Physical Science Essay

flight of the orbiter. Finally, there were five autonomous flights where astronauts piloted the orbiter separately from the 747 shuttle carrier and successfully landed at Edwards Air Force Base.

The orbiter used a tail cone to reduce drag and turbulence during the test flights, including the initial three free flights and captive flights. However, the last two free flights did not have this tail cone, exposing the three simulated space shuttle main engines and two orbital maneuvering system engines to aerodynamic forces. After extensive testing in the United States, the Enterprise was transported to Europe for air shows after crossing the Atlantic Ocean. On November 18, 1985, it was relocated from Kennedy Space Center to Washington, D.C.

The first orbiter, Enterprise, was originally built for NASA as part of the Space Shuttle Program and later came under ownership of the Smithsonian Institution. The following orbiter, Columbia, became the first to go into space. Columbia arrived at Kennedy Space Center from Dryden Flight Research Facility on March 25, 1979, atop the 747 shuttle carrier. Then it was prepared for its inaugural flight on April 12, 1981.

The space shuttle launches vertically using two solid rocket boosters called the first stage and three main engines known as the second stage. Both boosters and main engines remain active during liftoff. To achieve orbit, the shuttle must accelerate from zero to a speed of approximately 28,968 kilometers per hour (18,000 miles per hour), about nine times faster than a typical rifle bullet.

The spacecraft needs to leave Earth's atmosphere in order to avoid air resistance and overheating, allowing it to achieve high speeds. The journey begins with a gradual acceleration, taking eight seconds

for the engines and boosters to reach a speed of 161 kilometers per hour (100 mph) due to the ship's initial weight of over 2.04 million kilograms (4.5 million pounds). However, within one minute, the shuttle surpasses 1,609 kilometers per hour (1,000 mph) and has already consumed more than one and a half million pounds of fuel.

According to Rutondo (1994), having sufficient thrust is essential for a craft to exceed the speed of sound quickly. The ascent phase demonstrates that after approximately two minutes, when the shuttle reaches an altitude of about 45 kilometers (28 miles) and a velocity surpassing 4,828 kilometers per hour (3,000 mph), the boosters' propellant is depleted and they are discarded. These booster casings descend into the Atlantic Ocean via parachute, landing around 225 kilometers (140 miles) off Florida's coast. Dedicated NASA vessels recover these empty boosters - which are the largest solid rockets ever built - with the intention of refilling them with fuel for future launches. The solid fuel utilized in these boosters consists of powdered aluminum, similar to kitchen foil, combined with oxygen provided by ammonium perchlorate. Once the main engines cease functioning, the shuttle enters an elliptical orbit that would result in re-entry into Earth's atmosphere above the Pacific Ocean without any alterations. However, approximately 35 minutes after engine shutdown - typically when reaching its highest point in this elliptical orbit - ignition occurs for roughly three minutes on each side of the shuttle's tail using two orbital maneuvering system engines.

The shuttle's orbital maneuvering system engines utilize two propellants that automatically ignite upon contact, enabling a three-minute firing to circularize the shuttle's orbit at a safe altitude

above the atmosphere. Moreover, the shuttle possesses a unique capability of retrieving and returning large satellites from orbit. Assisting in manipulating sizable objects within the payload bay is the Canadian-built robotic arm called the Remote Manipulator System, situated on the left-hand edge of the cargo bay. This arm also aids in positioning spacewalking astronauts for various tasks such as satellite repairs, maintenance activities (including those conducted on the Hubble Space Telescope), or construction efforts for the International Space Station.

A typical shuttle crew consists of five to seven individuals; however, it can accommodate up to eight people. The crew composition includes pilot astronauts responsible for flying the shuttle (referred to as commander and pilot) and mission specialist astronauts who are trained scientists and engineers assigned with conducting experiments or performing specific tasks while in orbit. On occasion, payload specialist astronauts may join the crew to oversee specific cargo operations.

