3. Having now cleared our way of these necessary preliminaries, we may
at once proceed to speak of the manufacture of ROCKETS; first, of what a
rocket is, and then of how it is made. There is nothing like starting
with a good distinct notion of what we have to make before we set to
work to make it. It is said of a person who was asked by his friend to
give him a logical definition of a house, that he at once replied that
“_it was a thing with a chimney_;” which definition, being equally
applicable to a moderator lamp and a steam-engine, can hardly be
considered exhaustive in the case of a house; and, in like manner, if we
start with the idea that a rocket is _a thing that goes up in the air_,
we shall not have any very tangible model of rocket excellence before us
as a guide in our work. It is, however, very true that some rockets
which we see can only be properly and faithfully described as things
which go up in the air, for they no more deserve the name of a rocket
than does a child’s kite or a cock-sparrow, either of which would come
equally well under the above definition. But let us see whether we can
arrive at something a little more accurate. A rocket we will define as
_a species of firework which, when properly fastened to a stick of a
certain size and weight suspended with its mouth downwards, and ignited,
ascends into the air by the force of its own combustion, rises
majestically to its proper height, throwing out, from the beginning to
the end of its course, a rich and uniform tail of sparks, and at the
extreme range of its flight giving birth to a cluster of stars, or
shower of fiery rains, or other decorations, as they are called, which
should burn long enough to be well seen, and not disappear almost at the
moment of their appearance_. This is what every rocket should be when
fired; and let me beg of you not to stop short of attaining this
excellence, for perseverance will give you experience, and with the aid
of these two you need despair of nothing. When I had been puzzled and
misled by all the books and information on the subject that I could
procure, and had met with nothing but failure in all my attempts, I set
myself to work to make my own experiments in a new direction, on the
supposition that I understood, to a certain extent, the principle on
which success depended. And well do I remember my delight at seeing a
rocket of my own production scramble up into the air in a very
undignified and disorderly manner, and there perform certain nervous
evolutions which I will defy any pen to describe or pencil to depict.
But although its performance was erratic and laughable, I had conquered;
the key from that moment was in my own hands; and soon, after careful
consideration and a few more experiments, I managed to produce a rocket
of which I saw no reason to be ashamed.
I have stated above what appearance a good rocket should present to the
eyes of a spectator when fired; I am now about to state what appearance
it should present to its manufacturer before being fired—in fact, what
it is that he has to make. _It is a strong cylindrical case, made of
pasted brown paper and imperial board, contracted near one of its ends
in order to form a narrow aperture, and filled with a certain
composition in such a manner that a long narrow cavity is left in its
centre, extending almost throughout its whole length._ This is what I
shall call the rocket, for the ascending power lies solely in this part;
the head, being an after-addition, will be spoken of it in its proper
place, and not allowed to interfere here. In the annexed woodcut A A
represents the exterior diameter of the case; B B, the interior diameter
of the same; C C, the long cavity extending from the mouth up the centre
of the composition, which cavity is called the “soul” of the rocket; D D
D, the composition with which the remainder of the case is filled. The
lower of the two C’s represents the mouth, or “choke” as it is called,
at which all the combustion that goes on in the rocket has to find its
vent. When a light is applied to the mouth of the rocket, the whole
surface of the soul of the rocket is set on fire at once, and on this
depends its power of ascent; for so large a quantity of fire having to
make its escape through so narrow an aperture and meeting with
considerable resistance from the external air, makes the rocket recoil
in a direction opposite to that of its mouth, until all the combustible
material which it contains is consumed. This is a broad outline of the
principle upon which rockets ascend. It will be unnecessary for me to
dive deeper into theories here, for I am sure that you will be anxious
for me to come to practical details without further delay.
[Illustration:
Fig. 1.
]
Among other things in my prefatory remarks I stated that firework-making
need not be an expensive recreation, but you must bear in mind that
nothing is easier than to make it expensive, and that we must adopt some
strictly economical system of operation. Since rockets are the most
scientific of all fireworks, and the apparatus necessary for making them
is more costly than that for making any other kind of firework, we must
do all that we can to bring their manufacture within reach of the
amateur. There are many books, and I dare say many persons, that will
tell you that you cannot hope to produce a good rocket unless you have a
mould proper for the purpose made either of gun-metal or of some hard
wood. I believe that I am right in telling you that such a piece of
apparatus varies in cost from 3_l._ to 10_l._, but I also know that I am
right in assuring you that a rocket, in every respect equal to many that
are rammed in a mould, may be produced without this expensive luxury. I
can only say that I _never_ use a mould, and my belief is that the
workmen employed by professional pyrotechnists are, for the most part,
only too glad to dispense with its use, for it is of importance to them
to ram the greatest possible number of rockets in a given time, and if
they were to be delayed by having to unscrew and screw a mould before
and after filling each case, half their time and its value would be lost
to them. I use, and recommend you also to use, a simple steel spindle
let firmly into a wooden block, and if your cases are made strongly
enough you will be able to produce all that your ambition will picture
to you by means of this inexpensive apparatus, and without the help of
the mould.
But before we speak of the size and proportions of this spindle it will,
of course, be necessary for us to determine the size of the rocket which
we intend to produce. Now, the rocket that I recommend you to make, as
being the most generally useful and economical, is that which the
professionals call the _¼lb. rocket_. You will bear in mind that this
name is not intended to signify that the rocket when finished will weigh
a quarter of a pound, but that its interior diameter is equal to the
exterior diameter of a leaden ball weighing 4oz. You will find, I am
sure, that the capabilities of this size of rocket, when properly made,
will satisfy you for all ordinary purposes, and, taking this for
granted, I shall now proceed to speak of this particular size only, in
order to prevent the possibility of confusion.