Appleton, Victor – Tom Swift Jr 03 – And His Rocket Ship

“How does this invention differ from the ordinary aneroid altimeter that we use now?” Hank Sterling asked.

“An altimeter which depends on measuring atmospheric pressure won’t work at very low air pressures,” Tom replied. “This instrument picks up the noisy cosmic rays from the sun. The nearer the sun, the noisier the waves.”

“How accurate is it?” Hanson asked.

108 TOM SWIFT AND HIS ROCKET SHIP

“Within a few feet,” Tom replied. “Frankly, this part of the instrument is not my own brain child. The idea has been kicking around for some time.”

“You dreamed up the navigation part of it?” Bud asked.

“Yes,” Tom answered. “I took the principle of solar radiation and applied it to the stars. This instrument in the black case picks up the waves from three stars and the rocket’s position is recorded on the dial-instantly.”

“Let’s see it work,” Hank Sterling urged.

Tom flicked the toggle switch. A whirring sound began and the needle on the dial moved instantly to seventy-eight thousand feet. Another switch was snapped and five dots appeared on the upper dial.

“The black one at the bottom is the earth,” Tom explained. “The three red ones are stars.”

“The small one must be the fix-the position,” Hanson said.

“That’s it,” Tom replied. “The point of intersection of the lines from the three stars.”

“How do you know which stars are showing on your screen?”

“Each first-magnitude star sends its own distinct sound,” Tom explained.

“Listen.”

Three slightly different beeps were coming from the instrument. From a chart Tom identified them as Deneb, Vega, and Altair.