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from Blackwood's magazine (1910-jul)
VOL CLXXXVIII. NO. MCXXXVII., pp 3-13
NEW WARS FOR OLD.
By COLONEL À COURT REPINGTON, C.M.G.
II. THE AIRSHIP MENACE.
WHEN M. Blériot landed at Dover he opened a new chapter in the military history of the British Isles.
Our Navy declares and I hope with reason that it is able to destroy any and every enemy who approaches these islands of ours by sea. But our Navy has never pretended, and obviously cannot pretend, to exercise any effective control by strictly naval means over a foe who arrives in this country by any alternative route, whether above the sea or below it.
The Government is sometimes blamed for not having taken the lead in the fascinating science of aerial navigation, and for allowing us to remain several years behind France and Germany in the design and utilisation of airships of all kinds. There are some grounds for these complaints, but it was certainly not in our true interests to take the lead in promoting a science which is bound, though to what extent is a matter of opinion, to affect the predominant position which we have hitherto held at sea.
Unfortunately, we have passed beyond this stage. Practical airships have been constructed. Dirigibles and aeroplanes are in existence, and have already covered long distances, at great speed and with safety. Every year, not to say every month, progress is marked. With us or without us, these new auxiliaries of fleets and armies will continue to improve; and all that remains for us to do is to take measures to meet this new menace, if it is a menace, and to see that we are as well provided as our neighbours with these extremely unwelcome and quite novel arms.
I shall endeavour in this article, without dwelling unduly on technical details, to state what airships can do, what they may be expected to achieve in the immediate future, what changes in methods of war the introduction of this new factor is likely to bring about, and what guidance for our own conduct this investigation seems to suggest. Considering that practical aerostation is not much older than the century, and that the progress made in a few short years has been so astonishing, I think that we should be imprudent to maintain too conservative an attitude, and to refuse to the new science the hope of great progress hereafter. Thus, while we must distinguish between what airships can do now and what they may be expected to do, we must allow a wide margin of safety for inventive talent, for the awakened interest of governments, and for the relentless march of all-conquering human ingenuity.
There is a great variety in the type of airship in existence and projected. Military interest for the moment is continued to two namely, the rigid, semi-rigid, or non-rigid dirigible, and the aeroplane, whether monoplane, biplane, or other. The best known of the rigid-frame dirigibles is the Zeppelin. The improved Zeppelin can theoretically cover 1140 miles, and has already covered 800 miles, without descending. She has a speed of a little over 30 miles an hour on a calm day, and has risen to a height of 5600 feet. She can carry 15 passengers and a large supply of fuel, stores, and explosives.
The safety of this type upon which the dirigible now building at Barrow will, we hope, be an improvement is secured by distributing lifting power between seventeen separate balloons enclosed between partitions. Height control is derived from stabilising and balancing surfaces. The soaring power of the Zeppelin, thanks to her elevators, is said to be great without discharge of ballast. In the first Zeppelin an aluminium alloy known as wolframinium was used for rings, stays, and braces: the compartments contained 351,150 cubic feet of hydrogen, giving a lift of eleven tons. The reconstructed Zeppelin III., now known as Zeppelin VI., is said to have three motors which develop 350 H.P. In this airship, and in the Barrow ship, another aluminum alloy called duralumin is employed. The Zeppelin type has certain notorious disadvantages which have been demonstrated by the destruction of two of the kind by the elements. But, given proper provision for shelter or anchorage when descending to the ground, it is at present the most formidable, militarily speaking, of existing types of airships, because of its wide range, fair speed, and good carrying capacity.
