FTL Flavors: Summary

This is the sixth and final installment of my series on the different flavors of FTL. We’ve warped through hyperspace and jumped through wormholes… or something like that. To clear it up, here’s a summary table showing how these various flavors stack up on the criteria I used:


Clearly, that’s a simplification of several simplifications, but in reducing the various drive features to simple yes/no pairs, it highlights a couple of things. First, not all of the options are represented. What if you took something like warp drive and changed the FTL-FTL box to no? What would that look like if FTL ships could no longer interact? Is it that they cannot see each other? Or maybe they only see each other long after they’ve passed? Maybe they have FTL drives but not FTL sensors?

For another example, what if we put a “yes” in the FTL-Navigation box for wormholes? Maybe instead of simple point-to-point tubes, we’re actually cruising through a complex network of junctions and connectors. Maybe our expected Sol-to-Rigel trip is merely the result of taking all the default options at every junction? What if we could alter course at key junction points and end up somewhere entirely different? What if that kind of exploration can only be done by trial and fatal error?

The second thing I notice with such a table reduction is that there are very different ways to expand these choices into the story mechanics of the drive system. Consider that wormholes and jump drives have almost identical table entries, i.e. Rarely or No across most of the table. Yet these two FTL systems have very different feels to their stories.

Similarly, even staying within a single system can give you FTL drives that end up looking quite different in the actual stories. Consider warp drive. We’re all familiar with how it works in Star Trek. We tear across the universe, warping space and manipulating subspace fields and so on. In my space opera universe of the Hudson Confederacy, ships are using tachyon drives, essentially throwing up ephemeral sails to catch the tachyon wind and yank them up to FTL speeds. The mechanism looks completely different, yet functionally, my tachyon sails are just another warp drive. But my navigators don’t worry about subspace interference. Instead, they worry about shifting winds and tachyon storms.

Furthermore, it’s also an over-simplification to think that a story must use only one flavor of FTL. Many combine them. For example, the Honor Harrington series by David Weber uses a mix of hyperspace and wormholes. That is, while most travel occurs via hyperspace, one planetary system hosts the intersection point of several long-distance wormholes, giving them a huge strategic advantage both for shipping and war. Similarly, some of the later Star Trek series (TNG, DS9, and Voyager) added rare wormholes on top of their trusty warp drive fleet.

So, did I skip a flavor? Probably. There’s a lot of SF out there. Some of those FTL systems may indeed be fundamentally different, but I suspect that a lot of them will boil down to being one of these four with different names and different hand-waving for the so-called science.

But the most important thing for all of them is to get your characters from here to there before they grow old and die. And once there, they can try to write a letter home, which brings up the matter of FTL communication, but that’s a subject for some future series of articles. With luck, I’ll get to that before we reach Sirius.

The whole series: Intro, Warp Drive, Hyperspace, Wormholes, Jumping, Summary

FTL Flavors: Jumping

shipjumpingThis is the fifth installment in my series on the different flavors of FTL, and this week we’re jumping into… well, jumps. A jump is essentially teleportation over interstellar distances. You set your destination coordinates, hit the switch, and then you’re at the destination. In some stories, these jumps are instantaneous. In others, the jump takes time while you exist in some transitory null-space. That second variation might sound a lot like hyperspace, but the distinction between jumps and hyperspace are in the details.

One thing about jumping, though, is that the terminology is much sloppier than for other flavors. For example, the Dune universe used jumping, though they didn’t call it that. It was “folding space”, but it was functionally the same kind of interstellar teleportation that I’m describing here. Star Wars muddies the water further by talking about “jumping through hyperspace”, making it unclear which of the two flavors they’re using. This flavor is the furthest from known physics, so it’s understandable that it has the most hand-waving and distracting terms.

FTL-to-FTL Interactions: There are none. If the jump is instant, there is simply no time, but if even it takes a few days or weeks, the ship is not in any kind of recognizable space. You can’t see other ships, so you can’t interact with them.

FTL-to-sublight interactions: There are none. Again, if it’s instantaneous, there’s no time for such interactions, and even if it takes time, your ship is completely cut off from the rest of Einsteinian space.

Relativistic effects: If the jump is instant, there are one. If it takes time, I have typically seen it take the same amount of time on ship as it did in regular space. However, I don’t see this time match-up as a hard rule for this flavor of FTL.

In-FTL Navigation: There is none. All of your navigation choices were set before the jump. After that, you are simply waiting to land. This is probably the biggest distinction between jumps and the hyperspace flavor. Hyperspace typically allows at least some kind of in-FTL navigation, even if it’s merely to stop short and drop back to normal space.

