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The Landing Help (page 2)

By — McGraw-Hill Professional
Updated on Sep 16, 2011

An Experiment

The Mars utility vehicle (MUV) reminds you of pictures you saw of the very first Moon rovers in the Apollo missions of the mid-twentieth century. And in fact, the two are quite similar.

“What’s that?” you ask as the first officer unfolds a huge, gossamer-thin, butterfly-like sheet of material.

“A kite,” he says.

“A kite! How will that fly here?”

“It is a windy day, or hadn’t you noticed?”

You get into the MUV with the first officer. Then you feel a tug on your pressure suit and hear a whisper against the side of your helmet. “That’s a little bit of breeze.”

“A 20-meter-per-second breeze,” says the first officer. “Or, in old-fashioned terms, a good 45-mile-an-hour gale. Look over that way.” He points toward the southern rim of the caldera. Then you see plumes of pink dust rushing along from east to west.

“Is this wind enough to fly that kite?” you ask.

“More than enough,” says the first officer. “We’ll get away from the Eagle and then try to communicate with some other explorers that happen to be on the far side of the planet right now. This kite will support an antenna. A long-wire antenna, just like the first radio experimenters used around the year 1900 to see if they could send their signals across the Earth’s Atlantic Ocean.”

“Why can’t we do this experiment from the Eagle ? I feel nervous out here with nothing but a pressure suit for protection.”

“That feeling is normal,” says the first officer. “All astronauts, or nearly all, get the same feeling when they go on their first roves away from a space vehicle. It’s like free diving in the middle of a big lake or in the ocean. That’s not the same thing as paddling around in a swimming tank.”

“But why do we have to be all the way out here in the middle of nowhere just to test a radio?” you ask.

“There would be too much radio noise near the Eagle . Electromagnetic interference. All the Eagle’s computers and instruments generate electromagnetic noise. This is a sensitive little radio. It operates at a very low frequency, just 2 kHz, where the waves travel in contact with the surface of the planet,” says the first officer. “Here. You drive the MUV.”

“Two kilohertz! That’s audible sound!”

“It would be if we connected a speaker to the transmitter output rather than an antenna,” says the first officer.

You drive the MUV along toward the great plumes of pink. It’s like riding in a golf cart, except faster and with a slower but more exaggerated rolling motion. Red Martian rocks and boulders litter the floor of the caldera, stretching away in all directions as far as you can see. After about 20 minutes, the first officer says, “We stop here.”

He unreels the antenna line, a thin aluminum wire, and the delta-wing kite sails upward. “Don’t try this at home,” says the first officer.

“Why not?”

“Static electricity can build up, even on a clear day, and reach dangerous levels. I’ve got a couple of scars to show you exactly what it can do.”

“Can’t the same thing happen here?” you ask.

“Yes,” says the first officer. “But our pressure suits are metal-coated to protect against the solar wind and the ultraviolet. That also will discharge any . . . “

At that moment a spark jumps from the kite line to the first officer’s sleeve and from his ankle to the ground. You can’t hear it because of your protective headgear and because the Martian atmosphere is so thin, but you can imagine the “Pop!” it would make back home on Earth.

“Why must you use such low frequencies?”

“Higher frequencies require an ionosphere, or else artificial satellites, to propagate over the horizon. However, very low frequency (VLF) radio waves do not, at least not on a planet that can conduct electricity to any significant extent,” says the first officer. “Mars, according to our data, should conduct well enough to allow VLF waves to travel all the way around the planet.” He pulls out a sheet of paper from the pocket of his pressure suit and hands it to you. “Please see Fig. 6-6.”

Mars From Venus To Mars An Experiment

Figure 6-6. Low-frequency radio waves might allow over-the-horizon communications between exploration parties on planets that have no ionosphere, such as Mars.

“Interesting,” you say. “Primitive but interesting.”

“This MUV rolls on wheels, and they are more primitive than this antenna.”

“That’s a good point,” you say.

“That’s high enough,” says the first officer. The kite is now a tiny triangle against the sky, almost straight overhead. “Two and a half kilometers up.”

The radio tests are conducted. The radio itself is a small, battery-powered box with an old-fashioned telegraph key. The first officer taps on the key, then listens, then taps some more, then listens some more.

“Well?” you ask.

“Negative,” he says.”

“Is it supposed to work?”

“In theory, yes, if we have enough transmitter power and a long enough antenna.”

“Has anyone ever done this before?” you ask.

“Not successfully,” says the first officer. “Not from such a vast distance.”

“Why can’t you use communications satellites? Why this old-fashioned stuff?”

“We can use satellites once they are up and working. This is only an experiment. If we can ever get this type of communications system to work, explorers to the moons of the outer planets and someday to worlds beyond our Solar System might use it for communication before any satellites are launched.”

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