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Produced by the NASA Center for Aerospace Information (CASI) N -^ q ^ `76 7 (NA6A-TK b4-744) cuiRLNT UEVELUICHENTS i,.L';.t TER IRAN Alit )Yb'ltKS Wllti011a A+L.L'Uttcltlt]C:ca 3tt :ii'uC c Add l.11il ;tL'dt].bI1) ^J c: SC: r, 0^n ux^c]^'.`^^ HC A0z/ril At? l ^t\, ]] ] ]

CURRENT DEVELOPMENTS LIGHTER THAN AI R SYSTEMS

UNITED NATIONS INDUSTRIAL DEVELOPMENT ORGANIZATION CONFERENCE ON LTA SYSTEMS TECHNOLOGY FOR

ire-r,- nr nr1 r_ t nn r klr rn11AITD Y CC THE Bti NEE t ur DEVE OP NG W1 1-1 1,1 1 n At

VIENNA, AUSTRIA 19-22 OCTOBER, 1981

NORMAN Js MAYER aq^^o

PROGRAM MANAGER AND CONSULTA`y/ VA SYSTEMS ii NATIONAL AERONAUT,ICG AND SPACE ADMINISTRATION WASHINGTON, D,C,

.r 1 CUIlUNT LTA TECHNOLOGY DEVELOPMENTS Norman J, Mayer NASA He adqunrtesrs Washington, D.C.

&12rack Lighter-than-air aircraft '%LTA) Transportation in nations of the third developments and research in the United world constitutes a great potential for States and other countries are reviewed. advanced aircraft development which could The emphasis in the U.S, is on VTOL air- provides capability to bypass some of the ships capable of heavy lift, and on long evolutionary development of surface infra- endurance types for coastal maritime pa- structure which is often non-existent and tiol.Design concepts include hybrids difficult and expensive to develop. which combine heavier-than-air and LTA components and characteristics. Research A further incentive is produced by the programs are concentrated on acrodynamica, increased awareness of all nations to con- flight dynamic.;. irtod control of hybrid serve marine resources with the consequent types. establishment of extensive off-shore zones of protection which require new surveillance capability. 111-t., 12.91 t an These now applications have created In the interval between the termina- requirements for airships with character- tion of U.S. Navy airship operations in istics considerably changed as compared to 1962, to about: the middle of the 1970 past designs. These include VTOL capa- decade, the field of lighter-than-air bility under a variety of conditions, long aircraft (LTA) engineering and develop- period hovering, and in some cases higher ment was in a dormant state. The only con- speeds. Such capabilities may not be tinuity during that period was provided by available without the combining of LTA and flight operations with modified World War HTA (heavier-than-air aircraft) features. 11 type training airships by private firms These hybrid concepts will require the in the U.S. and West Germany. development of basic aerodynamic data, better understanding of their flight dynamics, and other new technology. A renaissance of sorts is now occur- iing in which there is world-wide inter- in the following descriptions of est in LTA, evidenced by several 4lovern- current developments, the various aspects ment and privately sponsored studies and of this relationship between now tech- some actual aircraft development. Several nology and aircraft developments will be stimuli have served to create this new emphasized. In this review, various air- attention to an old subject. perhaps the ship types will be described using an es- most important is the potential for new tablished method of referring to their transport capability in a world of chan- structural systems. This method has been ging requirements. These have emanated used with classical airships, as shown from the increasing demands ror heavy- on the left side of Figure 1, but it can lift caused by development of onergy re- also be applied to the newer configura- lated resources in remote areab, harves- tions shown on the right. ting of timber from relatively i.nacessi- M e locations, and by grov , th associated with industrial development. current Developments A second stimulus is the need for Aircraft Developments gvvater transport efficiency through elimination of inter-modal operations, United States - Two major programs, reduced terminal time, and higher fuel focused on different objectives are economy. Such demands in the past led to currently underway. One is the develop- Lbe development of containerized cargoes ment of heavy-lift hybrid airships and and new surface ship development - point- the other is the evaluation of airships ing the way to aerial systems to handle for maritime surveillance. larder sized payloads. Interest in the heavy-lift application was generated around a concept by Frank Piasecki of the Piasecki Aircraft Corp. for combining helicopters and aerostat

