Don't Make Me Open This!

Have you ever wondered what the North Korean Air Force's worst nightmare looked like?

Well, wonder no more!

(Warning: link leads to a rather large picture. Large, but well worth it.)

This one frame contains more heavy iron than most countries have in their entire Navy, and more tactical fighters than most countries have in their entire Air Force. Most of it can be relocated just about anywhere on pretty short notice. And for those who sit on a peninsula surrounded on three sides by ocean ... well, sucks to be you.

If Mr. Kim gets feisty, he'd better make his first shot a damn good one. He won't get a second.

Candygram!

"Zed's dead, baby. Zed's dead." -- Butch Coolidge, 1994

"Soon. It'll be soon. Al-Qaeda's credibility runs out like the sands in an hourglass. Their political capital's spent, their monetary captial, likewise. Their top leaders are on the run, and have to be lucky every day for the rest of their lives. We only have to be lucky once." -- Me, 2005

As it turns out, that's more or less correct: Al-Zarqawi was lucky every day, except for that last bit at the end, when the USAF left a brace of 500-pound greeting cards on his doorstep.

I'll skip the gloating, for the most part. There's a sense in which this changes nothing of substance. While he was a prime instigator, and while there's no obvious successor, the pot of crud that he stirred up is still swirling. Be that as it may, though, there's also a sense in which everything has changed.

Point the first: He was dimed out by someone within his own organization.

This opens up one of two possibilities. One, that someone under him had the thought that he was doing the cause more harm than good, and would be more useful than a dead martyr than as a live (and somewhat less than competent) leader. Or two, that someone under him coveted the top job and decided to let Uncle Sam's Speedy Delivery do the heavy lifting. In either case, serious schisms are evident within the enemy ranks. This is something that alert intel or spec-ops guys could exploit.

Point the second: The first ground troops on the scene were Iraqi.

This is important for a couple of reasons. First, they had enough on the ball to be the first to the party. Second, the overall commanders had enough confidence in them that they wouldn't muff the job. Both speak to the increasing maturity and effectiveness of native Iraqi forces. They've come a long way in the last couple of years.

Point the third: The strike yielded absolute fistfuls of intelligence data.

Whatever Z-Man had with him, we've got. Whatever he was using for contact info, we've got. Did he keep a Rolodex, Dayrunner, little black book? Guys in green suits are reading those even as we speak. Did he keep any kind of financial records with him? They're being analyzed, and the data is being fitted into existing patterns. Were I the new Number One in AQI, I'd be feeling a bit insecure right about now.

Point the fourth (and last): Now, it's all up to the Iraqis.

Now that the new government has been seated, sworn in, and gotten down to business, the ball's in their court. We can't win this. Which isn't the same as saying it can't be won, mind you; but, as of this point, we must transition to a supporting role. The end of this story can't be written in English by an American hand, it must be written in Arabic by an Iraqi. It is still too early to tell if the ending will be happy or tragic. There's still a host of opportunities for failure. But most of the decisions are out of our hands, now. The only decision left us is how much and how far we are willing to support the new government.

But, for better or worse, there's one insurgent who won't see the final outcome. Good riddance!

RIP, Scott Crossfield

Some sad news today. Scott Crossfield died earlier today when his Cessna went down in Georgia.

I must confess to conflicting emotions, here. On the one hand, it's sad to see him go. He was one of the greats. First to Mach 2, first to fly the X-15, a true pioneer of aviation. And he stayed active well into his retirement. But ... you have to know that he'd have hated living long enough to have to hang up his scarf. To a man like that, flying is like breathing.

Vaya con Dios, Mr. Crossfield. It's all VFR from here on out, and not a medical examiner in sight. And if that isn't Heaven, well, what is?

Seven Warning Signs

I found a rather interesting article while reading Jerry Pournelle's site, titled "Seven Warning Signs of Bogus Science".

