by Jeff Cunningham

Ni hao and welcome back to our ongoing look at the science and technology of everyone’s favorite cancelled TV show, Firefly. Today, we’re slipping the surly bonds of Earth-That-Was to look at gravity-defying vehicles and artificial gravity generators in space. As always, we’ll start by setting boundaries: We’re defining “anti-gravity” or gravity-defying craft as vehicles that travel hovering a finite distance from a gravity-generating point mass (such as the center of a planet) without generating any thrust or propulsion. That last part is the kicker: Rockets, helicopters, and Serenity herself don’t count, because they all get around by propelling something (air or superheated gases) downwards in order to push themselves upwards.

In the Verse

First off, if we agree to the definition we just set, there’s a couple of ships in the Verse of Firefly and Serenity that appear to hover and defy gravity, but are actually creating a lifting force through more conventional means:

The shuttles belonging to Serenity do indeed have engines and thrusters, they’re just really small (Serenity Blueprints Reference Pack). They use jet engines fed by an air intake on the underside while in atmo, and use ordinary reaction control thrusters (RCS, used on every spaceship since the race to the moon) while in the black. There’s also several different ships that are on the border, because we don’t really get a good enough look at them to tell if they’re powered by engines or some sci-fi, gravity-nullifying force:

For the sake of brevity, we’re going to limit our scope to the one craft that fans are most familiar with, and that we see the most of, the hover mule.

The Science

So, does the hover mule truly defy gravity? Well, the short answer is “no.” We’ll save the long answer of how gravity works for an upcoming installment of The Science of Firefly concerning artificial gravity. For now, the short answer is that gravity fields are radiated in all directions. If the mule generated a repelling force to oppose gravity through means that, again, we’ll discuss in the very near future, in addition to pushing the ground away beneath it, it would have the unfortunate side effect of pushing out in all other directions, causing our Big Damn Heroes to be thrown out of their seats. There’s another problem that it doesn’t take a PhD in theoretical physics to recognize: How smooth and level the flight is. In reality, this was because the hover mule scenes were filmed using a rig on the end of a boom extended from a truck going down a scenic highway.

If we stay in the Verse, though, and accept that as “real,” then it rules out gravitomagnetic repulsive forces. Think about it: If the mule were exerting some force that keeps it an exact distance from the ground, then it would be a bumpy ride driving through the brush–just like driving a vehicle on wheels, which also keep the vehicle at an exact distance from the ground. A six-inch rock on the ground would translate upwards into a six-inch bump experience by the crew of Serenity. Even if, instead of exerting a “pushing force,” the mule were somehow “cancelling out” gravity or the effects of gravity on the craft, hitting a bump in the road would then cause it to fly off into the sky, into the black, and never come down. Just how does the hover mule fly, then? The first thing you may notice when looking at the mule is how little there is to see: The hovercraft seems to be nothing more than four seats and a couple of structural beams. Once again, the Blueprints Reference Pack sheds some more light, by identifying some of the non-descript features at the rear of the mule as thrusters that push it forward, and “ground-effect fans.”

The term “ground effect” refers to how air behaves near the ground, which would suggest that we’re dealing with a descendant of conventional hovercraft technology seen today.

Hovercraft travel on a cushion of air pumped underneath it by powerful pumps, which would explain why the mule’s ride is so smooth: minor bumps in the road aren’t so directly translated to the craft itself. Hovercraft employ skirts to trap air underneath it so that they can get away with less powerful engines, but if you’re willing to eat the cost, you can skip the skirt and take the same brute force approach used by VTOL Harrier jets, Serenity herself, and, apparently, the hover mule. There’s several problems with the idea of the hover mule being a true hovercraft, though. Watch the following scene again and see if you can spot what’s wrong.

If you were watching closely, you may have noticed that, with the exception of the land-bound variant of the Crazy Ivan that Zoe pulls, the hover mule barely disturbs the ground that it drives over. If we assume from its size that the mule weighs about as much as an ordinary automobile, then it would take a great deal of lifting thrust to keep it aloft. That thrust equates to a great deal of air being pushed downwards, which means it should be kicking up a ton of dirt and making a great deal more noise–exactly like a helicopter, or even Serenity herself does. The crew of Serenity shouldn’t be able to hear each other over the engines that would be needed to keep flyin’.

Is there some other way to generate lift without the use of extremely loud turbines? It turns out that the answer to that question just might be “yes.” Electrohydrodynamic (EHD) thrusters, better known as ionocraft, utilize the Biefeld-Brown Effect to create lift with no moving parts. A simple “lifter” will consist of a small, lightweight balsa frame with two electrodes of opposing charges separated by a small gap.

When these electrodes are charged with a ton of juice, it ionizes nearby air molecules by stripping electrons away from their atoms. These charged ions then are attracted to and travel towards whichever electrode acts as the “collector.” As these ions travel along a line from one electrode to the other, they push other molecules of air out of the way. With enough voltage sent through the device, these pushed molecules add up to what’s called an ionic wind–it pushes air downwards like a helicopter, but without the helicopter blades.

