What's the purpose of ISRU?

[davidy12]

Title says it all. I just don't understand how ISRU is important for KSP. Can someone please explain it to me. I have done refueling operations with KAS, but other than that I don't see the significance.

[Red Iron Crown]

It is free fuel, and fuel that is available somewhere more convenient than on the surface of Kerbin.

[Slam_Jones]

Allows for (as you said) refueling operations and such. It can help extend the range of a vessel significantly, (or indefinitely) if done correctly.

It also provides a framework for conversion of other materials. For example, if you have the extraplanetary launchpads mod, you can modify your ISRU so it can convert Ore directly into Rocket Parts. This allows you to build new vessels on-site.

[davidy12]

Well... just curious, how do you transfer fuel more efficiently rather than docking?

[Slam_Jones]

Either build a single vessel with all the on-board equipment, or deploy little "gas stations" that would dig up and produce fuel on their own.

Here's an example station I built:

Typically, I'll bring in a nuke-powered lander, fill up, then take the fuel to an orbiting station.

As far as efficiency goes, I'm not completely sure the "best" way to go.

[Alshain]

It's not "free" fuel. I mean it costs quite a bit to set up the infrastructure. The idea is to fuel your ships from other places where you don't have to carry it with you. However to stock KSP, ISRU is irrelevant. It's not that hard to go anywhere in the solar system and back again just carrying fuel, and for the most part, hauling the infrastructure is just as bad as hauling fuel.

ISRU doesn't really become useful till you start using mods to colonize, add more planets, and do the other things. So why is it in stock then? Well, there are some questions I don't have an answer for and I'm not sure there is an answer for it. Suffice to say, it is pretty much a stock feature who's purpose is supporting mods.

[peachoftree]

to utilise resources in situation!

[wossname]

Well... just curious, how do you transfer fuel more efficiently rather than docking?

Suck it out of the ground.

[FlyingPete]

Things like a long term mission to Jool and its moons is where the ISRU equipment would come into its own. There is a balance to be struck somewhere in that you have weigh up (quite literally) the ISRU, mining landers etc against carrying more fuel from Kerbin. For short-term 'flags and footprints' type missions, it's not really worth it. Set up a base on Duna though, and you have a source of fuel on site to power exploratory missions, making the base self-sufficient in the long term.

I've sent a long-duration mission on its way to colonise space itself- there's a large ship that will rendezvous with asteroids and mine them for fuel. No long-term destinations, though depending on what trajectories it ends up following, it might end up at Dres or Duna/Ike for a while.

[Terwin]

I like ISRU because it allows me to do things like Biome hopping on Joolian moons and to bring along an asteroid as a droppable fuel pod without needing to send out such pods from Kerbin.

My rockets are probably not terribly efficient, and I can still do things like visit every solid body outside of Kerbin's orbit(not 100% sure about Lathe and Tylo, but I hope to verify it for Tylo tonight).

I can also 'just go' and not need to worry about having enough fuel for the entire itinerary, so long as I can manage my longest expected leg.

[mikegarrison]

This just funny.

I just don't understand how ISRU is important for KSP.... I have done refueling operations ... but other than that I don't see the significance.

The part is designed to allow refueling operations. So why are you looking for any significance other then that? Might as well ask what the significance of fuel tanks are, other than for carrying fuel.

[RocketBlam]

Really, it's because 1000 units of fuel in Jool orbit is a heck of a lot more expensive if you ship it from Kerbin, than if you produce it at Vall. I don't know how the costs break down, but the ISRU pays for itself pretty quickly.

[Mastikator]

Really, it's because 1000 units of fuel in Jool orbit is a heck of a lot more expensive if you ship it from Kerbin, than if you produce it at Vall. I don't know how the costs break down, but the ISRU pays for itself pretty quickly.

Hell you could get a ton of mileage just by doing a quick stop at Minimus before you go off on your hoffman transfer. It takes like ~170m/s delta-v to go from minimus surface to a highly eccentric orbit that can be taken advantage of.

