CHAPTER XXIX 

THE ENGINES OF THE SHIP 

     How much engine power should we install in our ship? What speed should we aim at? It would not be difficult to put in a motor of 200 or even 300 or 400 horse power. Indeed, at one time we thought of using a 200 horse power en­gine, and ordered a special motor of that size built in England, though it was not finished in time for our use. Now, a 200 horse-power en­gine would give the America a speed, in still air, of about twenty-seven statute miles per hour. The fuel consumption of the engine would be approximately 135 pounds per hour, or five pounds per mile. Could we afford this relatively high speed? 

     A moment's calculation showed that for motor­ing 3,500 miles at this speed we should need at least 17,500 pounds of fuel in our bunkers, and at that should have no reserve. What could we do with a smaller motor—say one of 80 horse power? It would yield twenty miles per hour in still air, or nearly four-fifths as much as the en­gine of two and a half times greater power. 

     The reader may be surprised at this. But he should remember that with airships, as with all other forms of propelled vehicles, an increase of speed calls not merely for a corresponding in­crease of energy, but that the energy applied must theoretically be augmented as the square of the speed, and in practice somewhat more. 

     We knew from our two voyages in Spitz­bergen that a motor of 80-90 horse power, run­ning at an output of 70, would drive the America about twenty statute miles per hour at a cost of forty-five pounds of gasoline, or less than 2.5 pounds per mile; and that therefore with this power and speed we could theoretically motor the 3,500 miles which separate Europe from America with about 8,000 pounds of fuel. 

     Now, in the enlargement of the airship we planned to carry about 9,000 pounds of gasoline in our bunkers, but could not well undertake to provide lifting force for nearly double that quantity, which would be necessary if we tried to drive the ship at the higher speed. Hence, we decided upon equipping the America with the same engines she carried in August, 1909, when she sallied forth from our base in Spitzbergen, and was making more than twenty miles per hour over the ice-fields of the Arctic Sea toward the Pole when an accident compelled us to turn about and make for the land. 

     Each of these motors is rated at eighty to ninety horse power, according to the number of revolutions per minute. One is a Lorraine-Dietrich automobile engine, heavy, trustworthy, enduring, solid, economical of fuel. It weighs, with its radiator and equipment, nearly one thousand pounds. It drives, at 500 revolutions per minute, a pair of twin wooden screws each twelve feet in diameter, placed at either end of the engine shaft, that, on either side of the steel car. The other is an E. N. V. automobile or aeronautic engine, eight cylinders, an admirable engine that runs almost without vibration and that is capable of working a long time at a stretch. It drives a pair of wooden* propellers, 10.5 feet in diameter, 750 revolutions per minute. 

     These propellers, by an invention of Engineer Vaniman's, patented in Europe, may at any mo­ment be turned to any angle of thrust we may desire. That is to say that while normally they work, as do the pair on the other engine, in push­ing the ship straight forward, if we wish to util­ize all or a part of the thrust to send the craft upward or downward we are able to do so, while the engine is running, by turning a wheel which operates a miter gear. Under some circum­stances this may be a highly advantageous ar­rangement. 

     We did not plan to run both of our propelling engines at the same time, though we could do so in an emergency. Though both together would give the ship a speed of about 25 miles per hour, the extra five miles would be too costly in consumption of fuel. Each engine and its propulsive system is independent of the other. If one should be temporarily or permanently dis­abled the other is in reserve. 

     By running one motor at a time, each in its turn, while the other cools and is lubricated and inspected, both should be kept in first class con­dition throughout a long voyage, barring acci­dents. Our hope was that we might have a driving motor in operation virtually the whole duration of the voyage. With our 9,000 pounds of gasoline and lubricant, we should have in our bunkers almost, if not quite, 200 hours of motor­ing with one engine, equivalent to approximately eight days, or a theoretical 4,000 miles (about 3,500 knots.) 

     Thus, so far as advance calculations are of value, and considering gasoline alone, the Amer­ica was to set forth with a rather small margin of fuel endurance—enough for a run of about 3.500 knots, with a voyage of 3,000 knots be­fore her. 

     Thousands of visitors to the airship at Atlantic City asked if we carried along with us any means of replenishing the gas during the trip. We did not. It could be done; that is, hydrogen could be carried in steel bottles, compressed to 125 or 150 atmospheres, and be emptied into the reservoir overhead in case of need, the steel bot­tles being thrown overboard to lighten the ship. But it was not necessary in our case. 

     The balloon part of our airship was so well made, so nearly gas tight, that we did not look for any loss 'by leakage of gas of more than 11/2 or 2 per cent. per day. A few years ago we inflated the balloon with ordinary coal gas in the old Exposition Building at Paris, and found the rate of loss to be not more than .6 of one per cent. daily, indicating an average loss of about 1.5 per cent. when using hydrogen. 

