ISRU producing very little conversion

[Hotel26]

I have empty fuel tanks, 1,500 units of ore in a tank. 4x Gigantor solar panels extended, and 4 of the small, passive radiators.  I noticed that the radiators did not pick up a glow.  (And I should mention that they were on a docked lander whereas the ISRU was on the rover docked to the lander.  Nevertheless, the ISRU status said temp OK, 100% efficiiency.)

Small ISRU runs quickly and at 100% efficiency at optimal temperature.  I see that I *am* getting fuel converted but from 1,500 units of ore I only got about 20 units of fuel.

There was a Kerbonaut sitting on a chair on the rover but I understand the presence or not of a Kerbonaut does not effect ISRU performance.

This is KSP 1.0.5.  So what gives?  I expected to get 3,000 units of fuel from that 1,500 units of ore...

Thanks for any assistance and enjoy your Holidays!

[Snark]

You're using the small ISRU, yes?  (the new one that was added in 1.0.5)

The large ISRU is non-lossy; that is, 1 ton of ore will always produce 1 ton of fuel.  It runs faster if you have a high-level engineer present, but the efficiency is always 100%.

I haven't had occasion to use the new small ISRU myself since it was added in 1.0.5, but I seem to recall hearing that unlike the big ISRU, it is lossy (i.e. one ton of ore produces less than a ton of fuel).  Don't know anything about the details, though.

Is this the first time you've used the small ISRU?  (i.e. is this a case of "I just tried using it for the first time and it wasn't what I expect", or is it a case of "it usually works, but not this time and I don't know why"?)

[FancyMouse]

I heard even for old big ISRU, mono mode is lossy as well. Haven't checked myself, though.

[fourfa]

Small ISRU turns 10 tons of ore into 1 ton of fuel.

Large ISRU turns 1500 ore into 3000 liquid fuel OR oxidizer, or 1350/1650 of liquidfuel/oxidizer, or 3000 monoprop.  Divide all those numbers by 10 for small ISRU.

Presence or absence of Kerbals doesn't change ISRU output, only drills (and only specifically engineers, not pilots or scientists).

Only about 20 units of fuel mean there must be a problem somewhere else.  Power, storage, docking state between tanks and ISRU, don't know.

[KerikBalm]

17 hours ago, FancyMouse said:

I heard even for old big ISRU, mono mode is lossy as well. Haven't checked myself, though.

1 unit of ore = 2 units of Mono/LF/OX

1 unit of LF or OX have precisely 1/2 the mass of 1 unit of ore. That is 1 unit of ore masses 0.01 tons, whereas 1 unit of LF or OX masses 0.005 tons. In contrast, 1 unit of monoprop masses 0.004 tons. Thus 1 unit of ore, massing 0.01 tons converts to 2 units of monoprop with a combined mass of 0.008 tons... 20% mass loss

[Hotel26]

@Snark Yes, first time using any kind of ISRU.  It's the small ISRU.

@fourfa Interesting.  The small ISRU is only 10% as efficient as the large ISRU??  woah.  Redesign.  I'll put the large ISRU on the rover on the surface.  Although truth be told, I am now producing so much ore that it doesn't matter much except for pride.  I'll run a test but it's credible that I am getting 150 units total of fuel from that 1500.  Or should it be 300?  Hmmm.

I can also send some ore space-side and use a big ISRU up there to see what yield I get.

I'll experiment and report back here.  Thanks for the help, gentlemen.

[Hotel26]

On 25/12/2015 at 11:40 AM, fourfa said:

Small ISRU turns 10 tons of ore into 1 ton of fuel.

Large ISRU turns 1500 ore into 3000 liquid fuel OR oxidizer, or 1350/1650 of liquidfuel/oxidizer, or 3000 monoprop.  Divide all those numbers by 10 for small ISRU.

Presence or absence of Kerbals doesn't change ISRU output, only drills (and only specifically engineers, not pilots or scientists).

Only about 20 units of fuel mean there must be a problem somewhere else.  Power, storage, docking state between tanks and ISRU, don't know.

You're right.  The Wiki says:

"The conversion rate of this module is far less efficient than the bigger Convert-O-Tron 250's. "

(I should have read the fine print!)

I just converted 478 units of ore to receive 86.51 fuel and 106 oxidizer which is a fuel:oxidizer ratio of 1:1.23 and a yield of 20%, rather than 200%, so fourfa's 10-fold divisor is accurate.

Thanks very much all!  It's a relief to know what is going on.

The ISRU is not strictly necessary on the ground.  I thought I could use a smaller fuel budget on the lander but it's cheaper to produce all the fuel in space (OR take a large ISRU to the ground...  which would mean a third type of flight system).