Additionally, among its capabilities, the shuttle can launch up to 28,803 kilograms (63,500 pounds) of cargo into orbit and remain in orbit for a maximum duration of 17 days before commencing its return journey back to Earth.

The shuttle's middeck is equipped with amenities for dining, resting, and maintaining personal hygiene. The upper deck, known as the flight deck or cockpit, contains flight controls on both its front and back walls. To reach the equipment bay, located on a smaller lower deck, one must lift up the floor panels on the middeck. This area beneath the floor holds avionics equipment, electronics equipment, and a trash compartment.

The crew cabin of the spaceship is pressurized and has a volume of about 74.3 cubic meters (2,625 cubic feet). It includes a circular

side hatch that measures approximately one meter (3 feet) in diameter. This hatch serves as both an entry and exit point for astronauts before launch and after landing. Additionally, there is an airlock located in the shuttle's payload bay that separates spacewalkers from the rest of the cabin. Before beginning extravehicular activities, the airlock is depressurized. A short tunnel connects the airlock to the middeck, and it can be isolated from the rest of the cabin by closing an inner hatch.

The airlock has a volume of about 4.24 cubic meters (150 cubic feet) and includes an outer hatch for space exit as well as a docking mechanism specifically designed for attachment to the International Space Station. During the initial ascent, the orbiter is lifted by the space shuttle's three main engines and solid rocket boosters, generating sufficient thrust. These main engines continue to operate for approximately 8.5 minutes after launch, matching the duration of the shuttle's powered flight. Once the solid rockets are discarded, the main engines then accelerate the shuttle from a speed of 4,828 kilometers per hour (3,000 mph) to over 27,358 kilometers per hour (17,000 mph) in just six minutes to achieve orbit. These engines combined produce a maximum thrust exceeding 1 unit.

The shuttle consumes 2 million foot-pounds of energy. As it accelerates, it becomes the largest gas guzzler in the world. The main engines burn a half-million gallons of liquid propellant from the orange external fuel tank. The propellant consists of liquid hydrogen and liquid oxygen, with the hydrogen being the second coldest liquid on Earth at -423 degrees Fahrenheit (-252.8 degrees Celsius). The engines primarily emit water vapor as the

hydrogen and oxygen combine. The engines consume fuel at a rate that could empty an average family swimming pool in under 25 seconds, while generating over 37 million horsepower to propel the Shuttle into orbit.

The main engines of the space shuttle are nearly 13 times faster than a car engine on the highway. These engines use high-energy propellants in a staged combustion cycle to produce thrust. The propellants undergo partial combustion in dual preburners, creating hot gas at high pressure for the turbo pumps. Inside the main engine's combustion chamber, temperatures can reach up to 3,000 degrees Fahrenheit (1,315.6 degrees Celsius). Each main engine operates with a liquid oxygen to liquid hydrogen mixture ratio of 6 to 1, resulting in a sea level thrust of 179,097 kilograms (375,000 pounds) and a vacuum thrust of 213,188 kilograms (470,000 pounds).

The engines can be throttled from 65 percent to 109 percent thrust, allowing for high thrust during liftoff and the initial ascent but reducing thrust to limit acceleration to 3 g's during the final ascent phase. Gimbaled engines provide pitch, yaw, and roll control during ascent. For the first two minutes of flight, solid rocket boosters (SRB) operate alongside the main engines to provide additional thrust for escaping Earth's gravitational pull. At approximately 45 km altitude (24 nautical miles), the boosters separate from the orbiter/external tank, descend with parachutes, and land in the Atlantic Ocean. Ships recover and refurbish the boosters for reuse on land.

The boosters provide guidance during the initial ascent and have a thrust of 5,300,000 lb. Besides the solid rocket motor, the booster contains different subsystems including structural, thrust vector control, separation, recovery, electrical

and instrumentation systems. The solid rocket motor is the largest ever developed for space travel and the first to be used on a crewed vehicle. It consists of a segmented motor case, solid propellants, an ignition system, a movable nozzle, and necessary instrumentation and integration hardware.