It is, however, too early to decide whether this type, the semi-rigid Parseval, or the non-rigid Gross and her French peers, will ultimately be preferred for military purposes. The German Parseval III. has motors of 200 H.P. and a speed of 32 ½ miles an hour. The Gross II. has a capacity of 270,000 cubic feet. Her two motors, driving two propellers, give a speed of 33 ¾ miles an hour, which will probably be exceeded by the Gross III., which has double the power, though this does not mean double the speed. The French non-rigid or so-called "souple" types of dirigibles are smaller than the German, and of less power. The Ville de Nancy is 180 feet long, 33 feet broad, and has a capacity of 180,000 cubic feet. The Ville de Paris can carry six persons and about 1000 lb. of ballast or explosives, while she has a mean speed in a calm of about 25 miles an hour. The non-rigid airship has not at present the range nor the carrying capacity of the rigid type, but it can be deflated, packed up, sent anywhere by rail, and then used in the manner that the Gross II. was used at the German manœuvres last year. We must anticipate very interesting results from these airships before long, and we must bear in mind that the non-rigid type is handy, and may yet become a dangerous rival to the Zeppelin. Our little experimental Army airship the Beta, with her 35 H.P. and low speed, cuts a very sorry figure when compared with these foreign squadrons of the air.
The range of the aeroplane is in principle dependent on fuel supply, which in practice allows at present a flight of about 150 miles at the rate of 50 miles an hour without descending. The world's record for an aeroplane flight with two passengers is at present 2 hours and 51 minutes. As the pilot of an aeroplane is almost wholly occupied with navigating his craft, an aeroplane which cannot take a second passenger to make observations is of little use for military purposes. The aeroplane has risen to a height of 4146 feet. If its motor fails it must come down, though not necessarily to grief. Its high speed, simplicity, cheapness, portability, comparative invulnerability to fire, and power to ascend and descend with ease, are in its favour, but it cannot remain motionless in the air, its power in attack is as yet undeveloped, and it is adapted for the moment only to short flights.
To what extent are improvements likely to take place in the immediate future? Improvements in the tensile strength of aluminium alloys, and in the trustworthiness and power of motors, will certainly decrease weights and increase the speed of dirigibles, perhaps up to 40 miles an hour, and increase the range to 1500 miles or more for the rigid type. If reserve buoyancy can be supplied by compressed gas, the range will be greatly extended, while the same result will also be obtained by more scientific use of plane surfaces. Bulk is sure to remain great, and the extreme limits have probably not yet been reached. Size means gain in lifting power over areas, for the first cubes as the second squares. The temptation is therefore to build big, but other factors enter into the calculation as size increases and end by imposing limits to size. There is no immediate probability that any dirigible will be able to make headway against strong winds, but on calm days and in moderate winds the arrival of German dirigibles above some of our seaports and a part of our territory must be anticipated in time of war.
There is some loss of buoyancy in navigating above the sea owing to the condensing of moist air on an airship, but specially designed envelopes will doubtless overcome this difficulty. It is said that a fabric has been made which, in the dampest atmosphere, does not increase weight more than a third of an ounce to the square yard.
The greatest difficulty not yet wholly overcome is that of navigating the air with certainty in any given direction, especially over the sea, when there is no point de repère for observers aloft. It is probable that the gyro-compass, which has been successfully introduced into the German Navy, will prove suitable for airship work. A real difficulty to the airman is the danger that, even if an airship is apparently heading in the required direction at full speed, the movement of the air may all the time be causing a lateral or angular drift. An airship sextant, capable of rapid manipulation, is required to enable the airman to determine and maintain a course against lateral drift due to the wind. On the other hand, the power possessed by the airship of remaining at the same altitude where air currents are fairly constant is favourable to equable flight. With his German gyro-compass, with an accurate chronometer for determining longitude, with wind vanes on ball mountings to show leeway, and with anemometers connected with speed and revolution-counting indicators to record distance travelled, the airman is already pretty well equipped for locomotion in a required direction, even at sea, and such difficulties as still remain to be overcome do not appear great by the side of others which have already been surmounted. As for the fog so prevalent in the North Sea, M. de Lesseps showed us only the other day that even the aeroplane can rise above the banks and be steered by the sun.
The dirigible is the best existing type of airship for purposes of strategical reconnaissance and attack. Observers on the deck of a dirigible can see ships at a distance of 30 miles in fair weather. On land, isolated men can be observed from a height of 2000 feet, horses and small groups of men from a height of 3000 feet, while from a height of 4000 feet the Patrie observed the smallest movements of formed bodies of troops at the Satory camp and obtained very clear telephotographs of them. It is difficult to exaggerate the value of the dirigible for purposes of strategical reconnaissance, and as wireless telegraphy has been adapted to use by airships there cannot be much doubt that in favouring weather the best watch in the air will secure the advantage of prompt and accurate information of the movements of fleets and flotillas at sea and of masses on land.
