AstroCappella: Wolf 359
Land Safely...
An activity by Kara C. Granger
Activity Summary:
During this activity, students will model the preparation needed for a soft-landing on a planet or object in space. They will do this by packaging a raw egg with certain material, and dropping the egg from a given height to test the packaging effectiveness.
Objective:
Students will apply simple physics and mathematics to determine the effectiveness of packaging an object for a soft-landing.
Materials for each group of 12 students:
- 8 index cards
- 8 raw eggs with no cracks
- 8 tape measures
- watch or timer with sub-second timing
- box of tissues
- cardboard
- tape
- string
- bubble wrap
- plastic
- any other piece of material that one group of students can choose
from to package their egg
Introduction
When launching delicate instruments to soft-land on the moon or other planets, a particular problem exists in packaging these instruments to protect them from vibration, acceleration and deceleration during launch, re-entry, and landing. This same consideration should be given if you are contemplating a trip to Wolf 359. How would you package your cargo in order to have a successful landing?
Activity
In order to prepare for such an event, we must understand the physics behind landing a payload. Simply put, we can create an experiment with raw eggs (where one raw egg represents a human, an animal, or a delicate optical or electronic cargo). Students will be asked to package these eggs to withstand a fall from about 5 meters.
Before dropping the egg, or even before the students actually package their cargo, the teacher should discuss the variables which can be controlled, which can be measured, and which can be calculated. One should discuss which factors have the greatest influence upon the forces of impact and which do not. For example, you may want to ask;
1. Does the mass of the package have any effect?
2. What about the dimensions and shape?
3. What about the falling distance/time?
Procedure
On each of the 8 index cards, place a different packaging assignment (see below). Place students into 8 groups, giving them their assignment from the Chief Scientist of the Egg Drop experiment, which is on an index card.
PACKAGING ASSIGNMENT
| A | B | C | D |
|---|---|---|---|
| Major budget cuts have occurred to your experiment. Your group can only rely on luck to save the egg in the soft-landing. | Some budget cuts have occurred to your experiment. Your group can only rely on tissue and tape to package your eg for the soft-landing. | Minor budget cuts have occurred to your experiment. Your group can only rely on tissue, cardboard, and tape to package your egg for the soft-landing. | You are in luck! Your group has been awarded a large budget. You may use any available material to package your egg for the soft-landing. |
The use of external devices to increase atmospheric drag such as parachutes, balloons and other air-drag devices should not be used due to the possibility of landing a payload on planets with little or no atmospheres.
1. Package your egg according to your assignment from the Chief Scientist of the Egg Drop experiment, which is on an index card.
2. Follow your teacher to the experimental soft-landing site, which has to be a place where you can drop your packaged egg from about 5 meters.
3. Prepare to time the length of the fall, then drop your egg from approximately 5 meters.
4. Examine the contents of the package to determine the various levels of success:
| shell intact, yolk intact... | complete success |
| shell intact, yolk broken... | brain damage! |
| shell broken, yolk intact... | paraplegic! |
| shell broken, yolk broken... | thank goodness it was only an egg! |
5. Make the appropriate measurements and calculations of the gravitational or `g' forces of impact.
Input:
-
DF = Distance of Fall
TF = Time for Fall
CD = Crush Distance
-
AV = Average Velocity
TV = Terminal Velocity
TC = Time to crush
D = Deceleration
G = g forces
AV = DF/TF
TV = 2 * AV
TC = 2 * CD/TV
D = TV/TC
-
G = D/32 feet per second per second
or G = D/9.8 meters per second per second
1. Record each group's calculations in an organized fashion, and where others can observe the results (such as an overhead or chalkboard). Ask students to discuss some commonalities among the data. Ask them if they notice a difference in one variable that protected cargo in any one group.
2. Ask the students to discuss how well this experiment modeled a real-life soft landing of cargo.
3. Discuss with students how they might change the packaging of their egg to ensure a successful soft-landing for every trial and group.