Speed Differential: Yes, there can be speed differences but not in the normal sense. After all, my instant jump cannot be any faster than your instant jump, but it is possible for my jump to be of a greater distance than yours. I jumped to Sirius in one jump, but you require four shorter jumps. That speed differential is a fairly common one in both fiction and space-based RPGs.

Another speed differential with jumping can be in the time it takes to figure out all those jump coordinates. This is less about the drive itself and more about navigational sensors and computation power, but it still impacts the overall speed of a series of jumps strung together. Similarly, it can take time to refuel or recharge the jump drives. So, not only do these jump delays allow two similarly-rated ships to have different overall speeds, but they further penalize any ship that has to do a series of shorter jumps.

Furthermore, jump accuracy makes a big difference in the final planet-to-planet travel times. Does your jump drop you out at the edge of the star system? In the neighborhood of the planet? Or can you plop yourself down in the atmosphere on a landing path to the starport? The further out you are, the longer you’ll spend travelling at sublight speeds to finish off the journey. Similarly, some jump systems don’t work well in gravitational fields, so it’s necessary to travel a ways out before making your jump in the first place. Put those together, and drive accuracy and stability can add days or weeks to your journey.

Now, for those jumps that actually do take time, we get into speed differences that are much more familiar. How long does a jump take? Is it the same for all jumps? Does it get longer the further you go? Maybe some ships can jump five light years in a day while others take a week. This kind of variation is fairly rare in stories I’ve seen, but I would not say it’s disallowed by the general flavor of jumps. It’s just another tweak.

Malfunctions: These tend to be either errors of navigation or fatal disasters. Sloppy navigation could be from miscalculating those jump coordinates, but they could just as easily come from some mechanical failure in the jump drive itself. I can see the jump-drive equivalent of Scotty shouting to the bridge, “Aye, her core filters are as twisted as the Admiral’s knickers!” Still, the worst that has happened is that you ended up somewhere other than where you meant to land, and space is 99.999… some more 9’s … 99% empty space. Very likely, you won’t have landed inside anything nasty.

ShipGoBoomOn the other hand, if “her core filters” are as twisted as Scotty says, they might just blow up when you hit the switch, especially if you’re too close to a planet, moving too fast, or anything else that makes a jump tricky. Who knows what would cause it, but when enough energy to teleport the ship five or ten light years goes awry, it’s not a healthy place to be.

And finally, there’s the possibility of jumping but never landing. These ships get lost in that transitory null-space, and we never hear from them again. Or do we? I’ve seen a few tales of the Flying Dutchman’s space cousin, and even one where they managed to recover them.

Special traits: A common feature I’ve see with jump drives is that they are reserved for larger ships, not little one-man fighters. This isn’t universal, but it’s common enough to note. Another feature I’ve seen crop up is the idea of jump points, i.e. fixed points in space where the local conditions are ideal for a jump. Those fixed points can add to the fun of space opera because they make space suddenly small again. The star system might be billions of kilometers across, but there are only four usable jump points. If you’re defending against an invasion or hunting unsuspecting merchants, those are the places you want to stake out.

That’s the end of the flavors. Tune in next week for a recap, some comparisons, and ideas that could point to as-yet-unsampled flavors.

The whole series: Intro, Warp Drive, Hyperspace, Wormholes, Jumping, Summary

FTL Flavors: Wormholes

artsywormholeThis is the fourth in my series on various flavors of Faster Than Light (FTL) travel, and today I’m dropping into wormholes. The basic idea of a wormhole is that it’s a shortcut between two points. Usually they are fixed points, but there’s some variation on that. Sometimes they are done as predefined shortcuts through some alternate parallel space, and other times they are special tunnels through our own space.

In most cases, they are fairly permanent and independent of the ships traversing them. Thus, ships that have only sublight capabilities are now about to cross vast interstellar distances just by popping through these wormholes, just like a pedestrian can cross town quickly by taking the subway.

FTL-to-FTL interactions: These are almost nonexistent. The only interactions you might have are with other ships (or beings) that are in the same wormhole with you. Plus, wormhole trips are usually presented as being fairly short, so the opportunities for interaction would be fleeting.

FTL-to-sublight interactions: There are none. At least, that’s how I typically see it done. The wormhole is completely cut off from the rest of the universe. At best, there might be some communication with stations near either end of the wormhole.

Relativistic effects: Typically, there are none. Sometimes the transits are essentially instant, like walking through a doorway. Other times, they last seconds to hours, but it’s generally presented as time flowing tick by tick along with a stationary timeframe.

However, I know of one wormhole setup where the wormhole is a tubular region of space where time flows thousands of times faster than normal, thus making the speed of light in that region thousands of times faster. Ships passing through this make up for the time-scale by travelling at relativistic speeds, thus slowing their internal time by a similar factor to the external speed increase. Thus, they make a multi-year journey in a few minutes according to their own clocks and quite possibly a few minutes according to our clocks as well. In that setup, however, there is no guarantee of an absolute matchup between the ship clocks and the stationary clocks, so there would be some variation from one wormhole to another, and sometimes even from one trip to another on the same wormhole.

