how to excute infinitly tedious maneuver node?

[omelaw]

I sent a small astroid tug to an asteroid ( a lv-n, IRSU, two drills) and met a 3000t E-class one

and aerobrakeing node is 180m/s, and appearently I only have 1cm/s^2 accerration(due to not enough fuel process rate)  then burn time is.... 180/0.01=18000s=5hour!

should I send another bigger tug for it?

[Tex_NL]

How much fuel storage have you got? Try filling your tanks as much as possible in advance.

[Evanitis]

You can try mining it for a lower mass too... But... 1 nuke for 3000t? *shivers*

I used 6 on this ~2000t one, and it still felt insanely long to do burns. Hell, it's still long now that it's stripped down to ~150t. I felt I shouldn't have used nukes in the first place - why conserve dV when you have hundreds of tonnes of ore? If I wanted another class-e today, I'd probably bring lot more powerful engines.

Edited February 11, 2016 by Evanitis

[Snark]

You have a very low-thrust engine and a very high-mass payload. Ridiculously long burn times are unavoidable.

You can speed up your wait time up to 4x by using physics warp, but yeah, it's going to be a very long wait, there's just no way around that.

So either you just resign yourself to waiting it out, or else you send something with a lot more thrust. There's nothing else.

 

Edited February 11, 2016 by Snark

[Streetwind]

58 minutes ago, omelaw said:

and aerobrakeing node is 180m/s, and appearently I only have 1cm/s^2 accerration (due to not enough fuel process rate)  then burn time is.... 180/0.01=18000s=5hour!

Isn't there some sort of bug with ISRU running while the engines are on? Or am I misremembering things?

[AlphaMensae]

Shades of that floppy monstrosity Scott Manley built in Interstellar Quest...burned for hours and hours because it couldn't handle more than 10% thrust..

Yup, this isn't Real Life, so unless you're unable to due to your situation in Career Mode or something, send a more powerful tug.

[radonek]

Physical warp will sure cut it down a bit if your HW can handle it. But make a savegame and be very careful - klaw and physwarp are both strong krakenbait. Or just bring a mainsail…

[Snark]

1 hour ago, omelaw said:

I only have 1cm/s^2 accerration(due to not enough fuel process rate)  then burn time is.... 180/0.01=18000s=5hour!

Ah.  I'd managed somehow not to notice the above-- in your original post, I just saw "3000t asteroid" and "single LV-N" and "long burn time" and my brain basically stopped processing further input right there.    Thanks to @Streetwind for pointing this out.

Doing the actual math:  a single LV-N with 60 kN thrust, pushing a 3000t asteroid, ought to get a whopping 2 cm/s² of acceleration, twice what you're experiencing.  So if you can deal with the fuel bottleneck, you can cut the burn time in half.  Still really long, but 2.5 hours is a whole lot shorter than 5 hours!

If your actual bottleneck is fuel processing speed, then you can save (some) on your time, though not on KSP in-game time.

1. Turn off your engine
2. Let the drills + ISRU run until your fuel tanks are full.  The nice part here is that you can use high-rate timewarp to zip ahead, so you're not wasting a bunch of your time.
3. Drop out of timewarp, throttle your engine to the max, burn until the tanks are empty.  (Use 4x physics warp during this phase.)
4. Repeat steps 1-3 as necessary.

It won't save any in-game time, because the fundamental limitation is still going to be the rate at which you can extract fuel.  If you can supply your ship with a higher-level engineer, that would boost the fuel extraction rate, which would save some in-game time but not really any of your time.

If you can do the above, and do 4x physics warp during the engine burns, that makes only a bit more than half an hour of your time to do the burn.  Still not great, but whether it's "good enough" depends on how patient you are.  Would sending a back-up ship with more engine power take longer than half an hour of your time?

30 minutes ago, Streetwind said:

Isn't there some sort of bug with ISRU running while the engines are on? Or am I misremembering things?

Yes, there is, but it isn't what's biting the OP here, I believe.

The ISRU bug happens when you have multiple engines running at the same time that ISRU is going on, and it happens even when you have plenty of fuel in your fuel tanks.  It expresses itself by making one of the engines (or was it "all but one"? I forget) run at significantly reduced thrust as long as ISRU is running.

But it doesn't happen when you only have a single engine (I believe), and in any case, if the OP is bottlenecking on fuel supply, there's really no way around that problem-- not enough fuel means not enough fuel, the engine is simply starving, that's all there is to it.

[Streetwind]

Ah right, that's how it went. Thanks for refreshing my memory

[Padishar]

46 minutes ago, Snark said:

But it doesn't happen when you only have a single engine (I believe),

It did happen with only a single engine (bug 5132) but it was supposedly fixed in 1.0.5 so shouldn't be happening anymore.  In any case, the bug only happened when you had multiple tanks with at least one empty and you could easily see when this was happening as the thrust readout on one or more of the engines would be very low despite still having plenty of fuel to run at full thrust (the engine would only use the small amount of fuel the ISRU put in the empty tank each frame and wouldn't touch the still full tank).

As you point out, a single nuke pushing 3000t only gets 0.02 m/s^2 anyway and that is going to be painful.  Using larger engines wont really help by itself as they will use fuel faster.  If you are resigned to running engines directly from ISRU output then you will need more output to get more thrust.  Just using a bigger engine will actually hurt your acceleration as, for the same fuel flow rate, the nuke has the highest thrust because of its high Isp (F = (mass flow rate) * Isp * g).  Your only reasonable solution is to either take lots of fuel with you or take a large empty tank that you can fill at high timewarp.

This is a bit old now (from back when nukes used LF+O) but my class E tug used 18 nukes:

Even that was a bit sluggish so I made an alternative with 6 mainsails:

Nowhere near as much deltaV as the first one but nearly 9x the thrust...

[Snark]

18 minutes ago, Padishar said:

It did happen with only a single engine (bug 5132) but it was supposedly fixed in 1.0.5 so shouldn't be happening anymore.

Dunno about the single-engine case, but it's definitely still happening with multi-engine in 1.0.5, I've run into it myself.  Had a mining/ISRU ship with two LV-N's on it.  Taking off from the surface with all tanks full (fuel & ore), set to full throttle.  If the ISRU was running, then one of the two LV-N's was running at only a small fraction of full power.  (As evidenced by the thrust readout in the right-click menu, and the smaller/dimmer exhaust flame from the engine, and the ship's desire to torque a bit due to uneven thrust).  It only affected one engine, the other was fine.  Turning off the ISRU conversion fixed the problem.

In any case, this is getting a bit off-topic, since this is clearly not the OP's problem-- not only is he just running a single engine, but also he's fuel-limited by what the drills can mine, rather than an engine-thrust bug.

[kurja]

Script kOS to do the burn for you and go do something else for the duration.

Hm doesn't mechjeb have an "execute node" function too?

[Tex_NL]

6 hours ago, kurja said:

Script kOS to do the burn for you and go do something else for the duration.

Hm doesn't mechjeb have an "execute node" function too?

I most certainly does. But using MechJeb to execute the node does nothing to shorten the burn. All it will do is take some work out of your hands.

[Evanitis]

6 minutes ago, Tex_NL said:

All it will do is take some work out of your hands.

Indeed... but if I decided to do an AFK burn of 2-4 hours, I'd most definately pick MJ's SmartASS over the stock SAS to hold the heading. I had bad experiences with the former in the past.