ORIGINAL PACC 615 OF POcR QUALM

TYPES OF LIGHTER•THAWAIR AIRCRAF=T AEROSTATS HYBRIDS

BALLOONS "; •^

FREE TETHERED LENTICULAR RIGID

^RIGID

^l" lsoLES SEMI-RIGID

AIRSHIPS PRESSURE NON-RIGID

m HEAVY-LIFT NON-RIGID METALCLAD

rig. 1

2 t` ORICINAL Or voml ^^RI^^.E hulls, tea obtain large vc.; t reveal lift capa- could be compatible: with Coast Guard opera- bility beyond preoent helicopter capaci- tions and would show improved capability ties up to an order of magnitude increase. over certain air and surface units now in This concept appeared to be a fortuitous use. A comparative plot is shown in Fig, 4. solution to a current military problem of For the cases soleeti.d, it was determined off-loading cargo vessels in parts where that airships could cowl-leto from 80-100 facilities do not exist or have been des- percent of the missions at oost.s equal to troyed. Various hybrid types and oombina- the HC-130 airplane and at 50-60 percent tions were studs ,.d by the Goodyear Aero- of the cost of ship operations. In 1980, space Corp. us•oor NASA sponsorship (Ref. 1) NASA entered into a joint agreement with (and lat°ot, independently). The most recent the Coast Guard to also assist in the proposed Goodyear configuration includes assessment of airships and to develop rotors and drive components modified from necessary related technology. Current R&D current helicopters, forward and reverse plans call for the procurement and opera- propellers for horizontal propulsion and a tion of an airship to engage in various 75050 m 3 envelope with a payload of Coast Guard missions. The extent of mission 68 tonnes. (Fig. 2) operation would be limited by the size' and performance of the airship which in all Although an operational requirement likelihood will be of smaller scale than was written by the Navy for, a heavy-lift one required for full mission operation. hybrid (Ref. 2), no program for develop- The flight program would include both mcnt was authorized. NASA has continued to operations with and independent from sur- explore the dynamics and control character- face craft to demonstrate hovering, detec- istics of the concept. however, (described tion and surveillance, air-sea rescue and under technology development), and a study other missions,. This program will be con- was sponsored to explore the potential ducted by the Navy. market for the type which included several concepts and configurations (Ref. 3). A few private efforts involving airship This study indicated that a substantial development also exist in addition to number of applications do exist. for heavy government sponsored programs,. One of vertical lift vehicles of various sizes. these, by D.C. Associatio n in Delaware, is These results are summarized in Table 1. described under Canadian programs. It can be seen that a leading application is in aerial logging. CAA a dEk - Several events in Canada have resulted from recent growth and development The Piasecki Corp. has also continued of the Northwest territories and some of to study various combinations of heli- the Western provinces. Studies sponsored copters and aerostats and has participated by the Ministry of Transportation identi- in several NASA and Navy sponsored studies fied several types of modern airships which to evaluate various aspects of the concept. might be suitable for transport systems in In 1980, the U.S. For,_:;t Service awarded this area (Ref. 5). Economic analyses in a contract, to be administered by the Navy, this study indicated that enormous savings to Piasecki for the development and opera- in transport expense were possible through tion of a Heli-stat for a demonstration the use of some kind of heavy-lift VTOL of aerial logging of Federal forests in the aircraft. These savings would accrue from U.S. Northwest. This vehicle is shown in the elimination of road construction - and Fig. 3. It will utilize a large number of reconstruction due to weather effects, component.; from Navy spare aircraft. The elimination of time dela;. by by-passing major components are four H•-34 helicopters obstructions (rivers, cantons) direct anti a 27611 m 3 Zm_ , Navy ci1r. hip delivery of men and equipMLnt, and exten- r?nve?lope. The helicopters will be modified sion of the working season. to ac:.comodate forward and reverse thrust propellers. This hybrid will lift a nominal The lagging of timber in these North- 25 tons of payload. It is be,nq constructed western regions is also an attractive use at the Naval Air Engineering Center at of heavy-lift hybrid airships. One type Lakehurut, N.J., and is scheduled for being developed for such use is the Cyclo- delivery in May, 1982. crane, a patented concept of D.C. Associ- ates. This vehicle is a unique combination Since 19'1 6, the U.S. Coast Guard has of rotorcraft and aerostat. It consists of been entlaged in an investi.► ation of var- an ellipsoidal non-rigid aerostat hull ious methods of implementing their re- supporting 4 rotor wings radially from quirc.naents and responsibilities resulting points along its maximum diameter. The from the Fishery Conservation and Managc- wings are equipped with tip airfoils and ment. Act which established a 200 mile zone propellers. The entire hull and wing sys- outward from most U.F. coasts covering an tem rotate, driven by the propellers such area of 2.2 million square miles. Added to that control and propulsion forces are the .0 nveds were problems caused by illegal developed by wing system regardless of ii,ara.timc traffic. 'rho U.S. Navy has been forward speed. A 1.8 tonne 9487 m3 assisting in stud-e: of a number of types demonstration model is being purchased by and sizes of airships which might be suit- Canadian Forest Products Industries, a ablo for Coast Guard missions (Ref. 4). private group. It will be tested in These studies indicated that airships Tillamook, Oregon and later operated in

