This is where things start getting really theoretical.

Pushing past lightspeed is more than just pushing past lightspeed: it's pushing past the constraints of time. After all, there isn't really any point in giving Beyond Lightspeed its own post if we're only looking at going 1.01x or 1.25x or even double or triple. Beyond Lightspeed means you can jump into hyperspace and cross the galaxy in just thirty minutes (according to Star Wars, anyways), making the distance between worlds akin to the distance between your house and the local 7/11.

Honestly, that kind of thing has always bothered me in Star Wars. Starships are presumably massive investments that most farmers spend lifetimes saving up to buy, and hyperdrives doubly so - yet every measly outpost in the Rebel Alliance has dozens of hyperspace-compatible X-Wings ready to go at any moment. You hear about how the protagonist wants nothing more than to finally leave their stupid planet, and then suddenly gets their hands on ship after ship after ship throughout the story. The galaxy becomes tiny and limited: more like a city than a massive span of thousands of stars and worlds.

The Milky Way galaxy is over a hundred thousand light-years in diameter: 52,850 from the center out. There's probably still light from the Earth from the ice age that's finding its way to the other side right now. Going at five times the speed of light doesn't shrink the galaxy to the size of a city. Going at five hundred times the speed of light barely makes it feasible to cross with cryosleep and a ridiculous amount of investment. And at the point that you're saying you can go a million times the speed of light, then you'd literally be hitting so many stars on your way through - I can't even begin to express how dead you'd be.

So basically we come to the big question:

What's the best speed for FTL?

As I see it, there are several issues to take into account:

• How the heck are you supposed to navigate at significant FTL? The average distance between stars in the Milky Way is 5 light-years; at 3,000,000x you'd be hitting a star roughly every second, which is a quick and easy way to get yourself mcslain. Does that mean you can get up to 500,000x speed and navigate by the minute? How much energy is required to change the trajectory of a ship traveling at such speeds?
• How does one change directions at FTL? And in space, for that matter? The on-board computers in Star Wars chart out lightspeed paths automatically, creating a rough series of lines and stops to avoid death traps and reach destinations that can't be accessed by straight lines. They never bother to show the ship actually navigating itself through hyperspace though, which has always bothered me. Presumanly you'd have to make several stops mid-hypersepeed to avoid certain doom, jumping in and out at various locations to reach your destination.
• At what point does FTL become too slow? That is, how much faster than lightspeed does it have to be to effectively mitigate the problems of traveling at c? Going at 1.25x doesn't exactly open up the galaxy for a daytrip. What's the highest minimum speed for FTL to actually start working?
• Basically: What's the minimum speed and what's the maximum speed? And how do you navigate?

Bottoms Up: How Slow can you Go?

Once again, the average distance between stars is 5 light-years. That means at the speed of light, it's gonna take you five years to get from one star to another. This is not fun.

At roughly 500,000x the speed of light, it'll take you just minutes to get from one star to another. This probably isn't good for a minimum speed. At 100,000x speed it'll take you on average five minutes between each star; at 50,000x, ten minutes. These are all still quite large numbers, because - after all - lightspeed is pretty dang fast.

At less than 10,000x speed it'll take you an hour to get from star to star. At 5,000x you make a day of it. These are still big numbers. 1,000x it's a road trip, 500x you need to stop and get a hotel.

100x speed means it's a business week to get from one star to another. That means it'll take a month to cross through several districts and get to someplace more distant. In terms of the scale I've been writing for my sci-fi novel, this seems like a good model speed for the likes of business ventures and military expeditions. If time isn't a big constraint, then 100x is a good speed for saving money and getting stuff done. They'd be akin to voyages from England to the New World; longer ones would be like going from Europe to India.

It's effectively a step down from the industrial scale of Star Wars, which is akin to a galaxy-wide modern-day consumerist economy - think of it as how we can practically access the entire world at any given moment for enough money, and how it just takes days for Amazon to get us our stuff. In my particular story, space travel is still in a pre-industrial phase (even though it's still massively beyond the level of industrialism in reality). Many individuals do have access to massive FTL speeds, but for the most part it's significantly more cost-effective to just take your time on these things.