In-FTL Navigation: Nope, sorry. You don’t get to steer the train. You can’t even pull the emergency brake. And no hopping out the back either. You stay on it until it dumps you out the other end. Do not pass Rigel. Do not collect two hundred quatloos. Your best bet is to hope that there are other wormholes near the end of this one so that you can exercise at least a little choice.

Speed Differential: In all the wormhole systems I’ve seen, the ships within the wormhole all travelled through it at the same speed. Or if there was any speed variation, it was not under the control of the ships themselves. They were merely being swept along by currents of different speed. Of course, there’s no guarantee that all wormholes move you along at the same speed.

Malfunctions: All the breakdowns I’ve seen with wormholes have been with the wormholes themselves. Either they collapsed or became untethered at one end. Typically, the worst that happens to you is that you’re stuck at the wrong end of a wormhole. Then again, I’d hate to be inside one when it collapsed.

Special traits: Wormholes have several interesting traits in the story-telling sense. The first is that they are often pre-existing objects outside the control of the characters using them. Maybe they’re naturally occurring phenomena, or maybe they were built by “the ancients”. Or maybe, like the subways, they were built by the government, and we peons have to live with them as they are. They key here is that it’s no longer a space travel system where we get to pick out our destination and sail on through the night. Instead, there are a handful of destinations to pick from, and if that’s not where we want to go, that’s just too bad.

The second interesting thing about wormholes is what they do to the Euclidean topology of space. I’m not referring to some freaky space warping around the wormhole entrance. Rather, I mean that Rigel is now 500 million kilometers away rather than 900 light years, because there’s a wormhole to take us there. Meanwhile, our next door neighbor Proxima is still 4.24 light years away because it has no wormhole. Yet another nearby star Sirius is now only 2.1 billion kilometers away (rather than 8.6 light years) because we can get to it via a series of wormholes, i.e. first Rigel, then to Polaris, Antares, Deneb, and finally Sirius. (Don’t get lost at Deneb – it’s a bad neighborhood.)

And finally, if the wormholes are not strictly ignorant carriers of traffic, but instead, intelligent agents of control, then those first two factors can make for some very interesting situations. Imagine being able to control all commerce, traffic, even information flow between these distant stellar islands, simply by deciding which ships will complete their journey, which worlds to cut off, or which radio transmissions to shunt aside. Now start thinking about it from the point of view of we peons not realizing that the wormholes are under intelligent control, and let your space-opera paranoia turn all the way up to Eleven.

technicalwormholeBut one last bit on wormholes. Like the warp drive, these might be possible if not actually feasible. What we call a wormhole is remarkably similar to a prediction of General Relativity, known more properly as a Einstein-Rosen Bridge. However, since our best theoretical examples of such wormholes are tied up with black holes, this still has a long way to go to before we can turn it into the green-line express from Sol to Rigel.

Tune in next week when we go Jumping.

The whole series: Intro, Warp Drive, Hyperspace, Wormholes, Jumping, Summary

FTL Flavors: Hyperspace

hyperspaceThis is the third in my series on different flavors of Faster Than Light (FTL) travel, and today I’m taking a look at hyperspace. The general idea here is that there is a separate space, parallel to our own, that allows for shorter travel between two points. It’s no longer four light years to Proxima. Instead, you transition over to hyperspace, travel a hundred thousand kilometers, and drop back into normal space at Proxima.

Generally, hyperspace is considered to be as Euclidean as normal space (which is not always truly Euclidean) and is scaled linearly with normal space. That’s the $5 way of saying that if you go twice as far in hypespace, you’ll go twice as far in normal space and in the direction you would have expected.

gateThe only tricky thing about hyperspace is getting between normal space and hyperspace. In some stories, your ship can contain the necessary equipment to open a transition point. In other tales, it requires a gate in normal space to open that transition point. But once you’re over in hyperspace, it’s just a matter of throttling up or sailing away.

Let’s see how the details break out.

FTL-to-FTL interactions: This varies. In some stories, hyperspace is a chaotic or void space that is completely incomprehensible, so you cannot interact with other ships even if they were supposed to be flying formation with you. In other tales, hyperspace is pretty much just like normal space but with better graphics. In those cases, you can fly around, talk to other ships, and even shoot at them. Of course, there’s room to play around between those two extremes such as limiting communication range due to “hyperspace flux” or the likes.

