(SANITIZED)PROPOSAL NO. 11510-A - SMALL PLASTIC AIRSHIP

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78-03642A001300040012-0
• Release Decision: RIPPUB
• Original Classification: K
• Document Page Count: 38
• Document Creation Date: December 22, 2016
• Document Release Date: June 14, 2012
• Sequence Number: 12
• Publication Date: November 8, 1957
• Content Type: LETTER

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Pm ft
Attention:
Sdbject:
Reference:
Gentlemen:
November 8, 1957
(a)
Code 461
11510-A - Small Plastic Airship
cr,v
157 ctile
61)
-1/44/tr(A_J
quest for proposal on Magee II and II dated
November 1957
(b) Propose,' No. 11510 dated 20 September 1957
is pleased to submit herewith proposal No.
11510-A covering phases II and III of the Small Plastic Airship.
This proposal will be considered a supplement to reference CO
and the same terms and conditions will apply. The two points cov-:
ered in the enclosed technical discussion will be as follow*:
1. Raise the airspeed of the vehicle at ceiling from 30
knots to 50 knots (no wind condition).
2. Add the design objective that the vehicle should be
field inflatible iu surface winds up to 15 knots.
The estimated cost of phases II and III is $152,748 plus a fixed
fee of 413,452 for a total of $2460240 of labia a cost breakdown
La enclosed herewith (Schedule A).
The proposed delivery schedule is pointed out in Schedule B.
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We are very happy to
there are any questions
please advise.
vembier 8, 1957 25X1
U. If
you,
Approved by
Copies to
s,
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Labor
557 hrs. *$4.10
317
.85 $14,245
45 2,070
65 3.W5 20,2543
Burden
Research De
Balloon cturiugDept.
t41,erat1545
Labor
or
4,050 hrs. 85 15,593
1,600 bra. 25
2,800 bra. $2.00
2,793
1,557 brs. $3.30 5,138
5,800 hrs. 0 $2.75 15,950
8,450 bra. * $2.15 ).8.168
692
39,256
231909
$114,623
.10 2,837
. $3.85 3,850
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1,100 bra. IS
200 bra. 44
2,550 bra.
Burden
Regfaril pent 692 bre. $3.30 2,284
Balloola Manufactturlps, Dept. 1,000 bre.9 $2.75 2,750
Balloon Operations to* 3,850 hre. 8 $2.15 Bare
Material and Fabrication
Total
00 Conting
Total Costs
& A S 654
Fee g 7%
Total Se/ling Price
for tests in Phases I/ aM II GTE
Portable Mooring Mast On
Large, Hanger-type building for inflation tests GTE
$16,472
nal
165,307
6
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Months:
1 3
4 - 6
7 - 9
Fbase /
1 - 3
%sota1 - 4 months
Flight tes
modi
dravinge
en
of Dee
1
of design de1 and
of detailed design
Feb cation of Prototype Model
Final Acceptance Teets
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=DUCAL DISCUSSION
Proposal 11510-A
Phase II of the proposed program is a developmental and testiog phase.
It will include the preparation of detailed manufacturing type drawings
from which the first design model will be fabricated. The detailed design
will be based on the preliminary drawings from Phase I. This portion of
the work vill be done in the Balloon Department. A photograph of part of
this faci:..ity iu Wawa iu Figure 1.
The ooepiete- venicle will then undergo inflation and flight tests.
The initial inflation tests will be conducted in an area protected from
the wind, preferably- in a large, hangar type building. The initial flight
tests will be conducted during relatively calm days and a portable mcoring
mast will be required during the initial flight tests to permit its re-use
On successive days without deflation. As the ground crews and pilots be-
come more experienced with the vehicie, tests will be conducted under vary-
ing wind conditions to test the vehicles compliance with the design ob-
jectives outlined in Phase I of this program. During the inflation and
flight tests minor vehicle modification Llay be made.
