Apollo 13 Propulsion Activity
Jerry Woodfill - Apollo13 Warning System Engineer
Testimony: After the explosion, there was concern over
which engine should be used to speed the trip back to Earth, the lander’s small descent engine at
the lower left (the DPS or Descent Propulsion System) or the command ship’s much more powerful service module
propulsion system (SPS) at the
right. The larger SPS was designed to put Apollo 13 in lunar orbit and
rocket Apollo 13 back to Earth. The
activity below deals with this facet of the rescue.
1.
Print the picture below and have the children color
their copy. Let them see a color
picture of Apollo 13 with the NASA logo and American flag to copy.
2.
Have the children cut out their picture.
3.
Paste the picture of Apollo 13 length-wise on a lunch
sack. After threading the string through a straw as pictured below, tape the straw length-wise along the
top of the lunch sack as pictured below and parallel to
their picture of Apollo 13
4.
Place a balloon in the lunch
sack. Have one child paste his picture with the lunar
lander’s engine pointed toward the open end.
Have another child point the service module’s engine toward the sack’s open
end. One represents the SPS, the other the DPS.
Blow the SPS balloon up much more than the DPS balloon corresponding to
the much larger thrust of the SPS than the DPS.
5.
Assign four children to holding
the four ends of two 10 foot long
strings. Assign each child as a moon
holder or Earth holder. Explain that the
10 feet represents 240,000 miles between the Earth and the Moon.
6.
After blowing up each
balloon, use a paper clip holder (or clothes pin clip) to keep air from escaping from the balloon as pictured below.
7.
The string's direction and position controls the trajectory and linear orbit of the Apollo 13 craft between the make believe Earth and Moon. (Round pieces of cardboard with photo-copies of the Earth and Moon pasted on them could be used to anchor the ends of the string by threading the string through a center hole in both the Earth and Moon cardboards. Have students hold the ends of the string which was threaded through the Earth and the Moon.)
8.
To “blast off” quickly release
the clip on the SPS sack first. Watch
the speed and distance the Apollo 13 lunch sack ship goes. Do the
same with the Apollo 13 sack propelled by the lunar lander’s engine. Compare the speeds.
9.
Repeat the process after
blowing up the SPS balloon especially hard.
Explain that this would be to speed the journey back to Earth before the
crew ran out of oxygen, water, and electrical power. Attached the clip to the balloon nozzel. Have the clip jaws closed with your fingers
on the release metal tabs. Conceal in
your other hand a pin. Have the children
count down from ten to similate NASA’ countdown clock. At the count of zero, prick the balloon with
the pin so that it explodes. Explain to
the children that this might have been the case because the SPS might have been
damaged by the oxygen tank explosion.
The wiser and safer decision was to use the lander’s engine. This made the trip back to Earth slower but safer.
Materials:
drinking straw, string (kite string), balloon (long rather than round), tape, 2 chairs (or students), paper lunch sack, scissor, paper
holder clip, crayons
