The Science of Battlestar Galactica

by Di Justo, Patrick

  CAFFEINE: THE ORIGINAL FTL DRIVE FUEL

  I do a lot of public speaking, mostly about astronomical education and EPO (Education and Public Outreach) for the Cassini-Huygens mission to Saturn. I sat in a daze in the Portland airport, having just given a description of Cassini’s expected science return from Saturn to a conference of military personnel and contractors. Since I had some frequent-flyer miles, and since Portland was (relative to L.A.) in the Vancouver area, I decided that after my talk, I would continue on to the BSG set for a two-day set visit. (Although I could do all of my work from L.A., occasionally I was allowed to visit the set and see the filming.) So in order to get my affairs in order enough to afford the three-day absence from my day job, I had been up all night working. Hence the daze.

  Since Portland International Airport has free Wi-Fi, I figured that I’d check my email while waiting. Just as the gate agent announced that it was time to board, I read a semi-urgent email from Ryan, Battlestar Galactica’s writer’s assistant, asking that I get in touch with Bradley Thompson as soon as possible. I sent a brief reply that I was about to board a plane, and that I’d phone when I could.

  The instant we landed in Vancouver, I flipped open my cell phone and made the call. “Hey Bradley, you know that annoying guy on every flight ever? You know, the one who gets on his cell phone the instant you land and talks really loudly? For the first time in my life, it’s ME. What’s up?” Bradley said, “You knew this was going to happen eventually. David [Weddle] and I are doing the rewrite on [episode] 216. We need you to figure out how the FTL drive works, so we know what components it has, so we know what can get battle-damaged, so the captain of Pegasus, in a Wrath of Khan-like move in the heat of battle, can run down to engineering and save the ship . . . I get in at 10:30 tomorrow, that’s how long you have.”

  Frakkin’ wonderful. Did I mention that I’d been up all night?

  So I slept for a scant few hours, got up at 0-dark-30, and made a huge pot of coffee. As Bradley alluded in his phone call, we had previously held brief discussions on the FTL drive—not so much about how it worked, but more in the form of “we’re going to have to describe this eventually.” So I already had my own rumblings of ideas about how the FTL drive worked, but had never put them into a coherent formulation. Luckily, and wholly coincidentally, my own musings were not dissimilar to those shared by Ron in his blog posting.

  So I paced my hotel room, and drank coffee. I mused on the science and technical aspects of the FTL drive, and drank coffee. I wrote up tech notes for the FTL drive, as well as other aspects of the new script, peed a lot, and drank still more coffee. I hit SEND on that e-mail at 10:28, and managed to get to the set in time to see Billy Keikeya get shot.

  This “description” of the inner workings of Galactica’s FTL drive was the product of 5 sleep-deprived hours of pacing, pondering, writing, caffeinating, and peeing in a Vancouver hotel room. Over the years, at science fiction conventions, the single most frequently asked question I get is, “How does Galactica’s FTL drive work?” I have always given the same reply: “As long as this could be a plot point in a later episode, I’m not sayin ’.” I fully realize that this has generally been interpreted as “How the FRAK do I know?” It’s nice to be able to share the details now, as well as confirm that, yes, we did have a clue.‹

  CHAPTER 23

  Artificial Gravity

  If artificial gravity could be invented, how might it work? Firing a rocket engine in a spacecraft will create a sensation of gravity, in the same way that accelerating in a fast car will push you against the back of your seat, and taking off in an airplane makes you feel as if your stomach has been left behind on the tarmac. This acceleration feels just like gravity, and from the perspective of the universe, it is gravity.

  Constant acceleration seems like the easiest solution to the artificial gravity problem: just keep firing Galactica’s engines at a constant rate in the proper direction, and presto, the acceleration will keep people and objects glued to the deck as though they were standing on Caprica itself. Instant artificial gravity. Unfortunately, constant rocket acceleration is probably the worst method of creating artificial gravity.