The manufacturing drawings will be finaliL to incorporate corrections
and/or modifications or deficiencies discovered dur.Lng the manufacturing
and testing periods.
Phase /I/ of the proposed program will include the construction of
a prototype vehicle from the finalized drawing in Phase II, flight tests,
and delivery of the sponsor. The flight teL will be conducted in the
presence of the sponsor and will be conducted to determine the vehicle's
compliance with the design objectives outlined in Phase I of this program.
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11,
Proposal 11510
SMALL PLASTIC AIRSHIP
Prepared. for
Prepared b,
Geophysics Section
Approved by
September 12, 1957
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I. OBJECTIVE
TABLE OF CONTENTS
II. INTRODUCTION
III. DESIGN OBJECTIVES
IV. PROPULSIVE ENERGY REWIREMENTS
V. FLUID DYNAMICS
A. Viscous Flow Theory
B. Electric Analogy Tank
C. Stability Analysis
VI. STRUCTURAL REQUIREMENTS
VII. SPECIAL PROBLEM AREAS
A. Field Handling and Inflation
B. Controllability
C. Other Lighter-Than-Air Systems
VIII. PROPOSED PROGRAM
IX. REFERENCES
ii
Pagel,
2
3
Is.
13
13
15
17
20
21
21
21
21
26
27
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LIST OF ILLUSTRATIONS
Figure Title
Page.
1.
Possible Configuration For Small Plastic Airship
7
2.
Surface Area Vs. Fineness Ratio For Equal Volume Bodies
of Revolution
9
3.
Farness Geometry
19
4.
Shroud in Place, Protecting Balloon From Wind During Infla-
tion Process
22
5.
Shroud Being Removed
23
6.
Model l3-S-8
24
7.
Model 21-8-8
25
iii
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PROPOSAL 11510
TECHNICAL DISCUSSION
I. OBJECTIVE
The objective of this proposal is to outline the areas of research
and development which are necessary for, and which will culminate in, the
preliminary design of a minimum size plastic airship. This work is an
outgrowth of the program initiated under Contract . The
work to date has been conducted on a very broad basis, applicable to the
LTA field as a whole, without limitation as to size, altitude, endurance,
etc. Although the proposed work is directed more toward a definite goal,
the approach will continue to be based on sound fundamental principles
and laws rather than on convention. In those cases where the laws are
not written or specified, or written and not verified, an attempt to do
so will be made, but only in those cases where the knowledge gained from
such laws will be beneficial to the design of a minimum size, but extremely
useful, plastic airship.
1
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II. INTRODUCTION
The powered lighter-than-air field has received considerable atten-
tion since its inception in the nineteenth century. Unfortunately, the
technological advances of the recent decades have not been applied in any
coordinated manner to this field. In most cases the available data, al-
though voluminous, fits no natural pattern. Very little is known about
the real reasons for favorable results in some cases and for less favor-
able results in others. The best results have been obtained largely by
a process of trial and error. The results of such developments are avail-
able only in the form of designs with specific geometric properties and
not in the form of laws or facts that are responsible for the results.
The progress on this program to date has been directed toward the estab-
lishment and/or understanding of the fundamental principles governing
the design and operation of powered lighter-than-air vehicles. Although
the program is now directed more toward a specific goal, a fundamental
approach will continue to be utilized.
Although it is not believed possible to arrive at a completely op-
timum design within the scope and time of this program, it is expected .
that a design incorporating considerably advanced techniques will result.
The program will emphasize the utilization and extension of those advan-
tageous features which are inherent in the airship.
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III. DESIGN OBJECTIVES
The preliminary design will be based on certain performance objec-
tives and will be limited according to the availability of field equip-
ment and personnel.
Ground handling difficulties are minimum for a minimum size vehicle.
