Nearly everyone on planet Earth has heard of the organization called NASA.  They may not know that NASA stands for National Aeronautics and Space Administration, but they do know that it runs the world’s most successful space program.  Though founded in 1958, NASA was immortalized in 1969, when it sent a man to the surface of the moon.  The event was the landmark of the twentieth century, and cemented the United States as the world leader in space exploration. 

The economic benefits that the United States reaped from its lunar landing cannot be overstated.  Leaders in aerospace are leaders in technology, and leaders in technology are economic superpowers.  If the American energy and auto industries matched the level of excellence of NASA, the United States would be technologically untouchable.

I would bet that the vast majority of Canadians haven’t a clue what CSA is.  The Canadian Space Agency is the Canadian equivalent of NASA, but the two organizations are hardly equivalent.  CSA is a fine organization.  They participate in the expensive practice of space exploration on a meagre budget; it is however the level of funding of national space organizations that determines the extent to which they may participate.

Here is an order of magnitude scale for the kind of aerospace related activity you can afford for a given amount of American dollars in 2011:

$100,000,000,000                 Manned interplanetary mission

$10,000,000,000                   Manned lunar mission

$1,000,000,000                     Unmanned rocket for satellite placement

$100,000,000                        Complete communications satellite or a 747 airplane

$10,000,000                         Space payload (eg, Satellite Antenna)

$1,000,000                           Basic helicopter

$100,000                              Half a tank of gas for a 747 airplane

$10,000                               One foot wide meteorite (collector’s item)

$1,000                                 Typical coach plane ticket with return

$100                                    Nike sneakers to jump as high as you can

$10                                      Movie ticket for Apollo 13

$1                                        Paper airplane

The table above shows that you need a factor of ten in terms of dollars to take an aerospace project to the next level.  Ten million buys the payload... Add a factor of ten for the satellite to mount it on... Add a factor of ten for something to launch the satellite with.  To merely participate in a project outside the atmosphere, the kind of budget required is ten million dollars.  This is why many nations stay out of the space game entirely.

   

NASA has an annual budget of 18.7 billion dollars.  This money comes from the roughly 300,000,000 US tax-payers, to the tune of about sixty dollars per tax-payer.  This level of funding allows the organization to explore space independently via unmanned probes.

CSA has an annual budget of about 300 million dollars.  Each of Canada’s 30,000,000 tax-payers contributes about ten bucks towards their nation’s space exploration effort.

The six-to-one US to Canada tax-payer contribution ratio used to be ten-to-one.  The gap has closed in recent years, not because Canadians pay more, but because Americans now pay less.  Still, with ten times the population and six times the per-person funding, NASA’s budget is sixty times greater than that of CSA.

With an operating budget of 300M, CSA can build payloads independently (Canadarm and Dextre, feeds and reflectors), and on occasion, with the help of private industries like MDA, build complete satellites (Radarsat-1 and Radarsat-2).  CSA also conducts research, both at its home base in St. Hubert, Quebec, and on the International Space Station, thanks to its accomplished crew of astronauts.

Still, with funding of this magnitude, Canada will never be able to launch anything into space independently.  And, maybe that’s OK.  By removing themselves from the propulsion side of space exploration, Canada has become a world leader in space payloads by developing its prowess in both robotics and antenna engineering.  CSA can be commended for doing a lot with not very much.

The classic argument against funding space agencies is that there are so many current problems that this money could help to solve here on Earth.  If we are forward-looking enough, we will realize that money invested in aerospace will usually pay for itself in spinoff technologies.  Other organizations like ESA (European Space Agency), JAXA (Japan Aerospace Exploration Agency), and ROSCOSMOS (Russian Federal Space Agency) continue to fund their space presence on the world stage for this very reason.

The accomplishments of a nationally funded space program should be saluted by the tax-payers that contribute to it.  As a Canadian, I have pride that my country has done so much with so little.  I hope that the level of funding for CSA will be maintained, and perhaps even increased over the years.  The boomer generation of kids were inspired by the lunar landing.  If space funding dwindles, this generation of kids will have to settle for paper airplanes.  

The expression “sound barrier” refers to the speed of sound in a given medium.  In the field of aerospace, which studies motion through air and space, the medium in question is air.  Space is a vacuum, which is no medium at all.  Sound can only travel if there is a medium to carry its information from one neighbouring molecule to the next.  As such, sound does not travel outside our atmosphere, contrary to what silly movies like “Armageddon” would lead one to believe.

