Reading dV map.

[Hooch]

Hello.

I use this map to more-less get the fuel I need.

But I would like to know exactyly how to read it.

Let's say I want to go to Moho.

I add

4550

1020

730

2200 - This one is slow down and "close" orbit around Moho at 50km?

1400 - Is deorbiting or getting back from ground to orbit?

1. Is that last number between "Low Orbit" and celestial body dV needed to deorbit and land or to get back to orbit. Or is it the same in both cases?

2. How to calculate amount of dV needed to get back to Kerbin based on that map?

Best regards,

Maciej K.

P.S.

Do you know any better map?

[Robbii6]

To calculate the way back just go backwards and add the delta v

Double i guess

[HoY]

also if your looking to land on Moho, unless you get an absolutely optimal launch window you should expect to bring along another 5-8k dV

the correction burn mid flight can cost between 100-1000 depending on the window, then the capture burn can cost from 2200 (minimum) to upwards of 8000 m/s if you have a really bad approach

and you see the little circle on the pictures of the planets with atmospheres, you can land on them for pretty much free if you have chutes, so dont add their full value for the landing just take off

[FortyCaliber]

Let's say I want to go to Moho.

I add

4550

1020

730

2200 - This one is slow down and "close" orbit around Moho at 50km?

1400 - Is deorbiting or getting back from ground to orbit?

1. Is that last number between "Low Orbit" and celestial body dV needed to deorbit and land or to get back to orbit. Or is it the same in both cases?

2. How to calculate amount of dV needed to get back to Kerbin based on that map?

...

Do you know any better map?

1. To get to Moho:

4550 - from Kerbin to 80K LKO

1020 - from LKO to escape (+10%)

-----

730 - from escape to Moho Intercept

2200 - from Moho intercept to 50K LMO circulization

-----

* These above two values should be combined as one for purposes of going there, so, 2930 m/s, because the dv to get from Kerbin escape to Moho intercept may vary depending on intercept altitude, but it is nominally 730 dv.

1400 is the value to get from Moho surface to 50K LMO.

So, for a single craft launching from Kerbin, landing on Moho, and Launching from Moho to return to Kerbin, the total would be:

4550

1020

730

2200

[unknown, but no more than 1400]

1400

2200

730

1020

-----------

13850 + [1400 max]

It's possible to do this, but it may be easier on your equipment load and fuel requirements if you build a vessel that carries a lander to Moho, detaches the lander, the lander lands, launches, re-docks, transfers crew and any remaining fuel, and then jettisons the lander. This way you don't need to land your return fuel on Moho. This of course assumes you know how to dock well.

A parachute is used to return the command pod to Kerbin, so no fuel is needed to land on Kerbin.

This is the best delta-V map available right now. I have contributed values to it and recommended that the author add 10% to all true values to account for error.

[Motokid600]

How is it only 730m/s from escape from to Moho intercept? It took me that much just to match inclination ( more I think. Over 1k ) Then the burn to Moho took me several thousand m/s of d-v. THEN the 2200m/s for capture. So that leads me to believe I'm doing it wrong. From 80km LKO I burn prograde just until SoI change to get the most circular Kerbol orbit as I can. Then at Mohos ( or any other planets ) AN/DN I perform the inclination burn. Then at the the right phase angle ( -151 degrees for Moho I believe ) I make the transfer burn. And...it fails everytime.

Every ship I construct for a landing and return ends up using every last drop in just getting to the target planets surface. I always have to use my return fuel. So that's no good. No matter how much fuel I put into space its always the same result. Now..I don't use nukes. I know...shoot me. I use them for my return stages, but the problem I find with nukes is there too large. You try to stack multiple stages with nuke engines and the next thing you know you have yourself a wobbly skyscraper...So besides the hardware issues how exactly is the person who made this chart conducting his burns? Do you burn straight out of LKO to intercept? Because even with the right phase I have too much trouble tweaking my nodes for an intercept. It's SO much easier in Kebol orbit after matching inclination.

Edited July 15, 2013 by Motokid600

[Mr Shifty]

1400 is the value to get from Moho surface to 50K LMO.

