PRELIMINARY DESIGN SPECIFICATIONS FOR A (SANITIZED) AIRSHIP

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78-03642A001300040007-6
• Release Decision: RIPPUB
• Original Classification: C
• Document Page Count: 3
• Document Creation Date: December 22, 2016
• Document Release Date: June 12, 2012
• Sequence Number: 7
• Publication Date: July 3, 1957
• Content Type: MISC

_ .rtr%rMTIAI 1W 14
Declassified in Part - Sanitized Copy Approved for Release 2012/06/14: CIA-RDP78-03642AO01300040007-6 \_
8270 GM-1
Subject PRELIMINARY DESIGN SPECIFICATIONS FOR A TWO 41AN AIRSHIP
These specifications are for minimum design conditions:
Speed - 35 mph
Range - 100 miles
Altitude - 7,000 ft
Payload - 400 lbs
Duration - 3 hrs at cruise speed
Wes,...
INTRA-C PANY CORRESPO ENCE
To At 526 Date 7-3-57 125X1
From At 526
I?A
i
The Pony Blimp made by Goodyear in 1917 was of a 35,000 cu ft class with a
3.3:1 fineness ratio. Because of new improved materials and engines, it is expected
that an airship could be successfully flown with a volume of only 20,000 ft3.
The following data is based on this size a vehicle:
Volume (20,000~)ft3 = (.056 L3)
Length 71 ft
Dia. = 24 ft
Envelope Weight = .0628 W (Vol)t/3 = .0628 x 4 x (20,000)2/3 = 190 lbs
where W = weight of material is oz/sq yd
Gross Lift at 7,000 ft = 1,070 lbs
Min. Ballonet Vol. = 20 per cent of envelope volume
Drag = CD? 1/2 )0 (Vel.) 2 (Vol,) 2/3
This formula is one that is standard for calculating the drag forces on an
airship.
The values for CD have been well established by the NACA from wind tunnel tests
and actual deacceleration tests on airships. From NACA Report No. 291, the maxi-
mum drag coefficient given for a Class "C" envelope with a fineness ratio of 3:1 is
.0339. The conclusions in NACA Report No. 394 indicate that "the addition of fins
and cars to airship models in the combinations tested increases the drag from 15
to 20 per cent at zero pitch". The data from these two reports indicate that it is
likely that the drag coefficient (CD) will be .0339 x 1.20 or .0406. In NACA Report
No. 397 the maximum CD given for an airship with a fineness ratio of 3:1 is .044.
For prelininary design, it is felt that a drag coefficient of .050 may be
safely used.
The values in the following table have been computed from the above formula
using a CD value of .0$0. The horsepower requirements are calculated from the fol-
lowing formula :
H.P. = (Drag) (Velocity)
550 x Propeller Efficiency
where the propeller efficiency used is 7
DOC- REV DATE BY
~, 4- GRID COMP DPI k-VKQ_ TYPR
r r uu l U j11 1 I I - ORNi CAMS AI- PAGES s.~ REY CL 3$
J114T V h MIYT Dew da r? . ?I.TU. Us 10.2
Declassified in Part - Sanitized Copy Approved for Release 2012/06/14: CIA-RDP78-03642AO01300040007-6
 Declassified in Part - Sanitized Copy Approved for Release 2012/06/14: CIA-RDP78-03642AO01300040007-6
-2- 7-3-57
Velocity
mph
ft sec
10
14.67
20
29.33
30
44
40
58.6
50
73.3
6o
88
Drag at
H.P. Required
Sea Level Sea Level
7,000 ft
9.38
.334
.27
37.5
2.6
2.1
84.5
9.0
7.3
150
21.3
17.2
235
41.7
33.7
338
72
58.3
The theoretical horsepower required at moderate speeds for this unit is quite
low. The main difficulty lies in selecting an engine that is sufficiently light.
Barmotive Products of San Leandro, California, manufacture an aluminum alloy
engine that has a horsepower rating of 40 and a dry weight of only 45 lbs. Such
an engine has a rather high rating for the design conditions of only 35 mph, but
it is unlikely that an engine would be available that would be any lighter and yet
have the required horsepower.
This engine, Nelson H-56, is designed for airborne operation and has been used
in the one-man "flying platform" experimental helicopters and in the Goodyear in-
flatable wing aircraft.
For a speed of 60 mph, McCulloch manufactures an engine with a rated horsepower
of 72 and a dry weight of only 76 lbs. This engine is used for drone target airplanes.
These two engines are both two-cycle air-cooled engines and are rated at 4100 rpm
which is not excessive.for a two-cycle engine.
The following is a tabulation of probable weights for an airship that would
meet the minimum design conditions:
Gross Lift at 7,000 ft altitude
Envelope weight
190 lbs
Power plant (propellers, mounts, acces-
sories, etc.), (Nelson H 56)
100
Water ballast
(7% gross lift)
75
Personnel
400
Gasoline
90
Gondola and fittings
215
1,070 lbs
1,070 lbs
Declassified in Part - Sanitized Copy Approved for Release 2012/06/14: CIA-RDP78-03642AO01300040007-6
 Declassified in Part - Sanitized Copy Approved for Release 2012/06/14: CIA-RDP78-03642AO01300040007-6
-3 -
7-3 -57
The values in this table are realistic and should not vary much for an
airship of this size.
The amount of ballast is calculated from standard operating procedure when
the amount of ballast was 4 to 7 per cent of gross load. Ninety pounds of gasoline
would last for 3-1/3 hours with the engine operating at rated horsepower. This
would provide a range of approximately 160 miles.
The need for an adequate material for its construction is the greatest deter-
rent in building this airship. Work is presently being carried on with the film
companies to develop a light, strong, gas-tight material. The goal at the present
is to laminate a Fortisan cloth with polyethylene to make a film that'can be fabri-
cated using present or improved heat-sealing techniques. With minor changes in the
presently available Fortisan-poly laminate, it is expected that a material suitable
for this model may be fabricated.
More preliminary design work has to be done on an internal catenary suspension
system to attach the control car and power plant to the envelope of the system.
Within a reasonably short period it is expected that an airship such as des-
cribed can be constructed.
~ Declassified in Part - Sanitized Copy Approved for Release 2012/06/14: CIA-RDP78-03642AO01300040007-6