Cayley, 1837, Practical remarks on aerial navigation

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George Cayley. "Practical Remarks on Aerial Navigation". Mechanics' Magazine, Vol. XXVI, No. 708. 4 March 1837.

Online at Internet Archive.

Statement of the propulsion problem: Balloons must be constructed at a large size in order to contain a large enough volume of gas that they can rise and lift weight. The increasing weight requires more and more engine power and fuel, thus, some think, precluding the possibility of efficiently propelling a balloon. However, writes Caley, "it is not true that the larger balloon, though perfectly similar in make to the smaller one, will, when driven through the air at the same velocity, meet with double the resistance—if it were so, the case of steering balloons would be hopeless, and on this mistaken ground many think it a vain attempt."

Instead, argues Cayley, since air resistance is proportional to the side of the surface exposed to the oncoming air, it increases at half the rate of the lifting capacity. Here he considers the case of two balloons, the second with twice the diameter of the first. Even if an engine generating four times as much horsepower will be four times as heavy, it will be lifted by a balloon with eight times the capacity.

If balloons of the respective diameters of one and two, both being spherical, be driven through the air with equal speed, the resistance will be as the surfaces opposed to the air, and the surface of the largest will be four times greater than that of the smaller, and hence will require four times the engine force to keep of the velocity; but the quantity of gas contained in the larger balloon is eight times greater than that in the smaller, hence it could sustain eight times as much engine power; but four times that power would keep up the required velocity, and hence it could carry a cargo of the weight of its engine, and yet keep pace with the smaller balloon. The simple terms of the case are, that the surfaces (and hence the resistances) increase as the squares of the diameter of the balloon; whereas the capacity to contain gas (and hence the supporting power) increases as the cubes of the diameter.
From this unquestionable law it follows, that if similar shaped balloons vary in diameter as the numerals, 1, 2, 3, 4, 5, &c, the resistance they will meet with in the air, at the same velocity, when compared to the weight (or engine-power) they will sustain, will be as 1, 1/2, 1/3, 1/4. 1/5, &c. This is a most important fact, and proves that as the law of relative dimunition to resistance is unlimited, there must ever be, theoretically, some bulk in which any species of first mover, however sluggish in proportion to its weight, would find itself suspended, and its power adequate to propel that bulk with the velocity required.


Original title Practical remarks on aerial navigation
Simple title Practical remarks on aerial navigation
Authors George Cayley
Date 1837
Countries GB
Languages [[en

Journal=Mech. Mag. Mus. Reg. Journ. Gaz.]]

Keywords LTA, aerodynamics, balloon
Journal
Related to aircraft? 1
Page count
Word count
Wikidata id

Sources

  • Brockett 1910, page 181, entry 2614: Cayley. Practical remarks on aërial navigation. Mech. Mag. Mus. Reg. Journ. Gaz., Vol. 26, No. 708 (March 1837), London, pp. 417-428, ill. (2614
  • Brockett 1910, page 181, entry 2617: Cayley, George. Practical remarks on aerial navigation. London, 1837, 8°, pp. 10, pl. 3. (2617
    • Indexed in Brockett twice; was it published separately as a pamphlet?