Relativistic Speed

Reaching the speed of light involves increasingly more energy because, as an object's speed approaches the speed of light, relativistic effects become significant. The closer you get to the speed limit, the harder it becomes to accelerate further.

We could apply a similar concept in SE2, just with a much lower speed limit: 300 m/s instead of 300,000 km/s. :)

I won't bother you with a detailed physics breakdown, but here's the basic idea. As you approach the speed limit, you need progressively more energy to keep accelerating at the same rate. At 0.5 of the speed limit, you need roughly 15% more energy; at 0.7c, around 40% more; and at 0.9c, around 130% more. The energy required approaches infinity as you approach the actual speed of light.

These are real relativistic values, although for gameplay we could obviously tweak the formula to better fit the intended flight model.

How Would This Work in SE2?

With a maximum speed of 300 m/s, you could accelerate normally up to around 150 m/s without noticing much difference. But as you approach 200 m/s, the energy cost would increase significantly. You'd need roughly 50% more energy to maintain the same acceleration, or, more practically, your ship would accelerate 33% slower with the same thrust. At 290m/s your acceleration slowes down a lot. Reaching 300 will be ofc impossible.

Gameplay Implications

Ships with higher T2M (Thrust to Mass ratio) and plenty of fuel could afford to reach higher speeds. Massive ships would generally avoid doing so to conserve fuel and energy.

This doesn't mean large ships couldn't go fast. It would be a trade-off between how much useful equipment, weapons, ammo and armor you want to carry and how quickly you want to accelerate and reach high speeds.

A large capital ship might rarely go above 200 m/s, while an interceptor specifically designed for speed could reach 290 m/s relatively easily.

Fuel and pursuit

Fuel reserves would become a much more important consideration. The faster you want to go, the longer you need to accelerate, and the more fuel you burn in the process.

This would give you a way to catch a fleeing target: either design your ship for higher speeds and make sure you have enough fuel left to sustain the chase.

It would also make changing direction at high speeds more demanding. There would be good reasons to slow down during combat and to set a maximum speed below 300 m/s when appropriate. See this topic for the reference.

No more situations where a small, speedy fighter simply can't catch a giant cargo ship. A cargo ship might technically reach higher speeds, but doing so would be expensive enough that its economically viable cruising speed could be closer to 150-160 m/s.

Returning fighters to refuel is suddenly a real gameplay mechanic. And they can restock ammo/missiles at the same time.

Speaking about missiles, or even custom torpedoes. There is now a clear reason why it is hard to escape chasing missile. It usually has a very good T2M helping it chase the target. However, if you have an agile fighter, you will have a much better chance to evade.

What About Jump Drives?

There's an elephant in the room: the Jump Drive. I won't address it here in details because it deserves its own discussion.

I'll just say that its combat capabilities should be toned down so different ship designs can have meaningful advantages and disadvantages when it comes to speed. A Jump Drive shouldn't be an easy escape button or allow ships to bypass an enemy fleet formation without meaningful risk.

Scientific Explanation

The 300m/s speed limit can be neatly explained through lore. It can be specific to the start system or due to alien activity. In any case, it has at least some scientific explanation and not just an arbitrary engine limit. The game will also teach people relativity while solving real gameplay issues.