Imagine that you are sitting in a seat on your back inside
a spacecraft atop a large rocket
filled with a million pounds of explosive fuel. You are
wearing your space
suit. You hear the noises of various pumps cycling on and
off around you. As the clock hits T minus 6 seconds, you feel
an enormous vibration shaking you violently and hear a loud
roar; the main engines have ignited.
At T minus 0 seconds, the solid rocket boosters ignite and
you are on your way. The cabin shakes violently as you lift
off, but in 8.5 minutes you will be in outer space, perhaps on
your way to the International
Space Station. This is how a launch of the Space Shuttle
has been described. But what is the space shuttle? What makes
it different from any other spacecraft? How does it work? In
this edition of How Stuff
Works, we will examine the fascinating world of the
space shuttle including its parts, design and various systems!
Photo courtesy NASA Liftoff of the space shuttle
A Brief History of the Space Shuttle Near
the end of the Apollo space program, NASA officials were
looking at the future of the American space program. At that
time, the rockets used to place astronauts and equipment in
outer space were one-shot disposable rockets. What they needed
was a reliable, but less expensive, rocket, perhaps one that
was reusable. The idea of a reusable "space shuttle" that
could launch like a rocket but deliver and land like an airplane
was appealing and would be a great technical achievement.
Photo courtesy McDonnell Douglas
Corporation Artist's concept
of a space shuttle with a manned booster and
Photo courtesy NASA NASA's original concept of the space
NASA began design, cost and engineering studies on a space
shuttle. Many aerospace companies also explored the concepts.
The concepts varied from a reusable, manned booster concept
(shown above) to a shuttle lifted by solid rockets. In 1972,
President Nixon announced that NASA would develop a reusable
space shuttle or space transportation system (STS).
NASA decided that the shuttle would consist of an orbiter
attached to solid rocket boosters and an external fuel tank
because this design was considered safer and more cost
effective. NASA awarded the prime contract to Rockwell
At that time, spacecraft used ablative heat shields
that would burn away as the spacecraft re-entered the Earth's
atmosphere. However, to be reusable, a different strategy
would have to be used. The designers of the space shuttle came
up with an idea to cover the space shuttle with many
insulating ceramic tiles that could absorb the heat of
re-entry without harming the astronauts (see Question
308: Meteors burn up when they hit the earth's atmosphere. Why
doesn't the space shuttle? for details).
Remember that the shuttle was to fly like a plane, more
like a glider, when it landed. A working orbiter was built to
test the aerodynamic design, but not to go into outer space.
The orbiter was called the Enterprise after the "Star
Trek" starship. The Enterprise flew numerous flight and
landing tests, where it was launched from a Boeing 747 and
glided to a landing at Edwards Air Force Base in California.
Photo courtesy NASA The Enterprise separates from a Boeing 747 to
begin one of its flight and landing tests
Finally, after many years of construction and testing (i.e.
orbiter, main engines, external fuel tank, solid rocket
boosters), the shuttle was ready to fly. Four shuttles were
made (Columbia, Discovery, Atlantis, Challenger). The
first flight was in 1980 with the space shuttle Columbia,
piloted by astronauts John Young and Robert
Crippen. Columbia performed well and several flights of
the other shuttles were made.
In 1986, the shuttle Challenger
was destroyed in flight when a flame from a leaky joint on
one of the solid rocket boosters ignited the fuel in the
external fuel tank. The Challenger exploded and the entire
crew was lost. The shuttle program was suspended for several
years, while the reasons for the disaster were investigated
and corrected. After several years, the space shuttle flew
again and a new shuttle, Endeavour, was built to
replace Challenger in the shuttle fleet. To date, the space
shuttles have flown about one-fourth of their expected
lifetime (each shuttle was designed for 100 missions) and have
undergone many refits and design changes to make them safer
and to carry heavier payloads into orbit.
Now, let's look at the parts of the space shuttle and a
The space shuttle consists of the following major
two solid rocket boosters (SRB) - critical for
external fuel tank (ET) - carries fuel for the
orbiter - carries astronauts and payload
Let's discuss the parts as we look at a mission.
Space shuttle mission profile. Mouse over each
box for a detailed view.
