IMPROVEMENTS IN PROPELLING AND STEERING SHIPS
Year: 1863

page_text: LETTERS PATENT to Arthur Auckland Leopold Pedro Cochrane, of
Portsmouth, in the County of Hants, Captain in the Royal Navy, for
the Invention of "IMPROVEMENTS IN PROPELLING AND STEERING SHIPS."
PROVISIONAL SPECIFICATION left by the said Arthur Auckland Leopold
Pedro Cochrane at the Office of the Commissioners of Patents, with his
Petition, on the 9th November 1863.
I, ARTHUR AUCKLAND LEOPOLD PEDRO COCHRANE, of Portsmouth, in the
County of Hampshire, Captain in the Royal Navy, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN PROPELLING AND STEERING
SHIPS," to be as follows:-
The improvements which constitute my Invention for propelling and steering
ships refer to that class of propelling agents which move the ship by the
reaction of a fluid discharged at the stern or other convenient part of it in
the opposite direction to that in which the vessel is required to move and
without the intervention of mechanical agents.
And these improvements consist in the mode of applying steam or other
vaporous, gaseous, or aeriform fluid or fluids suitable for the object as the agent
or agents for producing the requisite force at the stern or other suitable part
of a ship for the purpose of propelling or steering it, and I effect this object by
employing steam (by preference) as the motive power, which I obtain from
one or more boilers suitably placed in the ship and from which I convey it
through a pipe of suitable dimensions terminating in one or more jets to that

page_text: part of the ship where its power is to be employed. Although one or more jets
may be employed it will suffice to explain the operation of one jet. I place the
steam jet within a tube, which I designate the propelling tube, and which I
attach to that part of the ship from which it protrudes, the tube being of
suitable form and dimensions, leaving sufficient space between it and the steam
jet to allow air or water (as I may find most desirable) to pass in the requisite
quantity to propel the ship, suitable openings being provided to allow the air or
water to enter at one end of the propelling tube and freely to escape from it at
the other end, the air or water being put in motion in the tube by the steam jet
with considerable force and velocity. The steam acting upon the air or water
within the propelling tube discharges it with a velocity proportional to its
density, and the reaction of the force due to the velocity of discharge consti-
tutes the propelling power. In ejecting air from the propelling tube the steam
does not suffer such rapid condensation as when the steam is allowed to come
in contact with and to act immediately upon the water, by which its force is
proportionally limited. In using water, therefore, I prefer to employ a double
propelling tube, the one within the other, with free access to the ends of each,
so that the steam jet is made to expend its momentum upon the air which
passes through the inner propelling tube, and by reason of its inferior con-
ductibility slowly condenses the steam, and in its turn transmits the momen-
tum acquired from the steam to the water, and thus prolonging the action of
the steam for a longer period through the medium of the air and obtaining
the conjoint effect of the air and the water at the point of issue. In some
cases I prefer to discharge the air or water separately or both conjointly
beneath the surface of the water, and in others above the surface of the water;
and I also employ one or more jets of steam acting in one or more propelling
tubes, as the conditions of the case may require. I am by these means herein
described, which have not been hitherto employed for the purposes herein set
forth, enabled to produce the effects contemplated with greater facility, less expen-
diture of power, and consequently with greater economy than hitherto attained.

