How low is atmospheric flight?

[THobson]

I have a tourist that wants an atmospheric flight over Eve.  He was unimpressed with a fly past at 85km.  How low do I need to go to satisfy him?

[Tex_NL]

AFAIK your Ap must be inside the atmosphere. For Eve that means below 90km.

[MaxL_1023]

Atmospheric flight is any travel within a planetary atmosphere except for escape trajectories. Basically, you must have a closed orbit at some point within the atmosphere. 

If you were not captured by Eve and just flew past into a solar orbit you will not receive credit for the mission. Thankfully, it only takes a couple hundred m/s of delta-v to get from a very high elliptical orbit back to Kerbin, so try burning a bit at perapsis to close an orbit. If you have a heatshield, you could lower your Perapsis to 75km or so and probably aerobrake into orbit.

28 minutes ago, Tex_NL said:

AFAIK your Ap must be inside the atmosphere. For Eve that means below 90km.

Your AP can be anywhere, as long as it is within the SOI of the planet (non-hyperbolic). I usually get the achievement when aerobraking or re-entering Serran or Laythe (using the New Horizons mod).

[THobson]

Thanks.  I flew past (on an escape trajectory)  at 85km and am now in orbit at 700km.  I only have a couple of Nerv engines so not much use in getting me out of trouble while in the atmosphere.  So if I now dip down again to 85km that looks like it should be okay.  It seems odd though 85km on an escape trajectory is not atmospheric, but while in an orbital trajectory it is.

[Snark]

47 minutes ago, MaxL_1023 said:

Atmospheric flight is any travel within a planetary atmosphere except for escape trajectories. Basically, you must have a closed orbit at some point within the atmosphere. 

If you were not captured by Eve and just flew past into a solar orbit you will not receive credit for the mission.

+1 to this.  You need to be in atmosphere while traveling at less than escape velocity.

Note that this "rule" applies not just to contracts, but to science instruments as well.  For example, if you're going through Eve's atmosphere but are on an escape trajectory, then any measurements you take with your science instruments will count as "from space near Eve" rather than "from Eve's upper atmosphere."

[MaxL_1023]

I think it might stem from the rails system - a craft on an escape trajectory will usually survive an upper-atmospheric passage afaik (when not loaded by physics) while something in a closed orbit would be be auto-destroyed simulating re-entry. I have had situations where I lost a craft on a hyperbolic re-entry (underestimated the heat loads compared to orbital speed) but some pieces with command pods (those mechjeb modules are nearly indestructible) were still intact when I went to space center. Even though the pieces should logically have either landed,crashed or burnt up (nothing makes it back into orbit from a 20km Kerbin PE) they ended up staying on their escape trajectory with no atmospheric effects applied when out of physics load range.

 

[Snark]

27 minutes ago, MaxL_1023 said:

I think it might stem from the rails system

I don't think that's it-- all of this applies only to the craft you're currently flying, which is never on rails.

I've always assumed that Squad did this deliberately for game-balance reasons, i.e. so that you can't get a "free" accomplishment of being "in atmosphere" just by doing a high-speed flyby that grazes the atmosphere.  Requiring a captured orbit means you have to be "honestly" in the atmosphere.

Just a guess on my part, though, no actual knowledge.

[MaxL_1023]

I am not sure honestly, but something is odd with the way craft on rails behave. They seem to survive atmospheric passes (20km PE ) unaffected when hyperbolic but AFAIK they would be killed when put into (for example) a 100kmx20km Kerbin orbit.

[Snark]

28 minutes ago, MaxL_1023 said:

I am not sure honestly, but something is odd with the way craft on rails behave. They seem to survive atmospheric passes (20km PE ) unaffected when hyperbolic but AFAIK they would be killed when put into (for example) a 100kmx20km Kerbin orbit.

Oh, that.  That's not a bug, that's just how the game behaves by design.

Craft on rails completely ignore atmospheres, as long as the craft never goes below the point that the atmosphere reaches 1% of Kerbin sea-level atmospheric pressure (on Kerbin, that's around 23 km altitude).  If they go below that, then they just silently vanish (are destroyed).

That has nothing to do with the current case, which has to do with "what counts as 'in atmosphere'" when flying the current ship.  Different situation entirely.

[MaxL_1023]

Ok, thanks for clearing that up. I must have had a PE a bit higher than I remember.

[FancyMouse]

6 hours ago, Snark said:

the craft you're currently flying, which is never on rails.

Nope non-physics warp is on rails

[Snark]

2 hours ago, FancyMouse said:

Nope non-physics warp is on rails

Yes, but this is while in atmosphere, which won't allow the non-physics warp.