Wednesday, March 18, 2009

You're Getting Warmer (?)

This quote from Michael Steele came to my attention by way of Andrew Sullivan:

"We are cooling. We are not warming. The warming you see out there, the supposed warming, and I am using my finger quotation marks here, is part of the cooling process. Greenland, which is now covered in ice, it was once called Greenland for a reason, right?"

OK ... Steele would do well to stay away from microphones for a while, but he's got a tiny, minuscule point buried in there. But it's probably not the one he thinks it is. There's come chicanery going on in the climate change debate, but that doesn't really change the fundamental conclusions.

Here's the graph that started it all:

This graph, based on data analyzed by Mann, Bradley, and Hughes, appeared in the 2001 IPCC report. What this data set appears to indicate is a dramatic increase in temperatures during the 20th Century, a change that was entirely imputed to human causes.

I have had a problem taking this interpretation of the data seriously. The reason for that is that, for a long time, Mann refused to divulge the analytical techniques he used to derive the graph in the first place. As this Wikipedia page shows, he eventually came clean on how he got the data, but still ... in science, repeatability is key. As I said earlier, if you can't describe your procedure well enough for another researcher to duplicate it, you probably don't understand what's going on as well as you think you do, and if you won't, you've probably got something to hide. Now, it's possible (even likely) that Mann had nothing to hide. I tend to assume that most professional scientists have a sufficiency of professional integrity. But for a while there, he acted like someone who was hiding something. And you can't really trust diddled data.

But even discounting that graph, this one was the clincher for me:

This isn't junk processed through some super-secret filter. This is pure hard-core, read-it-and-weep data. The one incontrovertible, undeniable fact revealed by the ice core data is that current CO2 concentrations are at simply absurd levels.

Now, knowing that, what can we reasonably expect? What kind of warming will this result in?

The thing you must realize straight away is that the climate is a Sun-powered machine. Virtually all of the energy within the world's weather systems comes from the Sun. Further, daytime high temperatures are governed by solar heating of the surface, while night-time low temperatures are governed by how much heat can escape into space overnight. Atmospheric composition, then, will have its major effect not on daytime highs, but on overnight lows.

Now, let's look at the heat retention capacity of various gases within the atmosphere. From the Wikipedia article on the greenhouse effect, we see:

* water vapor, which contributes 36–70%
* carbon dioxide, which contributes 9–26%
* methane, which contributes 4–9%
* ozone, which contributes 3–7%

In a damp climate, water vapor dominates. In such climates, water vapor contributes 70% of the greenhouse effect, with CO2 only contributing about 9%. In dry climates, it's a more even split, 36% versus 26%. So, the most prominent effect is going to be in cold, dry climates, such as we see around the North Pole, and in Antarctica. The least prominent effects are going to be in warm, humid climates. I wouldn't expect a huge swing in temperature there due to atmospheric composition.

Now, how does this square with what we see happening? The reduction in Arctic sea ice seems to be bearing this out. There has also been a reduction in Antarctic sea ice. Both cases point to an elevation of low temperatures to the point that the sea ice has begun to melt.

Melting sea ice won't change the overall ocean levels. You can try this for yourself with a plastic cup, some water, an ice cube, and a Sharpie. Put some water in the cup, drop in an ice cube, and mark the water level. When you come back after the ice cube has melted, the level will not have changed. This is because ice contracts as it melts. Glacial ice is another matter entirely, as is Antarctic pack ice, since that melt-off adds new water into the system.

In any case, we're currently running an open-ended experiment on elevated CO2 levels, which is probably unwise. We don't really know with iron-clad certainty what the effects are going to be, but the effects probably aren't going to be especially pleasant. Sooner or later, we're going to have to get a grip on this problem. Besides reducing emissions now, we probably ought to be looking at ways we can reduce the amount of CO2 that's already in the atmosphere. One idea I've heard about is promotion of algae growth in the oceans ... which may be a good idea, up to a point. Done excessively, it can deplete the ocean of oxygen, which isn't very helpful, either.

To make a long story short, I haven't always trusted global warming proponents, but I haven't complained much because we already have a sufficiency of good reasons to get off of fossil fuels posthaste. They fill our air with crud, they enrich people who hate us, and aren't those two reasons good enough by themselves?

