Ah, the ripple drive. The staple of FTL travel throughout the galaxy. From the smallest inter-system freighter to the largest military cityship, practically all FTL-capable ships have ripple drives even if they also have another drive as well.
These are the only drive on the Legacy Flint-Vasa aside from thrusters and other sublight manuvering systems. Ripple Drives can be used for sublight speeds in addition to FTL speeds, however they are unsafe to use in proximity to other craft or space stations.
The basic principal is that Ripple Drives send energy through exotic matter to distort space in a localized way around the ship. For small ships, the Ripple Drives extend along the sides of the ship, generally for about 75% or more of the length of the ship, in order to distort space all around the ship. For larger ships, there's usually “ripple drive extenders”, which are special pods that pull the distortion field from near the drives (usually in the aft of the ship) and tug it more forward to help surround the entire ship.
This distortion field creates an interesting situation; the ship isn't actually moving. Rather, space is moving around the ship and the ship is being slid along for the ride. When traveling faster than light, space around the ship travels faster than light, and the ship is practically stationary for all intents and purposes. It cheats relativity out of causing time dialations; so the crew live and age aboard the ship at the same rate they would outside the ship.
There are also a few other beneficial side effects that we will get into in more detail below.
The maximum speed for a Ripple Drive is about 0.7 lightyears per hour on a well tuned military ship for short sprints. Typical large ships cruise around 0.5 lightyears per hour, and may burst upwards of 0.65 lightyears per hour. Small ships are often restricted to more around 0.25 lightyears per hour or less due to the limited power generation capacities.
So what does it “feel like” to be traveling FTL with a ripple drive?
Not like much. As noted, the ship isn't moving, but rather the localized space around it is, in effect making the ship a stationary frame of reference. The primary oddity is a lack of stars; looking out the window will reveal a purple-ish swirly haze around the ship, and no stars. Some people find the haze beautiful, some people find it a little disturbing. The haze is very wispy and it is quite easy to see there's nothing beyond it.
Ripple Drives work by churning up the space around the ship. As such, anything that enters the field of churned up space around the ship will, itself, get churned up. For example, a shuttle attempting to leave the ship while the ripple drive is active will likely get torn to pieces. If the ship is carrying a large piece of bulk cargo (for example, a section of a space station) and part of that cargo touches the ripple field, then the part of the cargo that touches the ripple field will abruptly be going FTL while the part not touching remains stationary.
At best, the cargo will likely be ripped off the ship and destroyed. At worst, it will collide catastrophically with the ship and nobody will survive.
And thus, one of the cargo management team's most important duties is to monitor bulk cargo and make sure that it stays secure and safely contained within the ripple field.
As noted above, the field a Ripple Drive generates is effectively impenetrable to most objects. The ship doesn't actually have to move in order to have the ripple drives turned on, so a ship can sit there with the drives churning and use them as an effective shield against kinetic threats.
That said, there are a number of threats that can penetrate a ripple field. A large enough explosion can transfer some energy through the ripple field. A missile designed to disrupt or merge ripple fields with the target ship can potentially penetrate it. And some energy weapons are effective through ripple fields.
And of course, an object sufficiently large and sufficiently well aimed could come through the ripple field as debris that would hit the ship within the field like a shotgun blast. That, or just “bad luck” with a smaller object, as anything that gets into a ripple field could have some fragmentation that gets to the other side of it.
As such, the most effective way to use Ripple Drives as a defense is to perform a “Ripple Flare”. This is simply making the space distortion field around the ship larger; it requires more energy, in fact, a rather large dump of energy into the system. And it is rather hard on the engines as a result. But, increasing the size of the ripple field for brief moments can make it more likely the ship will shrug off what might otherwise be a devastating attack.
Often, the ship's computer will be used to track incoming projectiles or likely weapons fire from enemies and be used to perfectly time Ripple Flares to destroy incoming attacks. The flaring of the drives will eventually burn something out, though, so it is not a defense with indefinite endurance.
You may wonder, what happens if two ships collide while traveling FTL using Ripple Drives.
The answer: not much. One of the key principles here is that there are no inertial forces at play; if a Ripple Field is disrupted, the ship just harmlessly stops in place wherever it happens to be. And what can disrupt a Ripple Field? Another Ripple Field!
