Economic Vall Refueler

[Red Dwarf]

I'm running a mission to the outer kerbol system, full up. I've got a giant mothership, atmosphere probes, a heavy science lander, the whole shebang. Thing is, my mothership doesn't have quite enough delta-v to make it out to Sarnus in one go. So, to counteract that problem, my science lander is fully equipped to refuel the mothership. My mission calls for a pit stop in the Jool system, to top up the tanks and test out the hardware.

I've been testing the lander on Vall, and I feel like I've run into a wall. It carries a full science suite for airless worlds, as well as a refinery and the big ore tank. I need it to be able to make orbit from Vall's surface carrying the full ore tank, drop that off at the mothership to be refined, and then make it back down to the surface to mine the next load. I've been able to do this on the Mun, but Vall, being larger, is foiling those designs. Now, no matter what I try, my landers aren't performing the way I need them too. And, if they do, they're massively heavy, bigger than my mothership can manage.

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So, my question for the forum: does anybody have a design which can pull this off? What is it that I'm doing wrong?

[Guest]

Remove the refinery from the ore hauler, or refuel someplace like Bop or Pol?

[Mikki]

Remove the refinery from the ore hauler, or refuel someplace like Bop or Pol?

I totally agree... i consider mining Vall "UNREASONABLE"...

[spudman2]

I don't have advice, but I would like to say that I'm the same boat as you; between "enough dV to do anything useful", "enough TWR to leave the ground" and "enough capacity to actually refill something", I can only get two at a time. I like your designs, though. Very clever.

[Captain Sierra]

Honestly, while refueling is more straightforward, you'll expend more delta V braking, then ejecting, from Jool and in turn Vall than you'll gain in benefit. Your best bet is cut the first 800+ dV off by refuelling at Minmus with existing infrastructure and/or taking a Jool gravity assist. Harder to set up, the gravity assist will save you more dV than attempting a refueling op.

[KerikBalm]

http://forum.kerbalspaceprogram.com/threads/121794-Has-anyone-managed-to-create-a-miner-capable-of-net-gain-to-orbit-on-Moho?p=1950595&viewfull=1#post1950595

Moho takes just a bit more dV than Val.

For moho, it is much better to take the refinery down to the surface.

Also, I think you should use 1x poodle rather than 4x LV-909s. 10kN more thrust and 0.25 tons less mass.

Plus your Isp is 5s better.

These aren't major differences, but it will help.

That said... I'd probably opt for a refueling craft on Laythe.... perhaps a dedicated tanker that isn't just for that mission.

Val's dV requirements are essentially 860x2.

You need 860 to get to orbit after mining, but you also need to haul enough fuel back up to replace the fuel you used getting down.

At Laythe the atmosphere will do that for you (so you can land with pretty much empty tanks), and you can get up to ~1,300 m/s (or better in 1.04 I hear) on very efficient air breathers...

So you only need the last 600m/s or so to be done on rockets, which is far more economical than lifting off of Val....

But I'm not sure how much extra dV (if any, oberth and all) it will take to travel to your next destination.

I would make a dedicated mining+ refinery+ tanker ship that doesn't go with the rest of the mission, and just stays in the Jool system to refuel things there.

[Vanamonde]

How-to question moved to the how-to subforum.

[bigcalm]

Here's what I'm trying out on Moho (which has slightly higher g but otherwise broadly similar) - figures are with a full ore tank:

For Vall you probably want to throw away all the solar panels and replace them a lot of nuclear isotopes.

How you get it to Vall is somewhat harder. My current system is to have 2 large shunts - one to take the lander empty of fuel (~27tons) and one to take enough fuel to make the first landing, docking them together in orbit.