Saturday, July 01, 2006

The Return of EOR

President Kennedy committed America to land men on the Moon and return them safely before the decade of the 1960s was over. History will record that America did do it with Apollo 11. And the US went back five more times after that.

Back in 1961 there were competing ideas of how to get to the Moon. The method that was finally chosen is called Lunar Orbit Rendevous [LOR] in which Apollo would proceed to the Moon. Once in orbit, two astronauts would climb into a lunar lander, visit the Lunar surface, lift off, rendevous with the Apollo CSM, transfer, and then fire the Service Module's main engine to return to Earth.

There was another idea on how to do it. It was called Earth Orbit Rendevous [EOR]. EOR was about launching components into orbit and assembling in Earth orbit the spaceship that would land on the Moon and return.

With Ares I and Ares V, NASA has returned to its roots. These two new rockets are designed around the EOR concept. EOR back in 1961 was abandoned because it demanded high precision in launching many payloads in short order in order to assemble the Moonship. What makes EOR feasible now? The International Space Station makes EOR more attractive since NASA/ESA/Russia can launch components of the ship, link them with the ISS, and take their time putting the parts together before heading out to the Moon and later Mars.

As the whole Orbiter concept was a compromise created in the 1970s amidst tight budgets, so too is Ares it seems. Ares I and Ares V both use five segment SRBs like the ones used with the Shuttle. The crew module is the same squat but aerodynamic shape as the Apollo Command Module. Another nod to NASA's Apollo/Saturn lineage is the use of the J-2X engine. This is actually a good choice of engines as it produces 225,000 lbs of thrust when Saturn used it. And for a bit of extra safety, the J-2 can be shut down and fired again which is what happened with the third stage of a Saturn V. Once that stack was in orbit the J-2 engine would shut down while the astronauts and groundside checked out the whole stack before giving the go ahead for the Moon trip. Then that single J-2 would fire to put Apollo on its course to the Moon.

Hopefully Ares will be as troublefree as the entire Saturn IB/V family was in getting the US to the Moon, Skylab, and the Apollo-Soyuz mission.

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