Ore to Kerbin Missions

[Wcmille]

Trying to think through my options for running ore-to-Kerbin missions. I have nice flat bases on Mun and Minmus. I could make a rocket that does the whole thing, or I could just haul the tanks around across craft. How are you doing those missions?

[Magzimum]

The last time I did a big refuel mission, I just attached some disposable mining gear to the bottom of the mothership, and landed the mothership itself. That was surprisingly simple compared to all other variations that I have tried.

Spoiler: two pics of that mothership.

Spoiler

Mothership landed. Mining gear in the middle, at the bottom.

After take off, and after consuming all fuel in the tanks (incl. the ore), the mining gear got separated.

This was from a Jool-5 mission - it can be found here.

I tried all kinds of refueling strategies: stationary mining, with a rover, or a tanker-rocket, that carries the fuel to where it's needed. I also once carried the ore - but this solution requires by far the least additional infrastructure. Of course, it totally lacks flexibility - it's just this one mission.

 

[edit] Hmm... or did you mean the contracts where you gotta mine ore from planet/moon A, and deliver it to planet/moon B (in your case Kerbin)? I never do those, but I would recommend to make the rocket as simple as possible - probably still with the mining gear attached to it - possible even disposable. 

Edited January 4, 2017 by Magzimum

[Wcmille]

Yes. Bring 550 Ore to Kerbin from Mun, in this case.

[Snark]

28 minutes ago, Wcmille said:

Trying to think through my options for running ore-to-Kerbin missions.

One thing to bear in mind-- be sure you read the precise fine print of the contract.  It may require you to land ore on Kerbin... but it may not.  It might only require bringing the ore to Kerbin's SoI, in which case merely escaping the SoI of wherever-you-mined-it is sufficient.  Just make sure you're not actually doing more than you have to, unless you're so inclined. 

Also... be aware that if the ore contract does say "land on Kerbin", it means land, on terra firma.  Splashdown doesn't count.  Has to be on land.

It's also worth noting that the game has no concept of "where did this particular ore come from?"  It knows where it's from as it's being mined, but once the ore is out of the ground, it's not "ore-from-Mun" or "ore-from-Minmus".  It's just "ore".  This has important implications for contract completion criteria.

For example,

6 minutes ago, Wcmille said:

Bring 550 Ore to Kerbin from Mun, in this case.

^ No.  There exists no such contract in the game.

It's understandable if you think that that's what the contract is, but it doesn't actually say that.  Take a close look at the actual contract.  It probably says something like this:

1. Mine 550 units of ore from the Mun.
2. Have 550 units of ore on your ship.
3. Land your ship on Kerbin.

Note that nowhere does it actually say that the 550 units of ore you mine in step 1 have to be the same units of ore that you have on your ship in step 2.  Anyone would be forgiven for thinking that-- it seems to be implied-- but it's not actually stated, and the game doesn't enforce that... because it can't, since the game doesn't know where the ore came from once it's mined.

This means there's a sneaky way to complete such contracts, if you're so inclined.  You can mine 550 units of ore on the Mun, and do whatever you want with them (for example, convert them to LFO as you mine them, or whatever).  As soon as you've extracted 550 units-- regardless of what you've done with them-- then you've completed criterion #1.  If you then just launch a new ship at KSC that happens to have 550 units of ore in it... then it will satisfy criteria #2 and #3 the instant it hits the launchpad.  You don't even have to take off.

Yes, it's a bit of an exploit, so some might consider it "cheating" and prefer not to do that.  Just letting you know that the option is there. 

[Wcmille]

[Fearless Son]

Absent using the exploit that @Snark described above (thanks for that) I find getting the ore back to Kerbin slightly more challenging than a typical Kerbin return, because the craft tends to have a much higher mass than it usually would when doing its terminal deorbit.  Even if all the fuel has been expended, the ore itself is quite heavy, which means it takes more total force to aerobreak than an unladen craft, which means it penetrates into the thicker atmosphere at higher speed, which means more heat generated in a shorter amount of time, etc.  That the ore containers are more delicate than most other structure parts complicates things, if only a little.  

The lesson being that you need to be a bit more careful about the design of a craft meant to get the ore to the surface than you would with most other craft.  It needs to be well heat-shielded, and not have too many parts that might stick out and get burned off.  It needs to be able to slow itself down more than you might expect from body drag alone, so A.I.R.B.R.A.K.E.S.  go over well, as do drogue chutes.  All this in mind, my advice would be to have the ore transported back to Kerbin orbit (either by a drilling mothership or just a transporter that docks with a drilling station or mobile rig,) park there, and send up a descent vehicle to dock and transfer the ore before landing it back on Kerbin.  This would be the most reliable method I would think.  

Actually sounds like an ideal mission for a spaceplane that launches with empty ore tanks in a cargo bay, come to think of it.  

[Snark]

8 minutes ago, Fearless Son said:

I find getting the ore back to Kerbin slightly more challenging than a typical Kerbin return, because the craft tends to have a much higher mass than it usually would when doing its terminal deorbit.  Even if all the fuel has been expended, the ore itself is quite heavy, which means it takes more total force to aerobreak than an unladen craft, which means it penetrates into the thicker atmosphere at higher speed, which means more heat generated in a shorter amount of time, etc.  That the ore containers are more delicate than most other structure parts complicates things, if only a little.  

The lesson being that you need to be a bit more careful about the design of a craft meant to get the ore to the surface than you would with most other craft.  It needs to be well heat-shielded, and not have too many parts that might stick out and get burned off.  It needs to be able to slow itself down more than you might expect from body drag alone, so A.I.R.B.R.A.K.E.S.  go over well, as do drogue chutes.

^ Excellent advice.

I find that the 10m inflatable heat shield is great for this-- it has so much surface area that it works really well for braking those heavy ore ships.

Another thing to be careful of:  you really, really don't want to land in water.  Not only does it probably not count for contract completion... but also, full tanks are exceptionally dense compared with most KSP components, to the point that it's not uncommon for an ore vessel to actually sink in water.  Which is such a royal pain... because once you start sinking (agonizingly slowly) through the water, you're basically stuck.  Game won't let you switch away or recover, the same way it won't let you switch away or recover when flying a plane.  So you have to wait until the ship either reaches bottom (in which case you can recover or switch), or sinks below its maximum-tolerated-pressure (in which case it explodes and you're off the hook).

And that takes for-frickin'-ever, even if you're at the maximum 4x physics warp.  So you have to just sit there twiddling your thumbs and glaring at the screen for a really, really long time.  It's incredibly annoying.

(Of course, one option would be to right-click on the ore tanks and dump the ore, which they can do.  That'll make your ship buoyant, so you can recover it as soon as it bobs to the surface.  It means you lose the ore, but hey, the contract wasn't completed anyway.)

[Sharpy]

Bring 550 ore from Mun, land on Kerbin?

 

Drill 550 units of ore on Mun. Jettison or remake into fuel, or whatever. Doesn't need to be in one piece - the tiny ore container emptied periodically or used to produce fuel continuously is sufficient.

Go to VAB. Pick an ore container, rightclick, fill with 550 units of ore, launch.

Contract complete.