SPACE 2/SPACE - Library 2 - Volume 1.iso/music/664/spacshut/shuttle.txt

Text File | 1992-11-30 | 16KB | 285 lines

The first true aerospace vehicle, the Space Shuttle, takes off like a
rocket.  The winged orbiter then maneuvers around the Earth like a
spaceship, and lands on a runway like an airplane.  The Space Shuttle is
designed to carry large and heavy payloads into Earth orbit.  But unlike
earlier manned spacecraft, which were good for only one flight, the shuttle
orbiter and solid rocket boosters can be used again and again.  Only the
external tank is expended on each launch.

The Shuttle also provides a new capability, that of the checkout and repair
of unmanned satellites in orbit, or returning them to Earth for more
extensive overhauls and another launch.  Satellites that the Shuttle can
orbit and maintain operate in the fields of environmental protection,
energy, weather forecasting, navigation, fishing, farming, mapping,
oceanography, and other space-borne applications.

Many spacecraft operate in geosynchronous orbit.  This is a flight path
about 35,888 km <22,300 miles> above and aligned with the equator, with a
speed in orbit that matches that of the Earth's surface below.  From the
ground such satellites appear to hang motionless in the sky.  They are
taken into low Earth orbit by the Shuttle, then on up to altitude by an
attached Propulsion Assist Module <PAM> solid propellant stage.  The more
powerful Inertial Upper Stage <IUS> is available for heavier payloads as
well as for interplanetary missions.

Unmanned satellites such as the Hubble Space Telescope, which some
scientists estimate can see to the ends of the observable universe, and the
Long Duration Exposure Facility <LDEF>, which can demonstrate the effects
on materials and life forms of long exposure to the space environment, can
be placed in orbit, operated as long  as necessary, and returned to Earth.
The Hubble Space Telescope program is managed by NASA's Marshall Space
Flight Center, Huntsville, Alabama, and the LDEF by the NASA Langley
Research Center, Hampton, Virginia.

The ability of the Shuttle to land on a runway, unlike the expensive
parachute descent and recovery at sea techniques used in Mercury, Gemini,
and Apollo, saves both time and money.  In addition, again unlike prior
manned spacecraft, the most expensive Shuttle components can be refurbished
and made ready for another launch.  The complex and expensive orbiter is
designed to last for 100 flights minimum, and the solid rocket booster
casings, engine nozzles, parachutes, etc., for 20 launches.  The high cargo
capacity and major component reusability of the Shuttle make it unique
among space vehicles.  A Space Shuttle can be launched into equatorial
orbit from the Kennedy Space Center, and into polar orbit from Air Force
facilities at Vandenberg AFB in California.

The orbiter is the only part of the Space Shuttle which has a name rather
than a part number.  The first orbiter built was the ENTERPRISE, which was
designed for flight tests in the atmosphere rather than operations in
space.  It is now at the Smithsonian Museum at Dulles Airport outside
Washington, DC.  Four operational orbiters were built; in order, COLUMBIA,
CHALLENGER, DISCOVERY, and ATLANTIS.


Parts of the Space Shuttle

The flight components of the Space Shuttle are the winged orbiter, an
external tank, and two solid rocket boosters.  The assembled Shuttle weighs
about 2,041,168 kilograms <4,500,000 pounds> at liftoff.

The orbiter carries the crew and payload.  It is 37 meters <122 feet> long
and 17 meters <57 feet> high, has a wingspan of 24 meters <78 feet>, and
weighs from 76,000 to 79,000 kilograms <168,000 to 175,000 pounds> empty.
It is about the size and general shape of a DC-9 commercial jet airplane.
Orbiters may vary slightly from unit to unit.

Each of the orbiter's three main engines produces 1,668,000 newtons
<375,000 pounds> thrust at sea level, and 2,090,560 newtons <470,000
pounds> in the vacuum of space.  They can burn for about eight minutes,
while drawing 242,240 liters <64,000 gallons> of propellants each minute,
and are used to take the orbiter to the edge of space and a near orbital
velocity.  The Orbital Maneuvering System <OMS> engines, burning nitrogen
tetroxide for the oxidizer and monomethyl hydrazine for the fuel, supply
the last increment of velocity to reach orbit, and the thrust for in-orbit
and de-orbit maneuvers.  These propellants are fed to the engines from
tanks carried in two pods at the upper rear of the orbiter.

The orbiter carries its cargo in a cavernous payload bay 18.3 meters <60
feet> long and 4.6 meters <15 feet> wide.  The bay is flexible enough to
provide accommodations for unmanned spacecraft in a variety of shapes and
sizes, and for fully equipped scientific laboratories such as the Spacelab.
When the Shuttle is fully developed as an operational vehicle the total
payload weight can reach 29,500 kilograms <65,000 pounds>.

