Calculating DeltaV for interplanetary transfer?

[Pawelk198604]

I want sent probe into EVE and make it burn up in it's atmosphere, collecting science (or soft land but maybe later) 

It was long time since i make mission to other planets in KSP, i one time ploted perfect course but forgot to add good relay antena to probe so i lost contract  

i just wonder does this website is still reliable for calculating transfer?

http://ksp.olex.biz/

I just want do it by myself not using Kerbal Engineer or MechJeb (maybe for planet angle but only for this) 

   

[Superfluous J]

Yes, that website should work fine, though watch out on the timings. Back in 0.22 there was no "kerbin time" which is now the default.

Also, you could look into the Transfer Window Planner mod, which basically takes that website and puts it into the game, allows for integration with Kerbal Alarm Clock, and doesn't have the above problems.

Edited September 2, 2017 by 5thHorseman
Added a couple caveats to using the website.

[septemberWaves]

Just so you know, an Eve transfer is usually only about 1000m/s once you're in low Kerbin orbit.

 

Also, here's a good method for figuring out absolutely any transfer delta-v from anywhere, provided you're willing to send several exploratory spacecraft before you can find out exactly how much delta-v you'll need for the full journey:

1. Get to a low Kerbin orbit, preferably the orbit which you'll be using as the basic parking orbit for most interplanetary transfers.
2. Regardless of how much fuel you have left or what position the planets are in, plot a maneuver node so that the projected orbit extends beyond Kerbin's SOI, and just about touches the orbit of whichever planet you're targeting. Try to get the ejection trajectory from Kerbin's SOI parallel with Kerbin's orbital direction by dragging the node around the low Kerbin orbit; if the planet is further away from Kerbin you should be leaving Kerbin's SOI in the same direction that Kerbin is travelling, whereas if the planet is closer to the sun than Kerbin you should be leaving Kerbin's SOI in the opposite direction that Kerbin is travelling.
3. Note the delta-v of this maneuver node, that is the approximate delta-v that will be required to transfer to this planet.
4. Figure out the launch window. This can be found by rough judgement; the transfer window will usually be at a time when a tangent to the orbit of the inner planet (drawn in the direction the inner planet is orbiting) will coincide with the outer planet. If you want a more accurate method, use the online calculator you linked in the first post of this thread.
5. At the launch window, launch a flyby probe with the amount of delta-v noted in Step 3 (obviously this is the amount which is needed once in Kerbin's orbit, not the total amount needed for the whole mission), as well as a few hundred meters per second extra so that you have a good margin for error. Send this probe to fly by the targeted planet.
6. Be sure to adjust the intercept with the targeted planet before reaching that planet's SOI. Adjust the intercept trajectory so that the periapsis is as close as you want to orbit the planet (e.g. for Eve I'd usually use a 100km orbit, and thus a 100km periapsis for the flyby probe).
7. Once the flyby spacecraft enters the planet's SOI, plot a maneuver node at the periapsis that would take the space probe to a circular orbit. The delta-v of this maneuver node is the amount of delta-v to reach a circular orbit from a transfer from Kerbin.
8. If you want to find out how much delta-v is required to get from Kerbin orbit to orbit of the targeted planet and then back to Kerbin orbit with no aerobraking, add the delta-v for the transfer to the delta-v for reaching circular orbit around the target, double that number, and add a few hundred as an error margin.

 

I use this technique for finding out the required delta-v for any situation when I don't already know what's required (such as rescaled versions of the solar system, or planet packs without documented delta-v charts). It's fairly approximate, but it works well. An example of how it works would be with Duna: I'd start out by sending a simple orbiter to low Kerbin orbit, and then using steps 2 and 3 I would find out that a Duna transfer takes about 1100m/s from a low Kerbin orbit. I'd then send a flyby probe with slightly more than 1100m/s to fly by Duna, being sure to adjust the orbit along the way so that the intercept periapsis is at 60km (because that's where I usually leave motherships in Duna orbit). By making a node at that periapsis as if I were going to transfer to a circular orbit, I would find that it's approximately 650m/s (if I remember correctly) to reach a circular Duna orbit. Conveniently, this is also the amount of delta-v required to leave Duna on a transfer directly back to Kerbin, and similarly the 1100m/s is about what is needed to circularize back at Kerbin without aerobraking. Therefore the total round-trip delta-v is about 3500m/s, so if I were designing a reusable mothership to make the journey without aerobraking I would design it to have 3800m/s with maximum payload. If I wanted to find out how to get to low Ike orbit from low Duna orbit, I'd have to start by sending a spacecraft to low Duna orbit and then use the exact same technique, because it also works for moons. It takes a few spacecraft to get numbers for every location, but it's certainly an effective method if you have the patience.

If you don't have the patience for such a method and you're using the stock system, try this delta-v chart. It's good for both the stock system and the Outer Planets mod, and for rescales with either of those you can just multiply the values on the chart by the square root of the scale factor (not always accurate for atmospheric worlds though). It says it's for 1.2.1 but I think it's still pretty accurate.

