Helping Aubie this week is Dr. Roy Hartfield, a professor in Aerospace Engineering at AU

Dear Michael,

Artificial or manmade satellites are launched into orbit about the earth as payloads mounted on either solid or liquid rocket powered launch vehicles. The best known current launch vehicle is the United States Space Shuttle. For Space Shuttle launches of satellites, the satellite is placed in the payload bay of the Space Shuttle Orbiter for safe travel during launch. During launch, the Orbiter is powered into orbit by two large solid rocket motor powered boosters and three main liquid rocket engines. The fuel for the liquid rocket engines is carried in the external tank. The space shuttle is now mostly dedicated to launching the remaining pieces of the largest artifical satellite ever to be placed in orbit, the international space station, and is no longer used to launch commercial satellites. Other well known commercial launch systems are the Boeing Delta series of rockets, originally derived from the a 1950’s era missile program known as Thor, and the French Ariane launch vehicle originally developed in the 1970’s.

The height to which satellites are launched depends largely on the function of the satellite. In most cases it is desirable for the satellites to remain in orbit for extended periods of time with little boosting from rocket motors. The minimum altitude at which this can occur is about 200 miles. This is referred to as low earth orbit. At altitudes below this, the orbits tend to decay at significant rates due to atmospheric drag. The International Space Station and the space shuttle orbit at approximately this altitude. For satellites which perform communications functions, a highly desirable orbit altitude is just over 20,000 miles above the surface of the earth. At this altitude, satellites orbit the earth with a period of 24 hours which means that they sometimes appear to be stationary in the sky from an earth-based observer. This orbit is referred to as a geosynchronous orbit. Satellites which are designed for weather forecasting, imaging of the surface of the earth, navigation, deep space imaging and other functions are placed in a variety of orbits, usually between low earth orbit and geosynchronous orbit. Some of these satellites are in non-circular or elliptical orbits meaning that they spend part of their time relatively near the surface of the earth and part of their time relatively far from the surface.

Thanks for your question!

Aubie and Dr. Hartfield