PERSONAL JETPACKS

Personal jetpacks have become a reality in space. On Earth, a successful jetpack has proved harder to achieve, although the devices have featured in lots of sci­ence fiction stories. In stories set in the future, a character straps a jetpack on his back, fires up the engine, and takes off.

A few personal jetpacks have been built and used in real life. The 1984 Summer Olympic Games in Los Angeles,

California, began with a pilot wearing a real jetpack flying into the stadium.

Most of the personal jetpacks devel­oped so far, however, are not powered by jet engines. Their jet thrust is supplied by a small, powerful rocket. These devices also are known as rocket belts, or rocket packs. When the wearer wants to take off, a liquid called hydrogen peroxide is forced from tanks in the backpack into a reaction chamber. Hydrogen peroxide is similar to water, but it contains extra

oxygen. Inside the reaction chamber, a chemical reaction changes the hydrogen per­oxide into steam at a temperature of 1370°F (743°C). The steam jets out of two pipes that point downward, pushing the flier up off the ground. The jetpack is steered by means of tilting the jet pipes.

Even the most advanced model built so far can be flown for no more than about 30 seconds. Jetpacks powered by jet engines can make longer flights, but they are far more complicated to build and much more expensive.

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The astronauts also are anchored to the spacecraft by their boots or with a line.