What is the speed of sound in air?  It is dependent on two factors associated with the air itself: its density and its bulk elasticity.  For standard atmospheric conditions, the speed of sound in air is about 340 m/s.

When an object travels through the air below this speed, its motion is said to be subsonic.  The term Mach number (M) refers to the ratio of a vehicle’s speed to the speed of sound of the medium it travels through.  A typical commercial airplane may travel around 170 m/s, or M = 0.5.  Jets travelling beyond 340 m/s are supersonic.  When an aeronautical engineer hears about Mach 4, he or she thinks of supersonic air travel, and not a Gillette razor. 

When a meteorite hits our atmosphere, it is travelling at supersonic speed.  So, supersonic flight predates man.  However, a fun piece of trivia is to determine man’s first creation that broke the sound barrier?  You do not need to look to the skies for the answer.  Just think, “Indiana Jones”.

Indeed, the bullwhip represents man’s first foray into supersonic speeds.  Due to the chain reaction involved in the mechanics of snapping a whip, the very tip of it will travel at speeds in excess of 340 m/s.  When an object accelerates from subsonic to supersonic speed, the achievement is accompanied by what is known as a sonic boom.  Invariably, the loud snapping noise of the whip is due to this phenomenon.  As it turns out, the speed of sound is no barrier at all; it is, however, a very critical speed.

The moment that an object transitions from subsonic to supersonic speed, the governing aerodynamic principles that affect it alter drastically.  The result of supersonic travel is that the object arrives without warning.  We are accustomed to receiving the sound of an oncoming vehicle before it arrives.  A car’s noisy engine serves as a useful warning for a pedestrian walking on a narrow the street.  As it turns out, the oncoming air that a supersonic jet whooshes through appreciates the advanced warning as well.

For subsonic flight, the air molecules that the airplane displaces have time to prepare for the displacement.  They organize themselves because the sound of the oncoming plane conveyed the following information: “Get out of my way!”

In supersonic flight, the plane is travelling faster than the sound it emits, so air has no time to prepare for the disruption.  The airfoil of the air molecules no longer forms an organized parade around the wing.  Instead, the parade seems to have been organized by drunken molecules (imagine if the St. Patrick’s Day parade took place in the evening instead of the morning...).  The effect of supersonic flow is that a shock wave is emitted through the air; shock is an appropriate term, because the air never saw it coming.

The cone-like shape that forms around an in-flight jet is due to the Mach angle of the jet.  The cone border divides the section of air that received sound wave warning from the jet from the section of air that had no idea it was coming.  So, jets travelling at Mach 4 create much steeper cones than do those travelling at Mach 2.  This angle determines the direction in which the shock wave will travel, and is the reason why a jet passes over your head quietly, but sends a sonic boom once it is a fair distance away (as if to say, “I was here.”).

As the medium of air behaves completely different for M < 1 than for M > 1, the wing design for subsonic planes and supersonic jets is quite different.  The rounded edges of a commercial airliner’s cross-section of wing complement the rounded path of the organized air molecules.  A supersonic jet’s wings will have a sharp diamond-like cross-section to optimize the pressure gradients that manifest around them.

When it comes to aerospace, flying through space is completely different than flying through air.  Whether moving slower or faster than sound, the air allows the plane to generate lift, but also deters its motion with drag.  A rocket may require vast amounts of energy to reach an Earth orbit, but once there, they require no fuel to maintain that high velocity.

To see some beautiful shock waves from jets, and even a rocket ship leaving the atmosphere, click on this link (and make sure to watch it to the end, as the rocket creates a truly astonishing sight).  Hopefully with this very introductory information in supersonic flight, the shock waves that you see will come to you as less of a shock.

To kick off “Aerospace Month” on the Engineer’s Pulse, let us first examine what the term aerospace refers to.  As the word indicates, aerospace studies the motion of objects through both air (in the Earth’s atmosphere) and space (outside the Earth’s atmosphere). 

The field of study can therefore be broken down into two principal areas: aeronautical (within the atmosphere) and astronautical (within space).  Examples of aeronautical navigation include aircrafts (aviation), helicopters, and even hot-air balloons.  Astronautical navigation is limited to spacecrafts and satellites.

