How can i return to kerbin from this orbit (in less tan 4 years)

[dakeXd]

Im new on the game and this was my first interplanetary mission, go around eve and come back home. i reached low orbit on eve and wanted to go back, but im not able to trace an orbit to reach kerbin, my buget its 3000 ms and i would like to come back before all my missions are expired (3-4 years aprox) Could someone help me or provide some guide to this kind of travels?

[Superfluous J]

You likely can't. But it's not a big deal.

At your Pe, set up a maneuver node to fire forward so your Ap touches Kerbin's Orbit, so you see the encounter markers. then, use the alarm clock to set an alert for that maneuver.

Then, go do the other contracts you've taken in that time. It's like half a year so you have plenty of time.

When the maneuver node time comes up, do that burn and then set up a new maneuver node at your Ap, burning forward to see if you can get an encounter. Use the +/- buttons on the maneuver node to look further into the future. Between +/- buttons and tugging the node handles, you should eventually get an encounter. It may be 10 years from now, but who cares? Because you can set an alarm, and then go do other things. Or, if you run out of other things you want to do, just time warp those years away.

tl;dr, use the alarm clock functionality to do other things while your ships are doing long transfers.

[king of nowhere]

You likely can, espoecially if your ship has a heat shield to aerobrake from a fast intercept, but it's hard for someone not very experienced.

Let's start with some basic orbital mechanics; the lower your orbit, the faster it goes. It means, since your orbit is inside kerbin's, that you are orbiting faster than kerbin. but not a lot faster, becuse your orbit is still fairly similar to that of kerbin. you probably have an orbital time of 300 to 350 days - it would have been nice if you had included that in the picture.

which is a problem if you want to return to kerbin fast, because you are moving faster than kerbin but you are slightly ahead of it. so you'll basically be chasing kerbin, for a full orbit. you'll only gain a few weeks every orbit, so it will take a while to catch up. It's going to be fairly cheap, at least.

So, to shorten your return, you can use some of your large fuel allotment to try one of two things:

1) go slower than kerbin, so that it will be kerbin to catch you.

2) go a lot faster than kerbin, so that you can reach it faster.

option 1) requires you to raise your orbit - either apoapsis or periapsis, apoapsis is likely more efficient - until you have an orbital time of some 500 days. this way, kerbin should overtake you in one orbit or so.

option 2) requires you to further lower your periapsis - down to an orbital period of 200 days or so - so that you'll move a lot faster than kerbin, and you will overtake it in two-three orbits.

in both cases, you are likely to not cross kerbin's orbit in an hohmann-like transfer, so you'll get a very high intercept deltaV - hence the need for a strong heat shield.

more troubling, in both cases, you still have the problem of getting an actual intercept on kerbin. it's doable with more orbital mastery, but not easy to explain. I don't think I can do it in a post.

Edited April 18, 2023 by king of nowhere

[king of nowhere]

UPDATE: I quickly simulated a couple trajectories for you to get an intercept in less than 2 years for half your deltaV budget.

19 hours ago, dakeXd said:

Im new on the game and this was my first interplanetary mission, go around eve and come back home. i reached low orbit on eve and wanted to go back, but im not able to trace an orbit to reach kerbin, my buget its 3000 ms and i would like to come back before all my missions are expired (3-4 years aprox) Could someone help me or provide some guide to this kind of travels?

You can see below that kerbin, eve and your spacecraft are in a similar position to what they are in your save. Not a perfect much, but as close as I could reasonably get, and close enough that the same strategy will work. actually getting in that position with the cheat mode was the hardest part.

so, let's see how you can return to kerbin with the two options I gave you

option 1): move slower than kerbin

start immediately a prograde burn. raise your apoapsis. eventually you'll reach a point where you'll spontaneously intersect kerbin - provided you have zeroed your inclination first, of course (if you don't, fix your inclination; it should only take a few hundred m/s).

the tricky part is that the game won't recognize your intercept unless you help it along the way. do notice, on the left, the purple maneuver node for 0 m/s. that's only because it helps the game to find the encounter. without it, the game was looking for an encounter 7 years in the future; the encounter-finding algorithm is not great. by setting that node, I instructed the game to look for intercepts shortly after that node, which is where you'll find it.

alas, the tricky part of advanced orbital mechanics is often that the game will not find the intercepts on its own, so you have to eyeball a good approximation of an intercept blindly, and then add some 0 m/s maneuver in the right place to get the game to actually see the intercept, and then refine it.

option 2): move faster than kerbin

First thing I did was to plot a retrograde burn. I plotted it near apoapsis because I want to still intersect kerbin's orbit; luckily, the ship is close to apoapsis right now.

burning retrograde I moved periapsis down, quite a lot. but crossing the orbit of moho is not a problem, encountering it by accident is extremely unlikely. then, at periapsis, I made a small prograde burn to raise orbit and cross the orbit of kerbin. Do notice that the periapsis maneuver is not in the first periapsis passage, but in the second; that's because it will take two orbits to overtake kerbin.

I planned those maneuvers, and of course I did not got a close encounter. but then, it's only a matter of increasing or decreasing the initial burn; this changes your orbital time, so that if the simulation shows that you will be passing behind kerbin, you need to get there faster and so you must lower periapsis a bit to reduce orbital time. and if you pass in front of kerbin, you are too fast and you must raise periapsis. be wary that this fiddling will also move your second maneuver, so you have to move it back to periapsis every time.