page_text: WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Ninth day of November, in the year of our Lord
One thousand eight hundred and sixty-three, in the twenty-seventh year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said Arthur Auckland Leopold Pedro Crchrane, Her special licence
that I, the said Arthur Auckland Leopold Pedro Cochrane, my executors,
administrators, and assigns, or such others as I, the said Arthur Auckland
Leopold Pedro Cochrane, my executors, administrators, and assigns, should
at any time agree with, and no others, from time to time and at all times
thereafter during the term therein expressed, should and lawfully might
make, use, exercise, and vend, within the United Kingdom of Great Britain
and Ireland, the Channel Islands, and Isle of Man, an Invention for
"IMPROVEMENTS IN PROPELLING AND STEERING SHIPS," upon the condition (amongst
others) that I, the said Arthur Auckland Leopold Pedro Cochrane, my
executors or administrators, by an instrument in writing under my, or their, or
one of their hands and seals, should particularly describe and ascertain the
nature of the said Invention, and in what manner the same was to be
performed, and cause the same to be filed in the Great Seal Patent Office
within six calendar months next and immediately after the date of the said
Letters Patent.
NOW KNOW YE, that I, the said Arthur Auckland Leopold Pedro Cochrane,
do hereby declare the nature of my said Invention, and in what manner
the same is to be performed, to be particularly described and ascertained in
and by the following statement thereof, reference being had to the Drawing
hereunto annexed, that is to say :-
The improvements which constitute my Invention for propelling and
steering ships refer to that class of propelling agents which move the ship by
the reaction of a fluid discharged at the stern or other convenient part of it
in the opposite direction to that in which the vessel is required to move and
without the intervention of mechanical agents.
And these improvements consist in the mode of applying steam or other
vapourous, gaseous, or aeriform fluid or fluids suitable for the object, as the
agent or agents for producing the requisite force at the stern or other suitable
part of a ship for the purpose of propelling or steering it. And I effect this
object by employing steam (by preference) as the motive power, which I obtain
from one or more boilers suitably placed in the ship, and from which I convey
it through a pipe of suitable dimensions terminating in one or more jets to
that part of the ship where its power is to be employed. Although one or
more jets may be employed it will suffice to explain the operation of one

page_text: jet. I place the steam jet within a tube which I designate the propelling
tube, and which I attach to the part of the ship from which it protrudes, the
tube being of suitable form and dimensions, leaving sufficient space between
it and the steam jet to allow air or water, as I may find most desirable, to pass
in the required quantity to propel the ship, suitable openings being provided
to allow the air or water to enter at the one end of the propelling tube and
freely to escape from it at the other end, the air or water being put in motion
in the tube by the steam jet with considerable force and velocity. The steam
acting upon the air or water within the propelling tube discharges it with a
velocity proportional to its density, and the reaction of the force due to the
velocity of discharge constitutes the propelling power. In ejecting air from
the propelling tube the steam does not suffer such rapid condensation as when
the steam is allowed to come into contact with and to act immediately upon
the water by which its force is proportionally limited. In using water, there-
fore, I prefer to employ a double propelling tube, the one within the other,
with free access to the ends of each, so that the steam jet is made to expend
its momentum upon the air which passes through the inner propelling tube,
and by reason of its superior conductibility slowly condenses the steam, and in
its turn transmits the momentum acquired from the steam to the water, thus
prolonging the action of the steam through the medium of the air for a longer
period and obtaining the conjoint effect of the air and the water at the point
of issue. In some cases I prefer to discharge the air or water separately or
both conjointly beneath the surface of the water and in others above the
surface of the water; and I also employ one or more jets of steam acting in
one or more propelling tubes, as the conditions of the case may require. I
am by these means (herein described), which have not been hitherto employed
for the purposes herein set forth, enabled to produce the effects contemplated
with greater facility, less expenditure of power, and consequently with greater
economy than hitherto attained.
It may be observed that the arrangements herein set forth are calculated to
avoid the loss attending the employment of steam in the steam engine, which
when tested by the dynamometer exhibits a discount amounting to about
fifty per cent of the steam generated in the boiler, and is well known to arise
from several causes combining to detract from the profitable use of the fuel.
In applying my improvements either to propelling or steering ships I adopt
steam by preference as the most convenient prime mover, the initial velocity
of which, though great, may be made available for low velocities, in which
state its momentum can be usefully employed. Under any circumstances the
aperture or jet from which steam is allowed to issue must, from the great

