|
|
Multidisciplinary
Design, Analysis, and
Optimization Branch
|
|
|
| |
EDUCATIONAL ACTIVITIES: THE BEST OF THE NASA AEROQUIZ
|
|
|
| |
|
| |
Week of 1/13/97:
Q:
When a commercial airliner is cruising at 35,000 feet, the temperature of
the air outside the aircraft is around minus 66 degrees Fahrenheit. However,
instead of heaters, air conditioners must be used to provide comfort for the
passengers and crew. Why?
A:
The pressure of the air at 35,000 feet is too low to breathe.
The fuselages of commercial airliners are pressurized to comfortable
levels using "bleed" air extracted from the engines' compressors. The
compression stage of the jet cycle raises the air to high temperatures, so air
conditioners must be used to cool the cabin air.
Congratulations to Bill Baumgarten.
Week of 1/20/97:
Q:
What was the first sonic boom created by humans? Was it when Chuck
Yeager broke the sound barrier in the Bell X-1? Or had people created sonic
booms before that?
A:
The first sonic booms attributed to humans were created
by very early supervisors (homo-sapien-bossius), who
developed the ability to "crack" a whip (much to the
dismay of workers (homo-sapien-dilbertius)).
Congratulations to Paul Giel.
Week of 3/31/97:
Q:
"Let's see now," the FAA aircraft certification engineer said to
himself. "95.4, 101.1, 97.8... add those together... Got it! 103.5!"
Is the engineer right? Or can't the FAA get good help these days?
A:
The certification engineer
is correct if he is adding sound levels in decibels!
Congratulations to Arnie McCullers.
Week of 6/2/97:
Q:
The White Knuckle Air Cargo Service has issued a request for proposals for
a new cargo aircraft. Here's an excerpt from the mission requirements
section: "...The aircraft shall have a cruising speed of not less than
Mach 0.7, shall be able to carry a payload of not less than ten thousand
pounds, and shall have a design range of not less than fifteen thousand
miles...." Is there anything wrong with any of these requirements?
A:
One half of the mean Earth circumference is 12450 statute miles.
Ignoring "no-fly zone" political issues, there's no reason
to build a cargo aircraft with a design range of fifteen thousand miles.
Congratulations to Arnie McCullers.
One more problem: the requirements also do not specify the use of Arnie's
Flight Optimization System aircraft analysis code!
- The Aeroquiz Editor.
Week of 6/30/97:
Q:
When rising to the surface, a major concern of deep sea divers is
contracting the bends.
Do pilots ever need to be concerned with getting the bends?
A:
Yes, Ask any ex-SR-71 pilot who may be around the office.
They needed to go through a process of N2 purging
prior to a mission. The "bends" is a direct result of
the reduction of external atmospheric pressure resulting in
nitrogen bubbles forming in the bloodstream.
Congratulations to Greg Engel.
Not only are the formation of nitrogen bubbles in a pilot's blood
a concern, but it isn't even the worst-case possibility. At very high
altitudes, the atmospheric pressure is so low that, without protection,
many liquids can boil at body temperature.
Pilots of the high-altitude U-2 spy plane, for example, wore the
MC-3 pressure suit, which has many of the properties of a spacesuit.
- The Aeroquiz Editor.
Week of 8/11/97:
Q:
The very first wartime air-to-air combat victory, interestingly enough,
did not involve the use of guns. What happened?
A:
Bombs were used.
Congratulations to Joe Wickenheiser.
On June 7, 1915, Royal Air Force pilot Reggie Warneford was flying a
Morane Parasol with no guns of any kind. He did, however, have six 20-pound
bombs, which he dropped on top of the hydrogen-filled German L.37 Zeppelin
dirigible over Ghent. The Zeppelin's helmsman jumped from the burning wreckage at
about two hundred feet, crashed through the roof of a convent, and landed in
an unoccupied bed, suffering only minor injuries. He was said to have opened
a beer hall after the war, where for years he told of his adventure.
- The Aeroquiz Editor
Week of 12/1/97:
Q:
During high-speed maneuvers in modern fighter aircraft, pilots can
experience centrifugal forces equivalent to many times the force of gravity.
When this happens, blood can pool in the body's lower extremities, and the
pilot is susceptable to blacking out. A G-suit counters much of this problem by
squeezing the pilot with expandable bladders to keep more blood in the upper
body. The U.S. Navy's Blue Angels pilots, however, choose not to wear them.
Why?
A:
Two reasons:
1. They don't make the g-suits in the color blue that the
Blue Angels wear (just OD green).
2. They have a strict workout regimen to increase their g-tolerance --
most of their shows do not have sustained g's in
excess of 5 g's, although there are some maneuvers with
instantaneous g-loadings of 8 or more.
Congratulations to Michael L. Jensen.
The suits are restricting and uncomfortable, preventing the Angels pilots
from performing precision flying. Instead, as Michael said, they keep in
excellent shape with rigorous training. When gee forces hit, they squeeze
their abdominal muscles for all they're worth.
- The Aeroquiz Editor.
Week of 1/5/98:
Q:
You are a passenger in a commercial jet cruising at 35,000 feet. Unknown
to you, an extremely unlikely event has occurred inside the main exit door --
the cleverly redundant latching mechanism has just failed completely. You
are on your way to the lavatory, but you confuse the restroom door with the
main exit door. You give the big handle a hard pull before the screaming
flight attendant can stop you. What happens?
