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Space Exploration


Space Exploration


Table of contents


Introduction

The stars have always fascinated us. This fascination was probably born when the first human directed his eyes into the nightly sky. Of course, these ancient peoples had no idea of the nature of the stars, so they made up fantastic myths about the stars. They believed to see constellations in the stars, and even found rules how one could predict the future by looking at them. For thousands of years these believes have hardly changed. Finally, at the dawn of the modern age, thinkers, such as Copernicus and Kepler, were able to reveal more secrets about the star, but still no sane being thought that it would be possible to travel to the stars or at least to the Moon. The first time that such a thought was discussed when Jules Verne wrote his visionary book "From the Earth to the Moon."




It was not before the end of World War II, however, when people became serious about traveling to the Moon. It was the time of the Cold War and both superpowers were struggling to prove that they possessed superior technology. At first the Soviet Union seemed to be ahead but the United States were far from admitting defeat in the space race.

In the following I want to give you a more detailed picture about mankind's way into space. Since it was difficult to access Russian sources I had to focus on the American efforts.


1. The Sputnik Shock

In both Russia and the United States the space race was a military project in the beginning. In the Soviet union it was headed by Sergei Pavlovich Korolev. In the 30s he led an amateur rocketry organization. In the 40s and early 50s he was forced to work in Stalin's labor camps.

After Stalin's death he was allowed to focus on his rocket project again. On May 20, 1954, his design bureau got an order from the government to develop the first Russian intercontinental ballistic missile (ICBM). Some plans already existed for the so-called R-7. It was supposed to be an offensive weapon against the United States that could be launched from Russian territory. Six days later he handed over a paper that was written by his friend M. Tikhonravov. It was titled "Report on an Artificial Satellite of the Earth". It stated that the R-7 missile could be used to launch satellites into space. Yet, the R-7 remained a military project. The military officials intended it to be a weapon and were reluctant to admit missile launches with it.

About a year afterwards the first Soviet Organization devoted to space flight was born. In August 1955 Korolev presented a new paper to a Soviet governmental commission. The R-7 should be used to lift a 1500kg object into space. Based on the report he received permission to use the rocket as a satellite launcher. Many Soviet military leaders were against the project because they feared that it might interfere with the ballistic missile development. Korolev was able to convince the Soviet leader Khrushchev of the contrary. The program could finally be started.

In the first days the program was processing slowly. It was formally approved on January 30, 1966, months after the plans were turned in. Subcontractors were not making required deliveries. Worst of all the R-7 did not have enough thrust to lift the heavy satellite. Its weight had to be reduced form 1500kg to 100kg.

The program was nearing completion in August 1957 when the first Russian ICBM, the R-7 was successfully tested. The rocket was now being modified for the world's first satellite launch. It had two stages and a length of 29 meters. On October 4, 1957 the rocket was ready for launch. Six minutes after lift-off Sputnik was released. Sputnik was designed to determine the density of Earth's upper atmosphere. However, it only transmitted signals for a short time. A month later, a second Sputnik was launched. It brought the first living being into space, the dog Laika. For about a week medical data was collected. Afterwards the dog had to be put to sleep since a safe reentry was not possible at that time. The last Sputnik that was shot into space was the one that was intended to go up first. It was launched on May 15, 1958. For two years it performed experiments on the Earth's magnetic field and ionosphere.

The launch of Sputnik was a shock to the western world since there were no previous announcements. The Russians seemed to be ahead of the Russians. In order to close this gap the National Aeronautics and Space Organization (NASA) was created on October 1, 1958.


2. The Mercury Project

2.1. What was Mercury about?

Project Mercury was launched one year after Sputnik was shot into space on October 7, 1958 as NASA's first project. It had three prime objectives.

to send manned spacecraft into orbit (circle Earth)

to find out weather humans can work properly in space, and

to recover both man and spacecraft safely.

The Mercury engineers were true pioneers. Nothing that they were doing has ever been done before. The engineers had to build a space capsule that protects humans in space from the vacuum, the freezing cold temperatures, the radiation of space that has just been discovered, and the astronauts had to survive the heat of the reentry into the atmosphere during which the spacecraft would be flying very fast.

The engineers found that the ideal shape for the spacecraft was bullet-like. They put strong heat shields on the front side so that the astronaut could survive the reentry. The Mercury capsules were driven into space by to different propulsion systems. At first the astronauts were boosted into space by Redstone Rockets which were only good for sub-orbital flights. Later the more powerful Atlas-D rockets were used. The Atlas-D was a modified ballistic missile. Its skin was extra thin to safe weight, so that it had to be pressurized from within.

