Rescue an Interplanetary Traveller?? Or, did the Mun effect the course of a ship on rails?

[Brainlord Mesomorph]

New career game, haven't landed on the Mun yet, I accepted a contract to rescue a Kerbal in LKO. When I looked, he’s not in LKO, he is in a failed transfer orbit to the Mun (Ap in lunar orbit, Pe in LKO but in the wrong direction) I don’t have a manned vehicle with that kind of delta V yet, so he’ll wait.

I proceed with my first robot lander on the Mun, all goes well.

Now I look at my map, and this guy is on an escape trajectory heading out toward the sun! His Pe is beyond lunar orbit and this guy is out of here!

At first I thought it was a different guy, wondering if I had accepted (and missed) a contract to rescue interplanetary traveler(!) then I realized the one on the transfer orbit was missing. And it was a very dangerous orbit. So I figure one of three things had to have happened:

1. The Mun came by and pulled him out of orbit, but that violates everything I know by the on-rails physics system.
2. I guess it’s *possible* that he flew by the Mun, and within 22 km(?), while I was doing my robot landing. (what are the odds of that?)
3. Or the game glitched out and moved his orbit.

So now I’m going to have a shipwreck in interplanetary space to go rescue once I have ships with enough delta V to get out there. (and an open contract until then) Edited November 18, 2015 by Brainlord Mesomorph

[monophonic]

Ships on rails do and always have changed SOIs and felt the effect. He was doomed to be ejected by the Mun the moment he spawned on that orbit.

[ZooNamedGames]

Ships on rails are subject to SOI effects such as gravity assists or slingshots. So I can take it that he was simply on an orbit which happened to be near the mun and he must have encountered it and was shot out of the Kerbin system.

[Brainlord Mesomorph]

Really?! always?

I thought the gray lines where the on-rails objects. And they always show a single conic section. You never see a bezier curve in gray.

I thought the ship had to be loaded for patched conics to work. You're telling me the system is doing much more complex math than its showing us in map view.

I assumed the system projected a single orbit for a given object and if it didn't collide with anything in THAT one orbit, just left it on that rail forever. Guess not.


EDIT: WAIT: then what *isn't* it doing "on rails"? Edited November 18, 2015 by Brainlord Mesomorph

[ZooNamedGames]

[quote name='Brainlord Mesomorph']Really?! always?

I thought the gray lines where the on-rails objects. And they always show a single conic section. You never see a bezier curve in gray.

I thought the ship had to be loaded for patched conics to work. You're telling me the system is doing much more complex math than its showing us in map view.

I assumed the system projected a single orbit for a given object and if it didn't collide with anything in THAT one orbit, just left it on that rail forever. Guess not.[/QUOTE]

It will record all encounters with all objects whether they are the current active vessel or not. This is easily seen with asteroids as they pass by Kerbin. The only thing the game doesn't manage while not the active vessel is atmospheric effects such as re-entry or aerobrakes. Currently if you enter a bodies atmosphere and that vessel is not actively controlled it will pass through as if it didn't have an atmosphere at all- unless it's periapsis is below the bodies sea level, then it just vanishes from exsistance. This is again, often seen with asteroids which (extremely rarely) spawn with a periapsis so low that it in fact collides with the planet, but regardless of size, after a certain point it vanishes from exsistance with no ill effects.

To the edit: atmosphere is not currently managed by the rails system. Edited November 18, 2015 by ZooNamedGames

[Korizan]

Basically the game deals with simple calculations or should I say one off when you are not controlling the craft or are near it.
So collisions with planets and SOI changes can easily be done.
Atmosphere is one that is completely ignored, for that the ship is ignored unless you are within range of it.
Also on rails has to do with the calculations involved in the orbits (ie 2 body calculations)
I am sure someone can go through the list in great detail for you if you wish.

[hugix]

Even when a vessel isn't loaded it will transistion SOI. When you launch a vessel on a interplanetary trajectory it will still leave the Kerbin SOI and enter the sun's SOI when not loaded.

[Brainlord Mesomorph]

I see, not atmospheric effects, BUT gravity effects. (I guess it could do that math once per orbit and not in a constant sub-second physics loop.) I was thinking atmospheric effects and gravity were handled the same way on rails.

But you have to agree that it doesn't SHOW us any of that in map view. for a ship you're not "flying" it shows a simple ellipse whether it hits an SOI or not. Hence my confusion.

