第 9 节
作者:疯狂热线      更新:2021-03-16 00:35      字数:9322
  permanent       shape    by  means     of  an   aluminium      framework。      A   serious
  disadvantage to this type of craft is that it lacks the portability necessary
  for military purposes。 It is true that the vessel can be taken to pieces; but
  not   quickly。   The   NON…RIGID   type;   on   the   other   hand;   can   be   quickly
  deflated; and the parts of the car and engine can be readily transported to
  the nearest balloon station when occasion requires。
  In   the   SEMI…RIGID   type   of   air…ship   the   vessel   is   dependent   for   its
  form partly on its framework and partly on the form of the gas envelope。
  The under side of the balloon consists of a flat rigid framework; to which
  the planes are attached; and from which the car; the engine; and propeller
  are suspended。
  As the rigid type of dirigible is chiefly advocated in Germany; so the
  semi…rigid craft is most popular in France。 The famous Lebaudy air…ships
  are good types of semi…rigid vessels。 These were designed for the firm of
  Lebaudy Freres by the well…known French engineer M。 Henri Julliot。
  In November; 1902; M。 Julliot and M。 Surcouf completed an air…ship
  for M。 Lebaudy which   attained a speed   of nearly 25   miles an hour。 The
  craft; which was named Lebaudy I; made many successful voyages; and in
  1905   M。   Lebaudy   offered   a   second   vessel;   Lebaudy   II;   to   the   French
  Minister   of   War;   who   accepted   it   for   the   French   nation;   and   afterwards
  decided to order  another  dirigible;  La Patrie; of   the same   type。  Disaster;
  however; followed these air…ships。 Lebaudy I was torn from its anchorage
  during a heavy gale in 1906; and was completely wrecked。 La Patrie; after
  travelling in 1907 from Paris to Verdun; in seven hours; was; a few days
  later;   caught   in   a   gale;   and   the   pilot   was   forced   to   descend。   The   wind;
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  however;   was   so   strong   that   200   soldiers   were   unable   to   hold   down   the
  unwieldy craft; and it was torn from their hands。 It sailed away in a north…
  westerly      direction     over     the   Channel      into    England;      and    ultimately
  disappeared   into   the   North   Sea;   where   it   was   subsequently   discovered
  some days after the accident。
  Notwithstanding these disasters the French military authorities ordered
  another      craft   of   the   same     type;    which     was    afterwards      named      the
  Republique。 This vessel made a magnificent flight of six and a half hours
  in 1908; and it was considered to have quite exceptional features; which
  eclipsed the previous efforts of Messrs。 Julliot and Lebaudy。
  Unfortunately;   however;   this   vessel   was   wrecked   in   a   very   terrible
  manner。      While     out   cruising    with   a   crew    of  four   officers    one   of   the
  propeller   blades   was   suddenly   fractured;   and;   flying   off   with   immense
  force; it entered the balloon; which it ripped to pieces。 The majestic craft
  crumpled up and crashed to the ground; killing its crew in its fall。
  In the illustration facing p。 17; of a Lebaudy air…ship; we have a good
  type of the semi…rigid craft。 In shape it somewhat resembles an enormous
  porpoise;      with    a  sharply…pointed        nose。    The    whole     vessel    is  not   as
  symmetrical as a Zeppelin dirigible; but its inventors claim that the sharp
  prow facilitates the steady displace ment of the air during flight。 The stern
  is rounded so as to provide sufficient support for the rear planes。
  Two   propellers   are   employed;   and   are   fixed   outside   the   car;   one   on
  each   side;   and   almost   in   the   centre   of   the   vessel。   This   is   a   some   what
  unusual   arrangement。         Some   inventors;       such   as  Mr。   Spencer;     place    the
  propellers at the prow; so that the air…ship is DRAWN along; others prefer
  the   propeller   at   the   stern;   whereby   the   craft   is   PUSHED   along;   but   M。
  Julliot chose the central position; because there the disturbance of the air is
  smallest。
  The   body   of   the   balloon   is   not   quite   round;   for   the   lower   part   is
