Sending a space probe outside Kerbin?

[sadron]

So, I got my space probe on an escape route from Kerbin orbit. But once it got outside of Kerbin's influence it got into a circular orbit around Kerbol. I want it to fly towards the inner solar system but I'm afraid that I'll burn through all of the xenon gas before its ion engine is going long enough to get it there. What am I doing wrong?

[Vanamonde]

You didn't do anything wrong, except perhaps underestimate the amount of fuel required. Once out of Kerbin's SOI, burn retrograde to lower your solar orbit periapsis, and once down there, burn retrograde again to lower the apoapsis.

[Fyrem]

this is (close to) the best and easiest method.:

To 'fall tword the sun' setup your escape orbit so that it travels BEHIND Kerbins orbit (if you some out just past Mins orbit, you will start to see Kerbins orbit circle... judge by that, and setup your escape close to that same line.)

Now, once you are out of Kerbins SOI (Sphere Of Influence) burn RETROGRADE. This will drop your PE tword the sun - tword Eve, and Moho. Get the PE where you want it, then when you arrive at the PE, you can circuilize buy burning Retrograde (again).

Note: the REVERSE is true: If you escape Kerbins orbit going in front of it's Path around the sun, and then burn PROGRADE after leaveing the SOI, your orbit will stretch out past kerbin, and tword Duna, Jool, Eello.

[sadron]

Now does this pertain to me burning on the rocket BEFORE releasing the probe? I don't think the ion engine is gonna cut it when burning retrograde...

[Vanamonde]

Where are you in the flight? The most efficient way to do it is to start your burn in Kerbin orbit, facing prograde, just as you are coming around from the night side to the dayside, and keep burning, whatever stages you've got, until your solar periapsis is where you want it. Wait until you get to that periapsis, turn retrograde, and burn to bring the apoapsis down.

[TheDarkStar]

You will always have a near circular orbit around the Sun when you leave a planet's SoI, since you still have the inertia from the planet you left. Also, if you are going to a planet with an atmosphere, you can slow down by aerobraking.

[maackey]

This map is really helpful for knowing approximately how much delta-v you need to reach planets in the Kerbol system:

http://forum.kerbalspaceprogram.com/showthread.php/25360-Delta-V-map

You can figure out your rocket's delta-v by Tsiolkovsky's rocket equation. By looking up the full/empty mass of fuel tanks+weight of every other component and the Isp of the rockets etc. manually, or use MechJeb/Flight Engineer which does all the part lookups and maths for you (the easy option I use )

edit: the ion engine has *very* *very* veeerrrry low thrust, so it takes a long time to go *anywhere* but is super efficient and gives great delta-v.

[TheDarkStar]

This map is really helpful for knowing approximately how much delta-v you need to reach planets in the Kerbol system:

http://forum.kerbalspaceprogram.com/showthread.php/25360-Delta-V-map

You can figure out your rocket's delta-v by Tsiolkovsky's rocket equation. By looking up the full/empty mass of fuel tanks+weight of every other component and the Isp of the rockets etc. manually, or use MechJeb/Flight Engineer which does all the part lookups and maths for you (the easy option I use )

edit: the ion engine has *very* *very* veeerrrry low thrust, so it takes a long time to go *anywhere* but is super efficient and gives great delta-v.

One thing about Tsiolkovsky's rocket equation: Each stage's delta-v has to be calculated individually, then added.

[sadron]

So, if I want my probe to go into the solar system to pass by planets, I'll need to first get the rocket to leave Kerbin's orbit then work on the solar orbit until it's slingshotting through the system to fly by planets and what not? And pretend my Kerbal Space Command is getting planetary photos n' stuff.

[TheDarkStar]

So, if I want my probe to go into the solar system to pass by planets, I'll need to first get the rocket to leave Kerbin's orbit then work on the solar orbit until it's slingshotting through the system to fly by planets and what not? And pretend my Kerbal Space Command is getting planetary photos n' stuff.

You have the idea right. If you set a planet as target (click on it's orbit) and your orbit gets close enough to the planet's, you can see the nearest you get to it in the next orbit or so. It also shows you how much your orbit's inclination is different from the target.

[sadron]

And if I target something, it'll appear on my Navball and then I just thrust in that direction?

[sadron]

Can anyone tell me? Sorry for the dumb questions x-x

[Westo454]

You'll get a target (purple) on your navball, but it might be better to mess with maneuvers in flight. This gives you a rough idea of no much Delta V is required for your specific circumstance. That way you can build your ship to your needs, I encourage you to use the rocket equation to calculate how much Delta V you need.

[Vanamonde]

And if I target something, it'll appear on my Navball and then I just thrust in that direction?

Oh god no. That only works for things that are within a few kilometers. To get to other planets you need to have very precise aim and timing, as set forth by this calculator: http://ksp.olex.biz/ But it's hard to be that precise, and even NASA does mid-course corrections.

[sadron]

I still need to learn how Delta-V works and what not. I'm smart, but for some reason I feel like looking at the Delta-V equations and trying to work that out ingame is gonna harm my brain x-x

[Specialist290]

Calculating delta-v ain't hard; it's just long and tedious (if you do it by hand). It's basically a function of your engine's efficiency and the ratio between the mass of the fully-fueled rocket and the mass of the final payload. There's two pages that I always recommend whenever the subject comes up, because they explain the basics in fairly simple terms and using no more math than you need to operate a calculator.

Of course, if you're willing to use mods, then things like MechJeb and Kerbal Engineer Redux can do all the math for you.

[sadron]

The thing is I wanna do it on my own merits. I respect people who use MechJeb but I'll feel like I'm cheating and that it wasn't done by me if I use MechJeb.

[Blackstar]

Then you want Kerbal Engineer Redux. It works in the assembly building and will calculate before you launch how much delta-V each stage has. There's also an in-flight module that updates the info as you go similar to MechJeb, but without any autopilot or planning capability.

[Westo454]

The alternative being the use of the following equation

Delta V=(Specific Impulse x Gravity) x Ln (Initial Mass/Final Mass)

It's really not that hard, especially if you have a calculator.

[PwnedDuck]

Now does this pertain to me burning on the rocket BEFORE releasing the probe? I don't think the ion engine is gonna cut it when burning retrograde...

Ion engine should take you to Duna or Eve, maybe Dres or Moho at a stretch, but you can't aerobrake there. NEVER release the probe from a rocket with fuel in it, if that's what your doing. Use the rocket for all the Delta V it has in it, then switch to the ion engine.

[Fyrem]

or another method instead of all the DeltaV math... just Launch something, anything,... and play around with it once it is 'out there amonst the stars'. while you are playing around with orbits, and such, you will begin to understand how much 'thrust' is needed to do various things.

until you have a basic understanding of how things 'move' out there, doing all the Delta V math is a waste of time. play around with a big rocket out in space for a bit to get used to the controls, maneuver nodes, seeing what an 'encounter' even looks like. THEN after that, re-build your rocket with 'just enough delta V + 20% extra" and try again... with the smaller rocket, trying to be efficient, etc.

But for the first time out.. just use what ever rocket got you there and play!

[Jokurr]

I agree with the above post. with my first probe to Duna I just winged it. Got it into LKO, then started playing with the map nodes until I got a flight path that would get me into an intercept with Duna. Timing was terrible and it took something like 200 days to get there, but it worked. Also turned out my probe didn't have enough fuel for a return trip home but that was ok for a first time. i got it to Duna, landed it, took off again and now it will orbit Duna forever. I learned a lot from that.