Is orbital body ore farming viable?

[jwbrase]

On Thursday December 31, 2015 at 5:00 AM, Foxster said:

I haven't yet found a use for mining and converting to fuel on any kind of regular basis. You can make any kind of practical mission in the system with one launch from Kerbin.

But for sending a given vehicle to orbit, you can put it on a smaller launch vehicle that's easier to build and fly if you launch the payload empty and fuel it on-orbit.
 

[Rune]

3 hours ago, KerikBalm said:

Except since SSTO landers without ISRU are possibe on Tylo... If you can start in orbit andland on tylo with all the fuel needed to get bck to orbit, then you can start on the surface of tylo (fueled by an ISRU) and get to orbit with all the fuel needed to land again. The margins are pretty small though making it a tedious undertaking to stockpile large amounts of fuel by ISRU on Tylo. It can be done though.

In order to do Tylo, you would have to get some payload in a >7km/s rocket... and you get to carry the payload on the first 3.5km/s, not the latter (you have to refuel on Tylo, else you have to take to orbit more fuel than it takes to land). Perhaps a high >1 TWR ship can be built like that... but no, thank you. Bop and Pol are there for a reason.

3 hours ago, Alshain said:

Depends on your definition of 'easier'. I would rather make 20 trips back and forth from the surface than perform one surface docking.

There are land dockings, and then there are land dockings:

After dropping one of those mobile surface refineries one a low-grav moon, the LackLuster can get back up and grab a 15mT ore tank: miner and tanker without sacrificing anything.

 

Rune. I'm probably too proud of this, since it is basically Mars Direct's surface refinery.

Edited January 4, 2016 by Rune

[Alshain]

@Rune The problem with that is it uses the claw.  I prefer to have my universe in tact, so I pretend that part doesn't exist.  There is no real good way to dock on the surface of a planet in stock.

[Foxster]

1 hour ago, jwbrase said:

But for sending a given vehicle to orbit, you can put it on a smaller launch vehicle that's easier to build and fly if you launch the payload empty and fuel it on-orbit.
 

Maybe...but there is a fairly high cost getting the refuelling in place. I suspect it might take a lot of launches to get your money back. 

[KerikBalm]

24 minutes ago, Rune said:

In order to do Tylo, you would have to get some payload in a >7km/s rocket... and you get to carry the payload on the first 3.5km/s, not the latter (you have to refuel on Tylo, else you have to take to orbit more fuel than it takes to land). Perhaps a high >1 TWR ship can be built like that... but no, thank you. Bop and Pol are there for a reason.

I've found that 4,900 m/s is sufficient dV to land on Tylo and get back to orbit... which is quite different from 7 km/s.

Its actually easier to do the surface -> orbit-> surface again than to do orbit->surface-> orbit again.

Either you deorbit+ land "heavy" and ascend "light", or you deorbit "light" then take on payload and ascend "heavy". Either way you have maneuvers with a dV of more than orbital velocity in a "heavy" and a "light" configuration. However, taking fuel on at the surface means that you do the landing in the "light" configuration. The landing takes more dV than the takeoff+ orbit because of the need to set the craft down gently and the resulting losses to gravity drag... so the fuel mass you waste to dV is less when you're trying to get fuel to orbit vs trying to land with fuel for the ascent. Also the TWR is better in that case, which should result in less total dV loss.

As I figure it, I had a design with roughly 5.5 km/s, I got to orbit with 614 m/s left, it was 154 tons to start with, the engine Isp was 340.

4900= 340*9.81 ln(154/m_0) .... so the ship would be ~34.5 tons in orbit, with 614 m/s left. The fuel for that 614 would amount to the payload.

614 = 340*9.81 ln(34.5/m_0)  so the empty mass would be ~28.7 tons... 34.5-28.7 = 5.8 tons of fuel payload to orbit.... with a tanker that has a wet mass of 154 tons... 3.77% payloa raction. I cou improve it a bit by removing the lander cans and the science packages I had on it... but that won't change a whole lot... maybe another ton of payload to orbit... Call it 6.8 tons of fuel per trip. An orange tank holds 32 tons of fuel. Thus I woud need 5 trips own to the surface of tylo, refining over 100 tons of fuel each time, just to fill up an orange tank.

