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Jul 11 13 9:28 PM

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Glossary of Airship Terms





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airship: the generic term for any dirigible
or powered lighter-than-air vehicle,
including blimps and zeppelins. Until the
1930s, the word “airship” was used to refer
to both lighter-than-air and heavier-than-
air craft, but now its use generally implies
only LTA craft.

ballast: a weight carried aboard a lighter-
than-air vehicle to offset the buoyancy of
its lifting gas. Gas balloons commonly use
sand, while blimps often carry metal shot in
small canvas bags. Water has been the
traditional ballast in rigid airships. Ballast
is often expendable, being anything with
weight that can be jettisoned from the
vehicle. Ballast may be dropped by an
airship to compensate for lost lifting gas or
to ascend more quickly.

balloon: an un-powered lighter-than-air
vehicle. Balloons can derive their buoyancy
from the confinement of hot air, hydrogen,
helium, ammonia or other gas. Balloons
can be free (un-tethered and free to drift
with the wind) or tethered to the ground
(sometimes called captive or kite balloons).
ballonet: an air-filled bladder inside the
envelope of a pressure airship used to
regulate the gas pressure and maintain the
envelope shape.

blimp: a term coined in 1915 as a friendly
synonym for a pressure airship. The word is
said to have mimicked the sound made
when a man snapped his thumb on the
airship’s gas-filled envelope. It is not
derived from the description of an
apocryphal type of World War I British
airship, the “Balloon, Type B, limp.” There
was never a “Type B” nor a designation
“limp” applied to a British airship before,
during or after WW I. The term most likely
originated with Lieutenant (later Air
Commodore) A. D. Cunningham of the Royal
Naval Air Service, commanding officer of
the British airship station at Capel in
December 1915. During a weekly inspection,
Lt. Cunningham visited an aircraft hangar
to examine a “Submarine Scout” pressure
airship, His Majesty’s Airship SS-12.
Cunningham broke the solemnity of the
occasion by playfully flipping his thumb at
the gasbag and was rewarded with an odd
noise that echoed off the taut fabric.
Cunningham imitated this sound by
uttering: “Blimp!” A young midshipman,
who later became known as Air Marshal Sir
Victor Goddard, repeated the tale of this
humorous inspection to his fellow officers
in the mess hall before lunch the same day.
It is believed that by this route the word
came into common usage.

buoyancy: the ability to float due to an
object displacing a fluid medium greater
than its own weight. Buoyancy can be
controlled by the use of ballast.
catenary curtain: a fabric curtain and
metal cable structure inside the envelope of
a pressure or semi-rigid airship to which
an external gondola or control car is
attached. A catenary curtain spreads the
load across a large part of the envelope to
minimize distortions and stretching of the
gasbag. Its shape is not a true catenary in
the mathematical sense, but it is similar in
shape to an inverted rope suspended by its
ends.
cruciform fins: a vertical and horizontal
“cross-shaped” arrangement of an airship’s
empennage or tail fins (+), as opposed to tail
fins arranged in “X” configuration.
dirigible: a word that describes any
steerable or directable airship, including
blimps (pressure airships), semi-rigid
airships and zeppelins (rigid airships). The
term often is used to describe only rigid
airships, but it applies to both. Dirigible is
synonym for airship.

duralumin: originally the trade name of a
lightweight but strong alloy of aluminum
mixed with smaller amounts of copper,
magnesium, manganese, iron and silicon.
High strength with little weight made the
metal a preferred choice for building the
structure of rigid airships. Alfred Wilm
patented the formula for the alloy in 1909,
and granted an exclusive license for its
manufacture to the company Dürener
Metallwerke. The “duralumin” name was
derived from Dürener Metallwerke, and
aluminum.

dynamic lift: the vertical movement of an
airship created by aerodynamic forces
acting on the shape of the vehicle, as
opposed to static lift, which is generated by
the buoyancy of a lighter-than-air lifting
gas.

envelope: the gas bag of a pressure or semi-
rigid airship. Unlike a rigid airship gas cell,
an envelope forms an external barrier to
the elements, and when pressurized, serves
an integral role in maintaining the
airship’s shape. It also has fittings for
attaching the fins, control car and other
structural components. The envelope is
usually made of a high-strength fabric
combined with a sufficiently impermeable
barrier coating or film to minimize loss of
the buoyant gas it contains. Formerly made
of rubberized cotton, envelopes nowadays
are constructed mainly of synthetic
materials with their seams cemented, glued
or sealed.

