This material was developed for the Live From Mars project
by Passport to Knowledge. Live
From Mars was a precursor to Mars Team Online.
Activity 3.1: The Incredible Light Bulb-Egg Drop Challenge
Teacher Background: The Incredible Bouncing Spacecraft
| Pathfinder will enter the upper atmosphere
of Mars at 7.6 kilometers per second at a 14.2 degree angle (90 degrees
would be straight down). It will meet its peak atmospheric shock,
encountering forces 25 times Earth's gravity, at 32 kilometers above
the surface. At 10 kilometers above the ground, a parachute will deploy
at nearly twice the speed of sound (400 meters per second). Rockets
inside the backshell will fire to further slow the lander's descent.
Shortly before landing, a set of airbags will inflate to cushion the
impact. After a few seconds, the tether attaching the lander to the
backshell and parachute will be severed, and, with 90 percent of the
fuel expended, the rockets will carry the shell and other debris away
from the landing area. Then, protected (hopefully) by its airbags,
Pathfinder will bounce on the Martian surface, perhaps as high as
a ten-story building, before finally coming to rest after its 8-month
Students will demonstrate an understanding of the challenges of
soft landing a spacecraft on Mars by designing, building and testing
their own "interplanetary lander."
| Materials: For each team of students
||Materials: For the whole class
a square yard of
tightly woven nylon
a paper lunch bag
a plastic shopping bag
2 - 3 balloons
two paper clips
five feet of string
three 8 1/2 x 11 inch
sheets of paper
a raw egg (now you
know it's going to
be fun!) or a light bulb
a sensitive scale (e.g. postal scale)
NOTE: In advance of class decide whether your school's policies
(and your own prudence) permit you to use light-bulbs, or whether
you will choose to use an egg, or other "fragile payload". Exercise
caution. Discourage students from leaning off ladders or out of
windows! We suggest enlisting help in the final "Drop Test."
From top of a ladder or table, drop a box of paper clips to the floor.
It's noisy and messy, but nothing's broken. Ask students to think of ways
they might safely land a fragile spacecraft on another planet. Tell them
that in this Activity, they are going to play the role of NASA engineers,
and are going to design, build and test their own interplanetary landers.
In the above discussions, students may suggest the use of retro-rockets
as in the Apollo moon landings or as seen in many science fiction films.
Explain to students that while retro-rockets do work, they add significant
size and weight to a spacecraft and, if their thrust is applied too close
to a planet's surface, they can seriously disturb or contaminate the things
scientists wish to study. Thus, in this Activity, they will be challenged
to come up with small, light-weight alternatives that don't use retro-rockets
for safely landing a very fragile payload on the surface of Mars.
Divide the class into Engineering Teams and distribute a set of
the above materials to each of the teams. Tell them they have exactly
one class period to design and build a lander out of some or all
of the materials they have received. The fragile payload they will
be challenged to land safely is the egg or light bulb which, when
placed in their "descent module", must survive a fall of three stories
without breaking. At the end of the class period, their landers
will be put away and retrieved on the first fair weather day available
for testing. Tell students that each team is in competition with
the others for an all important NASA contract and that the team
which builds the lightest lander that successfully lands an unbroken
egg or light bulb will be the winner.
When the big day arrives, record the weight of each lander and
then, amid appropriate pomp and ceremony, have a colleague or parent
volunteer drop each entry, one by one, out of a third story window,
or off the school's roof.
An exciting alternative is to invite your local fire department
to take part using one of their big hook and ladder trucks. Invite
the local news media to cover the
event. Video tape the contest and send us a copy
here at PTK !
Give the student teams the additional challenge of keeping the
overall size of their lander to a certain volume, e.g., no more
than 12 inches cubed. You may also wish to use this Activity as
a take home assignment and possibly allow students to get advice
from parents. This may prove an unfair advantage, however, to students
with engineers in the family.
In this Activity, students tested their creations on home ground.
As a follow up, challenge them to research relevant similarities
and differences between Earth, the Moon and Mars and draw conclusions
as to how these might affect the design of their lander. The Moon
has no atmosphere. Parachutes would be useless in slowing down landers
on the Moon. Mars does have an atmosphere, but it's very thin. Therefore,
a descent device that relied solely on a parachute to slow it down
would not work nearly as well on Mars as on Earth, unless it were
much bigger. This, in turn, adds weight and volume to the spacecraft.
Mars has only about one third of Earth's gravity. Therefore, objects
fall more slowly on Mars. Dropping something from a relatively low
height on Earth would cause the object to have the same speed on
Students studying physics will have ample opportunities to take
this Activity further. They can, for example, study a lander's changing
potential and kinetic energies as it falls. They can also study
the rate of fall of the lander and compare final velocities, with
and without parachutes, while learning about drag. Also noting that
the force of gravity on Mars is only 38% of that on Earth, they
can calculate how high a drop on Mars would result in the same velocity
upon impact as a drop from a three story building on earth.
Write a news report for July 4, 1997, the day Pathfinder is scheduled
to land on Mars.
Research the descent and landing sequence (link to JPL's Pathfinder
page from the LFM site) and what scientific data it will be collecting
as it descends through the Martian atmosphere. Do the same for the
Sojourner rover as it leaves the lander and begins to traverse the
Martian landscape. How is it powered, how long will it function,
what data will it be sending back to Earth?
Research MARS '96, the Russian mission slated to take off in mid-November
1996, but to arrive at Mars after Pathfinder. Report to the class
on similarities and differences between the Russian and American
missions in terms of the rocket being used and the design of the
lander. See if any Russian or German schools are on-line (the German
space agency and German researchers are involved in both missions
and German scientists contributed the ÒAÓ and ÒPÓ in Sojourner's
APXS). Begin sharing updates on what your class is doing via the
(Special thanks to PTK Advocate Fran O'Rourke-Hartman, of Cedar Wood
Elementary School, Everett, Washington, whose students prototyped this
Activity last year.)