A B O U T
INTRODUCTION TO HYPERSONIC FLIGHT
“Speed has become an important element of strategy."
- Regis McKenna
BEYOND MACH 5
Once you travel past the speed of sound you break the sound barrier and travel ahead of sound. That is called supersonic speed, or MACH speed.
Hypersonic speed occurs when a heavier than air body achieve a velocity superior to MACH 5 or five times the speed which sound travels through the atmosphere.
The speed of sound is roughly 1236 KM/H at sea level and at higher altitudes sound travel slower at about 1000 KM/H.
To simplify things we can say MACH 5 equals to 5000 KM/H.
As demonstrated in water (where sound travels faster) the less dense the envinroment the slower sound will travel. To give you a broader sense: In the vacuum of space sound do not travel at all. Temperature will also be a factor to determine the exact speed required by an aircraft to travel ahead of sound.
Achieving hypersonic speed brings several challenges to the table. One of them: Travelling through air at very high speeds causes a lot of friction. This friction is so high it will melt most known materials, and they will start melting very fast once you blast open your hyperplane throttle all the way.
So is it possible to fly Hypersonic using today´s technology?
Yes! For brief periods of time: MINUTES
Maintaining hypersonic speed is a very complex achievement but as history have shown to us that is not an impossible task. Most rockets like the recent SPACEX models achieve speeds way superior to MACH 5. Even the ICBMs (Intercontinental Ballistic Missiles) made and designed in the 50´s and 60´s can achieve hypersonic speeds at higher altitudes. Reentry capsules also achieve hypersonic speeds.
The Stardust sample-return capsule was the fastest man-made object ever to reenter Earth's atmosphere
(12.4 km/s or 28,000 mph at 135 km altitude).
ICBM test launch.
Hypersonic flight is not a new concept of flight and is nothing new. It was first demonstrated in 1949 at White Sands (New Mexico - USA) when they modified a V2 rocket into a two stage experimental configuration. The X-15 spaceplane also achieved hypersonic speeds for brief periods of time and was conceived to be a future orbital launcher. For a number of reasons the X-15 project was abandoned and the staged rockets we see sending astronauts all the way to space today took place and remain the platform to send humanity and all sorts of experiments to the heavens.
Artistic representation of the X-15 in flight. To this date the X-15 still holds the speed record for a spaceplane. In 1967 pilot Pete Knight reached the record speed of 4,520 mph, or Mach 6.7 (6.7 times the speed of sound). The X-15 was air-launched from the belly of a larger airplane.
A modern era rocket made by SPACEX waiting on the launch-pad.
ICBMs and HYPERSONIC
The Intercontinental Ballistic Missiles (ICBM) are hypersonic as they fly faster than MACH 5.
The point is: They are not very maneuverable at all and they follow a parabolic arc flight trajectory.
The newest missiles are being designed to be highly maneuverable and will fly at lower altitudes with the ability to change their flight path making it very hard for a defense system to track or intercept them.
That means these missiles will be able to fly at very low altitudes and at very high speeds way superior to MACH 5 following unpredictable and erratic trajectories.
How an ICBM designed in the 60´s hit a target.
On the other hand the newly designed hypersonic missiles can fly at lower altitudes and will be able to change their trajectories making detection and interception a very complex problem.
There are two main types of hypersonic missiles being developed by the defense industry:
Hypersonic Glide Vehicle (HGV)
It is a glider warhead set on top of a propulsion system. They are launched on top of the launcher vehicle, reach the edge of space and glide towards a target. They destroy a target using kinetic energy (their own weight + a lot of speed). These designs can be adapted to carry powerful weapons like nuclear devices.
Hypersonic Air-breathing Weapons (HAW)
Hypersonic Cruise Missiles (HCM)
Hypersonic cruise missiles are powered all the way from launch to final approach. They can accelerate and change their trajectories. While hybrid engines have been demonstrated there are two main types of technologies to achieve hypersonic speeds above MACH 15:
These are simplified turbine designs with a lot less or no moving parts at all. They are very complex to be built as the challenges involved are comparable to lighting a match inside a hurricane. Ramjets need a lot of airspeed to start performing: MACH 3
ScRamjets (Supersonic Combustion Ramjet)
Scramjets use a similar approach and need a higher airspeed to function: MACH 6
These engines can reach unknown higher speeds.
MOVING PARTS BREAK WITH HIGH SPEED
Problems Associated with Nuclear Hypersonic Weapons Proliferation
A collaboration between documentary filmmaker Neil Halloran and
Nobel Peace Prize - Research and Information, this short data-driven
film simulates a nuclear blast in a major city in order to tally the estimated deaths that would result. Using data from leading researchers and highlighting present day technology developments,the film illustrates the very real danger nuclear weapons still pose to humanity and life on Earth.
Spaceplanes are a proven technology and the Space Shuttle is our best example. It was a multi-stage vehicle launched to orbit with the ability to re-enter our atmosphere and glide back unpowered, just like a glider, to land over a very long runway. Can you imagine the challenges involved?
The Space Shuttle achieved the hypersonic mark speed of MACH 5 in just 160 seconds after lift off at an altitude of 70.000 Meters where the atmosphere is very thin causing a lot less air induced friction compared to a sea level altitude. In just 500 seconds (8.33 minutes) after lift off the Shuttle was floating in space at altitudes above 100.000 Meters with its speeds exceeding MACH 27. Today several projects and plans for feasible simplified hypersonic spaceplanes and airliners that don´t require a rocket assisted staged lift off like the Shuttle needed, have been proposed and some are under development. NASA and state of the art alike research facilities across the globe along with the private industry demonstrate fantastic plans and prototypes as the technology involved matures. Still, a number of technological problems must be solved and funding is a major entry barrier from individuals to big organizations. These programs cost billions of dollars from a paper concept to a fully functional technology demonstrator.
F U T U R E
Recent developments combined with the technological advancements that are just next door will be highly beneficial for the aerospace industry. We will see aircrafts delivering cargo and transporting passengers at speeds once imagined by science fiction. Further propulsion and dynamics research will lead to the development of lower cost sub-orbital and orbital launchers leaving Terra-Firma with experiments and passengers aboard.
The reduction of flight duration will be extremely important to fight global warming. Along with the newly introduced electric planes we believe "hypersonic" will be the next great step of aviation even being a 70 years old unresolved "new technology".