Compared with today's standards the Mercury capsules were very small. They had about 12,000m3 of Volume which is just the right size for one person to squeeze in. The internal controls were powered with batteries. Inside there were 120 controls, and 90 switches and levers. Despite that great number of instruments Mercury was only able change its orientation in space.


2.2. Mission History

Out of a group of 110 military pilots, seven were chosen to become America's first Astronauts, the Mercury Seven. They all gave their spacecraft a name which ended with a 7 to emphasize the teamwork among them. Before they could go on their mission tests on animals, and even a breathing robot were conducted.

On May 5, 1961, a Redstone, that was given the name Freedom 7, was ready to take off. It took Allan B. Shepard Jr. on a 15 minute space ride that was watched by 45 million Americans on TV. He had the experience of weightlessness for five minutes while he was traveling in a height of 187km.

Nine months later it was John H. Glenn's turn to make the first trip with an Atlas-D, which he had named Friendship 7. Glenn remained in the orbit for almost five hours, circling Earth three times. After experiencing a sunrise and a sunset in space he returned safely to Earth as a national hero. The primary objective of the "Mercury Project" was thus fulfilled.

Other Mercury missions followed, most noticeably Faith 7 the last one which started in May 1963. It was supposed to be an endurance test. L. Gordon Cooper spent 34 hours in space and rounded Earth 22 times. On board he slept, and made some great pictures of the Earth. He was also the first person to launch a satellite in space.


2.3. The Importance of Mercury

The Mercury Project answered many of the basic questions about space flight. It has proven that is possible to build rockets that are strong enough to launch humans into space, and that they could survive there. The engineers gained much experience and learned about the difficulties of preparing a rocket. It also showed that a global communications network was necessary to make the missions more secure.



The program was so successful that the last scheduled mission could be canceled. President Kennedy announced in 1961 that the United States would reach the Moon before the end of the decade. By 1963 most of the Mercury engineers had already been working on NASA's other projects: Gemini and Apollo.


3. "Twins" in space: Gemini

3.1. Just another step on the way to the Moon?

After the success of Mercury the Gemini Program was showing the Gemini Program was introduced to the public on January 3, 1962. At this time Apollo had already been called into life. To the public it was not as interesting as Mercury or Apollo since it was not real pioneering anymore. It was a mere preparation for the Apollo program. The Gemini Program had three main objectives.

The first was to accomplish space fights of two weeks in duration. The lunar missions would later take the same time. So NASA had to demonstrate the man and machine could work in space for so long.

The second goal was to dock with orbiting vehicles and to maneuver the docked combination using the propulsion system. Later these techniques would be used when the lunar lander separates from the command module in the lunar orbit.

The third was to perfect the methods of reentry into the atmosphere and land on a pre-selected point on Earth. The goal of making a landlanding was canceled in 1964, however.

The Gemini capsule was an improvement of Mercury. That's why it was originally called "Mercury Mark II". It had to be maneuvered by two pilots. The module had twice the weight of the Mercury capsules, but size of the cabin was increased by only 50 per cent. As a result the Gemini capsules appeared to be more cramped. In case of emergency the pilots could leave the capsule with an escape rocket instead of ejection seats. The batteries that provided Mercury with electrical power were replaced with fuel cells.

The capsule sat on a Titan 2 launch vehicle. The docking maneuvers were practiced with unmanned Agena upper stages that were always started shortly before the Titan 2 rockets. In order to fly the complicated docking maneuvers the maneuvering capabilities of Mercury have been improved a lot. Gemini was able to fly forward, backward, and sideways on its way around Earth. It was even possible to change orbits. These maneuvers required great precision, so besides the two astronauts the first board computers were required to make complex calculations.

The constructors of Gemini had to avoid long delays between the flights. Many parts of the spaceship were reusable. Thus the coast of the project have also been lowered. In only 20 months ten Gemini missions were launched. As there was little time between the flights space flight became routine. The ground operations became smoother and the risk for the astronauts decreased after every mission.


3.2. Important Missions


The first manned Gemini mission (Gemini 3) took off on March 23, 1965. It was a successful test of the design and lasted just four hours. The first full-time Gemini mission was launched on June 3, 1965, and returned safely four days later. Its highlight was the first space-walk ever. James McDivitt left the capsule for 22 minutes tied to a tether.

The goal of a two week space flight was accomplished by Gemini VII from December 4-18, 1965. The mission solved many problems of long-duration space flight. It included studies of nutrition in space and proved that even longer trips to space do not pose a threat to the astronaut's health. The Gemini VII pilots also managed to rendezvous with an Agena for the first time.