Idealistically the ground handling difficulties can be expressed as being
proportional to the product of the volume, to the two thirds power, times
the surface wind velocity squared. Also the structural efficiency, as
defined by the ratio of payload to gross weight, diminishes with an in-
crease in size1. For these and other reasons, emphasis will be placed
on minimum size, commensurate with the performance objectives as listed
below:
A. Payload, and/or luggage
B. Cruising altitude
C. Free ballooning capability
D. Cruising range at zero wind velocity
excilli A oploitirY /
E. Minimum speed t V sea level LO- Wiwi) - J70/077knots.
A A
A high degree of flight stability as well as excellent maneuvering
? 400 lbs.
^ 7,000 ft MSL
2 hrs.
? 100 miles
capabilities is essential. The vehicle must maneuver close to the ground
while the payload is decreased by as much as two-thirds. These objectives
will be increased wherever the gain can be obtained without incasing
the vehicle size.
F ezd htJ,ie
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IV. PROPULSIVE ENERGY REQUIREMENTS
A basic problem common to most powered lighter-than-air missions is
to propel a configuration with a maximum ratio of volume to weight through
the atmosphere with a minimum expenditure of fuel and a maximum degree of
directional stability and control.
Although considerable work has been conducted to individually opti-
mize airship components, we believe it is essential to consider the air-
ship structure together with its propelling, stabilizing and controlling
devices as a unit. Components should be so designed and arranged to com-
plement, rather than to interfere, with each other.
The analysis of the problem to approach an optimum configuration for
the task will include giving consideration to such basic parameters as:
A. Shape and fineness ratio for:
1. Size reduction.
2. Increased resistance to applied aerodynamic bending loads.
B. Boundary layer suction for:
1. Over-all energy requirement reduction.
2. Directional stabilization.
3. Directional control.
C. Conventional as well as rear propulsion for increased efficiency
and controllability.
D. Ring tail and shrouded propeller versus conventional fins for:
1. Thrust augmentation, particularly at low speed.
2. Flow improvement around hull.
3. Propeller efficiency increase and/or weight reduction of
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stabilizing surfaces.
4. Structural strength increase.
5. Increased directional stability and control, especially at
or near hovering conditions.
E. Engine air requirements (for cooling and combustion) and their
possible relation to boundary sucked air.
A. There appear to be several configurations worthy of investigation
in the early phases of this program. Some of these are:
1.
Small fineness ratio:
a. Aft propelled by ducted propeller serving also as the
stabilizer.
b. Some distributed boundary layer suction.
c. Boundary layer air used for engine intake or cooling
purposes.
2. Larger fineness ratio:
Same as 1. above but without boundary layer control.
Large fineness ratio: (4.2 to 1)
a. Stabilized by boundary layer control, eliminating the
need for fins (as suggested by Dr. August Baspet).
b. Conventional engine location.
4. Conventional arrangement with or without distributed boun-
dary layer suction.
The components involved in the configurations of 1. and 2. are ar-
ranged to complement each other. Although the magnitude of the over-all
reduction in drag is difficult to estimate, the arrangement presents a
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form of ideal propulsion called boundary layer propulsion. Configurations
of 3. and 4. minimize balance and flow separation difficulties.
Boundary layer control is intimately involved in all four suggested
configurations. Reductions in drag have to be closely measured against
the increased complication to determine the degree of usefulness. Unfor-
tunately, the theories are not verified at Reynolds numbers corresponding
to those of a full size airship. Measurements are being conducted on
other programs, and these results when they become available, as well as
theoretical predictions and measurements on this program, will be applied
to this analysis.
A list of apparent advantages for Configurations 1. and 2. is .presented
below. The full potential of Configuration 3. can only be estimated after
more progress has been made on programs now underway, particularly those
at Mississippi State College under Dr. August Raspet.
The degree of departure from the conventional shape (configuration 4.)
toward the short "fat" shape (Configurations 1. and 2.) will be evaluated in
terms of its advantages as well as the complications involved in preventing
flow separation. A series of shapes between these two extremes will be
analyzed theoretically for their over-all advantages prior to the selection
of a given shape for detailed investigation and preliminary design purposes.