W011LQ MARKUS FOR HEAVY-LIFT AIRSHIPS

NumtAf1 A1113N110b' A$ I II ICA]i')M Of PAYLOAD Ih0 X00 ^I10 LMGING ION2 600 MAf1111MF LAGISTH 5 27 t0 P( IIIOII UM ORR LING b InANSPIiiiI I.OWFR PLANT t POWER q 1 S 1 I LINE GOWiTRUC1 ON 1RANSPOIII ATION

TOTAL 112' A11 1 'ASSUMI S MR) 14P ivN UI11 IIAI WIo

Table 1.

i'rodu I ion curifiyi,: im. - 11, ,,vy -Lift Ail 1p

HELISTAT GENERAL ARRANGEMENT

ORIMNAL PAGE BLACK AND V.-INI i c RiOTOCRAPN

4 the Canadian province of Vancouver. both short and long ranee operation. Two Flights will begin in the summer of 1981. major stockholders in the company are A scale model used for research is shown freight transport companies and they are in cis, 5. Continued interest exists in interested in the potential which such air- Canada to sponsor home industrieu needed ships offer for fast lower coat service. to implement development of xosourcos, Much o^ this economy is expected to result etc. 'Phis could lead to the cotablis)unent from use of natural yon :gin a primary fuel. of companies in Canada to build and oper- Studies are continuing i,u this concept and ate airships. no specific design as yet has evolved. It is anticipated that the final design will Grcaat Britain - Interest in LTA in Great have an e:,lipsoidal hull shape rather than Britain has never ceased, although Govern- lenticular^ as originally planned although ment sponsorship of any work has. As a some model testing continues on the latter consequence, limited private interacts type as well, have been confined largely to studies of various concepts or to small experimental Airship Industries has tentative or- airship projects. In recent years, one ders for 500 and 600 series airships for firm, Aerospace Development; (later called training, patrol, one. advertising, and Airship Developments), combined their own interest is being shown in the larger design engineering capabilities with those non-riclid and rigid type as freight trans- available from specialized contractors to ports. produce a small non-rigid with several advanced features, designated tho AD-500 Welt_ Germany - As in Great Britain, activi- (Fig,6). All components were fabricated ties in Germany are privately sponsored. by separate manufacturersin England, Tho most active company, West Deutsche France, and Germany, with final assembly Lufterwerbung GmbH (WDL), has been opera- of the airship provided by Aerospace ti„g two non-rigid airships in Germany and Developments. This airship was wrecked Japan for aerial advertising. These air- following its second flight during ground craft are modified versions of Goodyear handling. "L” types, the design of which predatea WWII. However, several new features lrave Another organization, SXyships, later been incorporated to the Iml, modzf!,citionu. . known as Thermo-Skyshipa experimented with These include fuel tans icv nded by the lenticular shaped vehicles in scale model internal car suspension calileo within a form. Recently Thermo-Skyships and Air- center ballonet, improved air pressure ship Developments merged to form Airship systems, :slightly larger envolopas (6,000 industries, Ltd. Their plans includo two m , ), and tractor propellers. As of March, major objectives. The prime ont, is in the 1981, the two airships were being over- building of several sizes of non-rigid air- hauled and scheduled to commence flight L3hips beginning with an improved version of operations in April and May. the AD-500 now known as Skyship 500. This ,)132 111 3 airship will include a re- WDL has also completed a preliminary design designed control system, mooring system, study of a larger non-rigid, the WDL III and envelope. The control system will em- (60,000 n1 3 ), which would feature diesel ploy optical fibers to transmit. control engines locateer within the envelope, vec- signals to actuators located ;it the . control toring turbines for maneuvering control, surfaces. The mooring system hers been and removable cargo and passenger modules. strengthened to withstand hioLor forces, Specific development plans 1• ave not been end the envelope is designed for improved made for this airs'aip. gas retention. The new 500 1.3 ueheduled to make its first L.iglit durinq the summot The name of Luftsebi£ibau zeppelin has been of 1981. restored as an active mart of zeppelin Metalwerke, GmbH in order to respond to the A iltretc ho>d versior, of the 500 is also continuing interest for historical ma- under development. This is designated Sky- terials and information, and to remain cur- :;hip 000. It will contain a 6 meter para- rent on new developments. No plans have 11el middle body providing an additional been announced to resume airship construc- O.n tonnes or lift. 'rhea ear will also be t on activities, however. ::trotchcd 2.5 meI tors and will be equipped with 2 supurcharged Porreho. 250 H.1'. Prance - Various goveznment and private or- engrnea driving two t>_ltinq ducted fans ganizations in France have sponsored stu- (a y in the 500). This power will allow dies of airship applications and airship a top spored of 65 knot„, with a vortical concepts. Two agencies in particular, ONERA lift--riff capability ups to 1', OU kg. and SNIAS have investigated hybrid aircraft some of which are similar to concepts pro- The company is al,30 contempletinq a posed in the U.S. involving helicopter- Larder non-rigid, designated Skyship 5,000 aerostat combinations. One of these, called of 424HO 11,3 crnvc lope vo1u.,,c. the HELICOSTAT, featured a tri-lobed non- rigid envelope and 2 Turbomeca Arriel tur- Another, somewhat separate objective bines driving AS350 Ecureil rotors to pro- is in the design and construction of large vide forward and reverse thrust. if the metalclad airships (approx. 127400 m3 aircraft had been built it was to have been ft.) to be used as freight transports for used to demonstrate aerial logging,

