Humankind’s exploration of space began in the 1950s, with the first satellite, the Russian Sputnik, launched by rocket on October 4, 1957. It was followed on November 3 by another, carrying a dog named Laika.
The United States moved into space exploration on February 1, 1958, with Explorer I. A stream of similar robotic craft followed from both countries, carrying instruments that made various important discoveries.
Early space pioneering efforts built on the works of pre–World War II inventors such as the Russian schoolmaster Konstantin Tsiolkovsky, whose writings set out the basic principles for rocket propulsion, suggested multistage vehicles, and proposed liquid hydrogen as a fuel.
In the United States, Professor Robert Goddard suggested a method for reaching the moon. Goddard built rockets too, and in 1935 successfully launched one that reached a height of two kilometers.
Rocketry in World War II saw the invention of the V2 missile, with a range of around 300 kilometers, a top speed of 6,000 KPH, and a payload of over a ton. Following the war many German rocket engineers, including Wernher von Braun, were brought to the United States, while Soviet forces captured personnel and equipment from the V2 launching site of Peenemunde.
On April 12, 1961, the Soviets again led the way with the launch of Yuri Gagarin, a Russian cosmonaut, into space to become the first human to leave Earth. His mission lasted 1 hour and 48 minutes; he made a single orbit of the planet. The United States countered with a Mercury space capsule carrying Alan B. Shepard on May 5.
The effects of space travel on humans were of course largely unknown. The early manned missions resulted in considerable study of the physical damage of g-force, radiation, and weightlessness.
Rapid developments in hundreds of areas followed, as spacesuits, living quarters, and methodologies for delivering food were all pioneered, along with rapid improvements in the speed, range, and payload of rockets.
Meanwhile, robot explorers were recovering more data to inform manned missions. The first probe to journey to the Moon was launched on September 12, 1959, by the Soviet Union. Luna 2 reached its destination in 34 hours. The U.S. probes in the main were spurred by President John F. Kennedy’s address to the U.S. Congress on May 25, 1961.
The Ranger probes explored the Moon’s surface, photographing it before crashing into it; the probe therefore provided transmitted data that resolved images of around half a meter across, in contrast to the best telescopes of the time, which could only resolve to around 500 meters.
There was much debate on what the surface of the Moon actually looked like and whether it could support the landing of a heavy manned craft. Was the surface so rough no spacecraft could touch down without damage? Was the Moon dust so thick that any spacecraft would sink into huge drifts?
The Lunar Orbiter series of probes were designed to map the surface of the Moon so the best sites for exploration could be chosen. By the end of the five missions, 99 percent of the moon had been photographed to a resolution of 66 meters or better, and smaller areas had been photographed to within one meter.
The space race saw the Americans and the Russians competing as to who could reach the moon first; the dual projects were underscored by the cold war and the military implications of mastering space flight. In the end, the Russians never put a man onto the surface of the Moon but instead landed several robot explorers.
Both sides were, by the mid-1960s, progressing further down the road of manned spacecraft that could carry more than one astronaut. The rockets to launch the progressively heavier spacecraft began to increase in size, with the eventual development of the Saturn series, which still remain some of the most powerful lifting devices ever built.
In the United States, the Mercury one-person spacecraft was followed by the two-person Gemini craft. The three-person Apollo vehicles were developed, a two-part craft that included a lunar lander as well as a command section that would stay in orbit while the lander descended to the Moon’s surface.
The Russian program saw many achievements. The first female in space was Valentina Tereshkova, who completed 48 orbits in the Soviet Union’s Vostok 6 on June 16, 1963. The first space walk—a weightless venture outside a capsule—was achieved by Aleksei Leonov on March 18, 1965. The walk lasted for 10 minutes.
However, the Soviet Union’s space program was not without human cost: On April 23, 1967, the landing parachutes of the Soyuz 1 space capsule failed and cosmonaut Vladimir Komarov was killed. On January 27, 1967, the new U.S. Apollo program experienced tragedy when a fire broke out in the command module during a launch of the first piloted flight, designated AS-204.
Three astronauts died: Mercury and Gemini mission veteran Virgil Grissom; Edward White; and Roger Chaffee, an astronaut preparing for his first spaceflight. The subsequent investigation and report saw substantial improvements to mission safety. The AS-204 mission craft was renamed Apollo 1 in honor of the crew.
Powered by the enormous Saturn V three-stage rockets, the Apollo missions grew in their ability to take the astronauts further from the surface of Earth. On October 11, 1968, the first manned Apollo mission flew successfully; around the same time Russian spacecraft carrying live animals were successfully orbiting the Moon before returning to Earth.
Apollo 8 made the first human-manned circumnavigation of the Moon in December 1968. Apollo 10 was a "full dress rehearsal" of the proposed landing and carried out all of the proposed operations short of an actual descent to the lunar surface, although it descended to within nine miles of the Moon in the detached lunar module.
