Joshua Pawlicki's Explanation of How It Works

Please note that this material was originally a PDF written by Joshua Pawlicki that came into my hands as part of a .zip file of technical info for game purposes. When I find the proper link to Pawlicki's site, I will post it here.-- Maer

Mechanics 101

Foreward

Legal information: This fan-based companion to the Serenity Role Playing Game is non-profit, and is designed to supplement the said game by including expansive information. Serenity, Firefly, and so on are registered trademarks that are switching company hands rather rapidly. This information is based on the Firefly series.

On with the show: Well, if you're reading this, then you are a great deal like me and quite unsatisfied with “technobabble” that the Serenity RPG suggests that players use to determine the effects of a ship. This was originally designed for just myself, then myself and my GM, but I've decided to write it like this just in case it is publicized on some forum. You have my permission (if you need it) to distribute this online or whatever. Have fun, good rolls to you.

At any rate, this document (written January 14, 2006) details the core mechanics of a boat in the 'Verse, and explains the general underlying theory behind that, as well as some issues with the boats that might not occur at first glance. This is not official. It merely offers an alternative method to “technobabble” of looking at the ship mechanics. Most of the scientific principles here are correct (the outstanding exception is the Gravity Drive). But it's as close as I can get.

-Joshua Pawlicki
Ship Mechanic of the Swan

Reference Tables

Mach # = (speed of object/speed of sound) = 761 mph (1225 km/h) (at sea level, standard pressure)
                                        At higher altitudes, there being less air, sound travels slower, so Mach # increases as speed stays constant.
                                        Mach <1 is subsonic, .8-1.2 is transonic, 1-5 is supersonic, Mach >=5 is hypersonic (at which point the air around the ship
                                        gets compressed enough to really start screwing with you).

Speed of Sound = Mach 1 = 1225 km/h = 761 mph

Assumptions:
Gravity Drives can control gravitational fields through electromagnetism:

1. Screening -                Reduces gravitational attraction between two objects.
2. Artificial Gravity -       Creates a point that has the gravitational attraction of a planet, but only within a screening field, or on a planet-wide basis (terraforming)
3. Inertial Control -         Setting screening and artificial gravity against each other can reduce the inertia of an object (only in one direction). Also known as Inertia Reduction. Check                                    out the source book for more information on this.
   
   
   

Ship Systems Table

Function	Device	Fuel/Input	Exhaust	Brief Description
Gravity	Gravity Drive	Electricity	Electromagnetic Radiation	See Assumptions.
Power	Fusion Reactor	H2O Packs	He2, O2, Heat, Electricity	A hydrogen fusion power generator.
Heat	Heat Sinks	Heat	None	Heat storage.
Propulsion	Thrusters (Pods):	(See Below)	(See Below)	A reconfigurable multi-mode jet engine.
	Turbine Electricity, H2	Heat, Fumes	Spins a turbine to intake air, then ramjets it.
	Ramjet	H2	Heat	Compresses air and heats it, expanding it.
	Scramjet	H2	Heat	A supersonic version of the ramjet.
	Rocket	He2 / H2*	Heat, Fumes	Output of superheated gases provides thrust.
	Pulse Engine	Heat, Electricity, Gas*	Superheated radioactive gas	A really big rocket with gravitational aid.
Hull Hull	None	None	Vacuum and radiation shielding.
Atmosphere	Algae Tanks	CO2, Heat, Light	O2	Photosynthetic creation of oxygen.
Water	Tanked Water	None	None	Basically you just bring it along.
Food Stored Food	None	None	Basically you just bring it along.
Waste	W. M. S. Waste, Electricity	Dehydrated waste, H2O	Centrifuged, purified, then compacted.
Navigation	Computers	Electricity	None	Pre-placed beacons assist your computer.
Sensors	Sensors	Electricity	None	RADAR-like, but not just radio waves.
	Scanners Electricity	None	More advanced and specific than sensors.
Communications	Com. Transmission	Electricity	None	As scanners do, it sends out a EM signal.

Notes to Ship Systems Table:
(A slash indicates “or”, a comma indicates “and”.)
(* - In theory the pulse engine and rocket mode of the pods can use just about anything gaseous that'll expand when heated. It is most efficient to use the superheated helium exhaust from the fusion reactor, however, since this serves no other purpose on the boat.)

Required Supplies Table

Refueling Needed
H2O Packs	Bought at resupply depots. Dideuterium Oxide (2H2O) and Ditritium Oxide (3H2O) for the fusion reactor. See How it Works: Fusion Reactor.
H2O Tanks	Standard cheaper water containing various isotopes of hydrogen for drinking and washing.
Self-Produced
Carbon Dioxide (CO2)	Produced by human breath.
Electricity	Produced by the Fusion Drive. All you could want.
Heat	By-product of the Fusion Drive. See Exhausts: Heat, also.
Light	Commonly produced by electricity.