Mind you, I'm not really a scientist. I'm an engineer by education, and a code monkey by vocation. Ten years of grad school convinced me that I really only know three things for sure: Conservation of Mass, Conservation of Momentum, Conservation of Energy. Everything else is speculation. But ... there's a heck of a lot of utterly bogus "science" going on out there. Someone has got to flange up some sort of BS detector. I tried, once, to do something like that. It ended up being one of those projects that never quite went anywhere.

What I was getting at was this: no one ever really teaches the scientific method anymore. Oh sure, they mention it in passing at some point in most science classes. But they never go much deeper than that. Science is almost always taught as a body of stuff to be memorized, not as a way of thinking.

I have some practical knowledge of why this is the case. It's freaking HARD to get the little buggers to do ANY independent thinking. And a proper treatment of the scientific method is a pretty rigorous exercise in independent thinking.

The problem is, people confuse assertion of "new" facts with actual science. How are they to tell the genuine article from total baloney?

The Seven Warning Signs look to be a great place to start.

I'd add two broad principles to the list, though. They're important enough to deserve that treatment. The two principles are key to the scientific method: Falsification, and Repeatability.

Falsification: We don't know the strength of a steel bar because we've got some magical method for knowing the strength of a crystal lattice. We know the strength of a steel bar because we've bent the damn thing until it broke. Bent it U-shaped, stretched it until it snapped in two, twisted it until it gave way. Do that a few thousand times, and you will know without having to ask whether a given bit of stainless steel alloy will do the job you're asking of it. It's the same with a scientific theory. The accumulated tests that prove it true don't count. It's the tests built specifically to prove the theory false that make or break it. If you can't design such an experiment, there's something wrong with the theory. And, usually, what's wrong with such a theory is that it can't predict anything worth knowing.

Repeatability: You have to be able to describe the experiment completely enough that another experimenter can do what you did, and see the same things you did. If you can't, you probably don't understand what's going on as well as you think you do. If you won't, you've probably got something to hide. For us third-party observers, repeatability is a key thing to watch for. If other researchers are having a hard time reproducing "remarkable" new results ... there might not be anything to report, after all. It's when other people in the field report that they can repeat the experiment successfully that you know something interesting might be going on.

Armed with this information and a healthy dose of skepticism, you'll be better equipped to separate the real deal from the baloney. Now, if we could just get this out to the general public ... But that may be too much to ask.

Space Travel for Dummies: Hands-On Tutorial

--FIRST -PREV NEXT-

For those of you who care to download and configure some software, we can do a bit of a walk-through of a trip into orbit.

[NOTE: There are newer versions of Orbiter and its add-ons available. The new version of Orbiter is available here, and a selection of add-ons are available here.]

First, you want to download Orbiter from here. Orbiter, for those of you who don't know, is a freeware spaceflight simulator. It's fairly realistic, and if you're into that sort of masochism, it can be as realistic as you want it to be.

There are some add-ons we want, from Dan's Orbiter Page. Scroll down a bit, and click on the icons for Orbiter Sound and Delta Glider III. Basic Orbiter has no sound, and sound is a neat thing to have. As for DGIII, well, it has a couple of features the basic Delta Glider lacks. First, you can use the config tool to change up the paint job if you want. Second, and more importantly, it has an auto-pilot function. This makes life so much easier. I can hand-fly an ascent to orbit, but not to an accurate orbit. I can get into space, but if you're relying on me for an accurate rendezvous, you're SOL. With the autopilot, we have a fighting chance.

Now, let's fly.

From the start-up screen, you'll want to select the DeltaGliderIII folder, and Earth Scenery, and from that, the ascent from KSC to ISS. We aren't actually going to attempt a rendezvous, but we'll use that profile as a starting point.

When you get to the cockpit, use the left arrow key to go over to the orbit display. You'll see a grey circle, a green ellipse, and a bunch of numbers down the left-hand side. The grey circle is the Earth's surface, the green ellipse is your trajectory, and the numbers describe various things about your orbit. You won't need any of the numbers for this tutorial, so you don't have to worry about them unless you want to. The pictures on this display tell the story. If you're really interested, I'll have some definitions at the end of the post. One thing you'll want to do, though: punch the key on the upper right side of the panel. It'll change the reference of the display to ship-centered.

