Many years before Apollo astronauts walked on the surface of the Moon,
some scientists speculated that lunar dust might pose a significant hazard.
Dust accumulations in old craters could be quite deep and swallow up an
unsuspecting astronaut that tried to cross one. Lunar Surveyor spacecraft
that landed on the Moon prior to the Apollo expeditions showed that lunar
dust (called regolith or sediment) had only accumulated to the depth of
a few centimeters and therefore could not swallow up astronauts. This
did not mean that the sediment was completely safe. Rather, the fineness
of the sediment could pose a different kind of hazard-fouling equipment
and suit components. Viking landers on Mars in the middle 1970s and the
recent Pathfinder/Sojourner mission showed that Mars also has a sediment
coating that could foul equipment and suit components of future Martian
Today, it is possible to study the effects of lunar sediment on materials
because the Apollo astronauts returned home with samples. Rather than
consume valuable lunar sediment samples on materials tests, analysis of
the sediments permitted scientists to create simulated lunar sediments
to use in experiments. Based on Viking studies of Mars and the discovery
of Martian meteorites in Antarctica, scientists have also created simulated
Martian sediments. Both simulants have been used in a variety of tests,
such as fabric abrasion and penetration of bearing seals. Since astronaut
stays on the Moon were limited to a day or two, Apollo spacesuit materials
only had to survive 10 to 20 hours of use. Future Martian explorers, however,
will remain on the planet for many months to a year or more, and their
suits will need to be constructed of rugged materials.
This apparatus will measure the abrasion of fabrics and other suit
materials exposed to simulated Martian sediment.
Test samples are placed in a rock tumbler or a specially constructed
tumbler similar to the one shown on the proceeding page. Simulated Martian
sediment is placed in the drum and the rotating motion causes the sediment
to abrade the samples.
Materials and Tools Checklist
- Wooden base (12" x 24" x 1")
- Electric motor with pulley
- (use motor with low rpms)
- Pulley belt
- Plastic food jar (1 gallon)
- Four casters
- Wood block stops
- Fabric samples
- Masking tape
- Martian sediment simulant
The device shown on the previous page is a home made rock tumbler. It
is constructed from a plastic jar of the kind supplied to cafeterias and
restaurants with various food stuffs such as relishes or mayonnaise. A motor,
pulley, and rubber band belt rotate the jar. The jar rests on inverted casters
and is held in place with stops at the ends. Squares of fabric samples are
taped to the inside walls of the jar and a measured quantity of Martian
sediment simulant is placed in the jar. The jar is allowed to rotate for
a day or two and the fabric samples are removed for comparison with fresh
samples. Reddish-brown volcanic rock used for landscaping can be used for
making Martian sediment simulant. Bags of the rock will have small amounts
of abraded sediment at their bottoms or you can crush the rocks to a fine
soil-like material. Be sure to wear eye protection and gloves. Use a hammer
to smash the rocks. Sort out and discard the larger pieces to leave just
the sandy to powdery material behind.
Look for an electric motor at an electric parts store.
It may also be possible to find a suitable motor in an old appliance.
Casters can be obtained at a hardware store.
Examine fabric samples for signs of wear such as tears and holes.
If a sample is opaque, place it on the lighted stage of an overhead
projector to look for holes and thin areas.
If solid materials are to be tested, do not test fabrics at
the same time. The solid materials may damage the fabric, making it
difficult to interpret the results.
Estimate the number of rotations of the "rock tumbler" jar by
counting how many times the jar rotates in one minute. Multiply the
number of minutes the jar has been rotated by the number of rotations
More student interaction with the activity can take place if
the motor-driven apparatus is replaced with just a jar. Each day for
a week or two, students spend a few minutes shaking and rotating the
jar and counting the number of times.
Devise testing procedures to measure the abrasion of
the fabric on fabric in places on the spacesuit where fabric rubs against
itself (underarms, crotch, etc.).
Fabric abrasion tester in use at the NASA Johnson Space Center.
The white drum contains an inflated cylinder made from the outer
fabric of a spacesuit. The drum also contains lunar sediment simulant.
An electric motor with a pulley drives the drum.
Apollo 16 astronaut Charles M. Duke Jr. samples lunar regolith
(sediment) next to the "house rock" in the lunar Descartes highlands.
Very fine sediment clings to his suit
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