by R. L. Barkley & F. D. Buckley,
PROCEEDINGS, March 1943, V.69
The use of the rigid airship as an aircraft carrier will require much larger volumes than have been heretofore constructed. Volumes of approximately 20,000,000 cubic feet-three times those of the Hindenburg and Akron types-are necessary to the development of efficient carriers. Such volumetric increase does not introduce any new structural or operational difficulties. It perhaps does introduce some terrifying misgivings where there is a lack of imagination. In reassurance, it is pointed out that the Hindenburg had a volume three times greater than that of the standard World War airship, which in turn was three times larger than the pre-war commercial types. According to the Hindenburg’s operators, she was far easier to operate than any previous type. As to size, such an airship would require a dimensional increase of about 50 per cent as compared to the Hindenburg, i.e., a length of 1,200 feet (Hindenburg 803 feet) and diameter of 200 feet (Hindenburg 133 feet).
The standard gross lift of such an airship (100 per cent pure hydrogen at 32°F. 29.”92 hg) would be 750 short tons. Of this, 300 tons would comprise the structural dead weight of the airship (allowing 40 per cent dead-weight tonnage). A useful load of 400 tons would be available assuming normal operating conditions of 60°F. 29.”92 hg, with 98 per cent pure hydrogen. A fuel load of 150 tons would drive the airship some 12,000 nautical miles in still air. It could carry and operate 50 planes averaging 3 tons each, leaving 100 tons for aircraft fuel, bombs, etc., less the weight of the airship and aircraft crews (about 200 men) and their necessary equipment. The above estimate of performance presumes a static equilibrium take-off. Such an airship could carry (operating “heavy”) at least 5 per cent of its standard gross lift dynamically after take-off-about 40 tons in this case, and operate in that condition indefinitely. A maximum of 10 per cent of the standard gross lift can be carried dynamically for periods of a few hours. This overloading can be done by taking extra weight aboard in flight such as by fueling from another airship or landing additional aircraft. Under nearly all operating conditions a useful load of 400 tons would be available. A top speed of at least 80 knots could be expected from such an airship.
The elimination of heavy retractable landing gear installation on attached aircraft would contribute materially to the increase of their useful load. It is also probable that larger and heavier types than can be operated from surface carriers could be operated from airships.
Perhaps the greatest single advantage of the airship carrier is its adaptability to mass production. The delivery during World War I by the Zeppelin Co. of one 2,000,000-cubic foot airship every two weeks, utilizing three construction hangars, has already been pointed out. Achieving the same rate of production of airships ten times that volume demands only more facilities and men. With a dozen erection hangars in operation, the delivery of one airship carrier every four days could be realized. We have again become accustomed to rates of delivery which in normal times are startling-some of them even in view of the rather remarkable achievements of 1917-18. Shipbuilder Henry Kaiser’s recent statement that a man who knows one end of a wrench from the other can earn 95 cents per hour, that one who doesn’t will have the ends labeled for him, is typical of the daring and aggressive spirit with which the problem of mass production must be attacked. So it is with airships, in spite of the fact that a Congressional committee was recently advised that from 2 to 3 years would be required to construct a rigid airship. The German record of airship mass production need not be obscured; it is still a fact, and the possibility of improving upon it most certainly exists.
The speed and range of the airship carrier, coupled with its availability in large numbers, would make the concentration of aircraft when and where they are needed a much simpler problem than it is today. It would provide mobile bases for aircraft types which have been found to be the most effective at sea (i.e., dive bombers and torpedo planes) for much less expenditure of time, labor, and material than a similar concentration effected by surface carriers. It could and should have its construction centers located well inland, both as a defensive measure and to make use of labor which is not available to coastal shipyards. Should the airship be found only equal to the surface carrier as a base for aircraft, more attention could be diverted to the vital problem of producing cargo bottoms. It consumes some 300 tons of material as compared to 20,000 tons for a surface carrier. It is true that the material required is vitally needed in other war industries, but the development of a new and efficient aircraft carrier would most certainly establish the desirability of favoring it with a high priority classification.
The greatest objection to be held against such a proposal will be the alleged vulnerability of the airship. This criticism will become sharper as soon as it is thoroughly understood that the airship demands hydrogen to ensure continuous availability.