On July 20, 1969, after a four-day trip, Apollo 11’s lander separated from the main spacecraft with astronauts Neil Armstrong and Edwin Aldrin on board, while Michael Collins remained in orbit. The lunar module, named Eagle, successfully touched down, and, shortly afterward, filmed by the remotely controlled camera attached to the outside of the spacecraft, Armstrong emerged to back down the short ladder to the surface.
His steps were watched by millions of people via a television signal beamed back to Earth, with many millions more listening via radio. As Armstrong’s foot touched the surface of the Moon, he spoke the words, "That’s one small step for a man, one giant leap for mankind". Mankind had reached another world.
A total of seven lunar landings were made, with significant achievements made on each mission. Some 381.6 kilograms of lunar rocks were brought back to Earth, and each successive landing after Apollo 11 left behind an automated surface laboratory. The last three missions carried extremely sophisticated mapping cameras, and other instruments measured magnetic fields, chemical composition, and radioactivity.
Craft Failure
Apollo 13’s mission was aborted due to craft failure. An oxygen tank on the spacecraft had blown up and the normal supply of electricity, light, and water to the craft was lost around 200,000 miles from Earth.
A unique and innovative program of rigged repairs and procedure invention followed, resulting in the eventual safe return of the three astronauts to Earth. Apollo missions continued until December 1972, with different sites visited and a wheeled lunar rover successfully deployed to carry astronauts further from the spacecraft.
The missions increased the duration of time spent on the surface from hours to days. Twelve astronauts walked on the lunar surface. The last astronaut to leave the Moon was scientist Jack Schmitt.
Further space exploration programs commenced with Skylab, a section of a Saturn V rocket that was successfully placed in orbit and visited on several occasions by teams of astronaut/scientists who stayed in residence for ever-lengthening periods to conduct experiments. The program terminated in 1979.
A Soviet-American rendezvous in space, the Apollo-Soyuz mission, took place in 1975. The development of the space shuttle, a reusable craft capable of returning in a glide to Earth’s surface, began in 1970, centering around the idea of a cheaper alternative to previous craft.
The program used these spacecraft from their first flight in 1981 until the present. The shuttle fleet can each carry a payload of 30,000 kilograms to orbit. Mission loads have consisted of satellites, experiments, and materials for the International Space Station.
The Soviets also pursued a permanent presence in space. A series of space stations called Salyut were launched, using Soyuz spacecraft on ferry missions. In 1986 Salyut was followed by the modular space station Mir.
Following improved relations between Russia and other nations at the end of the cold war, Russian cosmonauts joined with the other countries contributing to, and working within, the International Space Station.
Stark Reminder
Space flight is not without its hazards, as was discovered in the early days of space exploration with the loss of the Soyuz 1 and Apollo 1 crews. Improvements in safety through redesign and development of spacecraft and propulsion systems have greatly reduced risk of catastrophic failure.
Nevertheless, the severe stresses placed on spacecraft and their systems, together with the risk associated with the application of cutting-edge technology, continue to make manned spaceflight inherently dangerous. Stark reminders of this were the loss of the spacecraft and crew of the space shuttles Challenger and Columbia.
The Hubble Space Telescope is the largest astronomical telescope ever sent into space. Launched in 1990 by a space shuttle, the telescope’s placement outside Earth’s atmosphere gives it a unique view of the universe.
Built by the Lockheed Missiles and space company, the space telescope has a length of 13.3 meters, or 43 feet 6 inches; a diameter of 3.1–4.3 meters, or 10–14 feet; and a weight of 11,600 kilograms, or 25,500 pounds.
NASA named the world's first space-based optical telescope after the U.S. astronomer Edwin P. Hubble. Dr. Hubble confirmed an "expanding" universe, which provided the foundation for the big bang theory.
With a mission duration of up to 20 years, Hubble is visited regularly by space shuttle crews for regular servicing. At an altitude of 380 miles (612 kilometers) in a low-Earth orbit, the telescope completes an orbit of Earth every 97 minutes. Sensitive to ultraviolet through near infrared light, the telescope relays to Earth three to four gigabytes of information per day.
Powered by two 25-foot solar panels, the telescope has revealed new information on the age of the universe, made findings on black holes, and provided visual proof that dust disks around young stars are common, reinforcing the assumption that planetary systems are plentiful in the universe.
Hubble's Replacement
Scheduled for launch in 2011, the James Webb Space Telescope is intended to replace Hubble. This telescope will see objects 400 times fainter than those visible with Earth-based telescopes. By contrast, the Hubble can see objects 60 times fainter than those visible with Earth-based telescopes.
The first components for the International Space Station were taken into orbit in 1998, and the station received its first crew on November 2, 2000, marking the first day a permanent human presence in space was achieved.
The space station has grown and evolved into an unprecedented laboratory complex. Offering a microgravity environment that cannot be duplicated on Earth, the station furthers knowledge of science and of how the human body functions for extended periods of time in space.
