The airship's problems and the possibilities for their solution in a short-haul transportation environment are surveyed. The problems are derived from both past experience and envisioned operation. Problems relative to both fully buoyant and semi-buoyant configurations are considered and their origins in principle discussed. Also addressed in this paper are the state-of-the-art technologies with the potential of providing answers to the airship's operational difficulties

Walker, C. D.

English

NASA Technical Reports Server

N76-15039 "
OPERATI(_IALCONSIDERATIONSFORTHE AIPSHIP
...... IN ,S,I,_,RT-HAULTRANS_
Li Charles D. ;!alker*
ABSTPACT: Thts paper surveys the airship's problems and the posst- ' _
hllities for their solution tn a short-haul tran.-portatton environ-
_ent. ThF problee_ are derived from both past experience and envi-
sioned operation. Problems relative to both fully buoyant and se_i-
- .. buoyant conftnurations are considered and their ortoins in principle
"_ discussed. Also addressed tn thts paper are the state-of-the-art
technologies wtth the potential of provtdtn_ answers to the airship's
operational difftculttes.
l The airship as a _de nf short.haul transoortatto_ appears a_onc the lonn ltst of
potential applications "or the modem operattnnal vehicle. But there is, at present,
no operational transport _trshin. The anti;tpa ed problems of or,oration, a necessary
! _ element of the c,mcept evaluation rot any row system, e_JSt then be based upon any
_ pprttnent past operattnn. Thts op_,attonal exr_rtence ts, however, limited in tt_
direct correlatlont_ _./e_ demand-_ It is liTitednot only in the scope of appli.
cati_s hut also to time base (as coe_ared to span of operations for Heavier T_an At_)
and level of tec_moloov. Vlrtuallva11 inputs keyed to later field airshipsoria_-0 nated prior to Iq39. Pllltarvand limitedcoe_r_rclal(ma;nlvadvertlsinn)experience
! continued tn the early lO6O's in the form of non-ri_l:is. Only limited com_rclalapp)tcation is _n notnn. Curre t r sea ch and development is almost nonexistent.
?
So the prese.t day planner, wtshino to determine the applicability of a moder_ air.
ship to the shert-h_ul air transport market, r,_st either tnnore the labors of his
: technological forehe_rers and start fro_ scratch or he can build on the past. He has
the _htlttv to survey, filter and assimilate the facts and ftoures of the airship's
operational history, r)ecermintne the operations and the _roblems that are now rele-
vant to a short-paul role, he can make swifter, less costly and less risky syste_
¢ostnn decisions. This p,tper wtll make a beotnnt_n tn this direction.
*Manaee_, Aorltno, Bedford, Indiana, I!.S.A.
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,_ REQUIREMENTSOF THE MODERNAIRSHIP IN SHORT-HAULTRANSPORTATION -_c,_
.'. Eventually,a set of criteriawill be required to evaluate the ennlneerin_solutions J
_"' \, of the a_rshtp's operational shortcoetnos. Thes_ c_:terta can be extrapolated from "
' the (leneral reouirements of a , 'oft-haul system. _,
,., Renulrem_ts,,of Short-l]aul,,Transportatlon,, .:
_ The neneral renutrements of the short-haul system are no different than those of any _!
;__ large transport system.: safety, convenience andcomfort, comparable cost, andcom- ":_
+ ' muntty benefit. From these aeneral reautrements, the technical requirements of a e,
" short-haul mode aircraft may be drawn. These are shown tn Table 1. _'-_
, Table 1 I,
_ Technical Requirements of an Aircraft Short-Haul Mode
_: • Reliabilityat Least Eaual • Accessibleto the Traveler/ ,_
_- - to Flxed-WlnaAircraft Shipper i_
"!. • Navioationaland Flight • Compatiblewith the Traveler/
: Path Control Atds to Provide Shipper _';
i_ _ All kfeather Operation
• External Noise at Acceptable
;_ • Intern1 Noise Vibration, Levels
t • Sensitivity to Atmospheric L
_' Conditionsat Levels Attractive • Low Air Pollutlon
_ to the Traveler/Shlpper
. • Low Enemy Consumption ,
_'i",' • Competitive Payload Capacity • Minimize Utilization of Land
_:, • Competitive Block Speed and New Facilities
The short-haul aircraft w111 be operating over travel distances of up to SO0miles :
,', and in low, medium and htgh density markets. !
