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MARS Dead or Alive
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Classroom Activity
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Objective
To investigate three variables affecting a parachute's rate of descent and then design a parachute that will descend as slowly as possible.
- copy of the "Slowing Things Down" student handout
(PDF or
HTML)
- copy of the "Engineering Team Directives" student handout
(PDF or
HTML)
- copy of the "Testing Your Parachute" student handout
(PDF or
HTML)
- 113-L (30-gallon) large plastic trash bag (0.9-1.1 mL thick)
- three 2.6-cm metal washers
- kite twine—Variable A teams: 12 m; B teams: 15 m; C teams: 10 m
- 25-cm compass—Variable A teams only
- tissue paper—Variable B teams only
- plastic grocery bag—Variable B teams only
- meter stick
- scissors
- clear tape
- fine-point marker
- 8-m measuring tape
- stopwatch
- calculator
Discuss with students some uses for parachutes (to slow down human descent, to
drop supplies and other materials into war zones, to slow down vehicles such as
the space shuttle and the rovers). Ask students what variables affect a
parachute's rate of descent (e.g., canopy surface area, canopy material, length
of suspension lines, number of suspension lines, shape, payload weight, vent
diameter, and wind). Write their answers on the board.
Tell students they have been hired to design, construct, and test a
parachute that will bring a payload down to the ground as slowly as possible.
In this activity, students will test three of the variables that affect descent
rate.
Organize students into enough teams so that each variable outlined in the
"Engineering Team Directives" student handout is tested by at least two
teams.
Distribute the materials and student handouts to each team. Have each team
make and record a hypothesis about how its variable will affect the descent
rate of its parachute. Ask students to explain their reasoning.
Emphasize the importance of constructing the parachutes as closely as
possible to the specifications provided. This is important to ensure the
consistency of results among both the parachutes tested within each team and
the parachutes tested among teams.
After students have constructed their parachutes, locate a safe and suitable
place to drop the parachutes, such as from a balcony, theater stage, gym
bleachers, or window. Make sure the drop height is at least 4-5 meters and that
there are as few drafts as possible. Emphasize to students the importance of
conducting each trial the same way—dropping the parachute in a consistent
manner and accurately timing the drop is critical to this activity.
Have each team report its results. Create a data table on the board for each
variable listing the average descent rates. What contributed to slower descent
rates for each variable tested? Once students have shared their findings,
present students with another challenge: Based on the results of previous
trials, design and construct a parachute that will have the slowest average
rate of descent while carrying a 2.6-cm metal washer payload. You may want to
give students the option of changing untested variables, such as number of
suspension lines or canopy shape. Provide students with any additional
materials they may need.
Have each team drop its parachute five times and determine the average rate
of descent for the five trials. Once all teams have finished, compare the
parachute with the slowest descent rate to the others. What about it might have
contributed to its longest descent time? To conclude, discuss with students
whether the slowest parachute would be the best parachute. What other
considerations might affect parachute design?
As an extension, have students research different kinds of parachutes and
their uses.
A
parachute helps reduce the speed of a falling object by providing air
resistance, or drag. The upward force of the air on the parachute opposes the
downward force of gravity on the payload. In addition, drag is produced when
air moves through the small holes in porous canopy material, across the surface
of the chute, or along the suspension lines. Parachutes that create more drag
have a slower descent rate, while parachutes that create less drag have a
faster descent rate.
A parachute with the slowest descent rate might not necessarily be the best
parachute for any given task. Engineers also need to consider other aspects of
parachute design, such as stability, weight, and materials cost.
Students tested the following:
Canopy Size: In general, parachutes with a larger surface area produce
more drag, and therefore descend more slowly. There is a point where a larger
canopy size yields no more added benefit.
Canopy Material: In general, lighter and/or less porous materials create
more drag than heavier and/or more porous materials.
Suspension Line Length: Longer suspension lines allow the canopy to
inflate fully and thus create more drag, slower descent rates, and more
stability. They also add more weight. Shorter suspension lines create less
drag, faster descent rates, and less stability. However, suspension lines that
are too long may become tangled, while suspension lines that are too short may
prevent the parachute canopy from fully inflating.
There are myriad additional variables that contribute to parachute descent
rate, including number of suspension lines, payload weight, number and size of
vent holes, number of canopy layers, and canopy shape. How these are combined,
and the ratios of the materials used, all contribute to how slowly a parachute
descends.
In addition to these and other design factors, parachutes are affected by
outside forces such as wind and atmospheric pressure. Because the atmospheric
density of Mars is less than 1 percent of Earth's, a parachute alone cannot
slow down the Mars Exploration Rover enough to ensure a safe, slow landing
speed. Therefore, the MER parachute system includes rockets to help slow the
descent of the lander and to help counteract the effect of strong Martian
winds.
To help the rover land safely, the NASA team designed several systems,
including an aeroshell to protect the lander carrying the rover from heat and
forces during atmospheric entry, a parachute to slow the lander's speed prior
to impact, and airbags to soften the landing. The Martian lander requires a
parachute system that will slow the lander enough to prevent it from crashing
into the surface, and stable enough to prevent the lander from striking the
surface at an angle.
