Question about required delta v for Duna, and how to actually calculate it?

[Dont]

So today I landed at Duna, to find myself with only 2150 delta v left for the Kerbin return.,

I don't think thats enough, but I do have 4 airbrakes and two parachutes remaining.

But the MAIN question is, how do I actually use this map? http://i.stack.imgur.com/bNAIZ.png

Delta V map ^. Now I feel pretty stupid, rightfully so but atleast I can admit it :D Which way is it?

4500 + 950 + 110 + 370 + 1380 = 7310 + a bit extra? Is that IT if I want to get back to Kerbin?

OR is it

4500 + 950 + 110 + 370 + 1380 (landed at this point on duna) + 1380 for takeoff, 370 for orbit, 110 for intercept and 900 (less cus aerobrake) for Kerbin = 10070 total. Is anything wrong, here? Which equation is correct... thanks for helping me!

TL;DR Does it take 10,070 dV to get to and back from duna, or 7310 dV? THANKS :D

[Aragosnat]

Start from Duna then start adding Delta-V as you past each point and less for Aerobraking. Also as long as you can EVA you have unlimited delta-V. 1380+370+110+950 = 2810 (edit) as Aero braking can take away the needed 4500 for lauching up. Plus and Gravity assists from the Mün to help you slow down will cut the needed delta-v's too. Just depends on how fast you want to slow down or how many orbts you can stand slowing down. Edit: The 4500 is needed if you had not parachutes and wanted to use engine power alone. Even then it would not be as high.

[Melfice]

Also keep in mind that the dV values for Kerbin, Duna, and Eve are likely too high under the new aero model.
Of course, that just means you have a bigger safety net.

Depending on what shape your rocket is, and what ascent profile you take, you can get into LKO* for about 3500-ish dV. 4000 dV should be the absolute maximum, unless you built a crazy monstrosity.

* LKO OUTTA NOWHERE!

[ghpstage]

The second method is much closer for going from Kerbin to Duna and home. Those values aaccount for one direction only so you have to consider both directions. So it would be 4500+950+110+370+1380+1380+370+110+950+4500.
Of course aerobraking can reduce the slowdown at any burn on which a white arrow is shown on the diagram, so at Duna thats the 1380+370 that can be reduced by aerobraking (including parachute), and at Kerbin the 950 and 4500.....
With the new reentry heat I don't know how much of this can actually be practically absorbed by the atmosphere now, in 0.90 you could pretty much always discount all of it. It should still offer a sizeable aerobrake if you hit it at the right angle and have heat shields however.

By the way the values on that map for atmospheric bodies are out of date, with the new aero Kerbin requires only around 3500m/s to achieve orbit. I don't know what Duna or the other planets or Laythe are though.

Depending on how Duna's atmosphere faired in the new patches it seems reasonably likely you could get home, assuming your craft can survive a heavy aerobrake at Kerbin. Its only around 1380+370+110 = 1860 to launch and achieve an encounter with Kerbin, and it wouldn't take much extra (probably like 10-20 if done early enough) to achieve an atmospheric entry rather than a flyby.

[Dont]

How does EVA (exiting ship) grant unlimited dV?

So 3500 (lkOrbit) + 950 (sun intercept) + 110 + ~350 + ~1000 or less + 1380(duna liftoff) + 370 + 110 + 900-1200(kerbin return with 4 aero brakes) = 8670 + 5-10% for efficiency. Is this correct?

[Aragosnat]

All out of gum & ghpstage: He is on Duna already. No need for him to calulate the delta-v needed for lifting off from there. Under the new Aero. He will likely need lesss Delta-vs as Kerbin is now under 4k needed. Not sure how much for Duna. Also anothing thing to point out is. How you enter an atmosphere will depend on how fast you slow down as well as you can now Raise and lower you Pe when within the atmosphere depending on how you angle your craft while going in and leaving.. Which means never needing to spend Delta-Vs on returning. Unless needed for power landing due to lack of chutes.

[Aragosnat]

Originally posted by Don't:

How does EVA (exiting ship) grant unlimited dV?

So 3500 (lkOrbit) + 950 (sun intercept) + 110 + ~350 + ~1000 or less + 1380(duna liftoff) + 370 + 110 + 900-1200(kerbin return with 4 aero brakes) = 8670 + 5-10% for efficiency. Is this correct?

EVA refuels to max when entering back into command pod or other place your Kerbal can be stored that is not a cargo bay.

[Dont]

I always thought monoprop fuel took some of the main engine's fuel, no? So it's a cheat?

[Dont]

Wow... how cheap. That's so... wow.

Was my math above correct?

[Aragosnat]

Crazy I know. IT takes the meaning Quote: Princess Leia, "Would it help if I get out and pushed." To a whole new level.

[Dont]

ROFL

[Aragosnat]

Originally posted by Don't:

How does EVA (exiting ship) grant unlimited dV?

So 3500 (lkOrbit) + 950 (sun intercept) + 110 + ~350 + ~1000 or less + 1380(duna liftoff) + 370 + 110 + 900-1200(kerbin return with 4 aero brakes) = 8670 + 5-10% for efficiency. Is this correct?

No. As when aerobraking. You don't need to count Kerbin when returning as you are braking to slow down. Which means you can get all that removed just by using Kerbin's air to stop you. So 1380 Duna lift off + 370 + 110 + 950 = 2810. Main reason is. You are using Kerbin's atmosphere to slow you down. The 4500 would be needed if and only if Kerbin had no atmosphere to help you slow down.

Edit: Either way. You need to get out and push.

[ghpstage]

The 950 is only needed if you intend to circularize in LKO too, it can also be aerobraked away assuming the craft can withstand the re-entry.

[Dont]

Ahh, I see it now. So simple, and your 100% right.

Thanks, I see n- wait no I dont...

I'm going to slow this down so my mental arse can handle this basic math...

1380, for liftoff duna.

370 for low orbit, duna.

110 to intercept for sun orbit.

950 to TRANSFER from sun, to Kerbin sub 70k orbit.. Anything wrong there <--?

[Dont]

We posted at the same time, so wait, the 110 goes from duna to kerbin low orbit???

[ghpstage]

110 is from Duna escape velocity to a Kerbin intercept, which if left as is would result in a flyby.
During a flyby the 950 would be needed to circularise into LKO.

However, if the flyby goes through the atmosphere, which if corrected in advance of entering the Kerbin SOI will be really cheap, the re-entry aerobraking will act against the 950. So unless getting into orbit from the ground at Duna has become much more difficult I think your craft has a decent chance of making it home. The real problem is aerobraking enough to take a big chunk out of that 950 while actually surviving the re-entry heat.