Now, hold down the right arrow key to get to the other display. Hit "SEL" to get the list of displays available. Take a look at what's available, but where you eventually want to end up is the Map display. It'll show your ground track, and the ground track of a selected target, if available.

Now that we've got that settled, let's program the autopilot. On your keyboard, type P903S43, then Enter. This loads the ascent autopilot, and then puts it into standby mode. You can activate it by hitting the "E" key. You don't want to do that just yet.

Now, if you hit F8, you get the HUD view. This is the view I like to fly from.

Hitting F1 toggles the external view. From here, you can hold down the right mouse button, and find an external view that you like the looks of. You can also use the scroll button, if you have one, to zoom in and out.

We're done setting up. It's time to light off our engines and get underway.

From the cockpit view, hold down the key and the <+> key on the keypad. Release both keys after full thrust is achieved. Now comes the trickiest part of the whole flight. If you've gotten the sound files in, this will be pretty easy. You'll hear a voice say, "80 knots." Don't do anything yet. Then, he'll say "V1." You still don't want to do anything. But stay on your toes. Shortly after V1, you'll be going fast enough to take off. The cue for that is when he says, "Rotate." The number keypad serves as a joystick. <2> pulls back, <8> pushes forward, <4> and <6> roll left and right. When you get the rotation signal, use <2> to pull back, but not to more than a 20 degree climb. Once you've left ground, tap "G" to raise your landing gear. Then, you can tap "E" to engage the autopilot. Once that's done, you can sit back and enjoy the ride.

This takes us to about T +30 seconds, referring from the time we started our engines.

The autopilot isn't particularly aggressive. It takes about forty seconds to turn to a 43-degree heading, and level the wings. Once it does that, it starts pulling up into a steep climb, a pitch attitude of 65 degrees. It reaches that attitude about two minutes into the flight. Remember, to get into orbit you have to do two things: gain altitude, and gain speed. Generally speaking, you gain altitude first, to get out of the thick, dense air near the surface.

While you're doing this, you'll probably notice that the green ellipse on the left display isn't changing much. Gaining altitude doesn't change that situation very much. Your trajectory is still what we call a degenerate ellipse. If the ground weren't in the way, your path would go straight down to the center of the Earth. This will change in a few minutes, though.

At about T +200 seconds, three minutes and change, the autopilot begins to rein in the climb. You've hit about 100 kilometers in altitude, so you can begin to bend over sideways to build up speed. But you don't do it all at once. It's more efficient to execute a "gravity turn": you turn a slight bit off of your climb, and let gravity pull your path towards the horizontal. It's a neat trick, but it only works if you have little to no air resistance.

But look over at your left-hand display. Now, the orbit begins to fill out. It changes from a degenerate ellipse to a normal ellipse. As you gain speed, you gain energy, and this is expressed as a bigger orbit.

Now, look to your right. The map display shows your ground track mostly in pink. That's the "underground" portion of your trajectory. If you ever try to shoot a Moon landing, that'll come in handy. Where the green trace ends, that's where your path intersects the surface. (If you spend a bit of time learning how to use these displays, there's little to no actual cipherin' involved in flying this thing. Which is a good thing, becuase most rocket jockeys aren't mathematicians.)

At about six minutes into the flight, the autopilot has brought the pitch attitude to zero. It's all about the speed, now. The magic number is about 7,700 meters per second. You're not near that yet, but you're getting closer all the time. The ellipse on the left-hand display is growing visibly.

Now is a good time to do a bit of sight-seeing. Again, F1 toggles between inside and outside views. You can look back at Florida, and south to the Bahamas. The scenery is pretty good.

At about nine minutes, the autopilot will do something that might surprise you at first. You're getting close to your target altitude, so the autopilot pitches down to soak up excess vertical speed. Don't worry about it if that happens. It means you're almost done.

And then, at T +580 seconds, the engines shut down, the autopilot terminates, and you're in a stable circular orbit.

As I've said earlier, this is the easy part. Landing is much, much trickier ...

