
Understanding Orbits Understanding Longitude and Latitude Greenwich, UK 4 SSE-120
Understanding Orbits Understanding Longitude and Latitude Greenwich, UK 5 SSE-120
Understanding Orbits Understanding Longitude and Latitude 6 SSE-120
Understanding Orbits Understanding Longitude and Latitude SSE-120 Page 105 -6 Morehead ~= W 840, N 37. 50 7
Understanding Orbits Satellite Launch Ports 8 SSE-120
Understanding Orbits Launch directions from launch ports 57. 50 Vandenberg AFB ISS 51. 60 Cape Kennedy 28. 50 Polar French Guiana Polar Near Equatorial 9 SSE-120
Understanding Orbits Understanding Longitude and Latitude r = 6378 km What additional orbit launch velocity would be needed to launch to 500 km circular orbit from the equator to the west? What additional orbit launch velocity would be needed to launch to 500 km circular orbit from the equator to the east? 10 SSE-120
Understanding Orbits Understanding Longitude and Latitude r = 6378 km 50 40 30 20 10 q Q = 300 0 r’ r’ = 6378*cos (q) Now can calculate throw velocity at any latitude 11 SSE-120
Understanding Orbits What must be the velocity of the launch vehicle to put a spacecraft into a given orbit? Orbital Velocity - v Altitude - h SSE-120 Page 308 12
Understanding Orbits SSE-120 Page 273 13
Understanding Orbits What determines the velocity of spacecraft in a circular o Altitude: given Velocity of spacecraft Fc v Vcir = 631. 3481 r-1/2 km/sec r Orbit - is from center of the earth – 6378 + alt km Vesc = 892. 8611 r-1/2 km/sec Fg Orbit Period Circumference = 2 pr Time to orbit = distance/velocity Orbit Period = Time to orbit (minutes) SSE-120 Page 181 14
Understanding Orbits Understanding Longitude and Latitude 15 SSE-120
Understanding Orbits Eccentricity e = 2 c/2 a Relationship between conic sections Conic Sections Circle Ellipse Eccentricity e=0 0<e<1 Parabola e =1 Hyperbola e >1 SSE-120 Page 157 16
Understanding Orbits Spacecraft orbit definition • Orbital size, use the semimajor axis, a • Orbital shape, is defined by eccentricity, e • Orientation of the plane in space, uses Ø inclination, i Ø right ascension of the ascending node, Ω X • Orientation of the orbit within the plane is X defined by the argument of perigee, v • Spacecraft’s location in the orbit is X represented by true anomaly, u SSE-120 Page 155 -156 17
Understanding Orbits SSE-120 Page 155 -156 18
Understanding Orbits X X X 19
Understanding Orbits Classic Orbital Elements (COEs) Checklist • Orbit’s size • Orbit’s shape • Orbit’s orientation Ø Orbit plane in space Ø Orbit within the plane • Spacecraft’s location SSE-120 Page 159 20
Understanding Orbits SSE-120 Page 164 21
Understanding Orbits SSE-120 Page 273 22
Understanding Orbits SSE-120 Page 179 23
Understanding Orbits SSE-120 Page 180 24
Understanding Orbits SSE-120 Page 184 25
Understanding Orbits SSE-120 Page 184 26
Understanding Orbits SSE-120 Page 203 27
Understanding Orbits SSE-120 Page 315 28
Understanding Orbits For a zenith pass. A d B 1. What is the distance d in k 2. What is the time it takes the spacecraft to go from A to B? r h 29 SSE-120
Understanding Orbits What is maximum latitude that a geostationary spacecraft can be seen? 30 SSE-120
Understanding Orbits Assessment Time 31 SSE-120
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