Having vessel+lander simultaneously in atmosphere

[The_Clyde]

Hi guys;

A silly question, I have a problem trying to launch a lander from an aircraft and I don't know why it is not working (inexperienced player here).

Both are coupled when taking off the runway (with 2 distinct manned command modules).

Then above Kerbin (~4000m) I decouple the lander (which deploys its parachute) and I remain in control of the aircraft to land it safely. After a couple of seconds/minutes, the lander disappears (console says debris crashed / crew killed)..

If I remain in control of the lander instead (switching right after decoupling), the lander lands cleanly and the aircraft (marker in the sky) eventually disappears.. console says that the crew was killed, no mention of the vessel (which DID NOT crash)..

The point is, if I manage the land the aircraft ASAP, remaining as close as possible to the land site (and the lander under chute), the lander doesn't "crash" nor disappear and I can do what expected: switching/recovering vessel or lander, even taking off and flying further, it doesn't matter anymore (as far as the lander actually landed, I guess).

What am I doing wrong? Is it a game limitation? Any workaround?

(KSP stock only - no Mods)

Help appreciated. Thx.

--

Edited August 19, 2015 by The_Clyde
marked answered. thx.

[kStrout]

KSP has an unload distance in the atmosphere, if you are below 20 or so km any ships 2.5km away from the active ship are destroyed, so the computer doesn't have to simulate aerodynamics on lots of ships.

[Geredis]

To follow on from Strout's comment, the only real suggestion anyone will have is to A) fly low and fly REALLY slow and orbit the drop area from that low altitude until the detached module lands.

[xtoro]

Do a search for KSP FMRS. It's a mod that allows you to decouple 2 ships, land one, then go back in time to control the other one and safely land it. This way you don't have to try to control both at the same time, which you usually can't do anyways.

[The_Clyde]

Great,

So it's not a bug or a noob error but actually a game feature. Thx for the confirmation.

So if I get it right, to be sure that my vessels are not concerned by the "garbage collector", I must be sure that either:

- the two vessels remain close enough; or,

- the vessel I am moving away from is in "stable state" (landed, or orbited).

(- or I use a mod).

So for my specific case (I am only launching the lander from the atmosphere), I should decouple low and fly over the landing zone (over and over) until the lander touches the ground; then I can fly back to the base.

The FMRS Mod looks great regarding what I am trying to do, I'll give it a try.

Thx for the replies. Helped a lot understanding this. Now I will experience how close I should remain so that the lander is not considered as a debris... is it 2.5km for sure? I read that somewhere but I don't know if it didn't change recently. Moreover I observed losing contact with the second vessel after a longer time.. maybe ~25km?

[Mister Dilsby]

I did something like this over Eve in the last few panels of "Eve: Order Zero" (comic in my sig) Without spoiling the story too much here was the sequence that worked:

--separate craft close to ground, in this case 8000m.

--activate parachute on one of the craft. This allows it to land safely without any more action on your part.

--use [ to switch to the second craft

--land (or crash) second craft close to the first. In my case the separation between the two ended up being about 9200m on the surface

Key is of course to keep them close. You will not be able to switch back and forth with [ ] if they are more than 2200m apart. If the non-POV craft is in the atmosphere and more than 22.5km distant it may simply disappear.

[_stilgar_]

KSP has an unload distance in the atmosphere, if you are below 20 or so km any ships 2.5km away from the active ship are destroyed, so the computer doesn't have to simulate aerodynamics on lots of ships.

I thought the distance was increased to 22.5 km in Patch 1.0

[ianm1981]

Another option is just to make sure both craft stay out of the low atmosphere Garbage collection zone. it doesn't quite work for your mission profile of dropping a lander but for satellite launches this works pretty well.

I have a Turbojet suborbital satellite plane that just pitches up at around 50 degrees and accelerates until apo is around 80km. Once the heating effects die down (40km up) I drop the satellite out of the cargo bay and circularise it at Apo. Then jump back into the plane for the dive back into the atmosphere.

then wait until the wings start to bite again reverse course and repeat the same suborbital hop back the other way to drop down and land at KSC. Its a great way of completing those small satellite contracts with a near zero launch cost as all you pay for is a splash of jet fuel, all the rest is payload.

[KerikBalm]

I thought the distance was increased to 22.5 km in Patch 1.0

It was. I made a recoverable first stage booster system to take advantage of this... its still pretty hard to have the things land before a rocket gets out of range. (I use Launch escape systems as boosters, since they have great TWR... those mounted on fleas... My craft launches with a 20:1 TWR, and a burn time of about 1 second, and then decouples and deploys the parachutes on them, as it starts its main engine at about 150 m/s and 100 meters)

Anyway, to the OP, you guessed right in the first post. It is a game limitation (I'm not sure I'd call it a feature, but it is intentional behavior to deal with computing limitations).

I'm not sure of the exact altitude, but if you are high enough, the game doesn't do this.

You can have "stable" orbits with a perapsis well within the atmosphere, as long as that vessel is not the active vessel, or within 22.5km of the active vessel. The game won't despawn it because its not low enough in the atmosphere, but it also won't do physics/drag simulations on it.

