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Naval
History and Heritage Command #NH 104274
Rockets are free-flying vehicles propelled by a high-velocity jet
of
gas. According to Newton's Third Law of Motion (conservation of
momentum), the force pushing the jet of gas to the rear of the
rocket
must be matched by an equal force pushing the rocket forward. In
this
respect, rockets are not fundamentally different from conventional
aircraft.
Aircraft
are driven by a propeller or jet engine that produces a flow of
the
surrounding air to the rear of the aircraft, driving the aircraft
forward. The gas or air flowing to the
rear of the vehicle is known as the reaction mass.
Rockets differ from aircraft in being self-contained. The gas
jet driving a rocket consists of the reaction products
from the rapid combustion of a mixture of fuel and oxidizer that
are
both stored within the rocket itself. Rockets are
also relatively simple and are capable of much faster acceleration
than
propellers or jet engines of comparable size. On the other hand, a
rocket is much less efficient, and thus has a much shorter range,
than
a conventional aircraft of the same size. The rocket must carry
both
its fuel and oxidizer, which constitute the sole reaction mass. A
conventional aircraft uses the surrounding air as oxidizer and
reaction
mass.
Rockets are not a modern invention. They have been used for entertainment in China for centuries, and the British experimented with rockets as weapons in the late 18th century, with little success. Because of the low efficiency of rockets, they were unable to carry a large enough warhead to have much effect on a military target.
Interest in rockets revived between the world wars, when researchers like Goddard in the United States and Tsiolkovsky in the Soviet Union revisited the technology with space travel in mind. Because they are self-contained, rockets are suitable for travel in the vacuum of space. However, rockets were also revisited as potential military weapons because of their simplicity and rapid acceleration. In addition, because a rocket contains its own reaction mass, it imparts no recoil to its launch mechanism, unlike a bullet or shell from a conventional gun.
Rockets are broadly classified by whether they use
solid or liquid fuel. Liquid fuel rockets generally store the fuel
and
oxidizer in separate tanks and the two are mixed in the rocket
nozzle.
This requires a more complex arrangement than solid fuel, and most
liquid oxidizers are difficult and dangerous to handle. As a
result, no
liquid-fuel rocket was used in the Pacific War. Solid-fuel rockets
use
gunpowder-like mixtures where the the oxidizer and fuel are
already
mixed; this makes for a very simple rocket that is much safer to
handle.The chief drawbacks of solid-fuel rockets is that solid
fuels are less efficient than liquid fuels and there is no easy
way to shut down the reaction once the fuel-oxidizer mixture is
ignited. The latter drawback was of no concern in most military
applications.
Firepower. The most obvious military application of rockets is as vehicles for destructive warheads. The chief advantage here is rapid acceleration without recoil. Rockets could be launched from aircraft or landing craft that could not handle the recoil of conventional artillery of equal destructive power. By the end of the war, Allied aircraft could carry up to ten 5" (127mm) rockets, giving them firepower equal to two broadsides from a destroyer. Rocket-firing fighters were first employed in the European theater and made their debut in the Pacific in the Marshalls campaign. A number of landing craft were modified to carry hundreds of rockets, giving these small craft the ability to lay down a massive bombardment on an invasion beach. However, the aircraft or landing craft then had to return to a munitions ship or a base to reload.
In March 1945 the "Tiny Tim" began to make its appearance in the
western Pacific. This was a 11.75" rocket designed at the
California
Institute of Technology that was carried primarily by Marine F4U Corsairs. Originally
designed as either a bunker
buster or an antishipping standoff weapon, this was 10'3" (3.12 m)
long
and weighted 1250 lbs (567 kg), and was fashioned out of standard
oil well piping with a 500 lb (227
kg) semi-armor-piercing bomb as
the warhead. This carried a 148.5 lb (67.3 kg) explosive
charge. To avoid damaging the launching aircraft from the back
blast,
the rocket was fitted with a lanyard that ignited the propellant
only
after the rocket had dropped some distance below the aircraft. The
weapon is credited with sinking one Japanese ship and damaging a
second, but was only deployed in small numbers.
In June-July 1945 submarine
Barb
patrolled off Karafuto and
Japan with an experimental rocket launcher
that allowed her to fire a barrage on coastal installations.
For the same reasons, rockets were employed by infantrymen to deliver antitank warheads against tanks and fortifications. The lack of recoil meant that a small team of infantrymen could launch a heavy warhead to a tactically useful range. On the other hand, the gas jet from the rocket produced a back blast that gave away the position of the antitank team, endangered other friendly infantry who carelessly positioned themselves close behind the launcher, and prevented safe use from a building or other enclosed space.
An innovation that first saw service at Saipan was the rocket-firing truck, which could fire a volley of 4.5" (114mm) rockets.
U.S. Marine Corps. Via ibiblio.org
The Japanes also made use of artillery rockets, including 200mm
rocket launchers sent to Peleliu
just prior to the Allied invasion. This weapon was 43" (109cm)
long and
carried roughly 130 pounds (60 kg) of a picric acid/flaked TNT
mixture.
The rocket was propelled by black powder, was launched
electrically,
and was not very effective, having a high dud rate, no
stabilization in
flight (which made it wobble like an American football and spoiled
its
accuracy), and a range of just 1500 yards (1400 meters). Marines
on Iwo
Jima called it the "bubbly-wubbly" for the blubbering noise it
made in
flight.
Short-Range Aircraft.
Both
the Germans and the Japanese produced short-range
aircraft
using rocket propulsion in place of conventional engines. The German Komet was a liquid-fueled interceptor armed with
conventional
weapons and theoretically capable of successfully landing after
its
flight. The Japanese Ohka or "Baka bomb" was a
solid-fueled suicide
aircraft with a large
charge of explosives that
was
carried to within range of its target (a
ship) by a
conventional bomber.
Rocket-Assisted Takeoff. Both the Allies and the Japanese experimented with the use of rockets to assist a heavy conventional aircraft in taking off from a short runway. Rockets were ideal for providing the rapid acceleration needed for just a short time during takeoff.
Antiaircraft Weapons.
Their
ability to deliver a large warhead without recoil makes rockets
attractive as antiaircraft
weapons. However, the rockets developed
during the Second World War lacked any kind of guidance and were
not
accurate enough to be successful in this role. The Germans armed
some
of their jet fighters with air-to-air rockets capable of taking
down a
heavy bomber with a
single
hit, but getting even a single hit was a
remarkable stroke of luck. The Japanese mounted surface-to-air
rockets
on their warships late in the war, but these are not thought to
have
destroyed a single Allied aircraft. Effective antiaircraft rockets
would have to await postwar advancements in guidance technology
before
they became effective.
References
ChinaLakeAlumni.org (accessed 2012-10-26)
CombinedFleet.com (accessed 2007-12-7)
Garand and
Strowbridge (1971; accessed 2011-5-30)
National Air and Space Museum (accessed 2012-10-26)
Parsch
(2004; accessed 2012-10-26)
The Pacific War Online Encyclopedia © 2007-2008, 2011-2012 by Kent G. Budge. Index