The huge external tank is 47 meters <154 feet> long and 8.7 meters <28.6
feet> in diameter.  It weighs a total of 756,441 kilograms <1,667,677
pounds> at liftoff.  Two inner tanks contain 529,000 liters <140,000
gallons> of liquid oxygen and 1,438,300 liters <380,000 gallons> of liquid
hydrogen.  The tank feeds these propellants to the main engines of the
orbiter throughout the ascent into near-orbit.  It is discarded and falls
into an uninhabited stretch of ocean, the only major Shuttle component
expended on each launch.

The two solid rocket boosters are each 45.5 meters <149.1 feet> high and
3.7 meters <12.2 feet> in diameter.  Each weighs 589,670 kilograms
<1,300,000 pounds>.  Their solid propellant consists of a mixture of
aluminum powder, aluminum perchlorate powder, and a dash of iron oxide
catalyst, held together with a polymer binder.  They produce 11,787,000
newtons <2,658,000 pounds> thrust each at liftoff.  Together with the three
main engines on the orbiter, this provides a total liftoff thrust of almost
28,912,000 newtons <6.5 million pounds>.


Crew and Passenger Accommodations

The two to seven person crew occupies a two level cabin at the forward end
of the orbiter.  They operate the vehicle from the upper level, the flight
deck.  The flight controls for the mission commander and pilot are at the
front.  A station at the rear, overlooking the cargo bay through two
windows, contains the controls a mission specialist astronaut uses to
operate the Remote Manipulator System arm which handles some of the cargo.
Mission operations displays and controls are on the right side of the
cabin, and payload controls on the left.  The latter are operated by
payload specialists, who are usually not career astronauts.  The living,
eating, and sleeping area for off-duty crew members, called the middeck, is
located below the flight deck.  It contains prepackaged food, a toilet,
bunks, and other amenities.

Space Flight is no longer limited to intensively trained, physically
perfect astronauts.  Experienced scientists and technicians can fly in
support of their payloads.  Crew members experience a designed maximum
gravity load of 3g during launch, and less than 1.5g during reentry.  These
accelerations are about one-third the levels experienced on previous manned
flights.  Many other features of the Space Shuttle, such as a standard sea-
level atmosphere, will make space flight more comfortable for the non-
astronaut of the future.


Typical Shuttle Mission

The rotation of the Earth has a significant bearing on the payload
capabilities of the Space Shuttle.  A due east launch from the Kennedy
Space Center in Florida uses the Earth's rotation as a launch assist, since
the ground is turning to the east at that point at a speed of 1,473
kilometers <915 miles> per hour.  This permits payloads on the fully
developed Shuttle to weigh as much as 29,500 kilograms <65,000 pounds> when
launched from KSC.

A launch to the south into polar orbit from Vandenberg AFB in California,
without the help of this speed of rotation of the Earth, limits a Shuttle
payload to about 18,000 kilograms <40,000 pounds>.

Spacecraft and other items of payload arrive at the Kennedy Space Center
and are assembled and checked out in special buildings before being loaded
into the orbiter.  Each Shuttle arrives as a set of component parts.  The
solid rocket booster propellant segments are received and checked out in a
special facility, then taken to the Vehicle Assembly Building <VAB> and
stacked on a mobile launcher platform to form two complete rockets.  The
external tank is received and prepared for flight in the VAB, then mated to
the solid rockets.  An orbiter is checked out in the Orbiter Processing
Facility, then moved to the VAB and attached to the external tank.  A giant
crawler-transporter picks up the mobile launcher platform and the assembled
Shuttle and takes them to the pad.  The Shuttle remains on the platform
until liftoff.

The orbiter's main engines ignite first and build to full power before the
huge solid rockets ignite and liftoff occurs.  The solid rockets burn out
after about two minutes, are separated from the tank, and parachute into
the ocean about 258 kilometers <160 miles> from land.  Two special recovery
ships pull the parachutes out of the water and tow the rocket casings to
land, where they are refurbished and sent back to the manufacturer to be
refilled with propellant.  The orbiter continues to the edge of space - a
total of about eight minutes of burn-time on the three main engines, where
the empty tank is discarded.  The two OMS engines then burn to inject the
orbiter alone into low Earth orbit.  The tank continues around the world
and breaks up over uninhabited ocean as it reenters the atmosphere.  Later
OMS burns raise or adjust the orbit as necessary.  A typical Shuttle
mission lasts from two to ten days, with a future growth potential of up to
30 days.

After deploying the payload spacecraft, operating the onboard scientific
instruments, taking observations, etc., the orbiter renters the
atmosphere and lands, normally at either the Kennedy Space Center or
Edwards AFB in California.  Unlike prior manned spacecraft, which followed
a ballistic trajectory, the orbiter has a crossrange capability <can move
to the right or left off the straight line of its entry path> of about
2,045 kilometers <1,270 miles>.  The landing speed is from about 341 to 364
kilometers <212 to 226 miles> per hour.  The orbiter is immediately "safed"
by a ground crew with special equipment, the first step in the process
which will result in another launch of this particular orbiter.


