The primary mission of space shuttle is to transport satellites in the atmosphere or carry equipments for the astronomers in the space to assist them in their experiment. Space shuttle missions have witnessed exciting highs as well as shocking lows since last three decades. It assisted astronauts in their scientific research and missions which resulted in valuable scientific gain.
Along with the scientific success, there were serious disasters such as the Challenger, which crashed while its launch in 1986. Columbia met an accident while re-entering Texas and Discovery failed before its launch in 2005 due to the foam which broke from its fuel tank. It was grounded for improvement until 2006, when Atlantis and Discovery both carried successful space missions. Space shuttle comprises following major components:
• SRB (Solid Rocket Boosters): two rocket boosters are normally required for its launch.
• ET (External Fuel Tank): this tank transports fuel for its launch.
• Orbiter: it transports payloads and astronauts
The mission of a typical space shuttle lasts for 7 to 14 days, depending on the mission or the objective of the mission. A typical mission of the space shuttle is shown below:
GETTING INTO ORBIT ===========> ORBIT ======> RE-ENTRY ====> LANDING
(launch, ascent, orbital direction) (life in space)
The orbiter carries astronauts and satellites to the lower or upper atmosphere of the earth’s orbit with approximately 5 to 7 crew members including pilot and the commander. When the space mission of an orbiter is completed, it drops out of earth’s orbit and enters into the various layers of earth’s atmosphere till it reaches ground.
Usage of space shuttles:
• Servicing and crew replacement of ISS (International Space Station) and Mir.
• Servicing missions which includes HST (Hubble Space Telescope).
• Experiments in the Earth’s orbit (also called as LEO).
LEO manned operations such as:
• Large satellites which including HST.
• ISS manned servicing construction components.
• Multiple logistics or Space hub supplies modules.
• Transport satellites along with a booster, IUS (Inertial Upper Stage) or PAD D (Payload Assist Module) to the location where the booster transports the satellite to:
• Higher Earth’s orbit, which include:
• Observatory Chandra X-ray.
• Multiple TDRS satellites.
• 2 DSCS III communications with the satellites in their mission.
• Support for defense satellite programs.
• Interplanetary orbit, which include:
• Magellan probe
• Galileo spacecraft
• Ulysses probe
Replacement of Space Shuttles by spacecrafts:
NASA plans to retire space shuttles by 2011, and launch a new spacecraft which will not only carry astronauts, but transport cargos and passengers outside earth’s orbit to Mars or Moon. This project is called as Project Constellation.
• Commercial replacements: NASA announced contracts for cargo resupply into the ISS (International Space Station).
• Launcher vehicles: Various space vehicles are proposed such as Heavy Lift Launch Vehicle and Shuttle-Derived Launch Vehicles.
• Next generation Orbiters: X 37 is the next generation orbiters.
