Apollo – a spaceship for the Moon

In recent decades, astronauts have been confined to Earth orbit, but history was made when they made their greatest adventure and 12 men travelled to land on and explore the lunar surface.

Early NASA illustrations for the Apollo project showing the mission vehicles. Image credit: NASA

To send humans to the Moon, NASA built its biggest rocket ever, a three-stage monster called Saturn V that stood 11 metres tall, or about as high as a 36-storey building. It would launch the Apollo missions that made history.

Atop the towering rocket was to be a three-part spaceship. One was the Command Module, another conical capsule, but big enough to carry three astronauts in relative comfort. For the trip to the Moon and back, it was attached to a cylindrical Service Module to provide electrical power, propulsion and storage. And tucked behind the assembly, with its three landing legs tucked in, was the Lunar Module that would ferry two astronauts to the lunar surface and launch them back again.

To reach the Moon, the Saturn V would first put the spacecraft into orbit around the Earth where checks would be made that all was well. Then the third stage would fire its engines again to send it towards the Moon. On the three-day journey there, panels protecting the Lunar Module would be jettisoned, and the Command/Service Module separate and turn to dock with the lander, pulling it away from the rocket stage which is now discarded.

The mated modules now go into orbit around the Moon. After a number of orbits, two members of the crew crawl through a hatch into the Lunar Module, it detaches from the rest of the assembly and fires an engine to descend to the Moon’s surface. The third astronaut remains in the orbiting Command Module.

On the Moon, the astronauts climb down a short ladder to the lunar surface. After one or more such excursions, exploring and collecting rock samples, they return to be launched back into space by the Lunar Module’s ascent stage. The base of the lander remains on the Moon.

After rendezvousing and docking with the Command Module again, the astronauts rejoin their companion, and the lander is jettisoned before the Service Module’s engine fires to send them back towards Earth. After another three-day flight, the Service Module is abandoned and the Command Module turns to descend, heat shield first, for re-entry into the atmosphere. Finally the capsule parachutes to splashdown in the Pacific to be picked up by an aircraft carrier.

A smaller Saturn

The Saturn V had a smaller relation, the Saturn IB, that was used to launch four unmanned test flights of Apollo hardware plus the first crewed mission, Apollo 7, which only went into low-Earth orbit with a light payload.

The Apollo IB rocket. Image credit: NASA

Fire on the launch pad

Due to the complexity and daring nature of the Apollo missions, it was always feared that there might be a disaster that could cost astronauts their lives. Few imagined that it would happen, not in space, but during a routine test on the ground. Tragically, that is what happened when the crew for the first planned manned mission, Apollo 1, were carrying out a pre-flight exercise on the launch pad at Cape Kennedy, Florida, in January 1967.

Gemini veterans Gus Grissom and spacewalker Ed White, together with rookie astronaut Roger Chaffee, were trapped inside when an electrical fault caused fire to break out inside the Command Module. Fed by pure oxygen, the blaze raged as the astronauts found themselves unable to open the hatch. The intense heat ruptured the capsule allowing air to flood in, killing the flames but creating dense smoke which killed the three men.

An inquiry into the disaster led to a redesign of the hatch so that it opened outwards, and a change in air supply to a mix of oxygen and nitrogen rather than pure oxygen. Flammable materials in the cabin were replaced with fire-resistant ones. The first crewed Apollo mission, which had been due to fly in February, 1967, did not launch until October 1968.

Next: Apollo 7 – astronauts get the travel bug