|
11/21/2000
Mistakes - High Tech, Low Tech
I just looked up the word "chad" in two dictionaries and all I
came up with is Chad, a country in Africa. Indeed, my
spellchecker tells me that I should have capitalized the word.
Yet, the identity of our next president is depending upon the
presence or absence, or on the degree of attachment or
"pregnancy" of chads on pieces of paper. I was amused by the
response of an Irish, or perhaps Scottish tourist in New York
who was interviewed on one of our TV news channels. He said
they don''t have this problem, they just mark their ballots with an
X. What a novel concept! In our precinct we neither punched,
marked an X, nor pulled a lever. We simply touched a screen in
the appropriate places and a green X lit up at that spot. When we
finished touching our choices, we pressed a button and a few
musical notes typical of today''s computer games informed us that
our vote was registered. Of course, living here in New Jersey
only three miles from the birthplace of the transistor, we expect
nothing less than the latest technology.
The failure of Florida to go to a high tech form of voting has
proved to be a mistake. Such technological mistakes may be
crystal clear in hindsight. Sometimes, however, in contrast to the
Florida case, a failure to implement or achieve a high tech goal
or decision can prove to be a good thing, as Martha Stewart
would say. In the past, I''ve mentioned my own peripheral
involvement in an effort targeted at the development of a nuclear
powered airplane. Failure to achieve that objective was certainly
a good thing. Another example of a technological mistake was
the decision by the United States to develop a supersonic
transport, or SST. All of us taxpayers should be grateful that we
failed to do so and were beaten by the British-French Concorde.
To understand these shenanigans, let''s talk a bit about
supersonics, the branch of aerodynamics dealing with the
behavior of objects when their velocity exceeds the speed of
sound. The speed of sound depends on what kind of stuff the
sound waves are passing through. Obviously, here we''re
concerned with airplanes in the atmosphere. Even in air the
speed of sound depends on such things as the temperature, the
humidity and the pressure, which goes down as you go higher in
altitude. Because of this variation, you''ll hear or read about the
so-called Mach number, named after Ernst Mach, an Austrian
physicist and philosopher. The Mach number is simply the speed
of your aircraft or missile in its surrounding atmosphere divided
by the speed of sound in that same atmosphere. At Mach one,
M-1, you''re at the speed of sound. At M-2, you''re going twice
the speed of sound and at M-0.85 it''s 85 percent of the speed of
sound. We''ll come back to M-0.85 shortly.
The performance of a rocket, an airplane or even your car
depends on the pattern of the air flowing around the moving
body. For projectiles and airplanes this airflow has been studied
by ultrahigh speed photography and in wind tunnels. You''ve
probably seen pictures of speeding bullets showed the patterns of
airflow around them. Wind tunnels range in size from huge ones
that can accommodate full size airplanes with wingspans of 70
feet to much smaller tunnels used to study airplane models or jet
engines. While huge fans, propellers or air compressors can
generate wind speeds of hundreds of miles per hour, some wind
tunnels manage wind velocities of up to many thousands of miles
per hour. In some of these wind tunnels, an explosive charge is
used to explode the model aircraft into the tunnel while at the
opposite end another explosion is used to propel the gas (air)
towards the model. This gives effective super high speeds,
which may only last for a second, so you have to be awfully fast
in getting your photos and other measurements!
Such studies on projectiles revealed that up to M-0.85, 85
percent of the speed of sound, the airflow pattern is plain old
turbulence. The study of turbulence in liquids and gases has
occupied many scientists and engineers for centuries. However,
above M-0.85, as you approach the speed of sound, shock waves
begin to appear. These shock waves form at breaks in the
smooth shape of the projectile or aircraft; hence the quest for a
streamlined shape. However, at M-1, the speed of sound, shock
waves form at the nose and tail and that''s when you hear and feel
that unsettling sonic boom if you''re on the ground.
How does this affect the shape of your aircraft? If you want to
fly at typical speeds less than the speed of sound, as in your
jumbo jet, the ideal shape is like a teardrop. However, when you
get in the shock wave range the large front surface of your jumbo
has to compress a lot of air to generate the shock waves. The
larger the surface the more energy you lose and the bigger the
shock wave. Now you know the reason for the needle-nose
shape of the Concorde - you want to minimize the surface up
front. But there''s another point of concern. The shape of the
shock wave depends on the speed. It propagates in the shape of a
cone and the faster you go the sharper the cone. This is why you
see the really fast planes with their wings swept back so sharply.