Tuesday, March 17, 2009

You Got Questions? They Got Answers...

This new service, coming in May 2009, is going to be so great...

Google works pretty well for most things. It's a decent research tool. But sometimes, that's not what you really need. Sometimes, you just need the answer to a (possibly) obscure question. You don't care to sift through various web pages for it, you just need to know. Like, say, "What was the world's population in 1950?" Or, "How long is Manhattan Island?"

When it goes live, you'll be able to type the question directly into WA's box, and out pops the answer.

I don't know about the rest of you, but I'm really stoked about this one. It's easily the best thing to come down the pipe since, well, Google.

Monday, March 16, 2009

Great Moments in Aviation, Part IX

As I wrote earlier, the pioneering age of aviation ended at or around 1910, once the airplane had assumed its now-familiar form. A new chapter opens in the fall of 1914, as an assassination in Sarajevo plunges Europe into war.

But the story isn't quite the one you'd expect. Conventional wisdom has it that wartime is a great spur for technology. This is mostly true. It does tend to focus the mind, and you get more immediate feedback as to what works and what doesn't. An active enemy is the harshest critic of performance that you'll ever find. But by and large, although the airplanes of 1918 were substantially faster and more powerful, they still employed the same basic ideas that they had in 1914. Granted, you do see the first all-metal frames used during WWI. But the most striking innovations were in the uses of the airplanes themselves.

You see, going into WWI, no one had the remotest idea what these newfangled contraptions were good for at all, if indeed they were good for anything.

But there was one immediately obvious application. Flying high above the trenches, a pilot could see for miles. He could see the disposition of the enemy forces in a way that no ground-based scout could. Almost overnight, aviation co-opted cavalry's centuries-old job of scouting and finding the enemy. Airplanes with camera-equipped observers became a common sight over the front. For the first time, generals had something close to a God's-eye view of the battlefield. Not that it did them a whole lot of good, since they had no real notion how to go about attacking a prepared position defended with machine guns. They tried, both sides, with the result being appalling slaughter and stalemate. But still, the observers flew above it all, capturing it on film.

Enemy planes flying overhead are never a good thing. Immediately, people began to talk about how to keep that from happening. You want your guy to be able to do it, but you want to deny that capability to your enemy. So, one fine day, a pilot took a pistol aloft with him, and tried to do something about it. Or so the story goes. I think it had to have been an observer. With a pilot, one hand and both feet are pretty much busy full-time; a pistol-waving pilot is either shooting left-handed or trying to fly left-handed. Neither one is liable to end well. Anyway, the pistols-aloft experiment pulled up a big fat zero, but the basic idea was thought fairly sound.

The next iteration was to mount actual machine-guns on the airplanes. Two variations were tried, with varying degrees of success. Two-place scouts were modified such that the observer had a swiveling machine-gun mount. In theory, this would give him a wide field of fire. In practice, he was as likely to shoot his own tail off as hit an enemy airplane. The more successful configuration involved taking a fast single-seater, and mounting one or two machine-guns facing forward. The pilot aimed his guns with the nose of his airplane. This was the configuration adopted as standard for pursuit airplanes. Pursuit airplanes' primary mission was to interdict enemy scouts, but quite often pursuit airplanes ended up skirmishing with each other. The best of these pilots became famous: Richthofen, Voss, Foch, Rickenbacker.

Another idea that was tried out early on was dropping explosives out of airplanes. The first bombing experiments were shockingly crude. Basically, the observer carried a few up with him, and then held them out over the side to drop them. They hit the ground every time. Beyond that, the system's accuracy left much to be desired. Then someone hit on the idea of carrying the bombs underneath, with a release mechanism, so that they could be aimed somewhat better. This was a distinct improvement. The early bombers couldn't hit as hard as artillery could, not even close, but the crew could see the target in real time. Meager as their bomb load was, they played a non-trivial part in the Saint-Mihiel offensive late in the war.

Although both sides went into WWI not knowing what to do with aviation, by the time the war was over, the basics of air war doctrine had been set. Three of the basic four functions of airpower had been defined: reconnaissance, air superiority, ground attack. Only transportation hadn't been seriously attempted yet. But it would be, and soon. The 1920s would bring a series of innovations that would make the airplane a lasting part of the civil economy.