FTL-to-sublight interactions: Usually there are no interactions here. You are in a truly separate space. At best there is a level of communication, but that is typically done via fixed points like gates. However, I have seen a couple of odd exceptions to this rule, typically where something unusual in normal space (such as a supernova or black hole) will cause a disturbance in hyperspace.

Relativistic effects: Generally there are none. The ships aren’t typically travelling very fast in hyperspace. It’s just that the distance there is shorter. Either that, or there is simply no special relativity in hyperspace. However, I have seen an odd time variation in some of C.J. Cherryh’s stories where mental processes continue on at a normal pace while other biological processes slow down. This allows frequent travelers to have a mental age of 40 while still appearing to be only 30.

In-FTL Navigation: This can vary, but there is almost always some. At the very least, ships travelling through hyperspace have the option of dropping back to normal space early, short of their destination. Course changes might require such a transition back to normal space, but there is that option. However, in most cases, hyperspace seems to allow as much navigational flexibility as the warp drive, complete with screeching turns and barrel rolls. Still, one limitation on this is the fixed points of gates. If you can only transition via the gates, then all the zigs and zags of your pilot won’t change the fact that you really only have a handful of destinations.

Speed Differential: Again, there typically is speed differential in hyperspace, typically achieved simply by travelling faster or slower within hyperspace. Sometimes, though, I have seen it done with multiple parallel spaces with different speed limits with them, e.g. hyperspace-A allows an effective 10-to-1 speed boost, while hyperspace-B gives 1000-to-1. However, I have seen a few cases (notably most of Jack McDevitt’s Omega Cloud series) where all ships travel through hyperspace at the same rate, since that is believed to be a fundamental property of hyperspace.

Malfunctions: These can suck. The most common malfunction is with your ability to transition to and from hyperspace. If you end up stuck in normal space, you’re just like the folks with the busted warp-drive, sticking your thumbs out in hopes of rescue. Except, of course, if you’re out in the middle of interstellar space, there won’t be any warp-drive ships careening past to see you. Instead, they’ll all be passing by unseen in hyperspace. Even worse is when you get stuck in hyperspace. Unless you can get to a gate to transition back, you’re left to the mercy of whatever monsters the author has left lurking in the dark corners of this alternate reality. Most often, those ships will simply disappear like the sailing ships of old, leaving only grieving widows and frustrated insurance adjusters.

Special traits: This is a nice dodge around relativity’s limits that doesn’t require much hand-waving with dubious physics. About the only big decision to make is whether or not ships can generate their own transition points or if some or all of them require a system of gates.

Tune in next week for a look at wormholes.

The whole series: Intro, Warp Drive, Hyperspace, Wormholes, Jumping, Summary

FTL Flavors: Warp Drive

This is the second in my series on the different flavors of Faster Than Light (FTL) travel, and today I’ll be looking at the warp drive. The ideas for warp drive predate Star Trek, and they weren’t always called by that name, but Captain Kirk and the Enterprise are the iconic example of the warp drive. With a few words of technobabble, the universal speed limit is suddenly gone.

Yes, they paid lip service with the distinction between impulse drives and the warp drive, and over the years, they’ve filled our heads with all the technical details of subspace fields, warp bubbles, and such, but the basic result is that we are no longer bound by the upper limit of lightspeed. Let’s look at how some of the details shake out.

FTL-to-FTL interactions: Two ships travelling at warp speed can interact. That seems pretty universal. They can travel together, see each other coming, even take pot shots as they fly past. Sometimes there are a few restrictions, but they’re usually more of the nature of “that’s never been attempted at this speed!” In other words, they’re dramatic challenges for the engineer, not fundamental limitations on the physics.

FTL-to-sublight interactions: Yes, you can see the planet coming, and it can see you. You can steer around it and come back in for a strafing run. Stories with warp drive usually ignore the fact that you can’t literally see something coming at you faster than light with vague talk of “long-range sensors”.

Relativistic effects: Warp drives almost never deal with relativity. I think a lot of this is that once having dispensed with Einstein’s limits, they would rather not bring up real physics again. However, I have seen one or two instances of mild relativistic effects with warp drives. Kube-McDowell’s Trigon Disunity trilogy had a drive that ultimately moved the ship faster than light via some tricks of warped space, but the occupants were also travelling at relativistic speeds within that warped space. Thus, they experienced less than half the elapsed time as their Earthbound friends.

In-FTL Navigation: Warp-drive ships generally have no problem turning to starboard at faster than light speeds. Since we’re now pretending there’s nothing special about the speed of light and imagining ourselves in space-going navy vessels, there is no reason to suspect otherwise.

Speed Differential: Yes, the Joneses have a faster warp drive than you do. After all, if there is no longer an upper limit on speed, someone is always going to be at least little faster than you. Of course, since speed variation is possible, this also means you don’t have to be traveling at your maximum speed all the time. You can save warp 9 for the really dramatic moments.

