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CONCEPT: Elliptical Orbits Consider a spacecraft in an elliptical ...

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NAME:PS 160 Extra Credit Due 22 February 2012Please pr<strong>in</strong>t <strong>an</strong>d staple. Please write your solutions on the question sheet. No po<strong>in</strong>ts will beawarded if I c<strong>an</strong>not underst<strong>an</strong>d what you have written, so please write clearly. Show allcalculations. There are eight questions for a total of 20 po<strong>in</strong>ts.<strong>CONCEPT</strong>: <strong>Elliptical</strong> <strong>Orbits</strong><strong>Consider</strong> a <strong>spacecraft</strong> <strong>in</strong> <strong>an</strong> <strong>elliptical</strong> orbit around Mars. At the low po<strong>in</strong>t, orperigee, of it’s orbit, it is 300 miles above the Mars’s surface. At the high po<strong>in</strong>t, orapogee, it is 3000 miles above the Mars’s surface. (Mars radius R = 3.4 x 10 6 m,<strong>an</strong>d mass M = 6.4 x 10 23 kg (1mile = 1.609 km, G = 6.67 x 10 -11 N m 2 /kg 2 .)a) What is the period of the <strong>spacecraft</strong>’s orbit? (3 po<strong>in</strong>ts)b) Us<strong>in</strong>g the conservation of energy <strong>an</strong>d <strong>an</strong>gular momentum, f<strong>in</strong>d the speed atperigee.(3 po<strong>in</strong>ts)c) Us<strong>in</strong>g the conservation of <strong>an</strong>gular momentum, f<strong>in</strong>d the speed at apogee.(2 po<strong>in</strong>ts)


NAME:d) What is the escape velocity for <strong>an</strong>y object located at a dist<strong>an</strong>ce from Marsequal to the perigee dist<strong>an</strong>ce of the <strong>spacecraft</strong>? (3 po<strong>in</strong>ts)e) What is the escape velocity for <strong>an</strong>y object located at a dist<strong>an</strong>ce from Marsequal to the apogee dist<strong>an</strong>ce of the <strong>spacecraft</strong>? (3 po<strong>in</strong>ts)f) It is necessary to have the <strong>spacecraft</strong> escape from the Mars completely. If the<strong>spacecraft</strong>s rockets are fired at perigee, by how much would the speed haveto be <strong>in</strong>creased above orbital velocity to achieve this?(2 po<strong>in</strong>ts)g) It is necessary to have the <strong>spacecraft</strong> escape from the Mars completely. If the<strong>spacecraft</strong>s rockets are fired at apogee, by how much would the speed haveto be <strong>in</strong>creased above orbital velocity to achieve this?(2 po<strong>in</strong>ts)h) Which escape route would cost less fuel – flee<strong>in</strong>g at apogee or perigee?Expla<strong>in</strong> your <strong>an</strong>swer.(2 po<strong>in</strong>ts)

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