Looking for some advice on Mun ops please.

[markadeane]

Hi all,

I'm in the early stages of Mun exploration, and have a few questions I'm hoping some of the seasoned vets can assist with!

I've set up a Mun orbital outpost at 150km and plan to use this as my staging point for conducting multiple descents and ascents using the stock 'super heavy lander'.

My first descent/ascent, conducted with MechJeb, left me out of fuel about 4km from the outpost, and I was a bit marginal on monopropellant by the time I got to docking.

So I've been analysing why things didnt work, the first thought is that my Munar orbital insertion has left me with an orbital inclination of 180 degrees. I'm not sure if that's as big an issue as it is back on Kerbin but as I understand it, you're better off if your orbit is in the same direction as the roation of the body you're orbiting.

So, Question 1: Should I sacrifice some of my fuel stockpile to to a 180 degree inclination change?

My other thought was whether there's way to calculate a 'sweet spot' for the optimum orbital altitude to minimse fuel use on round-trips to the surface and back. Is anyone able to share a calculation or tool that does such a calcuation please?

Finally I wondered whether the super heavy lander might actually be a poor choice of vehicle in the first place, and I'd be grateful for aynone's advice on better alternatives.

Thanks in advance everyone!

mark

[Vanamonde]

Orbiting retrograde means the approaching ship starts with a deficit of 2x the world's surface rotation speed, though on Mun, which is tidally locked, that's not so much. However, you'll have to pay that penalty for each and every flight to your station, both on the way up and the way down. Reversing your station's orbit would fix that, but would also take godawful amounts of fuel. I think you might be better off sending a whole new station into a prograde orbit. Whether you do that or not, 150kms is quite a high orbit, which again means burning more fuel on each trip to the station and back. Since Mun has no atmosphere, I believe the optimal orbital height would be the point at which your lander can reach orbital speed on a single burn at full thrust, which would, given perfect piloting, put it right at the station with a matching velocity, and no waste. That altitude would depend on the thrust/weight ration of your lander. All in all, 30km is a pretty comfortable altitude at which to fly rendezvous from Mun's surface, not for ideal efficiency, but as a compromise of efficiency and piloting difficulty.

[Sovek]

Your station need not be so far out, 150km is quite a bit for Mun. The rotation of Mun is minor, by about 9 m/s... so 18 m/s of ÃŽâ€V. Not worth the hassel.

The other problem is probably your landing and take off. I have no idea how much ÃŽâ€V the "Super Heavy Lander" has, but if its around 1.5km/s ÃŽâ€V, thats about enough for one round trip before refueling, assuming the station wasnt so high up. But anyways, landing is best done if you burn once to slow down and stop, just meters above the surface (MJ2 can tell you when to do your "suicide burn"), take off... thats something I've never done well... yet.

[Merinsan]

For take off from the mun, you just want to throttle up full and tip over to almost the horizon almost immediately, depending on your TWR, however with a target at 150km, you probably don't want to go so extreme. I'd be putting the station lower down. In my case, my station orbits the equator prograde, so I launch and tip over towards 90 degrees. I seldom try to rendezvous from launch because I am lazy and I probably have twice as much fuel as I need, besides it doesn't save much. I aim for a at least a 5km initial apoapsis and a speed of about 500m/s from the initial burn. I then circularize and plan the rendezvous with the station.

Also, my Mun landers often use nukes, simply for the fuel efficiency. You don't need much thrust, and the nukes work well for big landers.

[Dictator Dan]

Given the Muns lack of atmosphere, you could lower station quite a bit, and I agree with Vanamonde, it would probably be easier to send a whole new station out.

If you arnt looking to move large amounts of fuel up and down, you could probably get away with a pretty small lander. For my Mun base I have 3 landers, one is just a probe, small engine and fuel take and a Hitchhiker to move 4 Kerbals up or down, one for fuel movement, and one operates as a descent module for new habitats sent to the Mun. Remember every unnecessary part you bring to the surface, and lift back up takes fuel.

[Asheron04]

Mechjeb also is not very fuel effecient in my opinion. I do my landings manually.