Space Shuttles

Space Shuttles were the partially reusable rocket-launched vehicles designed to go into orbit around Earth. These were some of the most complex vehicles ever designed BY NASA, highly useful for carrying astronauts, satellites, and even parts of the International Space Station into space. These were also used as science labs in space for conducting scientific experiments.

The very first mission was launched in 1981. These Space Shuttles served mankind for 30 years and finally retired in 2011 with the launching of the last Space Shuttle 'Atlantis'.

Parts of a Space Shuttle

There are three main parts -

The orbiter

The orbiter is the most important part of a space shuttle. It looks like an airplane and this is a place where astronauts lived and rode. This also carries all the payload needed.

The name of the orbiters were Atlantis, Challenger, Columbia, Discovery, and Endeavour.

The solid rocket boosters

Solid rocket boosters are like thin rockets that provide lift-off for the space shuttle.

The external fuel tank

These orange tanks are filled with liquid hydrogen and liquid oxygen to provide fuel for the orbiter.

Stages of a Space Shuttle Mission

The Shuttle launches like a rocket, maneuvers in Earth orbit like a spacecraft, and lands like an airplane.

Lift off

To lift the 2.05 million kg shuttle from the pad to orbit (185 to 643 km) above the Earth., the SRBs are solid rockets that provide most of the main force or thrust (71 percent) needed to lift the space shuttle off the launch pad. In addition, the SRBs support the entire weight of the space shuttle orbiter and fuel tank on the launch pad. The John F. Kennedy Space Center on Merrit Island in Florida, United States was the launch site for the space shuttles.

SRB separation

The Solid Rocket Boosters (SRBs) operate in parallel with the main engines for the first two minutes of flight to provide the additional thrust needed for the Orbiter to escape the gravitational pull of the Earth. At an altitude of approximately 45 km (24 nautical miles), the boosters separate from the orbiter/external tank, descend on parachutes, and land in the Atlantic Ocean. They are recovered by ships, returned to land, and refurbished for reuse. The boosters also assist in guiding the entire vehicle during the initial ascent.

After solid rocket boosters get separated from the space shuttle, the whole energy load is transferred to space shuttle main engines (SSMEs) fueled by the external tank. It is now up to them to safely take the orbiter near enough to Earth orbit.

ET separation

When the Solid Rocket Boosters separate at an altitude of approximately 45 kilometers (28 miles), the external tank, with the main engines still burning, carries the orbiter piggyback to near orbital velocity, approximately 113 kilometers (70 miles) above the Earth. The now nearly empty tank separates and falls in a pre-planned trajectory with the majority of it disintegrating in the atmosphere and the rest falling into the ocean. This backbone of the shuttle is the only non-reusable part of a space shuttle.

After the separation of the external tank both the initial booster systems are gone i.e. the SRBs and now the space shuttle main engines. We are still a little away from the Earth orbit. The final push is done by two small OMS Rocket Motors which have their own hydrogen-oxygen filled tanks.

Into orbit

Once in space, the shuttle orbiter is home to the astronauts for seven to 14 days. Between this time the space shuttle does the required activities for which it is sent to space, whether it is to transport parts of the International space station or carry scientific experiments, or deposit satellite into Earth's orbit. The orbiter can be oriented so that the cargo bay doors face toward the Earth or away from the Earth, depending upon the mission objectives; in fact, the orientation can be changed throughout the mission. One of the first things that the commander will do is to open the cargo bay doors to cool the orbiter.

Re-entry

In most cases, they have been flying nose-first and upside down, so they then fire the RCS thrusters to turn the orbiter tail first. Once the orbiter is tail first, the crew fires the OMS engines to slow the orbiter down and fall back to Earth; it will take about 25 minutes before the shuttle reaches the upper atmosphere. During that time, the crew fires the RCS thrusters to pitch the orbiter over so that the bottom of the orbiter faces the atmosphere (about 40 degrees) and they are moving nose first again. Finally, they burn leftover fuel from the forward RCS as a safety precaution because this area encounters the highest heat of re-entry. Because it is moving at about 17,000 mph (28,000 km/h), the orbiter hits air molecules and builds up heat from friction (approximately 3000 degrees F, or 1650 degrees C). The orbiter is covered with ceramic insulating materials designed to protect it from this heat.

Landing

When the orbiter is 2,000 feet (610 meteres) above the ground, the commander pulls up the nose to slow the rate of descent. A parachute is deployed from the back to help stop the orbiter. The orbiter stops about midway to three-quarters of the way down the runway. After landing, the crew goes through the shutdown procedures to power down the spacecraft. During this time, the orbiter is cooling and noxious gases, which were made during the heat of re-entry, blow away. Once the orbiter is powered down, the crew exits the vehicle. Ground crews are on-hand to begin servicing the orbiter.