It is quite generally recognized in military circles that all weapons are vulnerable to countermeasures. It is also recognized that the vulnerability of any weapon is a function of the application of employment technique. It has been pointed out that the bombing Zeppelins of World War I defended themselves by making use of their great rate of climb and high operating altitude. The airship carrier will have to do practically all its operating at relatively low altitudes. Since it is acting as a transport medium rather than as a weapon itself, it must remain in the denser air of the lower altitudes in order to maintain its lift at the maximum possible value. Its defense lies in its ability to remain at a great horizontal distance from areas which are a source of danger to it. The high performance of its aircraft as compared to carrier-based types, and its relatively high speed combine to enable it to avoid attack more easily than can the surface carrier. It fears no reefs or rocks nor does it leave a betraying wake or oil slick hours behind. In an hour it moves 80 miles. In addition, it is vulnerable only to air attack, unless it should be brought by error within the range of anti-aircraft fire.
The loss of a carrier airship would involve the loss of not more than 200 men. The airship is very inexpensive with regard to the number of personnel involved to operate a given number of aircraft. The operating personnel of airships can be easily and rapidly trained. The personnel investment of a surface aircraft carrier is relatively tremendous, requiring not only personnel for the carrier but the immobilization of other units and their personnel to provide escort facilities. These units can always be advantageously employed otherwise. The greater problem is the development of proper tactical employment of the airship carrier. For this reason its operation must be constantly dominated by line aviation personnel.
The relative vulnerability of hydrogen and helium airships is an academic matter. If either were directly subject to air attack, loss would be certain. It is quite true that a single incendiary bullet can cause the loss of a hydrogen airship, but it is just as certain that if an incendiary does not cause the loss of a helium airship, means are available to do it, and would be brought into immediate action. The employment of contact bombs or explosive bullets would suffice. Special acid loaded bombs or bullets would be developed. The destruction of the airship’s lift by whatever means employed would achieve the desired result. The problem is, therefore, to avoid contact.
Contrary to press conceived belief, we do not possess sufficient helium to operate a fleet of airship carriers. According to figures released in the Army and Navy Journal of September 6, 1941, 57,000,000 cubic feet per year of helium would be required by 1944, upon completion of the 48 nonrigid airships then authorized. Authorization was being requested to bring the yearly output of helium up to 60,000,000 cubic feet. Since that time, a total of 200 blimps has been authorized by Congress. So it would not be too surprising to see even the nonrigid shift to hydrogen, assuming of course that they are delivered on time. Basing an estimate on the rather limited peace-time operation of the Akron and Macon, 60,000,000 cubic . feet per year would not suffice to operate two 20,000,000-cubic foot airship carriers. It should be noted that this hypothesis does not consider the important problem of transporting helium to airship operating bases. Scarcity of ship bottoms to transport helium, when other commodities are more urgently required, would seriously hinder the operation of airships. In railroad parlance, some 100 carloads would be required to provide initial inflation for one 20,000,000 cubic footer.
The relative lift values of helium and hydrogen are frequently misunderstood primarily because they have been frequently misrepresented. Helium, at standard conditions (100 per cent purity, 29.”92 hg, 32°F.) has 93 per cent the lift of hydrogen. In practical operation, because helium is never available at a purity greater than 97 per cent, and because of operational considerations which result in a further lowering of purity of helium relative to that of hydrogen, the lift difference is rarely less than 10 per cent. As the temperature of the air mass in which the airship operates increases, a further disparity is introduced which increases the lift advantage of hydrogen. To the 20,000,000- cubic foot aircraft carrier, structural weight and fuel load (range) remaining constant, substitution of helium means a reduction of the military load from 250 tons to 175 tons-a loss of 30 per cent. It is quite conceivable that the additional 75 tons carried by the hydrogen airship, disposed in additional aircraft, armament, or bombs, could easily mean the difference between accomplishment and failure of a mission, or even the difference between saving and losing the airship itself.
It is of interest to note here that the refusal of helium to Germany in 1938, while it resulted in the abandonment of commercial airship service, did not prevent the operation of LZ-130 (Graf Zeppelin II) for the training of new airship crews. Prior to the German attack on Russia, LZ-130 had been persistently reported in operation, carrying war materials from Russia into Germany. Even this relatively small commercial airship (same volume as Hindenburg-7,000,000 cubic feet) with range reduced to 2,000 miles, could carry better than 75 tons of payload.
