Post World War II
At the end of World War II, competing Russian, British, and U.S. military and
scientific crews raced to capture technology and trained personnel from the
German rocket program at
Peenem�nde.
Russia and Britain had some success, but the United States benefited the most. The US
captured a large number of German rocket scientists (many of whom were members
of the
Nazi Party, including von Braun) and brought them to the United States as
part of
Operation Paperclip.
In America, the same rockets that were designed to rain down on
Britain were used instead by scientists as research vehicles for developing
the new technology further. The V-2 evolved into the American
Redstone rocket, used in the early space program.
After the war, rockets were used to study high-altitude conditions, by radio
telemetry
of temperature and pressure of the atmosphere, detection of
cosmic rays, and further research; notably for the
Bell X-1 to
break the sound barrier. This continued in the U.S. under von Braun and the
others, who were destined to become part of the U.S. scientific complex.
Independently, research continued in the
Soviet
Union under the leadership of the chief designer
Sergei Korolev.
With the help of German technicians, the V-2 was duplicated and improved as the
R-1,
R-2 and
R-5 missiles. German designs were abandoned in the late 1940s, and the
foreign workers were sent home. A new series of engines built by Glushko and
based on inventions of
Aleksei Mihailovich Isaev formed the basis of the first ICBM, the
R-7.
The R-7 launched the first satellite, and
Yuri
Gagarin, the first man into space and the first lunar and planetary probes,
and is still in use today. These events attracted the attention of top
politicians, along with more money for further research.
Rockets became extremely important militarily in the form of modern
intercontinental ballistic missiles (ICBMs) when it was realised that
nuclear weapons carried on a rocket vehicle were essentially not defensible
against once launched, and ICBM/Launch vehicles such as the R-7,
Atlas and
Titan became the delivery platform of choice for these weapons.
Fueled partly by the
Cold War,
the 1960s became the decade of rapid development of rocket technology
particularly in the Soviet Union (Vostok,
Soyuz,
Proton) and in the United States (e.g. the
X-15
and
X-20 Dyna-Soar
aircraft). There was also significant research in other countries, such as
Britain, Japan, Australia, etc. and their growing use for
Space exploration, with pictures returned from the far side of the
Moon and unmanned
flights for
Mars exploration.
In America the manned programmes,
Project Mercury,
Project Gemini and later the
Apollo programme culminated in 1969 with the first manned
landing
on the moon via the
Saturn V,
causing the New York Times to retract their earlier editorial implying that
spaceflight couldn't work:
"Further investigation and experimentation have confirmed the findings of
Isaac Newton in the 17th century and it is now definitely established that a
rocket can function in a vacuum as well as in an atmosphere. The Times regrets
the error."
In the 1970s America made further lunar landings, before abandoning the
Apollo launch vehicle. The replacement vehicle, the partially reusable 'Space
Shuttle' was intended to be cheaper, but this large reduction in costs was
largely not achieved. Meanwhile in 1973, the expendable
Ariane programme was begun, a launcher that by the year 2000 would capture
much of the geosat market.
Current day
Rockets remain a popular military weapon. The use of large battlefield
rockets of the V-2 type has given way to guided
missiles. However rockets are often used by
helicopters
and light aircraft for ground attack, being more powerful than
machine
guns, but without the recoil of a heavy
cannon. In the
1950s there was a
brief vogue for
air-to-air rockets, ending with the
AIR-2 'Genie'
nuclear rocket,
but by the early
1960s these had largely been abandoned in favor of
air-to-air missiles.
Economically, rocketry is the enabler of all
space technologies particularly satellites, many of which impact people's
everyday lives in almost countless ways,
satellite navigation,
communications satellites and even things as simple as
weather satellites.
Scientifically, rocketry has opened a window on our universe, allowing the
launch of
space probes to explore our
solar system,
satellites to view the Earth itself, and space-based
telescopes to obtain a clearer view of the rest of the
universe.
However, in the minds of much of the public, the most important use of
rockets is perhaps
manned spaceflight. Vehicles such as the
Space
Shuttle for scientific research, the
Soyuz for orbital tourism and
SpaceShipOne for suborbital tourism may show a trend towards greater
commercialisation of manned rocketry,
away from government funding, and towards more widespread
access to space.
Types
There are many different types of rockets, and a comprehensive list of the
basic engine types can be found in
rocket engine � the vehicles themselves range in size from tiny
models
such as
water rockets or small solid rockets that can be purchased at a
hobby
store, to the enormous
Saturn V
used for the
Apollo program, and in many different vehicle types such as
rocket cars
and
rocket planes.
