Vall miner advice

[Ultimate Steve]

After much debate, I decided to use a Vall refueler system to refuel my ships for my Jool mission coming up. The system would work like this: The Vall miner would land on Vall, mine the ore and refuel itself, then take the ore up to Vall Station, where passing ships would refuel. Unfortunately I am running into some problems with my miner. The first version made orbit fine, but after converting the ore it mined into fuel so it could mine again, it only netted 20 ore (). The lander had plenty of fuel left over, and had boatloads of TWR, so I added more ore tanks. However, this version won't get into orbit now. So I decided to post here for any advice related to Vall mining: If I should go smaller, or bigger, or change the engines, or anything.

Here is a screenshot of the lander I am using:

Spoiler

 

Any suggestions? Thanks in advance.

[Foxster]

How about putting the miner bit on the surface and leaving it there? Then have a fuel tanker carry fuel to orbit. You'd need a rover with a fuel tank and a claw to run fuel from the mining base to the tanker when it re-lands.  

[Plusck]

My mining setup: album. This works very well for Moho, so it should work for Vall too.

For a hands-on experience: quicksave with a couple of seconds to get bearings

Edited April 28, 2016 by Plusck

[Norcalplanner]

I used a Kethane-powered mining rig for my Jool-5 mission back in the day, but haven't done a modern mining rig, so my comments may be off.

My initial impression is that your craft is very large and very heavy.  How much fuel are you trying to net per run?  Just making some minor changes like a lighter capsule and more efficient vacuum engines would probably help things a fair bit. Efficiency of rocket-SSTO designs depends a lot on keeping the weight down and the Isp up.  

Deciding whether or not to keep the ISRU converter on the craft is a big decision, and affects what you may find fun (or not).  If you can figure out a way to not carry around that extra dead weight, it would help a lot.  If you want to convert the ore to fuel in orbit, the most flexible setup would be to have one ISRU unit on the surface, and another unit in orbit - that way, you can top up fuel tanks at both ends, and make sure they're only sized large enough for a one-way trip.

You may also want to do some number crunching and see whether it makes sense to either go the full LV-N route, or maybe do a hybrid ship with LV-N main drives, then some Poodles or Terriers.  The LFO engines which kick in only when initially lifting off of Vall when you're fully laden.

[HMIC]

@Ultimate Steve Agree with what's been said so far.  My take is to have an ISRU converter tanker in low Vall orbit, that way your Vall miner would need very little dV to get into orbit and deliver this ore and fuel to the tanker.  From the tanker you can pick up the fuel you need and take it to the station.  OR!! Put your station on low Vall orbit and use this as the tanker.  

Divide the responsibility of you mining operation by using various ships and give them specific roles.  The more you do in orbit, the less dV you'll need. So you can focus on your main concern which is the mining rig for Vall.  

Example:

For Mun, I have a huge stationary tanker with an ISRU, fuel and ore tanks at 10km orbit (the lower the better). If you're in orbit and will not be required to move, dV is not a factor neither weight. You're not going to move, so the storage part is complete in orbit.  The mining rig's objective is to deliver ore to the tanker at 10km. The Mun's gravity was giving me a hard time on ascent, so instead of making the mining rig with parts to refuel itself which in turn would make it very heavy,  I divided this into two more ships and roles.  Made a ground mining rig and an ascent vehicle.  Since the ground mining rig will not be required to go to orbit now, you can make this a huge trailer mining truck and overload it with all the refueling parts, wheels and drills may you need, and have this monster resupply the ascent/descent vehicle when landed on the ground with fuel and ore by using a Claw.   

I only use stations for science and housing kerbals that need pickup to go home, arrival from kerbin or land at Mun.  This is like your airport or train station hub.  If you want fuel and ore at your station, have it tranfered from the 10km orbit up the station, dV and weight here are not huge factors, so hauling materials should not be a challenge.

That's about all I can spare for this.

 

Any other questions or comments, fire away. 

[Frank327]

One question I have about your miner is why do you have so many ore tanks on the same vehicle that has an ISRU converter? If I remember correctly, ore is twice as heavy as the fuel it will be turned into. So why not have a single ore tank and the rest be fuel tanks and do most of the converting on the surface of vall. You'll be able to ship more fuel and be less heavy and waste less dV getting into orbit with your payload.

Another option as mentioned is using lots of ore tanks and putting the ISRU converter into orbit on the refueling station. Then you won't have to take the 4t converter to the surface of vall and back up again. But on relatively high dV moons like vall and even the mun I would prefer only shipping fuel and not raw ore from surface to orbit because you'll burn so much of it in transport. Shipping ore around on minmus or one of the smaller jool moons is much easier and much more profitable.

Actually I think on vall it would be most profitable to divide the operation into three parts. First, a landed miner + converter that doesn't go into orbit anymore. Secondly a fuel transport that takes the fuel from the miner and transports it to orbit. Thirdly an orbital station where you can store the fuel for use. Docking the fuel transport and the surface miner together is going to be the toughest part of the operation.

[Plusck]

6 hours ago, Frank327 said:

One question I have about your miner is why do you have so many ore tanks on the same vehicle that has an ISRU converter? If I remember correctly, ore is twice as heavy as the fuel it will be turned into. So why not have a single ore tank and the rest be fuel tanks and do most of the converting on the surface of vall. You'll be able to ship more fuel and be less heavy and waste less dV getting into orbit with your payload.

Ore and the converted fuel you get per unit of ore have exactly the same weight. Yes, ore weighs twice as much but each ore gives two fuel (or 0.9 fuel and 1.1 ox if you convert using the LF-Ox option).

Therefore the only consideration is the weight of tanks, the weight of engines, the weight of additional items and the fuel/ox mix you need. Mining ore and converting in orbit is best if you want to ensure the best LF-Ox-monoprop ratios, since it's hard to optimise your system in advance without doing a ton of calculations to get the right mix of tanks. However it does mean that you have to ensure your carrier has enough fuel to get up to orbit.

 

19 hours ago, Ultimate Steve said:

Here is a screenshot of the lander I am using:

Any suggestions? Thanks in advance.

There's a huge amount of unnecessary weight (Mk1-2 pod, tons of batteries), inefficient engines (only 300 I_sp), and unnecessary carting of ISRU and drills to and from orbit. Really what goes up to orbit should only be the most efficient engines (aerospike or poodle, depending on total mass) plus tanks, plus minimal crew seating (command chair or lander can), plus minimal control stuff. Also I don't really see the point of wheels, since that doesn't look very drivable.

[Ultimate Steve]

Thanks for the ideas, I will redesign soon. When I'm finished doing what I'm doing right now.

@Plusck I am using the wheels because the normal landing gear has proven to be a bit... difficult.

[Reactordrone]

It's worth working out how much fuel the vehicle needs in order to land and only load it with that much. If you've still got 30t of fuel in the tank when you land that's two ore tanks worth of fuel that could have stayed in orbit. Leave just over 20t of fuel/oxidiser in it and you should be able to land.