Saturday, March 14, 2009

Earth: Rare, or Dime-a-Dozen?

On March 6, a Delta II rocket lifted off from Kennedy Space Center in Florida, carrying the Kepler space telescope towards an Earth-trailing Solar orbit. Kepler's mission is to look for Earth-like planets circling other stars. Metaphysically speaking, this is related to the biggest question left that Science has a fighting chance of answering: Are we alone? (The bigger ones, like "Is there a God?" or "Is there an afterlife?" are beyond the purview of Science, as most of us understand the term.)

I'm not really sure what to expect. Frank Drake once developed a famous equation to estimate the number of civilizations in the Galaxy. One can work backwards from that to get a hack at how many Earth-like planets there are, making the rather bold assumption that intelligent life can only develop on Earth-like planets. If you make some generous assumptions, then it seems likely that the Galaxy is as jam-packed with ETs as the Cantina from Star Wars.

Or maybe not. I read the book Rare Earths by Ward and Brownlee back when it came out in 2000, and the argument looked like it carried some weight. Basically, Ward and Brownlee argued that although single-celled life may be near-ubiquitous in the Universe, the leap to multi-celled life was a darned chancy thing, and may have only happened rarely. It's definitely a point to ponder, even if you don't necessarily agree with the premise. It's always dicey to make statistical inferences from a sample size of one, and Earth is the only habitable planet we know of. The Kepler mission will hopefully add some grist to the discussion. Because, when we start talking about ETs, the question inevitably comes up, "Where are they?"

Fermi's Paradox: if you can't swing a cat in the cosmos without smacking an ET upside the head, why haven't we seen any real traces of them?

We're left with a number of possibilities: (a) They exist, but won't make contact; (b) They exist, but can't make contact, or (c) They don't exist. There are several different flavors of (a) and (b).

One: They are prohibited by their own law from contact. Think "Prime Directive" from Star Trek. I find this reason slightly fatuous. Although it would explain why putative ETs have taken such great pains to avoid contact. They're not afraid of our cops or military. They're very afraid of their own. The ones who actually strut their funky stuff down here are poachers.

(As an aside, I tend to be very skeptical of claims of ET visits, especially in modern times. The reason is that any form of travel that involves a large change in velocity will invariably also involve a large amount of waste heat. This is elementary First Law of Thermodynamics stuff. Energy cannot be created or destroyed. Therefore, if you shed a boatload of kinetic energy, it's gotta go somewhere. You can't just wave a magic stick at it and make it go away. So, the easiest thing to do is radiate it away into space as waste heat. Which would be a gigantic HERE I AM beacon to anyone with an infrared telescope... Someone's bound to notice, I'm just sayin'. Given that no one has, I'm inclined to think it hasn't happened. Anyway...)

Two: They're not prohibited from contact, but refrain anyway because we're so incredibly gauche. This, I can believe. "OK, I'm off to study the natives of Sol III." "What? Are you mad? They still fling poo at each other, don't they?" "Well, I don't suppose I actually have to go all the way there..."

Three: Interstellar travel is rather harder than we've been led to believe. In the stories, heroes flit around the Galaxy like we drive over to the Stop-N-Go for a Slurpee. It ain't that easy, folks. Interstellar travel is, in my professional opinion, somewhere between damn hard and practically impossible. The easiest part is navigation. And that's not all that easy. When you're out far enough away from the Sun, you have no reliable position references. You can get a red-shift from the Sun, and a blue-shift from your target star, and figure out how fast you're going. And if you can get angle measurements from four widely-separated stars, you can triangulate your position, with some fat margin for error. If you're not careful, you can miss the star you're shooting for, and then you're in a whole world of trouble. But with care and attention, you can get the details right, and at least theoretically arrive in the right place. But then, there's the issue of propulsion to consider. We know we can't exceed the speed of light in normal space. So, if we want to fly to another star within a human lifetime, we have to do it at a fairly high speed. Here's the problem. Let's say we've got a 1000-ton ship moving at 99% the speed of light. How much energy does that take, relative to how much energy we produced in toto this year? The kinetic energy of this spacecraft is ten thousand times greater than the world's entire energy output in 2005. Chew on that for a second. How in the roaring purple Hell do we get that much energy in one place at the same time? Well, there's always antimatter ... but brother, that much antimatter all in one place is a damn scary prospect. And understand that this is coming from a guy who wouldn't sweat too much from living next door to a nuclear power plant. I'm not sure I want to live on the same continent as an antimatter fuel plant! That crap's dangerous. One fuel leak, just one, and foom! Your ship just became a blue flash. (Someone once said that gamma-ray bursts were high-tech industrial accidents. I'm not sure he was wrong...)

