What ships do need more hyperdrives ?
No ship 'needs' multiple hyperdrives, as hyperdrives mostly don't stack with one another. The important things to look at on a hyperdrive are its speed and its energy requirement. Warp Bubble Generators require 132 energy to operate at their full speed of 2000, which makes them incredibly inefficient because it means you need at least three space reactors in order get the full speed, and that speed is very low to start with (just as an example, if you design a ship with a Gerax hyperdrive and give the hyperdrive full power, the ship will have a higher hyperspeed even when out of fuel than a ship with a fully-powered Warp Bubble Generator at full fuel will, and it's faster by a factor of more than two).
As for why I said that hyperdrives 'mostly' don't stack with one another: a design with two different hyperdrive components (i.e. Kaldos + Equinox, not Kaldos + Kaldos) will result in a design which effectively has a single hyperdrive with the following characteristics:
1. The hyperspeed energy requirement will be equal to the maximum energy requirement of any hyperdrive component carried by the ship.
2. The time required to initiate a jump will be equal to the minimum jump initiation time of all the hyperdrive components carried by the ship.
3. The hyperspeed will be equal to the maximum hyperspeed of the hyperdrives carried by the ship.
4. The size requirement of the effective hyperdrive, as you might expect, is equal to the sum of the sizes of the hyperdrive components carried.
Thus, a ship with two hyperdrive components operates as though it has only one hyperdrive component which combines the best hyperjump-related aspects of the drives carried but requires the power of the most power-hungry drive carried. As a result, if you're going to combine any two hyperdrive components, you're better off going with Kaldos + Equinox, if both are available, than with any other pairing, as the Kaldos drive is the drive which sets the energy requirements in that pairing (except at the final upgrade of the two components, when they have equal power requirements) and the Equinox drive is faster than the Calista-Dal. The Gerax and Calista-Dal drives are reasonable candidates if you don't yet have the Equinox drive. Other potential combinations tend to offer too little improvement for the cost (e.g. Equinox + Calista-Dal saves you one second of jump initiation time off of about 12, while Torrent and Velocity drives already combine a similarly high speed to the Equinox drive with a similarly fast jump initiation time to the Kaldos in a single component).
What max range is possible for hyperdrive or is this not important
Maximum theoretical ship range depends on a combination of several things: the speed and energy requirements of your hyperdrives, your design's static energy requirement, the number of fuel cells carried by your design, and your reactor fuel efficiency. However, maximum theoretical range is largely irrelevant using any hyperdrive other than Warp Bubble Generators, as it's trivial to obtain ranges of about 5 sectors and fairly easy to obtain ranges in excess of 10 sectors with just a few Standard Fuel Cells, using Fission Reactors and Gerax Hyperdrives or higher-tech equivalents. Warp Bubble Generators, however, suffer from a combination of issues that make it difficult to create designs with more than perhaps two sectors range.
The first issue is that the Warp Bubble Generator requires lots of energy and has a low maximum speed. This combination of facts means that any jump using a Warp Bubble Generator is very fuel-intensive, as the hyperdrive energy use is in units of energy per second and the speed determines the duration of the trip. If we assume that you want to travel 1 system diameter (about 50,000 range units, if I remember correctly), a fully-powered Warp Bubble Generator will require 25 seconds plus the jump initiation time to make that jump. A Gerax hyperdrive will only require about 4 seconds plus its jump initiation time to make the same jump. The basic Gerax hyperdrive requires 78 energy per second from the reactors when fully powered, whereas the Warp Bubble Generator requires 132. Ignoring the energy cost of the jump initiation, this means that the Gerax hyperdrive will consume 312 units of energy over the course of the jump whereas the Warp Bubble Generator will consume 3300 units of energy. Assuming that you're using the same reactor to power both designs, this means that the Gerax Hyperdrive will use less than one-tenth the fuel that the Warp Bubble Generator will use to make that one jump, and the Gerax hyperdrive will get your ships there more than 6 times more rapidly.
The second issue that the Warp Bubble Generator has is that you likely only have the Basic Space Reactor available to power it. This reactor is the least fuel efficient reactor in the game, consuming 4.11 units of fuel per thousand energy produced, and has a very low output of 46 energy per second. Its only redeeming qualities are that you start the game with it and that it's about average size for a reactor. Just to fully power the Warp Bubble Generator, you need at least three of these things (because you must have an excess reactor output of 132; three Basic Space Reactors have a total output of 138, so it's fairly likely that you'll need a fourth, depending on your design's static energy requirements, if you want to fully power the Warp Bubble Generator), which costs you the 54 size units used by the reactors (note - you can often obtain superior range by NOT fully powering the Warp Bubble Generator than you can by fully powering it, because you can fit three more fuel cells into the space that would have held a reactor, though this makes an already-slow hyperdrive even slower).