DEFINITIONS:

Here are some definitions of some of the terms on the Orbit display. I haven't defined all of them, just some of the more important ones.

SMa: Semi-major axis. This is one-half of the total distance, end-to-end, of the long side of the orbital ellipse.

SMi: Semi-minor axis. This is one-half of the total distance of the short side of the orbital ellipse. This is almost never used except to compute the eccentricity.

PeD: Periapsis Distance. The Periapsis is the point of closest approach to the Earth's center. If it's less than the Earth's radius (6,378.137 km) then your trajectory intersects the Earth's surface at some point. If unprepared for said intersection, you're going to have a bad day.

ApD: Apoapsis Distance. The Apoapsis is the highest point on an orbit.

Rad: Radius. This is your current distance from the center of the Earth.

Ecc: Eccentricity. This is a number, 0 to 1, describing how flat your ellipse is. Zero describes a circle, one describes either a degenerate ellipse or a parabola.

T: Total orbital period in seconds. This is how long it will take to go around and come back to your starting point. For a low circular Earth orbit, it's about an hour and a half, give or take.

PeT: Time to periapsis. This is how long you have to go to reach periapsis. It's important for timing orbital maneuvers: if you want to raise your apoapsis, you need to do your burn at periapsis.

ApT: Time to apoapsis. This is how long you have to go to reach apoapsis. It's the same deal: if you want to change your periapsis, you have to do the burn at apoapsis.

Vel: Current velocity. 'Nuff said.

Space Travel for Dummies, Part 4

--FIRST -PREV NEXT-

Now, we come to the really hard part. It's worth mentioning that while nobody has actually ever died IN space, a total of nineteen have cashed in their chips going and coming. Breaking that down, it's seven on the way out, twelve on the way back. It's a very, very tricky thing to do, and it's easy to find yourself well and truly up the river without a paddle.

There's an odd little factoid about the first Space Shuttle mission that I find amusing. Both John Young and Bob Crippen were wired with medical sensors, recording heart rate and other parameters. Crippen, the rookie, recorded his highest heart rate during the launch. He wasn't too excited about re-entry and landing. Young, the veteran, took launch in stride. His pucker factor soared to its heights during re-entry. Obviously, he knew something Crippen didn't.

In short, it's the launch problem in reverse. You need to lose 18,000 MPH of speed and a couple of hundred miles of altitude without getting anything important broken, bent, or burned.

Easy to say, harder to do.

The first part is the easy part: you need to adjust your orbit so that the low part dips back down into the atmosphere. It doesn't take all that much fuel. You tap your maneuvering thrusters for about a minute or so, firing the jets out in front, soaking up a little of your orbital speed. Then, you start to descend. If there were no atmosphere present, your lowest approach would be about fifty miles up. But, there are a few billion air molecules standing in your way...

The basic idea is that you use friction and pressure drag to slow your vehicle down to a more manageable velocity, so that you don't have to use fuel to do the job. The problem is that your vehicle can only stand so much deceleration stress and thermal heating. There's a fairly narrow corridor, expressed as an altitude-versus-speed plot, that you can safely fly in. Too high, and you don't get enough deceleration, and skip back out into space. Too low, and it's a race between thermal stress and G-loading. One of them's gonna kill you, it's just a question of which one gets there first.

It's vitally important to keep control all the way through re-entry. Early ballistic capsules maintained control by putting the ship into a slow roll during re-entry. Kind of like a quarterback's spiral, only slower. More modern versions add active, computer-controlled guidance for extra control. Winged vehicles like the Shuttle can use their aerodynamic control surfaces once the dynamic pressure gets high enough. But if you lose control before you get down below Mach 1, you're in for a whole world of hurt. Vladimir Komarov found this out the hard way on Soyuz 1, when his capsule began spinning too fast. The parachute lines snarled up when they were deployed, and the Soviets were saved the trouble of cremation. They didn't find many pieces bigger than a soda can after the capsule struck the ground.

And then there's Columbia, which gamely tried to fly along missing its left wing for a little bit. A piece of icy foam tore a hole in its heat shield during launch, which let super-hot gases inside to romp and play with the aluminum wing structure during re-entry. It sagged, melted, and eventually let go. Parts were found in six or seven states.

