To the Mun with Mechjeb 2

[comiquaze]

Hi!

This is my first message here. I've been biten by the KSP bug last week, and I can't stop playing it.

I've managed to build a space station in LKO and I'm planning on sending the first Kerbals to the Mun soon.

As such, I did a test this morning. I built a satellite using the ISA MapSat upgrade and using my usual booster, I sent it on its way to the Mun using Mechjeb 2.

Now, I used the 'Ascent Module' and the 'Launch to Rendez-Vous' feature to fly the mission. My booster did a fine job of flying it the payload into LKO, but then things went awry.

The orbit never circularized, so I couldn't use the 'Hoffman' manoever. I tried various buttons, but all it did was to send my satellite in a huge orbit beyond the Mun and then using other buttons I managed to make it intercept the Mun but it then crashed on the surface. Luckily, it was unmanned, so no Kerbals were hurt.

I'm wondering what could be the best way to achieve a Mun orbit with Mechjeb 2. Do I send the payload up on a parking orbit at around 100km and then circularize the orbit and use the Hoffman manoever to reach the Mun or ?

And how do you get the craft in a LMO once you get there using the MJ 2 controls?

[robly18]

Now do it without mechjeb.

[flightmaster]

MechJeb 2 still has some bugs, that's why it's still in pre-release.

To get to the Mun with mechjeb just use the ascent guidance module and let that get you into orbit, then tell it to do a Hohmann transfer to the Mun. It should be two separate parts of your mission, the ascent and the transfer. Once you've intercepted, then it becomes easy.

[magnemoe]

The Rendez-Vous part of mechjeb 1.9 was of the save before activate type. Not sure if this is updated. It usually missed and had to compensate by overshooting. If you dropped stages during the burn things goes wild. Like you start burn with mainsail from first stage, then switch to poodle from second.

[Sovek]

Meh, I fly the thing myself, let MJ provide the SASS functions and more extensive telemetry.

[MC3craze]

Mechjeb is something you should try to wean yourself off of. Most of the functions can be emulated by flight engineer and the manuever nodes. While the newest version is a lot more manual friendly than versions previous, the autopilot can discourage people from actually playing the game. This is coming from someone who abused it when it first came out.

Anyway, to answer your question, if your orbit after encountering the Mun has a periapsis, set up a manuever node at that point and set it up for a burn retrograde until you have a roughly circular orbit. If the trajectory is just a straight path into the surface, burn prograde until your apoapsis is above your target orbit height and circularize at perapsis.

[comiquaze]

Thanks guys, I'll try that out when I back from flying for the job.

I'll let you know how it went.