Malfunctions: Whether it’s something as minor as a crack in the dilithium crystals or an ejected warp core, you’re not necessarily dead when things go wrong with your warp drive. Most of the time, you’re simply restricted to sublight travel again as Einstein takes a brief rest from spinning in his grave. Of course, many faults can be repaired, and you can get moving again. Failing that, you just have to stick out your warp thumb and wait for rescue.

Special traits: For storytelling, this is probably the easiest and to write and the simplest to grasp. It essentially ignores relativity and removes the problem of interstellar distances from the story. Rigel-4 is no longer hundreds of light-years away. It’s merely on the other side of the pond, so climb aboard the newest ship from the White Star Lines and have a safe… er… at least a short voyage.

alb-warp-driveBut ironically, this flagrant slap in the face to physics is starting to look like it just might, maybe, theoretically be almost possible. In 1994, Miguel Alcubierre proposed a way of changing the shape of space around us, shrinking it in the direction we wanted to travel and expanding it in the direction behind us. It requires some pretty crazy technology, the science for which is still pure speculation, but after about twenty years, it has a few people seriously considering it as a matter for research. How seriously? Apparently NASA is spending some of its precious half-pennies on it. It might not be much more than a publicity stunt, but there’s always that outside chance that it might be something huge.

So, tune in next week when we take a tour of hyperspace…

The whole series: Intro, Warp Drive, Hyperspace, Wormholes, Jumping, Summary

FTL Flavors

I don’t know which came first, the fictional accomplishment of travelling faster than light or Einstein’s prohibition against it, but one thing is certain, fictional FTL travel is here to stay. The genre of space opera almost requires it, and it has become a convenient cheat for telling stories over vast distances while still keeping them within our grasp.

This is the first of a six part series on the various flavors of FTL travel. Specifically, I’ll be breaking down the various forms of FTL travel and looking at how they work. I won’t be digging into the technobabble of fictional engineering manuals. Instead, I’ll be taking a look at how they work it story terms, i.e. what they allow, what problems they present, and so on.

Specifically, I’ll be examining each of them under these criteria:

Does it allow for FTL-to-FTL interactions? When you’re on your way from Earth to Rigel-4, can you run into another ship? Can you talk with them? Can you get into a fight with them? Or does this particular brand of FTL prevent those FTL ships from passing in the night?

Does it allow for FTL-to-sublight interactions? This is similar to but distinct from the first question. If you pass some planet along the way, can you see it? Can you make an FTL strafing run against some unsuspecting target? Or can they somehow see you coming?

Do you still have any relativistic effects? We might be mooning Einstein as we blow past at warp 5, but it might be possible to have some strange time dilation effects in place. Maybe you still age a little slower? Or faster? Or is it random?

Does it allow for in-FTL navigation? Do you set your destination and then trust to luck, or are you keeping one hand on the wheel at all times? If you find out that you’ve made a wrong turn, can you fix it, or do you simply have to wait until you get to other side?

Is all FTL the same speed? Does this particular FTL allow for some ships to be faster than others? Can you chase someone and catch up? Can you outdistance your pursuer? Or are we all on the same train?

What goes wrong? No mode of travel is without the occasional flat tire or torn wing. When your FTL engine breaks, what is the fallout? Are you left in space sticking your thumb out, hoping for a ride, or did you disappear into an alternate dimension, never to be heard from again? Or do things simply go boom?

And finally, is there anything that makes this particularly special? What makes it distinct from all the other go-go-go gadgets in the spacelanes? Is it man-made, a natural phenomena, or a gift from the ancients?

So, I hope you’ll tune in over the coming few weeks as I pop the hood on various starships and take a look at the story mechanics inside.

The whole series: Intro, Warp Drive, Hyperspace, Wormholes, Jumping, Summary

Space Elevator Misconception

BasicElevatorYou’ve heard of space elevators, right? You know, it’s that cable that hangs down to Earth from geostationary orbit and stretches out another 35,786 kilometers past that to balance it all out. Down here on Earth, we’re experiencing one Earth gravity, 9.8 m/s2, aka “1 g”. And up at the center, in geostationary orbit, we’re weightless. And at the far end, we’re experiencing full Earth gravity again, only pointed outwards due to centripetal force, right?


I’ve seen this crop up in a few SF stories involving space elevators, and it seems so natural that I assumed they were correct. It makes sense, after all. The bottom is being pulled down at one Earth gravity. To balance out, the other end also has to be getting pulled up at one Earth gravity. It makes sense, but it’s wrong.

Why? The key is that Earth’s gravity is stronger at the surface than in the increasingly higher orbital altitudes. Somewhere in the back of your head, you’re starting to remember something called the Inverse Square Law, aren’t you? That’s right. Like many physical phenomena, their effects decreases with the square of the distance. If you’re twice as far away, you only feel one fourth the effect.