Not that those are the only problems to be had. Soyuz 11 ran into a bit of trouble on its way back from Salyut 1. Russia very nearly scored another first on us. And it must be said, they did have the first space station. We, on the other hand, had the first space station crew who were able to brag about it afterwards. You see, a cabin purge valve had become stuck open during re-entry. It let all of the air out of the capsule, and the crew weren't wearing space suits. The predictable thing happened.

Coming down onto an airless world is just as exciting, but in a different way. Because there's no air, you have to burn enough fuel to do the deed. It's a more predictable process, since you can cipher out beforehand how much gas you need to bring along. They nearly got caught short the first time. Neil Armstrong landed on fumes. But they got better, and more precise, with each successive landing. It's interesting to note that while the computer was in control during most of powered descent, every final approach was flown by hand. No one trusted the guidance well enough that far down. Having had the chance to work with the algorithm, I can't blame them. It has an evil tendency to bend over sideways and burn for the horizon when the time-to-go gets short.

We seem to have lost a bit of the knack, though. The Mars Polar Lander had a senior moment during landing, and cut the engines about a hundred feet off the deck. Back to the drawing board...

Everyone says space is a dangerous place. That's rubbish. Getting there? Dangerous. Coming back? Really dangerous. Being there? Mostly harmless. Well, except for the time the oxygen converter caught fire, or when they rammed themselves with a cargo tug, or when the toilet stopped working... But those are stories for another day.

Space Travel for Dummies, Part 3

-- FIRST -PREV NEXT-

If you've been following along, by now you know the basics of how to get into orbit in the first place, and how to move around in Earth orbit once you get there. Which will do as far as things like going to the space station or putting a new satellite up go, but sometimes you'd like to step a bit further out. It's not all that much different than what we've already been talking about. You know the old saying, "What goes up, must come down?" Well, it's not always true.

If you throw something hard enough, it won't be coming back.

Let's revisit our good friend Superman up on Mount Everest. He still has a few baseballs left, and intends to put them to good use.

If you remember, last time he threw the ball a little harder than he had to in order to achieve a circular orbit, and put it into an elliptical orbit. If he puts more muscle into the throw, he can get it to sail higher and higher into the sky. The orbits get bigger and bigger, and they take longer and longer to get back to their starting point. Starting from 90 minutes, the orbit times extend to two hours, three hours, six hours, and longer. Then, you start measuring the orbits in days, not hours. They blast up to ten, twenty, a hundred thousand miles high. Eventually, he starts going home after he throws, coming back a couple of days later for the catch.

He's got one ball left.

He winds this one waaaaaaaaay back, and lets it go. It leaves his hand at over 36,000 miles per hour. If he weren't Superman, the shock wave would knock him down. Then, he packs up his stuff and goes home. He's done.

This one, you see, isn't coming back to Earth. Ever.

Here's what's happening: Gravity loses strength at the square of the distance from Earth. But, gravity can only drain your speed away at a linear rate. Most of the time, that's enough. It saps all of your vertical speed and pulls you right back. But if you're going fast enough, gravity can't suck speed away quickly enough, and no matter how far away you get you've always got a little speed left over.

So, that last ball Superman threw will sail across the Solar System forever. It's in a permanent Solar orbit, and probably won't ever come back to Earth.

This is an important principle, because that's what lets us leave Earth and strut our funky stuff across the Solar System. While gravity extends everywhere, it's not infinitely powerful, and can be overcome with enough effort. Sometimes, you even get to cheat a little bit and make gravity work for you.

That's the essence of what they call the gravity assist or "slingshot" maneuver. It's a way that you can get a speed boost and direction change for free, if you line everything up just right.

Ordinarily, changing speed and direction takes energy. And the only practical tool we have right now for doing that is a chemical rocket. Which means you have to bring along fuel to do it. Since you have to bring along fuel, you have to bring along fuel tanks, and that drives up the ship's weight.