Nah... I'm sticking to my plan of using Val as my fuel source for my Jool operations (and some limited ISRU on laythe, but that is to support surface and atmosperic exploration, not to supply orbital fuel depots... altough its designed so that it could do that as well).

My point is simply that it is possible... just not practical.

[Aethon]

58 minutes ago, Alshain said:

@Rune The problem with that is it uses the claw.  I prefer to have my universe in tact, so I pretend that part doesn't exist.  There is no real good way to dock on the surface of a planet in stock.

 

 

I have no problem docking these two on the surface.  The ISRU has engines on the front and back so it roves to the ore and roves back to the fuel tanker.  When the Sr. port is under it's mate, I raise the legs on the tanker and give it a little WASD wiggle and it docks right up.

Edited January 3, 2016 by Aethon

[Rune]

 

35 minutes ago, KerikBalm said:

I've found that 4,900 m/s is sufficient dV to land on Tylo and get back to orbit... which is quite different from 7 km/s.

Its actually easier to do the surface -> orbit-> surface again than to do orbit->surface-> orbit again.

Either you deorbit+ land "heavy" and ascend "light", or you deorbit "light" then take on payload and ascend "heavy". Either way you have maneuvers with a dV of more than orbital velocity in a "heavy" and a "light" configuration. However, taking fuel on at the surface means that you do the landing in the "light" configuration. The landing takes more dV than the takeoff+ orbit because of the need to set the craft down gently and the resulting losses to gravity drag... so the fuel mass you waste to dV is less when you're trying to get fuel to orbit vs trying to land with fuel for the ascent. Also the TWR is better in that case, which should result in less total dV loss.

As I figure it, I had a design with roughly 5.5 km/s, I got to orbit with 614 m/s left, it was 154 tons to start with, the engine Isp was 340.

4900= 340*9.81 ln(154/m_0) .... so the ship would be ~34.5 tons in orbit, with 614 m/s left. The fuel for that 614 would amount to the payload.

614 = 340*9.81 ln(34.5/m_0)  so the empty mass would be ~28.7 tons... 34.5-28.7 = 5.8 tons of fuel payload to orbit.... with a tanker that has a wet mass of 154 tons... 3.77% payloa raction. I cou improve it a bit by removing the lander cans and the science packages I had on it... but that won't change a whole lot... maybe another ton of payload to orbit... Call it 6.8 tons of fuel per trip. An orange tank holds 32 tons of fuel. Thus I woud need 5 trips own to the surface of tylo, refining over 100 tons of fuel each time, just to fill up an orange tank.

Nah... I'm sticking to my plan of using Val as my fuel source for my Jool operations (and some limited ISRU on laythe, but that is to support surface and atmosperic exploration, not to supply orbital fuel depots... altough its designed so that it could do that as well).

My point is simply that it is possible... just not practical.

Right, surface->orbit->surface and refuel is much easier to fly because you only fly the full ship on the ascent path, where it is easy to hit a nice gravity turn and lose as little to gravity drag as you have to. Besides, you can leave the refining kit on the ground and still land close by with a very high TWR to nail things cheaply. The thing is, you have to have a refining kit on the ground, else you need to take up, as payload, enough fuel to land and take off again with the full ore payload...in your case, the 156mT, which you can clearly see is ridiculous. With a refinery on the ground, you only need to take up enough fuel to land empty, the rest is profit. And on Tylo, though doable in theory, it would be a pain in the ass to do in real life, especially the precision landings. We are in perfect agreement then, since that is what I was saying!

1 hour ago, Alshain said:

@Rune The problem with that is it uses the claw.  I prefer to have my universe in tact, so I pretend that part doesn't exist.  There is no real good way to dock on the surface of a planet in stock.

