Main->Readings->5th Grade Readings->Human Spaceflight->Part 6
Vocabulary |
After the successful Moon landings, human beings continued with manned space flight, but their goals became more practical and closer to home. The Apollo program continued, but its projects were all done in orbit, and the Soviet Soyuz spacecraft made similar experiments. The U.S.A. launched the Skylab space station in 1973, and the U.S.S.R. sent up a space station, Salyut, from 1974 to 1977. Showing that the "cold war" between the nations was beginning to lessen, the American Apollo 18 and Soviet Soyuz 19 missions docked together in space, leading the way for more collaboration among different countries in space exploration.
However, all these missions were alike in one way, and it had to do with one of the old problems of spaceflight: re-entry. In order to get a spacecraft back to Earth from orbit, it had to fall back, hanging from parachutes. Scientists calculated the fall so the capsule would land in the ocean and cause the least damage, but it was difficult to control the path it followed and there was always a risk of parachute failure, bad weather, or human error.
The U.S. Columbia changed all that on April 12, 1981. Columbia was the first space shuttle. To " shuttle" means to move back and forth, and that was what Columbia did; it moved back and forth from orbit to the Earth.
The shuttle was a re-usable combination rocket-ship and glider plane which could take off from earth like a rocket and glide back to Earth like a plane. With astronauts John Young and Robert Crippen aboard, it took off from the Earth attached to the side of a huge fuel tank with two big rockets on either side.
Liftoff of Space Shuttle Columbia
Image courtesy of NASA,
Kennedy Space Center,
Astronomy
Picture of the Day
http://antwrp.gsfc.nasa.gov/apod/ap950806.html
When the rockets were used up, they dropped back to Earth, and when Columbia used the fuel in the tank, the tank fell back as well, and Columbia continued on into orbit. So far, the mission was similar to all the ones that had gone before, a multi-stage take-off. But it was the re-entry that was different.
After 36 orbits, 170 miles up, at a speed of 17,300 miles an hour, the crew turned Columbia tail forwards and fired the engines to slow it down. It began to fall out of orbit, and as it did the crew turned it to face forward again. At 75 miles above the Earth, it began to re-enter the atmosphere, glowing with the heat of friction, but now Columbia's new design began to work.
Unlike every spacecraft that had come before, Columbia had wings, like an airplane or a glider. The body of the shuttle was thicker than an ordinary plane and the wings were short and stubby, but they did the job. As the air got thicker, pilot Young moved the shuttle in gentle curves to slow it down and brought it to the correct speed. Copilot Crippen lowered the landing gear. At 214 miles an hour, still faster than a jet plane landing, Columbia touched down in the California desert and kept rolling until it finally came to a stop.
The shuttle was the first spacecraft to actually fly back from space. Its gentle landing and its careful design also meant something else. Columbia could be re-used. In fact, NASA was still sending Columbia on missions in the year 2003, over 20 years after it was first launched.
The United States built more shuttles after Columbia: Challenger, Discovery, Atlantis, and the latest one, Endeavor. All the shuttles were named after famous sea vessels which had made important discoveries.
The shuttles work as laboratories, moving vans, repair trucks, and supply vehicles in space. Aboard the shuttles, astronauts conduct experiments, carry satellites to orbit and bring them back down, fix orbiting objects, and bring supplies and materials to space stations. A shuttle must reach speeds of about 17,500 mph (28,000 kilometers per hour) to remain in orbit, though speed depends on how far up it is, normally from 190 miles to 330 miles, depending on its mission.
After it had made nine successful missions, the Challenger shuttle encountered disaster on January 28, 1986. Overconfident, NASA had rushed its program while trying to save money, and Challenger exploded only 73 seconds after take-off on that chilly Florida day. All seven people aboard the ship were killed, including Christa McAuliffe. An elementary school teacher, she had won a competition among many teachers across the country to be the first "Teacher in Space," and her class, excited, was in the crowd at Cape Canaveral watching. Everyone was horrified, and many people remember exactly where they were when they were watching the disaster.
Christa McAuliffe
Image Courtesy of NASA
Johnson
Space Center Digital Image Collection
http://images.jsc.nasa.gov/images/pao/STS51L/10062265.jpg
The space shuttle program ground to a halt and a thorough investigation was conducted. There were no shuttle flights for almost three years. Many projects were put to one side while the country tried to figure out what had gone wrong.
It turned out that a seal (an "O-ring") on the rocket booster had not worked properly because of the unusually cold weather. Engineers had warned that it might not work, and the flight had been canceled three times, but project directors had decided to go ahead after all.
Less confident, the United States finally continued with its space shuttle program, improving the safety of the missions. The safety record improved and for 17 years, there were no major problems with the shuttle. Then, on February 1, 2003, in what was to be one of its last missions, the first space shuttle Columbia broke up over Texas just 18 minutes before it was supposed to arrive back on the ground from space. Seven astronauts, including the first Israeli astronaut, died. Once again, NASA was shaken and the country was terribly sad. Yet too many people depended on the shuttle now. There were many projects still to be finished.
STS-107 Flight: January 16-February 1, 2003
Mission Specialist David M. Brown, Commander Rick D. Husband,
Mission Specialist Laurel B. Clark, Mission Specialist
Kalpana Chawla,
Payload Specialist Michael P. Anderson, Pilot William C. McCool,
Payload Specialist Ilan Ramon, Israel
Image courtesy of NASA, http://www.nasa.gov/photos.html
The United States once again remembered that no matter how safe the space program seemed, disaster was always possible.
Manned space exploration is very different from the way it was in the 1960s. Often, unless there is a disaster, people don't even realize that a shuttle mission is in progress or that people are moving about and working in orbit over our heads. Foreign mission specialists often go up in the space shuttle, and nobody thinks about it. An International Space Station is being built by the United States, Russia, and a number of other countries, but news articles about it often go unnoticed. The Soviet Union, once our greatest competitor in world politics and spaceflight, does not even exist any more; it broke apart and many of its former parts are struggling for money or fighting with one another. The United States is planning a manned mission to Mars in a few years, yet news about its plans rarely reaches the front page of the newspapers. Manned space exploration no longer seems such a great adventure. It is part of everyday life now.
Yet if you look at the size of the universe compared to the size of the Earth, it is as if we were ants floating on a leaf in the middle of the ocean, saying to one another, "Who needs to learn to swim? We have everything we need right here."
Earthrise
Image courtesy of NASA
30th anniversary of Apollo 11 : 1969 - 1999
http://nssdc.gsfc.nasa.gov/planetary/lunar/apollo_11_30th.html
Go on to Appendix: Newton's Laws and United Nations Treaty on Outer Space
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This page last modified on February 2, 2003