­ When the orbiter is 2,000 ft (610 m) above the ground, the commander pulls up the nose to slow the rate of descent. The pilot deploys the landing gear and the orbiter touches down. The commander brakes the orbiter and the speed brake on the vertical tail opens up. A parachute is deployed from the back to help stop the orbiter. The parachute and the speed brake on the tail increase the drag on the orbiter. The orbiter stops about midway to three-quarters of the way down the runway.

Photo courtesy NASA
Space shuttle orbiter touching down
After landing, the crew goes through the shutdown procedures to power down the spacecraft. This process takes about 20 minutes. 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.

Photo courtesy NASA
Parachute deployed to help stop the orbiter on landing
Photo courtesy NASA
Orbiter being serviced just after landing
The shuttle's technology is constantly being updated. Next, we'll look at future improvements to the shuttle.

Space Shuttle Improvements

Photo courtesy NASA

As mentioned previously, falling debris (foam insulation) from the ET damaged the shuttle orbiter, leading to Columbia's break up upon re-entry. To bring the shuttles back to flight status, NASA has focused on three major areas:

Let's take a closer look at each of these.
ET Redesign
The ET holds cold liquefied gases as fuel (oxygen, hydrogen). Because the temperatures are so cold, water from the atmosphere condenses and freezes on the surfaces of the ET and the fuel lines leading in to the orbiter. Ice can fall off the ET itself or cause the ET foam insulation to crack and fall off. In addition to ice, if any of the liquid gas were to leak and get under the foam, it would expand and cause the foam insulation to crack. So much of the ET redesign has focused on eliminating places where condensation can occur.

Photo courtesy NASA
ET redesign

First, the bipod fitting is the forward point where the ET attaches to the underside of the orbiter. Engineers and technicians discovered that this point is especially susceptible to icing. In the past, ramps of foam insulation over this part prevented ice buildup; however, this insulation fell off frequently, thereby presenting a danger to the orbiter.

Photo courtesy NASA. Photo credit: Lockheed martin/NASA Michoud
The foam ramps that protected ET bipod fittings from ice build up (above) have been replaced with a new joint that is electrically heated (below).

Photo courtesy NASA. Photo credit: Lockheed martin/NASA Michoud

In the redesign, the insulation has been removed and the fitting now mounts across the top of a copper plate, which contains electric heaters. The heater can warm the fitting and prevent ice buildup.
Second, liquid nitrogen is used to purge the intertank connection of any potentially explosive hydrogen gas. However, liquid nitrogen can freeze around the bolts in that area and cause foam insulation to break off. The bolts in that area have been redesigned to prevent leaks of liquid nitrogen.

Photo courtesy NASA. Photo credit: Lockheed martin/NASA Michoud
The foam ramps that protected the liquid oxygen feedline bellow were angled and could permit ice build up (above). They have been replaced with a design called a drip-lip that prevents ice build up (below).

Photo courtesy NASA. Photo credit: Lockheed martin/NASA Michoud

Third, five liquid oxygen feedline bellows lie along the umbilicus that connects the liquid oxygen tank with the main engines and are attached to the liquid hydrogen tank. The bellows compensate for expansions and contractions that occur when the liquid hydrogen tank is filled and emptied. The bellows prevent stresses on the feedline. Previously, the foam insulation overlying the bellows was angled. This angle allowed water vapor to condense, run between the foam insulation, and freeze, thereby breaking the foam. To correct this problem, the foam skirt of this joint has been extended over the insulation below and squared off so that water cannot run between the foam.

Preventing Future Space Shuttle Disasters
Explosive bolts separate the SRBs from the external tank when the SRBs burn out in flight. Engineers assessed that fragments of the bolts could also damage the shuttle. They designed a bolt catcher to prevent the bolts from damaging the ET or hitting the orbiter.

Photo courtesy NASA
A bolt catcher (above) was designed to prevent the explosive bolts on the SRBs (below) from damaging the ET or the orbiter.