Each solid rocket motor contains over 450,000 kg (1,000,000 lb) of propellant. The propellant is created through an intricate mixing and casting procedure at a facility in Utah. This process takes place in three separate mixer buildings where 600 gallon bowls are used for the mixing. Once mixed, the propellant is carefully transported to designated casting buildings where it is poured into casting segments.

The cured propellant has the appearance and texture of a hard rubber typewriter eraser. It is made up of a synthetic rubber formed by combining a polymer and its curing agent. The flexibility of the propellant is determined by the proportion of binder to curing agent, as well as the solid ingredients which include oxidizer and aluminum. The solid fuel consists of powdered aluminum, similar to the foil wraps found in kitchens, mixed with oxygen from ammonium perchlorate. The external tank (ET) serves as the orbiter's "gas tank" and holds the propellants that power the space shuttle main engines.

The tank is an essential component in the shuttle's launch as it provides structural support for attaching the solid rocket boosters and orbiter. Unlike other components, the tank is not reused and is discarded after approximately 8.5 minutes into the flight when its propellant has been used up. Throughout liftoff, the external tank bears the combined thrust loads of 7.8 million pounds generated by the three main engines and

two solid rocket motors.

The orbiter detaches from the solid rocket boosters at around 45 kilometers (28 miles) above Earth while the main engines continue to burn. Carrying the still attached external tank, the orbiter reaches a height of approximately 113 kilometers (70 miles) at near orbital velocity. Afterward, the empty tank separates and mostly disintegrates in the atmosphere before falling into the ocean.

The external tank is composed of three main parts: an oxygen tank positioned forward, a hydrogen tank positioned aft, and an intertank that connects these two propellant tanks. The intertank has multiple functions including housing instrumentation and processing equipment, as well as serving as an attachment structure for the forward end of the solid rocket boosters.

When completely filled, even though it weighs only one-third of the oxygen tank's weight, the hydrogen tank is twice its size.

Liquid oxygen and liquid hydrogen have a weight difference due to liquid oxygen being 16 times heavier. The spacecraft's external tank is coated with a 2.5-centimeter (1-inch) thick spray-on polyisocyanurate foam, which serves as a thermal protection system. This foam helps maintain the desired temperature of propellants, protects the tank from aerodynamic heat, and reduces ice formation. Additionally, the external tank includes various systems such as a propellant feed system, pressurization and vent system, environmental conditioning system, and electrical system. These systems are responsible for controlling propellant flow, regulating tank pressure, temperature, and atmosphere, providing power and instrumentation signals,and offering lightning protection.

To deliver propellants to the orbiter engines,a connection with a diameter of 43 centimeters (17 inches) is used.This connection branches inside the orbiter to supply each main engine.The forward fuselage of the orbiter houses the cockpit,living quarters,and

experiment operator's station while payloads are carried in the mid-fuselage payload bay.In addition,the aft fuselage contains the orbiter's main engines and maneuvering thrusters.

The cockpit, living quarters, and experiment operator's station are situated in the front fuselage. This section contains the pressurized crew module and supports the nose section, nose gear, nose gear wheel well, and doors. The crew station module, measuring 65 cubic meters (2,325 cubic feet), is located in the forward part of the orbiter. It consists of three sections: the flight deck, the middeck/equipment bay, and an airlock. In the payload bay beyond the crew module's aft bulkhead, a docking module and transfer tunnel with an adapter can be added for crew and equipment transfer during docking, Space lab activities, and extravehicular operations.

