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# Drill to ISRU ratio for asteroid mining

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What is the most efficient extraction ratio of 'Drill-O-Matic' Mining Excavator to Convert-O-Tron 250 for asteroid mining? What I mean is how many drills are needed to saturate an ISRU with 2 converters active. I spent 1/2 an hour trying to look this up for a design, but decided to give up and ask. IIRC correctly the engineer level can be reduced out of the equation.

Alternatively is it more effective to fill an ore tank quickly (with more drills) so you can avoid running drills on rails and avoid wasting asteroid ore?

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A large drill has a base rate on asteroids of 5 ore a sec, which means it can power 10 recipes.  A small drill has a base rate of 1 ore per sec, so it can power 2 recipes.

To get more fine grained:

The base rate for the liquid fuel + ox mix is 0.5 ore a sec for .55 ox and .45 liquid fuel.

The base rate for ox only is .55 ore a sec for 1.1 ox.

The base rate for liquid fuel only is .45 ore a second for 0.9 liquid fuel.

The base rate for monopropellant is 0.5 ore a sec for 1 monopropellant.

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10 hours ago, ajburges said:

for asteroid mining?

On moons, multiple drills often can't keep up with even a single ISRU.
Asteroids have a much larger ore content than the usual planet/moon where one drill can easily provide enough ore for many ISRUs, especially with a high-level engineer on board. Power becomes the limiting factor, so bring enough fuel cells.

Here's a mining rig I used in an older sandbox that I tuned to the best ratio. It can turn an asteroid into fuel faster than I could juggle the tanks I'll have to search for the craft file but it looks like about 10 ISRUs to 3 drills, with about 66 fuel cell arrays to power it all. As far as I remember, I started out with testing the maximum amount of ore/second a drill would pull out of the asteroid, then added ISRUs to match and measured the total EC rate and finally put in the appropriate number of fuel cells arrays (plus one or two for extra margin). The cooling capacity is a bit on the small side but it did work for hours without any efficiency penalty due to core heat.

Spoiler

Edit: here is the old craft file: https://pastebin.com/NLkh5aDD (the launcher needs the Making History DLC for the tanks and engines)
Version 1.5, how the time flies. Boy, was she a beast to launch. Also not included is the tug required to push it into an asteroid.

Edited by HansAcker
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This is the best guide I've seen on the subject. While it only goes into deep detail on calculations for surface mining, I believe the relevant number to swap is the Base rate of the drill for Asteroid vs Surface.

I think some of the numbers MAY have been re-balanced since that was written, but I cannot confirm.

I'm not sure ore is ever wasted in the on-rails process. I could be underinformed.

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The converters convert a zillion tons of ore to fuel in a second. Therefore, you need half a zillion drills in order to keep up. There's no point to trying. You want one large converter.

You might try to match the output of the drills to the consumption rate of your engines. However, that would assume that you are burning the engines continuously forever. Which you won't be. So that's pointless too.

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Thanks Hans. Looks like .3 is the ratio then (or close enough). I would look at Jr Drills, but they are too short to interact well with a Klaw.

I was planning a modular asteroid tug that would have a seperate mine/refinery as a detachable head. Wanted to saturate a single ISRU in a mass efficient manner. Given I would want any orbital refinery to be solar powered for yield purposes, I don't think I'll worry too much about multiple ISRU miners. Each needs over 3 Gigantors in ec/s at 2x conversion! More still to charge battery reserve for passage through the umbra.

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