ORIG►MA - ^'ra ^: `'' OF POOR VINL11"A ORIGIN-Al- ^;'.CF 19 OF PMR QUALITY

FFFECTIVtNtSS OF AIPSHIPS COMPANtO WITH OTHER COAST GUARD CRAFT

t " "I c

OMf TOTAL l t1 ,04A 1 Uy1 . ` ,.I I t COSTS IM H 1 %bK)k 1• t ! 000' p elIA AH •", I.Mt VITA

^ !0

Hrt IaI

ArHVI Aq1

h'i(a, S. CYCLOCRAN Plying Model

t) . AV-`.,00 Airship

.. OF po ^3 QUALITY however, no construction is planned at studios involving dirigible transport bu: prenont. (Ref. 6) no results have been reported.

The name envelope concept wan used in Several South American nations have an experimental RPV designated DINOSAURE. similar problems regarding development and In this 40 cubic meter mini-airship, 2 transport. Those involve resources in re- enveloped were joined to form a lifting mote areas requiring the transport of body shape. Other features included blown heavy equipment and limited by effec"M of controls and an air cushion landing system. seasonal weather. In a way, these are nimi- The model shown in Fig. 7 was used for lar to some of the Canadian Northwest pro- atmospheric research and com pleted 70 blems of development where terrain is not flights (Ref. 6). hospitable to road or rail construction and working periods are limited by accessi• A French engineer, M. Balascovic, has bility. All of these tend to establish been experimenting with lenticular shaped requirements for an aircraft capable of hulls and has proposed several versions heavy-lift, VTOL flight, and one requiring named Pagano, Titan, and Vespa. A single a minimum of around facilities, such as plane flight vehicle, "Flipper", was con- the heavy-lift hybrids. structed in 1978 to provide early date. (Ru£. 6) Unfortunately, the aircraft was Agr,ica - A limited demonstration of air- damaged beyond repair prior to its first ship operations was carried out by the ilight. Pr000nt plans by Baiascovic and Germs„ firm, WDL, under government spon- his company 11.E.A.B. include development sorship, in Ghana and Upper Volta, using of a 6,200 cubic meter airship called a WDL-I non-rigid. The airship was shipped ALCYON. A model of this aircraft is shown to Ghana and erected (in the open) at the in Fig, 8. It is intended as a low alti- airport. Conclusions on the results of tude VTOL vehicle. Vertical thrust is ob- these experiments were not publicized. It tained from 3 rotor systems located at is understood, however, that interest in 1200 points on the hull perimeter, For- developing an air transport system suit- ward thrust is provided by 3 propulsive able to the requirements of terrain and units mounted on the tail support struc- developments is continuinq in several W. ture of the aircraft. Although the vehicle African nations. has a large horizontal tail, it was judged co be inherently stable (in pitch) without II - Technoingv__Aevelonmente this appendage on the basis an analysis provided by CERT (the Toulouse branch of Configurations - In several countries, ONERA). Wind tunnel tests to measure drag departures from the normal hull forms were also run by ONERA. A full scale of ellipsoids and cylinders continue to be vehicle is planned for completion in 1982. studied. These concepts have boon con- sidered for a number of reasons such as a ,7anan - The Japanobe Ministry of Inter- desire for increased dynamic lift in national Trade and Industry (MITI) has flight, reduced resistance to ground winds sponsored studies to identify missions in while moored, or the need for a special which modern airships may be usuful. Many hull form because of payload or mission of these included the transport of electric requirements. Configurations include delta power generating equipment to various rela- planforms, lenticular shapes, and ellip- tively unaccessible location., in the soidal cross sections. Japan(-se Islands. others included supplying populations located on the many small Objective evaluations of these con- islands of the Japanese nation. Favorable c9pts in comparison with conventional results were shownin terms of the in- types is difficult because of the lack of direct costs which would be eliminated an adequate data base (for the new con- through the use of airships uch as road cepts) and also because requirements for construction, airport runways, bridges, each type may not allow direct comparioons. ote. The studies also identified a heavy- One such evaluation (Ref, 8) was made re- lift type of hybrid carrying between cently on the basis of specific: produc- 20-1.00 tonneu of payload. Following thr.,. tivity for deltoid hybrids and conven- study, a program of development was re- tional equilibrium types. (Spec. Produc- commended, but it has not been implemented tivity w Productivity/Airframe Weight & to date. (Ref. 7) Propulsive Weight). The results show that bull forms of very low aspect ratio Scljath_ nmc'ri,_a - There has bran sporadic (e-J 0.5) nave slightly higher values (of interest on the part of aeveral countries specific productivity) than conventional in South America. The most serious effort shapes. These hulls would actually combine wa:c unrJortaken by a Venezuelan firm in ellipsoidal fore bodies with flattened financing the development of the Aerospace (delta shaped) afterbodies. These results Developments Ltd. An500 airship in the seem to have been confirmed in an indepen- U.K. as a public relations and advertisincl dent study (Ref. 9) which compared very project. The late Cori. 9tion and later large VTOL nybrids and equilibrium types accident of the airsh^ 4, forced discontinu- for military airlift missions involving ation of this connection. very long range flight. Fig. 9 illustrates the results of these investigations. The government of Brazil has conducted 1