A typical shuttle mission is as follows:
getting into orbit
launch - the shuttle lifts off the launching pad
orbital maneuvering burn
orbit - life in space
A typical shuttle mission
lasts seven to eight days, but can extend to as much as 14
days depending upon the objectives of the mission.
In the next section, let's look at how the shuttle gets
Getting Into Orbit To lift the 4.5 million
pound (2.05 million kg) shuttle from the pad to orbit (115 to
400 miles/185 to 643 km) above the Earth, the shuttle uses the
two solid rocket boosters (SRB)
three main engines of the orbiter
the external fuel tank (ET)
orbital maneuvering system (OMS) on the orbiter
Let's look at these components closely.
Solid Rocket Boosters
height - approximately 150 ft (46 m)
diameter - 12 ft (3.7 m)
empty - 192,000 lb (87,090 kg)
full - 1,300,000 lb (589,670 kg)
thrust - 2.65 million lb (11.7 million N)
The SRBs are solid
rockets that provide most of the main force or thrust (71
percent) needed to lift the space shuttle off the launch pad.
In addition, the SRBs support the entire weight of the space
shuttle orbiter and fuel tank on the launch pad. Each SRB has
the following dimensions, parameters and parts:
solid rocket motor - case, propellant, igniter,
Because the SRBs are solid rocket engines, once they are
ignited, they cannot be shut down. Therefore, they are the
last component to light at launch.
Main Engines The orbiter
has three main engines located in the aft (back)
fuselage (body of the spacecraft). Each engine is 14 feet
(4.3 m) long, 7.5 feet (2. 3 m) in diameter at its widest
point (the nozzle) and weighs about 6,700 lb (3039 kg).
Photo courtesy NASA One of the space shuttle's main
The main engines provide the remainder of the thrust (29
percent) to lift the shuttle off the pad and into orbit.
The engines burn liquid hydrogen and liquid oxygen, which
are stored in the external fuel tank (ET), at a ratio
of 6:1. They draw liquid hydrogen and oxygen from the ET at an
amazing rate equivalent to emptying a family swimming pool
every 10 seconds! The fuel is partially burned in a
pre-chamber to produce high pressure, hot gases that
drive the turbopumps (fuel pumps). The fuel is then fully
burned in the main combustion chamber and the exhaust
gases (water vapor) leave the nozzle at approximately 6,000
mph (10,000 km/h). Each engine can generate between 170,000
and 213,000 lb (748,000 to 937,200 N) of thrust; the rate of
thrust can be controlled from 65 percent to 109 percent
maximum thrust. The engines are mounted on gimbals
(round bearings) that control the direction of the exhaust,
which controls the forward direction of the rocket.
External Fuel Tank As
mentioned above, the fuel for the main engines is stored in
the ET. The ET is 158 ft (48 m) long and has a diameter of
27.6 ft (8.4 m). When empty, the ET weighs 78,100 lb (35, 425
kg). It holds about 1.6 million lb (719,000 kg) of propellant
with a total volume of about 526,000 gallons (2 million
The ET is made of aluminum and aluminum composite
materials. It has two separate tanks inside, the forward
tank for oxygen and the aft tank for hydrogen,
separated by an intertank region. Each tank has baffles to
dampen the motion of fluid inside. Fluid flows from each tank
through a 17 in. (43 cm) diameter feed line out of the ET
through an umbilical line into the shuttle's main engines.
Through these lines, oxygen can flow at a maximum rate of
17,600 gallons/min (66,600 l/min) and hydrogen can flow at a
maximum rate of 47,400 gallons/min (179,000 l/min). During the
first few shuttle missions, the ET was painted white, but this
was stopped to reduce the weight.
System The two orbital maneuvering systems' (OMS)
engines are located in pods on the aft section of the
orbiter, one on either side of the tail. These engines are
used to place the shuttle into final orbit, to change the
shuttle's position from one orbit to another, and to slow the
shuttle down for re-entry.
