Chanute, 1891, Aerial navigation
Contents
Octave Chanute, Aerial navigation. A lecture delivered to the students of Sibley College, Cornell University. [May 2, 1890] Railroad and Engineering Journal 1891.
Premise
Distinction between aeronautics and aviation (p.3):
[...] even now the students of the problem are divided into two camps or schools, each of which expects flight to be compassed by somewhat different apparatus. These are:
1. AERONAUTS, who believe that success is to come through some form of balloonm and that the apparatus must be lighter than the air which it displaces.
2. AVIATORS,* who point to the birds, believe that the apparatus must be heavier than the air, and hope for success by purely mechanical means.
Curiously enough, there seems to be very little concert of study between these two schools. Each believes the other so far wrong as to have no chance of ultimate success.
* From avis, a bird. This comparatively recent French terms seems so appropriate as to warrant its adoption into English.
Chanute addresses the history of each domain separately.
Aeronautics
He begins aeronautics with Montgolfier in 1783 and describes balloons as unwieldy until the use of motor & screw in 1852. And "until 1884 no balloon had ever come back to its starting point." The spheroid shapes efficient for containing gas are terribly inefficient in surmounting air resistance.
- 1852, 24 Sept - Henri Giffard flies "elongated balloon filled with ordinary coal gas, driven by aerial screw propeller actuated by a steam-engine of his own designing. [...] It was in shape a symmetrical spindle, 144 ft. long and 39 ft. in diameter. The screw was three bladed and 11 ft. in diameter. The steam-engine was of 3 H.P. and weighed with the empty boiler 330 lbs., or 110 lbs. per H.P."
- 1855 - Giffard's second trial, with more elongated balloon (230' long, 33' diameter). Chanute considered both attempts dangerous due to insufficient precautions with fire and inflammable gas: "Giffard went up with a lighted steam furnace under a gas bag open to the air through its lower valve and he came down safely not once only, but twice ; and yet other aeronauts believe the practice so dangerous that not one thus far has repeated the experiment" (p. 10).
- 1872, October - Henri Dupuy de Lôme constructs navigable balloon with goal of returning to origin — in response to the siege of Paris, but not finished in time. 118 1/2 feet long, 48 2/3 feet diameter; 120,088 cubic feet of hydrogen; lifting power 8,358 lbs. "Its principal features of novelty were a system of triangular suspension, by which all weights were concentrated at a single point a short distance above the car, and the introduction inside of the gas bag of an air pocket or bag, say one-tenth in cubic displacement of that of the balloon, so as to keep it distended and rigid at all times, by blowing in or letting out air." [ link: Balloon within balloon ? ] Speed of 6.26 mph (perhaps overestimated) not enough to overcome wind.
- 1883 - Gaston Tissandier & Albert-Charles Tissandier construct "electrical balloon"; 92' long, 30' diameter; 37,439 cubic feet of hydrogen; lifting power 2,728 lbs. 99-lb. Siemens engine powered by 517-lb. bichromate of potash battery; screw 9.18 ft. diameter, two arms, 180 rpm. "The netting in this case was formed of flat ribbons sewed to longitudinal gores, which arrangement was found materially to diminish the air resistance to the ordinary twine netting." Trial 8 October 1883, just able to overcome 6.7 mph wind. Trial 26 September 1884: possible speed of 9 mph, vessel unable to return to origin.
- 1884-5 - La France: Charles Renard & Arthur Krebs construct balloon for French War Department at Calais. 165' length, 27.5' diameter; assymetrical, with larger bulge toward front ("as obtains in the case of birds and fishes"); screw in front instead of behind (as had been done); internal air bag as in the de Lôme balloon; whole vessel enclosed in shed before trial; 65,836 cub feet hydrogen; 4,402 lbs. lifting power; screw 23' diameter
- 1884, August 9 : First trial; travelled at 10.25 mph, went ~2.5 miles away, and returned to starting point.
- 1884, September 12 : La France travelled at 12mph but had to land suddenly and couldn't return to start.
- 1884, November 8 : Two successful voyages; (top) speed 13.42mph.
