Tips on a moho mission

[Guest]

If you got any tips on Moho please do tell! I need help the most on an orbiter

[VoidSquid]

Been there with some Kerbals the other week, the key was (is) having plenty dV, the more the better.

Getting there isn't much difficult, the issue though is to be able to break the insane velocity, in my case, it was some 3000 m/s.

I found this thread quite helpful:

 

[Guest]

2 minutes ago, VoidSquid said:

Been there with some Kerbals the other week, the key was (is) having plenty dV, the more the better.

Getting there isn't much difficult, the issue though is to be able to break the insane velocity, in my case, it was some 3000 m/s.

I found this thread quite helpful:

 

Okay the main problem I have is getting back. I have had two missions there before but one failed and one worked BARELY

[VoidSquid]

How I did the mission:

I sent two vessels: one lander with a 3-Kerbals pod, having all the scientific equipment plus being a harvester, this lander (after doing the experiments and harvesting fuel) stays in low Moho orbit at the end. The other ship being my "taxi" for returning, which I did refuel using the first vessel. The taxi naturally has way less weight, hence after refueling easy to return.

Edited August 29, 2019 by VoidSquid

[Zhetaan]

2 hours ago, The Doodling Astronaut said:

If you got any tips on Moho please do tell! I need help the most on an orbiter

There are three popular ways to orbit Moho that I know aside from taking a monstrous amount of delta-V and trying a Hohmann transfer:

One:  Ignore the transfer window, and instead attempt to rendezvous with Moho's orbit at its ascending or descending node with Kerbin's orbit.  Once there, burn retrograde to lower your apoapsis for an encounter with Moho on your return to this point.  There are varying schools of thought on whether you should transfer to Moho's ascending or descending node, because the difference in velocities when you do finally encounter Moho can be large, but this manoeuvre saves you the trouble of needing to correct your inclination and usually makes capture to orbit easier.

Two:  Try for an Eve assist.  This does not necessarily mean a gravity assist:  though a double Eve gravity assist (meaning you transfer from Kerbin to Eve, fly by Eve a second time, and then go to Moho) can save a lot of delta-V, Eve (especially with Gilly) also makes a good staging point for a vessel.  If it only needs to reach Eve instead of Kerbin, then it doesn't need quite so much delta-V in the first place.  I've seen a few grand tour vessels that stopped the mothership in Eve orbit and sent a lander to Moho and back again.  A miner on Gilly that generates propellant for your return while you go on to Moho makes this option even more attractive.

Three:  It's essentially the same as @VoidSquid's answer of sending a vessel with half the delta-V and mining equipment to make the other half.  This is completely compatible with either of the first two options, but it changes your mission profile enough to merit a special mention.  Whether you break that into multiple vessels is up to you, though it should be obvious that the need for orbital scanners complicates the mission profile somewhat without at least a detachable scanning module.  I've seen people send miners that remained on the surface; I've seen stage-able mining equipment, and I've seen people bring it back with them.  If you do choose this option, then remember that solar power is not necessarily the best option for Moho; the nights are more than sixty days long.

 

Insofar as returning to Kerbin is a problem, I'd need to know more about your specific situation.  What do you mean when you say that one mission worked barely?  Did it nearly run out of propellant?  Did you nearly miss the transfer?  Was it difficult to find a transfer in the first place?  The answers to these and similar questions help, and they will inform your next mission.

Edited August 29, 2019 by Zhetaan

[VoidSquid]

47 minutes ago, Zhetaan said:

though it should be obvious that the need for orbital scanners complicates the mission profile somewhat without at least a detachable scanning module

Good point, yes, that's why I sent three rockets in the previous transfer window, two rockets with three relay sats each for polar and equatorial orbit, and one rocket with all the scan sats, including ore scan.

[Guest]

@VoidSquid and @Zhetaan
My goal is to make this mission single launch and just Apollo style. With no ISRU or mining

[VoidSquid]

6 hours ago, The Doodling Astronaut said:

My goal is to make this mission single launch and just Apollo style. With no ISRU or mining

Ah, I see, different mission parameters then.

For the fun of it, I built a little ugly contraption of an unmanned lander where just the pod (Octo 2) plus a few other essential parts could return to Kerbin, no ISRU. Even that thingy with almost zero payload took me a while to build, and it barely made it back. I've no idea how I could build a rocket within your mission parameters.

[Empiro]

Moho's orbit is quite elliptical and has a significant inclination.

Eve assist is definitely the cheapest way, as it can both correct your inclination and slow you down. However, it requires careful planning and lots of patience as you need to encounter Eve right at Moho's AN or DN, and you may need several assists.