These days, it is much more stable than it used to. As long as you don't clip it (like the circular cargo bays, leave them a wide berth), and you stick to one clawed vessel at a time (no klawing klawed vessels, or docking klawed vessels, or doing anything with klawed vessels except de-klawing them when you are done refueling), they won't give you any trouble. Which basically means that they are perfect to dock a refinery with a vessel and do surface ISRU.

 

Rune. In any case, my save-fu is strong these days.

Edited January 4, 2016 by Rune

[KerikBalm]

6 minutes ago, Rune said:

The thing is, you have to have a refining kit on the ground, else you need to take up, as payload, enough fuel to land and take off again with the full ore payload...in your case, the 156mT, which you can clearly see is ridiculous. With a refinery on the ground, you only need to take up enough fuel to land empty, the rest is profit. And on Tylo, though doable in theory, it would be a pain in the ass to do in real life, especially the precision landings.

Yes, one needs to have a mining installation with a fuel truck already on the surace, and land within a reasonable driving distance to it.

Otherwise, of those 6.8 tons of payload (assuming my science stuff and crew cabin amounted to 1 ton)... -4.25 tons for the ISRU-> 2.55 tons

2x large drills (to balance it out, and because its a big craft and you certainly dont want to fill it with small ones... assuming you want more than one fuel delivery per year) -3 tons (1.5 each)..... uhhh... yea, we just went over the mass budget, and haven't even added back the crew cabin (for the engineer drill bonus, needed if the output will be high enough to run the whole thing off of fuel cell power), or enough power generation to run the drills and ISRU...

Double the craft size, double the payload.... so... 13.6 tons -4.25 for ISRU, -3 for drills, -0.6 for lander can, -2 for power systems (guessing here)... 3.75 tons of fuel to orbit from a ~300 metric ton craft... hey! better than 1% payload fraction! W00t! .... yea... if you're going to do it, leave the refinery on the ground... but mining on Val is so much more practical, and the transfers are much shorter (bop has serious inclination issues and long transfer times... pol is really far out there and the capture burn is higher even if getting to pol orbit is easy... val to tylo or val to laythe transfers are quite short and cheap.

Unlike Eve, its not strictly impossibe, its just incredibly impractical.

[Temstar]

18 minutes ago, KerikBalm said:

Otherwise, of those 6.8 tons of payload (assuming my science stuff and crew cabin amounted to 1 ton)... -4.25 tons for the ISRU-> 2.55 tons

That seems like a lot for Tylo SSTO. Imagine this setup:

1. You have some kind of orbital facility in Tylo orbit, either a space station or a ship for going to other places in Jool system.
2. You have some ISRU setup on the ground on Tylo, a rover of some sort with at least one seat for an engineer

So the SSTO is sorely for moving people between orbit and the ground repeatedly, and thanks to the ISRU rover on the ground it can be refueled on the ground.

If that's the case you can have an incredibly small SSTO using command seats. Tylo doesn't have an atmosphere so there's no issue with "open air" landers. And for life support RP players since your kerbals will have access to proper capsules on the ground (via the ISRU rover) and in orbit (via space station / spacecraft) their EVA suits only need to support them for at most several hours between launch back into orbit and docking with the orbiting craft. Even real life human EVA suits can handle that kind of time.
 

Edited January 4, 2016 by Temstar

[AbacusWizard]

I've gotten reasonably good at surface docking, at least on Minmus, where the gravity is weak enough to make things a little easier.

At first I tried placing upwards-facing large docking ports on the ground (attached by girders) to act as landing pads. Difficult, but it worked, although one bad landing sheared off a third of the solar array.

Later I set up a tanker on wheels that could land near the surface refinery and cautiously roll towards the wall-mounted medium docking port. Worked very well.

Recently I've been experimenting with a hybrid approach: a refinery with landing pads as before, but a wheeled tanker that lands nearby, rolls along so that its underslung docking port is directly above the landing pad, and retracts its wheels to settle onto the dock.