What does that mean for our space elevator? It means that at its center, we are not balancing 1 g of gravity with 1 g of centripetal force. Rather, we’re balancing the decreased gravity from the distant Earth with an equivalent amount of centripetal force. How much gravity is there at that distance? Let’s do the math.

The formula for gravity at a distance is:

g = GM / r2

… where G is the gravitational constant, M is the mass of the body (i.e. Earth), and r is the radius of the orbit. The value of the product GM is known to high precision at 398,600.4418 km3/s2, and the geostationary orbit radius is 42,164km — 6300 of which are between the Earth’s center and surface. So at that altitude, the gravitational attraction of the earth is 0.224 m/s2, or a mere 2.28% of the gravity we experience on the surface of the Earth at the base of the space elevator.

But what does that say about the centripetal force we experience out at the far end? Well, centripetal acceleration is defined by the formula

a = w2 * r

…where w is the angular velocity in radians per second, and r is the radius of the circle we’re turning in. Since we’re still staying over the same point on earth, the angular velocity is (2 * pi) per day or roughly 0.0000729 radians per second, and our radius is about 77,950km, i.e. twice the geostationary altitude plus the radius of the Earth itself. And being swung around at that far-flung distance will net us a grand total centripetal acceleration of… 0.41 m/s2.

But we’re not quite done, because even though we’re being flung around, we’re still feeling some gravity pulling us back to the Earth. At that distance, it’s only 0.065 m/s2, but that does drop us down to 0.35 m/s2, or a mere 3.6% the surface gravity of the Earth.

You thought the Apollo astronauts looked bouncy on the Moon? They were over four and a half times heavier than they would be at the end of the elevator’s cable. It’s enough to keep things on the floor, but it’s not enough to feel very strongly.

BasicElevator_withForceArrowsThis also points out an interesting problem with balancing the elevator. After all, it’s that balance between the Earth pulling it down at the spin flinging it out that keeps it in place. But as we’ve seen, the bottom of the cable is being pulled down towards the Earth at 9.8 m/s2 while the other end is only being pulled out at a mere 0.35 m/s2. Thus, while the top and bottom halves of the cable may have the exact same mass, the bottom half is heavier. That is, it is being pulled upon with more force.

The solution to this was given when these space elevators were first proposed, and that was to put a ballast weight at the far end of the cable. If it’s massive enough, it does not even need to be at double the geostationary altitude. It could be closer to the Earth, but since it would still be above geostationary orbit, it would be pulling with all of its weight (its mass times its centripetal acceleration) outwards. Thus, you can still balance out the space elevator and keep it floating serenely in the sky.

Ahh, I hear you saying, but what if we just made the cable longer? After all, the further out the cable goes, the centripetal acceleration acting on it goes up. Maybe if we made it long enough so that the far end did experience one full g of centripetal acceleration, there would also be enough force from the mass of that longer cable to balance it out. Maybe there’s still hope for some kind of mirrored gravity at either end of the cable?

Unfortunately, no, it doesn’t work.

The root of the problem is that while gravity drops off with the square of the distance from the Earth, the centripetal acceleration builds linearly with the distance. To experience one gravity at the far end of the cable, being swung around us once per day, the cable would have to be 1.84 million kilometers long.

There are two problems with such a long cable. The first is that the orbit of the moon is only about 384,000 kilometers. While a space elevator on Mars would face a similar problem with the small moons there, it has been suggested that the moons are small enough that well-timed wave maneuvers (like plucking a taut wire) would allow the elevator there to dodge the moons. However, Earth’s moon is 156 times wider than the largest of Mars’ moons, and even if its slow-moving body could be dodged, it would be impossible to dodge its gravity which would take the math into even crazier areas.

But the bigger problem goes back to that disparity between the two forces’ relationship to radius. While the gravitational acceleration acting on the bottom of the cable drops away rapidly as it rises from Earth’s surface, the acceleration acting on the far end of the cable as we back away from the end would only decrease linearly. So, while the mass of the “top half” of the cable would be only fifty times as massive (at a minimum), the force acting on it (the mass of each part times the centripetal acceleration acting on it) would be over a thousand times as great as the force of the lower half being pulled down to the Earth.

Even if it was made from a material cable of withstanding that much force, there is no way we could secure it to the surface of the Earth. It would be plucked from its docking station like an unwanted nose hair and flung into space like… well, like an unwanted nose hair.

So keep the solar system free of nasty million-kilometer cables, and don’t insist on 1 g of centripetal acceleration at the end of your space elevators.

