Space telescopesSpace telescopes are launched as satellites so we can study the Universe without interference from Earth’s atmosphere.
First space telescopeThe first space telescope was Copernicus, sent up in 1972. The most famous is the Hubble space telescope, launchttp://educational-wealth.blogspot.com/2014/02/what-are-planets.htmlhed from a space shuttle in 1990. Different space telescopes study all the different forms of radiation that make up the electromagnetic spectrum .
Hubble space telescope
In 1994 the crew of Discovery mended the Hubble space telescope in orbit. The entire centre section of the orbiter is a cargo bay which can be opened in space so satellites can be placed in orbit
Helios telescopeHelios was one of many space telescopes studying the Sun. X-rays can only be picked up by space telescopes such as the Einstein, ROSAT and XTE satellites. Gamma rays can only be picked up by space telescopes like the Compton Gamma-Ray Observatory. The Hubble space telescope’s main mirror was faulty when it was launched, but a replacement was fitted by shuttle astronauts in 1994.
SatellitesA One of the many hundreds of satellites now in Earth’s orbit. Satellites are objects that orbit planets and other space objects. Moons are natural satellites. Spacecraft sent up to orbit the Earth and the Sun are artificial satellites. The first artificial satellite was Sputnik 1, launched on 4 October 1957.
About 100 artificial satellites are now launched every year. A few of them are space telescopes. Communications satellites beam everything from TV pictures to telephone calls around the world.
Observation satellitesObservation satellites scan the Earth and are used for purposes such as scientific research, weather forecasting and spying.
Navigation satellitesNavigation satellites such as the Global Positioning System (GPS) are used by people such as airline pilots to work out exactly where they are.
Satellites are launched at a particular speed and trajectory (path) to place them in just the right orbit.
The lower a satellite’s orbit, the faster it must fly to avoid falling back to Earth. Most satellites fly in low orbits, 500 km above the Earth. A geostationary orbit is 35,786 km up. Satellites in geostationary orbit over the Equator always stay in exactly the same place above the Earth.
COBE satelliteThe COBE satellite picks up microwave radiation which may be left over from the Big Bang.
IRAS satelliteThe IRAS satellite studied infrared radiation from objects as small as space dust. Space telescopes that study ultraviolet rays from the stars included the International Ultraviolet Explorer (IUE), launched in 1978.
Polar orbiting satellitesPolar orbiting satellites circle the Earth from pole to pole about 850 km up, covering a different strip of the Earth’s surface on each orbit.
Communications satellitesCommunications satellites act as relay stations, receiving signals from one location and transmitting them to another.
SpacecraftThere are three kinds of spacecraft -
2- unmanned probes
Spacecraft have double hulls to protect against other space objects that crash into them. Manned spacecraft must also protect the crew from heat and other dangerous effects of launch and landing. Spacecraft windows have filters to protect astronauts from the Sun’s dangerous ultraviolet rays.
Flying saucersSupposed alien spacecraft are sometimes called ‘flying saucers’. Modern science-fiction portrays them as more like this.
Space travel RadiatorsSpace travel Radiators on the outside of the spacecraft lose heat, to stop the crew’s body temperatures overheating the craft.
Manned spacecraftManned spacecraft have life-support systems that provide oxygen to breathe, usually mixed with nitrogen (as in ordinary air).
Charcoal filters out smells. The US space shuttle, the first reusable spacecraft, has made manned space flights out into Earth’s orbit and back almost a matter of routine. The carbon dioxide that crews breathe out is absorbed by pellets of lithium hydroxide.
Spacecraft toiletsSpacecraft toilets have to get rid of waste in low gravity conditions. Astronauts have to sit on a device which sucks away the waste.
Solid waste is dried and dumped in space, but the water is saved. To wash, astronauts have a waterproof shower which sprays them with jets of water from all sides and also sucks away all the waste water.
Weightlessness of spaceThe weightlessness of space means that most astronauts sleep floating in the air, held in place by a few straps.
RocketsRockets provide the huge thrust needed to beat the pull of Earths gravity and launch a spacecraft into space. The space shuttle uses a huge fuel tank and two booster rockets to launch.
After launch the booster rockets fall away from the shuttle.
The shuttle uses its own power to complete its mission before returning to Earth. Rockets burn propellant , to produce hot gases that drive the rocket upwards.
Rocket's fuelRocket propellant comes in two parts -a solid or liquid fuel, and an oxidizer.
Solid fuelSolid fuel is a rubbery substance that contains hydrogen, and it is usually used in additional, booster rockets.
Liquid fuelLiquid fuel is usually liquid hydrogen, and it is typically used on big rockets. There is no oxygen in space, and the oxidizer supplies the oxygen needed to burn fuel.
It is usually liquid oxygen (called ‘lox’ for short).
First liquid fuel rocketThe first rockets were made 1000 years ago, in China. Robert Goddard launched the very first liquid-fuel rocket in 1926. The German V2 war rocket, designed by Werner von Braun, was the first rocket capable of reaching space.
