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<h2 class="hd hd-2 unit-title">Changing Orbital Altitude</h2>
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<h2>4.5.1 Changing Orbital Altitude</h2>
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<p>Now that we have seen how the energy of an orbit is related to its size and shape, in the next video Prof. Hoffman explains how that relationship can be used to change a spacecraft's orbital altitude, whether to reach a destination further away or to return to Earth at mission's end.</p>
<!--<p><span style="color: #ff0000;"><strong>Text blurb draft: Now that you have seen how the energy of an orbit relates to its size and shape, this video will explain how we can use that relationship to change a spacecraft's orbital altitude, whether to reach a destination further away or to return to Earth at mission's end.<br /></strong></span></p>-->
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<h3 class="hd hd-2">Video: Changing Orbital Altitude, Part 1 of 2</h3>
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<h2 class="hd hd-2 unit-title">The Hohmann Transfer</h2>
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<h2>4.5.2 The Hohmann Transfer</h2>
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<p style="text-align: center;"><em><span style="font-family: 'Open Sans', Verdana, Arial, Helvetica, sans-serif;">Illustrated examples of using the Hohmann Transfer to change orbital altitude in order to reach Mars (left) or Venus (right) (Image credit: <a href="http://www2.jpl.nasa.gov/basics/bsf4-1.php">NASA/JPL</a>)</span></em></p>
<p>In the previous video, we learned that an instantaneous change in velocity can change a spacecraft's orbit from a circular orbit to an elliptical one. However, this maneuver alone is not sufficient to change orbital altitude, since the spacecraft will eventually return to the initial point where the change in velocity occurred. Instead, we have to go one step further to "circularize" the elliptical orbit by performing a Hohmann Transfer. As Prof. Hoffman explains in the following video, the Hohmann Transfer uses two velocity changes at different locations to move a spacecraft between two circular orbits of varying sizes.</p>
<!--<p><span style="color: #ff0000;"><strong>Text blurb draft: In the previous video, you saw how an instantaneous change in velocity can change a spacecraft's orbit from a circular orbit to an elliptical orbit. If the spacecraft remains in space, however, it will return to the point where the change in velocity occurred. In this video, Prof. Hoffman will explain how the Hohmann Transfer uses changes in velocity at two locations to transfer a spacecraft between circular orbits.<br /></strong></span></p>-->
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<h3 class="hd hd-2">Video: Changing Orbital Altitude, Part 2 of 2</h3>
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<h2 class="hd hd-2 unit-title">Changing Orbital Inclination</h2>
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<h2>4.5.3 Changing Orbital Inclination</h2>
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<p>In addition to changing the size and shape of an orbit, it is also often desirable to change the orientation of an orbit in space while preserving the same size and shape. To do this, we turn our discussion to the topic of orbital inclination. In the next video, Prof. Hoffman lists the six parameters that can be used to exactly describe an orbit and the position of an object within it, and explains why it takes a (perhaps surprisingly) large amount of energy in order to change an orbit's inclination.</p>
<!--<p><span style="color: #ff0000;"><strong>Text blurb draft: In the previous videos, we saw how a spacecraft can change the size and shape of its orbit. It is also often desirable to change the orientation of an orbit in space while preserving its size and shape. In this video, Prof. Hoffman describes six quantities that can be used to describe an orbit and the place of an object in it, and the (perhaps surprisingly) large amount of energy needed to change the inclination, or tilt, of one's orbit.<br /></strong></span></p>-->
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<h3 class="hd hd-2">Video: Changing Orbital Inclination, Part 1 of 2</h3>
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<h2 class="hd hd-2 unit-title">The Influence of Launch Location</h2>
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<h2>4.5.4 The Influence of Launch Location</h2>
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Explain why it is difficult to change the inclination of a spacecraft’s orbit" type="button" id="LD">MO 4.7</button> <button border-radius="2px" class="mo_button" onclick="window.location.href='/courses/course-v1:MITx+16.00x+3T2016/5e0e82a56b234a2aaf12ac0b3359c3c5#MO48';" style="cursor: pointer;" title="MO 4.8:
Explain how the latitude of a launch site affects orbital inclination and the amount of payload that can be put into orbit " type="button" id="LD">MO 4.8</button></p>
<p><span style="line-height: 25.6000003814697px;">Now that we understand why it is extraordinarily difficult to </span><span style="line-height: 25.6000003814697px;">change orbital inclination, we discuss the implications of this challenge for launching spacecraft into orbit. As we will see, not all launch sites are created equal. In the next video, Prof. Hoffman addresses how the location of a launch site influences </span><span style="line-height: 25.6000003814697px;">the \(\Delta V\) required to achieve orbit, as well as the change in inclination needed to reach geostationary orbit.</span></p>
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<!--<p><span style="color: #ff0000;"><strong>Text blurb draft: Now that you have seen how difficult it is to change one's orbital inclination, in this video, Prof. Hoffman will explain how the location of one's launch site influences the change in inclination needed to achieve geostationary orbit, and even the \(\Delta v\) needed to reach orbit in the first place.<br /></strong></span></p>-->
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<h3 class="hd hd-2">Video: Changing Orbital Inclination, Part 2 of 2</h3>
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