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[quote name='hugix']Even when a vessel isn't loaded it will transistion SOI. When you launch a vessel on a interplanetary trajectory it will still leave the Kerbin SOI and enter the sun's SOI when not loaded.[/QUOTE]

Yes, but that's this ONE orbit, I figured that if it cleared the first orbit, THEN no more gravitational math. (i was wrong)

[FancyMouse]

well, it could be still a few periods before SoI change, so it's not shown in map view (yet)

[pincushionman]

"On rails" simulation is exactly the same as full simlation except it ignores, in particular:

1) atmospheric forces (lift and drag)
2) internal forces

All orbital-motion effects such as SOI changes are respected, and in fact in 1.0 the SOI-boundary behavior was changed under the hood to ensure it always happens (prior, you could skip through at high warp under certain conditions).

As for why you didn't see it in the orbital predictions, I can think of two reasons off the top of my head:

1) did't upgrade Tracking Center. If you haven't upgraded to "show patched conics" then the predictions will not account for SOI changes properly. They'll still happen, though.

2) At the time you looked, the Mun encounter was simply so far in the future the prediction didn't bother to show it. How much time had passed?

[Brainlord Mesomorph]

[quote name='pincushionman']

All orbital-motion effects such as SOI changes are respected, and in fact in 1.0 the SOI-boundary behavior was changed under the hood to ensure it always happens (prior, you could skip through at high warp under certain conditions).

[/QUOTE]

Ah HAA!
I *KNEW* I had seen spaceships fly through planets!!

EDIT: AAMOF, I used to put nodes right infront of SOI changes, because I was afraid of warping past them Edited November 18, 2015 by Brainlord Mesomorph

[paul23]

[quote name='pincushionman']"On rails" simulation is exactly the same as full simlation except it ignores, in particular:

1) atmospheric forces (lift and drag)
2) internal forces

All orbital-motion effects such as SOI changes are respected, and in fact in 1.0 the SOI-boundary behavior was changed under the hood to ensure it always happens (prior, you could skip through at high warp under certain conditions).

As for why you didn't see it in the orbital predictions, I can think of two reasons off the top of my head:

1) did't upgrade Tracking Center. If you haven't upgraded to "show patched conics" then the predictions will not account for SOI changes properly. They'll still happen, though.

2) At the time you looked, the Mun encounter was simply so far in the future the prediction didn't bother to show it. How much time had passed?[/QUOTE]

The also nullifies the rotation.

So physically the objects are considered point-masses.


I think he mean the "gray lines" didn't show the patched conics; this is normal, you only see them in tracking station if you click on an object.

@brainlord: still there are quite a few inaccuracies I noticed when going at high warp (objects not having the same final orbit after SOI changes depending on warp lvl).

[Xyphos]

The guy was doomed from the moment you accepted that contract. Had you not accepted, he would have survived. Funny how that works, no?

[Deutherius]

[quote name='Xyphos']The guy was doomed from the moment you accepted that contract. Had you not accepted, he would have survived. Funny how that works, no?[/QUOTE]

Well... He couldn't have been kicked out too far. Few years tops and he'll be back in Kerbin SOI again. Possibly hitting Kerbin.

[Xyphos]

[quote name='Deutherius']Possibly hitting Kerbin.[/QUOTE]

if his malnourished, already-dead corpse doubtfully survives re-entry, sure.

[Brainlord Mesomorph]

[quote name='Xyphos']if his malnourished, already-dead corpse doubtfully survives re-entry, sure.[/QUOTE]

He's happily in torpor, and by the time he completes one orbit, I'll have a massive interplanetary fleet ready to receive his incoming ship.

[wdsmith3]

One of my satellites had an "unplaned mun encounter" causing a slingshot to interplanatary space. It had enough fuel left to setup a duna encounter.

[Tourist]

[quote name='Xyphos']if his malnourished, already-dead corpse doubtfully survives re-entry, sure.[/QUOTE]

In the head-canon for my current career, Kerbals don't need to eat, they photosynthesize, that is why life-support and supplies are not an issue (at least in this career, I may add the lifesupport mod at some point in the future) They only eat snacks for fun.

So he could survive all that time, all he needs is sunlight. He'll be [B]very[/B] bored by the time he gets back though... you can only play "I spy" with mission control so many times before working out what "something beginning with J" is no longer presents the challenge it did in the first couple of hundred days.