Exhaust Table

Category	Description
Human Waste	Poop and the like.
Contaminated Water	From laundry, showering, washing dishes, etc.
Superheated H2 Gas	From the Thrusters and/or Pulse Drive.
Heat	It's hard to dump heat into space. There's no molecules to heat up. Heat is thus stored in heat sinks. Most ship designs allow you to use that heat to superheat water and eject it into space as an emergency overheating backup, thus ridding yourself of heat.

Introduction

Hey, so let's face it. Technobabble is for fools with no scientific interests and no desire to expand their understanding of what's really going on. This is a semi-scientific document detailing a basic layman's understanding of the processes going on in the ship.

This document was designed for the ship engineer and the GM so that they can know what the heck is going on, and hopefully wow their non-physicist friends into oblivion. Pilots should also read the How It Works: Atmospheric Flight and How it Works: Space Flight sections.

I have no extreme education in the field of physics. So some of this could be a little wrong. Please correct it if you can. But this is what I've gained from hobbyisting it. If something in here confuses you, check out the topic at www.wikipedia.org. Happy flying.

How It Works

When thinking about flight, there are two major modes to consider: in atmosphere and out of it. Flying in atmosphere gives you friction, which produces heat, which can pretty much burn you up if you go to fast and aren't aerodynamic enough. The upshot, however, is that you can lose heat to your surroundings (well, that's usually an upshot anyways), and that you can use the air itself for propulsion.

Atmospheric Flight

The problem with fast in-atmosphere (atmo) flight is overcoming the resistance of the air against your hull. Anybody can fly a boat slow. Anyone can drive a car slow. But you never see anyone doing that. There are several solutions to generating efficient propulsion in atmo and beating the resistance of the air. Aerodynamicy will reduce the resistance of the air because you can channel it well so that it's bouncing off you less. The trick with the flight is staying up there. Modern aircraft use airfoils on the wing to keep them up (which, in small detail, uses air flowing over the wing to push up on the underside of the wing while also creating a lack of air that pulls up on the top of it). You may choose to include these in your boat or not. The further you get from the fuselage (the main body part of an airplane), typically the less distorted air you get, and the more stability. Thus, typically, a larger wingspan means more force directed properly on the airfoil, and better lift. Properly designed airfoils have minimal drag, slowing you down less than poorly designed airfoils. This is, however, limited by materials. The force exerted on the tips of the wings of a too-far-reaching boat will literally rip the wings right off, and then you're in trouble. Of course, the "screening" ability of the gravity drive makes this totally unnecessary.

So right now you're probably thinking that you didn't want to talk about a plane, instead a spaceship. Airfoils are a neat thing for a mechanic to know, but your boat probably has big huge engines, not wings. In the Firefly/Serenity universe, most boats have large engines that swivel and provide lift to gain effects similar to a VTOL. Well, the design of these engines is (with modern materials) rather difficult to make reliably, although given perfect strength materials it could be done easily. The primary engine, known as a thruster or a pod, is a four-part engine. The basic principle relies on bringing in air, compressing it, superheating it, then letting it out the back of the engine. Since hot materials expand, it leaves at a speed considerably greater than the speed at which it entered, producing a force which then, by Newton's Third Law of Motion, pushes the engine forwards. This concept is called a ramjet engine. Given an constant source and concentration of fuel, a ramjet engine will accelerate until the forces of the air rip it into shreds. The trick is to thus limit the fuel that heats the air. Ramjet engines are extremely efficient, but will only work if you're already traveling at a certain speed roughly equal to half the speed of sound (around 620 km/h or 380 miles per hour), and are inefficient unless going even faster.

The question, then, is how to get up to that speed, which is where the turbine comes in. In the engines of the 'Verse, a turbine exists in each engine, powered electrically from the electricity generated by the fusion reactor (we'll get to that later). Anyways, once you have this turbine (basically a big fan) rotating, you can "suck" in air at sufficient pressure to run a ramjet-like process on it and do the same thing. The problem is that you can only go so fast before the force of the air pushing on the turbine rips it apart. Also, this requires a lot more fuel and electricity, and thereby should be used as little as possible. Once you get up to a sufficient speed, the turbine blades fold back or retract depending on the design and cease to turn. In theory you could reverse engineer a turbine to rotate at high speeds as an electrical generator (I.E. a windmill/wind power), but they're not designed to do so, and fusion power systems really negate the need. Either way, this is when the engine becomes a ramjet engine. The speed varies depending on the design and power of the turbine, but is usually around 600 miles per hour or 1000 kilometers per hour.

Once you pass Mach 1 or so (depending on design), forces of compressed air start bouncing around inside the ramjet engine due to the compression (it compresses the air to subsonic speeds). This can generate unwanted stress just about everywhere and eventually lead to all kinds of bad. The engines reconfigure somewhere within the transonic range to become scramjet engines (the method of how they reconfigure themselves depends on design, although the end products are similar if not the same). Scramjet engines are merely ramjet engines with a slightly different shape so as to allow supersonic air to pass through efficiently. They can usually get you up to Mach 28 or so (modern scramjets are capable of Mach 20-24, and it can be assumed that those in the 'Verse are constructed with better materials), which is more than enough to break the gravitational pull of the planet (you can orbit a planet from a low space orbit at Mach 22 safely, although of course scramjets don't work in space).

