Egg Drop
What It's All About
Pathfinder had to change its speed gradually when it landed to avoid shocks that could have damaged its delicate instruments. If the spacecraft changed speed too abruptly, as in a crash landing, the force would have damaged or destroyed it. The spacecraft used several methods to slow itself down for landing. The last step in the slow-down sequence used airbags to reduce the abrupt
change of speed on impact with the ground. When the lander hit the ground, the air in the bags absorbed the force of impact by compressing. It did this in less than a tenth of a second. That seems like a short time, but it was long enough to "break the fall" and reduce the force of impact. The compressed air bounced back and made the lander bounce as well, but the bounces got smaller until the lander came to a stop.
What You Need
- Cardboard cut to an equilateral triangle about 30 centimeters (12 inches) on each side
- Marshmallows, cotton balls, bubble wrap, balloons, and other cushioning materials
- Raw egg—in its shell
- Tape and glue
What to Do
1. Score and fold each corner of the triangle to the center of the side across from it. The result will be a tetrahedron: four equal triangles connected together. It will look like the basic shape of Pathfinder, with one triangle flat on the table and three triangles folded upward like flower petals.
2. Unfold the tetrahedron and turn it over.
3. Glue or tape your cushioning material to all four outer sides.
4. Turn the tetrahedron right side up again and tape the egg inside.
5. Tape the "spacecraft" closed.
6. Drop your spacecraft from a reasonable height. Try standing on a chair or table, for example.
7. Retrieve the spacecraft and open it carefully.
8. If your egg was broken, add some more or a different type of cushioning and try again. If it was not, experiment with greater heights and see what happens.
What Happened?
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Why?
The cushioning materials act like Pathfinder's airbags, "breaking the fall" into a series of bounces instead of one big, sudden stop. By slowing the change of speed in the actual collision, it reduces the force your spacecraft "feels" when it hits the ground.
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