A:
Nothing. The air pressure will keep the door shut no matter how hard you
push/pull. Part of the redundant system built into the door (i.e "plug").
Congratulations to Anthony Lee.
For safety reasons in a pressurized passenger plane, the doors
are designed to act as "plugs" in tapered door openings.
To open such a door (generally speaking; there are several designs),
they are pulled in first, then maneuvered out through the opening or
are rolled up on overhead tracks.
- The Aeroquiz Editor
Week of 1/19/98:
Q:
You are flying an airplane with a more or less conventional jet engine
through Jupiter's atmosphere. Do you need any fuel?
A:
Yes, you might need oxygen.
Congratulations to Bill Curtis.
A matter of semantics! Jupiter's atmosphere is rich in hydrogen, which
would be a ready-made "fuel" for your engine. On the other hand, you'd need
to carry an oxidizer, such as liquid oxygen.
- The Aeroquiz Editor
Week of 4/6/98:
Q:
Which is taller: A Saturn V rocket filled with fuel and oxidizer, or
an empty Saturn V?
A:
An empty Saturn V. The super cold fuel shrinks the metal of the
rocket, thus its overall height.
Congratulations to Anthony Lee.
The Saturn V used cryogenic liquid hydrogen fuel in its two upper
stages and cryogenic liquid oxygen as an oxidizer in all three of its stages.
The cold shrunk the overall height of the moon rocket by ten inches.
- The Aeroquiz Editor.
Week of 6/1/98:
Q:
When it comes to the excitement of speed, loops, and high-gee barrel
rolls, few things can match the thrill of flying in a high-performance
airplane. But Charles Lindbergh, who was no stranger to daredevil flying,
once remarked, "The thrill of [this] beats the thrill of flying." He was
talking about something that gave thrills that were somewhat similar to flying.
What was it?
A:
I think the answer to the question is "a roller coaster."
That is what is close to the thrill of flying.
Congratulations to "Stephen."
Lindbergh was talking about the Coney Island Cyclone. Built in 1927, it set
the standard for classic wooden-rail roller coasters. There are other
cues taken from aeronautics in roller coaster design: energy management,
extensive "pre-flight" checkouts, and many coaster trajectories
imitate classic barnstorming maneuvers.
- The Aeroquiz Editor.
Week of 7/6/98:
Q:
Why is a modern aircraft fuselage like a Gothic cathedral?
Yes, the famous European Gothic cathedrals with vaulted stone ceilings
and flying buttresses!
A:
They are both examples of stiffened, thin-shelled structures. In most
modern aircraft fuselages, internal "stringers" and other stiffeners deal
with longitudinal loads, while the skin supplies the necessary torsional
stiffness. In a Gothic cathedral, the relatively thin stone walls are
the structure's "skin." The major load in a cathedral is a lateral thrust
produced by the weight of the vaulted stone ceiling. That load is dealt
with by structural stiffeners: the elegant flying buttresses. Unlike
today's aircraft structures, the 12th and 13th century cathedrals were
designed and built without the aid of modern mathematical analysis -- a
truly remarkable engineering feat.
No one got the correct answer!
- The Aeroquiz Editor
Week of 8/3/98:
Q:
Near the end of his Apollo 14 moon walk, Al Shepard attached a 6-iron
club to the end of a sample collecting tool, hit two golf balls, and became
the first person to golf on the moon. Although his bulky space suit forced
him to take awkward, one-handed swings, he joked that the second ball
traveled "miles and miles." If he wasn't encumbered by a suit and was able
to get "good wood" on the ball, could he have taken advantage of the
moon's low gravity and no atmosphere and put the ball into orbit?
Assume he could hit it tangentially to the horizon, avoid mountains, put
it into a circular crater-top level orbit, and achieve a record-setting
250 foot-per-second club speed!
A:
Nah, the circular orbital velocity at the moon's surface is 5517 ft/s, so a
250 ft/s whap falls far short. I wonder if they will try to locate
Al Shepard's (NASA's?) golf balls someday! After all, what would an
alien think if it found one?! (What would they think it was?)
Congratulations to Bill Strack.
Week of 8/10/98:
Q:
What do fireworks, smoke bombs, falconry, border collies, mouse traps,
radio-controlled airplanes, sharpshooters, and propane-fueled noisemaking
cannons have to do with airport operations?
A:
They are all methods to scare away birds
from runways to prevent potentially catastrophic
bird ingestion into engines.
Congratulations to Dan Shedd.
With 11,571 bird-aircraft collisions reported to the FAA
between 1992 and 1996 (with a reporting rate estimated at only 20%), airport
birds represent no small problem. The mouse traps, by the way, are set for
mice and voles that chew the wiring of runway lights and attract birds of prey.
- The Aeroquiz Editor
Week of 9/14/98:
Q:
In many events, track and field athletes can take advantage of low aerodynamic
drag. The reduced drag that occurs on hot days and high altitudes, for example,
has been attributed to helping U.S. athlete Bob Beamon break, in Mexico City
in 1968, what was then the world long jump record by almost two feet.