The crew module consists of a two-level design. It features a forward flight deck where the commander's seat is located on the left side and the pilot's seat on the right side. This configuration allows for piloting from either seat and facilitates emergency returns by a single individual. Both seats are equipped with manual flight controls, such as rotation and translation hand controllers, rudder pedals, and speed-brake controllers. In total, the flight deck can accommodate four occupants. The on-orbit displays and controls are positioned at the rear of the flight deck and crew compartment.

The displays and controls on the left are for operating the orbiter, while those on the right are for operating and handling the payloads. According to The Encyclopedia Americana International Edition, Vol 25, (1998), there are over 2,020 separate displays and controls on the flight deck. The shuttle's crew uses five independent computers to monitor and

control the various systems of the shuttle. The skilled operation of the crew is required during every moment of the shuttle's flight, especially during changes or maneuvers, in coordination with computerized controls. The upper flight deck of the crew module has six pressure windshields, two overhead windows, and two rear-viewing payload bay windows. Another window is located in the crew entrance/exit hatch in the midsection of the crew module. The middeck of the crew module has provisions and stowage facilities for four crew sleep stations.

The middeck of the spacecraft provides stowage for various items, such as lithium hydroxide canisters and other gear, waste management system, personal hygiene station, and work/dining table. It is designed to accommodate a maximum crew size of seven. If needed, the middeck can be reconfigured by replacing the modular stowage and sleeping provisions with three rescue seats. This allows for a rescue flight crew of three and a maximum rescued crew of seven. The airlock, which grants access for spacewalks (extravehicular activity or EVA), can be positioned in different locations: inside the orbiter crew module in the middeck area on the aft bulkhead, mounted outside the cabin on the bulkhead, or on top of a tunnel adapter that connects the pressurized Spacehab module with the orbiter cabin. Additionally, an EVA airlock can be provided by a docking module. The airlock has two spacesuits, expendables for two six-hour payload EVAs, one contingency or emergency EVA, and mobility aids including handrails to assist the crew during various tasks.

The airlock provides space for two crew members to change into spacesuits. I have discovered that the midfuselage not only forms the payload bay of the

orbiter, but also supports various components such as the payload bay doors, hinges, tiedown fittings, forward wing glove, and orbiter system components. Additionally, each payload bay door has four radiator panels, which can be unlatched and moved to the correct position when the doors are opened.

The panels on the orbiter allow heat radiation from both sides, including the four aft radiator panels which radiate from the upper side only. Payloads can be attached directly to the orbiter or to payload carriers. Typical carriers include the inertial upper stage, pressurized modules, or specialized cradles for holding payloads. The Remote Manipulator System, known as RMS, is a 15.2-meter (50-foot) long articulating arm that can be controlled remotely from the orbiter's flight deck.

The elbow and wrist movements allow for the grappling of payloads in order to deploy them from the payload bay or retrieve and secure them for the return to Earth. The presence of a television camera and lights at the outer end of the arm allows the operator to view their hand movements on television monitors. Moreover, there are three floodlights positioned on each side of the payload bay. As for the aft fuselage, it comprises the left and right orbital maneuvering systems, space shuttle main engines, body flap, vertical tail, and orbiter/external tank rear attachments.

The forward bulkhead separates the rear section of the fuselage from the front section. The upper part of the bulkhead is connected to the vertical tail. The internal thrust structure provides support for the three main engines of the space shuttle, as well as the low-pressure turbopumps and propellant lines. I have learned that the US Space Shuttle program is a

significant milestone in the construction and operation of a space station, as well as the development of a "space plane" system. This system allows for the launching and landing of a vehicle into space, with the added benefit of being reusable, minimizing g-force and prioritizing safety and reliability.

Works Cited: Donald Cox (1962). The Space Race.

The book, "Into The Unknown," was published by Chilton Company Publishers in Philadelphia and New York, by Louis Rotundo in 1994. It was published by the Smithsonian Institution Press in Washington and London. Another publication mentioned is the Encyclopedia Americana International Edition, Volume 25, published in 1998 by Grolier Incorporated in Connecticut.