What is a supersonic missile?
What’s a supersonic missile? Well the short answer is a really fast missile. The prefix “super-” comes from Latin origins meaning that “above”, “beyond”, or “above” in relation to the root word. In this case the root word is “sonic” which refers to the sound. Therefore, supersonic means beyond [the speed of] sound. How fast is that, exactly? This is going to get into a bit of physics which uses the metric system for all of its calculations. First of all, there are a number of things that can affect sound. Let’s clarify what sound is first. Scientifically speaking, in a nutshell, sound is vibrations or waves traveling through something that are picked up by your ear and interpreted into something that makes sense. The medium that sounds waves travel through will affect its speed, for example, sound travels faster through water because the molecules are more densely concentrated whereas sound will travel more slowly in a gas like helium which is lighter than our regular atmospheric air at sea level. So let’s conceptualize this into an informal rule of thumb for medium: the less it floats, the less delay there is in sound traveling through it. In other words, the faster it sinks in water, the faster sound will travel through it. So now that we’ve addressed some of the wildcards, let’s move on to the textbook examples that are used as the standard in a controlled environment. When the temperature is 0C (23 degrees Fahrenheit), at Sea level (0 elevation) sound travels at 331.4 meters per second (about 362 yards per second) so a supersonic missile travels at speeds greater than this. In terms of miles per hour, that’s 742.336 mph. Keep in mind that any missile will be traveling through various altitudes and various temperatures which will affect how fast it actually travels at any given time from its launch point to its target so in a case like this, the figure above would not be entirely accurate but would be used as a standard to estimate what’s known as time on target or time to impact. Here’s a site that lets visitors calculate the speed of sound through various mediums at different temperatures. http://hyperphysics.phy-astr.gsu.edu/hbase/sound/souspe.html Once this supersonic missile reaches the speed of sound, it’s at the threshold of what’s called the sound barrier. For aircraft this is called “mach 1” which is one time the speed of sound. Many fighter aircraft can actually go this fast. So after all that, a supersonic missile is able to travel at speeds greater than 742.336 mph.
A supersonic missile is technically any missile that travels faster than Mach 1, as a number of cruise missiles do. However, sometimes the term is specifically used to refer to the next-generation, faster missiles with speeds of Mach 2 to Mach 3. These missiles, which include the Indian-Russian BrahMos, the Russian Moskit (Mosquito), and the American Coyote, are popular for anti-ship warfare plans, because their great speed would only allow a theoretical response time of 20-30 seconds, as opposed to the 120-150 second response time permitted by subsonic missiles like the American Tomahawk or French Exocet. Supersonic missiles use ramjet engines, 4X for the Moskit and Coyote and 2X for the BrahMos. Using ramjets for propulsion, these supersonic missiles are also known as air-breathing missiles. Ramjets use rapidly inflowing air to oxidize rocket fuel, obviating the need for an on-board oxidizer, allowing a greater weight-payload ratio and increasing top speed. They also lack moving part