You can also not use a mod, but use a text editor. Save right after separation, copy the text for the vessel that you don't fly down.... fly it down...

Save (under a different file name).

Load the previous file, switch to the vessel that you didn't fly before... save.

In you save file, paste over the (now) inactive vessel with the data from the file where you landed it. Now the inactive vessel that is >22.km away doesn't get "collected by the garbage collector"

Obviously, its easier to have a mod that does all of that(or an equivalent) for you.

[eddiew]

Slow and low, this could be done... at 100m/s you'd have 25 seconds to hoof the lander out the back and it be on the ground. Might manage it with a 500m altitude and a late chute - or you can stay in control of the plane and try to circle the area until its down to give it more time.

I am a little curious as to why you don't just land the plane though

Not really answering the problem, but the Stage Recovery mod does a nice job of catching things that fall into the game's garbage zone, and if they have chutes on them, will refund you a reasonable amount of money based on their distance from KSC. Very nice for SRB recovery; just cap them with a chute instead of a nosecone and get most of your money back. Like it says in the "designed to be recovered and refurbished" descriptions

[The_Clyde]

You can also not use a mod, but use a text editor.

Interesting, I wasn't aware you could that easily edit the save files.

BTW I tried the FMRS mod (as suggested in another answer) but when I switch back in time to control the second vessel, the crew is insta-killed :/ Dunno what I am doing wrong. Anyway, I will use the "circle around while the lander touchdown", dropping the lander at very low altitude and it's gonna make it. Actually the procedure by itself is not that important, I mostly needed to understand why my vessel and crew disappeared. It's quite clearer right now.

I am a little curious as to why you don't just land the plane though

The idea is to drop stuff (manned or not btw) on locations where an aircraft couldn't actually land. The idea is really to air drop something, landing would be cheating in my case

But of course, there are certainly better ways to achieve the same thing but that's the "20km garbage collector" thing that was bothering me.

[eddiew]

Ahh, I see. Have you considered going for a low-tech VTOL? Would work out a lot smaller than what you're aiming at so far. The top one here doesn't have much speed, but can land on very small areas with a bit of practise Even the chubby one only uses Wheesleys for lift, so the rear engine and intakes could be swapped for a very low-tech version.

Adjust wings to suit your available parts; the main thing is to get the vertical engines and fuel tanks all symmetrical about the CoM of the craft so that it stays balanced at all stages of flight. Bind some action groups to the rear/vertical engines so you can toggle them separately (use RCS and lights if your SPH is only tier 1 or 2) and you'll be able to land pretty much anywhere - with practise. I won't lie, VTOLs are fiddling to get the hang of, but very satisfying when you do

Edit; you could possibly even get a VTOL to carry an extra pod underneath that it would set down gently and fly away from... might need a lot of down-thrust though.

[The_Clyde]

I didn't think about VTOL indeed, these are quite fuel-consuming, aren't they? But yes, it could be a solution.

I still have to test how they can handle some extra load and what is their range (considering the cost of vertical take off and landing).

What do you mean by "use RCS and lights" (are RCS powerful enough? why lights?)

[eddiew]

I didn't think about VTOL indeed, these are quite fuel-consuming, aren't they? But yes, it could be a solution.

I still have to test how they can handle some extra load and what is their range (considering the cost of vertical take off and landing).

What do you mean by "use RCS and lights" (are RCS powerful enough? why lights?)

Sorry jumped ahead there, I'll clarify; an upgraded tier 2 SPH can assign "basic" action groups. That is, it can let you assign special functions to keyboard buttons, but only to the predetermined keys for lights, brakes, rcs, sas, and so on. Since rcs and lights have no place on an aeroplane, so they're the buttons you can safely assign to tasks like toggling vertical/horizontal engines without causing scary side effects (imagine if your SAS turned off whenever you went into vtol mode... not good). With tier 3, number keys 1-0 become available for action groups, so you don't have to make the compromise, but even with tier 2 there's generally a few things you can manage

Should have also mentioned that since tier 1 SPH can't assign action groups, vtols are basically impossible at that level since you can't have independent control of lift and thrust engines. Given that I count 29 parts on your plane, I now don't know if you're on tier 1 or 2, and ought to have asked before suggesting the idea ^^;

That aside, VTOLs can have good range. The Torguga above can push 700km, because once it's moving at a reasonable speed it can shut off the lift engines and close the bay, so it becomes pretty streamlined. Firebird V is a lumpen object no matter how you go about it, and won't break mach 1 because it can't get that streamlined shape. It's good for maybe 50-100km tops.

Fuel consumption isn't necessarily bad; you only need to keep the forward engines running when in full flight, so it's not like you're burning three at once all the time. Mostly it's down to having a cargo bay to tuck the lift engines into so that they don't leave you trying to fly a brick ^^ It is true however that you're carrying more weight in engine than a conventional plane, so you'll never get the range that a craft without VTOL options has (although there are fuel-less electric engines in a few mods that might do nicely...), but they can be made to handle the local hemisphere around KSC

[The_Clyde]

30 parts to be accurate

My SPH is tier 1 indeed, I didn't start playing with action groups yet.

I learnt a lot in this thread, a lot of stuff to add to my todo list. Thx.