The final configuration of the engines of Serenity/Firefly ships is a more optional use, at least in atmosphere. When in the rocket mode, the front of the engine closes, and superheated gases (likely helium exhaust from the fusion generator, although some designs use a fission reaction on the hydrogen fuel) are shot out the back. The upside of this is that it'll work in unusual conditions, such as a vacuum. The downside is of course that it burns tons and tons of fuel very quickly and, when compared to the ramjet-family, is extremely inefficient. But it is useful to know.

Space Fight

Ah, finally, the most inexplicable topic of them all. The big problem with space travel is not losing energy to friction. It is quite simply the dog-gone massive distances involved. For short range travel in space (between moons, orbit, etc), one would use the reaction drives to save on energy (that will be expanded on in the next section). Reaction drives are simply your atmo thrusters in rocket mode. The problem is the amount of gas you're dumping into space while doing it.

The key thing about space flight in the 'Verse is that it is unneccessary to go faster than the speed of light: star systems are very close to each other. However, you still need to go pretty darn fast, and there's one way to due that: The pulse engine. Due to the gravity drives (in a process later explained as inertia reduction, see Gravity Drive), one can effectively create a localized field in which the speed of objects can be accelerated greatly. Detecting someone who is moving in another inertial reduction field is tricky, but can be done pretty well by computers, although it's not a perfect science. The key to it lies in tracking the fore and aft parts of electromagnetic radiation exiting the inertial field of the other ship. The pulse engine is basically a really big rocket that provides a huge burst of acceleration within this field. It is more efficient than the pod rockets because some of the excess heat is converted into energy to power the localized gravity drive fields (see Gravity Drive).

Gravity Drive

The gravity drive is the principle thing that makes the ship run. In addition to simulating the artificial gravity on the ship, it creates the pressure necessary to create the fusion reaction (see Fusion Reactor). This also sucks a huge amount of power, understandably. The gravity drive can be used to create the three assumptions (see Reference Tables), and is the key part of the ship. Without it, the fusion reactor will shut off, and that results in losing all power, air ventilation, and further systems. It is extremely difficult to repair, and almost impossible to cold start without a jump from another ship (most ships carry extra power cells that they can use to power it just in case: invest in these). The device works off the basic concept that quantum gravitation (gravity between atoms) is based on magnetic polarities. The hull of the ship is lined with electromagnets that, given sufficient power, can create an artificial gravitational field within and on the surface of the hull of the ship. The "gravity drive" in the sense that most people think of it is only a single major component of the entire drive (which is spread throughout the ship). This part is known as the gravity drive hub, and is typically seated nearby the fusion generator. It's primary purpose is to complete the complex mathematical calculations required to determine the pulses of energy that should be sent to each of the electromagnets throughout the ship. In theory, it can be engineered and modified to allow complete manual control of the gravitational fields in the ship, but most devices do not support this feature by default (for obvious security reasons). The largest electromagnet in the entire ship is attached to the pulse drive for the purposes of very fast travel, which uses inertia reduction to increase the local of objects. Look up Superstring Theory and Quantum Gravity for more.

To reduce the need for power and required size of the fusion reactor, the fusion reactor's electromagnet is the only one that is constantly on. The rest of the electromagnets (those set in the hull that make you walk, not float, for example) are only on about 1/4th of the time (depending, as always, on design). The magnets turn on for a duration of 250 microseconds, then off for a duration of 750 microseconds. The pulse effect is similar enough to real gravity to fool any living being into thinking that it is constant, while only using 1/4th of the required power. Newtech systems have managed to get this into even smaller ratios, and average about 1/8th to 1/12th on time. The current record of minimal power consumption in the 'Verse while maintaining 1G is 1/45th in controlled lab conditions. In atmospheric flight, the ratio usually normalizes more, going to ½ the time or 2/3rds on time to allow upside down flight and so forth when another gravitational factor is an issue.

As the gravity drive relies on electromagnetic waves, EM radiation becomes a huge issue. Most hulls have radiation shielding plated within them. Those that don't are short-range only and rarely have a pulse engine. Most of the radiation is in the exhausts of a ship, and enough of it is at a high enough frequency to completely strip an atom of electrons instantaneous. While flying in another ship's exhaust is a good way to remain hidden from heat sensing, it will slowly decay your hull, and eventually reduce your boat to a cloud of subatomic particles. How long a hull can hold out against this radiation depends on how much rad-shielding it has and design. A normal radiation suit or vac suit will not hold out long against this level of concentrated radiation, and shuttles, having much weaker hulls than boats, can't sit in there for long either. On the other hand, the radiation is a very good way to destroy the exhaust of a ship and not leave helium gas everywhere where you've been (which would be pretty easy to track with a decent computer).