Descent and Landing Procedure
Because heat shields and parachutes cannot be used to land on an airless body such as the Moon, a powered descent with a gravity turn is a good alternative. The Apollo lunar module used a slightly modified gravity turn to land from lunar orbit. This was essentially a launch in reverse except that a landing spacecraft is lightest at the surface while a spacecraft being launched is heaviest at the surface. A computer program called Lander that simulated gravity turn landings applied this concept by simulating a gravity turn launch with a negative mass flow rate, i.e. the propellant tanks filled during the rocket burn. The idea of using a gravity turn maneuver to land a vehicle was originally developed for the Lunar Surveyor landings, although Surveyor made a direct approach to the surface without first going into lunar orbit.
Read more about this topic: Gravity Turn
Famous quotes containing the words descent and, descent and/or landing:
“In the world of the celebrity, the hierarchy of publicity has replaced the hierarchy of descent and even of great wealth.”
—C. Wright Mills (1916–1962)
““There is Hawthorne, with genius so shrinking and rare
That you hardly at first see the strength that is there;
A frame so robust, with a nature so sweet,
So earnest, so graceful, so lithe and so fleet,
Is worth a descent from Olympus to meet;”
—James Russell Lowell (1819–1891)
“I foresee the time when the painter will paint that scene, no longer going to Rome for a subject; the poet will sing it; the historian record it; and, with the Landing of the Pilgrims and the Declaration of Independence, it will be the ornament of some future national gallery, when at least the present form of slavery shall be no more here. We shall then be at liberty to weep for Captain Brown. Then, and not till then, we will take our revenge.”
—Henry David Thoreau (1817–1862)