Now, we humans are extraordinarily stubborn. If something's physically possible at all, one of us is bound to try it eventually. No matter the hardships, no matter the obstacles, one of our descendants will be hard-headed enough to make it so. But, not all creatures are quite so obstinate. It wouldn't surprise me at all to see our would-be visitors look at the vast deeps of interstellar space and say, "Hell with that. I've got better things to do."

Four: We're not alone alone, but intelligence is sufficiently sparsely distributed that we're alone for all practical intents and purposes. If there are only two or three intelligent ET species in our Galaxy, and they're on the other side, it's gonna be quite some time before we see any of them face-to-face. By "quite some time" I mean some thousands of years.

In any case, it's going to take Kepler a while to scan its assigned areas of local space. Hopefully we'll find something interesting. But even if we do find an Earth-like planet elsewhere, we're still stuck with the one we've got for the foreseeable future. None of us are going anywhere anytime real soon.

Thursday, March 05, 2009

Great Moments in Aviation, Interlude

By 1910, when Alberto Santos-Dumont built the Demoiselle, the basic form for all airplanes to follow had been set. There would be a few variations, but from then on, most would follow the same basic plan.

The obvious question is: why? Why this shape, and not another? The answer is that, in engineering, form follows function. To illustrate this, we'll compare the standard layout with the Wright Flyer layout, which we saw last time.

The Wrights had decided that control was the central problem, and therefore built their fliers to be very maneuverable. An unfortunate consequence of this was that the Wright designs were all statically unstable. This is a good thing from a maneuverability standpoint. Since the vehicle doesn't really want to fly straight and level, it's always ready to respond to a pilot command to do something else. But if you do want to fly straight and level, it takes a lot of work to keep it that way. So, the Wright fliers were easy to steer, but hard to fly. (An unstable aircraft might well be impossible to steer or fly. It all depends on the details.)

The European pioneers, on the other hand, preferred designs that produced stable gliders. That is, they would glide straight and level without any need for a pilot on the loop. This greatly reduces a pilot's workload in straight and level flight. Although they were harder to steer, they were much easier to fly.

By 1910, designers knew well what features of an airplane's design conferred the stability that they desired. In the pitch axis, you design for static margin. In the roll axis, you design for dihedral. Passive stability is relatively easy to achieve in the yaw axis, with the placement of the vertical stabilizer. (In practice, yaw and roll axes tend to be tightly coupled, and you really can't analyze them separately. But these illustrations still suffice for a basic explanation.)

Static margin is simply the difference between the location of the plane's center of gravity and the location of the plane's center of lift. Designers like for this to be a small, negative number. The reason they want it negative is that a negative static margin confers resistance to pitch-up gusts. If you tilt the nose slightly upwards, and the CG is ahead of the center of lift, then the natural tendency of the nose will be to fall back to neutral. But because you've built in a nose-down torque, you need to design the horizontal tail to provide negative lift, so that there will be no tendency to rotate in the cruise configuration. This also provides stability if you experience a nose-down gust, since the horizontal tail will produce more lift as the nose points downward, providing a net nose-up torque, again tending to reset the pitch attitude to neutral.

Dihedral has to do with the tilt of the wings of the airplane. This is easiest to see in low-wing monoplanes.

This configuration benefits roll stability. With slightly upswept wings, a low-wing plane will tend to roll back to vertical if upset in roll to the left or the right. The lower wing will produce a greater vertical force than the higher wing, providing the restorative torque. This also induces a side force that the pilot will have to counteract with a bit of rudder. High-wing monoplanes generally have little actual upsweep to the wings. Since the center of gravity is usually below the wing plane in this case, there's a pendulum effect that basically does the same thing, restoring the airplane to the horizontal with little extra effort on the pilot's part.

