How to Land and Return from Moho Without MechJeb (with a few comical missteps)

[sdrevik]

I played the KSP beta and got stuck on Moho- the best I could do is a flyby and a one-way suicide landing. With the improved fuel transfers in 1.0, I was bound and determined to use the opportunity for refueling to return surface samples from Moho. No mods. I’m like Kevin Bacon in Apollo 13, when he jumps to “I’m going to manual†in the simulator, and everyone rolls their eyes before they are simu-killed on re-entry. That’s me.

First, I thought, I remember that need fast stopping power on Moho injection, and nuclear engines are supposedly “nerfedâ€Â, so let’s build a return lander based on chem rockets. I have a fueling station running on Minmus, so I can get off Kerbin, top of the tanks, and go there.

For the lander design, I should also say, I like landers with full Kerbin return capability, rather than light landers. I like to bring down Science Jr, lots of goo, etc, so if I’m bringing all that weight, why not a single Kerbin capsule? If I’m going down with all that, and I’m bringing all that weight back to Kerbin, why not make it a full return vehicle? That’s worked for all my other Duna / Jool moon / Eeloo missions. And without mods, docking is a pain. And with the ability to not go down with my Moho return fuel, it's a fine strategy.

So- first issue, single Kerbin capsules don’t handle full size docking ports well, which is what I have on my Minmus fueling station. No problem, I stick an empty Lander Box on top of the capsule, connected with the capsule’s Junior docking port, and the big docking port on the outside of the lander. Dock for fuel, transfer, and jettison for the rest of the trip. I know I’ll need another refuel tanker sent to Moho, but I can design that later with a Junior docking port.

I get to Minmus, spend a good 30 minutes docking, and while transferring fuel, I run my calculations on my dV so far. Based on what I can carry, I can barely transfer to Moho, but NO CHANCE I’m going to be able to stop when I get there. Damn. OK, jettison the lander box portion still attached to the fueling station, so I’ll have a Junior docking port for the next design, return the Kerbal.

New design- nuclear rockets with liquid fuel. Back of the napkin calcs (no mods) indicate with a refuel, I should be fine, as long as I send another tanker to Moho for the return.

Up it goes, and we prepare to dock with the fuel station. Hm… can’t select the target. When we come back into daylight, I realize the problem- the original Capsule had a Junior port, but the back side of the lander did NOT having a flipped port to mate to- VAB just attached the lander to that port as is. I have NOTHING to dock to!!! Well, that’s just as well, because I realized on the way that my fuel base is mostly designed around fuel/ox mix- I’d strip the base of all the regular fuel and leave lots of oxidizer.

Notice anything missing on the can??? Oh yeah, the friggin' docking port!

I was really feeling dumb at this point.

Solution- make a new refueling tanker, similar to the one I will send to Moho, dock it to my nuclear Moho vehicle in outer Kerbin orbit, transfer and then be on my way. For the new tanker, I used pretty much the same design as the lander, without the legs, an OKTO in lieu of a capsule, and no science. The lifter is a stage of 5 orange tanks with Mainsails, a second stage of 5 more orange tanks with Swivels, where the outer tanks can be jettisoned and the center tank used by itself.

So that worked well- too good, in fact. I had 2/3 of an orange tank from stage 2-B on each system. So I joined them nose to nose for the journey to Moho, transferred what I could from the tanker’s orange tank to the Moho vehicle and began the burn. In fact, I first used a little of the tanker’s main engine and remaining fuel for the first part of the transfer burn. Needless to say, when that fuel was done, turning this monster around took a while, but I had plenty of RCS fuel. Docking the two of them was incredibly painful, as you can imagine. But I did it… all manually. (Drop mic).

Lesson learned- engines had to run slow (20% to 25%) throttle to avoid oscillating the two sides to death, as they were only joined by a narrow Junior docking port. Since most burns were long windows anyway, this was just more an exercise in patience (many burns were 15-20 minutes of real time). Once I placed into orbit with enough nuclear fuel to land (but not lift off yet), I began to plan Tanker#2.

And I decided to give in. I installed MechJeb2.

ONLY for docking intercepts, mind you. I will still do all my launches and transfers manually. But 30-40 minute docking episodes just aren’t fun anymore. I know I can do it, and I have better things to do with my time.

I flew my fuel tanker to Moho (new design with some serious lift),

Fuel tanker to go to Mojo. Note that Mk1 fuel tanks clustered in 4-way symmetry overlapping. It worked!

..got it into orbit, docked, and gave the lander just enough fuel for descent and ascent. Then I found a strange bug- when I used “G†to extend all 4 landing gear, my ship would explode. But they touched nothing. Restarted KSP, still the same result. So I manually extended each leg one at a time. No problem. Go figure.

The landing was a bit hard (more gravity than expected). They say any landing you can walk away from is a good one, but this was cutting it close, losing two landing legs and several struts, but at least I was upright. Those landing struts just didn’t want to come back to Kerbin for some reason, they had a death wish. So be it, I was done with them. Should make aerobraking interesting, though.

Leaning Tower of Kerbal.

Clearly, takeoff was interesting. I got up into a very low orbit, and took the tanker down to meet them. Then I gently (10% thrust to avoid horrible oscillations) moved the pair out, transferring fuel as I went. I couldn’t have been happier when I finally got to jettison the tanker and use full thrust.

VERY wobbly!!! Keep throttle < 10%.

Waited for Moho periapsis and node transfer window (only 87 days) and blasted off for Kerbin. I used 8 cycles of aerobraking at 56 to 47 km to get into a low enough orbit to move one of my Science Labs into place. Actually, it was such a polar orbit, I just launched a new science lab.

Then I found out my design only had 2-way symmetry on the RCS, not 4-way, which makes autodock useless. Tried it for a while by hand, then just decided to launch ANOTHER science ship with the additional RCS thrusters. Autodock worked like a champ. LOTS of data for the lab to process, these guys will be up there a while. But now I have the science tree 100% filled out, and I have *finally* conquered Moho.

Lessons learned:

• If I had it to do over again, I would have taken the additional weight for the CM to have a full size docking port, in the hopes they would be more structurally sound and less oscillation. Maybe.
  
• Moho has more gravity than you think. Start braking well above 14km.
  
• Check your designs (4-way symmetry on RCS, etc), although some bugs will just appear. My landing legs bug was NOT evident on the pad at Kerbal when tested.
  
• Using fueling tankers for the transfers is a fine strategy, but getting the fuel to Moho takes a BIG lifter.
  
• Unlike some forum posts say, nuclear engines are fine for Moho insertion, but you’ll need more than one. Three or four are fine.