ISRU+Drills - Logic, Math & Mechanics

[Violent Jeb]

[redacted, done]

Edited August 16, 2016 by Violent Jeb
Made it look nicer

[KerikBalm]

I like that the small ISRU is less efficient than the big one... but at the moment it uses ore 5x as fast to produce half as much fuel... one needs to mine 10x as much ore to make the same amount of fuel... that seems like a bit much.

"The way it works is that it consumes 5x the ore, but still produces the same amount per second." Check the stats again, it produces half as much per second.

FWIW, I was opposed to having a small ISRU at all, and was happy when the drill mass increased. Essentially, this ISRU makes a craft with a lvl 1 engineer act like an unmanned 2.5m ISRU craft.

I don't think they got the right balance between OP and useless. Its not terrible if you have a good engineer, but I can't timewarp and have my fuel tanks fill up... when I come back the ore tank is full, but no extra fuel is there... seems to be a problem with the fuel production when the craft is not in focus... and its stupid to add lots of ore tankage to it because the ore converts really badly. So then I have to babysit the thing to get it to fill my tanks... not happy with it.

[Violent Jeb]

Well i'm glad i'm not the only one. You're right - i see now that it is producing half as much, while drawing 5x more. That means it is 10% as efficient at most.

I really just don't see why they couldn't just adjust the outputs, or scale the darn thing linearly, why do a bunch of input and output parameters move in opposite directions. It makes no sense that a physically smaller object can process 5-10x more of anything, when the output is less.

It's not only the converting, you can timewarp during the mining process and as long as the craft had electricity when you started timewarp it'll continue to mine until the ore tanks are filled.

I am hoping for some improvements for ISRU tech come 1.1. I'm okay with a smaller unit, just not a smaller unit that has a larger input capacity.. The lighter drills are a good thing. I think there needs to be a better solution for ground based transfer (unless i just cave and use KIS/KAS).

[Geschosskopf]

Time is only of the essence for Kerbals when it invovles 1 or more of 3 things:

1. Transfer windows
2. Having many ships going hither and yon which you can only keep track of using Kerbal Alarm Clock
3. Using a life support mod

If none of these apply to you, then you have only to consider you own investment of your personal time.

[Reactordrone]

9 hours ago, Violent Jeb said:

However, The Small ISRU is logically FLAWED, and here's why. Let's say I can't fit 16 drills and an ISRU. The smaller ISRU is 1/5 as efficient as the large. Logically, you should be able to add 16/5 = ~3 drills, and convert at about 20% of the original rate. Except, this isn't how the small ISRU works at all. Somehow, this little ISRU actually CONSUMES 5X THE ORE!? The way it works is that it consumes 5x the ore, but [edit] only produces half the output.

 

Given that the small ISRU unit dumps 90% of the ore, it makes some sense that it goes through the ore at a faster rate. The Big unit goes slow and gets a 100% conversion efficiency, the small one steams through the ore picking the best material and only converting 10%.

Edited January 5, 2016 by Reactordrone

[Terwin]

By my understanding, the small drill and ISRU are for small probes that will land and replenish their fuel, but are not expected to refuel quickly.

In this scenario the reduced weight is worth the increased time/energy/heat costs of the small drills and ISRU(in fact you probably only have one drill in this scenario to further save on weight)

 

If you want performance, go with the big parts. (or, if you use tweakscale, very big parts... a 200% sized drill is equivalent to 8 drills in 1 part, and a 400% sized drill is virtually identical to 64 drills in 1 part(as an added bonus it even has a longer drill bit reach, letting you have it mounted higher on your ship and still reach the ground))

Also, don't forget your engineers, a novice engineer gives you 5x drilling speed and a 5 star engineer gives you 25x drilling speed.

I have noticed that at a decent drilling site(>=5%) a 3 star engineer(17x) can keep an ISRU busy with less than 7 full-sized drills.

 

[Fearless Son]

It seems logical enough to me that small ISRUs produce less fuel with more ore than the large ISRUs.  I assume that the smaller units have more limited refinement mechanisms, and can only extract minimal amounts of useful elements out of the ore, while the larger units have more complete suites of refinement steps and can squeeze more of the useful stuff out of those rocks.  

As for what use the small ISRU has, I find it actually useful as ballast to balance the weight of a full-sized mining drill.  It weighs exactly as much as a single drill and takes up approximately the same volume.  If what I am looking for is a balanced lander with a single drill, the small ISRU makes an excellent compliment that I can turn to fuel production if necessary.  Mind, I might be better off just finding another way to balance the drill, but that is not always aesthetically reasonable.

[swjr-swis]

Nice to see some hard numbers on the subject, giving some base to the experience that the small ISRU seems rather abysmal at what it does.

The way things are now, the only reason to use it at all is when the regular one surpasses some hard weight or form factor limits for the payload. The downgrade comes at a rather bitter price.

Better than nothing at all, I guess, but it's not an attractive option.

[fourfa]

The small ISRU has a place - for instance, tiny Mk2 spaceplanes that really need its tiny footprint typically don't have much tankage to fill in the first place.

[suicidejunkie]

I've also used the small ISRU in a "KAA Truck" probe rover.

It has one full scale drill, and a probe core, and is driven out to to the west coast or wherever a spaceplane has come down short.  One mk1 fuelselage of LF to get the plane airborne and to the runway for full return value is all it needs, and then it spends the next 50+ days filling back up until there is another spaceplane accident.

[Geschosskopf]

4 hours ago, fourfa said:

The small ISRU has a place - for instance, tiny Mk2 spaceplanes that really need its tiny footprint typically don't have much tankage to fill in the first place.