Spoiler: Its Jool.

[Geschosskopf]

[quote name='pincushionman']...As for why you didn't see it in the orbital predictions, I can think of two reasons off the top of my head:

1) did't upgrade Tracking Center. If you haven't upgraded to "show patched conics" then the predictions will not account for SOI changes properly. They'll still happen, though.

2) At the time you looked, the Mun encounter was simply so far in the future the prediction didn't bother to show it. How much time had passed?[/QUOTE]

Well, that's no necessarily the tracking station's fault but a basic game limit. The system that draws future orbital paths isn't very good if it has to draw through an SOI boundary. For instance, with asteroids. Oftentimes if you view them from outside Kerbin's SOI, it will look like they will be captured naturally and automatically without your intervention, but we know that's impossible due to KSP's 2-body gravity system. Then, when you view them from within Kerbin's SOI (as from a ship you just launched) you'll see the same asteroid now passing through without stopping, just as will really happen.

Also, if you're not actively setting up a maneuver node, you'll never see a future encounter on your own active ship's orbit until you're less than 1 full orbit from it happening. Until then, all you'll see is the blue oval when the ship is active. And if the ship is not active, all you'll see is the gray oval and NEVER see an encounter even when it will happen in less than 1 orbit.

[norup]

Yesterday, I was given a similar rescue mission, that happened to be one of the greatest challenges so far.
A two-star rescue mission, that turned out to be to a retrograde circular orbit just inside the Mun's orbit. Well, not circular for long, with both the stranded and the rescue craft having up to two gravitational encounters with the Mun each orbit. That was hilariously, frustratingly impossible(?). It of course ended with the stranded getting ejected into the solar system with a periapsis inside Eve, and having to abort the rescue mission and send out another interplanetary rescue vessel - mission still ongoing.

[pincushionman]

[quote name='Geschosskopf']…And if the ship is not active, all you'll see is the gray oval and NEVER see an encounter even when it will happen in less than 1 orbit.[/QUOTE]
Did not realize this limitation. Are SOI change predictions shown only when the object is *actually* active (being flown), or are they predicted when the object is selected in the Tracking Center? Because I doubt very many people would choose to fly a potential rescue object unless they already suspect upcoming encounters, and just give a quick look at it from the Tracking Center map.

[Geschosskopf]

If something shows up in the tracking center, and you can select it off the list, then it will show encounters coming up within its current orbital period but not any later than that. But if the object's path takes it into proximity of Mun's orbit, then you can be pretty sure that it will get an encounter in the near future, maybe even its next orbit.

The problem is, I never see stranded Kerbals in the tracking center until AFTER I've accepted the contract. They're not like "position satellite" contracts where you can see the target orbit before accepting the contract. So any time you accept a rescue contract for Kerbin orbit that doesn't expressly say it's in LKO, or is a multi-star thing in Kerbin orbit, you risk accepting an impossible contract due to the stranded Kerbal being ejected by Mun before you can get him. But if he's already in Munar orbit, he'll be safe. So I recommend NOT accepting contracts that can potentially have the Kerbal ejected.

[paul23]

[quote name='Geschosskopf']If something shows up in the tracking center, and you can select it off the list, then it will show encounters coming up within its current orbital period but not any later than that. But if the object's path takes it into proximity of Mun's orbit, then you can be pretty sure that it will get an encounter in the near future, maybe even its next orbit.

The problem is, I never see stranded Kerbals in the tracking center until AFTER I've accepted the contract. They're not like "position satellite" contracts where you can see the target orbit before accepting the contract. So any time you accept a rescue contract for Kerbin orbit that doesn't expressly say it's in LKO, or is a multi-star thing in Kerbin orbit, you risk accepting an impossible contract due to the stranded Kerbal being ejected by Mun before you can get him. But if he's already in Munar orbit, he'll be safe. So I recommend NOT accepting contracts that can potentially have the Kerbal ejected.[/QUOTE]

Well you can easily predict it: there are two price categories for save-a-kerbal missions. The lower profit ones are from LKO, at 80-100km altitude, "almost" in a circulat orbit. The higher once are above KEO and up to the orbit of the mun.

But isn't it actually more exciting racing against the clock instead of being able to do the same boring 90+ day encounter?