32 ASTRONOMY • APRIL 2020
shut down and temporarily abandon the
command module, saving it for an Earth
reentry. They also opted to crank up
power inside the LM, move themselves
there, and employ that portion of the
craft, in their words, as “a lifeboat.”
The situation was dire. The energy,
electrical power, and oxygen and water
were all extremely limited. Turning the
LM into a lifeboat made a return trip to
Earth possible; without the LM, none of
the astronauts would have survived.
Finding a way home
Once the grim nature of the situation
became apparent, Kranz directed per-
sonnel at Mission Control to abort the
mission. This could be done in a variety
of ways, as mission planners had cre-
ated scenarios for anticipated in-f light
problems. The most obvious alterna-
tive was the so-called Direct Abort
Trajectory, which would require firing
the service module’s engines in order
to spin up the spacecraft’s trajectory
and change its velocity by more than
6,000 feet (1,830 meters) per second.
When the analysis occurred, some
60 hours into the f light, it would be
possible to set the craft on a safe return
flight toward home. However, it would
be possible at this stage only if the LM
were jettisoned, and this was out of
the question because it now served as
the life-support system for the crew.
So Kranz quickly ruled out the most
straightforward, anticipated emergency
return option.
Kranz and the support crew on the
ground also considered whether the
service module engine’s fuel could beburned off, which could be followed by
jettisoning the service module, and then
using the LM engines designed for a
lunar descent to power the craft home-
ward. But f light controllers worried
about ridding the spacecraft of the ser-
vice module, which would supply valu-
able heat-shield protection during the
Earth reentry. Kranz and his colleagues
were also worried about the structuralThere are two ways to view the images
printed in 3D. To free view the images with no
mechanical assistance, let your eyes relax as
you view the photos as though focusing on a
point behind them. At first you will see the two
images split into four; as your eyes focus at the
correct distance, the middle two images will
combine to create a single, crisp 3D image.
The outer two images will remain on either
side of the 3D image and become blurry.
Alternatively, you can use a 3D viewer, such
as the Lite OWL viewer designed by Brian May
and included with the Mission Moon 3-D book,
to view images in 3D. Only 5 by 2.5 inches (134
by 64 millimeters) and 0.1 inch (3 mm) thick, the
Lite OWL viewer is designed for easily viewing
3D images in books, magazines, modern and
vintage stereocards, and even video or other VR
content on your smartphone. You can purchase individual
Lite OWL viewers separately at http://www.MyScienceShop.comHOW TO VIEW OUR 3D IMAGES
On April 17, 1970, a few hours prior to the splashdown in the South Pacific, Apollo 13 astronauts shot a short sequence of images of the jettisoned service
module from the command module, Odyssey. We used two consecutive frames from this series to construct a stereo view, showing the damage from the
oxygen tank’s explosion.