Ask Ethan #55: Could a Manned Mission to Mars Abort? - Starts With A Bang! - Medium - 0 views
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2014 exploration space spaceflight spacecraft spaceexploration spacetravel mars 2014.09.29-TNN
shared by John Lemke on 28 Sep 14
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No humans have ever traveled farther away from Earth than the crew of Apollo 13 did, as they circled around the far side of the Moon close to lunar apogee, achieving a maximum distance of 400,171 km above the Earth’s surface on April 15, 1970. But when the first manned spaceflight to another planet occurs, that record will be shattered, and in a mere matter of days.
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The way we currently reach other worlds with our present technology — or any remote location in the Universe — involves three distinct stages:The initial launch, which overcomes the Earth’s gravitational binding energy and starts our spacecraft off with a reasonably large (on the order of a few km/s) velocity relative to the Earth’s motion around the Sun.On-board course corrections, where very small amounts of thrust accelerate the spacecraft to its optimal trajectory.And gravity assists, where we use the gravitational properties of other planets in orbit around the Sun to change our spacecraft’s velocity, either increasing or decreasing its speed with every encounter.It’s through the combination of these three actions that we can reach any location — if we’re patient and we plan properly — with only our current rocket technology.
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The initial launch is a very hard part right now. It takes a tremendous amount of resources to overcome the Earth’s gravitational pull, to accelerate a significant amount of mass to the Earth’s escape velocity, and to raise it all the way up through the Earth’s atmosphere.
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The most optimal one for a one-way trip to Mars, for those of you wondering, that minimizes both flight time and the amount of energy needed, involves simply timing your launch right.
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When a planet orbits the Sun, there’s a lot of energy in that system, both gravitational energy and kinetic energy. When a third body interacts gravitationally as well, it can either gain some energy by stealing it from the Sun-planet system, or it can lose energy by giving it up to the Sun-planet system. The amount of energy performed by the spacecraft’s thrusters is often only 20% (or less) of the energy either gained-or-lost from the interaction!