OPERATIONALPROBLEMS OF THE MODERNAIRSHIP
It can be assumedthat in this operational environment the modernairship will en-
counter many of the same difficulties as tts ancestors during the first third of this
century. There wtll also be new problems spawned by market demnd_ institutions, and
modern technology. The ltst of problems that follows contains those difficulties that
appear to be emst nearly associated with the short-haul operating mode.
Slow Speed Aered_namtc.,Con,t_ol
This problen" is not one peculiar to the airship. It is commonto all aerodynamically ":
cont_lled bodies. Basically it ts the control surfaces' inability to p_ovtde an
adenuate resultant force due to lack of sufficient flow velocity. The upper thresh-
old for loss of aerndvnamtc control is aenerallv 15 mph. It was found that a kind of
control reversal also occurs at the_e low speeds. Thts has been investigated and pro.
_ cedural remedies can be instituted. _ This p_oblem is particularly hazardous during
landtne maneuvers when positive control ts reoutred for moortn_ operations, as well as ;
for the welfare of the ,_htp _tself.
TPt _ Contro1
The balance ad.tust_ent of an airship in flteht has two inputs - aerodynamic and static. ._
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i
Aerodynamictrlrvnln_is doneby deflectionof the elevators.Aqaln,thisis a common
pointforcontrolledaerodynamicbodies. But statictrimmingis mereobviousin a
buoyantsehicle. Statlctrlmls acco_llshedby adjustlngthe center-of-or_vitylonai- ) i
tudlnallv.The _edluPof statictrimadjustmenthas usuallybeenballastmoven_nt,
ballonetinflationcontrol,valvlngof liftinggas,or ewn shlftln_on-boardperson-
nel. ObvlousIy,the principleIs positionalcontrolof mass. Adequa)econtrolof
statictrimcan effectivelyminimizethe demandforaerodynamictrim._
Buo_anlcyControl ,
Thlsproblemareacan be basicallydescribedas the reoulremento maintaina levelof
staticllft. Controlis a functionof vehiclealtitudeand liftingmediumtemperature. -
has Valvtn9 -!_
The valvtnn of ltfttnn gas ts Intimately tted to buoyancycontrol. 7n fact, tt is a _?
meansof control. _as wtll be valved tf the airship exceeds tts pressure altttude ¢
and the has cell or envelope ts at maximumvolumecondition. There ts the potential
of a catastrophic_atlure of the envelope, so has ts released to reduce the pressure
differential. _as maybe valved to control ascent and descent, although it Is the
most expensive and risky means,
Ballast Mana_e_nt
Aqaln,thls is a meansof buoyancycontroland alsopotentiallya trimcontroltech- i
nloue. BallastIs massand has consistedof such innocuousItemsas sand,lead,and
watei'.The inefficientuse of ballast{andgas valvlng)in flightcan leadto a con-
dltlnncalled"exhaustion"by the Germans. It Is the conditionof an airshipthat
has lostits meansof buoyancy{andpossiblytrim)control.
Manp:_er(_roundCrew)
The bulkof the airshiprenulredmany personnelactivelyengagedin holdlnoherdown
when the shlnwas not flying. Beln9a buoyantbody,theairshipwas _nerally at the
mercynf sn_ of theelementsand peoplewere the,_steasymeansof activecontrol.
Today,thiskindof lahorIntenslveactivityIs a problem.
Weat)ervant)e
Another _rou_d prohlem, weathe_antng ts actually a result of the vehicle being a
buoyant hody and sub.lect tn any sufficiently laroe disturbing motion of the surr_,_T_c!-
tno medium.wtnd. With a streamlined conftnuratton and atrfotl_ aft, the airship
continually tries to _ofnt tnto the wind. b_oortnnan_ ground handltnq e_utpmentand
operations must be adaptable accordtnely.