That's bad. As the current NASA administrator, Mike Griffin, once wrote: "Spacecraft, like turkeys, are bought by the pound."

But, sometimes, you get to pull one over on Mother Nature. Here's how it works:

Imagine a skater, carrying a grapnel hook on a bungie line. He wants to round the corner, but doesn't want to expend the effort to turn his skates. So, he throws out his line, hooks a pole, and swings around.

By timing your approach and direction just right, you can swing around a planet just like the skater swung around the light pole.

As you fall in, coming from behind and below, you speed up as the planet pulls you in. As you speed away, the planet's gravity isn't able to suck your speed away quickly enough to get it all back. Basically, you've stolen a tiny bit of the planet's orbital momentum, and used it to speed up and change the direction of your orbit.

We've gotten pretty good at this. Voyager, Galileo, Cassini, all of them went through numerous slingshot encounters to achieve their missions.

And that's about it for basic orbital maneuvers. Once you escape Earth orbit, getting to and from another planet in the Solar System works just the same as getting to and from something in Earth orbit. You burn in the direction of travel to gain energy and go farther out, and you burn against the direction of travel to lose energy and go in.

Which brings us to a trick question. Remember this: you can amaze your friends at parties, because almost no one ever gets the right answer the first time.

Here's the problem: you've got a package of dangerous waste that you want to be rid of forever. You've got two options. One, drop it into the Sun, and two, send it into interstellar space.

Which one is easier?

Sending it into interstellar space, of course.

This stunned me the first time I heard it, but the numbers absolutely work out.

Earth's orbital velocity is about 30 kilometers per second. As a rule of thumb, escape velocity is about one and a half times orbital velocity. So, once you've escaped Earth, you have to gain about another 15 km/sec to achieve Solar escape velocity.

But to drop something straight down, you have to shed ALL of your orbital velocity. So, to drop something into the Sun means you have to find a way to shed a full 30 km/sec.

It's a hard fact to swallow, but I assure you, it's true.

Next time: How the heck to we get back home?

Space Travel for Dummies, Part 2

-- FIRST -PREV NEXT-

"East takes you out. Out takes you west. West takes you in. In takes you east."
-- Larry Niven, The Integral Trees


Once the main engines shut down, things get quiet. Not completely quiet. That would be bad. There's a constant hum and rattle of pumps pumping and motors whirring, but if that ever stops, breathing is liable to become just a little bit difficult. But the rumble of the main engines has stopped, which means that you've reached a stable orbit.

Now what?

Last time we took a look at how you get into orbit in the first place. Now, we're going to look at what you can do once you get there. It's not enough just to get into space. You need to know how to get around, so that you can go where you want to go, not just bore holes in the sky.

Let's rejoin Superman back on Mount Everest, where he just caught a baseball that he threw all the way around the world. What do you think would happen if he threw it just a little bit harder? There's only one way to find out ... He pulls another ball back, this one farther still, and lets it rip. Just like the other ball, it never touches the ground, but unlike the other ball, its path takes it not on a level path around the world, but slightly upwards. By the time it reaches Brazil, it's several miles higher than the first ball's path. But, it starts to fall closer to Earth after that. About two hours later, Superman catches it when it comes back.

Now, what's going on, here? In a word, it's all about energy. Neglecting atmospheric friction, the energy of an object in orbit is constant. If we start with an object in low Earth orbit, and give it just a slight kick so that it goes a little faster, its orbit is no longer a circle, it's an ellipse. The low point on the ellipse touches the original circular orbit. The high point on the ellipse sticks out just a little bit.

Consider the opening quote from The Integral Trees. It's a pretty good description of how basic orbital maneuvering works. Going East -- adding speed to your trajectory -- takes you Out -- farther away from Earth. Going Out takes you West -- as you climb up, you trade speed for altitude, and end up going a bit slower. If you left another spaceship back in your original orbit, if you look down, you'll see it pass under you. Going West -- taking speed away from your trajectory -- takes you In, or closer to Earth. This works the opposite way: you take a little bit of energy away from your orbit, and start to lose altitude. But now you're trading altitude for speed, and you'll pass anything you left in your original orbit. Which brings us -- you guessed it -- to the last bit: "In takes you East."

