A civil engineer in Essen, Germany has determined the transfer orbit which will get astronauts to Mars the quickest.
Walter Hohmann, a civil engineer, spent several years studying physics and astronomy before publishing his book The Attainability of the Celestial Bodies. It may become required reading for NASA mission planners.
Fuel requirements will be central to the architecture of interplanetary spaceflights, Dr. Hohmann expects. To account for this, he solved for the trajectory which requires the least amount of velocity change, or what scientists call “delta V”. Spacecraft produce this acceleration by firing rocket engines.
The most efficient orbit between two planets turned out to be an ellipse that lies tangent to the planets’ orbital paths.
Source: University of Arizona
Such an orbit requires the least amount of energy to achieve when starting from Earth, but has a serious drawback. Least-energy trajectories are also the slowest. For a crewed mission, taking along enough food and oxygen could make a less efficient path ultimately cheaper.
Another problem is waiting for planets to be in the right place for launch. Because Earth orbits the sun faster than the outer planets and slower than the inner planets, the possible alignment for such a transfer trajectory only occurs occasionally. The window to leave for Mars only opens every two years, for example. Launching interplanetary spacecraft at other times would require vastly more fuel.
Nevertheless, astronomers and aerospace engineers find Dr. Hohmann’s discovery extremely useful for designing space missions.
Happy Amazing Breakthrough Day!