Sample Results
Variable A: Surface Area
Parachute 1: 18 cm canopy
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Height (m)
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Time (s)
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Rate (m/s)
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Drop
1
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4.5
m
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2.14
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2.10
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Drop
2
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4.5
m
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2.23
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2.02
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Drop
3
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4.5
m
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2.23
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2.02
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Drop
4
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4.5
m
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2.28
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1.97
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Drop
5
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4.5
m
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2.04
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2.21
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18
cm:
average descent rate: 2.06 m/s
27 cm
average descent rate: 1.25 m/s
36 cm
average descent rate: 1.04 m/s
Variable B: Canopy Material
Parachute 1: trash bag
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Height (m)
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Time
(s)
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Rate
(m/s)
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Drop
1
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4.5
m
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4.09
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1.10
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Drop
2
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4.5
m
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4.20
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1.07
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Drop
3
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4.5
m
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4.48
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1.00
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Drop
4
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4.5
m
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4.56
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.99
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Drop
5
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4.5
m
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4.67
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.96
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trash
bag
average descent rate: 1.02 m/s
grocery bag
average descent rate: .87 m/s
tissue paper
average descent rate: .96 m/s
Variable C: Suspension Line Length
Parachute 1: 15 cm line
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Height (m)
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Time
(s)
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Rate
(m/s)
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Drop
1
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4.5
m
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2.05
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2.20
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Drop
2
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4.5
m
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2.65
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1.70
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Drop
3
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4.5
m
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2.05
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2.20
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Drop
4
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4.5
m
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2.20
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2.05
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Drop
5
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4.5
m
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2.15
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2.09
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15
cm
average descent rate: 2.05 m/s
25 cm
average descent rate: 1.31 m/s
50 cm
average descent rate: .96 m/s
Web Sites
NOVA's Web Site—MARS Dead or Alive
www.pbs.org/nova/mars/
In this companion Web site for the NOVA program, watch the program online,
learn why water is necessary for life, investigate the rover's parts, explore
Mars' landscape, and design your own parachute.
Mars Academy
www.marsacademy.com/
Features an international online collaborative project to find real-life
solutions to problems involved with designing a manned mission to Mars,
including landing site selection, trajectory calculations, rocket design, crew
selection, and life support system plans.
Mars Daily
www.marsdaily.com/
Contains a collection of articles related to Mars exploration.
Mars Exploration Rover Mission
mars.jpl.nasa.gov/mer/
Includes short biographies of the scientists who worked on designing the
rovers and background information about the mission.
Mars Exploration Rovers
athena.cornell.edu/
Provides information about the scientific instruments on board the rovers,
the flight plan, and video simulations of the rovers landing on Mars.
Martian Invasion: Probing Lively Puzzles on the Red Planet
www.sciencenews.org/20031108/bob10.asp
Outlines the objectives of the European Space Agency's and NASA's
near-simultaneous missions to Mars.
NASA Center for Mars Exploration
cmex-www.arc.nasa.gov/CMEX/index.html
Presents hundreds of concept maps of Mars-related information, digital atlases
of the Red Planet, a menu of human and robotic missions to Mars, educator
resources, and more.
NASA Spacelink: Mars
spacelink.nasa.gov/Instructional.Materials/Curriculum.Support /Space.Science/Our.Solar.System/Mars/.index.html
Provides image libraries, resource guides, investigations, and more.
NSTA Web News Analysis: Mars Journeys
www.nsta.org/main/news/stories/nsta_story.php?news_story_ID=48395
Offers a digest of online news articles focusing on Mars journeys.
Slowest Model Parachute Challenge
www.cc.gatech.edu/projects/DITC/designTasks/parachute/index.html
Provides an in-depth investigation for a coffee filter parachute challenge,
complete with video clips from three classrooms that completed the unit.
Books
Boyce, Joseph M.
The Smithsonian Book of Mars.
Washington: Smithsonian Institution Press, 2003.
Provides a firsthand account of the history of the planet's exploration by one
of NASA's Mars program scientists. Includes explanations of Mars's atmosphere,
climate, surface, and interior derived from NASA mission findings.
Croswell, Ken.
Magnificent Mars.
New York: Free Press, 2003.
Discusses what is known about Mars and what is still to be discovered.
Hartmann, William K.
A Traveler's Guide to Mars: The Mysterious Landscapes of the Red Planet.
New York: Workman Publishing Company, 2003.
Discusses the three major eras of Mars's 4.5-billion-year history and compares
the geologic time processes on the Red Planet with those on Earth. Includes
many photographs.
Morton, Oliver.
Mapping Mars: Science, Imagination, and the Birth of a World.
London: Fourth Estate, 2002.
Examines scientists' efforts to map Mars and profiles researchers and science
fiction writers who have contributed to how Mars has been viewed.
Raeburn, Paul.
Mars: Uncovering the Secrets of the Red Planet.
Washington: National Geographic, 1998.
Chronicles the history of human exploration of Mars, describing each Mars
mission and its key players. Includes a pair of 3-D glasses to view a foldout
landscape of Mars.
The "Slowing Things Down" activity aligns with the following National Science
Education Standards.
Grades 5-8
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Science Standard B: Physical Science
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Motions and Forces:
If more than one force acts upon an object along a straight line, then
the forces will reinforce or cancel one another, depending on their direction
and magnitude. Unbalanced forces will cause changes in the speed or direction
of an object's motion.
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Science Standard E:
Science and Technology
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Understandings about science and technology:
Perfectly designed solutions do not exist. All technological solutions
have trade-offs, such as safety, cost, efficiency, and appearance.
Technological designs have constraints.
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Mathematics Standard 13:
Measurement
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Grades 9-12
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Science Standard B: Physical Science
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Motions and Forces:
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Science Standard E:
Science and Technology
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Understandings about science and technology:
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Mathematics Standard 13:
Measurement
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Classroom Activity Author
Margy
Kuntz has written and edited educational materials for 20 years. She has
authored numerous educational supplements, basal text materials, and trade
books in science, math, and computers.
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Mars Dead or Alive: A Hostile Environment
Learn in this Teachers' Domain video segment (5m 17s) about the Mars mission and why scientists are so interested in exploring the red planet.
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