It is possible for observers on airships to detect ships at sea from positions far beyond the reach of guns, and to escape destruction by artillery on land, thanks to speed, height above the ground, and the difficulty of ranging. It will not be very convenient to mount guns on airships, but specially designed guns will probably become necessary for use against other airships, and may be fired by compressed air. The projectiles of airship guns may possibly give out a jet of flame and a smoke "tracer" on discharge, but the Germans possess a sensitive fuze which is said to act upon contact with even such light fabrics as envelopes of airships. Whether some form of uninflammable gas, steam, or ammonia can be discovered or adapted to the use of dirigibles in order to overcome the dangers arising from inflammable hydrogen gas is a question that remains open. On the whole, helium, which is almost as light as hydrogen and not inflammable, appears to be the best substitute for hydrogen at present known, but very little isolated helium as yet exists.
Contrivances for dropping or firing explosives upon ships, troops, and works below will form the main offensive armament of the airship which will also strive to play the part of the hawk to the heron of the rival airship. An airship which can soar higher than her foe and travel faster has this foe at her mercy. Guns for repelling airship attack on sea or land will rely on flame-fire or sensitive fuzes. On rare occasions shrapnel may be effective if bullets of a special design are introduced into the shell.
An object moving through the air at a great height, not necessarily on a horizontal plane, at an unknown range, and at a speed of 25 to 40 miles an hour, is not easy to hit. The rigidity of the trajectory, admitted for the construction and use of sights for horizontal fire, is no longer true when firing into the air. Rifle-fire against an airship is practically unaimed fire unless special slights are introduced. The perforation of gas envelopes by small calibre bullets has, moreover, been proved by French and German experiments to have little effect in reducing buoyancy. The carriages of fieldguns, again, do not as a rule permit of fire at angles of elevation greater than 16° or 20° unless the trail is buried in the ground. At a height of 3000 to 4000 feet the airship will practically have nothing to fear from the fire of these weapons. Howitzers and some types of heavy artillery will theoretically be more effective, but we should be sanguine to suppose that the fire of any cumbrous cannon will be anything but most disappointing against such swiftly moving marks as modern airships. Effective fire against airships, whether from ships or from land, can only be expected from special guns using special projectiles. The Germans realised this fact at a very early date, and are well ahead of other Powers with their 7.5-c. and 10.5-c. anti-airship guns, which have an extreme vertical range of 6800 and 12,400 yards respectively. Messrs Vickers have designed a 3-pr. gun for high angle fire, but, thanks to the very thorough experiments at Dantzig and elsewhere, Germany is as far ahead of us in anti-airship artillery as she is in airships themselves.
While airships may use special artillery for attacking their kind, their main offensive menace will rest with the projectiles or explosives fired or dropped upon the mark below. It is true that we have signed and ratified an international declaration which prohibits "the discharge of projectiles and explosives from balloons, or by other new methods of a similar nature," but Germany is not a party to this declaration, so we are forced to ignore it. The velocity acquired by bombs dropped from a great height is considerable, and up to a certain point increases with the height. It is true that explosives are much less harmful against certain targets, for instance a bomb-proof, when they are not enclosed in a strong and heavy shell, but in the future contest between the airship bomb and the armoured deck the bomb will probably win in the end. At present spherical bombs to the number of thirty, with thin walls, and each containing 44 lb. of explosive substance, can be carried by an airship of the Patrie type. Very much more can be carried by the larger Zeppelins. The transport and the projection at one discharge of a ton of explosive substance are not beyond the reach of attainment, and this amount will be much more than enough to wreck any warship now afloat. It is commonly supposed that the sudden loss of weight caused by the discharge of projectiles will compromise the stability of airships. French experiments appear to show that this danger has been exaggerated, and it seems to be probable that loss of ballast can be compensated by a proper arrangement of escape valves.