Most current rockets are chemically powered rockets (usually
internal combustion engines,
but some employ a decomposing
monopropellant) that emit a hot
exhaust
gas. A chemical
rocket engine can use gas propellant,
solid propellant,
liquid propellant, or a
hybrid mixture of both solid and liquid. With combustive propellants a
chemical reaction is initiated between the
fuel and the
oxidizer in the
combustion
chamber, and the resultant hot gases accelerate out of a
nozzle (or
nozzles) at the rearward-facing end of the rocket. The
acceleration of these gases through the engine exerts force ("thrust") on
the combustion chamber and nozzle, propelling the vehicle (in accordance with
Newton's Third Law). See
rocket engine for details.
Rockets in which the heat is supplied from a source other than a propellant,
such as
solar thermal rockets, can be classed as
external combustion engines. Other examples of external combustion rocket
engines include most designs for nuclear powered rocket engines. Use of
hydrogen as
the propellant for such engines gives very high exhaust velocities (around 6-10
km/s).
Steam rockets, are another example of non chemical rockets. These rockets
release very hot water through a nozzle
where, due to the lower pressure there, it instantly flashes to high velocity
steam, propelling the rocket. The efficiency of
steam as a rocket
propellant is relatively low, but it is simple and reasonably safe, and the
propellant is cheap and widely available. Most steam rockets have been used for
propelling land-based vehicles but a small steam rocket was tested in 2004 on
board the UK-DMC
satellite,
as an alternative, with higher performance, to
cold gas thrusters for attitude jets. There are even proposals to use steam
rockets for interplanetary transport using either nuclear or solar heating as
the power source to vaporize water collected from around the
solar system, at system costs that are claimed to be greatly lower than
hydrogen-based systems.
Uses
Rockets or other similar
reaction devices carrying their own propellant must be used when there is no
other substance (land, water, or air) or force (gravity,
magnetism,
light) that a
vehicle may
usefully employ for propulsion, such as in space. In these circumstances, it is
necessary to carry all the
propellant
to be used.
However, they are also useful in other situations:
Weaponry
In many military weapons, rockets are used to propel
payloads to
their targets. A rocket and its payload together are generally referred to as a
missile, especially when the weapon has a
guidance system.
Science
Sounding rockets
are commonly used to carry instruments that take readings from 50 kilometers
(30 mi) to 1,500 kilometers (930 mi) above the surface of the Earth, the
altitudes between those reachable by
weather balloons and satellites.
Launch
Due to their high exhaust velocity (Mach ~10+), rockets are particularly
useful when very high speeds are required, such as orbital speed (Mach 25+).
Indeed, rockets remain the only way to launch
spacecraft
into orbit.
They are also used to rapidly accelerate spacecraft when they change orbits or
de-orbit for
landing. Also, a rocket may be used to soften a hard parachute landing
immediately before touchdown (see
Soyuz spacecraft). Spacecraft delivered into orbital trajectories become
artificial
satellites.
Hobby, sport and entertainment
Hobbyists build and fly
Model
rockets of various types and rockets are used to launch both commercially
available
fireworks and professional fireworks displays.
Hydrogen peroxide rockets are used to power
jet packs,
and have been used to power
cars
and a rocket car holds the all time
drag
racing record.
Components of a rocket
Rockets at minimum have a place to put propellant (such as a
propellant tank), one or more
rocket engines and
nozzle,
directional stabilization device(s) (such as
fins,
attitude jets or engine
gimbals) and a
structure (typically
monocoque)
to hold these components together. Rockets intended for high speed atmospheric
use also have an
aerodynamic fairing such as a
nose cone.
As well as these components, rockets can have any number of other components,
such as wings (rocketplanes),
wheels (rocket
cars), even, in a sense, a person (rocket
belt).
Noise
For all but the very smallest sizes, rocket exhaust compared to other engines
is generally very noisy. As the
hypersonic
exhaust mixes with the ambient air,
shock waves
are formed. The
sound intensity from these shock waves depends on the size of the rocket.
The sound intensity of large rockets could potentially kill at close range.
The
Space
Shuttle generates over 200
dB(A) of noise around its base. A
Saturn V
launch was detectable on
seismometers a considerable distance from the launch site.
Generally speaking, noise is most intense when a rocket is close to the
ground, since the noise from the engines radiates up away from the plume, as
well as reflecting off the ground. This noise can be reduced somewhat by flame
trenches with roofs, by water injection around the plume and by deflecting the
plume at an angle.
For manned rockets various methods are used to reduce the sound intensity for
the passengers as much as possible, and typically the placement of the
astronauts far away from the rocket engines helps significantly. For the
passengers and crew, when a vehicle goes supersonic the sound cuts off as the
sound waves are no longer able to keep up with the vehicle.
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