Marriage in SF/F

I attended a wedding last week, and it got me thinking about the institution of marriage in science fiction and fantasy. I frequently run into stalwart captains and noble queens who are single by either choice or tragedy. I also see a number of couples, but I confess I don’t run into all that many marriages, and certainly even fewer weddings. Maybe that only means I’m reading about a bunch of loners, but it does not show up as often as I’d expect.

Still, it’s not entirely absent. There actually are a number of marriages, and while some are the humdrum union of old sweethearts, I’m more interested in the marriages that can only occur in a science fiction or fantasy setting, or at the very least, that won’t happen in our world today.

InterracialMarriageGiven that last week’s wedding was an interracial marriage – my long-time friend is black, and his bride is white – I thought I would start with some similarly mixed marriages. Perhaps the most famous is that of Spock’s parents, his human mother Amanda and his Vulcan father Sarek. Another of my favorites from SF is the union of Babylon 5’s Captain Sheridan and the Minbari Ambassador Delenn. Rather than focusing on their progeny, we got to see the culture clash play out in their courtship. (One word to my fellow Babylon fans: Woohoo!)

SheridenDelennOn the fantasy side, Lord of the Rings had Aragorn marry Arwen with hints of half-elf children in their future. I’ve seen a few human-demon pairings as well as human-vampire pairings, but very few actual weddings. (Sorry, I’m not aware of anything called Twigh Lite.)

These all tend to be humanoid to humanoid pairings. I don’t know if that’s a lack of imagination, a lack of effects/makeup budget, or a simple limit on what parts match up with other parts.

HeinleinFridayThen we get into different kinds of marriage. Heinlein was all over this with both line marriages in The Moon is a Harsh Mistress and group marriages in Friday. Some of these were meant to preserve property, while others were simply a raised finger to the institution of monogamous marriage.

I’ve also run into time-delimited marriages from several different authors. C.J. Cherryh’s Ateva, particularly their nobility, marry for reasons of political alliance, and those marriages come and go with shifting loyalties. Kube-McDowell’s Quiet Pools showed me contractual marriage with and without options for child-rearing.

Sharon Shinn’s world of Samaria had angels living amongst humans, but angels were forbidden to marry angels. Instead, angels always married humans, but even then, it was often a more open marriage, particularly for the male angels. You see, an angel-human pairing could produce either human or angel children, but since successful angel births were rare, male angels were spreading their seed far and wide. I’ll let you read the books for the messy details of when the god Jovah would choose the Archangel’s spouse – not always a match made in heaven.

I’ve also run into SF societies that completely divorce, so to speak, marriage from reproduction. The merchants of C.J. Cherry’s Merchanter’s Union did not really marry. The woman would have sex with men from other ships, because their own ship was filled with family. Children were not raised by mother and father. Rather, they were raised by mother and aunts and uncles. The demons in my upcoming Hell Bent have similar family lives for very different reasons.

A world I imagined had a society made more intellectual than emotional by computer implants, and marriages were based on intellectual harmony with no regard to physical or sexual chemistry. Choosing a sexual partner was done via genetic analysis, and potential partners approached the selection with about as much emotion as we would choose a lab partner for class. Child-rearing was quite different, of course, but the implants allowed early intellectual maturity, long before the body reached adulthood.

hivemindsmallNow, if that hasn’t completely detonated the nuclear family, I’ve heard of even stranger arrangements, where the aliens in question were sentient symbiots, so simple pairings were by definition group marriages. Taking it further, there are some fictional races that live in between individual sentience and shared hive minds, so the notion of marriage for love vs. arranged marriage is dropped into the conceptual blender and thoroughly pureed.

These days, marriage is a political hot potato here in the US with the ongoing debate over gay marriage, but I would like to think that in the future we’ll at least be able to talk about marriage without invoking Nazis or the end of civilization. After all, it’s all about finding the symbiotic hive mind of our dreams, right?

So how about the rest of you? What’s the wildest concept of marriage you’ve run into in SF or fantasy?

The Last Book You’ll Ever Read

As I edit Ships of My Fathers, I’ve been thinking back to my father’s death. Specifically, I remember that towards the end, when it was clear that the second round of chemo was not going to work, he was reading a book on cosmology and faith. As a lifelong scientist and Christian, he was looking for some kind of reconciliation between two oft-conflicting viewpoints. I don’t know if he found what he was looking for, but I do remember thinking about mortality and limited time and that someday, I will be reading the last book I will ever read.

skullandbookWhat kind of book is that going to be?

It might very well be something of a religious nature. I don’t expect that, since I don’t feel I have a lot of open questions in my theological view of the universe, but you never know what you’re going to do when you’re staring death in the eye.

But I like to think, instead, I’ll be reading fiction. Maybe I’ll reread some old favorite tale. Maybe I’ll be tearing my way through some new series that a friend recommended. I have always loved to escape into stories, and I think they will be a great comfort to me in my final days.

