Escape Velocity from Kerbin

[V-Bro - The Titan's Driver]

So I've been getting back into KSP, and I'm experimenting with getting to Duna, and I'd like to pick your minds for a moment.

How much Delta V do you actually need to escape Kerbin?
I'm trying to be more efficient with my launches and use less fuel.
The game says escape velocity is about 3431 m/s, but there's plenty of factors that make the velocity in practice much higher: getting the rocket off the ground, punching through the atmosphere, and adjusting orbits so that gravity doesn't work against you.
The amateur inside me keeps yelling "just go straight up" and he needs to be silenced.

I'm also looking for tips on how to "eject" from Kerbin's SOI, as some trajectories are better than others, depending on where you want to go. In this case, Duna's my target.

[kamikazi21358]

https://i.imgur.com/gBoLsSt_d.jpg?maxwidth=640&shape=thumb&fidelity=medium

[V-Bro - The Titan's Driver]

Originally posted by kamikazi21358:

https://i.imgur.com/gBoLsSt_d.jpg?maxwidth=640&shape=thumb&fidelity=medium

That's a great start - has some extras too. A little old (was for 1.3, so planets have changed), but for space travel, it should be a great reference.

[kamikazi21358]

Originally posted by V-Bro - The Titan's Driver:

Originally posted by kamikazi21358:

https://i.imgur.com/gBoLsSt_d.jpg?maxwidth=640&shape=thumb&fidelity=medium

That's a great start - has some extras too. A little old (was for 1.3, so planets have changed), but for space travel, it should be a great reference.

It works with a pretty good degree of accuracy still, it works for me still. Just add a couple hundred d/V for errors and inefficiency or whatever the case is, 99% of the time it is usually enough if something doesn’t drastically go wrong.

[RoofCat]

if you don't go for curved orbit around Kerbin that value might be close to the thruth. Because of how explosive 90° vertical launch escapes atmosphere and gravity much quicker. It just adds up along the route. You pass every "part" faster and in the end escape much quicker so less gravity to slow you down. Least I have seen for LKO was within 2950..3000m/s. That's finished circular low orbit. Turning that straight up and adding some more should be enough. Just start like a bullet.

Not a great solution for realistic space travel designs though as you can't have high delta v total nor optimal prices this way.

[MechBFP]

Going straight up is indeed the best way to reach escape velocity. Not particularly useful mind you unless you just want something in a random solar orbit.

[Grumpy Old Gamer]

Forget the Delta-V maps, they all use the same numbers, which are hopelessly out of date. In general for Kerbin you want about 10,000 m/s of DV. it canbe done with less, btu unless you are going for technical perfection, its better to have extra.

[Grumpy Old Gamer]

Originally posted by RoofCat:

if you don't go for curved orbit around Kerbin that value might be close to the thruth. Because of how explosive 90° vertical launch escapes atmosphere and gravity much quicker. It just adds up along the route. You pass every "part" faster and in the end escape much quicker so less gravity to slow you down. Least I have seen for LKO was within 2950..3000m/s. That's finished circular low orbit. Turning that straight up and adding some more should be enough. Just start like a bullet.

Not a great solution for realistic space travel designs though as you can't have high delta v total nor optimal prices this way.

Spaceplanes launch horizontally, and need far les weight, but are an advanced concept adn there is usually little room for error. They are also difficult to scale. It can be done, but generally they top out at launching Hall effect satellites or gettign kerbils into orbit.

[kamikazi21358]

Originally posted by Shadow Raider:

Forget the Delta-V maps, they all use the same numbers, which are hopelessly out of date. In general for Kerbin you want about 10,000 m/s of DV. it canbe done with less, btu unless you are going for technical perfection, its better to have extra.

It can be done with less than half that.

I literally just launched a satellite today for a solar orbit. 8000 d/v gets you escape velocity. From the sun.

[Grumpy Old Gamer]

Originally posted by kamikazi21358:

Originally posted by Shadow Raider:

Forget the Delta-V maps, they all use the same numbers, which are hopelessly out of date. In general for Kerbin you want about 10,000 m/s of DV. it canbe done with less, btu unless you are going for technical perfection, its better to have extra.

It can be done with less than half that.

I literally just launched a satellite today for a solar orbit. 8000 d/v gets you escape velocity. From the sun.

Doubtful. It takes more than that for a Jool flyby.

[kamikazi21358]

Originally posted by Shadow Raider:

Originally posted by kamikazi21358:

It can be done with less than half that.

I literally just launched a satellite today for a solar orbit. 8000 d/v gets you escape velocity. From the sun.

Doubtful. It takes more than that for a Jool flyby.