Would an airplane also experience better performance trying to take off from
a high altitude field on a hot day?
A:
No. The high altitude would translate into a longer takeoff run due to the
thinner air. In addition, a turbine engine prefers cool, dense air.
Shortest takeoff runs occur at low, cool altitudes.
Congratulations to Anthony Lee.
Although drag is indeed less on a hot day at high altitude, so is lift!
Jet engine thrust also suffers substantially. The low-density air results in a
reduced flow rate through the engine. So, thanks to Newton, we know the
force of thrust is penalized. The nozzles also have less enthalpy difference
to work with, and, for you thermodynamic cycle analysis fans out there,
the engine's integral of TdS is smaller!
- The Aeroquiz Editor
Week of 11/2/98:
Q:
In 1922, fantasy author Edgar Rice Burroughs wrote At the Earth's Core;
a story of a hollow Earth kingdom called Pellucidar. In the story,
adventurers drilled their way into the Earth. As they went ever deeper, the
force of gravity reversed direction, and they began climbing "up"
into the land of Pellucidar. When they "surfaced," they stood upright inside
the hollow shell of the Earth, held there by the gravity generated by the mass
of Earth directly beneath them. Assuming the Earth really is a hollow shell,
would gravitation work that way?
A:
No. In fact, it can be shown that there is no net force of gravity at all
inside a hollow Earth! The mass of the Earth directly under your feet would
indeed generate a gravitational force on you (as Burroughs surmised), but so
would the mass of Earth far over your head. Although the mass over your head
is far away, there is a lot more of it than the mass under your feet. For a
perfect spherical shell, you can mathematically show that the net force of
gravity is zero. In "reality," there would be small forces acting on you
due to mass concentrations within the Earth's crust, the centrifugal force
of the Earth spinning (about 0.3% of a "gee" at the equator), and because
the Earth is an imperfect sphere. But Burroughs was wrong -- You would float
in Pellucidar!
Congratulations to John D. Winstel.
Week of 11/23/98:
Q:
When machine guns are used in aviation dogfights, incendiary tracer
bullets are often mixed with the ordinary bullets at regular intervals.
The incendiary coatings (often red phosphorus) ignite at about five hundred
degrees Fahrenheit as the tracers exit the muzzle, allowing the pilot to see
where the bullets are going. However, if the pilot aims exactly at where the
tracers are going, he is guaranteed to miss with the bulk of his ammunition!
Why?
A:
The combustion of the coating alters the surrounding airflow, and the
trajectories of the incendiary bullets are different than the ordinary bullets.
Congratulations to Nicolas Cousineau.
Tracer bullets provide a good example of drag reduction via "base burning."
The red phosphorus combustion effectively pressurizes the flat rear base
of the tracer bullet (an area that would otherwise be a low-pressure
recirculation zone) and greatly reduces its "base drag." The tracer
bullets fly significantly farther than ordinary bullets.
- The Aeroquiz Editor.
Week of 12/14/98:
First in a series of aerospace logic problems!
Q:
There are three closed hangars at the top secret Area 51 at Nellis
Air Force Base. One hangar contains Mach 10 spyplanes, another
contains alien flying saucers, and the other contains both
spyplanes and flying saucers. Each hangar has a sign. One sign
says "Spyplanes," another sign says "Saucers," and the other sign
says "Both." However, to confuse the onlookers peering through
high-powered telescopes who believe that the truth is indeed out
there, each hangar is labeled incorrectly. You happen to have three
remotely-controlled door openers, one for each hangar door. From
your position in the desert, and at great personal risk, you can open
the hangar doors. The doors only open wide enough to see one vehicle
inside before they are stopped and the alarms go off. Opening doors
takes time, and the more doors you open, the greater your odds are
of becoming Doberman lunchmeat. What is the fewest number of hangars
you need to see open to be able to accurately know their contents?
A:
One. If you open the hangar labeled "Both," that is.
Since it was stated that each hangar was labeled incorrectly, this
hangar will not contain both spyplanes and saucers. Suppose you saw
a spyplane through that door. Then that hangar would contain all spyplanes.
Now, what about the other two? The hangar labeled "Spyplanes" does not
contain spyplanes (since it's labeled wrong and because we now know which
hangar is the spyplane hangar), so it must contain saucers. And the
third hangar (incorrectly labeled "Saucers") must contain both saucers
and spyplanes.
Congratulations to Nicolas Cousineau.
Week of 1/11/99:
Q:
Many people fantasize about using a time machine to go back in time
and, for example, buy stock in McDonald's or place a bet on the New York Jets in
Super Bowl III. If you could travel back to 1920, would it be a good
idea to invest in the Loughead Aircraft Manufacturing Company?
A:
This is sort of a trick question. The Loughead brothers established
their aircraft company in 1916. They pronounced their name "Lockheed."
Unfortunately, due to the glut of cheap war surplus airplanes, the
company folded in 1920. It would have been better to invest in the
Lockheed Aircraft Company, which opened for business in 1926, renamed
amidst concern that the former spelling would invite pronunciations
like "Loghead" or "Loafhead."
Congratulations to Dale J. Martin.