  Let’s assume that Caprica is the same size as Earth, with the same gravitational field. In order to create Caprica-equivalent gravity on Galactica, the engines would have to fire in a direction perpendicular to the deck in a way that would increase Galactica’s speed by 9.8 meters per second. Every second. In the first second, the entire ship would be moving at nearly 10 meters per second. At the next second, it would be moving at almost 20 meters per second. After one hour, Galactica would be traveling at 6 kilometers per second, in a direction perpendicular to the decks, and still accelerating. At the end of five weeks the ship will be traveling at 10 percent of the speed of light, still in a direction perpendicular to the decks, and it’ll just keep going. At the end of a year, assuming the fuel holds out, Galactica will be traveling at a large fraction of the speed of light, and it will become increasingly difficult to go any faster. Your artificial gravity is over.

  Samuel Anders.

  Samuel Anders.

  The next simplest way to produce a sensation of artificial gravity is by rotating the spacecraft, or at least a section of it. Objects in the spacecraft will move with the rotating section, and this motion will eventually cause them to “stick” against the outermost rim of the rotating section. The force of inertia, known more colloquially as “centrifugal force,” keeps crew members pinned against the hull in the same way that the spinning carnival ride Vortex keeps victims—uh, carnival goers—pinned against the wall.

  Spinning the spacecraft works well in movies and on TV, but in real life there is one problem with this type of centrifugal ersatz gravity: the Coriolis Effect. It’s kind of complicated, but the basic idea is that if you’re located on or in a rotating environment, you’ll start to rotate, too (or you’ll spend a phenomenal amount of energy to stop yourself from rotating). The Coriolis Effect causes hurricanes to rotate counterclockwise in the Northern Hemisphere and the clockwise in the Southern Hemisphere, and in a smaller space it would do the same thing to a person’s inner ear fluid, which regulates the sense of balance. In a rotating space station your eyes might tell you that your body is standing still, but your inner ears will “know” that you’re spinning around. If you’re lucky, you’ll only get dizzy.

  Experiments on Soviet cosmonauts showed that Coriolis nausea caused by spinning the spacecraft can be eliminated if the rotation rate is kept low—which naturally means that the ship, or at least the radius of rotation, has to be correspondingly huge. Most people have little trouble tolerating anything up to 3 rotations per minute (RPM) without throwing up. Some people never make it past 3 RPM, while others can acclimatize to 6 RPM. Practically no one escapes illness at close to 10 RPM. In summary, if the ship rotates too slowly, a large fraction of the crew is vomiting from space sickness; if the ship rotates too rapidly, a large fraction of the crew is vomiting from motion sickness. When humans leave Earth to explore space en masse, invest in the company that makes puke bags.

  Obviously, Galactica does not spin to simulate gravity, but a ship named Zephyr does. Zephyr, also known as the “Ring Ship,” is one of the most prominent ships in the Rag Tag Fleet. Zephyr seems to be quite the oddity within the Fleet, apparently being the only ship that creates artificial gravity in this way. This could imply that Zephyr is very old, but if that’s the case then her FTL drive would have had to have been a retrofit. Perhaps, like a Chrysler PT Cruiser, the inner workings of the spacecraft are modern, but she has a “retro” exterior: “Come experience what space travel was like for our Kobolian ancestors!” Zephyr just may be a Colonial manifestation of steampunk.

  The “Ring Ship,” Zephyr.

  Zephyr is one of the larger ships in the Rag Tag Fleet, and it stands out. Every viewer has noticed that gigantic ring slowly spinning. Is that realistic, though? Should it be spinning faster? Slower? That’s a reasonably
easy question to address. The strength with which occupants are pinned to the hull (the fake gravity) depends upon the diameter of the ship and the speed at which it rotates. To explore the realism of this, we start with one equation and one definition. The equation for centripetal force is

  where F is the force felt by the object spinning (in our case, the person feeling the artificial gravity), v is the rotational velocity, m is the person’s mass, and R is the radius of the spinning section of the ship. We further define Γ as a factor that indicates the number of Gs we wish to emulate. In other words, if we have a ring spinning fast enough to simulate twice the force of Caprican gravity, then Γ = 2. Obviously, Γ would normally be 1 because we want to simulate one Caprican G. So to express the above equation in terms of G forces, we have

  where g is the normal downward acceleration of gravity, 9.81 m/s2. The miracle of algebra occurs and we have three equations. To find the simulated gravity for a given spin radius and spin rate,

  where f is the rotation rate in RPM and π is the constant 3.1416. To find the spin radius for a desired force of gravity and RPM, we rearrange and use