On the assumption that flow separation can be prevented at no great penalty
by distributed suction on a shape such as presented in Figure 10 the follow-
ing advantages are to be gained:
1. Propeller thrust is combined with stabilizing control surfaces
to give low speed controllability at and near hovering conditions.
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POSSIBLE CONFIGURATION
FOR SMALL PLASTIC AIRSHIP
Tubes for Boundary
Layer Suction
Standard Light
Airplane Engine
Ducted Propeger
Arrangement
--30'
Two-man Gondola
50'
Streamlined Strut for
Stabilizer Support
Approximate Volume, 20,000-25,000 lxl?ft.
Figure I
7
Tali Assembly
for Directional Control
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111'
2. When flow separation is prevented, the drag of an airship is
largely a function of the ship's surface area. (Figure 2 shows the rela-
tionship between the Relative Surface Area and the Fineness Ratio for equal
volumes of a body of revolutionl.) This reduction in surface area results
in both drag and size reduction, which in turn reduces the propeller, engine
and fuel requirements, with a further decrease in size of the envelope neces-
sary to lift them.
3. The lift of a ring air foil has twice the lift of an ellip-
tic flat plate that spans a diameter and has a quarter of the area2. It
operates outside the ship's boundary layer with a resulting increase in
effectiveness.
4. A ring tail can be designed to superimpose a favorable pres-
sure gradient on the rear of the hull, which retards boundary layer growth
and reduces drag.
5. The ring tail can be used to increase the mass flow through
the propeller, with a net result of a gain in thrust without a loss in ef-
ficiency.
6. The propeller, like the ring tail, superimposes a favorable
pressure gradient on the rear of the hull, which retards boundary layer
growth and reduces drag. When the propeller is ducted, the pressure in-
crement forward of the propeller is large and the pressure back of the
propeller is nearly constant3.
7. The ring-acts as an end plate to the' propeller blades and
thus reduces the falling off in thrust toward the tips. The space between
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RELATIVE SURFACE AREA
..)
SURFACE AREA VS FINENESS RATIO FOR EQUAL VOLUME
BODIES OF REVOLUTION GENERATED BY THE EQUATION
y x
2f el."
n = Dimensionless number
y = Radius of revolute about the central axis
x = Coordinate along central axis
f = Fineness ratio, -Eliza.
L = Length of body
. _
)
I
r.
I
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the blade and the ring must be kept small. The ducted propeller would
have much broader blades toward the tips, with a possible appreciable
increased propeller efficiency. Ordinarily, the main consequence of the
ring would be the increased skin friction drag on the ring. By proper
propeller and fairing design, however, this loss will not be appreciable.
This loss also must be somewhat discounted in this case because the ring
eliminates the conventional tail surfaces and their high drag contribu-
tions. In one example3? the ring and plate effect increased the effi-
ciency by 11 percent.
8. By proper ring design, the forces interacting between the
ring and the propeller can increase the efficiency by another increment.
In the above mentioned example this amounted to approximately eight
percent.
9. Variable pitch propeller blades are required when the ex-
ternal rate of variance changes appreciably with flight speed. The pres-
ence of the fairing or ring makes it possible to keep the rate of advance
actually experienced by the propeller more nearly constant, reducing the
requirement for variable pitch blades. This beneficial effect arises
from the fact that the velocity increment due to the ring is more pro-
nounced at lower flight speeds.
10. The increase in static thrust for a ducted propeller can
be spectacular', which, of course, is important in takeoff and landing,
particularly from fields not considered airports.
11. The ducted propeller allows the use of a smaller diameter and
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higher speed propeller, which results in a reduced propeller and engine
weight in a small ship.
12. The ring surrounding the propeller is a safety feature,
possibly of importance in field operations.