Space shuttleUnlike other spacecraft, the space shuttle can land like an aeroplane ready for another mission. But even the shuttle has to be launched into space on the back of huge rockets. These soon fall back to Earth, where they are collected for reuse. The most powerful rocket ever was the Saturn 5 that sent astronauts to the Moon.
The space shuttle is a reusable spacecraft, made up of a 37.2-m-long orbiter, two big Solid Rocket Boosters (SRBs), three main engines and a tank. The shuttle orbiter is launched into space upright on SRBs, which fall away to be collected for reuse.
Orbital velocityThe biggest problem when launching a spacecraft is overcoming the pull of Earth’s gravity. To escape Earth’s gravity, a spacecraft must be launched at a particular velocity .
The minimum velocity needed for a spacecraft to combat gravity and stay in orbit around the Earth is called the orbital velocity.
Escape velocityWhen a spacecraft reaches 140 percent of the orbital velocity, it is going fast enough to break free of Earth’s gravity.
This is called the escape velocity.
Launch vehiclesThe thrust (push) that launches a spacecraft comes from powerful rockets called launch vehicles. Launch vehicles are divided into sections called stages, which fall away as their task is done.
First stage of Launch vehiclesThe first stage lifts everything off the ground, so its thrust must be greater than the weight of launch vehicle plus spacecraft.
It falls away a few minutes after take off.
Second stage of Launch vehiclesA second stage is then needed to accelerate the spacecraft towards escape velocity. After the launch stages fall away, the spacecraft’s own, less powerful, rocket motors start. To stay in orbit 200 km up, a spacecraft has to fly at over 8 km per second.
Wings and space craftA spacecraft cannot use wings to lift it off the ground, as wings only work in the lower atmosphere. Instead, launch rockets must develop a big enough thrust to power them straight upwards, overcoming gravity with a mighty blast of heat.
Landing of OrbitarsWhen the mission is over the orbiter lands like a glider. The orbiter can go as high as a near-Earth orbit, some 300 km above the Earth. The maximum crew is eight, and a basic mission is seven days, during which the crew work in shirtsleeves. Orbiter toilets use flowing air to suck away waste. The orbiter can carry a 25,000 kg-load in its cargo bay.
First four orbitersThe first four orbiters were named after old sailing ships - Columbia, Challenger, Discovery and Atlantis.
Engines of orbitarsThe three main engines are used only for lift-off.
Orbital Manoeuvring System (OMS)In space, the small Orbital Manoeuvring System (OMS) engines take over.
The Reaction Control System (RCS)The Reaction Control System (RCS) makes small adjustments to the orbiter’s position. In future, faster space planes may take over from shuttles, so that humans can visit other planets.
Tragedy with shuttle in 1986The 2003 shuttle programme was brought to an untimely end when the Columbia exploded killing all seven crew members. This tragedy echoed the ill-fated Challenger programme of 1986.
Space probes Voyager 2 used Saturn’s gravity to fly on to Uranus and Neptune. Space probes are automatic, computer-controlled unmanned spacecraft sent to explore space. The first successful planetary probe was the USA’s Mariner 2, which flew past Venus in 1962. Mariner 10 reached Mercury in 1974.
Vikings 1 and 2 landed on Mars in 1976. Voyager 2 has flown over six billion km and is heading out of the Solar System after passing close to Jupiter (1979), Saturn (1980), Uranus (1986) and Neptune (1989). Most probes are ‘fly-bys’ which spend just a few days passing their target and beaming back data to Earth.
SlingshotTo save fuel on journeys to distant planets, space probes may use a nearby planet’s gravity to catapult them on their way.
This is called a slingshot.
Space probesIn the first ten years of the 21st century, more than 50 space probes will be sent off to visit planets, asteroids and comets, as well as to observe the Moon and the Sun. Space probes will bring back samples from Mars, comets and asteroids early in the 21 st century.
Probes are equipped with a wealth of equipment for recording data and beaming it back to Earth.
Terrestrial Planet Finder (TPF)Terrestrial Planet Finder (TPF) may be used to detect planets circling nearby stars in 2009.
Voyagers 1 and 2The Voyagers are a pair of unmanned US space probes, launched to explore the outer planets. Voyager 1 was launched on 5 September 1977.
It flew past Jupiter in March 1979 and Saturn in November 1980, then headed onwards.Jupiter's orange moon. Voyager 2 discovered sulphur volcanoes on this moon, in 1979. on a curved path that will take it out of the Solar System altogether. Voyager 2 travels more slowly.
Although launched two weeks earlier than Voyager 1, it did not reach Jupiter until July 1979 and Saturn until August 1981. The Voyagers used the ‘slingshot’ of Jupiter’s gravity to hurl them on towards Saturn. While Voyager 1 headed out of the Solar System, Voyager 2 flew past Uranus in January 1986 and Neptune on 24 August 1989.
It took the first close-up photographs of the two planets. The Voyagers revealed volcanoes on Io, one of Jupiter’s Galilean moons. Voyager 2 found ten unknown moons around Uranus. Voyager 2 found six unknown moons and three rings around Neptune. Voyager 2 reached Neptune in 1989, revealing a wealth of new information about this distant planet. Voyager 2 will beam back data until 2020 as it travels beyond the edges of the Solar System.