The Physics of Stealth
The Blackbird is considered as a strategic reconnaissance aircraft, this is simply an fancy name for a spy plane and to be one the aircraft must be able to
mask its presence be it visual or through sound and against technology such as radar.                                        photo from http://www.globalsecurity.org/intell/systems/sr-71-pics.htm

The Sr-71 easily fulfills all the requirements needed in order for it to be concealed from the enemies as shown by its stellar record during its deployment in the field. In terms of speed, the Blackbird reached maximum velocities of Mach 3.3 or about 2,200 mph.  It also cruised at about 80,000 ft above ground so there is typically no way of seeing the aircraft with just the naked eye. The most important however is its ability to hide from radar.
 
 Radar Stealth:                                                                                                                                       
In order to understand how to hide from it, one must know how radars work in the first place. A radar is a tool which is used to  find the location of an object in a certain area. This is done by using the fact that radio signals bounce off of metal surface which is a major component in most aircrafts. To make an aircraft more aerodynamic, engineer create them with a specific shape that reflects radio signals in all direction. This of course includes the direction back to the radar which then pinpoints the location of the aircraft. With this in mind, the designers of stealth aircrafts created a more flat shape for their planes in order to reflect radio signals in other directions thanthe radar thus inducing a sort of invisibility.

Lastly, aside from being able to hide from radar an aircraft must also be able to hide its heat signature. This can be problematic as going as fast as the SR-71 can produce lots of heat due to friction. The next page will explain how the Blackbird manages to keep itself from overheating even when speeding at Mach 3.3.