  Rearranging again, for a given rotation radius and simulated gravity, the rotation rate in RPM is given by

  So if the radius of Zephyr’s ring section is 500 meters, which is close to what it appears onscreen given its perspective to other ships, in order to simulate 1G of gravity the ring would have to spin at 1.33 RPM, or 1 1/3 times the rate that a second hand moves around a clock dial. This happens to be very close to what is observed onscreen. What do you want to bet that somebody in the Battlestar Galactica visual effects department did this calculation as well?

  If all objects have gravity, doesn’t Galactica, as massive as it is, exert its own gravitational force? Yes. Can that be what keeps everyone glued to the deck? No. Galactica’s gravitational field is large, and Galactica surely warps the space around it, but nowhere to the extent that would provide artificial gravity similar to that of a terrestrial planet. It wouldn’t even provide gravity equal to that of a small asteroid, so the only other reliable way to make artificial gravity is to use science fiction and just make “artificial gravity.” This has been the other way to present space travel on a low budget, but it has just as many (if not more) problems as centrifugal ersatz gravity.

  How does Galactica’s artificial gravity work? We don’t know and probably never will, but we can make some calculated guesses as to the requirements and constraints upon its implementation. In chapter 12, “General Relativity and Real Gravity (or the Lack Thereof ),” we established that Isaac Newton’s Law of Universal Gravitation, expressing the force of gravity between two objects separated by a distance r, is

  (We recognize that General Relativity is a better way to understand the cosmos, but Newton’s equation is still used today as a good approximation of gravity in many theoretical applications.) If we take the time to understand why the force of gravity gets weaker as a function of 1/r2, then we can understand what might be involved in a practical implementation of artificial gravity.

  Let us imagine that any object with mass will emit gravitons: massless particles that travel at the speed of light. Further, imagine that gravitons are the agents that warp space. The more mass in a volume of space, the more gravitons are emitted; the more gravitons in a given volume of space, the greater the warping of space; the greater the warping of space, the greater the gravitational pull. We’re not alone in our imaginings; this is how many physicists understand how gravity operates (at a very cursory level, of course). If the model shown to the left is true, then a massive object like a planet or a star would emit gravitons that propagate radially outward from its center.

  Gravitons emitted from a massive object like a planet.

  Imagine that we take a snapshot of all the gravitons that leave the surface of the planet in the figure a given instant, and that we can count every single one of them. We would then know that N gravitons were propagating outward at the speed of light in a spherical shell that is one graviton thick. If the degree to which space is warped is determined by the number of gravitons in a given volume, the density of gravitons (σ) for that snapshot in time would be

  where rplanet is the radius of the shell (initially the same as the radius of the planet) and 4πr2 is the surface area of the expanding spherical shell. When the shell expands to radii R2 and R3, the density of gravitons is

  If we compare the graviton density when the shell is at R2 compared to when it first left the planet, we have

  If R2 = 2rplanet, then

  If R3 = 3rplanet, then

  W e can now see why the force of gravity decreases as 1/r2 and now have an even better understanding and appreciation of Newton’s Law of Gravitation! We can now better understand some of the issues behind the creation of artificial gravity.

  If the Colonials could somehow generate an artificial gravitational field, they would therefore likely use some sort of device that worked by emitting gravitons. (We have zero idea how to build a controlled graviton emitter, but let us assume that the Colonials know all about them and how to harness them.) The gravitons would have to be emitted in a directed pattern that mimicked planetary gravity. Since gravitons would not carry an electric charge, it would be nearly impossible to create a directed beam like we can do with charged particles (like in a linear accelerator) or photons (as with a laser).

  Since gravity’s effects diminish as 1/r2, an antigrav machine in the bowels of the ship (say near the CIC) would create Caprica-like gravity in the CIC only! Other parts of the ship would experience a gravity gradient—stronger gravity near the CIC, diminished gravity near the bow, stern, and flight pods. Items at the extremes of the ship would (1) feel significantly “lighter” than objects in the center of the ship and (2) would all lean away from the CIC! This is clearly no way to live.