The most exciting Gemini mission was undoubtedly Gemini VIII that took off on March 16, 1966. Its objective was to achieve the first docking maneuver ever. The pilot Neil Armstrong approached the Agena carefully and managed to dock. The successful action was almost followed by a catastrophe. While docked to the Agena the Gemini capsule began rolling over. A thruster was stuck and could not be deactivated. The crew undocked immediately and the capsule began rotating even faster, at the rate of one revolution per second. In order to stop the motion the astronauts had to use their reentry thrusters. They used up much of their fuel so that an emergency landing had to be made as soon as possible. 10 hours after launch Gemini VIII was already back on Earth.

The last Gemini mission was launched on November 11, 1966. By then all the goals of the Gemini project had been accomplished. Space-walks and complicated maneuvers such as rendezvous and docking procedures had become routine. Fears about the risks to health had been eliminated. The final objective of Gemini (smoothing the reentry) has been completed when the board computer controlled the reentry. Now it was time to tackle the next mission: the flight to the Moon.


4. From the Earth to the Moon

4.1. The technical aspects of Apollo

The Apollo Program was initiated in July 1960, a year earlier than Gemini. At first its prime objective was to fly astronauts around the Moon. Another program including a lunar landing was planned to follow. When President John F. Kennedy declared that an American astronaut would be landing on the surface of the Moon before the end of the decade Apollo shifted its focus. Besides taking men to the Moon the program had two other objectives. The first was to establish the technology to meet other national interests. The second one was to achieve preeminence for the United States in space. Apollo was not just pioneering like Mercury. The constructors also wanted to discover new technologies that could be used for later missions such as skylab.

The Apollo spacecraft consisted of three modules. The command module, the service module and the lunar module. The command module functioned as living quarters for the three-man crew. The cylindrical-shaped service module contained the supplies for the astronauts and the Service Propulsion System engine which was used to maneuver in the lunar orbit.

The lunar module was the first true spacecraft. It was designed for space flights only. Thus, it did not have any aerodynamic qualities. It could separate from the command/service module in the moon orbit taking two astronauts down to the surface.

In order to boost the Apollo vehicles the strongest rockets in history were built. The Saturn V was 110 meters high and fueled it had a total weight of 2.7 million kilograms (!). It was parted in three stages. Each stage was to be disjoined from the rocket after it burnt out. Then the next one would start burning to take the space ship closer to the Moon.

The lunar missions were highly complex and required faster ground operations than Mercury and Gemini since there were now two objects to track in space. The astronauts had to practice hard for their mission. Altogether they spent 84.000 hours, this are nearly 10 man years, on geology field trips, simulations of lunar gravity, and, of course, flying the lunar vehicle.




4.2. The Missions that Made History

The United States lost some of its astronauts for the first time as Apollo was nearing completion. It happened on January 27, 1967, when a test for the first manned Apollo mission was scheduled. The command module caught fire, trapping three astronauts inside. The intense investigation and the modifications to Apollo delayed the program for more than a year.

The next manned mission left off on October 11, 1968. It did not start with the lunar module and remained in Earth orbit to conduct tests on Apollo's other components. The cabin for the astronauts was larger than Gemini's but still the eleven days of the mission took their toll on the astronauts. They complained about the bad food, and everyone developed a cold.

Apollo 8 that left ground on December 8, 1968, was the first space ship that took astronauts around the moon. Originally a test of the lunar module in Earth orbit was intended but plans had to be changed when it became obvious that the Soviets were catching up. The lunar module for Moon landings still was not included. Instead the service propulsion system for navigation around the moon was tested.

Two missions with further tests followed. Then the time to make history has come for the crew of Apollo 11. On July 20, 1969, four days after lift-off, Neil Armstrong put his feet on the lunar surface speaking his famous words: 'That's one small step for man . . . one giant leap for mankind.' He and Edwin Aldrin spent 21 hours on the surface of the Moon. They left a flag of the United States of America and a plaque with the following words engraved: "Here Men From Planet Earth First Set Foot Upon The Moon. July 1969 AD We Came In Peace For All Mankind." Four days later they returned to Earth as heroes.

With Apollo 11 the objectives of the program were basically met. The USA not only won the race against the Russians they also proved that it was generally possible to reach other worlds. Even if there is going to be a Mars mission it will never overshadow the great achievement of making the first trip to another planet. It will just be another step of mankind on its way to the stars.

Six other Moon missions were scheduled. One of them never reached its goal. Tragedy almost struck on Apollo 13 when on oxygen tank in the service module exploded within 321,860 kilometers of Earth. The only way to safe the lives of the astronauts was to abort the moon landing and to return to Earth by using the gravity forces of the Moon. The command module of the space ship was almost completely inactive so the crew had to spend most of the time in the lunar module. After four tense days in space Apollo 13 eventually returned back to Earth.