M. Juchmès, the pilot of the Lebaudy, proved long ago that an airship can remain poised and practically immobilised in the air even in a wind. Very fair practice has already been made in dropping bombs on selected marks, and the conclusion at which the French appear to have arrived is that 50 per cent of projectiles dropped from a height of 4500 feet can be made to fall within a square with sides of 25 yards. The 'Punch' artist was a little behind the times when he depicted the disappointment of the foreign airmen who had "missed London." When more scientific instruments are devised, the 20-foot broad funnels of warships will be the airman's bull's-eyes. Already nothing prevents the effective offensive use of airships in war, within their present limits of range, and in favourable weather, which after all occasionally occurs, even in Scotland. The mean hourly wind velocity, judging by the "Challenger" observations, is only 17 miles at sea, while on land it is only 12 ½ miles, but increases in higher altitudes. Airships have to contend, over our islands, with a higher average velocity of wind than is found in France or Germany. But we must expect every year to hear of dirigibles with greater range, higher speed, and better carrying capacity, which in their turn will increase the military results which may be expected from these types in their three main duties namely, communication, reconnaissance, and attack.
Progress in the military use of aeroplanes will chiefly take the form of increased range and speed, and perhaps of increased size. The limit of range cannot be calculated with any precision, but may extend to 500 or even 1000 miles before very long, while enthusiasts expect a speed of 200 miles an hour, and consequently hope to combat the highest winds, which are not much over 100 miles an hour. The Gnome rotary engine has lately effected a marked improvement in aeroplane flight, and as better and lighter motors are placed on the market there is sure to be constant progress, while safety may be increased by duplicate engines and propelling gear. The fact that a skilful pilot of an aeroplane will be able to face winds which will keep dirigibles in their harbours will always give the aeroplane a place in the aerial forces of every nation, while for purposes of tactical reconnaissance, both on land and sea, the aeroplane promises to be invaluable. It will not easily be open to attack by the slower dirigible. It requires no expensive, complicated, and ponderous plant. It is much less exposed to the buffets of the wind when at rest. It may turn out to be the destroyer of the air, and in any case it is sure to have its use in war. It would be very imprudent for us to tie ourselves to any particular type of airship for naval and military purposes at this moment. We must excel in each type and remain constantly alert to what the foreigner is doing.
Scepticism respecting the utility of airships in war is not an attitude that can be justified any longer. We must all in the end yield to evidence and to proofs of tangible achievements. The questions then arise how airships are likely to be employed in a future war, how they can best be met, and what measures it behoves us to take. In case of war between England and Germany, the object of the latter will obviously be and quite rightly to use an arm which we do not yet possess in such a manner that she may obtain early and accurate information of our naval dispositions and movements, and at the same time cause us the maximum amount of moral and material damage.
In the discussion of an interesting paper read by Lord Montagu of Beaulieu before the National Defence Association last year, allusion was made to the probability of airship attack upon the nerve centres of London, such as the General Post Office, the Telephone Exchanges, the Bank of England, the Royal Palaces, the Railway Termini, and so on. Nearly all the speakers thought that such attacks were admissible and probable. It is true, and the fact may prove most interesting in its consequences, that the gobe-mouche and the "mafficker" may hereafter come within sight of the enemy, and for the first time realise his existence and their danger. But my view is that great towns like London and Edinburgh are to some extent protected against aerial bombardments by the inherent uselessness and inexpediency of such measures even from the German point of view. Great Powers like England and Germany do not make war on women and peaceful citizens. I do not think that it would profit the cause of Germany in the least to bombard London or Edinburgh from the air. Such an act would only infuriate our people, and make them ready for every sacrifice. If we heard that a Royal or a plebeian nursery, a crowd of peaceful clerks, or bevies of young women in the Telephone Exchanges, exasperating as they sometimes are, had suddenly been swept into eternity, the war would become one of extermination. Humanity aside, I do not think that it would pay Germany to provoke a war of that character with the British Empire. We shall be under the disagreeable necessity, in case of war with Germany, of temporarily incarcerating all German citizens in this country of a military age, that is to say, between the ages of 17 and 45. There is such a thing as the stern law of reprisals, and I hope that no enemy may ever impose it upon us.