Week of 1/18/99:
Q:
In 1978, mountain climbers Reinhold Messner and Peter Habeler were the
first to climb Mount Everest entirely without supplemental oxygen. Everest's
peak is 29028 feet above sea level -- the approximate cruising altitude of
many commercial jet aircraft. Since air travel is much less strenuous than
climbing Everest, is it really necessary to pressurize the cabins of passenger
aircraft?
A:
Yes! For the general population, any altitude above 8000 feet can result
in hypoxia, and heart and respiratory complications. For the flight crew,
it is especially important that they maintain a high enough blood oxygen
content. At 18,000, the atmosphere is one half the density at sea level.
If the passengers were given weeks to aclimate to the reduced oxygen
available, then pressurization would be unnecessary. There is also the
pulmonary and respiratory edema, which is fatal, to consider.
Congratulations to Ed Wahler.
In fact, climbers Messner and Habeler were quoted as saying,
"Every 15 steps we collapsed into the snow to rest as we approached
the summit - then we crawled on again." If you avoided the acclimatization
process and flew without oxygen to 29028 feet, you would pass out quickly.
The altitude can also be deadly. High-altitude pulmonary edema (HAPE) and
high-altitude cerebral edema (HACE) can affect mountain climbers.
Interestingly, the first time anyone reached such a high altitude was in
the first turbocharged aircraft. In February, 1920, Major Rudolf Schroeder
of the U.S. Army flew a small biplane powered by a new turbocharged Liberty
engine to 33,130 feet. His oxygen system unexpectedly failed, he blacked
out, and his plane went into a steep dive. Luckily, the denser air revived
him as he fell and he landed safely.
-The Aeroquiz Editor
Week of 3/1/99:
Q:
"And so," the young engineer concluded his presentation. "If we just
increase our jet engine's combustor temperature by just twenty degrees,
we'll see these tremendous improvements in performance and operating costs."
"You do that," growled a grizzled, graybeard engineer as he looked up from his
antique slide rule, "and our turbine life span will be cut in half."
"What?" sputtered the rookie. "How can you know that? You need testing! Three
dimensional modeling! Hundreds of hours of computer time!"
"All I need to know," replied the veteran, "is my job."
How did he know?
A:
He knows the same way any of us with experience knows--he's been there and
done that. nThe temperature-RPM-time relationship to engine life is well
documented. The higher the temperature, the higher the RPM, and the
longer the period of time of higher than normal temperature and/or RPM,
the shorter the engine life. That's why jet aircraft have operating
limitations. My aircraft, the B-52, is limited to 30 minutes of military
rated thrust (MRT) but only 5 minutes of the higher takeoff rated thrust
(TRT). Exceeding these limits isn't likely to destroy an engine at any
given time, but exceeding the limits repeatedly cuts down on the engine's
life expectancy dramatically.
Congratulations to Norm Worthen.
High pressure turbines are designed and built to withstand a maximum
tensile stress without failing during a specified period of time and
operating temperature. The stress limit is the "creep rupture strength"
of the turbine material (times the appropriate safety factor), and it is
extremely sensitive to temperature. The Larson-Miller relation states
that the parameter T(C + log t) is a constant, where "T" is temperature,
"t" is the rupture life, and "C" is a material-dependent dimensionless property.
A good materials engineer knows the Larson-Miller relation!
- The Aeroquiz Editor.
Week of 3/15/99:
Q:
In order to certify, commercial jet aircraft engines are required
under U.S. Federal Aviation Regulations to undergo bird ingestion tests.
In controlled conditions on the ground, dead birds of varying sizes are
dramatically shot from special cannons into the engine's inlet.
There are several types of foreign object ingestion tests required under
FAR Part 33 rules, all of which are designed to establish engine safety.
Generally speaking, which test is more difficult to pass -- the
one-and-a-half-pound bird strike or the four pound bird strike test?
A:
Probably the one-and-a-half-pound bird strike test,
since I believe they must ingest multiple birds
simultaneously at that weight and only one for
the four pound bird.
Congratulations to Daniel Shedd.
For engines of sizes where both types of bird ingestion tests must
be conducted, the smaller bird test is usually more difficult to pass.
For the larger (four pound) bird test, the engine is allowed to fail.
As long as fragments do not pass through the containment ring, the engine
does not catch fire, and it retains its ability to be shut down, the
manufacturer can pass this particular test. Only a single four-pound
bird is launched. The one-and-a-half pound bird test, however, requires
that the engine remain operable for five minutes without more than a 25
percent thrust loss. In other words, the engine must be able to slice
and swallow the bird without a significant effect. In addition, depending
on the engine's size, up to eight of these smaller birds may need to be
fired in rapid succession into the fan face to simulate an airplane's
passage through a flock. Fans of the movie "Die Hard II" will be
disappointed to learn that the "John Amos Ingestion Test" is not required
for certification.
- The Aeroquiz Editor
Week of 9/20/99:
Q:
One worrisome type of aircraft malfunction is the loss of power to the
various external aerodynamic control surfaces that steer the airplane.
Though (thankfully) these occurrences are rare, it was a malfunction like
this that caused the crash of a United Airlines DC-10 at Sioux City in 1989.
One of NASA's more innovative and important aeronautics projects is the
development of a system that can help the pilot safely land a commercial
airliner that has suffered a complete failure of all of its aerodynamic
control surfaces. How can this be done?