By the time the station had been operating for five years, 89 scientific investigations had been conducted. A complete characterization study of the radiation environment in the station was done, with evaluation of models of radiation shielding by the station’s structure.
With 15,000 cubic feet of habitable volume assembled by late 2005, the space station at that point had more room than a conventional three-bedroom house. Astronauts and scientists from a variety of nations have visited and worked in the space station.
Civilian and private missions into space have been achieved. The California millionaire and former NASA rocket scientist Dennis Tito was the first private space tourist to visit the ISS for a 10-day excursion in April 2001.
Test pilot Mike Melvill took the privately built rocket plane SpaceShip One to an altitude of more than 100 kilometers, the acknowledged point at which space begins, on July, 12, 2004.
Robot explorers have also achieved an enormous amount in the conquest of space. The first interplanetary explorer, the United States’ Mariner II, was launched on August, 26, 1962, to explore Venus and successfully reported a high surface temperature and the absence of a magnetic field.
In January 2004 two NASA robot explorers named Spirit and Opportunity landed on Mars. The six- wheeled craft crawled over the surface, measuring, photographing, and analyzing, and surprised their controllers by continuing to function for over a year, during which time they traveled for several miles.
On December 25, 2004, the NASA Cassini spacecraft, nearing Saturn, released the European Space Agency’s Huygens probe toward the surface of the ringed planet’s largest moon, Titan. Parachuting to the Moon’s surface, the probe’s cameras and spectrometers analyzed the chemical composition of Titan and transmitted data back to scientists on Earth.
Other probes have been sent to all of the planets in the solar system, including distant Pluto with the launch of the New Horizons probe in January 2006. Some probes have had lengthy careers and considerable success.
The Pioneer space probe, launched on March 2, 1972, was the first spacecraft to travel through the asteroid belt and the first spacecraft to make direct observations and obtain close-up images of Jupiter. It made its closest encounter with Jupiter on December 3, 1973, passing within 81,000 miles.
Pioneer’s last, very weak signal was received on January 23, 2003. Pioneer 10 continues into interstellar space, heading for the red star Aldebaran, about 68 light years away. It will take Pioneer over 2 million years to reach its destination.
Another development of the post-Moon program has been the space community’s understandings of asteroid dangers. A "dinosaur-killer" strike is now thought to be avoidable, due to a program of surveying and tracking all heavenly bodies.
Such ambitious ideas have been supported by the success of missions such as the Stardust spacecraft, launched in 1999. This mission managed to capture particles from a comet beyond the Earth-Moon orbit and return them to Earth.
Other aspects of space exploration are numerous. The discovery of other planets orbiting distant stars has been made possible; the Earth is ringed by satellites enabling advanced communications and a Global Positioning System (GPS); and superior meteorology and detailed imaging have been developed. Various spin-offs from the space program for the everyday world include such variables as the development of freeze-dried foods and materials such as Teflon.
Progress has been not as fast as science fiction written from the 1930s to the 1980s depicted—space flight has proved expensive and difficult, and the manned Moon bases and Martian cities have not happened.
However, other nations besides the United States and the Soviet Union—a collective European approach and manned missions from China—have begun space exploration and plans are under way to see a human presence on both the Moon and Mars.
Two basic difficulties have to be overcome if human exploration of other stars and their solar systems is to succeed. The first is the speed of the spacecraft. The fastest vessel ever built (by 2006) was the New Horizons probe, which achieved a speed shortly after launch of 10.07 miles per second, or 36,256 MPH. The nuclear-powered craft crossed the Moon’s orbit around nine hours after liftoff. Even at this speed, the estimated mission duration to Pluto is around nine years.
If the mission were manned, this would mean an overall duration of 18 years traveling plus the exploration time. If this craft’s speed were applied to reach the nearest star system to Earth, the mission time would be hundreds of years. Therein lies the second major problem—the duration humans can withstand space conditions.
The long-term effects of weightless space flight are still being studied, but it is doubtful that such missions could be withstood by a human crew. Scientists believe the craft would have to have some sort of gravitational compensation. A manned, one-way, long-term mission is also an unknown, although science fiction has done a great deal to explore both of these issues.
Indeed, space flight may have provided some answers by extrapolating various scenarios from the work of physicists that may get around interstellar exploration problems.
If space is not an empty vacuum and contains distortions, as has been proved, then the "warps" in space may provide points where great distances can be surpassed, rather in the way a fly can travel from one end of a curved scarf to the other end by simply flying between the two points rather than walking the entire length of the scarf.
There may also be ways to build spacecraft that fly at much faster speeds; light sails, antimatter rockets, and drives utilizing alternative theories of gravity and electromagnetism might allow much greater speeds. But then other problems arise: that of the relativity time-space equation, for example, and how to get humans to cope with the acceleration and deceleration speeds such a spacecraft would demand.
Although the difficulties of exploring beyond the solar system are great, they may not be insurmountable. One fact remains: If humans want to survive beyond the certain degradation of our own star and its planetary system, then space exploration must be continued.