DI NOSAI , M i n i fit''

i J. 9 ,%I,CYON Model

^ I^1

1 1^

rrutluct . ty Comparisons 8

r.. _ ,./mot

SLACF i OCr,A 7 tf f ^/ r r,1 01110dM ,,v li \+t^,, pJ

It should be noted that the produc- Another approach to the study of Clight tivity valued arc low compared to air- characteristics is being employed by the planes at their best ranges, but possible Naval Air Development Center. This consists features ouch as VTOL capability, large of a remotecon rol flyin, ►nodal 9.75 m single payload and volume capacity, and long and 24.5 m in volu,,ne. It will the potential for extreme range flight approximate a 1/10 Scala version of a could make some hybrids attractive for Coast Guard patrol vehicle concept, and future development,. will incorporate a tilting bi-rotor propulsion and control system. pvnomlcs and Confrpl .• Conventional equilibrium airships are usually designed to be Dynamics and control studies of cone controllable by aerodynamic mean .t through ventional airships have also been con- the use of hull and empennage farces above ducted in Canada by DeLaurier (Ref. 12), some minimum flight speed. Below this and in France by ONDRA, the french govern- point, static forces only are available ment aeronautical research agency. This for control. The new hybrid concepts which latter work includes analysis of sling- combine large rotors with aerosta.: hulls load dynamics in connection with heavy- arc, by design, intended to circumvent lift airship certification ( Ref. 13). this problem through the availability of large thrust forces at all airspeeds, and A number of other analyses for specific to achieve near helicopter-like hover concept developments have also been made in capability. It also appears that some Franco, Great Britain, and the U.S. future airships will require rather precise controllability at or near zero airspeeds. A fundamental problem with most of These new flight characteristics will vary these new programs is the lack of a suit- with mission applications but in general aisle data base. Some of these new config- they establish needs for design criteria urations have strained theoretical know- beyond the present data base. For this ledge to limits without correlation with reason, the bulk of research effort in re- either wind tunnel or flight data. An cent yearn has been devoted to the devel- early indication of some of these problems opment of suP able analysis and simulation was revealed in discrepancies between small of flight. scale wind tunnel tests and analyses of hybrid concepts with large rotor systems One example of such effort is an ana- (fief. 14). Force vectors did not agree in lytical program developed by Goodyear magnitude or direction. Larger scale and (Ref. 10) for non-rigid heavy lift hybrids higher Reynold's number tests are scheduled which models flight path simulation dy- by NASA during 1982 to investigate these namic stability, and control concepts for areas further. various flight mission profiles. The vehicle motions, velocity changes, power Structures and Materials, - Two developments requirements, fuel consumption, and sus- in recent years which have major impact on pended payload dynamics are recorded via airship structures are new methods of strip charts and also displayed on CRT's. analysis, and new materials.