A:
The pilots of the DC-10 in the Sioux City crash were able to gain some
control over the plane by varying the engine thrust levels. However,
manually controlling pitch and yaw by moving throttle levers is
a very difficult task. Bill Burcham of the NASA Dryden Flight Research
Center developed a control logic scheme that can be easily incorporated
into existing flight control computers that will permit the pilot to
steer the aircraft by only varying engine thrust. This concept has been
proven in flight test of both fighter and civil transport aircraft.
I worked with Bill in the sim labs here at Dryden before I was put on
the X-33 project. With his control logic in the loop I was able to
land a virtual L-1011 without flight control surfaces.
Congratulations to Brian Curlett.
Individual throttling
of the engines of a multi-engine airplane enables a pilot to control
the aircraft's orientation well enough to land safely. The system uses
standard autopilot controls already present in the cockpit, together
with new programming in the aircraft's flight control computers.
The concept is simple: for pitch control, the program increases
thrust to climb and reduces thrust to descend. To turn right, the
autopilot increases the left engine thrust while decreasing the right
engine thrust. Successful demonstrations of the system have been made
at NASA Dryden using a wide body MD-11 aircraft.
- The Aeroquiz Editor
Week of 10/4/99:
Q:
Although hard to believe, one of the "quietest" airplanes in the
world is the Boeing F-15 attack/air superiority fighter taking off with full
afterburners. Yes, this is a trick question, but can you figure out
why this is true?
A:
Since the F-15 can takeoff in a short distance and
then climb nearly vertically above the airport, its noise
"footprint" over neighboring communities near the airport
would be next to nothing as compared to a 747 which will
climb out at a much shallower angle. Therefore, even though
the F-15 is converting a serious amount of dinosaurs into
noise, nobody is around to hear it.
Congratulations to Kevin Finke.
The jet noise produced by an afterburning F-15 is ear-splitting.
However, when low noise takeoffs from populated areas are important,
F-15s often perform what are known as
"viking" takeoffs. After rotation and
lift off, thanks to its thrust levels being significantly higher than
its weight, the F-15 climbs virtually straight up and does not level off until
it is high enough that little noise propagates to the ground. If the F-15
had to certify under civilian aircraft noise regulations, its community
flyover noise level (officially measured at a point 6500 meters from the
point of brake release) would be very low. This is in sharp contrast to
heavy, long haul commercial jets, where community flyover altitudes are
often barely over a thousand feet. Another civilian noise measurement point,
however, is the so-called "sideline noise." For the F-15, this measurement
would peak somewhere around lift off (at a low altitude), and would be
very high!
- The Aeroquiz Editor
Week of 10/25/99:
Q:
"My data indicate a duration of 5.2," said the NASA rocket
scientist.
"I dispute your contention," replied the NASA trajectory
analyst. "The time interval was only 5.1. That asset was jettisoned
after its malfunction allowed an elongated post-percussion
trajectory. The backup systems then were engaged for periods
of 2.0 and 1.2."
The rocket scientist thought for a moment
and said, "Yes, you are indeed correct. 5.1 plus 2.0 plus
1.2 is nine."
Hints abound in this week's question!
Is their addition correct? Or can't NASA get good help these days?
A:
The starting pitcher was in for 5 & 1/3 innings before giving
up a home run. Two relief pitchers were brought in for 2 and
1 & 2/3 innings, respectively. 5 & 1/3 + 2 + 1 & 2/3 = 9.
Congratulations to Dale Martin.
Dale always uses baseball notation math during the World Series!
- The Aeroquiz Editor
Week of 1/10/00:
Q:
The "spoiler" wings often seen on the rear of many cars are intended
to increase stability and traction at high speeds by adding a "downforce"
over and above the weight of the car. In other words, they're upside-down
wings that provide a downward force instead of lift. Formula One racing cars,
for example, have wings that provide huge amounts of downforce at typical
racing speeds. If spoilers work on race cars, they must also
help to improve performance on Mom's minivan. Right?
A:
No, unless it is mummy Schumacher driving a very special minivan.
An aerodynamic force is not much felt at low speeds, for one, and I
suppose the compared proportion of the aileron's surface to the total
"wetted" and frontal areas of the vehicle is much less favourable to the
minivan than to the F1. So, the minivan's aileron is almost purely aesthetic.
Congratulations to Nicolas Cousineau.
On most cars bought off the showroom floor, spoilers are primarily a
visual styling cue added by the manufacturers to increase sales.
A few high-speed sports cars have genuinely functional spoilers.
And sometimes cars that have only modest power but are driven fast
are given functional spoilers. Audi's new TT, often driven on the
Autobahn, where speed limits are, well, not very limited, is an example.
But keep in mind that even the spoiler on Dodge's Viper GT2 is
aerodynamically trimmed to a neutral position.
And the new 174 mph Corvette C5 has no spoiler at all.
Spoilers on your average econobox cars (especially front wheel drive
econoboxes) do nothing.
- The Aeroquiz Editor.
Week of 1/31/00:
Q:
It's the week of the Super Bowl and time for a question about U.S.
football! Oakland Raiders star punter Ray Guy booted 1049 punts over thirteen
pro seasons for a whopping 44,493 yards with an average kick of 42.4 yards.