The basic principles behind EHD thrusters are simple enough that they’re actually easy enough for hobbyists and classrooms to construct using plans found online. The Mythbusters even examined them in one episode. As we’ve covered earlier (and as said Mythbusters further proved), ionocraft aren’t defying gravity, but they do generate lift without moving parts. The other catch that nearly resulted in potentially fatal injury on the set of that episode is the fact that it cannot be over-stressed that it takes a lot of voltage to make it fly. On average, the theoretical lift generated by a simple science-fair type of EHD craft is about one gram per Watt of power pumped into it. Now, this alone does not invalidate the Biefeld-Brown Effect as a possible means of achieving flight in Firefly and Serenity. You may recall from our last episode that we observed that the centuries separating us from the setting that the show takes place in have clearly brought remarkable (and entirely plausible) advances in the field of power density. In English, that means that, in the future that the Verse exists in, they’ve figured out how to cram way more juice into a small battery without making it any bigger. Otherwise, they wouldn’t be able to fit the enormous amount of power required to operate a laser into a device that fits in your hand (like the Lassiter laser pistol from the episode “Trash”). Unfortunately, the tendency of those high voltages to short out or injure the operator is the final nail in this anti-gravity coffin.

We refer you one last time to the film: http://www.anyclip.com/movies/serenity/arriving-on-the-planet/

No doubt, you noticed that, just as the crew are getting ready to leave in the hover mule to be bad guys at around 1:15, Kaylee is on her back beneath it, performing some last-minute maintenance. Remember, ionocraft generate thrust with moving air. If the mule is powered by EHD thrusters with no moving parts that have been scaled up with enough power to match, it still has to blow around enough air to push it off the ground. In such a confined space like Serenity’s cargo bay, it’d be like a helicopter spinning up its rotor blades in your living room, blowing anything lighter than a bowling ball from wherever it’s been placed–but Kaylee doesn’t even have so much as one of her bangs out of place when she gets up from underneath the hover mule, when simple physics dictate she should look like this:

The final clincher, though, is that she’s under the mule working on it in the first place. Remember, these things require a lot of juice to work–enough to where touching that tiny little balsa model while it’s in flight will more likely than not kill you. As comfortable as little Kaylee is around machines and even if such a hypothetical vehicle had shielding (at least to protect the passengers), we’d have to believe that such a mechanically gifted person as her would never risk working on it while it’s actually running.

Conclusion

So, where does that leave us? When we here at Take Back the Sky set out to look at the science behind Firefly and Serenity, we didn’t really give much thought to what would constitute “Busted” or “Confirmed” for each topic we looked at. Part of the nature of science itself is that you really can’t actually prove or “confirm” anything to be in the positive. What we can do, and have strived to do here is to essentially to find the “most likely suspect,” scientifically speaking, behind all the blinking lights of the Verse.

Unfortunately, this time, it looks like we can’t do that. There’s just no known way that the hover mule and similar craft in Firefly and Serenity can exist and fly like they do using any existing or theoretical principle of the laws of physics. On the other hand, though, because the series and film take place centuries into the future, we can never really say anything is well and truly “busted,” because we have no way of knowing what world-changing discoveries and breakthroughs could occur between now and then. A hundred years ago, who could have believed that people would walk around with tiny devices in their pockets that allow them to see and talk to anyone in the world, as if they were in the same room, instantaneously? That sort of thing violates what they at the time believed to be the limits of physics, and we’re committing a truly terrible fallacy if we believe that we’re somehow immune or in any way superior to them.

So, with that in mind, from here on out, when we encounter something in the Verse that simply can’t be explained by known science and technology, we’re going to give it our own special grade…

Verdict: “Not so solid…”

…but there’s one last wrinkle in our tale. It’s beginning to scare us here how seemingly inconsequential details in Firefly and Serenity that are so easy to miss turn out to completely vindicate the Verse from a scientific standpoint (see the previous entry’s review of the Reavers’ microwave-beam weaponry).

Remember the Bellepheron Estates from earlier? Large, artificial islands floating in the sky above some body of water where the wealthy elite live? We’re led to believe that each is the size of a mansion, with some space for surrounding grounds. Each of these estate-island-ships would need to dedicate a lot of the space beneath “ground level” to large, powerful machines–powerful enough to keep something so large hovering at a relatively fixed height above the water’s surface.

The trouble is, with such a discerning clientele living aboard these things, you can’t use ginormous engines like you could aboard a S.H.I.E.L.D. helicarrier. The vibrations and rumblings of those engines would be transmitted through every square inch of the estate. There’d be no escaping it, and there’d certainly be no sleep, because no matter where they placed their fancy four-poster beds, they’d still hear it at some level through their pillows.

Since we’ve already showed that scientists of the Verse have solved the problems of energy density, it stands to reason that it’s not impossible that the Bellepheron Estates use the Biefeld-Brown effect to levitate through electrohydrodynamic forces, which would allow the noble and wealthy of the Core Worlds to rest their heads in peace. They’d have to scale up the machines and supply them with enough power, but again, from what we’ve seen in the show, it’s entirely possible.

Think back to the episode “Trash”: When Wash holds Serenity steady beneath the estate of one Durran Haymer as Kaylee and Jayne engage in dangerous hacking and sabotage atop the ship, they’re not blown off by a downdraft generated by the estate–which makes sense, because they’re at the spot on the estate where automated drones must dock to pick up garbage containers, and they’d have no less difficulty performing those duties in the wake of an EHD thruster powerful enough to keep the thing afloat. It’d make sense for the engineers who designed the estates to place said engines at the lowermost point of the estate, with utility and maintenance ports located above it where they’ll be out of the way.

However, to keep the estate in the air, there’d have to be an astronomical level of voltage running through the island, which would pose severe risks of electrocution to anyone touching the wrong spot on it while it’s in flight–and guess what happens to Jayne?

Who would have thought, huh? Now, this isn’t proof positive, but it at least suggests that something like the Biefeld-Brown effect is at work here. Looks like we’ll end on an up note, after all…

Verdict: Science is Shiny!

See you next time!