Photo courtesy NASA

To detect falling debris and possible damage to the shuttle, NASA has done the following:

Photo courtesy NASA
The RMS/OBSS will allow astronauts to inspect the underside and leading edge of the wings for damage.

Finally, engineers and technicians have installed 66 tiny accelerometers and 22 temperature sensors in the leading edge of both wings on the orbiter. The devices will detect the impact of any debris hitting the orbiter's wings.
The entire purpose of the imaging and wing sensors is to detect possible damage from falling debris. Engineers and administrators can analyze these images and make recommendations to the crew during the mission.
NASA also formulated ideas on how to repair damaged shuttles while in flight, including:

These ideas were tested aboard the shuttle Discovery in June 2005.

History of the Space Shuttle
Near the end of the Apollo space program, NASA officials were looking at the future of the American space program. They were using one-shot, disposable rockets. What they needed was a reliable, less expensive rocket, perhaps one that was reusable. The idea of a reusable "space shuttle" that could launch like a rocket but land like an airplane was appealing and would be a great technical achievement.
NASA began design, cost and engineering studies on a space shuttle and many aerospace companies also explored the concepts. In 1972, President Nixon announced that NASA would develop a reusable space shuttle or space transportation system (STS). NASA decided that the shuttle would consist of an orbiter attached to solid rocket boosters and an external fuel tank and awarded the prime contract to Rockwell International.
At that time, spacecraft used ablative heat shields that would burn away as the spacecraft re-entered the Earth's atmosphere. However, to be reusable, a different strategy would have to be used. The designers of the space shuttle came up with an idea to cover the space shuttle with many insulating ceramic tiles that could absorb the heat of re-entry without harming the astronauts.

Photo courtesy NASA
The Enterprise separates from a Boeing 747 to begin one of its flight and landing tests
Remember that the shuttle was to fly like a plane, more like a glider, when it landed. A working orbiter was built to test the aerodynamic design, but not to go into outer space. The orbiter was called the Enterprise after the "Star Trek" starship. The Enterprise flew numerous flight and landing tests, where it was launched from a Boeing 747 and glided to a landing at Edwards Air Force Base in California. EnterpriseEnterprise is now on display at the National Air & Space Museum's Steven F. Udvar-Hazy Center near Dulles International Airport in Washington, DC.
Finally, after many years of construction and testing (i.e. orbiter, main engines, external fuel tank, solid rocket boosters), the shuttle was ready to fly. Four shuttles were made (Columbia, Discovery, Atlantis, Challenger). The first flight was in 1981 with the space shuttle Columbia, piloted by astronauts John Young and Robert Crippen. Columbia performed well and the other shuttles soon made several successful flights.
In 1986, the shuttle Challenger exploded in flight and the entire crew was lost. NASA suspended the shuttle program for several years, while the reasons for the disaster were investigated and corrected. After several years, the space shuttle flew again and a new shuttle, Endeavour, was built to replace Challenger in the shuttle fleet.
In 2003, while re-entering the Earth's atmosphere, the shuttle Columbia broke up over the United States. NASA grounded the space shuttle program after the accident and worked feverishly to make changes and return the shuttles to flight. In 2006, the shuttle Discovery lost foam from its external fuel tank. Once again, the program was grounded and scientists struggled to solve the problem. The Discovery launched twice in 2006, once in July and again in December. According to NASA, the July 2006 launch was the most photographed shuttle mission in history. The Atlantis launched in September 2006, after delays due to weather, a problem with the fuel cell and a faulty sensor reading.

While the space shuttles are a great technological advance, they are limited as to how much payload they can take into orbit. The shuttles are not the heavy lift vehicles like the Saturn V or the Delta rockets. The shuttle cannot go to high altitude orbits or escape the Earth's gravitational field to travel to the Moon or Mars. NASA is currently exploring new concepts for launch vehicles that are capable of going to the Moon and Mars

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