page_text: velocity with which the steam issues, be exceedingly small to represent a given
power, and where a large jet becomes necessary by the extent of the power
required it will be found more advantageous to employ a number of smaller
jets suitably disposed and of the same aggregate area, the circumferential
surface of the smaller jet bearing a larger proportion to its area than that of
the larger jet, and in cases where the steam jet is employed to move a fluid
by induced current the smaller jets will for that reason be preferable. In
apportioning a steam jet to perform a given service it must be made of
suitable area to discharge the quantity of water converted into steam which is
sufficient to propel the body to be moved. The quantity of water evaporated
from the boiler, the pressure at which the steam is to be maintained and used,
the corresponding volume of steam raised from the water, together with its
initial velocity, can all be readily obtained, and the area of the steam jet or
nozzle deduced therefrom. Having determined the area of the steam jet, its
effluent velocity, and the effluent velocity of the propelling fluid at the point
of discharge to give the requisite speed to the body propelled, the means for
reducing the high velocity of the steam to the velocity of the fluid discharged
has to be next considered. As the discharge of steam into water causes its
rapid condensation and incurs a wasteful expenditure of fuel, air is employed
in the intermediate space so as to prevent the contact of the steam and water.
The air being put in motion by the steam absorbs its momentum and
transmits it to the water with trifling loss, the steam expending its force upon
the air, and when condensed its molecules of water are carried forward with
the air with a velocity proportional to the density acquired. As the velocity
of the steam has thus been transferred to the air in a ratio proportional to
the weight of air put in motion, it will be found to be considerably reduced,
and by causing the air to issue from the orifice of its tube into another tube
of larger diameter a second induced current is obtained, and an additional
weight of air put in motion, and this is repeated until such a volume and weight
of air has been accumulated as to reduce the velocity to that required at the
point of issue of the propelling tube. The induced current of air through
each successive tube of the series being less than the preceding one, and the
velocity thereby diminished in proportion as the areas of the tubes are
increased, the number of tubes required to effect the object will depend upon
the velocity required at the end of the series, as seen in Fig. 1.
The object of this arrangement is to convert the elements of the momentum
existing in the steam into a practicable form for imparting its force economi-
cally to the object in view, and it is that by thus increasing the weight of the
fluid moved that the excessive velocity of the steam is rendered practically

page_text: available for propelling purposes. As it may be desirable in some cases to
effect the same object as that described without the extended series of tubes it
may be accomplished in the following manner :-Momentum being the com-
bination of weight and velocity it is obvious that by increasing the density of
the air after it has acquired its full velocity from the steam a new condition
will be obtained and the fluid will be impelled forward with a diminished
velocity, and the means which I employ for this purpose is by causing a stream
of water or other fluid denser than air to be injected into the propelling tube
after the air has acquired its velocity, and this is readily effected by inserting
a pipe fitted with a jet and a valve or stop-cock to regulate its flow into the
centre of the propelling tube and to cause it to spread itself in a thin film or
spray so as to intercept the current of air and to compel the air to absorb or
combine with it and to carry it forward to the point of issue. The reduction
of the air's velocity will be proportional to the square root of the density
attained, as seen in Fig. 2. The same effect is thus obtained as by the series
of tubes in Fig. 1. The water may either be caused to combine with the air
in successive increments or the combination may be effected at one point only,
but it is essential that the combination should be as complete as possible, so as
to insure a uniform velocity at all points in the area of the tube.
Having now described the nature of the arrangements by which I effect the
objects contemplated, viz, the adaptation of the reaction principle to the
purposes of propulsion and steering vessels, I need only remark that every
application must depend on the character and conditions of each particular
When applied for propulsion the discharge pipe may be protruded from
that part of the ship where its effort is to be employed and in a line with the
keel of the vessel, and when applied to steer a vessel the discharge pipe must
necessarily be directed in a line transversely to the keel, or at an angle if
preferred

page_text: fluid escapes into the air or into the water, as the case may be. When a
number of jets be used instead of one central one they may be applied in the
form of an argand gas burner, as dotted.
Fig. 2 represents the second arrangement, in which I is the steam jet;
K, the air tube; L, the jet of water; M, a disc or other equivalent and suit-
able device for spreading the water into a thin film or into spray. In this
arrangement the density of the air is increased in proportion to the quantity of
water injected and the velocity proportionally diminished thereby.
Having now shewn the methods of carrying my improvements into opera-
tion, I would have it understood that I do not confine myself to the precise
form or construction shewn in the Figures, as they may be varied to suit
particular cases, but what I claim is the modes of effecting the reduction of
the velocity of the air, when employed for the purposes herein described, by
means of the expansive series of tubes and by the combination of steam, air,
and water, or other gases and fluids, in the manner described, either separately
or conjointly.
In witness whereof, I, the said Arthur Auckland Leopold Pedro Cochrane,
have hereunto set my hand and seal, this Ninth day of May, in the
year of our Lord One thousand eight hundred and sixty-four.
ARTHUR L. COCHRANE. (L.S.)