  Most likely, the Colonials use tiny graviton generators (we’ll call them NAGGs, short for Nano Artificial Gravity Generators) embedded in each deck in each room and corridor. The NAGGs must be able to shape the gravitational field upward so that the gravitational field fills the room without making extremely tall people on the deck below feel as if they were being pulled toward the ceiling. Ideally, the field must be strong enough to keep people glued to the deck, and that means emitting the gravitons in a hemispherical pattern at best. If a NAGG were placed in the center of the room, we would have a similar problem as placing one near CIC, only in miniature. You’d be leaning away from the center of the room, or feel alternating gravity highs and lows while walking down the corridor. If the NAGGs are spaced linearly down the centerline of each hallway, and in a stripe within each room, then the graviton field would take the shape of a half-cylinder emanating from the centerline of the deck. In this case, gravity would trail off as a function of 1/r as the further you were from the NAGGs. The good news is that this is an improvement over 1/r2. The bad news is that this stifles crew social interaction: everybody walking down a corridor would be leaning ever so slightly away from the hallway centerline.

  Gravitons from an artificial gravity generator.

  If you put multiple NAGG strips down the corridor, we start to approach something that looks more like a constant field, without the highs/lows of our previous efforts.

  Gravitons from an artificial gravity generator.

  Clearly the more NAGGs embedded in the deck, the more planet-like the gravitational field. If graviton generators existed, they would be spread uniformly across any area that required gravity.

  All of this assumes that individual graviton generators could create hemispherical patterns. More than likely, the nature of gravitons would radiate in a spherical pattern. This means that if a society were capable of generating gravitons, and were able to make the generators small enough to embed within a deck, the gravity generators in the floor above would pull you upward nearly as powerfully as the ones beneath your feet would pull you down. So instead of the expected situation where the floor for one level is the c
eiling for the deck beneath, it’s likely that each floor that had NAGGs would be a “floor” in two directions, similar in structure to the hangar bays on the Pegasus.

  Although we have never had any visual clue that Vipers have artificial gravity, we have clearly seen that Raptors do. If the artificial gravity were engaged, and unless the gravity field were hemispherical, how would a Raptor ever get off the deck? Clearly, for tactical spacecraft like the Raptor, an artificial gravity system would be more of a complication.

  The bottom line is that even if artificial gravity could be created, by generating gravitons instead of rotating the ship or undergoing a constant acceleration, the problems are just beginning. Even after a society understands the nature of gravity, something that is currently beyond the ken of Earth physics, there will still be technological hurdles to overcome. In the foreseeable future, and perhaps forever, artificial gravity will belong to the realm of science fiction.

  CHAPTER 24

  Navigation

  Food, water, and fuel shortages. Few, if any, basic services. The constant fear of imminent Cylon attack. Although the Colonials have more than their share of problems, the problem of being “lost” in a Galaxy with over 300 billion stars scattered throughout its 32 trillion cubic light-years might be just as unsettling and as perilous as any of the others. In the episode “Lay Down Your Burdens, Part I,” Starbuck tells a Ready Room full of pilots and ECOs that the Twelve Colonies, in particular Caprica, are “nineteen plotted jumps away.” This is after a year on the run, one that began with 240+ (presumably somewhat random) jumps in “33.” The implication is that although humans have probably explored only a tiny fraction of the Galaxy, there is an infrastructure or methodology in place that allows them to recompute the positions of the Colonies, and that allows them to know their relative position within the Galaxy at any time. How would they accomplish this? How might the Rag Tag Fleet navigate from the radioactive remnants of the Twelve Colonies to Kobol to Dead Earth, and subsequently on to Earth II? The navigation of any vessel, from an automobile to a battlestar, is a process by which a navigator answers three basic questions: “Where are we?,” “Where are we going?,” and “In which direction do we go to get there?” While these questions sound fairly straightforward initially, interstellar navigation is another very good example of the adage “Anything studied in sufficient detail becomes infinitely complex.”