 

both options will leave you with some 1500 m/s, which should be enough for kerbin capture even if your approach is not very favorable. so you can do this even if you don't have a thermal shield and aerobraking capability.

 

EDIT: also, your whole management was quite inefficient. You may want to look up some tutorials on hohmann transfers, they are generally the cheapest options.

Edited April 18, 2023 by king of nowhere

[dakeXd]

4 hours ago, king of nowhere said:

UPDATE: I quickly simulated a couple trajectories for you to get an intercept in less than 2 years for half your deltaV budget.

You can see below that kerbin, eve and your spacecraft are in a similar position to what they are in your save. Not a perfect much, but as close as I could reasonably get, and close enough that the same strategy will work. actually getting in that position with the cheat mode was the hardest part.

so, let's see how you can return to kerbin with the two options I gave you

option 1): move slower than kerbin

start immediately a prograde burn. raise your apoapsis. eventually you'll reach a point where you'll spontaneously intersect kerbin - provided you have zeroed your inclination first, of course (if you don't, fix your inclination; it should only take a few hundred m/s).

the tricky part is that the game won't recognize your intercept unless you help it along the way. do notice, on the left, the purple maneuver node for 0 m/s. that's only because it helps the game to find the encounter. without it, the game was looking for an encounter 7 years in the future; the encounter-finding algorithm is not great. by setting that node, I instructed the game to look for intercepts shortly after that node, which is where you'll find it.

alas, the tricky part of advanced orbital mechanics is often that the game will not find the intercepts on its own, so you have to eyeball a good approximation of an intercept blindly, and then add some 0 m/s maneuver in the right place to get the game to actually see the intercept, and then refine it.

option 2): move faster than kerbin

First thing I did was to plot a retrograde burn. I plotted it near apoapsis because I want to still intersect kerbin's orbit; luckily, the ship is close to apoapsis right now.

burning retrograde I moved periapsis down, quite a lot. but crossing the orbit of moho is not a problem, encountering it by accident is extremely unlikely. then, at periapsis, I made a small prograde burn to raise orbit and cross the orbit of kerbin. Do notice that the periapsis maneuver is not in the first periapsis passage, but in the second; that's because it will take two orbits to overtake kerbin.

I planned those maneuvers, and of course I did not got a close encounter. but then, it's only a matter of increasing or decreasing the initial burn; this changes your orbital time, so that if the simulation shows that you will be passing behind kerbin, you need to get there faster and so you must lower periapsis a bit to reduce orbital time. and if you pass in front of kerbin, you are too fast and you must raise periapsis. be wary that this fiddling will also move your second maneuver, so you have to move it back to periapsis every time.

 

both options will leave you with some 1500 m/s, which should be enough for kerbin capture even if your approach is not very favorable. so you can do this even if you don't have a thermal shield and aerobraking capability.

 

EDIT: also, your whole management was quite inefficient. You may want to look up some tutorials on hohmann transfers, they are generally the cheapest options.

You're trully a hero, thank you, i will try to reach kerbin safelly using your tips :>

[dakeXd]

UPDATE!

I finally reached kerbin in less than 2 years, took me some tries (the delta v was not enought to slow down and get and orbit around kerbin, so i archived a reentry orbit at 4000mps).

(The brave kerbals ready to touch Kerbal land water again).

 

The reentry was hard and the shuttle was near to flip and get destroyed, but luckily it reached surface at the first try.  I learned a lot about ksp just in this trip, thank you all, especially king of nowhere, the tips were very helpfully.

[king of nowhere]

18 hours ago, dakeXd said:

UPDATE!

I finally reached kerbin in less than 2 years, took me some tries (the delta v was not enought to slow down and get and orbit around kerbin, so i archived a reentry orbit at 4000mps).

 

 

 

The reentry was hard and the shuttle was near to flip and get destroyed, but luckily it reached surface at the first try.

as I predicted.

You can estimate intercept speed just by looking at the map. A planet is moving very fast, and your ship is also moving very fast, so when they meet, they will have great differences in speed. but, just like two cars speeding on a motorway can touch each other lightly with minimal damage because they are moving in the same direction at very close speed - but a lateral of frontal impact would be devastating - you can achieve a low intercept speed relative to a planet if you reach it while going in the same direction. it's called a hohmann transfer

this case shows earth and mars, but the principle is, look at the point where the transfer orbit intersects mars orbit: both mars and the spacecraft are moving in the exact same direction. this results in (relatively) small intercept speeds.

if you cross the orbit of your target body, the intercept speed is a lot bigger, because you are moving in different directions. but sometimes, like in your case, you can't avoid it.

a reentry pod with a heat shield can withstand a lot of punishment, hence my prediction that - even though you'd have to cross kerbin's orbit in your trajectory and therefore would have a high intercept speed - your ship could survive. it appears from the picture that you don't have a thermal shield but rather a cargo bay; that's also very good for thermal resistance, unfortunately it creates drag in front. and when a ship has drag in front, it wants to flip. good for you, SAS was strong enough to prevent that