Chapter XVI : MINING THE AIR

While the anti-aircraft gun represents the only force which hasbeen brought to the practical stage for repelling aerial attack,and incidentally is the sole offensive weapon which hasestablished its effectiveness, many other schemes have beendevised and suggested to consummate these ends. While some ofthese schemes are wildly fantastic, others are feasible withincertain limitations, as for instance when directed againstdirigibles.

It has been argued that the atmosphere is akin to the salt seas;that an aerial vessel in its particular element is confrontedwith dangers identical with those prevailing among the waters ofthe earth. But such an analogy is fallacious: there is no moresimilarity between the air and the ocean than there is between anairship and a man-of-war. The waters of the earth conceal fromsight innumerable obstructions, such as rocks, shoals, sandbanks,and other dangers which cannot by any means be readily detected.

But no such impediments are encountered in the ether. The craftof the air is virtually a free age in the three dimensions. Itcan go whither it will without let or hindrance so long as themechanical agencies of man are able to cope with the influencesof Nature. It can ascend to a height which is out of allproportion to the depth to which the submarine can descend insafety. It is a matter of current knowledge that a submarinecannot sink to a depth of more than 250 feet: an aerial vessel isable to ascend to 5,000, 8,000, or even 10,000 feet above theearth, and the higher the altitude it attains the greater is itsdegree of safety. The limit of ascension is governed merely bythe physical capacities of those who are responsible for theaerial vessel's movement.

It is for this reason that the defensive measures which arepractised in the waters of the earth are inapplicable to theatmosphere. Movement by, or in, water is governed by the depthof channels, and these may be rendered impassable or dangerous tonegotiate by the planting of mines. A passing ship or submarinemay circumvent these explosive obstructions, but such asuccessful manoeuvre is generally a matter of good luck. So faras submarines are concerned the fact must not be over looked thatmovements in the sea are carried out under blind conditions: thenavigator is unable to see where he is going; the optic facultyis rendered nugatory. Contrast the disability of the submarinewith the privileges of its consort in the air. The latter isable to profit from vision. The aerial navigator is able to seeevery inch of his way, at least during daylight. When darknessfalls he is condemned to the same helplessness as his confrere inthe waters below.

A well-known British authority upon aviation suggested thatadvantage should be taken of this disability, and that the airshould be mined during periods of darkness and fog to secureprotection against aerial invasion. At first sight the proposalappears to be absolutely grotesque, but a little reflection willsuffice to demonstrate its possibilities when the area to bedefended is comparatively limited. The suggestion merelyproposes to profit from one defect of the dirigible. The latter,when bent upon a daring expedition, naturally prefers to make abee-line towards its objective: fuel considerations as a matterof fact compel it to do so. Consequently it is possible, withincertain limits, to anticipate the route which an invading craft will follow: the course is practically as obvious as if thevessel were condemned to a narrow lane marked out by sign-posts.Moreover, if approaching under cover of night or during thickweather, it will metaphorically "hug the ground." To attempt to complete its task at a great height is to court failure, as therange of vision is necessarily so limited.

Under these circumstances the mining of the air could be carriedout upon the obvious approaches to a threatened area. The mines,comprising large charges of high-explosive and combustiblematerial, would be attached to small captive balloons similar tothe "sounding balloons" which are so much used by meteorologistsin operations for sounding the upper strata of the atmosphere. These pilot balloons would be captive, their thin wires beingwound upon winches planted at close intervals along thecoast-line. The balloon-mines themselves would be sent tovarying heights, ranging from 1,000 to 5,000 feet, and withseveral attached to each cable, the disposition of the minesin the air in such an irregular manner being in fact closelysimilar to the practice adopted in the mining of a channel forprotection against submarines and hostile ships.

The suggestion is that these mines should be sent aloft at duskor upon the approach of thick and foggy weather, and should bewound in at dawn or when the atmosphere cleared, inasmuch as infine weather the floating aerial menace would be readily detectedby the pilot of a dirigible, and would be carefully avoided. Ifthe network were sufficiently intricate it would not be easy foran airship travelling at night or in foggy weather to steer clearof danger, for the wires holding the balloons captive would bedifficult to distinguish.