Apollo 17, the last mission, was launched on December 7, 1972. Like the crews of the two preceding missions they had a moonrover that allowed them to get a better overview of the lunar surface. The Apollo Program ended as Apollo 17 splashed into the pacific on December 19, 1972.


5. Other Apollo missions

5.1. Skylab

Since the earliest days of the NASA space program concepts for a space station were studied. They all failed, however, since there was no way of getting such a station into orbit. As the powerful Saturn V rockets were invented in the mid-Sixties for the Apollo program Skylab initially called the "Apollo Applications Program", was born. Leftover Apollo hardware was should be used to male longer stays of astronauts in space possible.

At first there were two concepts for the Skylab mission. The concept of the "wet" workshop was to launch one of the weaker Saturn IV-B rockets and then vent and refurbish its upper stage in space. The second concept that was later realized was the "dry" workshop.

According to the plan a Saturn IV-B upper stage was modified on ground. It was divided into two levels. The "lower" one served as the astronaut's living quarters. It had three bedrooms, a dining table, a work area, as well as, a bathroom and a shower. In the "upper" level there was a storage room and a large space for experiments.

The largest piece of equipment was the Apollo Telescope Mount (ATM). It was attached to the end of the cylindrical workshop. Its purpose was to study the sun without any atmospheric interference.

Furthermore, Skylab had an airlock module for space-walks. Space-walks were not only required to do repairs but also to change the film in the ATM and to conduct other experiments.

Skylab was launched into space by a Saturn V rocket on May 14, 1973. The crew was scheduled to follow the next day but Skylab was damaged during the start. The combined meteorite shield and sunshade was torn loose and took one of the two solar arrays with it. Ten days later a fix was worked out and the astronauts were able to go on the first of three skylab missions.

The three man crew failed had to complete the repairs as fast as possible since the missing of the sunshade caused high temperatures in the station. These conditions could have spoiled the food for the astronauts and the sensitive film material for the ATM. They succeeded in setting up a parasol as a replacement for the sunshade but failed to deploy the second solar panel which was also damaged. After two weeks the repair was finally completed so that Skylab was provided with energy. After one month the first Skylab mission was competed. Two more missions of two and three months in duration followed. Until today, Skylab 4 is the longest mission ever carried out by a U.S. astronaut. It lasted 84 days. Between the missions the space station was deactivated. On July 11, 1979 the empty Skylab station burned up in the atmosphere.

The Skylab missions provided weather scientists with some valuable data. By photographing targets on the sun and evaluating weather conditions on Earth some valuable solar orientated material was obtained. The final crew also made observations of he Comet Kohoutek that was coincidentally passing Earth. The astronauts carried out lots of other experiments. For example they found out that spiders were also able to spin webs in the state of weightlessness.


5.2. Apollo-Soyuz

Apollo-Soyuz was the last mission of the Apollo era. It was less a technical matter than it was a political one. In 1972 U.S. President Nixon and the Soviet leader Kosygin initiated the program. It was a symbol for the goodwill between the two superpowers.

American and Soviet scientists had to grant each other inside into their respective programs so that a common docking system could be designed. In preparation of the flight Soviet cosmonauts were practicing at Johnson space center, and the American crew did the same in Moscow. Flight controllers from both nations also conducted joint simulations.

Apollo 18 and Soyuz 19 left Earth within seven-and-a-half hours on July 15, 1975. Two days later Thomas P. Stafford and Alexei Leonov exchanged handshakes. The two space ships remained linked for 44 hours. During that time they ate together, exchanged gifts and flags and paid visits to each other's ships. They also conducted further docking maneuvers in which the Soyuz took over the role of the active ship. The Soviets spent five days in space. The Americans concluded their trip after nine days.


6. "Revolution" in space: the Space Shuttle

6.1. The Design of the Space Shuttle

The Space Transportation System, better known as the Space Shuttle, meant a revolution to space flight in many ways. It was the first reusable space craft, and allowed not only to take satellites into space but also to take them back to Earth. Furthermore, many of today's Shuttle flights are non-military operations



The Shuttle project was started in 1972. A spacecraft that could be used over and over again proved to be a difficult task for the constructors. Insulating Tiles that are able to stand the heat of the reentry and better engines which can survive many missions had to be invented.

Space Shuttles are very different from the previous types of space crafts. They look a little bit like airplanes and have got three main engines. These engines burn the liquid hydrogen and oxygen that are stored in the large External Tank. Most of the thrust for the lift-off, however, is derived from the two Solid Rocket Boosters which are attached to the tank. Two minutes after lift-off they have burnt out and they are dropped into the ocean for recovery. Eight minutes after he start the Shuttle has reached the orbit and the Shuttles own engines are deactivated as well.