If you don't want to use an assist, the keys to success are:

• Capturing close to the PE so your speed difference is lower
• Correcting your inclination as far from Kerbol as possible, since inclination changes are cheapest when far away / moving more slowly.
• One other thing to consider is that Moho's argument of periapsis is 15 degrees, meaning that its AN is 15 degrees off from the PE, while its DN is 15 degrees off the AP.
• This means that you should combine maneuvers and both lower your PE and correct your inclination at its DN (which from your perspective is actually the AN -- confusing, I know)

I like to use the following procedure (sorry if some of the steps are a bit difficult to understand):

1. Launch a craft in orbit around Kerbin with 0 inclination, and place a maneuver that brings you barely into a solar orbit.
2. Set Moho as a target and note where the AN is.
3. Warp until Kerbin is about a day away from the AN point. Now, place another maneuver node that has both prograde and normal components so that the maneuver eliminates the relative Moho inclination AND places your PE so that it is touching Moho's orbit. I've found that it's around around 2000 in the prograde and 1000 in the normal direction. However, thanks to Pythagoras, this only costs a total of around 2300 m/s.
4. If you want to maximize savings, note the trajectory after your escape burn, and launch a ship that matches the escape inclination exactly. This saves about 200 m/s as you won't need to burn any in the normal direction.
5. Perform the maneuver. Accuracy is important, so make any corrections afterwards to put your PE so that it's barely touching Moho's orbit.
6. Place one maneuver at your PE, and place another node ahead of that one. Click the next orbit button a few times for the second maneuver node. You'll see the close encounter markers move around. Click until you find one where you are close to your PE, and Moho not too far ahead of you.
7. Now, go to the first maneuver node and start pulling the retrograde direction. You should see the encounter marker for Moho move closer to you (you're lowering your AP and decreasing your orbital period, so you're catching up to Moho). You should be able to get an encounter without burning more than 100 m/s, since any change in orbital period is multiplied by several orbits.
8. Perform the maneuver. Again, accuracy is fairly important.
9. Wait a few orbits and you'll get that encounter your second maneuver node had predicted. and once you're 1/4 of an orbit from Moho, do a correction maneuver that puts your PE close to Moho.
10. Finally, capture at Moho. This step should take less than 1900 m/s, putting the total delta-V cost around 4000 or 4200 m/s. This is about as good as the optimal transfer time according to the transfer planner (and you don't need to wait for years).

Edited August 30, 2019 by Empiro

[OrbitsR4Sissies]

I weaponized Empiro's and others' advice here to positive effect.

Meet the Pioneer; a 4200-or-so delta-V spacecraft to fulfill a landing contract on Moho, Gilly, the Mun, Minmus, Duna and Ike using a single vessel: a 2200 dV lander it carries in tow.

I was no stranger to Moho's challenges. I've sent many of a spacecraft there and just bulked up with ridiculous amounts of fuel from Kerbin, typically one-way probes, worse for Kerbal missions.

I didn't want to do that here because I knew I would save a bit by refueling at Gilly. But I had never left for Moho from Eve before. So that's why I'm here.

After Pioneer did its thing alone at the Mun and Minmus, a refueled tanker stage and a similar one with a mining ship headed to Eve. There, refueled one of the two transfer stages, reconfigured as a depot over Gilly. The lone Kerbal on Pioneer is Bill, the engineer, picked because he can improve mining and converting efficiency and repack chutes after Duna for his Kerbin return.

The transfer stage had enough dV to leave Eve just before the Moho AN, ignoring the transfer window. I set the DN orbit to just reach Moho's orbit.

First burn from Pioneer at Moho AN, around 1100 dV, partially corrected inclination while also setting up the first Moho encounter.

Second burn, flying around 12000 m over the North Pole, again for about 1100 dV, all but fully corrected inclination and reduced Pioneer's orbital AP.

Burn 3, for 331 dV, made shortly after the first flyby, sets up a new encounter...

Pioneer entered Moho orbit with a very modest 461 dV burn.

Now, I did have to send two tanker ships to refill Pioneer in orbit...mostly because I was lazy and panicking before I learned what I could do. I could've sent another mining ship instead instead of two ships (one that burned 10x more fuel than Pioneer to get an orbit).

Returning from Moho to Eve, I generally reversed the steps, although I'm recalling this from bad memory. Used 1000 dV in the Moho tanker stage to just squeak out of Moho near its DN. Made a partial inclination burn around 1300 dv at Eve's AN, I think. A second burn at Eve's DN for an encounter at its AN left the spacecraft left even more fuel to spare on capture burn, thanks to Eve's gravity.

Pioneer, refueled, now has a comparably easy trip to Duna to complete its contract. Thanks for the great information, everyone.

 

Edited September 6, 2019 by OrbitsR4Sissies
Clarifying

[dire]

Just for kicks I threw together an apollo-style rocket that, on paper at least, looks like it can get to Moho and back with flags and footprints. Its mothership has 10k dV and its two landers have like 2400-ish each. DV might change quite a bit depending on when and how satellites and landers are deployed, but at a minimum you should be able to reserve one lander as an expendable drop-tank for the return home and have loads of dV to spare.

If anyone wants to give this a test run let me know how it goes. I remembered parachutes on the return stage this time!

https://kerbalx.com/direstorm/Odin-24-XL-1-Huginn

Edited September 8, 2019 by dire

[Barefoot Friar]

@OrbitsR4Sissies May I please have the .craft file for your miner?

[OrbitsR4Sissies]

15 hours ago, Barefoot Friar said:

@OrbitsR4Sissies May I please have the .craft file for your miner?

Here you are. First time anyone's asked me for any craft, so you motivated me to get my KerbalX account set up.

https://kerbalx.com/OrbitsR4Sissies/Pilgrim-Mining-Lander

The miner supports the Venturer, a long-range interplanetary spacecraft with a 2400 dV lander. As noted above, I put a miner at Gilly and, later, Ike and Pol to ensure the Venturer's lander can land on most anything and return except Kerbin, Laythe, Eve, and Tylo.

https://kerbalx.com/OrbitsR4Sissies/Venturer

[Barefoot Friar]

Awesome.  Thank you!