Propulsion

“ As the power applied to the propulsion of a vessel is only that which acts upon her in the direction of the keel,—and as, of the gross indicated power developed by her engine, one portion is absorbed in working the organs of its mechanism, another in overcoming the friction of the load, while still other proportions are expended in the slip of the propeller and in the friction of its surfaces on the water,—only that portion of the gross power which remains is applied to propulsion; and it is this remainder which varies in the ratio of the cube of the speed. ”

“ FOREWORD Although successful heavier-than-air flight is less than two decades old, and successful dirigible propulsion antedates it by a very short period, the mass of experiment and accomplishment renders any one-volume history of the subject a matter of selection. ”

“ But the total work done in propulsion is the same in both cases, therefore if is the efficiency under real conditions, we have—
The value of depends upon the lines of the vessel and position of the propeller, the essential point being the extent to which the frictional wake is led into the periptery of the propeller blades. It is manifest that is limited to a value less than the sternward component of the impressed velocity (compare § 200) . ”

“ But the very existence of the facilities of the engine-room, of the nimbleness of the clipper-moulded keel, of the capacity of the towering and exquisitely-calculated heights of cloths to snatch a desired power of propulsion from the teeth of the antagonistic gale, is, I take it, an admission of our own weakness when we contrast the ocean-machinery with which science has dowered us with the contrivances with which the early seamen triumphed over the forces of Nature and created new worlds as heritages for a self-complacent posterity. ”

“ Of these, (1) alone is to be regarded as a propeller loss; (2) is more correctly to be considered as a propulsion loss, for it is inevitable in the theory of propulsion and is not dependent on the instrument, whether it be a screw propeller or what not. ”

“ In this instance a very slight movement at the root of the pinion, or that end of the lever directed towards the body, is followed by an immense sweep of the extremity of the wing, where its elevating and propelling power is greatest—this arrangement ensuring that the large quantity of air necessary for support and propulsion shall be compressed under the most favourable conditions. ”

“ The report required by this section shall include information regarding existing, pending, and planned engine developments across a broad spectrum of thrust capabilities, including propulsion for sub-orbital, small, medium, and heavy-lift space launch vehicles. ”

“ Every change which has tended to increase the speed of racing boats has (like the changes in Poncelet's experiment) rendered necessary an increased energy, or, as one may say, an increased intensity of propulsion. ”

“ A type of engine specially devised for airship propulsion is that in which the cylinders are arranged horizontally instead of vertically, the main advantages of this form being the reduction of head resistance and less obstruction to the view of the pilot. ”

“ Primarily intended for the experimental investigation of any problems connected with ship resistance and propulsion, it has successfully dealt with such different problems as the manœuvring of ships, torques on rudder heads, skin friction, resistance due to rough seas, rolling and pitching of ships, stability of ships and hydroplanes in motion on the water, and the form of flying-boat hulls for efficient and stable action in getting on and off the water. ”

“ Their monstrous pilot then set the bar and advanced both levers of the dual power control out to the extreme limit of their travel.
There was no sense of motion or of acceleration, since the new system of propulsion acted upon every molecule of matter within the radius of activity of the bar, which had been set to include the entire hull. The passengers felt only the utter lack of all weight and the other peculiar sensations with which they were already familiar, as each had had previous experience of free motion in space. ”

“ When mechanical propulsion is the auxiliary power, we have a different problem. Take a vessel capable of being driven by sail at a speed of eight knots, and by her engines alone at four knots. Now, if she be sailing at a speed of eight knots, and we start her engine to make the number of revolutions necessary to induce a speed of four knots, the screw, not traveling as fast as the hull, will be dragged to the amount of the difference between its speed and the speed of the boat—four knots. ”

“ Experiments in marine propulsion also show that the thrust depends more on the disk [62] area than on the width of the blades. All the facts tend to show that for efficiency the blades of the propeller should be narrow, in order that the air may not be acted on for too long a time, and so put too much in motion, and the blades be so separated that one blade does not disturb the molecules of air upon which the next following one must act. ”

“ All attempts at propulsion with internal propellers—that is, by turbine wheels, pulsometers, ejectors, or by pumps—have failed in consequence of the great friction set up by the water in its rapid passage through the pipes from and to the sea ”

“ In general a flyer is subject to four forces: weight, thrust, air pressure and inertia. When these balance about any axis the craft has equilibrium about that axis; when they balance about the three axes the craft is completely balanced, and preserves its orientation in flight. Devices for preserving this complete balance have already been described; as also provision for propulsion and sustentation, launching and landing safely.
Thus at the close of the nineteenth century all the essential principles and contrivances of pioneer flight were worked out, except one—a suitable motor. ”

“ We have only arrived as yet at the infancy of the process, but we have made a good beginning, for, having once proved that a machine capable of raising itself in the air, wholly unaided from without, can be made, we have overcome with this apparently small result the whole difficulty. The principle of propulsion by means of a screw is by no means a novelty. It was first utilised in windmills, whose sails are nothing more nor less than an immense screw which is turned by the action of the wind on its surface. ”

“ It is evident that if a bird can, by altering its angle and altitude, so manipulate the wind coming within its grasp, that the portions that are moving in excess of the mean velocity have their velocity reduced, and those that are moving at less than the mean velocity are accelerated, the total energy of the wind will be reduced, and the energy thus taken from the wind may become available for the purposes of propulsion. ”

