Getting home from the red planet

[krblman]

I can go to Duna and land with my eyes closed. At this point I've gotten duna missions down to a science, and I can land on duna with around a 30 degree margin of error from a transfer window.

 

But, there's one thing duna-wise I cannot do.

 

How do I get home from duna? I have no idea how to rendezvous (and even if i did, the ship doesn't have docking ports). The lander has around 2.5km/s of Delta V when it lands on the Duna. I've tried sending a kerbal home from Duna but he just got flung around the sun for all eternity. Perhaps the problem is like Eve - It's difficult for me to get to Eve, hence why I only have 1 satelite around Eve and 1 kerbal on eve whereas I have 3 on Duna, and 5 satelites.

Either way, is it meant to be easy or something

[EnderKid2]

Getting home from Duna is the same as getting there. Eject on the correct trajectory during the Duna -> Kerbin transfer window.

Edited May 21, 2021 by EnderKid2

[krblman]

Just now, EnderKid2 said:

Getting home from Duna is the same as getting there. Eject on the correct trajectory during the Duna -> Kerbin transfer window.

How much delta v

[EnderKid2]

Same as getting there. Delta-V map says 1690 m/s from low Duna orbit to low Kerbin orbit, but if you aerobrake at kerbin that drops to 740 if I'm reading the map correctly.

You have a delta-V map and transfer window charts for both directions, right? (though Kerbal Alarm Clock has all the transfer windows between any two bodies so you should use that)

Edited May 21, 2021 by EnderKid2

[Martian Emigrant]

16 hours ago, krblman said:

I can go to Duna and land with my eyes closed. At this point I've gotten duna missions down to a science, and I can land on duna with around a 30 degree margin of error from a transfer window.

 

But, there's one thing duna-wise I cannot do.

 

How do I get home from duna? I have no idea how to rendezvous (and even if i did, the ship doesn't have docking ports). The lander has around 2.5km/s of Delta V when it lands on the Duna. I've tried sending a kerbal home from Duna but he just got flung around the sun for all eternity. Perhaps the problem is like Eve - It's difficult for me to get to Eve, hence why I only have 1 satelite around Eve and 1 kerbal on eve whereas I have 3 on Duna, and 5 satelites.

Either way, is it meant to be easy or something

Hi krblman.

Not pretending to be a planetary rendez-vous expert but 2500 m/s from Duna surface seems enough. A little to play with don't mess too much of it.

You'll have to aerobrake at Kerbin. If the cut is too shallow but make a capture you might have to do several orbits. But from my chair it seems feasible.

Personally I don't use transfer windows. Just the delta-V map.

Save and restore are your friends.

Have fun, make mistakes.

 

 

15 hours ago, EnderKid2 said:

Same as getting there. Delta-V map says 1690 m/s from low Duna orbit to low Kerbin orbit, but if you aerobrake at kerbin that drops to 740 if I'm reading the map correctly.

You have a delta-V map and transfer window charts for both directions, right? (though Kerbal Alarm Clock has all the transfer windows between any two bodies so you should use that)

I have never seen that transfer window chart. Might have to copy it and look at it some more.

Thanks.

 

ME

Edited May 21, 2021 by Martian Emigrant

[Vanamonde]

This question about how to play the game has been moved to Gameplay Questions. 

[Snark]

17 hours ago, krblman said:

Either way, is it meant to be easy or something

It's pretty straightforward and doesn't require a heapton of dV, so basically yes.  It does mean you need a good transfer window, though.

There are a lot of transfer window planners out there, but this one is my personal favorite because it's so simple to use and I like the graphical display of when (and in what direction) to eject:

https://ksp.olex.biz

Just put in origin as Duna, destination as Kerbin, pick what height your parking orbit around Duna is-- say, 60 km-- and there ya go.    From low Duna orbit, you want to eject when Kerbin is 75 degrees behind Duna in their orbits around the sun, and the little picture on the right shows what direction in which to eject.  The size of the burn will be a bit over 600 m/s.

If you allow yourself around 1300 m/s to get to low Duna orbit from the surface, that means your lander sitting on the surface should need a total of around 1900 m/s (in the best case) to make it back home to Kerbin.  Since you've got 2500 m/s, that means you have a nice big safety margin, so you ought to be able to do it pretty well.

(Note that this doesn't budget anything for braking at Kerbin-- I'm assuming you have a heat shield and can just aerobrake once you get to Kerbin.  If that's not the case, then you'd need more dV to brake at the destination.)

 

[krblman]

1 hour ago, Snark said:

It's pretty straightforward and doesn't require a heapton of dV, so basically yes.  It does mean you need a good transfer window, though.

There are a lot of transfer window planners out there, but this one is my personal favorite because it's so simple to use and I like the graphical display of when (and in what direction) to eject:

https://ksp.olex.biz

Just put in origin as Duna, destination as Kerbin, pick what height your parking orbit around Duna is-- say, 60 km-- and there ya go.    From low Duna orbit, you want to eject when Kerbin is 75 degrees behind Duna in their orbits around the sun, and the little picture on the right shows what direction in which to eject.  The size of the burn will be a bit over 600 m/s.

If you allow yourself around 1300 m/s to get to low Duna orbit from the surface, that means your lander sitting on the surface should need a total of around 1900 m/s (in the best case) to make it back home to Kerbin.  Since you've got 2500 m/s, that means you have a nice big safety margin, so you ought to be able to do it pretty well.

(Note that this doesn't budget anything for braking at Kerbin-- I'm assuming you have a heat shield and can just aerobrake once you get to Kerbin.  If that's not the case, then you'd need more dV to brake at the destination.)

 

The lander does not have a heat shield. However, it has an escape pod (command module, parachutes, and science container) with a heat shield.

[Snark]

1 hour ago, krblman said:

The lander does not have a heat shield. However, it has an escape pod (command module, parachutes, and science container) with a heat shield.

Well, that's what I meant:  you can return to Kerbin with the parts you care about, and don't need to spend a bunch of rocket fuel to brake on arrival.

[krblman]

6 minutes ago, Snark said:

Well, that's what I meant:  you can return to Kerbin with the parts you care about, and don't need to spend a bunch of rocket fuel to brake on arrival.

Oh okay