Spacelab: Science in Orbit

Periodically the Shuttle is scheduled to carry a complete scientific
laboratory called "Spacelab" into Earth orbit.  Two complete Spacelabs
<plus instrument-carrying platforms exposed to space, called "pallets">
have been built by the European Space Agency <ESA>, which paid for the
development expense and manufacturing costs of the first one.  NASA
purchased the second unit.  A Spacelab is similar to a small but well-
equipped laboratory on Earth, but has been designed for zero-gravity
operation.  It provides a shirt-sleeve environment where up to four people,
who eat and sleep in the orbiter, can perform scientific tests utilizing
the high vacuum and micro gravity of orbital space, and make observations
above the obscuring atmosphere.

Spacelab personnel are men and women of many nations, experts in their
fields, who must be in reasonably good health.  They are required to have
only a few weeks of space flight training, but many have spent years
preparing to perform their experiments in orbit.

Most of the experiments on a given Spacelab mission are devoted to a single
broad field, such as medicine, manufacturing, astronomy, space physics or
pharmaceuticals.  Four successful Spacelab missions have been flown to
date.  One of these was an all-pallet configuration, where all the
instruments were exposed to space and operated from inside the orbiter.

A Spacelab and its pallets remain attached to the orbiter throughout the
mission.  After landing, the Spacelab is removed from the orbiter and the
instruments changed for the next planned field of study.  A Spacelab has an
estimated life of 50 missions.


The Spacelab program results from a worldwide interest in the study of
science and technology in the space environment, and is an example of how
the costs of such ventures can be shared internationally.  The
participating ESA nations are Belgium, Denmark, France, Italy, The
Netherlands, Spain, Switzerland, United Kingdom, and the Federal Republic
of Germany.  Austria participated as an associate member of ESA.


Space Applications

The Space Shuttle is scheduled to carry the component parts of the Space
Station into orbit, and to provide an initial base for assembly operations.
People operating inside the micro gravity of a Space Station can produce
products difficult or impossible to make on the Earth's surface.  They
could also build space structures designed to provide services to Earth,
such as power generation from sunlight.  In addition, such orbiting
stations provide astronomers and other scientists an instrumented platform
above the atmosphere from which they can study the composition and
structures of our universe in ways not possible on the ground.

Other applications are the economical manufacturing in zero gravity of
presently very expensive medical drugs, or glass for lenses,or electronic
crystals of unrivaled purity and size, as well as various alloys,
composites, and metallic materials impossible to produce on Earth.  Drugs,
metals, glass and electronic crystals will first be manufactured in pilot
programs on board various Spacelab missions, proving the concept before
larger scale operations begin.

The Space Shuttle is overall the most capable vehicle built since the space
program began, and will be the major means of bringing the benefits of
space utilization to humanity throughout the rest of the 20th century.


Orbiter Insulation

A special silicon-based insulation in the form of 100 square inch <average>
tiles serves as the primary heat shield for the orbiter.  This material
sheds heat so readily that one side can be held in bare hands while the
opposite side is red-hot.  These lightweight tiles are made to survive
temperatures of up to 1,260 degrees Celsius <2,300 F>.  Previous manned
spacecraft used heat shields that ablated - flaked away in small pieces to
carry off heat from the surface - during the fiery entry into Earth's
atmosphere.  They tended to be heavy and were not reusable.


Improved Space Suit & Unique Rescue System Developed For The Shuttle

An improved space suit and an independent rescue unit have been developed
for the Shuttle crew by the Johnson Space Center, Houston, Texas.  Johnson
is responsible for mission planning, and provides ground control and
support during each flight.  The space suit is for use when working outside
the pressurized crew or Spacelab compartments.


Unlike earlier suits, each of which was tailored to an astronaut's specific
measurements, these come in small medium, and large sizes, and can be
adjusted to fit both men and women.  A suit comes in two parts - upper
torso and pants - and each part is pressure sealed, unlike previous suits
that were zipper-sealed at the waist.  The material used for the elbow,
knee, and other joints is a fabric that allows easier movement, and costs
and weighs less than the neoprene rubber joints of earlier units.  Each
suit has an integral life support system rather than the previously
required set of connected tanks carried on the back.

For rescue operations, including an emergency transfer between vehicles,
most of the crew will enter plastic life support modules which are then
pressurized from an internal life support system.  They  form spheres 86.36
centimeters <34 inches> in diameter when inflated, and have built-in
communications systems.  The suited astronauts move the spheres through
airless space.