Optimizing Atmospheric Entry Speed in Space Games

[DynV]

TL;DR Summary: A question about a game which gravity affect much of the game-play.

In a space game I'm trying to arrive as fast as I can on a low atmosphere planet. There's an autopilot to get me at low orbit but that would mean having a speed of zero compared to the surface I'm over if it let it on until completion. I tried disabling the autopilot part-way but if I do it too soon I overshoot the planet (of course if I do it too late it's wasted fuel but most importantly wasted in-game time). Is there a way to spot the maximum entry speed, or a bit slower than that? Please keep in mind the engines don't allow breaking, the faster the ship was, the longer it take to slow down.
I can change the camera angle in case I'd need to look for something that would be hard to spot if I only had cockpit view. There's also statistics for surface gravity and radius. I don't need precise calculations, if I can only eyeball ~3/4 of the actual maximum entry speed (that won't overshoot). Oh and my ship have heavy atmosphere shields so temperature won't be an issue for most planets.
I don't remember high-school covering gravity to the point that would begin to answer my question, so I used the intermediate prefix.
Thank you

 

[hmmm27]

If you're trying to land then you need either a seriously long runway (to land tangentially), or to turn the ship backwards to use thrust from the engine (to land radially).

 

[DynV]

If you're trying to land then you need [...] to turn the ship backwards to use thrust from the engine (to land radially).

The autopilot does that, but goes to a full-stop unless I interrupt it; too soon and it overshoot. I thought I brought that up in the OP...

 

[hmmm27]

The autopilot does that, but goes to a full-stop unless I interrupt it; too soon and it overshoot. I thought I brought that up in the OP...

You didn't mention whether you were trying to land or orbit.

 

[DynV]

You didn't mention whether you were trying to land or orbit.

I wasn't that specific but wouldn't that mean coming to a full-stop? It's for hovering, orbiting with thrusters assistance, since a real orbiting would be quite high.

 

[hmmm27]

If your craft drops below orbital velocity at whatever alitutde, then it will fall down, or require downwards thrust to maintain. If it's going faster then it will fall up.

 

[hmmm27]

Or, simply go right in at full Cruise and hit "Dock" just before you plow into the docking ring.

Or, take advantage of the advanced game functions and go in on autopilot, pre-ordering supplies and setting up trades through your space-phone, so you don't waste time on the ground going to shops, etc.

 

[DynV]

Or, simply go right in at full Cruise and hit "Dock" just before you plow into the docking ring.

The auto-pilot already does that, taking almost all the fuel to start, drift a large portion of the way, then slow down and usually ends with fuel right above warning level.

Or, take advantage of the advanced game functions and go in on autopilot, pre-ordering supplies and setting up trades through your space-phone, so you don't waste time on the ground going to shops, etc.

If I wanted to do that I'd play a GPL recreation of the game Escape Velocity, now I'm playing a GPL recreation of the game Elite.

I want to know at what point to drop autopilot when setting it to low orbit so it goes right below the speed it would overshoot the planet. I suspect (strongly) there's a way to eyeball it, that there must be something happening when the ship becomes slow enough to be "attached" to the planet gravity. Maybe I have to drop the autopilot to test that condition throughout the landing, maybe activating an upward or downward thruster does something more or less than the moment it "snaps" to the planet, and when that stops I can leave the autopilot off?

I can manually pilot the ship but it's inefficient, I either am too save and waste too much fuel slowing down, or overzealous missing the mark and adding an extra step to the path.

 

[Drakkith]

I suspect (strongly) there's a way to eyeball it, that there must be something happening when the ship becomes slow enough to be "attached" to the planet gravity.

Assuming the game is using realistic gravity, then no, there is no visual indication that you've gone from an open orbit to a closed orbit (being 'captured' by the planet). You'd have to do the math each and every time you want to slow down unless you're always coming in at exactly the same speed and stopping at the same height above the surface, in which case you could roughly 'eyeball' it after getting some experience.

Unfortunately I don't know the mathematical details, though I expect it to be very complicated with integrals and other nasty stuff.

 

[DynV]

I don't know the mathematical details, though I expect it to be very complicated with integrals and other nasty stuff.

I think it's in there https://github.com/pioneerspacesim/pioneer/blob/master/src/Ship.h and that's just the header.