You should be able to lift off from Moho to 50 km for under 1000 m/s. It's airless; this is easy to calculate. Orbital speed at 0 km is 820 m/s. A Hohmann transfer from the surface to 50 km takes 71 m/s. Add the two together, plus 10% for inefficiency. Theoretically the landing should be possible for similar delta-V; depends on the pilot's skill.

[Johnno]

None of the current delta-v maps take into account inclination (nor eccentricity I think). They're for equatorial orbit to equatorial orbit, which will give you wrong values for Moho, Dres and Eeloo. To get correct values for transfer to those three use this: http://alexmoon.github.io/ksp/

As pretty much always comes up when Moho is discussed (and as HoY pointed out) you need quite a bit more for both the inclination and the capture burn. I'm used to burning around 4k for capture, and I bring 1k for inclination.

I'm just now wrapping up my first mission to Dres and spent more delta-v than planned cause of sloppy exit and course correction burns, getting home shouldn't be a problem though as I always overengineer my ships.

So yeah, bring extra if you're heading to Moho, Dres or Eeloo.

[Mr Shifty]

From 80km LKO I burn prograde just until SoI change to get the most circular Kerbol orbit as I can.

This method, where you exit Kerbin's SOI with as little relative velocity as possible, is hurting you. If you're hurtling away from Kerbin with some excess velocity, then you get to add (if you leave in the direction of Kerbin's prograde) or subtract (if you leave in the direction of Kerbin's retrograde) that excess velocity from Kerbin's when you reach the sun's SOI. This wouldn't matter except that the Oberth effect makes these speed changes much more efficient when you're near Kerbin.

Then at Mohos ( or any other planets ) AN/DN I perform the inclination burn.

Here's why this isn't working for you. If you're following Kerbin along near its orbit, you're going about 9,300 m/s relative to the sun. To calculate how much delta V is necessary for an inclination change you can use (as an approximation that works for small angles): velocity*sin(delta-inclination)=9300*sin(7 degrees) = 1133 m/s. What you want is an inclination change of less than 7 degrees, which you can accomplish by setting up your transfer ellipse, then burning at the far end from Moho, near Kerbin, when you're going slowest and you can use the long axis of the orbit ellipse as a lever. Or you can use this tool:http://alexmoon.github.io/ksp/ to calculate the launch trajectory directly from Kerbin's orbit.

[Motokid600]

Some good info Shifty thanks. As for that tool. What's the difference between balllistic, optimal and plane change? And which time do I type in exactly? The flight time? Or.. is there a general game time somewhere?

[Mr Shifty]

Some good info Shifty thanks. As for that tool. What's the difference between balllistic, optimal and plane change? And which time do I type in exactly? The flight time? Or.. is there a general game time somewhere?

The departure and arrival times are in game Universal Time. You can see game UT, I believe in the Tracking Station. I use Kerbal Alarm Clock, which displays it in the main GUI. It starts at 1y1d0h0m0s when you start a new save. The time of flight on the graph is in days, and the departure date is the number of days since the beginning of your save, e.g. UT 2y1d would be day 366.

Ballistic is a single burn elliptical transfer; plane change has an inclination change burn in the middle of the transfer; and optimal is the most efficient of the two for each point on the plot. Note that you can hover over the ejection and insertion delta-V links to get numbers you can plug into MechJeb or the Improved Maneuver Node plugin for exact transfer trajectories.

[Motokid600]

Awesome man thanks so much. Uhm...why choose one option over the other though?

Edited July 15, 2013 by Motokid600

[tomf]

Plane change is a bit easier to manage - just burn prograde from kerbin at the correct time and then set up a node to correct inclination at the AN/DN.

Ballistic requires only a single burn but it is more complicated to work out in which direction to point the rocket.

Optimal requires the minimum dv but will have a complicated burn at Kerbin and a plane change burn later on.

[The Scientific Moustache]

https://en.wikipedia.org/wiki/Bi-elliptic_transfer have you ever considered incorporating bi elliptic transfers. these would be preferable in terms of delta v over hohmann transfers while going from/to moho to/from jool or eeloo. Also eeloo to eve either way. Also very useful for going into low kerbol orbit.