Maybe I’ll recreate it and show pictures next time. The rocket lacked 10.000 d/v, but I had nodes for the option of sun escape velocity. The satellite I settled currently for is in a eccentric orbit with it’s Ap. over 500,000,000 I believe.

[Grumpy Old Gamer]

Originally posted by kamikazi21358:

Originally posted by Shadow Raider:

Doubtful. It takes more than that for a Jool flyby.

Maybe I’ll recreate it and show pictures next time. The rocket lacked 10.000 d/v, but I had nodes for the option of sun escape velocity. The satellite I settled currently for is in a eccentric orbit with it’s Ap. over 500,000,000 I believe.

maybe 10k if you are already in orbit, definately not a direct shot fromkerbin surface unless you get lucky and get a gravity assist from the mun and possibly from one of the other planets.

Unless the last pacth dramatically reduced DV requirements, in which case agian, the map is uselessly out of date.

[kamikazi21358]

Originally posted by Shadow Raider:

Originally posted by kamikazi21358:

Maybe I’ll recreate it and show pictures next time. The rocket lacked 10.000 d/v, but I had nodes for the option of sun escape velocity. The satellite I settled currently for is in a eccentric orbit with it’s Ap. over 500,000,000 I believe.

maybe 10k if you are already in orbit, definately not a direct shot fromkerbin surface unless you get lucky and get a gravity assist from the mun and possibly from one of the other planets.

I took off from Kerbin and made orbit (sloppy orbit, it was like ~71k and 330k pe. and ap.), from which I set a maneuver node, it was about high 4K d/v as that was all the fuel I had left. From pe., the ~4.9k d/v was more than enough to sling the satellite into the sun’s escape velocity, while the position I wanted to burned from got me ~500m away from the sun, which would take ~49 years to get to the ap. I did it like 3-4 hours ago from writing this. I had 8k+, less than 9k d/V total before launch, so about 4.9k left over from the sloppy orbit, that is very close to around 3.4k d/v for the orbit.

[Grumpy Old Gamer]

Originally posted by kamikazi21358:

Originally posted by Shadow Raider:

maybe 10k if you are already in orbit, definately not a direct shot fromkerbin surface unless you get lucky and get a gravity assist from the mun and possibly from one of the other planets.

I took off from Kerbin and made orbit (sloppy orbit, it was like ~71k and 330k pe. and ap.), from which I set a maneuver node, it was about high 4K d/v as that was all the fuel I had left. From pe., the ~4.9k d/v was more than enough to sling the satellite into the sun’s escape velocity, while the position I wanted to burned from got me ~500m away from the sun, which would take ~49 years to get to the ap. I did it like 3-4 hours ago from writing this. I had 8k+, less than 9k d/V total before launch, so about 4.9k left over from the sloppy orbit, that is very close to around 3.4k d/v for the orbit.

OK, well video or it didn't happen.

[[IFC]Mjollnir]

Even I, with my just over 60 hours don't need 10K of d/v to reach LKO... with around 7,5K I can make a trip to Mun, establish orbit, adjust orbit, release satelite, make it back to Kerbin and on the way do a rescue mission in LKO too...
Do you have any mods installed that change the system? Like real solar system or so? Otherwise it sounds like you're doing something wrong...

Originally posted by Shadow Raider:

Forget the Delta-V maps, they all use the same numbers, which are hopelessly out of date. In general for Kerbin you want about 10,000 m/s of DV. it canbe done with less, btu unless you are going for technical perfection, its better to have extra.

But I agree, it's always better to have some spare d/v, in case you mess up a burn...

Edit:
To OP:

In case you're still struggling, there are some mods out there, that might help you:

This will make transfers to other planets easy:
https://forum.kerbalspaceprogram.com/index.php?/topic/155998-16-astrogator-v090/

And this one makes gravity turns just as easy:
https://forum.kerbalspaceprogram.com/index.php?/topic/148448-14177-gravityturn-continued-automated-efficient-launches/&

(it says recompiled for 1.4 but so far works with the latest KSP version...)

[kamikazi21358]

The save is a relatively new campaign (~<60 days) and I wanted to launch a probe out of escape velocity of Kerbin. The rocket built had 7,526 d/v, even less than the amount I suggested earlier (>8k). This was enough for escape velocity from the sun, however, I didn't want that, so I didn't even burn at pe. The result was a very eccentric orbit such as this:
https://steamcommunity.com/sharedfiles/filedetails/?id=1642147729
If you're still not satisfied, ill redo a similar mission in the future. But as you can see, it takes way less than '10k d/v' to escape Kerbin's soi, as only 3/4ths of that is capable of escaping the sun's soi.