During the spring of 1937, experiments were carried out involving the operation of aircraft from the Hindenburg. It was stated that mail service was to be speeded up by putting mail aboard after take-off and flying it in ahead of the airship’s arrival. Passengers were to be picked up and discharged at London by plane instead of having to go all the way to the Frankfort terminus. It is of particular interest that the plane pilot who made the tests was the late German air force general, Ernst Udet, to whom a large measure of credit is given for the organization and tactics of the Luftwaffe as well as those of the parachute troops. Although press releases and photograph captions at the time stated that Udet was the pilot, conflicting stories were told after the loss of the Hindenburg as to the results of the test-in one case a flat denial that they had ever been carried out was given to a United States naval officer. Press photographs showed that the apparatus used was practically identical to our own, except that the trapeze bar was located considerably closer to the hull of the airship. The peculiar circumstances surrounding the test give indications that it was carried out to determine the military value of the airplane-airship combination. Should Germany find herself able, through possible defeat of Russia, for instance, to operate airships from relatively attack free bases, the airship carrier might provide means for effective attack against our industrialized east coast. The possibility should also be considered that Japan might find the combination useful to multiply her offensive naval aviation power in the Pacific and to permit attack on west coast production facilities. Japan, in cabling her regrets over our loss of the Macon, stated that she would like to investigate the usefulness of the naval airship. It is conceded that the above is largely conjecture, but it is well not to disregard it lest the airship carrier burst suddenly upon us with harsh reality. We are well aware that the Axis powers quite capably employ offensive aviation. We should become aware, if we are not already, that among them they possess the ability to operate and mass produce airships, and the willingness to expend them in large numbers, should that be necessary, to enable aviation based thereon to achieve the desired results. The problem of training plane pilots to operate from airships is quite simple, as we have found from our own experience.
During the first World War, German airships were operated exclusively from hangars. The operations of docking, undocking, and ground handling were accomplished entirely by man power. It has been previously pointed out that all but two of the German naval airships were immobilized in their operating hangars during the first day of the Battle of Jutland, and that these two were in a rotating hangar. One of the major handicaps of airship operation was thus brightly illuminated. It is surprising that the Germans took no steps to find a solution to the problem.
Similar difficulties were recognized during the operation of British anti-submarine patrol nonrigids, and a report from our Scientific Naval Attaché dated April 24, 1918, to the Chief of Naval Operations recommended that the best thought and effort be directed toward developing mooring out facilities in order to increase the service availability of patrol blimps. Today, however, a satisfactory solution remains to be developed, with the result that hangar space is still required for each and every blimp constructed. It can readily be appreciated that the difficulty of constructing operating hangars is one of the major factors responsible for the slow delivery of anti-submarine patrol blimps, which was noted in Time magazine for June 1, 1942. The situation is typical of many produced by post-war apathy towards military development.
During our operation of rigid airships, more strenuous efforts were made to overcome these difficulties. A mooring system with a great degree of reliability enabled our airships to operate for extended periods without relying upon hangar facilities. Elaborate mechanical equipment for docking and undocking was also developed, but demonstrated conclusively that an airship would always be immobilized by strong winds if forced to operate from a hangar. German commercial operators were sufficiently impressed to copy the essential features of our mooring system, which they used with great success.
The implications to be drawn from the above are quite clear: the hangar must be used only for the construction and extensive overhaul of airships. All operation must be carried out from mast bases, to assure the constant availability of the airship and the aircraft based thereon. An airship immobilized in a hangar is helpless against attack, which fact was demonstrated to the German operators during the first World War. Apparently the lesson did not penetrate.
To date, the numbers of aircraft taking part in action at sea have been small compared to those used in land operations. The primary reason for this is that there are relatively few aircraft carriers in existence. The very nature of the aircraft carrier makes it difficult to produce and replace. Hybrid conversions are being used-and should be-to augment the strength of our primary offensive power at sea, but many of these are bound to be disappointing from the standpoint of results obtained. The insufficiency of carriers seriously hampers the sea-keeping qualities of naval aircraft. Press releases have indicated that many cripples, which could have been polished off by aircraft-or fast battleships for that matter-escaped from the Battle of Midway. Sufficient aircraft of suitable types could have followed and annihilated these units, preventing their future use against us. Airship-based aircraft could have been gainfully employed here. To pursue and annihilate these forces-without the danger of being ambushed by enemy submarines. The construction of sufficient surface craft, particularly battleships, to accomplish such a task requires a formidable investment in material, time, labor, and personnel. In addition, such means are vulnerable to all the weapons of sea warfare, whereas the airship is vulnerable only to aircraft attacks. The adaptability of aircraft to mass production assures us relatively easy attainment of decisive superiority, and the rigid airship can provide basing facilities for these aircraft.