     Later at Spitzbergen we confirmed this indica­tion. And at Atlantic City, where the ship was inflated for several weeks, we found the envelope of the reservoir to be in substantially its original good condition of gas tightness. During the voyage we reckoned that the loss of lifting force due to leakage of gas should not exceed, at the highest, 2 per cent daily, or under 500 pounds. Now, we expected the motors to consume 1,000 pounds of gasoline, perhaps a little more, each day, reducing by that much the load carried by the ship. Hence, instead of losing lifting force by gas leakage, we should gain an average of about 500 pounds daily. 

     did not. It could be done; that is, hydrogen could be carried in steel bottles, compressed to 125 or 150 atmospheres, and be emptied into the reservoir overhead in case of need, the steel bot­tles being thrown overboard to lighten the ship. But it was not necessary in our case.

The balloon part of our airship was so well made, so nearly gas tight, that we did not look for any loss 'by leakage of gas of more than 11/2 or 2 per cent. per day. A few years ago we inflated the balloon with ordinary coal gas in the old Exposition Building at Paris, and found the rate of loss to be not more than .6 of one per cent. daily, indicating an average loss of about 1.5 per cent. when using hydrogen.

Later at Spitzbergen we confirmed this indica­tion. And at Atlantic City, where the ship was inflated for several weeks, we found the envelope of the reservoir to be in substantially its original good condition of gas tightness. During the voyage we reckoned that the loss of lifting force due to leakage of gas should not exceed, at the highest, 2 per cent. daily, or under 500 pounds. Now, we expected the motors to consume 1,000 pounds of gasoline, perhaps a little more, each day, reducing by that much the load carried by the ship. Hence, instead of losing lifting force by gas leakage, we should gain an average of about 500 pounds daily. 

     What the winds might do to help or hinder the America on her long voyage was an exceedingly important factor. Before this effort was de­cided upon, a thorough study was made of wind and weather conditions over the Atlantic Ocean. The United States Weather Bureau, under the direction of the eminent practical meteorologist, Professor Willis L. Moore, publishes monthly forecasts of the winds of the North Atlantic, based upon reports from vessel masters during the past twenty-five years. 

     In these admirable and comprehensive records the sea is divided into rectangular spaces each containing five degrees of latitude and five de­grees of longitude. In each of these spaces a diagram, known in meteorology as a wind rose, gives the probabilities of wind movement for the month in number of hours out of one hun­dred, from the various points of the compass, with the force of the wind on the Beaufort scale. 

     Analysis of these "roses" told us just the sort of wind we might expect. We found the gen­eral trend of the air currents to be from west to east throughout the months of July, August, September and October, there being little differ­ence between the months, as to prevailing direc­tion, but the winds growing in force as the autumn comes on. 

     Along the transatlantic steamer routes in September the winds blew about 60 per cent. of the time from the western semicircle, and are somewhat stronger than those from the eastern semicircle. In October the time percentage is a little greater for the winds from the west, and the force of all winds markedly increases. 

     We found that the prevalent direction of the winds was not only favorable to our voyage, but that the conditions were remarkably well dis­tributed throughout the whole of the prospective course. Careful analysis in detail showed that in September (the month in which we reckoned upon being able to start) we might expect an average net wind movement of from six to eight miles in our favor. 

      Upon these facts we based our hope of a suc­cessful voyage. With our airship equipped to cross the ocean, theoretically at least, with her own power and fuel, considering the winds as neutral, or helping as much as they hindered, it seemed reasonable to hope for a fortunate out­come at a time of the year when the wind re­sultant is distinctly in our favor. 

     Often we were asked if we are not afraid of running into a cyclonic storm coming up from the West Indies—if there would not be danger of the airship being torn in pieces if caught in one of the gales which are born of the progress of an area of low barometer across the Atlantic. We were not afraid of cyclones from the West Indies. In fact, we think we should have wel­comed the appearance of one in our wake after we got well out to sea. 

     These cyclonic storms from the Wrest Indies almost invariably turn to the northeastward off Hatteras and make for the British Islands with increasing velocity, their average speed across the North Atlantic, or at least a part of the way, running from twenty to thirty miles per hour. Their general course is so well defined that we did not fear them on the score of the direction in which they would carry our ship. 

     It is true that occasionally one of these storms —"lows," in which the revolving currents move in a direction contrary to the hands of a watch —veers far off to the north in midocean. Should we have been involved in one of these the America might have been carried northward, possibly to her old headquarters at the 80th parallel of north latitude in Spitzbergen. But that was a remote chance which we were willing to risk.