34 ASTRONOMY • APRIL 2020
LM descent engine, which lasted four
and a half minutes, only two small
course corrections would be made before
approaching the home planet.
The grave circumstances of Apollo 13
became a worldwide sensation. Television
coverage broke in and reported routinely
on the mission, in a special report sce-
nario that harkened back to the assassi-
nation of President John F. Kennedy and
other tragedies. Updates did not look
particularly encouraging for some time,
leading to a sense of panic and a feeling
that a terrible calamity would result. The
small supply of electrical power in the
craft did not allow live television broad-
casts, so news desks passed on the latest
statements and updates, as broadcasters
employed models of the spacecraft to try
to explain to viewers what was happen-
ing and how the mission might end.
Lovell later wrote that using the LM
as a lifeboat for three astronauts really
stretched the limits of what it was
intended to do: It was supposed to sus-
tain two astronauts for about a day and a
half rather than three astronauts for the
four-day return to Earth. The command/
service module produced water as a
byproduct from its fuel cells. But such
was not the case with the LM, which
employed silver-zinc batteries, and so
within the LM, vitally important electri-
cal power and water were in short supply.
Oxygen was less of a concern because the
LM had enough to spare in order to
repressurize the spacecraft’s atmosphere
after each lunar surface activity. But
Kranz and the astronauts all wanted to
minimize the inherent risks, of course,
so they powered down the LM as much
as possible to preserve supplies. This also
helped them keep communications and
life-support functions as stable as pos-
sible until nearing reentry into Earth’s
atmosphere.
Another looming problem that wors-
ened as the cruise toward Earth contin-
ued was carbon dioxide. This, in fact,
proved to be a challenging test for both
the controllers and the crew alike.
Removing carbon dioxide from the LM’s
atmosphere would be critical — too
much buildup of this gas would prove
fatal. Carbon dioxide removal took place
via lithium hydroxide canisters, and the
LM lacked the number required to
remove sufficient carbon dioxide for thereturn cruise home. Further, the backups
were in storage, out of reach, and the
command/service module lithium
hydroxide canisters were incompatible
with the LM. So ground controllers
worked out a plan, communicated it to
the crew, and the astronauts jury-rigged
an outfit to accomplish the task, using
hoses to connect the cubical command
module canisters to the LM’s cylindrical
sockets. They later referred to this
arrangement as “the mailbox.”Back home
As the craft approached Earth, the crew
would have to power up the command
module from scratch. This had never
before been tried during a f light. Given
the craft’s weak power availability, con-
trollers Aaron and Mattingly proposed
a procedure, but they were uncertain.
The extremely cold temperatures within
the spacecraft, which dropped as low as
39 degrees Fahrenheit (4 degrees Celsius),
meant that water had condensed on sur-
faces and alarmed the crew and control-
lers, who thought of potential electrical
shorts. But this did not, in the end, turn
out to be a problem.
Another risky maneuver loomed.
Before approaching Earth’s atmosphere,
the crew would have to separate the LM
from the command module. Ordinarily,
the astronauts would employ the service
module’s so-called reaction control sys-
tem, with its thrusters, to accomplish
this. But the craft’s power failure meant
this was not operable, and the service
module would be gone before the LM
anyway. University of Toronto engineers,
led by Bernard Etkin and called on byLEFT: Following the successful splashdown of
Apollo 13, NASA flight directors celebrate in Mission
Control. They are, left to right: Gerry Griffin, Gene
Kranz, and Glynn Lunney.RIGHT: This image provides a sea level view of the
recovery of Apollo 13 in the South Pacific. Fred
Haise steps onto the life raft as Jim Lovell leaves the
spacecraft in the background. Jack Swigert is
already in the raft. The crew were picked up by
helicopter and carried to the waiting USS Iwo Jima.