The placement of the vertical tail is perhaps the simplest and most obvious thing. The vertical tail is in back for the same reason that fletching is on the back of an arrow: weathervane stability. If you tried to shoot an arrow backwards, what would happen? The very first gust that pulls it off-center will pull it farther and farther off-center, until it's flying with the fletching in back again. Once designers realized this fact, no one ever seriously contemplated doing it any other way.

In my opinion, the year 1910 brings to a close the first chapter in the history of aviation. It was, in a sense, the end of an era of innocence. The pioneers all looked forward to a peaceful future, one where ever-advancing airplanes would knit mankind's far-flung civilization ever closer together with bonds of peaceful travel and commerce. None of them foresaw what lay only four years in the future, nor would they have believed it had anyone told them.

In 1914, the airplane would go to war, and the second chapter of aviation's history would begin.

Sunday, March 01, 2009

Great Moments in Aviation, Part VIII

The story becomes somewhat crowded between 1896 and 1906. The year 1896 saw three pivotal events in aviation history. Octave Chanute brought together several glider enthusiasts on the shores of Lake Michigan, testing various kinds of gliders. Later that year, Otto Lilienthal died in a glider crash. And an American scientist, Samuel Pierpont Langley, built and flew a small unmanned heavier-than-air flying machine powered by a small steam engine.

Langley was, at the time, the founding director of the Smithsonian Astrophysical Observatory. In the 1890s he began research into the problem of powered flight. His first attempts were duplications of Alphonse Penaud's work with gliders powered by rubber bands. He was never entirely successful duplicating Penaud's results, but was successful enough to continue his own avenues of research. Langley focused on the problem of power, pushing to develop ever more powerful engines. In November of 1896, one of his powered machines took off and flew for 5000 feet. His success earned considerable recognition. In 1898, he received grants from both the War Department and the Smithsonian to develop full-scale manned versions of his Aerodrome. He soon abandoned steam engines in favor of the new internal-combustion technology. Over the next five years, he would refine the design of his Aerodrome, and that of its engine. Charles Manly and Stephen Balzer developed a 50-horsepower engine for use in the full-scale Aerodrome. In October 1903, the Aerodrome was ready for its first flight.

Or so they thought. Charles Manly took the controls for the first attempt. The Aerodrome, you see, didn't have a landing gear. It was launched by catapult. And Langley chose the Potomac River for his flights, for the stillness of the air. The Aerodrome, then, would reach flight speed by catapult launch off of Langley's houseboat. On the first attempt, a wingtip caught the edge of the catapult, sending the Aerodrome into the Potomac. Manly managed to extricate himself from the wreckage, and swim back to the houseboat. They also managed to salvage most of the wreck, and rebuild the Aerodrome in time for another test on December 8th. (Oh, so close, so close...) But the second test fared little better than the first. The Aerodrome cleared the catapult fine. But the Aerodrome immediately experienced what we now call "wing torsional divergence", and basically disintegrated in mid-air. Manly was once again dunked into the Potomac, along with what was left of the Aerodrome, and once again managed to swim to safety. Manly was 0-for-2, and promptly retired from the test-pilot business. The War Department was singularly unimpressed by these results, and terminated Langley's funding. One of Langley's assistants, Glenn Curtiss, made numerous improvements and upgrades, and eventually flew a heavily modified Aerodrome in 1914, somewhat salvaging Langley's reputation. But they missed their shot at being first to fly, by little more than a week, as it turned out.

