About atmospheric flight

[testadilegno]

Dear all,
I'm a long time 'lurker', having discovered this project around alpha 6 or 7.
I have started to follow you more frequently in recent times, and I was wondering if I can contribute a little:
I'm not a very experienced programmer (especially in C++), but I'm a physicist, so I guess I can lend a hand with physics and math stuff.

Now, on the topic.
I've seen here and around that there appears to be some interest in a more detailed model of flight.
If you feel that this could be a useful improvement, I could have a look and see if there is a simple way to add in a reasonably realistic atmospheric flight model.
Let me think what do you think of it, and if there are any ideas/wishlists/resources/etc that have been discussed before.
I'll start first reading some papers, studying and writing down stuff, and come here when I have done my homework.

Finally, a technical question: I had a look at the code, and I guess that DynamicBody.cpp is the file where you apply forces on the ships (am I right?).
There I have seen the code for atmospheric drag... I could start hacking on that.

Best, and thank you for your efforts,
Alessandro

[robn]

Finally, a technical question: I had a look at the code, and I guess that DynamicBody.cpp is the file where you apply forces on the ships (am I right?).
There I have seen the code for atmospheric drag... I could start hacking on that.

Correct. A DynamicBody is one that can move freely and have forces applied to it. Conversly, a non-dynamic body is something like a planet or space station, which usually has fixed velocity and rotation and can't have additional forces applied to it (we say its "on orbital rails").

Welcome :)

[FluffyFreak]

That would be very welcome and we can help out with the C++ side of things :)

[Marcel]

I have a wish, and it's probably a big one. I wish that the aerodynamic characteristics of a ship would be consistant with its form. Maybe a few tables and you pick from the closest match. Some of the ships would have to travel at aircraft speeds through an atmosphere and some could do mach 20 as a result of their hull designs. A ship with wings would glide much better than a pointed brick, but the wings would add dead weight outside an atmosphere. An atmospheric shield generator could still be purchaced to improve performance. It could use the new shield mesh which might be useable as a simple aerodynamic model. All you have to to is write a wind tunnel simulator and... well I said it's a big one!

[impaktor]

Malabar and Wave aught to behave very differently in atmospheric flight. I think I discussed this on IRC a few days ago, so it's on the minds of others as well.

[testadilegno]

I had in mind something among the lines you have pointed out.
I imagine having a table, or a "per model" set of parameters, that could be used to calculate the forces acting on a ship in the atmosphere.
Since I had a very positive feedback (thanks!) I'll start working on that, and I'll keep you informed of how things develop.

In short, I'd like to follow these two guidelines:

• Reasonably simple code: I don't think it will be useful to add in a "flightgear"- or "orbiter"-like physic model. Also, I wouldn't be able to invent and program it ;-p
• Simple workflow: I would expect that it should not be too hard to add in new "parameter values" for new ships, when new models are done.

One thing that we have to consider, game-wise, is the fact that the engines on the ships are extremely powerful. We don't really need wing lift to fly. There should be other reasons to chose one shape or another:

• Damage sustained by flying at high speed? (Imagine taking off with the DSM like an apollo rocket... It looks like it would start loosing pieces at 200 km/h...)
• Noise? (Fines if you fly fast above cities?)
• more advantages/drawbacks

In this view, I was thinking that the "atmospheric shielding" could be active during different stages of flight (takeoff, reentry, high-mac cruising, etc), or one could fit different shields for different purposes: e.g. a "reentry shield" just to land on planets, and a "high-mac" shield to be able to fly fast in the atmosphere even if your ship is shaped like a brick. Maybe a wave wouldn't need it, and a DMS would.

Anyway, I'm off to work now, please keep commenting/criticize/give advice/etc :-)

[Nyankosensei]

Sonic cone at mach1 ?

i don't think is a good idea add vne to the ships becouse that make impossible fuel scoop on gas giant, but a better friction inside atmosphere can be usefull for reentry

[impaktor]

Sonic cone at mach1 ?

i don't think is a good idea add vne to the ships becouse that make impossible fuel scoop on gas giant, but a better friction inside atmosphere can be usefull for reentry

That's something I haven't thought about. It would be a shame if one could no longer fuel scoop.

But atmosphere could affect top speed, course changes, and damage from friction if no atmo. shield.

[FluffyFreak]

In short, I'd like to follow these two guidelines:

• Reasonably simple code: I don't think it will be useful to add in a "flightgear"- or "orbiter"-like physic model. Also, I wouldn't be able to invent and program it ;-p
• Simple workflow: I would expect that it should not be too hard to add in new "parameter values" for new ships, when new models are done.

I've thought about this in the past and looked into it a bit, the simple reason for atmospheric flight is that you want winged bodies like the wave to handle like an aircraft in atmosphere with banking, climbing, diving etc. The power of the engines is almost independent of this because you want to be able to do something approximating that even at very high Mach values as you slam through a Gas Giants atmosphere :)

Likewise you expect slippery shaped ships to have less drag. The wave/kanara should need less power to travel at high speed through a planets/Gas-Giants atmosphere meaning they use less fuel, whereas a DSM should be brought too a crawl by it's drag making scooping an atmosphere difficult and travelling through atmosphere too a station slower and less efficient.

Marrying a simple model of lift & drag to the engine would be a great start and give us about 70% (guesstimate) of what people actually say they want.

There are two tricky times in the flight though:
[*] On entering the atmosphere as it's blends from 100% Newtonian physics into the atmospheric flight mode,
[*] Coming into a hover to land at a station or on the ground.

Those times are going to be especially hard for the existing autopilot to understand, I guess we'll just have to work around that somehow.
There are example of other open source autopilots for games and remote control/drone aircraft we can probably look into later on.

[baobobafet]

Large wing craft should be more fuel efficient for delivery of payloads to and from orbit - making them logical choices for work in atmospheric environments.
Of course that might imply some form of runway for take-off and landings to take full advantage of the increased lifting capability.
The engines on such craft could be minimaly powered in order to save weight(allowing more cargo). This could also allow for economically priced smaller and low power winged starter ships to carry more payload on take-off and landing. Unpowered gliders could even be practical for cargo traveling one way from orbit to runways on the surface.
- Although that might require some sort of in low orbit mooring system for large wingspan craft.

A buoyancy model for lighter than air atmospheric type craft would make for a nice addition as well.