Only three of his punts were blocked. Historically, kickers were afterthoughts
in the draft. But that changed in 1973 when Guy became the first punter
to be drafted in the first round. No one had a sweeter "swing" than Guy,
who would kick the pig so high that other teams accused him of using
helium in the ball. And owner Al Davis wanted them to think that he did.
But seriously, would helium make Guy's footballs significantly lighter?
A:
I calculate a weight savings of about a tenth of an ounce.
Congratulations to Chris Snyder.
So do I. Using regulation football dimensions (about 11 inches long and
21 inches around the middle), I get a volume of about 129 in3.
Using a pressure of 10 psig and good fall football weather of 518 degrees
Rankine, I get a weight savings of 0.13 ounces, making a 14- to 15-ounce
football about one percent lighter. I leave it to you to decide its
physical and psychological significance!
- The Aeroquiz Editor.
Week of 2/21/00:
Thanks to Alan Nies for submitting this
week's Aeroquiz!
Q:
Six aerospace industry executives visit a jet engine component
warehouse. Each executive represents their company. Three of them
are from aircraft manufacturing companies; the other three represent
the engine manufacturing companies that are each partnered with one of
the airframers. Each of them buy as many components as they pay in
dollars for each component (that is, if an executive buys 5 components,
they cost 5 dollars each; if an executive buys 17 components, they
cost 17 dollars each). Each of the aircraft company executives
spends exactly 63 more dollars than their engine company partners.
The airframers are Boeing, Lockheed-Martin, and Gulfstream. The engine
companies are General Electric, Pratt & Whitney, and Honeywell.
Boeing buys 23 more components than Pratt & Whitney, and Lockheed-Martin
buys 11 more components than General Electric. What engine company
is partnered with each airframer?
A:
Boeing is with Honeywell, Lockheed-Martin is with Pratt & Whitney,
Gulfstream is with GE.
Congratulations to Brian Wallenfelt.
Brian didn't show his work, but I'll cut him some slack due to his
Illinois pedigree. (By the way, Brian, it's tough for Illini
alumni here in Buckeye country!) The solution goes something like this:
The amount spent by each executive is a square number, and each
aircraft rep spends $63 more than their engine company partner. First,
we must find three sets of squares that differ by 63:
A12 - E12 = 63 or (A1 + E1)(A1 - E1) = 63
A22 - E22 = 63 or (A2 + E2)(A2 - E2) = 63
A32 - E32 = 63 or (A3 + E3)(A3 - E3) = 63
As seen above, we must find three sets of two factors (integers) whose
product equals 63. Listing the larger factor on the left, and since
(A+E) must always be larger than (A-E), the only possibilities are:
63 x 1 = 63, or A1+E1 = 63; A1-E1 = 1
21 x 3 = 63, or A2+E2 = 21; A2-E2 = 3
9 x 7 = 63, or A3+E3 = 9; A3-E3 = 7
Solving the three sets of simultaneous equations:
A1 = 32
A2 = 12
A3 = 8
E1 = 31
E2 = 9
E3 = 1
These numbers represent the number of items that each rep purchased (as well
as the number of dollars paid for each item).
Since Boeing bought 23 more items than Pratt & Whitney, it is easily
seen that Boeing must be A1 (32 items), and Pratt & Whitney must be E2.
Similarly, Lockheed-Martin must be A2 (12 items), and General Electric
must be E3 (1 item).
And that leaves Gulfstream as A3, and Honeywell as E1.
Solution complete!
Boeing is partnered with Honeywell,
Lockheed-Martin is partnered with Pratt & Whitney,
Gulfstream is partnered with General Electric.
- The Aeroquiz Editor
Week of 5/8/00:
Q:
You are cruising in a commercial jet at 35,000 feet. You
look out your window. It's a nice day with the sun shining
overhead. You look along the span of the wing and
are surprised to see an irregular blur of light and shadow
dancing back and forth above the wing. You are just about
to cancel your order for a second martini when you recall
details from your compressible fluid dynamics class. What
did you remember?
A:
I remember that even while traveling at subsonic speeds
in an airliner, the local flow velocity over the wing can
reach the speed of sound (or higher) and produce shock waves.
What you're seeing is a weak shock produced by traveling faster
than the critical mach number for that wing.
Congratulations to Frank Brown.
Unless you're William Shatner in the "Nightmare at 20,000
Feet" Twilight Zone episode, you're seeing a shock wave!
As Frank wrote, there are often regions around the
wing surfaces where the flow has been accelerated to supersonic
speeds. When this occurs, there is a weak shock wave at the
downstream boundary between the subsonic and supersonic flows.
If the conditions are right, you sometimes can be lucky enough
to see the refracted light from the shock wave with your naked eye.
- The Aeroquiz Editor
Week of 10/16/00:
Q:
Some fighter aircraft have phony canopies painted on their
undersides. Why?
A:
For the same reason many animals, such as some moths or butterflies,
have fake eyes on their bodies or wings. In a fight with a bird,
a moth might escape if the bird mistakes a bright, fake eye on the
moth's wing for the real thing. The bird bites the "eye," and the
moth escapes with just a nick taken out of the wing. Likewise, in a
dogfight, an enemy fighter might mistake a fake canopy for the real
thing and become confused as to the actual orientation and direction
of flight of the target aircraft. All it may take is a split second
of indecision in the mind of the enemy for the target to gain an
advantage and either escape or become the hunter instead of the hunted.