A similar but more comprehensive in- Past efforts in this area were extreme- vestigation was initiated under NASA ly limited by the complexit'es of the contract with Systems Technology, Inc. structures, In rigid airships, for example, (Ref. 11). This program is intended to be simplications and approximations were re- developed in three sequences or versions. quired which only by experience provided The first one incorporates the basic major reasonable results. In non-rigids, the elements of vehicle dynamics in steady envelopes and suspension system were treat- flight with simplified rotor models. The ed by assuming that strength and elastic second version contains the effects of characteristics in major portions would hull-rotor interference, and atmospheric exhibit relatively uniform behavior. turbulence. Version three will include payload dynamic effects simulation, ground Finite element methods using digital effects, and vehicle stability derivative computing equipment now provide a basis dcterminatton. The complete analysis is for more exact and more detailed computa- scheduled to be completed in July 1981. tions. A particular advantage results from It will be installed in NASA Am p s computer the ability to motel (analytically) the equipment and also be available to other dynamic behavior of systems taking into organizations with similar equipment. The account nonlinear characteristics and various elements of this proq, ram will be coupling effects. Fig.11 illustrates the adaptable for simulating a number of envelope and suspension system of a small. vehicle configurations including those non-rigid airship using a specifically with control and thrust units different developed program (Ref. 15). in numbe- and location from the basic heavy-Lift form rotor concepts. The piloted Structural weight continues to be one simulator facilities at the NASA Ames of the most important elements in sizing Research Center are also being utilized to airships, and hence determining their provide opportunities for piloted simula- efficiencies. Weight reductions can be tion of airship flight. This facility is accomplished through the use of composite shown in Fig.10 VI(I. In. Piloted AJranip Simulation

COMPU : ER DRAWING OF NONRIGID AIRSHIP STRUCTURAL ELEMENTS

Fica. 11.

BLACK Ai D WHITE P.OTOGRAPH

10 ORIGINAL C! OIL POOR QVAUIV

materials, and iie+ synthetic filaments and Thrust units already located in the proper films (for inflated components). direction seem to be one practical approach as was demonstrated by the side thruster The envelope assembly is the largest shown on the model in Fig, 12. This experi- single weight component in a non-rigid, mental model, designated IM-1, incorporated A saving of half of t-11 o weight would re= tilting propellers and a tail thruster as oult in a not reduct,+.a of 15 percent in well. envelope volume and 13 percent in propulsive power ifa complete ro-design is con- A French experiment, conducted by gNFRA oidered. Such savings may be possible used two intermeshing propellers with axes using a combination of composites for the at 900 to each other, demonstrated that hard structural components with newer syn- both thrust and efficiency ware enhanced thetic filamuntu ouch as Kevlar, and es s result. Graphite. An example of the actual application of new materials can be found n 9,a9JqtigU - The actual operation of air- the British Airship Industries Skyohip $00 ships in the past 19 years has boon limited which is deooribed elsewhere in thin paper. to thoso involved with private U.S, public The car, empennage, and none mooring and relations activities and Gorman aerial stiffening components were built using advertising as previously noted. Loth combinations of Kevlar and fiberglass com- these groups have employed methods similar pooites. to each other and basically not different from previous naval operations. These in- Another posoibility for weight reduc- clude operations from a fixed base with tion in envelopes could result from a do- hangar facilities and from portable equip- croaso in factors of safety. Currently, ment at various locations without hang- to little or no research on the sub- aring. The Merman operation primarily has ject. Part of this determination needs to employed the latter method, with a hangar be based on better correlation between de- usually only available as an assembly sign criteria and actual service experi- facility. ence, similar to that reported in (Ref. 16) for Navy airships. An examination of the possibilities for ground handling heavy-lift hybrids Some exploration of structural design was made by Goodyear and oponsored by NASA criteria was undertaken as part of heavy (Rof. 17). These indicated that nose moor- lift hybrid airship studies sponaorod by ing to a fixed or mobil mast continues to NASA (Ref. 1), but a considerable greater be the method by which weight penalties amount needs to be done if realistic re- from structural loads on the airship are quirements are to be established for new minimized. Fig. 13 shows the effect& of airship designs. Among these to the sub- total restraint (no weathervaining) on ject of gusts and turbulence. Criteria suspension system and envelope weight for used for past airships may not be very a 68 tonne heavy lift airship of 75,100 m3 applicable particularly for determining cu. ft. It can be seen that component loads from maneuvering with much higher weight could exceed total lift. thrust and carrying suspended loads such as possible with some the heavy-lift hy- C=tificatiosn - In the U.S., the only civil brids. activity (Goodyear operations) is certified on the basis of similarity of the airships prLML01 On - It is not likely that engines to Navy °L° type airships flown during specifically designed for airships will WWII. For this reason, a detailed certi- over be available considering the small fication for airships of any type has market such aircraft represent. In the never been developed. in contrast, the past, engines designed for other uses British Civil Aviation Authority was forced have been adapted for airships using spe- to develop a complete requirement (Ref. 18) cial gear boxes and components, and it is during design and development of Airship probable that. future vehicle designers Industries Skyship 500 - previously Aero- could be forced to continue this practice. space Developments AD500. It is antici- A significant difference between the past pated that a similar requirement will be and prosent, however, is the emphasis now developed by the FAA if new U.S. designs on low speed control. This establishes are built. requirements for higher thrust in some cases and for thrust vectoring through the Comment and Summary use of tilting propeller3 and cyclic and collective pitch variation. with the ex- Table 5 is a list of the several LTA ception of cyclic pitch, all of these sys- vehicles and their characteristics under tem., have been incorporated in airships development in various countries. The before but to a lesser degree. single largest project is the HELI-STAT program for the U.S. Forest Service. It is Response time for counteracting dis- possible that the programs in the U.K., turbances is crucial if any thrust system if successful, could surpass the invest- is to be effective. Even though inertial ment levels now indicated for the U.S. characteristics of airships favor longer projects. It is interesting to note that periodh, these would be shorter than the enterprizes in the U.K. are privately time required for tilting thrust axes. supported even though the efforts involve