The OMS engines burn monomethyl hydrazine fuel
(CH3NHNH2) and nitrogen tetroxide oxidizer
(N2O4). Interestingly, when these two
substances come in contact, they ignite and burn automatically
(i.e., no spark required) in the absence of oxygen. The fuel
and oxidizer are kept in separate tanks, each pressurized by
helium. The helium is used to push the fluids through the fuel
lines (i.e., no mechanical pump required). In each fuel line,
there are two spring-loaded solenoid valves that close the
lines. Pressurized nitrogen gas, from a small tank
located near the engine, is used to open the valves and allow
the fuel and oxidizer to flow into the combustion chamber of
the engine. When the engines are shut off, the nitrogen goes
from the valves into the fuel lines momentarily to flush the
lines of any remaining fuel and oxidizer; this purge of the
line prevents any unwanted explosions. During a single flight,
there is enough nitrogen to open the valves and purge the
lines 10 times!
Either one or both of the OMS engines can fire, depending
upon the orbital maneuver. Each OMS engine can produce 6,000
lb (26,400 N) of thrust. The OMS engines together can
accelerate the shuttle by 2 ft/s2 (0.6 m/s2). This acceleration can change the
shuttle's velocity by as much as 1,000 ft/s (305 m/s). To
place into orbit or to de-orbit takes about 100-500 ft/s
(31-153 m/s) change in velocity. Orbital adjustments take
about 2 ft/s (0.61 m/s) change in velocity. The engines can
start and stop 1,000 times and have a total of 15 h burn time.
Now let's put these pieces together to lift off!
Profile of shuttle launch and ascent into
Photo courtesy NASA SRB separation
As the shuttle rests on the pad fully fueled, it weighs
about 4.5 million pounds or 2 million kg. The shuttle rests on
the SRBs as pre-launch and final launch preparations are going
on through T minus 31 seconds:
T minus 31 s - the on-board computers take over
the launch sequence.
T minus 6.6 s - the shuttles main engines are
ignited one at a time (0.12 s apart). The engines build up
to more than 90 percent of their maximum thrust.
T minus 3 s - shuttle main engines are in
T minus 0 s -the SRBs are ignited and the shuttle
lifts off the pad.
T plus 20 s - the shuttle rolls right (180 degree
roll, 78 degree pitch).
T plus 60 s - shuttle engines are at maximum
T plus 2 min - SRBs separate from the orbiter and
fuel tank at an altitude of 28 miles (45 km). Main engines
Parachutes deploy from the SRBs.
SRBs will land in the ocean (about 140 miles (225 km)
off the coast of Florida.
Ships will recover the SRBs and tow them back to Cape
Canaveral for processing and re-use.
T plus 7.7 min - main engines throttled down to
keep acceleration below 3g's so that the shuttle does not
T plus 8.5 min - main engines shut down.
T plus 9 min - ET separates from the orbiter. The
ET will burn up upon re-entry.
T plus 10.5 min - OMS engines fire to place you
in a low orbit.
T plus 45 min - OMS engines fire again to place
you in a higher, circular orbit (about 250 miles/400 km).
You are now in outer space and ready to continue
Now, let's look at where you will be living while you are
Orbiter Once in space, the shuttle orbiter
is your home for seven to 14 days. The orbiter can be oriented
so that the cargo bay doors face toward the Earth or away from
the Earth depending upon the mission objectives; in fact, the
orientation can be changed throughout the mission. One of the
first things that the commander will do is to open the cargo
bay doors to cool the orbiter.
Mouse over the "Menu" options to see
The orbiter consists of the following parts:
crew compartment - where you will live and work
forward fuselage (upper, lower parts) - contains
support equipment (fuel cells, gas tanks) for crew
forward reaction control system (RCS) module -
contains forward rocket jets for turning the orbiter in
movable airlock - used for spacewalks and can be
placed inside the crew compartment or inside the cargo bay
contains essential parts (gas tanks, wiring, etc.) to
connect the crew compartment with the aft engines
forms the floor of the cargo bay
cargo bay doors - roof of the cargo bay and
essential for cooling the orbiter
remote manipulator arm - located in the cargo bay
used to move large pieces of equipment in and out of
the cargo bay
platform for spacewalking astronauts
aft fuselage - contains the main engines
OMS/RCS pods (2) - contain the orbital
maneuvering engines and the aft RCS module; used for turning
the orbiter and changing orbits
airplane parts of the orbiter - used for flying
the shuttle upon landing
You will live in the crew
compartment, which is located in the forward fuselage. The
crew compartment has 2,325 cu.ft of space with the airlock
inside or 2,625 cu.ft with the airlock outside.
