[2.0.20] Wider space platforms are significantly slower than heavier ones.

[IsaacOscar]

My apologies if this is not a bug, but intended. I'm reporting it as the behaviour was quite surprising, and it depends on a complicated mathematical equation that might not be behaving as intended.
If it is not a bug, I would like to transfer this post to ideas and suggestions as the current behaviour is just totally strange, counter-intuitive, and makes the game too easy (as it's much easier to build skinny platforms than light ones)

What did you do?

I built the following two platforms on Nauvis:

heavy_platform.png (152.36 KiB) Viewed 651 times

wide_platform.png (3.32 MiB) Viewed 651 times

I used the map editor, both platforms have a signal thruster fueled by infinite pipes, and several guns to shoot asteroids.
They also have some combinators to count time and speed.
I then sent them both to Vulcanus.

What happened?

The first platform took 1:26.45 seconds to reach vulcanus, with a max speed of about 211km/s.
The second platform took 1:42.16 seconds, a max speed of 159km/s.

What did you expect to happen instead?

I expected the second platform to take less time, as it is much lighter. As can be seen in the bottom right of the screenshots right under speed, the first platform weigh 400 tons, but the second is only 62.

Does it happen always, once, or sometimes?

Always.

It appears the cause of the above is due to the complicated and very physically unrealistic equation here (https://github.com/wube/factorio-data/b ... s.lua#L513)

Code: Select all

space_platform_acceleration_expression = "(thrust / (1 + weight / 10000000) - ((1500 * speed * speed + 1500 * abs(speed)) * (width * 0.5) + 10000) * sign(speed)) / weight / 60"

As can be seen, it takes into consideration the width of the platform, which is a complete surprise as the game makes no hint of this nor do the FFFs (e.g. https://factorio.com/blog/post/fff-381). In particular, the above equation makes the width of the platform have a much more detrimental effect on acceleration, hence my second platform being slower (it is 14 tiles wide, whereas the first one is 8 tiles).

See 122365 for more of a discussion.

[boskid]

Does not sound like a bug, moving to Balancing.