So Meador changed these parameters by small amounts to see what effect this would have on the long term stability of the orbit. Of course, this stability could be the result of the particular set of starting parameters for the spacecraft in the program - the time of jettison, the latitude, longitude and altitude, heading angle and so on. By running the program with and without this force, Meador found that this had little effect on Eagle’s orbit. It can even include the effect of solar radiation pressure. In this way, it calculates how a spacecraft’s orbit changes over time. The program models Eagle as a uniform sphere and includes the effect of numerous, small but relevant forces such as the gravitational pull of the Earth, the Sun and all the planets except Mercury.Īt each point in time, it calculates the effect of all these forces to determine where the spacecraft will be at the next point in time and then repeats. Meador loaded the program with GRAIL’s lunar gravitational field and then used it to work out what must have happened to Eagle after Columbia jettisoned it in 1969.
This models a spacecraft’s trajectory in any gravitational field and is widely used to simulate missions to Earth orbit, to the Moon, to Mars and beyond. Meador began his task using an open-source program called the General Mission Analysis Tool developed by NASA and others. Apollo 13 astronauts famously used their ascent module as a lifeboat to get back to Earth, where it burnt up in the atmosphere. Deliberate Crashesīy contrast, the lunar ascent modules from Apollos 12, 14, 15, 16 and 17 were all deliberately crashed into the Moon to help calibrate seismometers that astronauts had left on the surface. That could point observers to the impact crater that is Eagle’s final resting place. So why not use this map to work out how Eagle’s orbit must have decayed and where it might have eventually hit the lunar surface.
Nobody knows what happened to Eagle after NASA abandoned it. In 2012, NASA sent a pair of spacecraft called GRAIL to map the Moon’s gravitational field and this mission eventually created a detailed map of this varying field. Instead, underground concentrations of mass lead to tiny variations in the Moon’s gravitational field that make most lunar orbits unstable in the long term. Planetary geologists have long known that the Moon’s mass is not evenly distributed throughout its volume. Indeed, the spacecraft might still be visible from Earth to anybody willing to look hard enough to find it. “There exists some possibility that this machine might have reached an inert state, allowing it to remain in orbit to the present day,” says independent researcher James Meador. Now, a new analysis suggests that Eagle is still up there, in essentially the same orbit that Columbia left it in. NASA has always assumed that this orbit was unstable and that some time later, Eagle must have crashed into the lunar surface.
The crew then closed the hatch and the command module returned to Earth.īefore leaving, though, it jettisoned Eagle, leaving the ascent module in a retrograde orbit some 125 kilometers above the lunar equator. After docking, Neil Armstrong and Buzz Aldrin clambered back into Columbia carrying 22 kilograms of lunar rock. On July 21, 1969, Apollo 11’s Eagle lunar ascent stage lifted off from the surface of the Moon to rendezvous with the command module Columbia in orbit.
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