FUEL CELLS—ENERGY FOR A POWER-HUNGRY WORLD - Chemistry: Notable Research and Discoveries - page 145

batteries was that the power needs
of manned space flight would re-
quire a large number, especially
since safety concerns necessitated
carrying plenty of backups—once
the astronauts left Earth, they had
to have everything they would ever
need already on board. Weight is
a serious issue in rocket launches;
escaping Earth's gravity requires
tremendous acceleration, and be-
cause of Newton's second law of
motion—acceleration equals force
divided by mass—increasing the
mass of a rocket increases the force
required to accelerate it. NASA
engineers were worried that even
their most powerful rocket would
be unable to accelerate safely to the
required speed if the mass was too
great. Every item was weighed, and
engineers excluded anything not
essential to the mission.
Another power option was to derive energy from sunlight—solar
energy—but in the 1960s, the technology to do this was not quite practi-
cal. Nuclear energy techniques were available, but NASA felt this would
be too risky as well as too heavy.
The best alternative proved to be fuel cells. NASA chose an alkaline
fuel cell, similar to the one Bacon had built, for the Apollo missions,
including Apollo 11, which landed on the Moon on July 20, 1969. These
fuel cells were reliable, efficient, and performed another valuable service
in addition to providing electricity—the reaction produced drinking
water for the astronauts. Three fuel cells, each capable of 28 volts and
weighing 250 pounds (114 kg) on Earth's surface, operated in parallel
on the Apollo flights. Just one of these fuel cells would ensure a success-
ful mission, so two extra cells gave the astronauts a comfortable safety
margin. But the fuel cells performed extremely well, logging thousands
of hours of operation without a failure.

Space shuttle launch (NASA)