13. It is common practice to define the resistance to aerody-
namic bending loads by the formula:
R31rAF
=
where:
f = resisting force
= length of the ship
R = largest radius
LIP = pressure differential.
From this it can be seen that a ship of lower fineness ratio is or-
dinarily a much stronger ship, or conversely the ship can be made smaller
for the same strength.
14. As the fineness ratio is decreased, a reduction in profile
area is experienced. This in turn reduces the aerodynamic forces acting
on the ship.
15. The aerodynamic loads on the stabilizing surfaces can be
better absorbed by a ring tail configuration, which is inherently a super-
ior type structure ascompared to a cantilevered fin type.
16. A smaller ship has an increased structural efficiency5. A
higher percentage of the gross load will be in payload. The arrangement
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offers some advantages regarding boundary layer suction. It is possible
that air requirements of the engine can be combined beneficially with 'the
suction requirements of the boundary layer.
The problems in weight and balance do not appear to be insurmountable.
Present day lightweight, high strength materials, as well as advanced
stress analysis techniques and strained measuring devices, make such an
arrangement appear feasible. Several engines suitable for rear installa-
tion are currently available.
Care must be exercised in defining a configuration which will be
stable for both moored and flight conditions.
Other difficulties that may 'be encountered are incompatibilities be-
tween propeller diameter requirements and ring diameter requirements.
Another important unknown at this time is the effect of the hull on the
velocity of the air flowing in to the propeller. Once these items are
determined, however, there are 'numerous parameters to be adjUsted and
compromised. Different techniques to replace conventional moveable control
surfaces will be investigated. It is expected that inflatible pressure
beams can be substituted for this purpose and will be the subject of con-
siderable model as well as theoretical work.
It is realized that other programs evaluating ring tails and rear
engine installations have been conducted. Reports on all of these programs
have not been received The reports reviewed to date6 indicate the de-
sirability of further investigation of these features.
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V. FLUID DYNAMICS
A. Viscous Flow Theory
The resistance of an airship is due almost entirely to the viscous
action of the fluid which causes the growth of a boundary layer of con-
siderable thickness, this being aggravated by the extreme length of most
airships.
Theoretical methods are now advanced to a sufficient degree to al-
low the calculation of the viscous drag of bodies of revolution7. Unfor-
tunately, these methods utilize certain assumptions which have never been
verified by in-flight boundary layer measurements on airships. The drag
values for airships have been obtained experimentally, either by full
scale deceleration tests or by wind tunnel methods. Large discrepancies
have appeared in these data8, due largely to a lack of understanding of
the boundary layer growth mechanism which is sensitive to free air tur-
bulence, surface roughness and the Reynolds number effect. A method
described by Paul S. Granville9 presents a. procedure for calc\alating the
viscous drag of bodies of revolution. It involves the detaild analysis
of the development of the boundary layer from its origin on the nose, to
a zone of laminar flow, to a transition zone between laminar to turbulent
flow, to a turbulent boundary layer and finally to a frictional wake.
Required for this procedure are:
1. Profile dimensions.
2. Pressure distribution.
3. Body Reynolds number.
Although potential flow theory is adequate for obtaining pressure
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distributions about simple shapes) it is expected that the three dimen-
sional electric analogy tank will be useful in obtaining pressure distri-
butions about bodies with stabilizing surfaces and propelling devices
attached. The Model will have to be of sufficient size to reduce menis-
cus difficulties.
It is essential that theoretical work be verified by detailed ex-
perimentation as extrapolation of the available information can be mis-
leading. It is anticipated that detailed boundary layer profile measure-
ments will be conducted in the field on a full scale captive balloon model
having the airship shape and stabilizing method selected by theoretical
analysis of the factors involved, as previously mentioned. Prior to this
effort, however, a review of the boundary layer work conducted by Northrup
Aircraft Corporation, and particularly the tests conducted on bodies of
revolution in the low turbulence NACA wind tunnel at Moffet Field, Calif-
ornia, will be made for possible applicability to this program.