Wilbur and Orville Wright also took up the challenge right about this time, in the late 1890s. They first became interested in roughly 1896, when they learned of Chanute's glider experiments at Lake Michigan. They began to study up on what had been done so far, and in May 1899, Wilbur wrote the Smithsonian Institute with a request for information and publications on aeronautics. Their study led them to believe that the key problem to be solved wasn't power so much as it was control. Provided that you could build a glider that was fully controllable in all three axes, you could always put an engine on it and fly. Their key innovation was their development of wing-warping for control. They noticed that birds in flight would control their direction by changing the orientation of their wing-tips, and sought to mimic this method in their biplane gliders. It proved to be quite successful. Within three years, they developed a very efficient and very controllable glider. In 1903, they began work on integrating an engine into this design. The engine they ended up with was a very small 12-horsepower engine, but very lightweight. In December 1903 they were ready to give it a try. On December 14th, the flipped a coin to see who would try it first. Wilbur won the coin toss, but the flyer stalled immediately after takeoff and sustained minor damage. Three days later, after repairs, Orville Wright took to the air, and flew under power and under full control for 120 feet.

Although they were first, the cautionary proverb "be careful what you wish for" is very relevant to their lives after that first flight. They undoubtedly built the first powered, fully controllable airplane. Also undoubtedly, they built the first airplane capable of flying a full 360-degree turn while airborne, which they did in 1906. But their technical success did not always translate into business and financial success. The Wrights had a well-documented penchant for secrecy that made them extraordinarily difficult to work with. They were mortally afraid of giving away their secrets. Most of their time and energy were consumed in battles both over their patents, and with the Smithsonian over credit for the first flight. Neither of them really had time anymore to devote to further work on their actual product. Wilbur died of typhoid in 1912, and Orville sold the company in 1915.

The last of the three major pioneers at work in the late 1890s was Alberto Santos-Dumont. Many Americans will have never heard of him. But if you think about it, there's something very curious about aviation nomenclature. Why, if the first powered airplane was invented by an American, do so many airplane parts have French names? Aileron, fuselage, empennage, and so on ... Well, it's because the world didn't stand still while the Wrights were tied up with all of their legal death-duels. And Santos-Dumont was largely responsible for the popularization of aviation in Europe.

He came late to heavier-than-air vehicles. In the late 1890s, he started building dirigible balloons. That is, hydrogen balloons that mounted both engines for thrust, and movable vanes for directional control. It wasn't a particularly uncommon sight to see Santos-Dumont flying over Paris at rooftop level, sailing over the streets under full control, occasionally stopping at fashionable outdoor cafes for lunch. In 1901, he won a 100,000 franc prize for flying from the Parc Saint Cloud to the Eiffel Tower and back within 22 minutes. After this, he began to turn his attention to heavier-than-air vehicles. In 1906, his first successful design, the 14-bis, flew in full view of the public in France. This became the first flight that was certified by an independent body, the Aero Club de France. His career as an aviator was sadly cut short, though, when he fell ill with multiple sclerosis in 1910. But he had inspired several other Europeans to follow suit, including such aviation pioneers as Louis Bleriot, Louis Breguet, and Henri Farman.

Alberto Santos-Dumont is also notable for another reason. When he was making his record-setting flights with his Number 6 dirigible, he noticed that he was having considerable difficulty consulting his pocket watch for time checks. In any kind of flying machine, one's hands are usually both busy at once, and generally a pilot seldom has a hand free for yanking out a pocket watch. Santos-Dumont took his problem to jeweler Louis Cartier, who devised a simple solution. Ladies had been wearing tiny watches on their wrists for years as jewelry. What Cartier did was to take a small pocketwatch, and affix a leather strap to it so that Santos-Dumont could wear it on his wrist. Then, he could check his watch without ever taking his hands from the controls. Overnight, the multifunction chronometer became the trademark of the aviator. Fashionable gentlemen began to wear them as well, and today the wristwatch is practically ubiquitous.

Today's watches have a few refinements that the originals lacked. Mine, for example, has an E6B flight computer built into the outside dial. It's a circular slide rule you can use to find out how much longer it will take to reach your destination, whether you have enough fuel to make it, and it also has a few built-in unit conversions. It's also useful for figuring tips. I found it curious, though, that wristwatches only became popular in the last hundred years, give or take.

In any case, after Langley, the Wrights, and Santos-Dumont the feasibility of manned heavier-than-air flight had been proven beyond all doubt. Incremental improvements would be made over the next ten years or so, leading to airplanes flying faster and higher, and even capable of carrying a useful load. The next big jumps would take place about ten years down the road, although not necessarily when or where you might expect.