These facts are the foundation of the art of orbital rendezvous. You don't catch up to another spaceship by burning your engines constantly until you match position. No, what you do is enter a higher or lower orbit, and wait. At just the right time, you make an orbital adjustment burn, and match trajectory with your target. The actual math is a lot more complicated than that, but that's the general idea. You spend most of your time in space waiting for the right time to make these maneuvers.

The other thing is, you're not always in the same orbital plane as the spaceship you want to dock with. The way you want to handle this is to make sure you launch into the right orbital plane to begin with. That's why you hear about "launch windows" all the time. It's possible to change your orbital plane once you get into space, but plane change maneuvers drink fuel like nobody's business. You never want to do one unless you have to. It's always easier to make sure you get the plane right the first time around. But if you do have to, the way you change the plane of your orbit is that you fire your rocket at right angles to your current direction of travel. That is, instead of firing ahead or behind, you fire your rocket sideways.

In any case, now that we've gotten ourselves into space, we know how to move around and get where we want. Next time, we'll talk about going a little farther out: to the Moon, and beyond.

Fear and Loathing at Wal-Mart

There's been a trend afoot at major retailers for quite some time now, and it really torques me off.

I really, really hate being treated like a crook.

At first it was the CDs. I don't think there was ever a time when they weren't packaged in such a way as to prevent use by their legitimate owners. That, at least, has gotten a bit better. Back in the day they used this industrial-strength Kryptonite stick-um that would never, ever come off the case. These days at least you can get the goo off. But it still takes two or three minutes of dedicated, painstaking effort to open the damned thing. All because the retailers are convinced that everyone entering their store is just aching to exercise a bit of five-finger discount.

Buy a clue, dolts. Not everyone is a thief.

The latest offense was, I suppose, at least partly my fault. Naive rube that I am, I dropped $20 on a new watch at Wally World without bringing along my Gerber Multi-Plier, acetylene torch, and other assorted cutting tools.

I remember a time when you could buy a watch, take it out of the box, and you were done. Not so. No, now the damned thing is secured to its packaging with not one, not two, but THREE nylon straps. Nosiree, no one's walking away with one of these babies without a fight!

But what of the poor consumer who just wants a way not to be late for something important? There's nothing for it but to use your teeth and car keys in ways that neither God nor General Motors really intended.

Now, I don't object to a bit of active loss prevention here and there. They've got a right to get their fair due for their merchandise, and I've known one or two people in my time who'd steal for sport, to say nothing of necessity. But surely, in the modern day, there are less offensive ways of doing it? Some way that won't actively diminish my enjoyment of the product?

In my more optimistic moments, I envision a day when store security can rely on RFID tags on all their merchandise. If you try to walk off with something, it'll cry out for help all by itself. You won't have to watch the merchandise. It'll watch itself.

In my more pessimistic moments, though, I imagine that the damned sadists LIKE doing this to me. They ENJOY your pain. "Welcome to Wal-Mart, shopper. This head-vise is a preventive security measure that we only extend to our most valued customers." "Oh, that boot to the groin was just a courtesy detail." "Molten sand enema? Anyone?"

On-line shopping looks better and better all the time. At least that way, I can be sure to have all my tools at hand when I have to open the damned box.

Space Travel for Dummies, Part 1

--FIRST -PREV NEXT-

For years now, I've threatened to write a book on space travel, but have never made the time to do the deed. There's a niche to be had, for a book somewhere between kids' picture-books and professional-level textbooks. I have a couple dozen pages of notes, somewhere. Provided that they haven't been thrown away in a cleaning binge.

Anyhow, it probably ain't gonna happen. So, I'm going to do the next best thing. I'll collect those thoughts here, in a series of posts. I'm not sure how many posts it'll be.

First off, let's talk about falling. Not just any kind of falling. This is falling with panache, daring, and style. Any fool can fall and hit the ground, but it takes great skill to fall ... and miss.