Cut-away drawing of the orbiter's crew
The crew compartment has three decks:
flight deck - uppermost deck
forward deck - contains all of the controls and
warning systems for the space shuttle (also known as the
seats - commander, pilot, specialist seats (two)
aft deck - contains controls for orbital operations
maneuvering the orbiter while in orbit (rendezvous,
Let's look at the
orbiter's systems and how it achieves these functions.
Life Support The orbiter must provide you
with an environment similar to Earth. You must have air to
breathe, food to eat, water to drink, and a comfortable
temperature. The orbiter must also take away the wastes that
your body produces (carbon dioxide, urine, feces) and protect
you from fire. Let's look at these various aspects of the
orbiter's life support system.
Atmosphere Control, Supply and
Recycling On board the space shuttle, you need to
have the following:
atmosphere similar to Earth
breathed out carbon dioxide removed
contaminating or trace gases removed
normal humid environment
Our atmosphere is a
mixture of gases (78 percent nitrogen, 21 percent oxygen, 1
percent other gases) at a pressure of 14 lbs/in2 (1 atm) that we breathe in and out. The
space shuttle must provide a similar atmosphere. To do this,
liquid oxygen and liquid nitrogen are carried on
board in two systems of pressurized tanks, which are located
in the mid-fuselage (each system has two tanks for a
total of four tanks). The cabin pressurization system combines
the gases in the correct mixture at normal atmospheric
pressure. While in orbit, only one oxygen system and one
nitrogen system are used to pressurize the orbiter. During
launch and landing, both systems of each gas are used.
The atmosphere is circulated by five loops of fans. The
circulated air picks up carbon dioxide, heat and moisture:
carbon dioxide canisters remove carbon dioxide by
reacting it with lithium hydroxide. These canisters are
located in the lower deck of the crew compartment and
changed every 12 hours.
Filters and charcoal canisters remove trace
odors, dust and volatile chemicals from leaks, spills and
A cabin heat exchanger in the lower deck cools
the air and condenses the moisture, which collects in a
slurper. Water from the slurper is moved with air to
a fan separator, which uses centrifugal force to
separate water from air. The air is recirculated and the
water goes to a wastewater tank.
Water Besides air, water
is the most important quantity aboard the orbiter. Water is
made from liquid oxygen and hydrogen in the space shuttle's fuel
cells. The fuel cells can make 25 lb (11 kg) of water per
hour. The water from the fuel cells passes through a hydrogen
separator to eliminate any trapped hydrogen gas. Excess
hydrogen gas is dumped overboard. The water is then stored in
four water storage tanks located in the lower deck. Each tank
can hold 165 lb (75 kg). The water tanks are pressurized by
nitrogen so that water can flow to the mid-deck for use by the
crew. Drinkable water is then filtered to remove microbes and
can be warmed or chilled through various heat exchangers
depending upon the use (food preparation, consumption,
personal hygiene). Excess water produced by the fuel cells
gets routed to a wastewater tank and subsequently dumped
Temperature Control Outer
space is an extremely cold environment and temperatures will
vary drastically in different parts of the orbiter. You might
think that heating the orbiter would be a problem. However,
the electronic equipment generates more than enough heat for
the ship. The problem is getting rid of the excess heat. So
the temperature control system has to carry out two major
Distribute heat where it is needed on the orbiter
(mid-fuselage and aft sections) so that vital systems do not
freeze in the cold of space.
Get rid of the excess heat.
To do this, the shuttle has two methods to handle
Passive methods - generally simple, handle small
heat loads and require little maintenance.
Insulating materials (blankets), surface coatings,
paints - reduce heat loss through the walls of the
various components just like your home insulation.
Electrical heaters - use electrically-heated
wires like a toaster
to heat various areas.
Active methods - more complex, use fluid to
handle large heat loads, require maintenance.
Cold plates - metal plates that collect heat by
direct contact with equipment or conduction.
Heat exchangers - collect heat from equipment
using fluid. The equipment radiates
heat to a fluid (water, ammonia) which in turn passes heat
on to freon. Both fluids are pumped and recirculated to
Pumps, lines, valves - transport the collected
heat from one area to another.
Radiators - located on the inside surfaces of
the cargo bay doors that radiate the collected heat to
Flash evaporator/ammonia boilers - these
devices are located in the aft fuselage and transfer heat
from Freon coolant loops overboard when cargo bay doors
are closed or when cargo bay radiators are overloaded.
