01. What are the landing procedures? (A K2S Question)
From The Space Library
The preparation for landing begins the day before deorbit. That day is filled with storage of all the equipment, experiments and clothing that have been used during the mission. On that day we check and recheck most of the systems that we will depend on to ensure a safe re-entry and landing. Some systems—for example the landing gear— can't be checked and we just hope that there have been no failures. The day also offers an opportunity to reflect on what we have seen, what we have accomplished, and the significance of what we have done and how those successes will influence the knowledge for the next generation. It is also the time that we talk about the funny things that have happened and those experiences that will always be remembered by the crew. The morning of launch is filled with excitement. There is continuous conversation with Mission Control about the predicted weather at the landing site, and a review of the deorbit and landing procedures. Several hours before deorbit, the crew changes into their launch and entry suits, and begins to rehydrate using a water and salt solution. We spend some time reconfiguring the software from on orbit support to re-entry, and verify that the computers are ready and that there are no funny things that could cause a problem. The crew has practiced each of these procedures and recovery from possible failures during training. There is nothing more to do until the commander initiates the deorbit command. Soon after the button has been pushed, the orbital maneuvering rockets fire to slow the orbiter down, beginning the descent from space into the atmosphere. The deorbit maneuvering is automated, giving the crew the opportunity to look down and watch the world rush up toward them. Sounds scary, but it isn't at all. The re-entry to landing takes about one hour, and half of that time is spent above the atmosphere, still at orbit speed of approximately 17,500 miles per hour (mph) and still at approximately zero-gravity. When the orbiter encounters the atmosphere, there is an onset of gforces and a beginning of the slowing process resulting from the friction. The crew begins to feel heavy and the outside temperature of the orbiter approaches 2,500° F; inside, however, the crew is quite comfortable with the temperature about 70° F. The orbiter banks from side to side to lose energy, and, combined with the increased atmospheric friction, decelerates to landing speed of approximately 190 mph and maneuvers into alignment with the landing runway. As the orbiter decelerates below Mach 1, or the speed of sound, the commander takes control and flies manually to touch down. During this entire series of events, there is absolutely no propulsive power. The orbiter is just a glider, so there is only one opportunity to land, and therefore it has to be extremely accurate. The space team has so fully prepared that most observers think it is risk free. Not the case at all! Re-entry, just as ascent and on-orbit operations, is extremely dangerous, but the risk is mitigated by training, reliable systems, an emphasis on safety, and an attitude of success. After touchdown, the orbiter is guided to a stop by the commander. At this time, with coordination with Mission Control, the orbiter is powered down and the crew awaits the opportunity to exit the vehicle and stand on Earth again.
Answer provided by Col. USAF (Ret.) Frederick D. Gregory
Question and Answer extracted from the book Kids to Space - by Lonnie Schorer
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