It is expected that the boundary layer investigations conducted by
the Aerophysics Department of Mississippi State Colle gel? under Dr. Baspet
will be of considerable value in planning and executing this program,
particularly with respect to the experimental technique employed and its
relation to the various theoretical treatments.
Once the boundary layer profile is established for various stations
of a given shape and configuration, intelligent estimates of the location,
amount and distribution of suction can be made. According to Cornishil
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the section velocity is determined by an equation of the type:
Vo = (H + 2) 4)U' +14219T -
PU
where:
H = Boundary - layer shape parameter
9 = Boundary - layer momentum thickness
U = Local velocity
.r0 = Local wall shearing stress
op = Mass density.
Therefore, the suction velocity should be governed by reducing the momen-
tum thickness without letting the local shearing stress get too high, i.e.,
low suction velocities largely distributed are preferable to concentrated
large suction velocities.
The final degree of boundary layer suction must be evaluated in terms
of added complication and weight as well as reduction of overall energy
requirements and control advantages.
B. Electric Analogy Tank
The Electric Analogy Tank consists of an insulated trough partially
filled with an electrolyte; usually a weak electrolyte such as ordinary
water. An electric field is introduced into the tank by suitably placed
electrodes. When a body is placed in the field, the body's effect on
the field can be measured by a probe, tracing lines of constant voltage,
which are also the streamlines surrounding the body. Detailed analysis
of the flow surrounding any shape can be made. Such analysis can explain
the superiority of one shape or configuration over another. One will
probably be able to deduce criteria leading to optimum aerodynamic perfor-
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411,
mance. It is possible also to study the effect of a propeller and a ring
tail combination on the flow surrounding an airship configuration. The lift
curve is found by varying the angle of attack. In these cases it is ne-
cessary to adjust the trailing-edge streamline to conform with the boundary
conditions of smooth flow.
Use of the tank combines the visual advantages of a smoke tunnel with
those of a high speed computer. In many instances it can solve problems
that are impossible to solve by other techniques. Since the tank simulates
perfect fluid theory, its limitations are largely the same as the perfect
fluid theory. It is necessary to utilize viscous drag theory in combin-
ation with the tank to obtain resistance data. Progress to date at GMI
has resulted in setting up the analogy tank and computer for three dimen-
sional bodies of revolution. Test runs have been made on bodies of known
pressure distribution. The streamlines plotted by the computer compare
very favorably with known data12.
Brower has recently established a method of obtaining the normal force
on a body of revolution by use of the electric analogy tank13. This is a
rather unique solution, since the perfect fluid theory has traditionally
been plagued by WAleMbert's paradox that a body pointed at both ends im-
mersed in an inviscid fluid stream inclined to the body axis sustains no
force. Brower refined Von Karman's original work by applying the theory
to one model, having a fineness ratio of six. This accounts for a vortex
system, which is responsible for a normal force, being generated. He
recommends this technique in those cases where one shape is to be thor-
oughly investigated.
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C. Stability Analysis
The aerodynamic characteristics of a lighter-than-air vehicle are of
fundamental importance in performing a static and dynamic stability anal-
ysis since both upsetting and stabilizing forces and moments are aero-
dynamic in nature.
Lift, drag, pitching moments, sideforce, yawing moments, rotary lift
and rotary moment characteristics are all necessary for these computations.