Freon coolant loops wrap around an inner core.
The evaporator sprays water on the heated core.
The water evaporates removing heat.
The water vapor is vented overboard.
Freon coolant loops pass through a tank of
Heat released from the freon causes the ammonia to
Ammonia vapor is dumped overboard.
The cabin heat
exchanger also controls the cabin temperature. It uses
circulated cool water to remove excess heat (cabin air is also
used to cool electronic equipment) and transfers this heat to
a Freon exchanger. The Freon then transfers the heat to other
orbiter systems (e.g., cryogenic gas tanks, hydraulic systems)
and radiates excess heat to outer space.
Light The orbiter has
internal fluorescent floodlights that illuminate the crew
compartment. The orbiter has external floodlights to
illuminate the cargo bay. Finally, the control panels are
lighted internally for easy viewing.
Food Food is stored on
the mid-deck of the crew compartment. Food comes in several
forms (dehydrated, low moisture, heat-stabilized, irradiated,
natural and fresh). The orbiter has a galley-style kitchen
module along the wall next to the entry hatch, which is
equipped with the following:
food storage compartments
a food preparation area with warm and cold water outlets
metal trays so the food packages and utensils do not
Waste Removal Like any
home, the orbiter must be kept clean, especially in space when
floating dirt and debris could present a hazard. Wastes are
made from cleaning, eating, work and personal hygiene. For
general housecleaning, various wipes (wet, dry, fabric,
detergent and disinfectant), detergents, and wet/dry vacuum
cleaners are used to clean surfaces, filters and the
astronauts. Trash is separated into wet trash bags and dry
trash bags, and the wet trash is placed in an evaporator that
will remove the water. All trash bags are stowed in the lower
deck to be returned to Earth for disposal. Solid waste from
the toilet is compacted, dried and stored in bags where it is
returned to Earth for disposal (burning). Liquid waste from
the toilet goes
to the wastewater tank where it is dumped overboard.
Fire Protection Fire is
one of the most dangerous hazards in space. The orbiter has a
Fire Detection and Suppression Subsystem that consists
of the following:
area smoke detectors on each deck
smoke detectors in each rack of electrical equipment
alarms and warning lights in each module
non-toxic portable fire extinguishers (carbon
personal breathing apparatus - mask and oxygen bottle
for each crew member
After a fire is extinguished,
the atmosphere control system will filter the air to remove
particulates and toxic substances.
Position and Orbit To change the direction
that the orbiter is pointed (attitude), you must use
the reaction control system (RCS) located on the nose
and OMS pods of the aft fuselage.
View of the front of the orbiter
Photo courtesy NASA OMS firing
The RCS has 14 jets that
can move the orbiter along each axis of rotation (pitch, roll,
yaw). The RCS thrusters burn monomethyl hydrazine fuel and
nitrogen tetroxide oxidizer just like the OMS engines
described previously. Attitude changes are required for
deploying satellites or for pointing (mapping instruments,
telescopes) at the Earth or stars.
To change orbits (e.g., rendezvous, docking maneuvers), you
must fire the OMS engines. As described above, these engines
change the velocity of the orbiter to place it in a higher or
lower orbit (see How
Satellites Work for details on orbits).
Communications and Tracking You must be able
to talk with flight controllers on the ground daily for the
routine operation of the mission. In addition, you must be
able to communicate with each other inside the orbiter or its
payload modules and when conducting spacewalks outside.
Talking with the
Ground NASA's Mission Control in Houston will send
signals to a 60 ft radio antenna at White Sands Test Facility
in New Mexico. White Sands will relay the signals to a pair of
Tracking and Data Relay satellites
in orbit 22,300 miles above the Earth. The satellites will
relay the signals to the the space shuttle. The system works
in reverse as well.
The orbiter has two systems for communicating with the
S-band - voice, commands, telemetry and data files
Ku-band (high bandwidth) - video and transferring
two-way data files
to Each Other The orbiter has several intercom
plug-in audio terminal units located throughout the crew
compartment. You will wear a personal communications control
with a headset. The communications control is battery-powered
and can be switched from intercom to transmit functions. You
can either push to talk and release to listen or have a
continuously open communication line. To talk with
spacewalkers, the system uses a UHF frequency, which is picked
up in the astronaut's spacesuit.
