Astro Fisika: Indonesia Space Flight Society

Sunday 17 August 2008

Indonesia Space Flight Society

Indonesia Space Flight Society
~Masyarkat Penerbangan Luar Angkasa Indonesia~

Add & Edited By:

Arip Nurahman & Dian Hadiana (IT Telkom, CEO. Seneby Corp.)

Department of Physics,
Faculty of Sciences and Mathematics
Indonesia University of Education
and
Follower Open Course Ware at Massachusetts Institute of Technology, Cambridge.
USA

Spaceflight is the use of space technology to fly a spacecraft into and through outer space. Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other earth observation satellites.

A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of the Earth. Once in space, the motion of a spacecraft both when unpropelled and when under propulsion is covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.

History

Main article: History of spaceflight

See also: Timeline of spaceflight

The realistic proposal of space travel goes back to Konstantin Tsiolkovsky. His most famous work, "Исследование мировых пространств реактивными приборами" (The Exploration of Cosmic Space by Means of Reaction Devices), was published in 1903, but this theoretical work was not widely influential outside of Russia.

Spaceflight became an engineering possibility with the work of Robert H. Goddard's publication in 1919 of his paper 'A Method of Reaching Extreme Altitudes'; where his application of the de Laval nozzle to liquid fuel rockets gave sufficient power that interplanetary travel became possible. This paper was highly influential on Hermann Oberth and Wernher Von Braun, later key players in spaceflight.

The first rocket to reach space was a prototype of the German V-2 Rocket, on a test flight on October 3, 1942, although sub-orbital flight is not considered a spaceflight in Russia. On October 4, 1957, the Soviet Union launched Sputnik 1, which became the first artificial satellite to orbit the Earth. The first human spaceflight was Vostok 1 on April 12, 1961, aboard which Soviet cosmonaut Yuri Gagarin made one orbit around the Earth.

Rockets remain the only currently practical means of reaching space. Other non-rocket spacelaunch technologies such as scramjets still fall far short of orbital speed.

Earth-launched spaceflight

Reaching space

Proton Rocket heading for space

The most commonly used definition of outer space is everything beyond the Kármán line, which is 100 kilometers (62 mi) above the Earth's surface. (The United States sometimes defines outer space as everything beyond 50 miles (80 km) in altitude.)

In order for a projectile to reach outer space from the surface, it needs a minimum delta-v. This velocity is much lower than escape velocity.

It is possible, indeed routine, for a spacecraft to leave a celestial body without reaching the surface escape velocity of a body by propelling itself after take-off. However, it is more fuel-efficient for a craft to burn its fuel close to the ground as possible, keeping escape velocity a consideration.

Sub-orbital spaceflight

Main article: Sub-orbital spaceflight

On a sub-orbital spaceflight the spacecraft reaches space, but does not achieve orbit. Instead, its trajectory brings it back to the surface of the Earth. Suborbital flights can last many hours. Pioneer 1 was NASA's first space probe intended to reach the Moon. A partial failure caused it to instead follow a suborbital trajectory to an altitude of 113,854 kilometers (70,746 mi) before reentering the Earth's atmosphere 43 hours after launch.

On May 17, 2004, Civilian Space eXploration Team launched the GoFast Rocket on a suborbital flight, the first amateur spaceflight. On June 21, 2004, SpaceShipOne was used for the first privately-funded human spaceflight.

Orbital spaceflight

Main article: Orbital spaceflight

A minimal orbital spaceflight requires much higher velocities than a minimal sub-orbital flight, and so it is technologically much more challenging to achieve. To achieve orbital spaceflight, the tangential velocity around the Earth is as important as altitude. In order to perform a stable and lasting flight in space, the spacecraft must reach the minimal orbital speed required for a closed orbit.

Leaving orbit

Main article: Escape velocity

See also: Direct ascent

Achieving a closed orbit is not essential to interplanetary voyages, for which spacecraft need to reach escape velocity. Early Russian space vehicles successfully achieved very high altitudes without going into orbit. In its early Apollo mission planning NASA considered using a direct ascent to the moon, but abandoned that idea later due to weight considerations. Many robotic space probes to the outer planets use direct ascent -- they do not orbit the earth before departing.

Plans for future crewed interplantary spaceflight missions often include final vehicle assembly in Earth orbit, such as NASA's Project Orion and Russia's Kliper/Parom tandem.