equilibrium: a condition of relative balance
in which the forces of lift and gravity are
equal.

fineness ratio: the ratio of an airship’s
length to its diameter; the higher the
number, the longer and more slender the
airship.

gas cell: on a rigid airship, the gas-
impervious, balloon-like container of lifting
gas housed within the rigid framework.
These cells were built as light and gas-tight
as possible, using a variety of fabrics and
gas-barrier materials. They were held in
place by wire and cord netting, and their
volume could vary with atmospheric
pressure. The framework and outer cover of
a rigid airship maintained its shape, not the
outward pressure exerted by its gas cells.

gondola: a term used to describe the
variously-shaped external pods on an
airship that house engines or control
stations. The earliest airships had open-top,
boat-shaped structures holding engines and
crew. Later, these structures were enclosed,
giving rise to the terms “control car” and
“engine car” or simply “car.”

Heavier Than Air (HTA): the branch of
aeronautics that includes flight vehicles that
require air passing over an airfoil (e.g., a
wing) to generate aerodynamic lift. Such
vehicles include airplanes, gliders,
helicopters and kites, either piloted or un-
piloted.

hybrid airship: an airship with features
found in more than one type of dirigible
construction, for example, an airship
having both pressure airship and semi-rigid
airship characteristics. The term also
applies to “hybrid” vehicles that rely on a
combination of lighter-than-air (a gas cell
or envelope) and heavier-than-air
(stationary or rotary wings) principles to
achieve flight.

Lighter Than Air (LTA): the branch of
aeronautics (sometimes further confined to
aerostatics) that includes flight vehicles that
depend upon buoyancy from the
displacement of air for their lift. Such
vehicles include balloons and dirigibles of
all types, piloted or un-piloted. LTA does not
include kites (except when referring to
tethered “kite” balloons or aerostats).

non-rigid airship: another term for a
pressure airship.

pressure airship: a term used to describe an
airship whose shape is dependent on the gas
inside its envelope having a higher pressure
than is found in the atmosphere outside.
With no lifting gas in its envelope, a
pressure airship is only an empty bag on
the ground with its control car, fins and
hardware fittings the only rigid structures.
Also called a “non-rigid airship.”
pressure height: the maximum altitude at
which an airship can no longer contain its
lifting gas due to its greater pressure
compared to the surrounding atmosphere.
At this altitude, the airship’s spring-loaded
automatic valves open to relieve the
pressure or else the gas cell or envelope will
burst.

rigid airship: an airship whose shape is
maintained by an internal framework and
whose lifting gas is contained by a separate
gas cell or cells within that structure. The
external fabric covering on a rigid airship
is not completely gas-tight, but it does
protect the more delicate gas cells and other
interior components from wind and weather
and provides a degree of streamlining. Rigid
airships include zeppelins and similar
aircraft built by other companies. Even the
metal skeleton of a “rigid” airship must flex
somewhat under loads or else it would
break.

Schütte-Lanz: the rigid airship
manufacturing company founded in
Mannheim-Rheinau, Germany by Johann
Schütte and Karl Lanz. From 1909 until
shortly after WW I, it was a competitor to
the Zeppelin Company and introduced many
innovative refinements to rigid airship
design. These improvements appeared in
Zeppelins due to a wartime patent-sharing
agreement. Schütte-Lanz airships generally
were more streamlined, but their plywood
girders (used instead of duralumin) were
weakened by exposure to moisture.
semi-rigid airship: an airship with a rigid
keel but whose envelope is maintained by
gas pressure. The keel at the bottom of the
envelope is used as a support for control
car, engines, ballast and sometimes tail
surfaces.

static lift: the vertical force exerted on an
airship created solely by the buoyancy of its
lighter-than-air lifting gas, unlike dynamic
lift, which is generated by aerodynamic
forces acting on the shape of the vehicle.
streamlined: having a smooth,
aerodynamically efficient shape offering
minimal wind resistance; a classic example
is the elongated tear drop shape.

zeppelin: The often generic term for any
rigid airship, derived from the name of its
inventor and promoter, Ferdinand Graf von
Zeppelin (1838-1917). The first aircraft of of
this type flew in 1900 near Friedrichshafen,
Germany. After many trials and
tribulations, Zeppelin was able to form a
company, Luftschiffbau-Zeppelin, to
manufacture this type of airship. The word
is properly capitalized when referring to
airships produced by the Zeppelin Company,
but may be used lower-case to describe
generically any similar, cigar-shaped rigid
airship.

Blimp'n ain't easy