The orbiter also has a series of internal and external video
cameras to see inside and outside.
Navigation The orbiter must be able to know
precisely where it is in space, where other objects are and
how to change orbit. To know where it is and how fast it is
moving, the orbiter uses global positioning
systems (GPS). To know which way it is pointing
(attitude), the orbiter has several gyroscopes.
All of this information is fed into the flight computers for
rendezvous and docking maneuvers, which are controlled in the
aft station of the flight deck.
Power All of the on-board systems of the
orbiter require electrical power. Electricity is made from
cells, which are located in the mid fuselage under the
payload bay. These fuel cells combine oxygen and hydrogen from
pressurized tanks in the mid fuselage to make electricity and
water (see How Fuel
Cells Work for details). Like a power grid
on Earth, the orbiter has a distribution system to supply
electrical power to various instrument bays and areas of the
ship. The water is used by the crew and for cooling.
Computers The orbiter has five on-board
computers that handle data processing and control critical
flight systems. The computers monitor equipment and talk to
each other and vote to settle arguments. Computers control
critical adjustments especially during launch and landing:
operations of the orbiter (housekeeping functions,
payload operations, rendezvous/docking)
Pilots essentially fly the
computers, which fly the shuttle.
Doing Useful Work The Shuttle was designed
to deploy and retrieve satellites as well as deliver payloads
to Earth orbit. To do this, the shuttle uses the Remote
Manipulator System (RMS). The RMS was built by Canada and
is a long arm with an elbow and wrist joint. You can control
the RMS from the aft flight deck. The RMS can grab
payloads (satellites) from the cargo bay and deploy
them, or grab on to payloads and place them into the bay. With
the RMS, the shuttle plays a major role in building the International
Space Station by delivering components built on Earth and
attaching them to existing modules in space.
Photo courtesy NASA Spacelab module in the orbiter's cargo bay
provides additional lab space
Within the mid-deck, there are are racks of experiments to
be conducted during each mission. When more space is needed
for experiments, the mission may call for the Spacelab module.
The Spacelab module was built by the European Space agency. It
fits into the cargo bay and can be accessed by a tunnel from
the mid-deck of the crew compartment. It provides a
"shirt-sleeve" environment in which you can work. The
experiments will be in the areas of microgravity science, life
science, space science, Earth science, engineering research
and development, and commercial product development.
Photo courtesy NASA Astronauts working in the Spacelab
You will spend most of your time on the shuttle doing work
to accomplish the mission objectives. Besides work, you will
have to exercise frequently on the treadmill to counteract the
loss of bone and muscle mass associated with weightlessness.
You will also eat at the galley and sleep in your bunk-style
sleeping quarters. You will have a toilet and personal hygiene
facilities for use. You may have to perform spacewalks to
accomplish the mission objectives. This will involve getting
into a space suit and going through depressurization
procedures in the airlock (see How
Spacesuits Work for details).
When your mission objectives have been accomplished, it
will be time to return to Earth. Let's look at this process in
the next section.
Return to Earth: Re-entry and Landing In
order to return to Earth, the orbiter must be maneuvered into
Maneuvering of the orbiter for
When a mission is finished and the shuttle is halfway
around the world from the landing site (Kennedy Space Center,
Edwards Air Force Base), mission control gives the command to
come home, which prompts the crew to:
Close the cargo bay doors. Most likely, you have been
flying nose-first and upside down, so you then fire the
RCS thrusters to turn the orbiter tail first.
Once you are tail first, you fire the OMS engines
to slow the orbiter down and fall back to Earth; it will
take about 25 minutes before you reach the upper atmosphere.
During that time, you fire the RCS thrusters to
pitch the orbiter over so that the bottom of the orbiter
faces the atmosphere (about 40 degrees) and you are moving
nose first again.
Finally, you burn leftover fuel from the forward
RCS as a safety precaution because this area encounters
the highest heat of re-entry.