i EFFCCT OF TOTAL RESTRAINT r I^ ON 75 TON HEAVY LIFT AIRSHIP

11J I NVI1 1011I WI NOMINAL OWY56 LIF1

5USf 1 N•-1/)N SYS1 W ►

NO%f M(X)RfD FNVELOPI WI

l If 1

NO!.f MOON# U SUSPI NSIUN SYST W1

0 ul 4C 50 f!0 vVIND tiff f O 11111111 I )` 11 V*ctor^a Thrust Test M001VI Fig. 13.

CURRENT AIRSHIP DEVELOPMENTS CHARACTERISTICS

MAX MA X VOLUME LENGTH PIA GROSS GROSS I SPEED USEFUL NAMEICO m 3 m m WT kq LIF ► k KNOTS LOAD kg H P COMMENT HEAVY LIF T AIRSHIP ; i^50 138 33 131885 11 AO UNDER STUDY GOODYEAR 33858 ( 69027 8780 HELI STA 1 21813 105 23 S 109 12) UNDER PIASECKI 21021 60 . 70 ?5589 5100 CONSTRUCTION A UNDER )481 55 20 10884 907G(^ 80 1814 380 ) ON TRI T; ' 3K79HI P 500 5132 50 14 AIRSHIP wn 5703 50681') 62 1883 300 NSTRU T I '1 IR HI eat 13055 56 14 AIRSHIP IN pU. _ 8256 5707131 65 2883 500 CONSTRUCTION LI 14) UNDER W DEUTSCHE 6000 60 15 8286 6286 61 1497 500 LUFMERAUNG _ CONSTRUCTION WDL III (2) W DEUTSCHE b0000 122 30 62239 &)8716 76 39909 2600 UNDER STUD Y LUFTWERRUNG KLI COST AIAT 49 AE.iQ5PAT IA L C J400 3' 15 6540 3447(2) 3447 1200 UNDER STUDY DINOSAURE 7 1 HPq 17 8 1 48 46 (4) OPERA'-ON:AL

UNL R ALCYON 6200 44 9151 5687i21 60 988 885 DEVELOELO PMENT G2 201 GOODYEAR 5741 59 14 5587 5587 12) d3 1488 420 Ca ; RATIONAL

(1) 0 1524 m ALT (3) t3 10 m ALT (5) HEIGHT (2) A 305m ALT (4) S L Table 2.

