Advanced Question How real is Orbiter?

[ToTheMoon]

The orbital mechanics, aerodynamics all of it, how real is it?

 

[Urwumpe]

The orbital mechanics, aerodynamics all of it, how real is it?

The orbital mechanics are very good, but not ultimatively real. It is maybe 1/50th of the accuracy of professional simulations per simulated day, but Orbiter also does this in real-time - it would be very painful for example to include all 2000 measured J-terms for non-spherical gravity, including the seasonal effects (GOCE even measured falling leaves in the autumn).

Orbiter does also not have variations in solar activity and its effects on Earths atmosphere. But thats OK, since scientists still have no good model of the solar activity cycles.

And Orbiter does not mind relativity... but thats a rather small factor unless you are close to the sun.

The aerodynamics depend on the spacecraft. The more the add-on does itself, the more accurate you can get. Especially, this also includes satellite aerodynamics. Practically Orbiter does everything it can do there satisfactory. It helps you a lot and is not standing in the way for more advanced stuff. A better general purpose API for defining aerodynamics would be nice, but isn't necessary. The rest is the job of add-on developers and framework developers.

The lack of weather and wind is a small factor... but its a spaceflight simulator. Space weather would be nice, but thats a job for add-on developers again.

 

[N_Molson]

GOCE even measured falling leaves in the autumn

Seriously ? :blink:

 

[SanderBuruma]

I would seem rather incredible if falling leaves would significantly affect the orbital characteristics of active satellites.

 

[Malky]

If you think not about single leafs, but quite big mass, which is in one moment moved two or three meters closer to center of Earth... That doesn't seem impossible to me.

 

[Urwumpe]

Seriously ? :blink:

Seriously. Only a minor factor among the changes in the seasonal ground water levels, freezing snow and changes in the atmosphere, but you can see it as well in the monthly data.

http://connection.ebscohost.com/c/a...-biomass-variation-geodynamic-effects-1982-98

Professor Reiner Rummel, one of the main investigators of GOCE, described the accuracy of the gravity sensor as such: Would a super tanker carrying the sensor collide with a snow flake, the sensor would notice the deceleration of the supertanker.

 

[SolarLiner]

but thats a job for add-on developers again.

Exactly. Orbiter is a fantastic simulator with spherical attracting bodies, but after that it really is it. Non-spherical gravity sources get "hacked" in.
But the modding possibilities are almost infinite. Look at the "Bump" add-on (abandoned I think now) that adds terrain and vessel collisions, Ourlex that added terrain way before the Orbiter 2015 beta, and of course the external graphics clients that helps the immersion quite a bit.

 

[Urwumpe]

Non-spherical gravity sources get "hacked" in.

Thats wrong - Orbiter supports simple non-spherical gravity sources since 2006. Orbiter 2010 added radiation pressure in its physics core and an example solar sail spacecraft to play with it.

 

[SolarLiner]

Thats wrong - Orbiter supports simple non-spherical gravity sources since 2006. Orbiter 2010 added radiation pressure in its physics core and an example solar sail spacecraft to play with it.

Yeah but my point by "hacked in" is that non-spherical objects acts like spherical objects; only the visual mesh is non-spherical.

 

[Urwumpe]

Yeah but my point by "hacked in" is that non-spherical objects acts like spherical objects; only the visual mesh is non-spherical.

That is wrong, you are mixing completely different things up there. You can have objects that have a special mesh that can be as non-spherical as you want.

And independent of that, you can define spherical harmonics for the gravity field, that allow you to put satellites for example into sun-synchronous orbits. You even have a very visible option in Orbiter for enabling/disabling it. Most have it disabled AFAIR, despite seeing Phobos as potatoe.

http://en.wikipedia.org/wiki/Orbit_modeling#Non-spherical_gravity

 

[SolarLiner]

That is wrong, you are mixing completely different things up there. You can have objects that have a special mesh that can be as non-spherical as you want.

And independent of that, you can define spherical harmonics for the gravity field, that allow you to put satellites for example into sun-synchronous orbits. You even have a very visible option in Orbiter for enabling/disabling it. Most have it disabled AFAIR, despite seeing Phobos as potatoe.

http://en.wikipedia.org/wiki/Orbit_modeling#Non-spherical_gravity

Well, TIL then. That makes Orbiter one level cooler to me!

 

[Keatah]

The precision of control of the ion thrusters aboard goce is likened to be the equivalent of a hypothetical control system that can vary the stationkeeping thrusters (of a supertanker) with enough discrimination so as to account for the impact of a snowflake.

I don't believe there are sensors capable of determining how much to adjust those thrusters. Just that they can be adjusted.

 

[alamat]

I would seem rather incredible if falling leaves would significantly affect the orbital characteristics of active satellites.

same idea with it