Pretty much everything in KSP is a trade-off between elapsed gametime on one side and mass/fuel/cost on the other side.  This is true with rockets (you can use a lot less fuel going places with multiple gravity assists but it will take MUCH longer than a bigger rocket just burning the direct route) and it's true with ISRU (big, heavy, expensive parts for fast refuel or small, light, cheap parts for a slow refuel). 

As I mentioned above, elapsed gametime is only of importance in a limited set of circumstances.  If none of those constraints apply to you, and you can find a place with the minimum concentration of ore to run the small drills (IIRC, 2%?), then there's no reason NOT to use the small ISRU and drills to save on overall rocket mass and cost.

Carrying this a step further, unless elapsed gametime matters, there is no reason at all to ever use more than 1 small drill.  Provided you have the minimum ore concentration that the small drill needs, it will eventually fill the tanks just as surely as 10 big drills.  IOW, unless you're under a time constraint, all you get from having multiple drills is a bigger, heavier, more expensive vehicle that needs a bigger, heavier, more expensive rocket to get it to its destination.

For this reason, I"m rather surprised that Squad introduced the small ISRU and drills in 1.0.5.  If you thought the big ones were OP, the small ones are even moreso.  Even with 1 small drill on the most pathetic workable patch of ore, you'll still get your tanks full long before you miss the transfer window back to Kerbin.  And even if you use life support, you still need enough food to wait on that transfer window anyway, so whether you use big or small drills and ISRU makes you no difference.

[Rune]

6 hours ago, Geschosskopf said:

Pretty much everything in KSP is a trade-off between elapsed gametime on one side and mass/fuel/cost on the other side.  This is true with rockets (you can use a lot less fuel going places with multiple gravity assists but it will take MUCH longer than a bigger rocket just burning the direct route) and it's true with ISRU (big, heavy, expensive parts for fast refuel or small, light, cheap parts for a slow refuel). 

As I mentioned above, elapsed gametime is only of importance in a limited set of circumstances.  If none of those constraints apply to you, and you can find a place with the minimum concentration of ore to run the small drills (IIRC, 2%?), then there's no reason NOT to use the small ISRU and drills to save on overall rocket mass and cost.

Carrying this a step further, unless elapsed gametime matters, there is no reason at all to ever use more than 1 small drill.  Provided you have the minimum ore concentration that the small drill needs, it will eventually fill the tanks just as surely as 10 big drills.  IOW, unless you're under a time constraint, all you get from having multiple drills is a bigger, heavier, more expensive vehicle that needs a bigger, heavier, more expensive rocket to get it to its destination.

For this reason, I"m rather surprised that Squad introduced the small ISRU and drills in 1.0.5.  If you thought the big ones were OP, the small ones are even moreso.  Even with 1 small drill on the most pathetic workable patch of ore, you'll still get your tanks full long before you miss the transfer window back to Kerbin.  And even if you use life support, you still need enough food to wait on that transfer window anyway, so whether you use big or small drills and ISRU makes you no difference.

Yup, I also limit my refinery outputs with the number of drills. That way, as long as I can keep electricity rising, the refinery will throttle down and keep on mining off-camera while I do other things. Since I do a lot of other things, the time spent mining is not really that important. Then again, my experience with the small refinery is limited, and with potatoroids things change completely: two big drills will keep a single refinery real busy with no engineer required. But in those situations it's really a matter of throttling the single nuke so I can keep it firing indefinitely anyway so who cares...

So basically, the big ISRU is for orbit, where I want 100% conversion rate, and if it can mine off-camera as I suspect it can (with enough electric production and an engineer, I think it can keep itself running on fuel cells), then surface ops will convert to the small one over time.

 

Rune. My current save has dozens of active flights... and only a handful are outside kerbin's SOI.

[Geschosskopf]

1 hour ago, Rune said:

So basically, the big ISRU is for orbit, where I want 100% conversion rate, and if it can mine off-camera as I suspect it can (with enough electric production and an engineer, I think it can keep itself running on fuel cells), then surface ops will convert to the small one over time.

I keep forgetting about asteroids because I hardly mess with them myself.  When I do mine them, it's just to hollow them out so they're easier to move to the contract orbit, so I WANT waste and inefficiency   But yeah, if you catch them specifically to use as fuel depots, then you don't want to waste any of their finite amount of resources and the big parts would be required.

But ore on planets is infinite, its concentration just affects tank-filling speed, and a few days more or less spent filling tanks almost never matters to anything happening in the KSP universe.  The small parts do work off-camera but even if they didn't, it only takes a few seconds of real time to warp your tanks full with either size of parts.  The small parts are cheaper and lighter, need less power, and cooling, and their inefficiency is meaningless in virtually all gameplay situations.  Asteroids-as-fuel and planets with < 2% ore anywhere useful are the only situations I can think of where you'd have any reason to ever use the big parts instead of the small ones.

[KerikBalm]

I haven't been able to get the small ISRU to work off camera.... I fill up the ore tanks off camera, but thats it.

I have only 1 radial ore tank, because the ore conversion is so low, I want to store fuel with minimal dea mass or ore tanks.... yet that is meaning that I ave to time warp unti 75 ore units are extracte, convert them to 6.75 LF and 8.25 Ox, then time warp again, convert again... and repeat. To fill a FL-T800 tank, this requires over 50 cycles of that... WTF, no thanks...

[suicidejunkie]

Jot down the LF and Ox levels of your miner before leaving the scene quickly with drills running and ISRU chugging.

When you come back, see if they're different.  It might be that the catchup physics top out at one ore tank worth of ISRU conversion, and between the small or tank and inefficient ISRU, you're only getting a tiny amount of fuel converted between physics loads.

[RoverDude]

If you're losing out during catch-up mechanics your likely culprit is insufficient intermediary storage.