In-system transfer at escape velocity

[NFunky]

Hi guys, got an interesting situation I've never dealt with before.

I am attempting to send my first probe to Minmus in Kerbol 3.7x scale. It's a simple thing with a comms dish, scanner, themometer, batteries and an excessive amount of solar panels. It's very light and mounted on a T200 with Spark engine, so it gets around 3,200 dV once place in LKO. Plenty of dV, even for 3.7x, but no so much that I can afford to waste hundreds.

I jut successfully put a similar satellite into polar Mun orbit by launching into a polar Kerbin orbit, then setting up the transfer so that I cam in directly over the Mun's pole, no plane change required. I want to do the same thing for Minmus, but I'm running into an interesting problem. As you can guess from the subject line, when I try to set up a trans-Minmus injection, I hit escape velocity before I reach Minmus orbit because of the 3.7x scale. This puts me in a tough spot, caue I don't really want to raise my LKO to keep the transfer inside Kerbin SOI, since this will almost certainly cost several hundred dV in doing the maneuver and the loss of Oberth effect. So I'd really like to be able to go on an escape trajectory that intersects Minmus SOI, but the maneuver node and target system do not lend themselves very well to this task.

So, how should I go about plotting the node? You don't get close approach position estimates unless your orbit crosses the target, so I can't do my usually method of determining the tranfer time. Minmus SOI is very small too, so I don't think I can just eyeball it and guess. Anyone done a maneuver like this before?

Thanks

[Harry Rhodan]

I jut successfully put a similar satellite into polar Mun orbit by launching into a polar Kerbin orbit,

I know that's not the actual question but you don't have to go to a polar orbit to achieve that. Just use a normal equatorial orbit and burn slightly to normal or antinormal during the transfer burn.

[Tex_NL]

Easiest (and cheapest) way to get to a Minmus polar orbit is to first launch into a low Kerbin parking orbit. Time your launch and angle correctly to end up in the same 6degree plane as Minmus. Plan and execute your transfer burn like normal. Perform your plane change as soon as you enter Minmus' SOI. High above the surface a plane change is incredibly cheap. Circularize at Pe.

[NFunky]

I guess just forget about what I said about polar orbits. The Kerbin polar to Mun polar was for SCANSat, to give me a full Kerbin scan before heading to the Mun to scan it too in the same mission. I got a new scanner from research, so I thought I'd do the same thing for this mission as well. I am definitely willing to forgo the Kerbin scan to make the Minmus mission more feasible though, so I just now launched the sat into 6 degree co-planer LKO. Got a little over 3,300 dV.

I'm still having the exact same problem with planning the intercept though. I hit escape velocity while my apoapsis is still many thousands of km short of Minmus' orbit. I suppose with the extra 100 or so dV saved from not launching polar, I can just raise my AP on the burn side of Kerbin, but I feel like I'm going to have to raise is to at least 300 km to lower my transfer velocity. Is there a more economical approach? There has to be right?

[Tex_NL]

Either you're doing something terribly wrong or you're describing it terribly wrong. If you could post some screenshots of your map where things are going wrong we might be able to see what's the problem.

[Tatonf]

I think it's a bug. Minmus have been set in orbit around Kerbin but it stands outside Kerbin's SOI. It must be from one of your mod (may be Kerbol 3.7x scale is messing up).

Can you tell us :

1) The highest altitude you can achieve before exiting Kerbin's SOI

2) The altitude of Minmus

[tseitsei]

1)Transfer to minmus normally

2)Capture to VERY elliptical orbit (Ap should be right on the edge of Minmus SoI)

3)Change inclination at Ap. Since your orbital velocity is almost zero it will cost very little dv to do the plane change (well below 100/ms should be enough if you leave Ap far enough)

4)Drop your Ap when you reach Pe next time

5)Profit