[Pawelk198604]

53 minutes ago, eloquentJane said:

Just so you know, an Eve transfer is usually only about 1000m/s once you're in low Kerbin orbit.

 

Also, here's a good method for figuring out absolutely any transfer delta-v from anywhere, provided you're willing to send several exploratory spacecraft before you can find out exactly how much delta-v you'll need for the full journey:

1. Get to a low Kerbin orbit, preferably the orbit which you'll be using as the basic parking orbit for most interplanetary transfers.
2. Regardless of how much fuel you have left or what position the planets are in, plot a maneuver node so that the projected orbit extends beyond Kerbin's SOI, and just about touches the orbit of whichever planet you're targeting. Try to get the ejection trajectory from Kerbin's SOI parallel with Kerbin's orbital direction by dragging the node around the low Kerbin orbit; if the planet is further away from Kerbin you should be leaving Kerbin's SOI in the same direction that Kerbin is travelling, whereas if the planet is closer to the sun than Kerbin you should be leaving Kerbin's SOI in the opposite direction that Kerbin is travelling.
3. Note the delta-v of this maneuver node, that is the approximate delta-v that will be required to transfer to this planet.
4. Figure out the launch window. This can be found by rough judgement; the transfer window will usually be at a time when a tangent to the orbit of the inner planet (drawn in the direction the inner planet is orbiting) will coincide with the outer planet. If you want a more accurate method, use the online calculator you linked in the first post of this thread.
5. At the launch window, launch a flyby probe with the amount of delta-v noted in Step 3 (obviously this is the amount which is needed once in Kerbin's orbit, not the total amount needed for the whole mission), as well as a few hundred meters per second extra so that you have a good margin for error. Send this probe to fly by the targeted planet.
6. Be sure to adjust the intercept with the targeted planet before reaching that planet's SOI. Adjust the intercept trajectory so that the periapsis is as close as you want to orbit the planet (e.g. for Eve I'd usually use a 100km orbit, and thus a 100km periapsis for the flyby probe).
7. Once the flyby spacecraft enters the planet's SOI, plot a maneuver node at the periapsis that would take the space probe to a circular orbit. The delta-v of this maneuver node is the amount of delta-v to reach a circular orbit from a transfer from Kerbin.
8. If you want to find out how much delta-v is required to get from Kerbin orbit to orbit of the targeted planet and then back to Kerbin orbit with no aerobraking, add the delta-v for the transfer to the delta-v for reaching circular orbit around the target, double that number, and add a few hundred as an error margin.

 

I use this technique for finding out the required delta-v for any situation when I don't already know what's required (such as rescaled versions of the solar system, or planet packs without documented delta-v charts). It's fairly approximate, but it works well. An example of how it works would be with Duna: I'd start out by sending a simple orbiter to low Kerbin orbit, and then using steps 2 and 3 I would find out that a Duna transfer takes about 1100m/s from a low Kerbin orbit. I'd then send a flyby probe with slightly more than 1100m/s to fly by Duna, being sure to adjust the orbit along the way so that the intercept periapsis is at 60km (because that's where I usually leave motherships in Duna orbit). By making a node at that periapsis as if I were going to transfer to a circular orbit, I would find that it's approximately 650m/s (if I remember correctly) to reach a circular Duna orbit. Conveniently, this is also the amount of delta-v required to leave Duna on a transfer directly back to Kerbin, and similarly the 1100m/s is about what is needed to circularize back at Kerbin without aerobraking. Therefore the total round-trip delta-v is about 3500m/s, so if I were designing a reusable mothership to make the journey without aerobraking I would design it to have 3800m/s with maximum payload. If I wanted to find out how to get to low Ike orbit from low Duna orbit, I'd have to start by sending a spacecraft to low Duna orbit and then use the exact same technique, because it also works for moons. It takes a few spacecraft to get numbers for every location, but it's certainly an effective method if you have the patience.

If you don't have the patience for such a method and you're using the stock system, try this delta-v chart. It's good for both the stock system and the Outer Planets mod, and for rescales with either of those you can just multiply the values on the chart by the square root of the scale factor (not always accurate for atmospheric worlds though). It says it's for 1.2.1 but I think it's still pretty accurate.

thanks

I heard that i can use EVE and DUNA to get to Jool and save lot of fuel? 

Edited September 2, 2017 by Pawelk198604

[septemberWaves]

9 hours ago, Pawelk198604 said:

I heard that i can use EVE and DUNA to get to Jool and save lot of fuel?

This is very true, but it takes an absolute age and it's often simpler to design a vehicle with the extra delta-v than to plan for the numerous gravity assists that it would take to save a significant amount of fuel on a Jool transfer. It's also not an option if you're using life support, because it takes so long. If you're experienced you can get to Jool with around 1200m/s I think using gravity assists, when a direct transfer would take 1000m/s more than that. But it's an incredibly inconvenient method and is only really worth doing if you're doing a lot of other missions in between to pass the time, or if you're using a spaceplane where any fuel saving has a big impact.