Weather +
Perhaps _otentially the greatest problem, weather has manyfacets. _usttno near the +
ground maycause a vehtcle/nro_Id collision. Turbulence at altitude can produce
structurally damantneshear forages. Themals can oroducean undesirably rocky ride-
trlmcontrolproblems.Precipitationand condensationFrovldebuoyancyproble_
throunhPass accu_ulatlonon thevehicle'ssurfaceandpossiblecoollnnof the llftlno
eas, reducing displacement. Te,)erature varlattons result tn chanoesof ltfttnn qas
and thus affect huoyancy. The control surfaces can easily be _an_ed tf tce ts al-
lowed to accumulate. Thts problem ts co_n to all aircraft. Loss of visibility ts
not as great a Frohlem for an airship as ttts for a heavier than aircraft because an
atrshtp can red,;ce tts vel_tty to _ero tn obstacle avoidance wtthout loostnn lift.
It _tll be _r,re of a danner in conoestedairspaces. Lightning strikes are not a _reat
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1976007927-267
j ?
problem because even a large puncture of the oas container doesn't meat. a catastrophic
loss of lift. And the use of helium, rather than hydrogen as the ltfttna gas, mear.s
_- that combustion is neaated.
_, Hu_n Error
i' Thts problem is all pervasive and, as Ionn as man remains in the operational system, i
_ thts problem area _t11, to somedeoree, be present. /
ill "_" Air Traffic Control t ,...
This headlno refersto a cataqory of problems derived from the interactionof air t,
vehicles within a ltmtted volume of airspace. An atr transport system hrtngs these i, -, j_
problems of coneestton upon the airship. •
: " Useful-Load Transfer r '
_ t The transfer of payload to or from the airship, both on the ground and hovering, is i '_
' I .. as presenttno some touah enqineertnn and procedural problems. Problems of post- i '>
:' ttve load postttontna, vehtcle control, and buoyancy control are foremost in thts new " _-
aPea. I_
Land:'In.oImpact C_tro_l
Because airships were orl_Inallyconstructedof Qlrder and wire frames overlayedwlth
fabric skins, any impacttnQ contact with the earth could cause structural damage.
I_act loadtna would still be a problem wtth rigid structures of thts type.
'*- InterfaceHith ,C,round Handlin,_/Sup,p#rt EO,UlIpment
_ Problems of enuipment/system interfacing wtll becomea laraer concern when the de-
;,, st_n complexity of the airship escalates to meet the problems touched on greviously.
Both active and passive _round support wtll be important to a meore_ or docked airship,
POSSIBLETECHNOLO(;ICALAPPROACHES
All of the previously descussed problem areas must be evaluated to determine their
basic nature. Only then can effective, detailed approaches to solvtng the problem
be proqran_ed. In the paraoraphs to follow, however, a start is made at isolating
state-of-the-art concepts and techniques that may be able to evolve solutions.
Vectored/Lt ft Thrust
Prnductn_ vectored thrust bv swiveling propulsors and by reversing propellors.ts pos-
stb)e. Both _ethods are either in operation today or in the prototype staae, o
Another approach that ts in operation ts the use of the directed thrust Jet of a turbine
engine; an application of blown flap technolooy.
Improved Control Surface Response t
....... i
Several current control systems appear to be applicable. Control Augmentation Syster,
flv-by.wt re, and Acttve Control Technolo,y would provtde an attracttve coupl tno of
dtqttal/electrical/hydraultc/mechantcal systems for the tncreastnqlv complex control
requirements of the _odern airship,6, 7 Boundary Layer Control would oo far toward
solvtnn the principle cause of _urface control loss.
_m_)rovedStatic. Trtm
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1976007927-268
The approach to tmprovtnq static trtmmtna may be the positional control of mass in the I
form of a lt_utd. Aircraft are currently uttltztna on-board fuel for this purpose hy
controlltnq tts locatton in the fuel tanks. Additionally, the concept of a semi-buoy- ..
ant airship would provtde mass for an tnerttal keel that ts Inherently trip stabtlizina.