The third issue goes hand in hand with the second issue - you're probably only using the Warp Bubble Generator while you're restricted to small ships, which greatly limits the amount of space you have to toss in reactors to power an inefficient hyperdrive. This means that your designs will often not fully power the hyperdrive in order to squeeze whatever else you need on the ship into the limited available space, which makes the ship slower and thus makes the design less fuel efficient (note that the hyperdrive component itself has a fixed fuel requirement for a given jump distance, as if you reduce the supplied power by X% you have also reduced the travel speed by X%, so any hyperdrive requires only a fixed amount of fuel for a jump of any given distance; it's the added cost from the static energy requirements that drive the fuel efficiency down as you reduce the power supplied to the hyperdrive below its requirements).
A further issue is that the fuel cells available at game start are rather lacking in capacity. This means that you might require 5 or 10 fuel cells (30 to 60 size units) just to obtain a 1-sector range on the Warp Bubble Generator, which combines with all the other issues with space requirements to restrict the operating range of an early-game design. Simply replacing the Warp Bubble Generator with a Gerax Hyperdrive and changing nothing else about the design can quite easily improve the theoretical range by a factor of five or more.
There are two different types of engines in the list you put together - maneuvering engines (directional thruster, thrust vector, swift vector, multi vector), and main thrust engines (ion thruster, proton thruster, acceleros engine, quantum engine, vortex engine, starburner engine, turbothruster). Both of these are used only while the ship is traveling at impulse/cruise/sprint speeds. Maneuvering Engines govern how rapidly the ship turns, in some formula determined by the total thrust of the maneuvering engine components and the total size of the design, though I cannot tell you the exact equation, and increase the static energy requirements of the ship if I recall correctly. Main thrust engines determine the cruise and sprint speeds and the energy requirements for impulse/cruise/sprint speeds; the cruise and sprint speeds are determined by summing up the total thrust at that thrust level (so if I have 5 engines that each give a cruise thrust of 560 and a sprint thrust of 600, I have 2800 cruise thrust and 3000 sprint thrust) and dividing that resultant thrust by the total size of the ship (continuing the example, if I have a size-400 ship, those five engines will give my ship a cruise speed of 7 and a sprint speed of 7.5, which I think rounds to 8), while the power requirements for each speed level are determined by the sum of the energy requirements for each thrust level determined by the drive component. Main thrust engines and maneuvering thrusters DO NOT affect hyperspeed, which is determined only by the hyperdrive and by how much power you can give it. It is advisable to keep the cruise speed above 12 for any design you have, as otherwise your ships will most likely be unable to catch up to a planet if they run out of fuel (all ship movement speeds except, I think, impulse are divided by three when the vessel is out of fuel, though I don't believe turn rate is affected; this is what gives me the ability to say that a fully-powered but out-of-fuel Gerax drive design is still more than twice as fast as a fully-powered fully-fueled Warp Bubble Generator design, as the Gerax drive's 12500 speed becomes 4166 or 4167 when out of fuel, as compared to the Warp Bubble Generator's best possible speed of 2000).
Ships will use standard engines for any purpose that requires them to remain below lightspeed - combat, short-distance travel (if there's a hyperdrive equipped, 'short distance' basically means that if it's further away than the other side of the planet that your ship is at, you're going to take a hyperjump), or movement in a hyperspeed-denied area (a couple story locations, or within range of a ship with an active hyperdeny component) - and hyperdrives for anything else, if they have them. This is because even the slowest hyperdrive is likely to reduce the duration of the journey by a factor of at least 10 (it's very rare to have a design with a cruise speed in excess of 40-50, and you will most likely be able to attain a speed of at least 400 on the Warp Bubble Generator even if you don't change the design to free up some reactor output, as that speed requires only about 27 excess reactor output and if you don't have at least that much, your design probably doesn't have the power to do much of anything worthwhile anyways). Cruise speed is the normal sublight travel speed, impulse speed is used while docking with stations or planets, and sprint speed is used while moving to engage a target and perhaps while attempting to flee, though cruise speed is the speed used for most of an engagement if I'm not mistaken.
< Message edited by Aeson -- 7/4/2014 9:48:45 PM >