If I know the end is coming soon, I don’t think I’ll put the book down when I’m done and declare, “That was the last book.” More likely, I’ll pick up the sequel, because I want to know what happens next.

And isn’t that perhaps the best way to go? With the hunger for story and a thirst for that great mystery of what comes on the next page?

What do you think your last book will be?

Secrets and Surprises

hiroshimaheadlineI once asked my grandfather what he had thought about the atomic bomb when the news of Hiroshima broke. I expected him to say he was surprised, and while he was, it wasn’t the surprise I had been expecting.

You see, he knew the atomic bomb was under development. In fact, most of the people in his office knew, too.

No, he was not working at Los Alamos, nor was he at Oak Ridge or any other Manhattan Project facility. He was an electrical engineer at Bell Labs in New Jersey. His main military effort during the war was for sonar.

So, given how secret the Manhattan Project was, how did he know about it?

It was the sudden silence in the various scientific publications. In the late 1930’s, there had been a steady stream of advances in the study of radioactive materials and how they transformed from one element to another. There were also theoretical hints around nuclear fission and what it could mean. He remembered expecting to read very soon that they had confirmed the splitting of the atom with details about energy output, particle emissions, and so forth.

Instead, there was nothing.

Mind you, my grandfather was not a nuclear scientist. In the day, that was more a sub-specialty of chemistry, but he wasn’t a chemist either. He worked on signal amplifiers and repeaters. In fact, he considered his greatest achievement to be a key development in the repeaters for the transatlantic telegraph lines.

But he read the scientific journals, just like all of his fellow engineers at Bell Labs, and when a lot of big names suddenly went silent, they began to wonder. Calls to various colleagues at universities came back with reports of certain professors and promising grad students going on extended sabbatical to parts unknown.

From an unrelated source, John Campbell of Astounding Stories also knew something was up, and he knew it was in New Mexico. According to the story, he knew this by how many subscriptions had suddenly moved there, and when he started noting the names on those subscriptions, he also put two and two together.

So what had my grandfather been surprised at? He said he was surprised by the reality of how powerful the atomic bomb was. Little Boy exploded as 16 kilotons. Fat Man was all the way up at 21 kilotons. While they had not talked in detail around the office — it was wartime, after all — the general feeling was that fission explosions might be one hundred times as powerful as chemical ones. Some argued for closer to a thousand times as powerful.

They knew high explosive bombs were getting up to one thousand and two thousand pounds, essentially a ton. They knew some of the limits of what the bombing aircraft could carry, and from that they estimated that the fission bombs might reach 500 to 1000 tons, i.e. one kiloton. “Of course,” he said,”we didn’t really know what a kiloton explosion would look like.

portofchicagoaftermathBut they got some idea in July of 1944 when the Port of Chicago (northeast of Oakland, CA) suffered a giant munitions explosion of about 1800 tons of TNT, i.e. 1.8 kilotons. A cousin of my grandfather’s had been one of the few surviving officers of the ship that exploded (the SS E. A. Bryan), and he had only survived by the luck of being on shore leave, visiting his girlfriend in nearby Oakland. Apparently he had felt the explosion through the ground, many miles away and could see the fireball rising over the horizon. But still, the much closer towns of Concord Pittsburg had not been particularly damaged.

Armed with what knowledge they had, my grandfather had expected fission bombs to be used as super “blockbusters”, and that bombers would blanket an industrial section of a city with five or six of them, possibly expanding to the larger city with another ten or twenty. He said one of his coworkers argued for fewer since the concentrated explosion would generate a more lethal shockwave than the larger pile of TNT had done in the Port Chicago explosion. Even then, it was assumed that a bombing raid would need at least four to ten to be equivalent to a larger TNT-based bombing.

hiroshimadamageIt never occurred to him that it might be so powerful both in magnitude and in lethality that a single bomb could effectively destroy a mid-sized city. “It made me glad we were out of New York,” he said.

The other surprise he confessed was that we had not used it on the Germans. It did not come out until later just how late in the war the bomb was ready, and he had spent much of the war wondering when he was going to see it being used in the European theater. Of course, none of them knew the logistics of gathering the fissionable material nor the design problems of making it work as an explosive, and it was that delay that caused a few of the detractors to suggest that no such effort was being made.

So, looking back on that, I wonder about our own future. If certain key researchers in quantum computing or nanotechnology suddenly went silent, would I know about it? If dark matter and dark energy theorists started disappearing into an Alaskan research institute would you realize it? I’m not one for conspiracy theories, but I have to wonder how many of us would notice if a relatively obscure research field suddenly went dark. Did they simply lose funding, or are we about to be surprised?