Nor do I think that airships are ever likely to be used for the transport of troops for the invasion of our islands. So far as our experience goes, there seems to be no likelihood that the men, guns, ammunition, and stores, to say nothing of waggons and horses, required by an army destined for the invasion of the British Isles, will ever pass by way of the air.
But even if these two forms of attack be excluded, there remains, unfortunately, a sufficiently large sphere of activity for the airship to cause us much anxiety. First of all, reconnaissance. In favourable weather the German airships will begin their watch at sea during the period of tension, and they may be able to keep under frequent observation any ships of ours which enter the decisive maritime area within the Channel and the North Sea. The reports by wireless from the airships will permit the German naval forces to operate against any weaker detachments of ours within striking distance, and should render any attempt on our part to watch closely the German coast and ports a hazardous proceeding. It is certainly true that the weather conditions over the British Isles are frequently very unfavourable for airship work, and that affavit Deus may yet be struck upon another British medal. But we must also suppose that a Power which expects important results from airships will select a moment that is favourable for their activity and not the reverse.
I pass from the rôle of reconnaissance to that of attack. We must reckon with the fact that in favourable weather the dirigible soon will, if it cannot already, outstrip the fastest warship afloat. So long as the ship has no armament which will keep the airship at a respectful distance and this is the case with us at present there is no reason why the latter should not rain down projectiles on the deck and into the funnels of the ship until the supply of explosives is exhausted. So long as our warships are without this special armament they remain exposed to this form of attack, the future consequences of which will vary from year to year according to the forms which the projectiles of the hostile airship will hereafter take, the character of the contrivance for dropping or firing them, and the future types of armoured decks or steel pent-houses to resist these new attacks, if they can be resisted. As the airships increase in numbers and efficiency we must expect to see groups of them seek out our fleets at their anchorages and renew their depredations on a larger scale.
By hovering over our naval ports and establishments dirigibles can hope to play havoc with ships within the port, and with those completing for sea, building, or repairing. Cordite factories are sure to invite the particular attentions of the enemy. Flotilla bases where destroyers or submarines may be found will offer a specially attractive bait, for these light craft, secured as they often are in long lines near a quay, form a large and vulnerable target. The points open to attacks of this nature will constantly be increased as the range of hostile airships extends. Such attacks will be particularly dangerous at night when there is a moon, for it has been proved that it is very difficult to distinguish an airship by night, while the outlines of ships in the water can be seen plainly from above.
Every one who has watched fish from a bridge knows that it is possible to see a considerable distance into water directly below. Observers in airships will often be able to detect submarines and mines, to drop marks over the latter to guide mine-sweeping craft, and to attack submarines when these are either on the surface or near enough to the surface to use their periscopes. Dirigibles can safely approach within close range of submarines and make good practice with bombs or specially designed projectiles for use against these pests. The airship seems destined to play the part of the gull to the submarine fish, and offers at present the best hope of mitigating if not of ending the severe strain imposed upon a navy by the submarine menace. It is partly because Germany has such a large number of airships ready, while we have almost none, that I think she must hope to beat us in flotilla war. The airship has the faculty of approaching its objective, whether on sea or on land, rapidly and noiselessly. A few minutes after it is first observed it will be able to act. Nothing but other airships or special guns can check or delay its attack. It has all the moral force which attaches to novelty in war.
We cannot speak of the command of the air in the sense that we understand that of the sea. The command of the air, in its literal sense, seems destined to remain in the temple of the winds. Nevertheless, superiority in power to wage war in the air has become an imperative obligation for the State which desires to command at sea, and it is not improbable that in the near future the command of narrow waters may be decided in the air. Superiority in the air will enable a Power to act with knowledge against an enemy in the dark. It will, in favourable weather and narrow waters, discount largely superiority at sea. It will allow attacks to be made on hostile ships at sea and in port. By it alone, failing military action ashore, can a hostile fleet which takes refuge in defended harbours within airship range be attacked and perhaps destroyed. By it alone can the submarine menace be met and perhaps discounted.