[KerikBalm]

8 hours ago, Temstar said:

That seems like a lot for Tylo SSTO. Imagine this setup:

1. You have some kind of orbital facility in Tylo orbit, either a space station or a ship for going to other places in Jool system.
2. You have some ISRU setup on the ground on Tylo, a rover of some sort with at least one seat for an engineer

So the SSTO is sorely for moving people between orbit and the ground repeatedly, and thanks to the ISRU rover on the ground it can be refueled on the ground.

Yes, It is a lot, my initial proposal had no such thing. What I said there was in response to Rune saying you'd need to land next to an ISRU operation on the surface of Tylo.

To quote more of what I said:

"Yes, one needs to have a mining installation with a fuel truck already on the surace, and land within a reasonable driving distance to it. Otherwise, of those 6.8 tons of payload ..."

This was the "otherwise" case... where the ship has to be massive to be able to haul the ISRU equipment and still have any payload capacity at all.

If all you want to do is move kerbals back and forth rom the surface, well then thats another thread, but that is easily doable. 6.8 tons of payload is a lot of kerbals.

http://wiki.kerbalspaceprogram.com/wiki/Mk3_Passenger_Module

Actually, it would be more than 6.8 tons... My ship had 630 m/s left over, not 614 (I seem to have conflated that number with the 415 m/s eft over on my aerospike design), and was carrying 2 lander cans+ science and electrical equipment. The 2 lander cans alone are 1.2 tons... 1.2+5.8-> 7... The science and un-neccessary electrical stuff probably increases that to 7.5 tons of payload (which still means that it can't handle a 2.5m ISRU+2x large drills+1 crew capacity+electrical)...

Btw... do you get the drill speed bonus for using a command seat? or do they have to be in a pod? I think the game treats kerbals in external command seats a bit differently. The drill bonus of an engineer would be needed to make something like that work at tylo where solar produces 1/25th the normal power, RTGs aren't really viable for the high power demands of ISRU either... so fuel cells are really what you'd want - but they consume fuel to produce fuel, and you need a net positive... so the drill bonus of kerbal engineers really helps with that (A lvl 5 engineer will make a drill produce 25x more ore for the same electric charge consumption)

[Terwin]

15 hours ago, Rune said:

These days, it is much more stable than it used to. As long as you don't clip it (like the circular cargo bays, leave them a wide berth), and you stick to one clawed vessel at a time (no klawing klawed vessels, or docking klawed vessels, or doing anything with klawed vessels except de-klawing them when you are done refueling), they won't give you any trouble. Which basically means that they are perfect to dock a refinery with a vessel and do surface ISRU.

I do not generally have problems with my Klaws any more.

I generally mount a klaw on the nose of my training/tourist vessels in case I get a rescue+pod mission.

I then recover the rescuees/trainees/tourists with another klaw mounting rescue vessel, klawing the recovered pod when present(it is then a single piece grabbed by a klaw on each side).

I don't know how much of this is due to the stock bug-fix mod however.

 

More on-topic I generally just have a nuke-powered craft with ISRU for wherever I intend to go.  (in previous games I landed and returned from everywhere except Lathe, Tylo, and Eve using this approach)

I am not a big fan of docking, orbital or landed, so my first multi-part(as opposed to multi-stage) craft is actually heading to Jool in my current game.  Even there, I can land the entire thing on Vall/pol/bop for refueling and only separate the  lander for Lathe and Tylo.  (The original plan was to use the lander everywhere, but I verified my fully loaded TWR was high enough to lake off from Vall when I did a test landing on Minmus, so now I am planning to land my transit/science/Life Support/Habitat component(4x nerv)  with the lander(2.25xMamoth with science and ISRU) on the smaller moons)

 

Unfortunately I chose a bad time to depart, so my Jool ship is still more than a year from Jool, I might even need to replenish some of the USI-LS supplies before I head back to Kerbin if that will also be a multi-year transit. (~ 30 seats for 5 kerbals, so at least they are not crowded)

Of course I also refine a lot of the fuel in orbit, as I use the ore tanks as back-up fuel tanks, but that is only after I fill all my fuel tanks on the surface.