Photo courtesy NASA Artist's concept of a shuttle
Because you are moving at about 17,000 mph (28,000 km/h),
the orbiter will hit air molecules and build up heat from friction
(approximately 3000 degrees F, or 1650 degrees C). To protect
you from this heat, the orbiter is covered with ceramic
Reinforced carbon-carbon on the wing surfaces and
High-temperature black surface insulation tiles on the
upper forward fuselage and around the windows
White Nomex blankets on the upper payload bay doors,
portions of the upper wing and mid/aft fuselage
Low-temperature white surface tiles on the remaining
These materials were designed to absorb large
quantities of heat without increasing their temperature very
much (i.e., high heat capacity). During re-entry, the aft
steering jets help to keep the orbiter at its 40 degree
attitude. The hot ionized gases of the atmosphere that
surround you will prevent radio communication with the ground
for about 12 minutes (i.e., ionization blackout).
Shuttle flight path for
Soon, the orbiter will encounter the main air of the
atmosphere and it will be able to fly like an airplane.
The orbiter was designed from a lifting body design with swept
back "delta" wings. With this design, the orbiter can generate
with a small wing area. The orbiter is being flown by the
flight computers at this point. The orbiter will make a series
of S-shaped, banking turns to slow its descent speed as you
begin your final approach to the runway. The commander picks
up a radio beacon from the runway (Tactical Air Navigation
System) when the orbiter is about 140 miles (225 km) away
from the landing site and 150,000 feet (45,700 m) high. At 25
miles (40 km) out, the shuttle's landing computers give up
control to the commander. The commander flies the shuttle
around an imaginary cylinder (18,000 feet or 5,500 m in
diameter) to line the orbiter up with the runway and drop the
altitude. During the final approach, the commander steepens
the angle of descent to minus 20 degrees (almost seven times
steeper than the descent of a commercial airliner).
Photo courtesy NASA Space shuttle orbiter touching
When the orbiter is 2,000 ft (610 m) above the ground, the
commander pulls up the nose to slow the rate of descent. The
pilot deploys the landing gear and the orbiter touches down.
The commander brakes the orbiter and the speed brake on the
vertical tail opens up. A parachute is deployed from the back
to help stop the orbiter. The parachute and the speed brake on
the tail increase the drag on
the orbiter. The orbiter stops about midway to three-quarters
of the way down the runway.
Photo courtesy NASA Parachute deployed to help stop the orbiter
Photo courtesy NASA Orbiter being serviced just after
After landing, you go through the shutdown procedures to
power down the spacecraft. This process takes about 20
minutes. During this time, the orbiter is cooling and noxious
gases, which were made during the heat of re-entry, blow away.
Once the orbiter is powered down, you exit the vehicle. Crews
are on-hand to begin servicing the orbiter. You have had a
Future Space Shuttles The current shuttle
fleet has been through about a quarter of its expected
lifetime. These shuttles have undergone and will have many
improvements to make them lighter, safer and more efficient.
Some of the improvements include:
ET - redesigned to reduce the weight by 7,500 lb
(3400 kg); This improvement allows the shuttle to carry that
much more weight in payload.
Main engines - pumps, combustion chambers and
nozzles have been redesigned for safety.
SRB - improve the valves, seals, filters and
propellant for safety.
Hydraulic systems - change from rocket
fuel-powered electric generators to safer, lighter,
Glass cockpit - lightweight LCD displays
replaced cumbersome mechanical displays and redesigned for
more efficient use.
Photo courtesy NASA Shuttle Atlantis's new glass
Undoubtedly, the space shuttle computers will be overhauled
as computer technology improves. Space shuttles may also have
touchscreen controls in the future.
Photo courtesy NASA Future space shuttle concepts from left to
right: X-33, VentureStar, current space shuttle
The current space shuttle has four components, three of
which are recovered after each flight. The ET is discarded
after each use. But what if you could have a shuttle that was
all one piece and 100 percent recoverable? NASA is currently
exploring this idea with the X-33 and VentureStar designs (see
Space Planes Will Work for details).
Photo provided courtesy of the X Prize
Foundation Artwork: Martin Demonte Flightpath of X Prize concept: Pablo De
Finally, private entrepreneurs are also developing reusable
space vehicles in competition for the X Prize. The X Prize is
a $10 million prize competition for the first team to build
and launch a fully reusable rocket that can boost three humans
into a sub-orbital flight (60 miles or 100 km high) on two
consecutive flights within two weeks. The technologies
developed in the X Prize competition may lead to the
development of future, commercial, reusable spacecraft.