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You are a NASA Space Suit Engineer and you need to select the best material to be used on your space suit.
- Materials per Group
- 1 empty tissue box
- 1 pair of scissors
- 1 roll of cellophane tape
- 10 napkins
- 10 paper towels
- 1 small marble
- 1 large marble
- 1 meter stick
To investigate the relationship between mass, speed, velocity, and kinetic energy. To apply an engineering design test procedure to determine impact strength of various materials.
National Science Content Standards:
o Motion and Forces
Science and Technology
o Abilities of Technological Design
Science in Personal and Social Perspectives
o Personal Health
National Mathematics Content Standards:
o Apply appropriate techniques, tools, and formulas
o Develop and evaluate inferences and predictions based on data
Vocabulary: Debris, Force, Kinetic Energy, Mass, Speed, Velocity
The International Space Station (ISS) orbits about 400 kilometers (250 miles) above the surface of the earth. The ISS is surrounded by human-made debris (trash) which can impact (hit) the ISS or the astronauts in space suits outside of the ISS at speeds up to about 7 kilometers per second (16000 miles per hour). Debris traveling at high speeds can cause life threatening damage to the ISS the space suits. Data collected by the International Space Station helps to track these objects.
This activity can be conducted in a classroom environment. Ideally, have three (3) students per team.
Other materials like tissues, aluminum foil, etc. may be used in the place of the napkins and paper towels. Marbles can be replaced with other objects if desired. A student handout with answer key is provided.
Additional Information for Teachers
Types of Orbital Debris
1. Natural Debris. This comes from asteroids and comets that pass near Earth. It is usually smaller and harder to observe than human-made debris.
2. Orbital Debris. This means all human-made space objects that aren‘t being used. These are caused by pieces from rockets and satellites.
Both types of debris are called Micrometeoroid and Orbital Debris (MMOD).
How much orbital debris is in Earth orbit?
In Earth orbit there are about 19,000 objects bigger than 10 cm, about 500,000 objects between 1 and 10 cm, and millions of objects smaller than 1 cm.
How is the International Space Station protected from orbital debris?
The ISS is the most heavily shielded space craft ever flown. Important areas like the modules (sections) where the astronauts live can survive hits from orbital debris less than 1 cm in diameter. The ISS can also move to avoid larger objects.
How are astronauts protected when they need to go outside of the ISS?
Astronauts sometimes need to go outside of the ISS to do repairs and inspections. These are called Extravehicular Activities (EVAs). The astronauts use a space suit to protect them, called the EVA Mobility Unit (EMU).
Space Suit Layers
This activity focuses on the engineering design and testing process used to select the best materials to protect the astronauts while they are in their space suits. The space suit is protected by multiple layers of materials with each layer serving a different function. The layers of the suit from inside to outside are:
1. Pressure garment bladder. This is a urethane coated nylon oxford material (kind of like a rubber balloon) which keeps all the breathing air inside the space suit.
2. Pressure garment restraint layer.
This layer is made of Dacron (a material commonly found in tents). This gives the pressure garment bladder a human shape and holds it close to the body of the astronaut.
The next layers of the suit are called the Thermal Micrometeoroid Garment (TMG).
3. TMG Liner. The inside layer is made of Neoprene (a material found in wetsuits). It protects astronauts from the temperature extremes in space.
4. TMG Insulation. This is made of about 6 layers of aluminized Mylar (a material commonly found in metallic balloons), and insulates the astronauts to keep them at the tight temperature.
5. TMG cover. The outside layer is made of Nomex, Kevlar, and Teflon. These are the same kinds of materials used in a bulletproof vest, even though the space suit is not bulletproof. It protects against micrometeoroid impacts in space. It is also white because white tends to reflect more heat energy than it absorbs which prevents the space suit from getting too hot. The TMG cover layer is the focus of this engineering activity.
How does NASA test space suit materials?
NASA has a Hypervelocity Impact Testing Facility (HITF) located at White Sands Test Facility in New Mexico. The HITF is home of a light gas gun.
NASA has to use a light gas gun in order to accelerate small objects to speeds of up to 7 kilometers per second (16,000 miles per hour) into a space suit material sample.
A failure is defined as an impact that completely penetrates the pressure garment bladder, damages the inner liner of the pressure garment bladder, or causes the bladder to leak air or oxygen.
1. Velocity is defined as the speed and direction an object travels. Kinetic Energy is defined as the energy due to the motion of an object. Kinetic Energy is defined as the one half of the mass of an object multiplied by the square of the velocity of an object.
Kinetic Energy = ½ x mass x velocity2
If marble A is traveling at the same velocity as marble B, and marble B has more mass, which marble has the larger kinetic energy?
Answer: Marble B will have the larger Kinetic Energy.
1. Speed is defined as the distance an object travels over a certain period of time. As an engineer, how would you calculate the speed the marbles are traveling when they impact (hit) the space suit material sample?
Answer: Speed is calculated by measuring the distance the marble travels and dividing it by the time it takes the marble to impact the suit material sample.
2. When the same-sized marble was dropped from a different height, did it hit the suit material sample with the same speed? Why or why not?
Answer: No. Since the marble is constantly accelerating, the further the marble fell, the faster it was going when it hit the test material sample.
3. A force is defined as the push or pull on an object. What two forces are pushing and pulling on the marble as it falls toward the space suit material sample?
Answer: When the marbles are falling on Earth, they are falling through the atmosphere. An object that is falling through the atmosphere has two external forces acting on it. The first is the gravitational force (weight) and the second is the force due to drag (air resistance) acting on the marble as it falls toward the space suit material sample.
4. Air resistance increases with speed. When different sized marbles are dropped from the same height, will they hit the suit material sample with the same speed? Explain your answer using your answer from Question 3.
If you were to compare two objects, the higher velocity occurs for the object of lower frontal area. For this activity the marbles would have drag forces very close to each other due to their similar frontal areas, which lead to similar drag forces.
If the two marbles were falling in a vacuum (no atmosphere), the only external force acting on them is the force of gravity. Without air resistance, objects fall toward the Earth with the same constant acceleration caused by Earth’s gravity. Such objects are said to be free falling. The weight, size, and shape of an object are not a factor during free fall, so both marbles would fall at the same speed and hit the box at the same time.
During the Apollo 15 mission to the Moon, NASA astronauts proved this by dropping a hammer and a feather at the same time, and they both landed at the same time. On Earth the drag forces would have made the feather hit later, but the Moon has no atmosphere, so gravity was the only force.
If the marbles were dropped from a much greater height, according to Newton’s first and second laws of motion, an object will accelerate if the forces acting on it are unbalanced. The amount of acceleration is proportional to the amount of net force acting upon it.
Falling objects initially gain speed because there is no force big enough to balance the downward force of gravity. As an object gains speed, the air resistance (drag force) increases. A marble that weighs more will have a greater downward force of gravity. The heavier marble will have to accelerate for a longer period of time before there is enough upward air resistance to balance the larger force of gravity (weight).
When the upward air resistance equals the downward force of gravity, the object will have reached its terminal velocity. Terminal velocity is the final velocity of the object.
The heavier marble requires a larger air resistance to reach terminal velocity so it would have to accelerate for a longer period of time.
5. What suit material survived the largest number of impacts? Explain you answer based on your test results.
Answer: The paper towel should have survived the largest number of impacts. The layered napkins should have performed better than at least the single napkin.
6. Compare the damage done by the two different marbles. What did you observe?
Answer: The larger marble should have done more damage than the small marble.