Imagine, if you will, Superman standing on the summit of Mount Everest with a pile of baseballs. Let's say that he picks one up and throws it. It flies eastward a bit, before smacking into the peak next door. He decides that was a pitiful effort, picks up another, and heaves it a bit harder. It flies over the next mountain, and lands somewhere in eastern Nepal. We can't see it from where we stand. It's gone a bit around the curve of the Earth. Still not satisfied, he picks up another ball and throws it with more force. This time, it plinks into the Pacific, somewhere north of the Phillippines. He keeps repeating the process, dunking the next ball off the cost of Ecuador, and then skipping it across the ground somewhere in Brazil. Then, at last, he pulls one back and lets it go ... and it never quite touches the ground. It screams through the sky, twenty-five times faster than sound, always falling but never hitting anything, until, about 90 minutes later, Supes turns around, and THWACK! He neatly traps it in his catcher's mitt.

That, ladies and gentlemen, is called an orbit.

It doesn't matter what's doing the orbiting, or what it's shaped like. It could be a baseball, a '57 Buick, an Orange Julius stand, or the Eiffel Tower. If you can drag it a couple hundred miles straight up, then set it moving sideways at 18,000 miles per hour, it will circle the Earth indefinitely.

The other thing to notice is that the Earth's gravity is still in full force. There's no such thing as Zero-G in Earth orbit. We sometimes use the word, but it's sloppy. Better to say "free-fall", because that's what's really happening. Something that's in orbit around the Earth is falling all the time. But it's going so fast, that the ground curves away before it can hit. Yes, it is possible to fall and miss the ground. All you need to pull that trick off is a bit of speed.

The next question is, how do you do it?

Well, remember, there are two things you have to do. First, you have to lift it up outside of Earth's atmosphere. Second, you have to accelerate it to orbital speed. It's pretty tough to do both at the same time. It's incredibly tough to try to do it with only one set of engines.

It ought to be fairly obvious that the "lift" job needs a really powerful, high-thrust engine. It's not as obvious what the "accelerate" job needs. For that, we'll have to look at two equations:

[1] V2 - V1 = Ve * EXP (M1/M2)

V2 and V1 are the final and initial speeds, respectively. Ve is the exhaust speed of the rocket, and M1 and M2 are the initial and final weights of the rocket. The other equation is:

[2] P = Ve * T

P is the power produced by the rocket engine, and T is the thrust.

Now, here's the sad and sorry fact: for chemical rocket engines, P is pretty much fixed. Energetic chemical reactions all produce about the same power level. There's not a whole lot of difference there. Where they are different is in how fast the exhaust moves. An engine with fast-moving exhaust gives us a better top speed. We see that from [1] above. But, looking at [2], we see that when Ve is big, and P is fixed, then T has to be smaller. Going the other way, if we want lots of T, we have to live with less Ve, and not as much speed.

But, because we have two different jobs to do, we need both kinds. Look at the Shuttle, for example. The solid rocket boosters aren't too terribly efficient, but they're absolutely swimming in thrust. When they light off, the Shuttle leaps off the pad with force and authority; as long as those SRBs are burning, you're going somewhere. When they're done, the Shuttle's main engines take over. They're not super-powerful, but they're about as efficient as chemical rockets get. Now that the heavy lifting's done, they can bend over sideways and start building up some speed.

Just about every modern rocket system uses the same scheme. The Ariane 5 uses parallel staging like the Shuttle, with solid boosters flanking a hydrogen/oxygen core stage. Others, like Russia's Soyuz rockets, use clusters of kerosene rockets to do the lifting, before handing over to a more efficient upper stage for orbital insertion. There was a proposal in the '50s to use balloons to take a rocket up out of the dense layers of the atmosphere, and shoot it into space from there. It was never tried, so far as I know. It wasn't a bad idea, and might have worked. Other proposals use a large 747-type plane as a mother ship, carrying a rocket plane piggy-back to 40,000 feet or so, before the rocket plane separates and flies into space. Also not a bad idea, but there are some kinks to work out.

That will do for an introduction. Next time, we'll figure out how to get around in space once we actually get there.