The advantages of a mining operation

[Warzouz]

@Geschosskopf, I totally agree with you. I tried the Kerbin LKO refueling tank/station. that was a real waste of time for very little gain. The I begin to look into recoverable SSTO rockets and that was much more profitable, with only 3 minutes of wasted time.

Even if I understand that mid trip refuels are a waste of time, and even of fuel, it's sometime fun to do it.

There are also contracts that push you to do such operations (journeys and those horrible tourists missions (who do them anyway ?) )

[Fisk02]

If you aren´t afraid of waiting years to get a couple of liters of lfo, then it isn´t worth it... I really think that the mining system in ksp are really up.

[Geschosskopf]

3 hours ago, Warzouz said:

@Geschosskopf, I totally agree with you. I tried the Kerbin LKO refueling tank/station. that was a real waste of time for very little gain. The I begin to look into recoverable SSTO rockets and that was much more profitable, with only 3 minutes of wasted time.

Even if I understand that mid trip refuels are a waste of time, and even of fuel, it's sometime fun to do it.

There are also contracts that push you to do such operations (journeys and those horrible tourists missions (who do them anyway ?) )

AFAIK the only contracts that require mining are those that want you to deliver ore from Point A to Point B, or to have X amount of ore in a station or base (which is too much to just tweak into the tank in the VAB and fly there from the ground).  And all of these contracts require you to do very stupid things, leaving you with a set-up that you'll never use again because it's so horribly inefficient.  For instance, haul ore from Eve to Gilly.  Seriously?!?!?  Or build up a stockpile of ore in a base or, especially, a station, especially in a location (like Mun, Minmus, or Kerbin) where you should never bother with a refueling system anyway.  None of them want you to do anything that's actually of long-term use to you.  As a result, I've never accepted any of these contracts.

[WuphonsReach]

Refueling in LKO (low Kerbin orbit) is generally not worth it.  Put your refueling stations up around 2500-3000km altitude around Kerbin (Kerbin synchronous orbit works well), or even out by the edge of Kerbin's SOI.  This has a bunch of advantages:

• More fuel in the tanks when you slip free of Kerbin's gravity well.
• More accurate ejection burns (easier to start/stop at right time without changing ejection angle much).

I always boost my inter-planetary launches up to at least 500-1000km or more before doing the ejection burn.  Yes, you waste a bit of fuel circularizing at the higher altitude, but it makes everything easier.

[Geschosskopf]

15 hours ago, WuphonsReach said:

Refueling in LKO (low Kerbin orbit) is generally not worth it.  Put your refueling stations up around 2500-3000km altitude around Kerbin (Kerbin synchronous orbit works well), or even out by the edge of Kerbin's SOI.  This has a bunch of advantages:

• More fuel in the tanks when you slip free of Kerbin's gravity well.
• More accurate ejection burns (easier to start/stop at right time without changing ejection angle much).

I always boost my inter-planetary launches up to at least 500-1000km or more before doing the ejection burn.  Yes, you waste a bit of fuel circularizing at the higher altitude, but it makes everything easier.

Actually, this is very inefficient.  For starters, the further away from Kerbin you do your burn, the less Oberth effect you have, so the more fuel you need to generate a given amount of dV.  Second, Kerbin's escape velocity is constant but when you're orbiting out near Minmus, you're starting velocity is much lower than it is when close to Kerbin (a few hundred at most compared to over 2000)..  Therefore, you need more dV just to escape Kerbin, plus whatever you need in addition to reach your target.  So that's more dV required, and more fuel used to create every single m/s, so you end up burning way more fuel for the same burn than if you started in LKO.  And on top of that, the further out you are, the more time it takes to make an orbit, on the order of weeks instead of 20 minutes or so in LKO.  This means you'll almost certainly miss the ideal transfer window by at least a few days, making the burn itselt (no matter where you do it from) cost more dV than it should.  I've tested this just recently and found all this to be true.  A transfer from Kerbin in the same window to Niedon costs about 2700m/s from LKO and about 3500m/s from about 1/2way out to just Mun, for example, and that 3500m/s requires more fuel per m/s than the 2700m/s in LKO.

There are some folks who refuel at Minmus then dive down to a low Kerbin Pe to do their transfer burns, with the benefit of having higher starting velocity and more Oberth than being in LKO.  But OTOH you usually have to wait a couple weeks off the ideal transfer window for Minmus to line up opposite your ejection angle so you can make the dive, which means the dV cost is more than the minimum, which means this is usually results in little or no fuel savings at the cost of greatly increased complexity.

[Clear Air Turbulence]

So a mining operation on minmus supplying a refuelling station in sub-munar orbit?   I guess you then also have the option of a gravity assist every now and then...

[Warzouz]

1 hour ago, Clear Air Turbulence said:

So a mining operation on minmus supplying a refuelling station in sub-munar orbit?   I guess you then also have the option of a gravity assist every now and then...

It doesn't change much. It's not worth it. Still, you can do it for fun (that's way we all play KSP

[juanml82]

It depends a lot on play-styles. Do you just want to plant the flag? Not worth it.

Do you want to do biome hoping and survey contracts? That's useful.

Are you designing huge motherships? Useful: send them to orbit with dry tanks by using smaller boosters with less lag, refuel in LKO and go to destination

Do you want to reuse interplanetary tugs? Take your payloads to wherever you're sending them, return the tug (and maybe kerbonauts) to Kerbin, refuel the tug in orbit and the next time you want to send something to another planet, you just need to lift the payload to LKO instead of lifting a new tug as well.

Edited December 4, 2015 by juanml82