The mines would depend upon detonators to complete their work,and here again they would bear a close resemblance to sea-mines.By looping the mines their deadliness could be increased. Theunsuspicious airship, advancing under cover of darkness or thickweather, might foul one of the wires, and, driving forward, wouldtend to pull one or more mines against itself. Under the forceof the impact, no matter how gentle, or slight, one or more ofthe detonating levers would be moved, causing the mine toexplode, thus bursting the lifting bag of the vessel, and firingits gaseous contents. An alternative method, especially when acable carried only a single mine, would be to wind in the captiveballoon directly the wire was fouled by an invading aerial craft,the process being continued until the mine was brought againstthe vessel and thereby detonated.

Another proposed mining method differs materially in itsapplication. In this instance it is suggested that the minesshould be sent aloft, but should not be of the contact type, andshould not be fired by impact detonators, but that dependenceshould be placed rather upon the disturbing forces of a severeconcussion in the air. The mines would be floating aoft, andthe advance of the airship would be detected. The elevationof the mines in the vicinity of the invading craft would beknown, while the altitude of the airship in relation theretocould be calculated. Then, it is proposed that a mine within dcertain radius of the approaching craft, and, of course, belowit, should be fired electrically from the ground. It ismaintained that if the charge were sufficiently heavy and anadequate sheet of flame were produced as a result of theignition, an airship within a hundred yards thereof would beimperilled seriously, while the other mines would also be fired,communicating ignition from one to the other. The equilibriumof the airship is so delicate that it can be readily upset, andtaking into account the facts that gas is always exuding fromthe bag, and that hydrogen has a tendency to spread somewhat inthe manner of oil upon water, it is argued that the gas would beignited, and would bring about the explosion of the airship.

Another method has even been advocated. It is averred inauthoritative circles that when the aerial invasion in force ofGreat Britain is attempted, the Zeppelins will advance under thecover of clouds. Also that the craft will make for one objective--London. Doubtless advantage will be taken of clouds,inasmuch as they will extend a measure of protection to the craft,and will probably enable the invading fleet to elude the vigilanceof the aeroplane scouts and patrols. Under these circumstances itis suggested that balloon-mines should be sent aloft and beconcealed in the clouds. It would be impossible to detect thewires holding them captive, so that the precise location of the lurking danger would not be divined by the invader. Of course,the chances are that the invading airship would unconsciouslymiss the mines; on the other hand the possibilities are equallygreat that it would blunder into one of these traps and be blownto atoms.

An English airman has recently suggested a means of mininginvading Zeppelins which differs completely from the foregoingproposals. His idea is that aeroplanes should be equipped withsmall mines of the contact type, charged with high explosives,and that the latter should be lowered from the aeroplane and betrawled through the atmosphere. As an illustration I will supposethat a hostile aircraft is sighted by a patrolling aeroplane.The pilot's companion in the latter immediately prepares hisaerial mine, fixing the detonator, and attaching the mine to thewire. The latter is then dropped overboard, the wire being paidout from a winch until it has descended to the level of thehostile craft. The airman now manoeuvres in the air circlingabout the airship, dragging his mine behind him, and endeavouringto throw it across or to bring it into contact with the airshipbelow. Naturally the latter, directly it observed the airman'sobject, would endeavour to elude the pursuing trawling mine,either by crowding on speed or by rising to a greater altitude.The aeroplane, however, would have the advantage both in point ofspeed and powers of climbing, while there is no doubt that thesight of the mine swinging in the air would exert a decisivemoral effect upon those in the airship.

Attempts to render the mine harmless by discharging itprematurely with the aid of rifle and machine-gun fire would, ofcourse, be made by the crew of the airship, but the trawling minewould prove a very difficult target to strike. If such a missilewere used against an airship of the proportions of a Zeppelin themine would inevitably be trawled across the vessel sooner orlater. Once the airship had been fouled, the aviator wouldmerely have to drive ahead, dragging the wire and its charge across the gas-bag until at last one of the contact levers of themine was moved by being dragged against some part of the vessel,when the mine would be exploded. In such operations the aviatorwould run a certain risk, as he would be more or less above theairship, and to a certain degree within the zone of the ultimateexplosion. But there is no doubt that he would succeed in his "fishing" exploit within a very short time.