- 1885: August 25 : 13.42mph; forced descent
- 1885: September 22 : 13.42mph, return to Calais
- 1885: September 23: 14.00mph, return to Calais
"Since 1885 no outdoor experiments have been made so far as the public is aware but it is understood that numerous experiments have been actively carried on within doors, which, being intended to improve a war engine, have been surrounded with a profound mystery." Nevertheless some papers published recently by Renard. Speculation that French motors are very advanced; will travel 28mph; and dominate the skies in the next war. (pp. 15-16)
Chanute lists the various obstacles and possibilities for ballooning. Problems which he considers still unsolved include longitudinal and altitudinal (balloon rising and falling with changing gas temperature) stability. He identifies speed as the number one issue, and suggests the need for:
- More aerodynamic hull
- More efficient screws
- Lighter/efficient motors
- Larger vessels: "for, inasmuch as their contents, and consequent lifting power, will increase as the cube of their dimensions, while their weight will, approximately, only increase as the square, the surplus lifting power will evidently increase with the size, and greater motive power in proportion can be used" (p. 19).
Aviation
The old desire for mechanically powered flight, inspired by birds, has been revived in the past 20-odd years (i.e. since 1870) — but theoretical interest has not yet yielded practical results.
Three schools within aviation:
- Flight by flapping in imitation of birds.
- Lifting motion and forward motion from screws.
- Lifting motion from wings and forward motion from screws.
In the first category, Chanute cites a 12" long flapping apparatus designed by Pichancourt, flying 30–60'.
In the second category, he refers to a French inventor 25 years ago (1865) but dismisses these aircraft as requiring too much energy to stay aloft.
Thus, he favors the third category of aircraft which use fixed wings (aeroplanes).
Books mentioned:
- Duke of Argyle, The Reign of Law
- M. Mouillard, Empire de l'Air
- Dr. Pettigrew, Animal Locomotion
- Prof. Marey, Le Vol des Oiseaux
International Congress of Aeronauts and Aviators held in Paris in August 1889. Russian engineer Drzewieki "starting from the best empirical formulae he could find, had calculated the weights sustained, the surfaces required, and the power needed for aeroplanes in artificial flight at various velocities" (p. 27). He argued that birds stay aloft due to lift moreso than flapping. For this to work, the wings must be inclined at an angle <6° to the line of flight. In fact the optimal angle may be between 1° and 2°.
This and other findings suggest that "if aeroplanes are ever built to carry tons of weight, their proportion of surface to weight may be considerably less than those which obtain with birds, but that the speed will need to be greater than that of flying animals in order to obtain support from the air, while the motive power required will vary approximately only in the direct proportion of the weight carried."
Drzewieki also recommends a low center of gravity, and a minimized distance between center of gravity and center of pressure.
Chanute: "My own estimate of the power required by a common pigeon gliding at an angle of 1° with the horizon was 9.33 H.P. per ton of his weight, and 10.49 H.P. per ton at an angle of 2° for this same velocity of 25 miles per hour.
"These are considerably less than the powers required to drive a balloon of moderate size at the same speed, for we have already seen that the air-ship La France would require 51 H.P. to attain 25 miles per hour; or, as it weighs 2.2 tons, the motor would needs develop 23.2 H.P. per ton of the weight of the whole apparatus." (30)
He goes on to consider steam, gas, and electric motors. He thinks gas (combustion) motors are the most promising.
Remaining difficulties include stability and the achievement of initial velocity (for which birds cannot provide clear examples, because weight is a more important factor).
His prediction:
Success with aeroplanes, if it comes at all, is likely to be promoted with the navigable balloon. It now seems not improbable that the course of development will consist, first, in improvements of the balloon, so as to enable it to stem the winds most usually prevailing, and then in using it to obtain the initial velocities required to float aeroplanes. Once the stability of the latter is well demonstrated, perhaps the gas-bag can be dispensed with altogether, and self-starting, self-landing machines substituted, which shall sail faster than any balloon ever can.
Link
- Full text at the Internet Archive
| Original title | Aerial navigation. A lecture delivered to the students of Sibley College, Cornell University. [May 2, 1890] |
|---|---|
| Simple title | Aerial navigation |
| Authors | Octave Chanute |
| Date | 1891 |
| Countries | US |
| Languages | en |
| Keywords | aerial navigation |
| Journal | Railroad and Engineering Journal |
| Related to aircraft? | 1 |
| Page count | 36 |
| Word count | |
| Wikidata id |