It''s to avoid the shock waves from the nose of the plane.
Now back to the story about the American mistake that has saved
us taxpayers huge sums of money. Coincidentally, the impetus
for this column is an article in November''s American Heritage by
John Steele Gordon, whose article in another issue of that
magazine provided material for last week''s column on Edison
and the electric chair. I suspect Gordon''s article may have been
prompted by this year''s crash of the French Concorde near Paris.
The idea for a supersonic transport was in full bloom in the years
after the Boeing 707 began flying across the Atlantic in about 7
hours. Many people assumed that, since there were already
fighter planes flying at supersonic speeds, the next logical step
was to build a passenger-carrying SST. In the 1960s, the British
had been researching this possibility and wanted the U.S. to join
in and share the expense. But America didn''t want to play
second banana and decided to cede the first shot to the British.
The plan was to then leapfrog over them with a more impressive
aircraft. Meanwhile, Boeing began work on the 747. Not to be
denied, Britain signed an agreement in 1962 with France to
jointly build an SST, the Concord, later to become the Concorde.
In 1963, President Kennedy committed the U.S. to building an
SST. Earlier, he had committed to a moon landing and the
Apollo program. It is ironic that the latter, much more ambitious
project was the one that succeeded. At any rate, by 1966 and the
funding of some $400 million, the government had chosen
Boeing and Lockheed to compete by coming up with individual
SST designs. Remember that the designs for good performance
at subsonic and supersonic speeds are fundamentally different.
The Boeing approach was a design that was supposed to allow
good performance at both subsonic and supersonic speeds. This
was to be accomplished by a swing-wing design that would
allow the plane to change the shape of the wing in flight and thus
alleviate the sonic boom problem as well as allow the use of
more airports. Lockheed, on the other hand, stuck to a more
conservative approach with a design much like the Concorde''s
fixed-wing, which is good for supersonic but lousy for subsonic
flight. Lockheed''s plane would have been much larger than the
Concorde. The U.S. government, in the form of the Federal
Aviation Administration supported by "competent Government
evaluation", chose Boeing. This decision, made on New Year''s
Eve of 1966, was thankfully a big mistake!
After nearly two years, it was clear that the swing-wing was not
feasible for any significant passenger load and Boeing switched
to the delta-wing design of the Concorde. By this time it
appeared that the U.S. was about 6 years behind the British-
French combo and various airlines had options on 74 Concordes.
Another obstacle to a U.S. SST was evolving, namely, the
environmental movement, which was beginning to decry the
sonic boom problem and the SST''s huge fuel consumption. In
1970, the 747 was flying some 400 or more passengers over the
Atlantic with a fuel consumption that was less than would be
required by the forthcoming Concorde, with only a hundred
passengers. Furthermore, the 747 was making a profit!
In March of 1971, both the House and Senate voted to kill the
SST program by margins of only 11 and 5 votes, respectively.
There were predictions by critics, including Barry Goldwater,
that this action would doom the U.S. lead as an airframe
manufacturer. But, as the environmentalists made their point
regarding the sonic boom it became clear that the SST would
only be flying over the oceans. Consequently, all but the British
and French dropped out of the SST game. It was the jumbo jets
and the "interim" 747 that took the brass ring. And Britain and
France, who built only 16 Concordes, were left to swallow the
billions of pounds and francs of development costs.
History repeats. Not too many years ago, there was another SST
initiative and the press was full of accounts about the possibility
of flying from New York to Tokyo in a few hours. The U.S.
government funded a program called the High Speed Civil
Transport program. I searched "High Speed Civil Transport" on
the Web and came up with a slew of sites, mostly NASA sites,
dealing with various aspects of the program. According to
Gordon''s article, Boeing has now dropped the project. The
reason? The article quotes a Boeing official, "You and I couldn''t
afford to fly in the darn things." Another good thing.
Heck, I can''t afford to fly the Concorde, let alone a HSCT!
Allen F. Bortrum
|