This ingenious scheme has already been tested upon a small scaleand has been found effective, the trawling bomb being drawnacross its target and fired by contact within a few minutes. Theexperiment seems to prove that it would be simpler and moreeffectual to attack a hostile aircraft such as a Zeppelin in thismanner than to drop free bombs at random. Moreover, we cannotdoubt that the sight of a mine containing even ten or twelvepounds of high explosive dangling at the end of a wire wouldprecipitate a retreat on the part of an airship more speedilythan any other combative expedient.

The advocate of this mine-trawling method, who is a well-knownaviator, anticipates no difficulty in manoeuvring a mine weighing30 pounds at the end of 300 feet of fine wire. Success dependsin a great measure on the skill of the aviator in maintaining aconstant tension upon the line until it falls across itsobjective.

The process calls for a certain manifestation of skill inmanoeuvring the aeroplane in relation to the airship, judgment ofdistance, and ability to operate the aeroplane speedily. Therapid ascensional capability of the airship, as compared withthat of the aeroplane, is a disadvantage, but on the other hand,the superior mobility and speed of the aeroplane would telldecisively for success.

Among the many wonders which the Krupp organisation is stated tohave perfected, and which it is claimed will create considerablesurprise, is the aerial torpedo. Many of the Krupp claims arewildly chimerical, as events have already proved, but there is nodoubt that considerable effort has been expended upon this latestmissile, for which the firm is said to have paid the inventorupwards of L25,000--$125,000. Curiously enough the projectilewas perfected within gunshot of the British aerodrome of Hendonand is stated to have been offered to the British Government atthe time, and to have met with a chilling reception. One fact,however, is well established. The inventor went to Germany, andsubmitted his idea to Krupp, by whom it was tested without delay. Upon the completion of the purchase, the great armamentmanufacturers did not fail to publish broadcast the fact thatthey had acquired a mysterious new terror of the skies. That wassome three years ago, and in the interval the cleverest brains ofthe German firm have been steadily devoting their time andenergies to the improvement of the missile, the first appearanceof which was recorded, in a somewhat hazy manner, in the closingdays of December.

While the exact mechanism of this missile is a secret, thegoverning principles of its design and operation are known to aselect few technicians in this country. Strange to say, theprojectile was designed in the first instance in the interests ofpeace and humanty, but while engaged upon his experiments theinventor suddenly concluded that it would be a more profitableasset if devoted to the grim game of war. At the time themilitary significance of the airship and the aeroplane werebecoming apparent; hence the sudden diversion of the idea into adestructive channel.

This aerial torpedo is a small missile carrying a charge of highexplosive, such as trinitrotoluene, and depends for itsdetonation upon impact or a time fuse. It is launched into theair from a cradle in the manner of the ordinary torpedo, but theinitial velocity is low. The torpedo is fitted with its ownmotive power, which comes automatically into action as themissile climbs into the air. This self-contained energy is sodevised that the maximum power is attained before the missile haslost the velocity imparted in the first instance, the resultbeing that it is able to continue its flight in a horizontaldirection from the moment it attains the highest point in itstrajectory, which is naturally varied according to requirements. But there is no secret about the means of propulsion. The bodyis charged with a slow-burning combustible, in the manner of theordinary rocket, whereby it is given a rapid rotary motion.

Furthermore it is stated to be fitted with a small gyroscope inthe manner of the torpedo used in the seas, for the purpose ofmaintaining direction during flight, but upon this point there isconsiderable divergence of opinion among technicians, the generalidea being that the torpedo depends upon an application of theprinciple of the ordinary rocket rather than upon a small enginesuch as is fitted to the ordinary torpedo. The employment of aslow combustible ensures the maintenance of the missile in theair for a period exceeding that of the ordinary shell. It isclaimed by the Germans that this projectile will keep aloft forhalf-an-hour or more, but this is a phantasy. Its maintenance offlight is merely a matter of minutes.

The belated appearance of this much-lauded projectile and itsrestricted use suggest that it is unreliable, and perhaps no moreeffective than the aerial torpedo which appeared in the UnitedStates during the Spanish-American War, and proved a completefailure. An effective and reliable means of combating orfrustrating a dirigible attack, other than by gun-fire or resortto the drastic remedy of ramming the enemy, has yet to bedevised.

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Chapter XVI : MINING THE AIR

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