Some ships have used "dazzle" paint schemes in the past to the same
effect. Such paint schemes were certainly visible, but they broke up
the ships' outlines and made direction and speed calculations
difficult for targeteers' firing solutions.
Congratulations to Norm Worthen.
If you can confuse your opponent in air-to-air combat, even
for a moment, you might be able to gain a favorable position on him!
Forward-swept wings may also cause a momentary disorienting effect.
- The Aeroquiz Editor
Week of 1/8/01:
Q:
"Turn off the lights when you're not using them," the NASA engineer
nagged his teenage son. "Do you think I'm made of money?"
This time, the boy was prepared for that tired old cliche and fired back
a well-reasoned reply: "But dad, it's January and cold outside.
We have an all-electric house and the heat is on. If I happen to leave
on a light, it's simply helping to heat our house. And at one hundred
percent efficiency, I might add!"
"Are you kidding?" the father replied to
his smug son. "In this house, we get nearly a three hundred percent heating
return on our electric power! You're wasting energy!"
Is that possible? Is he wrong? Does he have a secret NASA invention
hidden away in the basement? Or something ordinary he bought from the
HVAC guy down the street?
A:
Two words: Heat Pump.
Congratulations to A.R. Nies.
The house is equipped with an ordinary heat pump! Heat pumps are
popular in regions that are not too cold, or even in regions that are
indeed cold, but have no cheaper heating alternatives available. In
moderately cold climates, heat pumps typically provide much more heat energy
than the mechanical energy put into them. This is done by "pumping" what
heat may be outdoors into homes via a working fluid and heat exchangers.
On a very cold day, there may be comparatively little heat outside, which
is why they are not very popular in northern climes. The local price
of electricity relative to natural gas or other energy sources is also
a factor. But in moderately cold climates, heat pumps perform very well.
A resistance heater (like the light bulb in the question) has a so-called
"coefficient of performance" of one hundred percent, but good heat pumps
have coefficients around two or three hundred percent. No alien
technology -- just thermodynamics!
- The Aeroquiz Editor
Week of 1/22/01:
Q:
The U.S. Marine crew chief backed away from his mostly disassembled
engine and squinted up at the hot South Pacific sun. It was 1944 in
the Solomon Islands and the chief had to keep his airplanes flying.
"Whaddaya think, sarge?" asked the grease-covered kid from Nebraska.
"The fuel mixture's the problem," replied the chief. "These new
carburetors vibrate too much and the fuel foams up. At high engine
speeds, the motor's running lean."
"Guess there's nothin' we can
do about it out here in the middle of nowhere," concluded the kid.
"Naw, it'll be allright," said the chief. "Go and get me my sinkers
outta my fishin' tackle box and a roll of tape. We'll fix these
airplanes."
What does the chief have in mind?
A:
Would he be fastening
the weights to the carburetor's body so as to change
the mass, and therefore either dampen the vibration
or alter the natural frequency?
Congratulations to Dan Shedd.
The added mass of the sinkers changes the carburetor's natural
harmonic frequency to something lower than the engine's vibrational
frequency. The carburetor then can operate with significantly less
vibration and the fuel foaming problem disappears.
- The Aeroquiz Editor
Week of 3/26/01:
Q:
Interestingly, a total of three core modules were built for the Russian
Mir Space Station. These 20.4-ton, 43-foot long modules were designed to
provide living quarters, life support, power, scientific research
capabilities, and a docking area for the Mir Station. The most famous
of the modules fell from its orbit last week after 15 years aloft. One of
the other modules is in a warehouse in Russia. The last module is
a) On display in a distinguished Moscow museum
b) On the launch pad at Baikonur, Kazakhstan, ready to lift off!
c) Hidden somewhere at the top-secret Area 51
d) A popular family tourist attraction in Wisconsin Dells
A:
D!
Congratulations to "KMB."
Hundreds of thousands of people have toured the Mir exhibit since May of
1997 when it was put on permanent display at Tommy Bartlett's Robot
World & Exploratory in Wisconsin Dells, Wisconsin. Tommy Bartlett
purchased the authentic Mir core module from a Moscow museum.
- The Aeroquiz Editor.
Week of 4/30/01:
Q:
"Now this lovely couch," droned the antique furniture salesman,
"is quite unique. It is absolutely form-fitting -- a plaster cast
was made for its occupant and the charming fiberglass shell you see
here was crafted and contoured for his specific shape. A tasteful
crushable honeycomb material is bonded to it and it is lined with
an elegant padding."
"Sounds like 'the occupant' was a real couch
potato," remarked the customer.
"Oh no, sir, quite the contrary.
The people who used these couches were among the fittest on earth."
What is he selling?
A:
It's a chair fabricated for space travel. The fitness of the user
is required to be at peak before liftoff.
Congratulations to Vern Newsome.
Each of NASA's early astronauts had support couches constructed
that were contoured to their specific shapes. These couches were
designed to evenly support body loads during all phases of flight and to
protect from the acceleration forces of launch and reentry.