If we reflect upon our preparations for figuring in these aerial combats, we shall probably agree that the creation of an Advisory Committee under Lord Rayleigh was a wise measure, for it is in experiment and research that we are so greatly behindhand. But we took another step which can less easily be defended, namely, the separation of our future airmen into two corps, one naval and the other military. The idea was that the rigid-frame dirigible was alone suited to the naval service, and other types of airships only to war on land. But is it quite so clear that the Army has not just as much need for distant reconnaissance as the Navy? and is it so certain that semi-rigid and non-rigid dirigibles and aeroplanes have no useful functions in a naval war? Many hard-headed people believe that the aeroplane will, without using her motors, eventually emulate the long-continued soaring flight of great birds. I think that we shall see parent ships for aeroplanes before long, very fast craft, with decks organised exclusively for launching aeroplanes, and with supplies of fuel, and all facilities for picking up aeroplanes on their return from scouting trips. In my idea, the aeroplane will impose itself upon the Navy.
I think that we are on the wrong tack in maintaining service distinctions in the domain of aerostation. The corps should be a single family, with a single aim, namely, the safe navigation of the air. We cannot count upon the same unity of doctrine and effort in two corps as we can in one. The division which we have imposed is artificial and arbitrary, for the air knows no coast nor ever will. All forms of aerial locomotion have much in common for instance, the study of air currents, motors, steering, observation, signals, and so forth. A single corps, neither of Army nor of Navy, but one which will serve both without distinction and form the missing-link between the services, is the real need of the times, and into such corps we should take steps to attract as many practical airmen as possible. It is also obvious that a technical school for the complete instruction of apprentices should be created with the least possible delay.
Airship and anti-airship artillery must also be constructed. Every warship that floats should have an anti-airship armament, and as the surface destroyer is gradually ousted by her swift submersible sister of 30 knots on the surface and 15 submerged, this type too will in the end be compelled in self-defence to adopt similar precautions. Anti-airship guns must be mounted at our naval ports and anchorages and round our factories of cordite and war material. It is necessary that the hostile airship should be attacked promptly and at extreme ranges directly she appears. Direct hits will be most difficult to obtain, but, as the mark will be large, and a single hit with flame-fire will mean the certain death of every one on board a dirigible which trusts to hydrogen, there will be much inducement to keep out of range, at all events by day, and to avoid the poised position, which means a "sitter" for the guns below. In principle it is in the air that the airship must be fought, but the speed and rapid action of the airship make the defensive value of aerial forces very problematical. The stroke will probably be delivered in most instances long before the airships of the defence are ready for action, so that we shall with difficulty escape the obligation of arming our ships, yards, and factories of warlike materials with anti-airship guns. As for the night attacks of airships I am unable to suggest any means of combating them, and I am very doubtful whether any such means will ever be found. The best preservative will be to get in our aerial blow upon the hostile navy first.
There is need for great vigilance and sustained effort. We are mainly dependent at present upon second-hand evidence of foreign experiments, and we shall never realise all that the airship can do in war until we have built and practically tested every form of airship of our own. If we can succeed, as I am convinced we can, given adequate financial provision, in building and in navigating a few score of serviceable dirigibles with a range of some 1500 miles, and capable of discharging projectiles which will wreck a ship if they hit her deck, we shall gain the inestimable advantage of being able to attack, and perhaps destroy, hostile fleets in their ports where our Navy cannot at present get at them. We shall in any case possess the power which we lack of attacking hostile submarines, and thereby of gaining the upper hand in the war of small craft which may determine the fate not only of Navies but of Empires.
The ideas which I have ventured to express in these two articles are no doubt but no more than the new arms themselves revolutionary and disturbing. They are without the sanction of war experience, because neither the submarine, nor the airship, nor the modern torpedo which is practically a new weapon, has yet figured in any war. But when new arms are introduced, and until we have the test of war to approve or condemn them, we are reduced to speculation concerning their future use. In the conflict of ideas arising from free discussion some sparks of light occasionally flash forth.
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