How's my logic?

[Millenniumfalsehood]

I'm in an argument with a guy on another forum about the nature of a set of exhausts on the back of Serenity (from that TV show Firefly). He seems to think they're the ship's sublight space drive, while I think they're the exhausts(heat or otherwise) for the ship's lightspeed drive. To provide context, the guy is attempting to justify making the little exhausts on the back of his Serenity model into nozzles, and I (being a rivet-counting accuracy nut ) want him to make them as accurate as possible to the show, since this will be released free to the public and I want to download and assemble the model without having to redesign it.

The relevant exchange went like this:

"Main thrusters are not exactly as they were on screen. I have shrunk the biggest one a bit and placed the four smaller ones further away - another little sacrifice of accuracy to maintain a hint of plausibility"

"Hey Micro, those are *not* the main thrusters. They're exhausts for the FTL engine system. The main thrusters are the big suckers on the wings."

"[flame]There ain't no FTL engine, it's just sort of gravity drive or something. But definitely sublight. And considering what kind of fiery wake these exhausts spit, they are certainly not just exhausts . Those big jet engines are there for atmo flying (although they work in vacuum too - weird).[/flame]
I'd really love to know how the Firefly engine works"

"Sure they are, it's just not heat that's coming out of them. It may be an exotic plasma byproduct of the reaction that generates the FTL speeds. There's no reason to assume they're anything other than a simple exhaust system. Besides, if they were an engine nozzle assembly that uses Newtonian impulse principles to move, they would have to throw out an incredibly dense fuel at average rocket exhaust velocities, or else they throw out conventionally massed fuels at incredible velocities. The second is highly improbable because the nozzles are tiny in relation to the hull, so the first one is more probable. If the fuel really *is* dense in order to achieve high speeds, then the ship itself would weigh too much to lift off using the jet engines on either wing. Assuming these are the rocket engines also ignores the large flaps around the beehive, which appear to focus or deflect a field behind the ship to get it to move.

And yes, in order for a ship to get anywhere in a star system the size of the Alliance system in less than a few months' time, a lightspeed system is *definitely* required, so it is a lightspeed drive of some kind. Think of our own Sol system. It takes light approximately 5 hours to get from the sun to Pluto. If the Alliance system is larger (the fact that it has several habitable planets in the habitable zone suggests it's a *MUCH* larger system and has a bigger sun than our own system), anything slower than lightspeed would be highly impractical for trade. Voyager 2 took 15 years to get to Pluto's orbit at a speed of 3.1 AU/Yr, or over 32,000 MPH. If a ship were going at that speed, it would need two months or so to get from Earth to Mars (if you average their respective distances, though there would be times it would be much closer). Even at half of lightspeed, it would take two hours, and evidence in the show suggests the planets in the Alliance system are further apart and myriad. Conventional chemical rockets or ion drives would be too slow and the fuel requirements too great, so a light drive which manipulates space or transfers the ship to 'hyper/sub/jump/space' would be required.

I doubt it's powered by gravity, as that's a pathetically weak force. It's more likely magnetic or M/AM in nature, due to the glowy bits (light is electromagnetic in nature)."

I'm 99% sure those are not a propulsion system, but I'm not sure of my logic behind the deductions I took to come to that conclusion. Am I waaaaaaaay off-base and spouting stuff I am ignorant about (I'm not too knowledgeable in regard to rocketry, so my knowledge of that is limited to what I picked up in past exchanges with people who are, and to be honest my memory of Firefly may be fuzzy), or should I stick to my guns?

[Simon_Jester]

There is no evidence that Serenity (or any other ship in the setting) can travel faster than light. The existence of interplanetary travel on a time-scale of days, even given the large size of the "Alliance" star system, only proves that ship speeds need to be up in the range of 5 or 10% of the speed of light.

Therefore, there is a fundamental flaw in your reasoning- the assumption that all STL travel is as slow as the gentle ballistic coasting of space probes powered by chemical rockets were (are) around the year 2000.

[Millenniumfalsehood]

Thanks for the quick response. I'm not in the habit of making an idiot of myself, but sometimes my fingers type before my brain engages(though I wasn't trying to suggest ships in Serenity are as slow as Voyager; I was using that as an example of a vehicle which used conventional rocketry to get to the outer planets).

That being said, I'm still not convinced those are the engine nozzles. They may be exhausts for the high-speed engine, but the speed increase seems to be due to the flaps and the beehive, not those impossibly tiny holes.

[PeZook]

Why does it matter what they are? You're arguing about placing them on the model. The guy should shut up about his "hint of plausibility" bullshit: how does moving the things around maintain it? It's still a fucking interstellar starship. Besides, it's not like he's qualified to decide what is an what is not plausible on rockets. His approach would be like some XXVth century nerd moving around the HMS Nelson's guns on his computer model because he thinks they're not optimally placed: the actual ship has those guns placed like that, so a model should have them there, too.