Orion vs. Apollo: NASA's new moonshot

From the Earth to the moon
During Apollo, a single three-stage Saturn V Moon rocket carried the crew, Command Service Module and the Lunar Module into Earth orbit. After one orbit the Saturn V's third stage was re-ignited and sent Apollo toward the Moon.

After discarding the third stage on the way to the Moon, the Apollo spacecraft entered lunar orbit. At the appropriate time, two of the three crewmen boarded the Lunar Module and went down to the surface, leaving the third crewman in the Command Module.

The plan for Constellation, as it stands now, is to launch a four-person crew in an Orion spacecraft atop an Ares I launch vehicle from the Kennedy Space Center into Earth orbit, where it will wait up to four days, Drake said.

Ninety minutes after the Ares I launch, a heavy-lift Ares V rocket is to launch the Altair lunar landing spacecraft and an Earth Departure Stage into Earth orbit for a same day rendezvous and docking with the Orion capsule.

The joined spacecraft will remain in Earth orbit for up to four days while waiting for the Moon to orbit into the right position when the launch window for a Trans-Lunar Injection opens up. Then the combined spacecraft will blast their way toward the Moon.

After discarding the Earth Departure Stage, the Altair lunar lander's rocket engine — powered by liquid hydrogen and liquid oxygen — will brake the spacecraft into orbit around the moon.

This is different from Apollo, which relied on the Service Module's main service propulsion system engine for the same job.

Location is everything
Although plans for the first mission or so may change, Drake said the baseline plan is for all four astronauts to board Altair for the trip to the lunar surface, leaving an empty Orion spacecraft to circle the moon on its own.

That's a big difference from Apollo, which left one astronaut in the Command Module to keep that spacecraft healthy and the crewmember busy with "bird's eye" science observations of the surface.

As for the selection of a lunar landing site, during Apollo a variety of sites were explored, all generally near the moon's equator. For Constellation, a single site will be selected, likely near one of the poles.

Among the reasons, according to Drake:

With each landing NASA will leave equipment there that can be joined with other hardware to build up a permanent station on the surface. It may be possible to establish this site in a place on the Moon where there is always sunlight, which can help with generating electricity and maintaining the correct thermal conditions with the surface hardware. It is also possible that a crater near the poles that remains in constant darkness may hide water ice, which can be broken down into hydrogen and oxygen for use in powering fuel cells, producing rocket propellant and making drinking water.

Under the hood
Systems inside Apollo versus Orion also will be very different.

While Apollo had a switch for everything, Orion will have glass cockpit displays and touch-sensitive screens that can be programmed on the fly.

While Apollo relied on computers with less power and memory than a digital toy found inside a cereal box, Orion will have the latest computers plugged into an open architecture that allows upgrades to software and hardware.

While Apollo used a pure oxygen atmosphere in space, Orion will use a nitrogen-oxygen mixture at reduced pressure to make it easier for spacewalking or Moonwalking astronauts to depart the spacecraft.

And while Orion's heat shield will use an ablative material and parachutes for a splashdown in the water like Apollo, unlike Apollo there continues to be talk about how much of an Orion spacecraft can be reused after flying, Drake said.

"We have a lot of options on the table," Drake said of the entire Orion system.

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