Obviously 100x wouldn't be the absolute absolute minimum speed. For local travel you could go at 1.01x - 1.25x and jump between planets to go hang out with your friends over the weekend, and perhaps if you don't have the money you could go at somewhere around 10x to spend a little over a month moving to the next star over. Regardless, at a practical scale, I think 100x makes for a very friendly number - so let's go with it.

Head over Heels: A Need for Speed.

30,000,000x speed is the right-away "too fast" bar, because at that speed you'd be hitting a star approximately every second.

We established earlier that roughly 500,000x will make star-to-star travel take about a minute each. I don't think that's a good high limit. If 100x speed is akin to an overseas voyage, then I want the maximum speed to be akin to an airplane ride. A jump from one star to another will take just an hour or two, while crossing the galaxy would take a day or two and multiple flights. It takes a commercial airliner to cross the globe in just under 48 hours, though that's around a globe rather than across a disk (I'll be going by radius rather than diameter to determine the max speed, then). 52,850 light-years is 19,191,700 light-days, so you'd have to go at roughly 9,595,850x lightspeed to cross it in a couple days.

That's obviously an issue - we'd still be hitting a star every few seconds. Clearly we need a different parameter.

Perhaps it's not a great idea to compare the galaxy to the globe. It's hard to express just how big it is. And besides - it's not like it's taking months for the 100x speed starships to cross the entire thing. Rather than looking at the galaxy as a whole, we should be looking at individual star-to-star travel in the same terms. From one star to another is like crossing an ocean: meaning for budget voyages it'll take a week or two, and for rich people trips just a few hours. It takes a plane roughly 3 1/2 hours to cross the Atlantic, so we'll set that to our goal for our top speed.

5 light-years times 365 = 1825 light-days, then times 24 makes 44760 light-hours. 8,760x speed would mean that you cross in just an hour, so our upper limit would be about 2500x.

So there we go. 100x - 2500x as our best average. The absolute slowest FTL would be just over 1.01x (for local system travel), while the absolute fastest would be upwards of 2900x (based on the fastest crossing of the Atlantic by plane coming out at about 3 hours).

Anyway

Navigation: How to Not Die in Space, For Dummies

So if you're going really fast, then it becomes remarkably easy to hit things - and in space, when you happen to hit things, you often wind up dying.

If you're going too fast, then there's really nothing you can do to avoid hitting space things. Yeah, there's a lot of space in space, and hitting things is kinda difficult - but it's like going on a windy mountain road in the middle of the night at fifteen over without your brights on. The chances of skidding over ice and hitting a deer just get higher and higher the fewer precautions you take - except in this case, the deer is an entire planet and the ice is a gravity well.

So how do you dodge a deer in space?

The faster you're going the harder it is to slow down - at least, that's how it works in normal physics. Fortunately for us, we aren't obeying the laws of normal physics at all - we're going upwards of 3000x the speed of light here. Clearly we're thinking with portals here.

Basically: if you can go past the speed of light and destroy all physics, then you can suddenly drop to speed 0 and destroy all physics.

So how do you know where the deer are in space?

Google maps, of course. We'd need to have charted the entire galaxy. All of it. The archives cannot be incomplete - this would be bad. In addition to having charted it, we'd need to have some way for every FTL-capable ship to access it all: a prospect that gets more and more complicated the more you have to consider.

Basically: we need some kind of supermapping supercomputer with really good FTL wifi.

What if there's a brand-new deer in space?

The last thing you want to encounter on your space daytrip is a rogue planet slamming into you mid-hyperjump. However, if there's FTL wifi, then it should stand to reason that there's also FTL radar. Your ship would likely be able to drop out of hyperspace in emergencies so that you don't hit any space deer.

Basically: space radar.

Hey, how are we doing FTL in the first place anyways?

Tune in next time for... uh.... the next thing!

Bye!