Other ways of reaching space

Main article: Non-rocket spacelaunch

Many ways other than rockets to reach space have been proposed. Ideas such as the Space Elevator, while elegant are currently infeasible; whereas electromagnetic launchers such as launch loops have no known show stoppers. Other ideas include rocket assisted jet planes such as Skylon or the trickier scramjets. Gun launch has been proposed for cargo, but this would incinerate the cargo due to air friction.

Launch pads and spaceports, takeoff

Main article: Launch pad

Saturn V on the launch pad before the launch of Apollo 4

A launch pad is a fixed structure designed to dispatch airborne vehicles. It generally consists of a launch tower and flame trench. It is surrounded by equipment used to erect, fuel, and maintain launch vehicles. A spaceport, by way of contrast, is designed to facilitate winged launch vehicles and uses a long runway. Both spaceport and launch pads are situated well away from human habitation for noise and safety reasons.

A launch is often restricted to certain launch windows. These windows depend upon the position of celestial bodies and orbits relative to the launch site. The biggest influence is often the rotation of the Earth itself. Once launched, orbits are normally located within relatively constant flat planes at a fixed angle to the axis of the Earth, and the Earth rotates within this orbit.

Reentry and landing/splashdown

Reentry

Main article: Atmospheric reentry

Vehicles in orbit have large amounts of kinetic energy. This energy must be discarded if the vehicle is to land safely without vaporizing in the atmosphere. Typically this process requires special methods to protect against aerodynamic heating. The theory behind reentry is due to Harry Julian Allen. Based on this theory, reentry vehicles present blunt shapes to the atmosphere for reentry. Blunt shapes mean that less than 1% of the kinetic energy ends up as heat that reaches the vehicle and the heat energy instead ends up in the atmosphere.

Landing

Main article: Splashdown (spacecraft landing)

Recovery of Discoverer 14 return capsule

The Mercury, Gemini, and Apollo capsules all landed in the sea. These capsules were designed to land at relatively slow speeds. Russian capsules for Soyuz make use of braking rockets as were designed to touch down on land. The Space Shuttle glides into a touchdown at high speed.

Recovery

After a successful landing the spacecraft, its occupants and cargo can be recovered. In some cases, recovery has occurred before landing: while a spacecraft is still descending on its parachute, it can be snagged by a specially designed aircraft. This mid-air retrieval technique was used to recover the film canisters from the Corona spy satellites.

Expendable launch systems

Main article: Expendable launch system

All current spaceflight except NASA's Space Shuttle and the SpaceX Falcon 1 use multi-stage expendable launch systems to reach space.

Reusable launch systems

Main article: Reusable launch system

The Space Shuttle Columbia seconds after engine ignition

The first reusable spacecraft, the X-15, was air-launched on a suborbital trajectory on July 19, 1963. The first partially reusable orbital spacecraft, the Space Shuttle, was launched by the USA on the 20th anniversary of Yuri Gagarin's flight, on April 12, 1981. During the Shuttle era, six orbiters were built, all of which have flown in the atmosphere and five of which have flown in space. The Enterprise was used only for approach and landing tests, launching from the back of a Boeing 747 and gliding to deadstick landings at Edwards AFB, California. The first Space Shuttle to fly into space was the Columbia, followed by the Challenger, Discovery, Atlantis, and Endeavour. The Endeavour was built to replace the Challenger when it was lost in January 1986. The Columbia broke up during reentry in February 2003.

The first (and so far only) automatic partially reusable spacecraft was the Buran (Snowstorm), launched by the USSR on November 15, 1988, although it made only one flight. This spaceplane was designed for a crew and strongly resembled the U. S. Space Shuttle, although its drop-off boosters used liquid propellants and its main engines were located at the base of what would be the external tank in the American Shuttle. Lack of funding, complicated by the dissolution of the USSR, prevented any further flights of Buran.

Per the Vision for Space Exploration, the Space Shuttle is due to be retired in 2010 due mainly to its old age and high cost of the program reaching over a billion dollars per flight. The Shuttle's human transport role is to be replaced by the partially reusable Crew Exploration Vehicle (CEV) no later than 2014. The Shuttle's heavy cargo transport role is to be replaced by expendable rockets such as the Evolved Expendable Launch Vehicle (EELV) or a Shuttle Derived Launch Vehicle.

Scaled Composites SpaceShipOne was a reusable suborbital spaceplane that carried pilots Mike Melvill and Brian Binnie on consecutive flights in 2004 to win the Ansari X Prize. The Spaceship Company will build its successor SpaceShipTwo. A fleet of SpaceShipTwos operated by Virgin Galactic should begin reusable private spaceflight carrying paying passengers in 2008 .