Static stability and equilibrium conditions for the moored or free flight
condition of a lighter-than-air captive vehicle can be mathematically de-
termined by solving the three equations, listed below, simultaneously14:
1. Vertical forces:
L cosi? + D sine + (B - T cos 9
2. Horizontal forces:
D cos # - L sinp = T sin e
3. Moments about C.C. (Center of Gravity):
AY [D cos (GC - - L sin (0C - r )] +
(14,dcB AY s sin (0 -Cr.) T = mcG
where:
lift, LBS
drag, LBS
static Buoyancy, LBS
an gross weight, LBS
cable tension, LBS
3111 aerodynamic moment about Center of Buoyancy,
(Ma)CB
MCG = moment about Center of Gravity, FT. Liz
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Pr. LBS
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= dynamic moment arm of tail lift with respect to C.G. The remain-
ing terms appearing in these equations are defined in Figure 3 and apply to a
moored captive balloon. For the free flight condition many of the terms are
zero and a thrust term must be added. The results obtained from the solution
of these equations apply to the ideal case of steady-state wind conditions.
It is also, necessary to investigate the dynamic response to time variable
wind currents and gusts superimposed upon the steady wind current. .For small
displacements from the equilibrium condition, the pitching motion of the ship
must satisfy an equation of the type:
Ie '?' + m",+ mita' + in2'0 = Mg (t)
where:
Ie = effective moment of inertia, of the balloon in pitch, including
virtual inertia of the envelope and fins
m = slope of the aerodynamic pitching moment versue0C at at
1
m2? = metacentric stabilizing moment coefficient
m" = rotary derivation of pitching moment due to rate of pitch.
0 and are small angular displacements from the equilibrium balloon
altitude.
M = pitching moment due to aerodynamic forces acting during the
gust.
A similar analysis can be made for the ship in yawing motion. One important
factor in lighter-than-air work is the large virtual inertia.
A mathematical stability analysis will be made as a part Of the pre-
design analysis. In this manner it is possible to predict the effect of
component designs of different or unusual arrangements as well as to de-
fine the control necessary for flight maneuvers.
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NV
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/
/
/
/
ei
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VI. STRUCTURAL REQUIREMENTS
Careful analysis will be carried out to determine the static and dy-
namic forces applied to the envelope. A model of the vehicle will be
built and evaluation of fabric strain will be made. The work conducted
to date at
under the title of Pressure Beam Mechanics will prove use-
ful for this application. The findings of Zannoni, et al.15, will also
be of value. An operating pressure will be specified to provide adequate
resistance to the envelope bending moments caused by static buoyancy,
component weight, and aerodynamic forces in flight. Material exposure
tests have been carried out and are reported in the final report16. Two
or three of these materials will be selected early in the program for
further weathering tests on this program. A material for the envelope
will then be selected in view of these findings.
The vehicle will be provided with one or more ballonets, which are
separate, internal air chambers. Multiple ballonets may have certain de-
sirable trim and pitch control features. The main purpose of the ballonet
is to allow the lifting gas to expand or contract without changing the
size or shape of the main envelope. The expansions or contractions are
caused by changes in atmospheric pressure, temperature and the vehicle
altitude. The size, shape, location and bap.onet material will be specified
from these findings.
Past experience has shown that pressurization by centrifugal blowers
is a desirable method. This type of blower, equipped with forwardly in-
clined vanes, has a characteristic of providing constant pressure at min-
imum power. Available aircraft-type equipment will be reviewed and op-
timum equipment will be selected.
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11.
VII. SPECIAL PROBLEM AREAS
A. Field Handling and Inflation
Special consideration will be given in the preliminary design to
minimize field inflation and launching difficulties. Provisions for moor-
ing the vehicle during this period will be provided. It is expected that
shroud techniques can be developed to facilitate inflation for high wind
launchings. Figures 14. and 5 show the shroud technique as applied to
free balloon launchings for high wind conditions. Component selection
and design for the vehicle will be influenced by the requirements of this
type launching.
B. Controllability
Several new ideas regarding controllability of the airship have been
advanced. It is expected that small laboratory models will be constructed
to verify certain aerodynamic properties. Theoretical work, entitled
"Inflatible Muscles," conducted in the first phase of the program will be
beneficial in the analysis of these ideas.