“ In effect, Jim—and you, Jerry—will grasp it much easier in this manner. If you had a machine throwing a jet of water, and it touched an opposing jet of water, your propulsion would build up till the limits of the energy from the opposing jets were reached. Suppose those jets continued to reach out. As light frequencies, till you built up your maximum. In a vacuum your speed would continue at that maximum velocity till you chose to decelerate. ”

“ Some such artificial propulsion was almost indispensable, as the prevailing calms rendered the use of sails unavailable. One of the earliest motive powers extensively employed was the expansive force of the vapour of water, raised at a high temperature; and for many hundred years these curious ships were in actual use. I have seen several of them which are still kept in a vast marine museum at Lasondre. ”

“ The importance of the propulsion-pneuma is this: It controls the master generators of electrostatic force, which are used both to move this planet and ours, and to perform the act of Translation. If the Pyramids control it, they may be able to take us out of circuit, perhaps back to Earth, perhaps throwing us into space, where we will die. ”

“ Some years ago experimental water-jet vessels were built in New York in which a jet only 5⁄8 inch in diameter with a pressure of 2,500 pounds per square inch was used, but the experiment proved a failure. The propelling force of a jet is the reaction of the stream of water against the orifice from which it issues. The action is just like Hero’s reaction steam turbine referred to on page 143. The propulsion would be the same were the jet discharged in the open air or in a vacuum or against a solid stone wall. ”

“ They move through the water very rapidly by a kind of jet propulsion, gulping water in the mouth and shooting it out explosively from the rear. They are little affected by changes in hydrostatic pressure, as are fish with air bladders. ”

“ The air balloonet to husband the gas supply and thus prevent the deformation of the outer container or support, as well as to provide stability; (2) the triangular suspension to attain longitudinal stability; and (3) the screw propeller for propulsion, beside selecting the proper location for the latter.
PROBLEMS OF THE DIRIGIBLE Ability to Float. If ability to rise in the air depended merely upon a knowledge of the principle that made it possible, it undoubtedly would have been accomplished many centuries ago. ”

“ The railroad originally was as completely dissociated from steam propulsion as was the ship. ”

“ The little cruiser rose slowly under the lift of the fans; then he opened the throttle and swept out in a parabolic curve that ended in a vertical line. Straight up, the ship roared. It shot through a stratum of clouds. The sun that was under the horizon shone redly now; it grew to a fiery ball; the earth contracted; the markings that were coastlines and mountains drew in upon themselves.
He passed the repelling area and felt the lift of its mysterious force—the "R. A. Effect" that permitted the high-level flying of the world. His speed increased. ”

“ Invading the realms of fancy? Well, perhaps so, but at any rate it is possible that extraordinary speed through space may be secured if means are found to maintain the impulse of the engine and the thrust-drift efficiency of the propeller at great altitude. ”

“ Instead of the wind possessing32 the speed, in this instance, it is you who provide it. The motor of an aeroplane, driving the propeller of the machine, turns this at 1000 or more revolutions a minute, and causes its curved blades to screw forward through the air as they turn, like those of a ship's propeller through water—or a gimlet into wood. The propeller, as it bores its way into the air, draws or pushes the aeroplane across the ground; and the speed grows rapidly until the air, sweeping with an increasing pressure beneath the planes, becomes sufficient to bear the craft in flight. ”

“ In such a case the pitch is the mean effective pitch.
§ 14. Blade Area.—We have already referred to the fact that the function of a propeller is to produce dynamic thrust—to drive the aeroplane forward by driving the air backwards. At the same time it is most desirable for efficiency that the air should be set in motion as little as possible, this being so much power wasted; to obtain the greatest reaction or thrust the greatest possible volume of air should be accelerated to the smallest velocity. ”

“ That as the object of wing or screw is to mount upon the inertia of the particles of a mobile fluid, and as the rotation of steamship propellers in water—a fluid of many times the inertia of air—is already in excess of the highest speed heretofore tried in the propellers of moderately successful flying machines, it is plain that the speed employed in water must be many times exceeded in air. ”

“ THRUST-DRIFT RATIO.—The proportion of thrust to drift is of paramount importance, for it expresses the efficiency of the propeller. It is affected by the following factors: Speed of Revolution.—The greater the speed, the greater the proportion of drift to thrust. This is due to the increase with speed of the passive drift, which carries with it no increase in thrust. For this reason propellers are often geared down to revolve at a lower speed than that of the engine.
Angle of Incidence.—The same reasons as in the case of the aeroplane surface. ”

“ The lift or descent of the gravitor sufficed for climbing or diving maneuvers. He'd looked like a human fish swimming in the sky.
For the ships, of course, such a jet unit wouldn't do. The ships needed jets which would work while in motion, at speeds exceeding a hundred miles an hour. Thus, they'd had to fly the ship until its gravitors completely polarized its hull. Then they had to determine the air-flow over that hull at flying speeds with flow and pressure indicators mounted on the hull. ”

“ Curtiss’ method of control led the way to the modern type of wing aileron and the general system of control was basically the same as that in use today.
POWER FOR THE AIRPLANE
Going back to the four forces that govern the flight of a plane, we find thrust pulling the plane forward. Thrust is the force that keeps the plane in the air; without it the airplane could not leave the ground for sustained flight. Thrust is created by the propeller. The propeller blades function in the same manner as the wings. ”

“ Its striking against the atmosphere makes a counter-pressure against the outside of the stem-head. Up to 30 kilogrammes to the square metre, therefore, all increase in the air-ship's speeds tends to reduce strain—so that the faster the air-ship goes, the less will it be liable to burst its head!
How fast may the balloon be carried on by motor and propeller before its head-stem strikes the atmosphere hard enough to more than neutralise the interior pressure ? ”