The Space Shuttle has a 18 meter long cargo bay where additional modules can be placed. Respective to their mission the Space Shuttles can be equipped with mission specific tools or modules. One of them is the Spacelab Module. It was built by the European Space Agency and provides the astronauts with a fully equipped laboratory. It allows scientists to conduct experiments ranging in subject matter from astronomy to biomedical examinations. Another important tool is the Remote Manipulator System, a 15 meter crane. It is used to move heavy payloads such as satellites in and out of the Shuttle. The Manned Maneuvering Unit backpack changed the art of space walking. With it the astronauts could move outside their spacecraft without a connecting tether and therefore work faster in their spacesuits.

In 1995 a new capability was added to the repertoire of the Shuttle. In order to prepare for the service on the International Space station, Shuttle crews began a series of dockings with the Russian space station Mir. U.S. astronauts sometimes spent months in space so that they get used to living and working in space.

Today the Space Shuttles make up a fleet of four spacecrafts. The first one, Atlantis, entered service in 1981. It was followed by the Challenger (1983), the Discovery (1984) and the Columbia (1985), and the Endeavour (1991).


6.2. Shuttle missions

Space Shuttles usually take off with a seven-man-crew. Such a large crew allows to divide the astronauts into two categories. There are the pilots who are responsible for flying and maintaining the orbiter and there mission specialists for experiments and payloads. These specialists are not necessarily career-astronauts.

During the early missions the Space Shuttles often carried communications satellites into the sky. Sometimes three satellites were place in orbit during one single mission.

This policy changed when the greatest catastrophe in human space flight so far took the lives of seven astronauts. On January 28, 1986, the Challenger exploded just 73 seconds after lift-off. Later it was determined that a seal in one of the two Solid Rocket Boosters did not work properly due to the freezing cold temperatures that day. The Shuttle program was suspended for over two years in order to make several improvements to the other Shuttles.

The number of flights was greatly reduced as a result to the accident. Today the Shuttles are only used when a payload requires them or when human presence is absolutely necessary. The majority of the missions were of defensive or scientific nature. Most recent payloads include the decade's most important space science projects such as the Hubble Space Telescope , the Galileo Jupiter spacecraft, and the Gamma Ray Observatory. The most recent Shuttle mission was launched on December 4, 1998. The Endeavour brought a module for the International Space Station into orbit and the crew connected it to the Functional Energy Block that is already in space. The next Shuttle launch is going to be on May 20. The Discovery crew is also going to work on the International Space Station. This mission will be the 95th Shuttle mission.


7. The Mir Space Station

After Skylab Mir was the second permanent space station. Its core was launched on February 19, 1986. Over ten years later it was completed with the adding of the Remote Sensor Module. During its 13 years in orbit it was a home for 62 cosmonauts from 24 different countries.

Mir is floating 390 km above Earth. A Russian cargo and resupply vehicle is used to send science equipment and data to and from the station. Each transport also includes food and water supplies for Mir. When it is leaving the station it takes care of the removal of waste materials.

The entire complex is composed of six modules. The most important of the is the core module. It has a total length of 43 meters and contains the crew's living quarters and control area. Each cosmonaut has got a room for himself as well as a personal hygiene area. From the control area the crew has got access to every major system on board. The core has got multiple docking ports where additional modules are attached to. They also allow space craft dockings.

Mir has got four additional modules. Besides contributing to the station's energy supply and adding storage space for food and water the modules have got a special purpose. The astrophysics module Kvant-1 gathers information from far-away stars, Kvant-2 provides laboratory areas for biological research. In addition it has an airlock for space walks. The Kristall Technological Module is used for material development in a space environment, and has got a docking port that can be used with the Space Shuttle. The Remote Sensing Module contains a number of Spectrometers. Its purpose is to make observations of the Earth atmosphere.



Bibliography

David Baker: Space Flight and Rocketry
Facts on File, Inc., 1996, ISBN 0816018537

Judy A. Rumerman: Human Space Flight: A Record of Achievment
Mikaya Pr., 1998, ISBN 1265403210

David S. F. Portree: NASA's Origins and the dawn of space age
Enslow Publishers, Inc., 1995, ISBN 1876254040



The Agena was originally developed by the U.S. Airforce in 1956. Later it was modified to put satellites into precise orbits and to propel space probes towards other planets.

At a rendezvous the astronauts move their space ship within a distance of fewer than one meter and maintain this position for a few minutes or hours.










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