There is no real line in the sand, where the atmosphere becomes space; there is just a very gradual transition between the two extreme states.  Near the surface of the Earth, the medium known as air is a reasonably dense gas, with roughly 1 atm of pressure (101.3 kPa); this figure depicts how tight the molecules of the matter are packed together.  In space, at about 300 km altitude, we begin to see the other extreme, where molecules like Oxygen may travel a kilometre before colliding with another molecule.

Although the altitude up until 10,000 km is considered to be the atmospheric domain, 300 km is a convenient line in the sand.  It is where the pressure may be approximated as zero, and the flight dynamics are astronautical in essence.  300 km also happens to be the altitude at which the International Space Station (ISS) orbits the Earth.

Some perspective with regards to the scale of altitude is helpful to appreciate aerospace.  A commercial pilot will often announce a cruising altitude of about 30,000 ft, which translates to about 10 km.  This is a typical distance from the Earth’s surface where aeronautical navigation takes place.  The 300 km altitude mentioned previously is in the region of LEO (low Earth orbit).  Even this altitude is a stone throw away from the Earth in a relative sense, given that the radius of the Earth is about 6,378 km.  Cities on Earth that we consider nearby are usually more than 300 km apart.

The difference between travelling in air and space is immense.  A bird flying and a fish swimming have more in common than do a rocket and an airplane.  Airplanes, birds, and fish, make use of the fluid around them to propel themselves, whether that fluid be a gas or liquid.  Although spacecrafts must first travel through the atmosphere to reach space, they are designed for navigation once they reach space – a place with no surrounding matter to make use of.

From a Newtonian physics point of view, aeronautical ships have four forces acting on them.  The first three involve the air: the thrust force from the engines, the drag force opposing the thrust force (due to wind resistance), and the lift force on the wings due to air pressure gradients.  The final force acting on an airplane is the gravitational one.  When a rocket or satellite travels through space (outside the atmosphere), the gravitational force is the only force acting on it for the majority of the time.  It is the high velocity and gravitational force that cause satellites to orbit the Earth – to gravitate around it.

On occasion, when a rocket is in orbit, it may want to alter its course.  If its engines worked like those of an airplane, it would be unable to move.  Whereas an airplane propeller intakes and outputs the air around it for propulsion, a rocket must carry its fluid (gasoline) with it.  A spacecraft engine makes use of Newton’s third law: it exhausts the fuel that the rocket carries at extremely high velocities (opposite to the direction in which it wants to move) to impart an impulse on the entire rocket.  If a rocket orbiting out in space were to run out of fuel, it would be stranded.  With virtually no surrounding fluid to impose a drag force on it, it would continue to orbit indefinitely.

The field of aerospace is one of man’s most exciting realms of research and development.  Our species, always fascinated by the world around us, saw the birds that navigate the air around them with ease as a direct challenge.  However, we had to wait until the early twentieth century to participate in the fun.  On December 17, 1903, the Wright brothers performed the first powered, controlled flight. 

Aviation has seen a multitude of advances since that historic flight over a Century ago.  The sheer quantity of people transported via commercial aircraft today is astonishing.  It is estimated that in the year 2014, the number of man flights will reach 1.26 billion (3.5 million man-flights per day). 

From a technological standpoint, the principal goal continues to be to make lighter airplanes for increased energy efficiency.  Material advances ensure continuous improvement in this area.

While aeronautical travel is interesting, astronautical travel is where the excitement of aerospace resides.  Nothing captivates the human spirit more than the exploration of faraway lands.  Indeed, the 1969 lunar landing remains a benchmark in human history – possibly man’s crowning achievement to date.

Despite the allure of interplanetary missions and other aerospace research endeavours, many believe that we should focus our resources on more immediate issues that exist on the surface of the Earth, such as poverty, hunger and disease.  I believe there is a careful balance to be found here.

Economies that do not advance technologically stagnate, and no area (short of military applications) creates as many spinoff technologies as does aerospace.  Materials that are developed for aerospace are later employed by other industries.  For example, composite materials, which continue to be developed for aircraft use, are later used for hockey sticks.  Velcro was originally developed for astronautical applications, but today, it allows little Jimmy to do up his shoes. 

International poverty must be addressed, but only economically healthy countries can afford to send aid.  Economic health may only be found on the borders of cutting edge technology, and this is where aerospace lives.

Still, the most compelling reason to take to higher altitudes remains the human spirit.  We are still in awe by the birds.  Today, we see the endless cosmos as a challenge, and wish to explore it.  A major advancement in astronautical travel will be necessary if we are to truly address this challenge.  This advancement will be the topic of my next article.