Ripple Fields rely on a carefully choreographed series of 'ripples' along the hull of the ship, similar to oars on a galleon. Two Ripple Fields coming in contact with each other is like the oars getting caught in something, except the 'boat' in this case has no inertia, so instead of continuing to sail forward, it just stops.
So two ships colliding at FTL will just harmlessly both come to a dead stop, albeit rather scary close together; how close together depends on the sizes of the ships involved, as the size of the ship determines the size of the ripple field around it. Small ships could easily as close as 5 meters apart; large ships perhaps 20 to 40 meters apart. Close enough that the pilots should coordinate activity to make sure there is no collision. This is one of the primary jobs of the pilot “babysitting” the ship under FTL.
Real life aircraft follow radio beacons as waypoints, and thus there are flight paths in the sky; starships do the same thing, except they go from Comm Relay to Comm Relay in order to pick up communication during a voyage. As such, most ships fly more or less the exact same path as they travel from port to port; this is how come, even though space is big, these 'collisions' are not uncommon. How common they are depends on the trade lane in question; obviously, the more congested, the more likely they are to have collisions.
As such, the more densely populated trade lanes have coordination to try and make sure the different paths don't intersect; it's a bit like Air Traffic Control, giving each ship some spacing in 3-D space to try and make sure it doesn't hit another. Such a system is not usually deemed necessary on less populated routes.
Okay, so we've covered ripple-on-ripple collisions. What happens if a ship going FTL collides with something not going FTL?
Interestingly, not much; FTL objects can interact with FTL objects, and non-FTL objects can interact with non-FTL objects, but generally speaking an FTL object will pass through non-FTL objects as if they aren't there. At least, to a point; certain cosmic bodies have energies, densities, or other qualities that can cause FTL interactions. For instance, many stars and some planets; it is therefore considered more safe to not chance it rather than to try and pass through them.
If an FTL object were to try and pass through a planet, and fail, then it would emerge stationary and likely within that planet's atmosphere. It would then most likely dead-drop to the surface. Thus, you can't take an FTL run at a planet as a form of attack; depending on many factors, your ship could emerge high enough to burn up and break apart harmlessly, or close enough to the surface to only do minor damage.
In the 'best' possible case, your ship will fall on something on the ground and explode violently due to the various volatile components of a starship; but franky, bombs generally do a much better job and are far cheaper. The ship is becoming a weapon in spite of FTL, not because of it; you could do the exact same effect with more precision and accuracy without trying to involve FTL travel.
A more likely scenario is for two objects to try to leave FTL at the same place at the same time. In such a case, it isn't really an FTL collision, but more or a 'same place at the same time' collision. The answer here is simple; when coming out of FTL, continue to use the ripple drives to move away from the system/com relay's 'entry point' at sublight speeds until you are within the system's 'safe zone'. Each populated system and comm relay has a designated 'safe zone' under which no ship will run their ripple drives; this provides plenty of room for ships to come in, and use their ripple drives as 'bumper car' bumpers, sort themselves out, and then approach using local flight control.
So is there a way to knock a ship out of FTL for whatever reason? Piracy being an obvious one. The answer is, of course, yes: all you need is a device that's generating a Ripple Field, preferably over a large area. A bit like a fishing net, where the biggest constraint is the size of the net requiring a good deal of energy to keep up. Since ships tend to go along trade lanes, a pirate can take a reasonable guess as to where to set up their net.
However, more often, there are logical 'short cuts' which can be taken. Let's say you're going from point 'A' to point 'D'. Obviously, the fastest way to go is straight from A to D; however, the trade lane goes through points B and C which have comm relays or other populated systems. There's not enough traffic straight from point A to D to warrant the infrastructure of comm relays, etc.
Thus, a pirate can set up a net on an 'unofficial' trade lane between A and D and hope to get lucky.
This said, the chance that a ship will happen to fly through the relatively tiny area your ripple 'net' can cover is pretty close to zero; space is a big place, and setting up a large net is beyond the capability of most pirates. That's more of a job for a whole military task force; a CSS City Ship would have sufficient power generation to set up a huge net to cover a lot of area, but a pirate wouldn't have that kind of budget.
So, what a pirate is better off doing, is operating near a comm relay. 'Throw the net' over a target ship by moving your ripple net around the ship quickly as it emerges to use the relay, and jam comms. And thus, this is how most pirates operate. Or gathering intellegence; if they know a ship is going to take a short cut, or have some way to influence ships considering a short cut, they may know quite precisely where to set up a net.