So far, results seem to indicate that the relatively short-range, carrier-based dive bombers and torpedo planes have a greater effectiveness than the long-range horizontal bomber in fulfilling the precise requirements of sea warfare. The long-range bomber is at its best employed over stationary land targets, or in the area-bombing operations now being conducted in Europe.
We must concede that the naval operations to date have been on a small scale insofar as the number of aircraft employed is concerned. Future actions will undoubtedly involve numbers greater by many times-even considering only the employment of surface carriers. But we must wait until these carriers are available before we can employ them. We have time, therefore, to undertake the development of the airship carrier. Assuming that we can equal the German rate of airship production, utilizing 12 erection hangars instead of 3, 90 airships per year could be produced, basing 4,500 aircraft averaging 3 tons each; or 2,700 averaging 5 tons each. The possibility is rather striking, but it is there nonetheless.
The fundamental concepts of sea power have not changed. The bulk of all goods and personnel necessary to the conduct of war will be transported by sea. The establishment of offensive bases, involving the so-called amphibious warfare, demands local sea control. It is not the basic concepts which have changed, but the new tools used and the means of applying them. Germany, in the older sense of the term, is not a sea power. But any military power which takes such a terrific toll of shipping, regardless of the means employed, must be considered a sea power of the highest order. The new conditions forced upon us demand a new course of action. The ponderousness of naval equipment makes its alteration to meet new conditions extremely difficult. Much of our old equipment has been made nearly useless by the new conditions under which it must fight. Insofar as possible all new equipment must be capable of adaptation to new conditions.
It is certain that aviation will remain the primary striking force at sea for some time to come, perhaps for all time. It is not necessary or desirable to introduce the additional complication of a separate air force. But a perfect liaison is necessary, and ours has improved vastly since the outbreak of the war. A clear picture of the general situation involved is the first essential-the second is the proper employment and correlation of all the offensive power at hand. How the organization is constructed is of no consequence if these two basic essentials are complied with.
As to the part the airship can play, the old conception which previously governed its development must be immediately junked. It is not a negative scout or a patrol vessel. Its aircraft do not exist only to augment its ability to scout. It is merely transportation for an offensive force of aviation, which it serves as an auxiliary with all that may imply.
The misconceptions, previously outlined, which have been permitted to arrest its development must be strenuously overridden if they continue to suppress progress, whatever their source. In the future, responsibility for operational failure must be definitely placed. Placing it on the mute airship can only frustrate the attainment of the desired development. DuPlessis, the French naval airship operator, summarized this responsibility neatly: “If, in this nice little game all responsibility evaporates, all activity is also.- destroyed and there is no equipment able to survive such a regime.” While it is quite true that the alleged difficulties of construction and operation have discouraged public opinion and to some extent naval opinion, the primary objection to the airship from a military viewpoint comes from its failure to deliver the goods when the opportunity was available. Even so, definite possibilities were indicated by the operation of the Macon.
As to construction, competition between at least two companies should be encouraged and subsidized. The competition of the smaller Schutte-Lanz airship organization was one of the major factors in the effective development of the Zeppelin airship. Contracting for the first 27 of the 48 originally authorized blimps from one company has been a second factor responsible for their slow rate of delivery. The Army, in ordering barrage balloons, contracted with at least five different companies, at greater cost perhaps, but the production has been gratifying. A blimp is, after all, nothing more than an enlarged barrage balloon provided with power and control facilities. If necessary, the Navy might provide competition by entering upon the construction of rigid airships itself, as it did in the case of the Shenandoah. The airship is not such a mysterious construction problem that it requires the monopolized services of a single, highly specialized construction company.
Nor does it require a monopoly of highly specialized operators possessing superskill. Press contention notwithstanding, the past history of airship operation amply confirms this fact. The responsibility for development falls squarely upon the shoulders of those whom it would serve as an auxiliary-the naval aviation organization and the naval service at large for which it provides extension of an already powerful striking arm. It must be developed and operated in exactly the same manner and by the same forces as the aircraft carrier. It is the responsibility of the Navy in general and of naval aviation in particular. The possibility exists of developing an auxiliary which can multiply many times the strength and sea-keeping qualities of our primary naval offensive weapon. We would be unwise to ignore it. In closing, we refer again to the writings of DuPlessis who attempted “to draw attention to questions too long neglected and to provoke their solutions rather than furnish them.”
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