C. Other Lighter-Than-Air Systems
The staff will be available to consult, discuss, and make preliminary
estimates and calculations involving other lighter-than-air tasks. Figures
6 and 7 show two lighter-than-air vehicles which are used for specific
task objectives.
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'
10* .""t ,040't PA41;:e
9;:(r
rk,k '1 ?
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VIII. PROPOSED PROGRAM
It is anticipated that the following sequence of events will take place:
Months 1 - 6
Continued theoretical analysis;
Trips to other establishments conducting related work;
Laboratory model work;
Continued review of published work;
Selection of a shape and configuration;
Review of available power plants and propellers.
Month 7
Design of model;
Continued theoretical analysis.
Month 8
Fabrication of model;
Continued theoretical analysis.
Months 9 and 10
Experimental evaluation of selected shape and configuration.
Months 11 and 12
Selection of standard aircraft engine and propeller;
Preparation of preliminary design report for small plastic airship.
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1111
DE. REFERENCES
1. General Mills, Inc. Mechanical Div. Engr. Res. and Bev. Dept. Rept.
no. 1701. Lighter-than-air concepts study, by A. A. Anderson et al.
First Progress Rept., Contract Nonr 1589(07) (May 1, 1957).
2. Ribner, H. S. The ring airfoil in nonaxial flow. J. Aeronaut. Sci.
14: 529-30 (1947).
3. nchemann, D. and J. Weber. Aerodynamics of propulsion. N.Y., McGraw-
Hill, 1953.
4. Ibid.
5. Op. cit., Ref.l.
6. Jeifertt, R. Wind tunnel tests on a 1/75 scale hull of the Goodyear-
Zeppelin airship Akron Z.R.S.4 with various ring tail surfaces. Cal-
ifornia Institute of Technology. Guggenheim Aeronaut. Lab. Rept. no.
105, part 2 (Apr. 1932); Goodyear Aircraft Corp. Rept. 5630, TI 75053
(Sept. 1, 1953).
7. Granville, P. S. The calculation of the viscous drag of bodies of
revolution. U. S. Navy. David W. Taylor Model Basin. Rept. 849
(July 1953).
8. Gertler, M. Resistance experiments on a systematic series of streams
lined bodies of revolution - for application to the design of high-
/speed submarines. U. S. Navy. David W. Taylor Model Basin. Rept.
c-297 (Apr. 1950). pp. 36-40.
9. Ibid.
10. Mississippi State College. Experimental techniques for analyzing the
turbulent boundary layer, by J. J. Cornish. Research Rept. no. 8,
Contract Nonr 578(01) (Oct. 7, 1954).
11. Misziosippi State Oollege. Prevention of turbulent separation by
suction through?Eiterforated surface, by J. J. Cornish. Research
Rept. no. 7, Contract Nonr 978(01) (Oct. 13, 1953). p. 3.
12. General Mills, Inc. Mechanical Div. Engr. Res. and Dev. Dept. Rept.
no. 1765. Lighter-than-air concepts study, by A. A. Anderson et al.
Final Rept., Contract Nonr 1589(07) (Sept. 1, 1957).
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13. Rensselaer Polytechnic Institute, Dept. Aeronaut. Engr. TR AE5701.
An electric-tank analogy solution of a linearized theory for the
normal-force on a slender closed body-of-revolution, by W. B. Brower.
Contract Al' 18(600)-499 (Feb. 8, 1957).
14. General Mills, Inc. Mechanical Div. Engr. Res. and Dev. Dept. Rept.
no. 1746. A captive balloon antenna carrier, by H. H. Henjum et al.
Final Rept., General Electric Co. Contract no. EHP-033-7201
(July 25, 1957).
15. General Development Corp. Rept. no. R50-3-1. Report on fabric devel-
opment, by P. J. Zannoni, D. R. Redpath and E. L. Shaw. Contract
AS 52-250C (Dec. 14, 1953).
16. Op. cit, Ref. 12.
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