Later on in this article, I wish to describe an instrument, experiments with which can be made to answer for us the question as to whether or not a motor is needed; but just here further quotations should be given to show the trend of the best thought.
Aeronautics (N.Y.) for January contains Professor Langley’s remarkable paper entitled “The Internal Work of the Wind.” The closing paragraph is as follows:
“The final application of these principles to the art of aerodromics seems, then, to be, that while it is not likely that the perfected aerodrome (air-runner) will ever be able to dispense altogether with the ability to rely at intervals on some internal source of power, it will not be indispensable that this aerodrome of the future shall, in order to go any distance—even to circumnavigate the globe without alighting,—need to carry a weight of fuel which would enable it to perform this journey under conditions analogous to those of a steamship, but that the fuel and weight need only be such as to enable it to take care of itself in exceptional moments of calm.”
Mr. Octave Chanute, in his admirable chronicle entitled “Progress in Flying-Machines,” which will soon be published, says in one of his closing chapters: “But it is possible to utilize a still lighter power [than that of engines], for we have seen that the wind may be availed of under favorable circumstances, and that it will furnish an extraneous motor which costs nothing and imposes no weight upon the apparatus.
“Just how much power can be thus utilized cannot well be told in advance of experiment; but we have calculated that under certain supposed conditions it may be as much as some six-horse power for an aeroplane with one thousand square feet of sustaining surface; and we have also seen that while but few experimenters have resorted to the wind as a motor, those few have accomplished remarkable results.”
The indications seem to be that we must try to construct a machine analogous to the sailing-yacht rather than to the steamship, though perhaps the aerial machine of the future will be, so far as power is concerned, analogous to the yacht Sunbeam with its auxiliary screw.
Before continuing further with this subject, I wish to call attention to certain facts concerning the storage of power and the flight of soaring birds. First, in regard to the storage of power. It is well known that the construction of a useful electric storage-battery presents a most difficult problem. Such a storage device is needed for use upon the surface of the earth; yet, for purposes of aerial navigation, there is a much simpler accumulator which can be used. Take, for example, one hundred pounds of lead and let energy be stored in it by giving it altitude, just as energy is stored in the weight of a clock when it is wound.
What is known as one-horse power is the amount of energy which must be exerted in lifting thirty-three thousand pounds at the rate of one foot per minute, or five hundred and fifty pounds at the rate of one foot per second, or fifty-five pounds at the rate of ten feet per second. To give an illustration, it may be stated that if a man weighing one hundred and sixty-five pounds ascends a flight of steps ten feet high in three seconds, he exerts for the time being just one standard horsepower.
A small balloon which can lift one hundred pounds of lead three hundred and thirty feet high in one minute exerts one-horse power.
The lead when lifted to this height has stored within itself thirty-three thousand foot-pounds of energy.