  flattened and rests on a rigid frame from which the car is suspended。 The
  balloon is divided into three compartments; so that the heavier air does not
  move to one part of the balloon when it is tilted。
  In    the   picture    there   is   shown     the   petrol    storage…tank;      which     is
  suspended immediately under the rear horizontal plane; where it is out of
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  danger of ignition from the hot engine placed in the car。
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  CHAPTER XII A Non…rigid Balloon
  Hitherto we have described the rigid and semi…rigid types of air…ships。
  We have seen that the former maintains its shape without assistance from
  the gas   which inflates   its   envelope  and supplies   the  lifting   power;   while
  the latter; as its name implies; is dependent for its form partly on the flat
  rigid   framework       to  which    the  car   is  attached;   and   partly   on  the   gas
  balloon。
  We   have   now   to   turn   our   attention   to   that   type   of   craft   known   as   a
  NON…RIGID BALLOON。 This vessel relies for its form ENTIRELY upon
  the pressure of the gas; which keeps the envelope distended with sufficient
  tautness to enable it to be driven through the air at a considerable speed。
  It will at once be seen that the safety of a vessel of this type depends
  on the maintenance of the gas pressure; and that it is liable to be quickly
  put out of action if the envelope becomes torn。 Such an occurrence is quite
  possible   in   war。  A   well…directed   shell   which   pierced   the   balloon   would
  undoubtedly  be   disastrous to   air…ship   and   crew。  For  this   reason the   non…
  rigid balloon does not appear to have much future value as a fighting ship。
  But; as great speed can be obtained from it; it seems especially suited for
  short overland voyages; either for sporting or commercial purposes。 One
  of   its   greatest   advantages   is   that   it   can   be   easily   deflated;   and   can   be
  packed away into a very small compass。
  A   good    type   of  the  non…rigid    air…ship   is  that  built  by   Major    Von
  Parseval;     which    is  named     after   its  inventor。   The    Parseval    has   been
  described as 〃a marvel of modern aeronautical construction〃; and also as
  〃one of the most perfect expressions of modern aeronautics; not only on
  account of its design; but owing to its striking efficiency。
  The balloon has the elongated form; rounded or pointed at one end; or
  both ends; which is common to most air…ships。 The envelope is composed
  of a rubber…texture fabric; and externally it is painted yellow; so that the
  chemical properties of the sun's rays may not injure the rubber。 There are
  two   smaller   interior   balloons;   or   COMPENSATORS;   into   which   can   be
  pumped air by means of a mechanically…driven fan or ventilator; to make
  up    for  contraction     of  the  gas   when     descending     or  meeting     a  cooler
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  atmosphere。   The   compensators   occupy   about   one…quarter   of   the   whole
  volume。
  To secure the necessary inclination of the balloon while in flight; air
  can be transferred from one of the compensators; say at the fore end of the
  ship; into the ballonet in the aft part。 Suppose it is desired to incline the
  bow   of   the   craft   upward;   then   the   ventilating   fan   would   DEFLATE   the
  fore    ballonet    and   INFLATE       the   aft  one;   so  that  the   latter;  becoming
  heavier; would lower the stern and raise the bow of the vessel。
  Along   each   side   of   the   envelope      are   seen   strips   to   which   the  car
  suspension…cords         are   attached。    To   prevent     these   cords    being    jerked
  asunder; by the rolling or pitching of the vessel; horizontal fins; each 172
  square feet in area; are provided at each side of the rear end of the balloon。
  In   the   past   several   serious   accidents   have   been   caused   by   the   violent
  pitching of the balloon when caught in a gale; and so severe have been the
  stresses on the suspension cords that great damage has been done to the
  envelope; and the aeronauts have been fortun