Meteoroids and space debris present a potential hazard to astronauts and spacecraft. This activity demonstrates the penetrating power of a projectile with little mass but with high velocity.
|Step 1. Hold a raw potato in one hand. While grasping the
straw with the other hand, stab the potato with a quick, sharp motion. The straw
should penetrate completely through the potato. Caution: Be careful
not to strike your hand.
||Step 2. Again hold the potato and this time
stab it with the straw using a slow push. The straw should bend before penetrating
the potato very deeply.
Astronauts on spacewalks are likely to encounter fast-moving rocky particles called meteoroids. A meteoroid can be very large with a mass of several thousand metric tons, or it can be very small--a micrometeoroid about the size of a grain of sand. Every day Earth's atmosphere is struck by hundreds of thousands or even millions of meteoroids, but most never reach the surface because they are vaporized by the intense heat generated when they rub against the atmosphere. It is rare for a meteoroid to be large enough to survive the descent through the atmosphere and reach solid Earth. If it does, it is called a meteorite.
In space there is no blanket of atmosphere to protect spacecraft from the full force of meteoroids. It was once believed that meteoroids traveling at velocities averaging 80 kilometers per second would prove a great hazard to spacecraft. However, scientific satellites with meteoroid detection devices proved that the hazard was minimal. It was learned that the majority of meteoroids are too small to penetrate the hull of spacecraft. Their impacts primarily cause pitting and sandblasting of the covering surface.
Of greater concern to spacecraft engineers is a relatively recent problem--spacecraft debris. Thousands of space launches have deposited many fragments of launch vehicles, paint chips, and other "space trash" in orbit. Most particles are small, but traveling at speeds of nearly 30,000 kilometers per hour, they could be a significant hazard to spacecraft and to astronauts outside spacecraft on extravehicular activities.
Engineers have protected spacecraft from micrometeoroids and space trash in a number of ways, including construction of double-walled shields. The outer wall, constructed of foil and hydrocarbon materials, disintegrates the striking object into harmless gas that disperses on the second wall. Spacesuits provide impact protection through various fabric-layer combinations and strategically placed rigid materials.
Although effective for particles of small mass, these protective strategies do little if the particle is large. It is especially important for spacewalking astronauts to-be careful when they repair satellites or do assembly jobs in orbit. A lost bolt or nut could damage a future space mission through an accidental collision.
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