The Astronomy Book

245

moon landing, many technological
hurdles needed to be overcome.
One of the first was the method of
getting to the moon. Three options,
known as mission architectures,
were on the table. The direct ascent
(DA) profile, or “all-the-way,” required
an enormous multistage rocket
with enough fuel on board to
transport the crew back to Earth.
This was initially the favored
approach. However, it was also
the most expensive, and doubts
were raised over the feasibility
of building such a monster rocket
before the 1969 deadline.
In the Earth-orbit rendezvous
(EOR) profile, a moon-bound rocket
ship would be assembled in space
and dock with modules that had
already been placed in orbit. Lifting
things into space is the most
energy-consuming part of any off-
Earth mission, but multiple rocket
launches would sidestep the need
for a single spaceship. This was the
safest option, but it would be slow.

The real weight-savings came

with the lunar-orbit rendezvous

(LOR) profile. Here, a smaller rocket

would put a three-part spaceship

on course to the moon. At the

moon, a command module would

remain in orbit with the fuel for the

journey home, while a lightweight

two-stage lunar lander would be

sent to the surface. This quick and

comparatively cheap option carried

See also: The launch of Sputnik 208–09 ■ Understanding comets 306–11 ■ Exploring Mars 318–25

NEW WINDOWS ON THE UNIVERSE

Project Mercury astronaut John

Glenn enters the Friendship 7 on

February 20, 1962. His mission, lasting

just under five hours, was the US’s

first manned orbital spaceflight.

We choose to go

to the moon.

With the Soviets ahead

in the Space Race, the US

wants to catch up.

A mission to

the moon requires

enormous investment,

which the Soviets would

not be able to match.

with it the very real risk of leaving

a crew stranded in space should

anything go wrong. After much

debate and lobbying, influential

figures, such as Wernher von

Braun, director of NASA’s Marshall

Space Flight Center, threw their

backing behind LOR, and in 1962,

LOR was chosen. This was the first

of many leaps of faith for Apollo.

Technological hurdles

On February 20, 1962, John Glenn

became the first American to orbit

Earth, looping three times around

the planet in Friendship 7, as

part of the US’s first spaceflight

program, Project Mercury, which

ran from 1958 to 1963. Three more

successful Mercury flights followed,

but there was a big difference

between operations in low Earth

orbit and landing on the moon. An

entire new fleet of launch vehicles

was required. Unlike Mercury

spacecraft, which carried a single ❯❯