SLACi%' A1'14'J INTc PIIJTOGRAF14 novel departures from pact types. It is turbulence and gusts for various airship likewise noteworthy that the German opera- concepts. tion which io devoted to advertising and which also involved some risk venture capi- 4. envelope materials research to im- talization and is now reported to be self prove long term permeability, durability, supporting. These operations should offer and achieve lower weight fractions. evidence that government support is not necessarily a prerequisite to the initia- 5. improved methods of ground handling, tion of a new LTA venture. maintenance, and determination of all- weather flight capabilities. The new types under study and development in most cases are a compromise be- 6, Realistic assessment of design, tween slow flying equilibrium airships construction, and operational costs partic- with low energy consumption and faster ularly related to specific missions and more maneuverable concepts. But the total types. cost of flight vehicles is not fuel cost alone, although this factor will rise in The area of flight dynmaics and control importance as costs inc:oase. As shown in appears to be sufficiently emphasized in the productivity steadies of deltoid hy- current programs and should continue to be brids, such vehicles may be uniquely an important aspect of future research as suited to certain mission applications pro- well. vided that /3* values of 1.0 are not required. This is reasonable since no single In sunurary, current developments in- type of vehicle of any wind has -var been clude continuing efforts in the U.S. in found to :satisfy all requirements. research on the dynamics and control of hybrid airships, structural analysis, and LTA technology and development today scaled experimentp. Vehicle programs in- appears to stand on the threshold of an clude the construction of a heavy-lift era of new uses Compared with other aero- HELI-STAT for logging demonstrations and nautical types, these developments are the building of a flight vehicle for Coast miniocul y and extremely vulnerable. Their G laard mission demonstrations. Activities viability is conditioned by the critical in foreign nations include building air- need for a true industrial base. None ships for demonstration of aerial adver- exists at present. tising, passenger and, freight transport, coastal surveillance, and general utility. The particular design effort involved The successful achievement of these and in the various projects described in this future efforts will be dependent on build- paper is somewhat akin to the kind of ing an improved industrial base and fragmented aeronautical endeavor that broadened R&D effort. existed in the U.S. following World War I, where there was much enthusiasum, limited financing, and inadequate engineering in many cases. * /9 = Static Lift/Gross Weight Basic technology development should References include : a il the subdisciplines involved in design, construction, and operation. It 1. NASA Contract NAS2-8643-Report Nos. is generally true, however, that most re- CR 151917, 151918, 151919, Sept, 1976. jearch today is only in connection with 2. U.S. Davy Operational Requirement OR- particular concepts and only on subjects W1019-SL. which appear to be obstacles to predictable 3. NASA Contract NAS2-9826-Report No. design. Few if any of the incremental re- CR 152202, Dec. 1978. finement: normally associated with aero- 4. Navy Report NADC-80149-60 "Maritime nautical rc,:Warch are part of current in- Patrol Airship Study", March 19, 1930. vestigations. Whether these will be, re- 5. Browning, R.G.E. "Canadian Interest main:, tobe seen. Without a continuing in Modern LTA Transportation" AIAA research effort there is little hope for Paper 79-1585, July 1979. true advancement in the field. 6. Coloque International Economie et Technologie Des Aeronefs Alleges, Amon; the many elements needing in- March, 1979. vootigation, perhaps the most important 7. RAE-RNIAS conference, London, March are: 1981. 8. NASA Technical Memorvndum 81151, July 1. Large Reynold'; number aerodynamic 1980. drag and the effect:; of various configura- 9, GLOD, J.E. 11 4irship Potential in Stra- tion changes. tegic Airlift Operations", AIAA Paper 79-1.598, July 1979. 2. Design and location of propulsion 10.Nagabushan, B.L. & Tomlinson, N.P. ,inrt:; for maximum efficiency. "Flight Dynamics Analyses and Simulation of Heavy Lift Airship", AIAA Paper 79- 3. Development of structural design 1593, July 1479. criteria including particular definition 11,NASA Contract NAS2-10330. of realistic requirements for flight in 12.DeLaurier, J. & Schenck, D. - "Airship

ORIGE 'L?',; . ^ ...,, OF POUR 4

ORIGINAL oynamic st°ijbjltty ,l A1nA Paper 79-1591, OF POOR QUALIV July 1970. 11. llrroovi, M. "Etude du Cotipla€e, Pilotage Trouillage d 1 un Dlrigily le ale Transport" EMA Doper No. 117127, Jan., 1977. 14. NASA CR 152127, April, 1978. 1Fi, Sampatli, S.G. et al "Determination of the.,f Natural Frequency of an Airship ^ odo 1 " . 1 0. 'Navy Bureau of Aeronautics Design Memo 402. 17. NASA Contract NAb2-10448. 18. British Civil Air Worthinoss Require- ments, Section 0, Dec., 1979.