Thermodynamic Ltft tna Gas l_anaQement
Sugaestions for artificial means of super heating the 11fttng gas to increase lift on
one hand and cool, compress or 11query the has to decrease ltft on the other, have
ohvtous merit. The means of compression and ltautftcatton _ay prove too massive,
hoHever.
Hechantcal/Themal Ictn,a Prevent ton
Proven means of applytng thermal energy to aerodynamic surfaces to prevent tctna are
available. The heat produced by a thermodynamic has managementsystem would also prove
helpful, Hydraulic and mechanical means of releasing the tce are practical.
Increased Speed Capabtltt _ ._
Thts t_provement has many beneffts tncludtnQ economic competitiveness and weather
avoidance. It may he accemp14shedby use of lamtnar flow control to reduce draa, !
hetter aerodynamic dest(In, and turboprop/turbofan propulsors.
Avton_cs 1
The v,tde ranae of systems available and programed can provide atds to solve the
weather and atr traffic control problem. Instrument Landtnq System and Area Navt-
aatton are two systems tn extstance, l_tcro-wave landing and discrete-address beacon i
systems are projected atds of importance. Heather forecasting provided to the system,;
user wtll ao far to assist the operational airship.
Improved Flt,_ht Crew Tratninq
Simulators, currently an tndtspenstble part of flt_ht cr_ training should improve
the airships' efficiency and safety.
?.round Hand]tn,q/Patertal Handltnq Equipment
In a competitive transport market, the atrshtp cannot t qnore the existing container-
Ized/hulk car ao handltn_ systems. In addtttont consideration to adapting conventtenal
neneral purpose equipment such as vans and flat-bed trucks should be given. Thts
could assist tn opentng new markets.
Improved Voortn._ l_ethods i
The prohlems of _oortng and handltnq airships wtll not soon be gone. But tnnovat|ve
devices such as tumtables for mooring and direct moortno to the airship's undercar-
riage structure could ease them.
Further study and clarification of the semi-buoyant ]tft concept may tn ttself prove
the most Important solutton to the modern airship's problem. The successful adapta-
tion of the safe.st form of atr travel wtth the best understood and utilized form
could man a more efficient complete transportation system.
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!:w I .......... ' _. If" .,i_
j I',
I
REFERENCES: ..
.: -j 1. Vtttek, J. F., Problems and Issues For Short-Haul Air Tran.sportati_, Society of
Automotive Enntneers, New York, New York' ( t_ay, 1972 )
, 2. Coty, U. A. and Kasltnq, P. H., V(STOL and STOL _or Short-Haul Transpor.tation, AIAA
,. Fourth Annual t._ettno and Technical Dtsp_ay, NewYork, New York '( October, 1967 ).
-. _ 3. Fisher, R. P. and Ross, R. S., Recent Airship Developments and Applications, Pro-
ceedtnqs, Sixth AFCRLScientific Balloon Symposium, Bedford, Massachusetts ( Z7 Octo-
ber, 1970 ).
_ 4.0.c.Afrshi(llPFebruary,Aerod_namfcs__1941 U.).S. War DepartmentTechnlcalManualTM 1-320,Washlnqton, '_
_"" 5. Stepnlewski,W. Z., VTOL Aircraftand Short.HaulTransportati.on,AIAA Student ,
Journal, New York, New York ( December,197? }. "'
6. Fraser, P. C, and Felleman,P. G., Ol,qitalFly-By-Wire,Astronautics& Aeronsutics,
New York, New Yor_ ( JulylAuaust,1974 ).
:.. 7. Goodmanson,L. T. and _ratzer, L, B., Recen.t Ad.vanc.esin Aerqd_nam.t.csFor Tran s-
_ poTt Aircraft,Astronautics& Aeronautics,Ne_ York, New York ( January, 1974 }." '
.
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Operational considerations for the airship in short-haul transportation

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