During the Mercury Program's development, NASA was concerned over
predictions that the ballistic capsule, after separation from the
Atlas booster, in some emergency situations would be subjected to
over 18 gees of deceleration from atmospheric drag. Navy Lt Carter
Collins had, at that point, ridden 12 gees in a centrifuge.
The day after learning of the need for higher gee testing, he rode
the centrifuge in 2 gee increments: 14, 16, 18, and 20 gees!
Collins sustained no injuries, and in fact he walked out of the
centrifuge and later drove home, despite some nausea caused by
inner ear stress.
-The Aeroquiz Editor
Week of 5/21/01:
Q:
Lightweight materials, leading edge wing slats for enhanced lift,
rudders for yaw steering, and aerodynamic camber provided by
structurally-stiffened skin. All characteristics of modern airplanes,
right? Or could they also be found over 200 million years ago?
A:
Look no further than the cousins of the dinosaurs, the pterosaurs.
This group of creatures had all the features mentioned. Hollow bones
made for a lightweight frame, the wings had "droops" over the leading
edge that formed a slat of sorts, the long tail with a paddle on the
end formed a moment arm with aerodyamic surface for a rudder, and the
thin, leathery skin closely followed the contours of the "finger"
bones for a cambered shape. The high lift created by the larger pterosaurs
made these guys great gliders that could soar for hours on prehistoric
thermals.
Congratulations to Norm Worthen.
Pterosaurs were likely as ecologically diverse as modern birds,
and were in existence long before the first bird took wing.
Pterosaurs were remarkably lightweight, in part due to very thin-shelled,
hollow bones. Even the Quetzalcoatlus northropi, with its
nearly 40-foot wingspan, probably weighed no more than a child.
A short pteroid bone extending forward from the arm may have helped
some pterosaurs control a forewing membrane -- much like a leading
edge slat on a modern airplane wing. Many pterosaurs had cranial
crests that may have been used as rudder-like steering aids.
And although the actual wing skin rarely fossilizes, a nicely preserved
wing membrane from a Rhamphorhynchus has small corrugations
that may have added strength, stiffness, and camber to its wings.
- The Aeroquiz Editor
Week of 9/3/01:
Q:
"Here you are, sir. You'll be in seat 14A. Have a nice trip." The
airport ticketing agent smiles and hands you a boarding pass.
As you walk towards the waiting area near your gate, you notice from
your itinerary that your "flight equipment" is no longer the familiar old
turboprop aircraft that usually services your route. Instead, it is an
Embraer ERJ-135. "Huh, that's one of those relatively new regional
jets. They're not that big. So seat 14A must be way back near the tail."
You're curious, so you queue up the wireless modem in your laptop and
take a look at the 135's seating accommodations on Embraer's web page.
"Technology sure is great," you think. But your bemusement turns to
panic when you see that the ERJ-135 has only 13 rows of seats on the
port side and only 12 rows of seats on the starboard side! "I don't
have a seat!" you exclaim to the ticket agent. "I have to be in
Hoboken by noon!"
"Don't worry, sir," laughs the agent.
"We have a seat for you."
How can that be?
A:
I guess it is like in these buildings where, to accomodate for
superstitious persons, the 13th floor has been simply omitted in
the numerotation. The floors go directly from 12 to 14.
Congratulations to Nicholas Cousineau.
To soothe all the triskaidkaphobics out there, airplane seating nomenclature
is a lot like hotel and skyscraper floor labeling! The fear of the number
13 can be traced to Norse mythology. Odin threw a dinner party one night
in Valhalla and invited 11 divine friends. Unfortunately, the evil
trickster Loki crashed the party and brought the count to the devil's
dozen. When the good-guy god Balder tried to throw Loki out on his ear,
Loki killed him with a spear made of mistletoe (a kind of "kryptonite"
for Norse gods).
- The Aeroquiz Editor
Week of 9/24/01:
Q:
Zaphod and Arthur spotted the orbiting casino resort station as
they approached the desert world of Kakrafoon. In a few minutes,
Zaphod had maneuvered their ship so that the two spacecraft were in
circular orbits that were identical in every respect, except the
casino was ten kiloquats ahead of Zaphod and Arthur. "I can't wait
to have a pan galactic gargle blaster," said Arthur. "Let's increase
our speed so we can catch up!"
"No, silly," replied Zaphod. "To catch
up, first we need to slow down."
How would that help?
A:
The spaceship is in a stable circular orbit, so increasing the
tangential velocity will increase the centripetal acceleration,
throwing the orbit out of balance and increasing the stable
orbital diameter. They must slow down to drop towards the planet,
then Eddie the onboard computer will tell them when to point
upwards and apply thrust in order to rendezvous with the casino
from below (if he has finished calculating the reason for the
existence of tea).
Congratulations to Andrew White.
As the laws of Kepler and Newton help to point out, increasing your
orbital speed in the direction of flight will only put you in a
higher, eccentric orbit with a longer orbital period. Counterintuitively,
you would immediately start to fall behind your rendezvous target. This
problem vexed the astronauts and ground engineers of the earliest Gemini
rendezvous mission until the details were worked out.
A more appropriate thing to do might be to slow down, drop into a lower
eccentric orbit, perform an orbital circularization maneuver, and wait
until you've passed underneath your target. Then you could perform
the opposite sequence to rendezvous.
- The Aeroquiz Editor
|
|
|
|