[xebx]

An ISRU setup pays back very very quickly for a large ship / large tanker :

1 ISRU mass : 4.25t, 2 Drillers : 1.5t, 2 gigantor + 2 fuelcells array : 1t, 1 small Ore tank : 0.5t, total is around 7.25t.

This is less than 1 small Rockomax X200-16 tank (9t, 8t fuel)...

During my Eve mission, it took only 30-33 days to refuel 7 Kerbodyne S3-14400 tanks (stock largest tanks) on the surface : Fuel Mass (with tank) = 7x81t = 567t

Edited October 6, 2015 by xebx

[helaeon]

It lets you do a Duna mission one of the proposed Mars mission ways as well: where you send a little ISRU base first get it digging up and making fuel. Then you only need to send the manned lander. You can expend all the fuel in the lander if you need on landing, then use Duna's resources to fill up the lander to go back to Kerbin. Now that your base is already there though you could send as many landers as you like and keep fueling them up. If you wanted to do science on a planetary scale you'd have a fuel depot in orbit and a fuel hauling drone that could make orbit with lots of excess fuel and keep that depot topped off. You'd do ferry missions as needed. Then you'd send a lander designed to dock with that depot, land, return to orbit, top off and go home.

ISRU opens up a ton of mission profile options even in stock.

[Mister Dilsby]

Right now I'm making extensive use if ISRU for an Eve mission. Here's my armada in Gilly orbit:

The reason all the ships are different and many do not appear to be entirely suited for the mission at hand... is reasons. The Eve lander will be the pointy thing in the middle. It used almost all of its fuel to SSTO from Kerbin and was towed to this point by the one that looks like a frilled lizard, at lower left. That ship, and the little one on the far right, are both ore miners that shuttle back and forth to Gilly. We turn the mine into ore with a few of the other ships, which will fill up the lander before it enters Eve atmosphere.

Anyway, we're not done yet with ISRU. That lander is going to need to burn a lot of fuel to survive its descent, and it will need even more to get back to orbit. There is a rover hidden inside the cargo bay of the ship on the extreme left; that rover has a drill and an converter, and will dock with the lander on the surface to refuel it.

And that is what ISRU means to me

Edited October 6, 2015 by Kuzzter

[AbacusWizard]

I set up a large fuel production operation on Minmus a while back. There's a mobile combine (mine/refinery) and a huge surface-to-orbit tanker: the tanker docks with the combine; the combine drills for ore, converts it to fuel, and pumps it directly into the tanker; the tanker detaches, takes off into orbit, and rendezvous with any ship in Minmus orbit that needs refueling (or waits around as an orbital fuel depot).

Net result: all of my Minmus orbital projects (and there are many of them) get unlimited free fuel, and I can launch my interplanetary ships with their tanks nearly empty (a significant savings on the mass I have pull out of Kerbin's gravity well), with just enough fuel to get them to Minmus orbit, and then top them up completely with said free fuel.

[damny]

I mostly think of ISRU as a mechanic that provides additional goals. It makes bases and stations more useful and gives me reasons to use them after I launch them. Yeah it's also free fuel, but I got everywhere I wanted to without mining, so the free fuel is just a side effect. (It's certainly not as powerful as Kethane used to be in the old days when I ran that.)

In this sense, it's not really "important" - you can run a space program without it and still do everything. But it gives you more options, which is what sandbox games run on.

[magnemoe]

I mostly think of ISRU as a mechanic that provides additional goals. It makes bases and stations more useful and gives me reasons to use them after I launch them. Yeah it's also free fuel, but I got everywhere I wanted to without mining, so the free fuel is just a side effect. (It's certainly not as powerful as Kethane used to be in the old days when I ran that.)

In this sense, it's not really "important" - you can run a space program without it and still do everything. But it gives you more options, which is what sandbox games run on.

Yes, it also let us scale up missions, and they have to be scaled up to use ISRU.

If you only send an kerbal in a pod to plant the flag you don't need ISRU, sending 4-5 some hitchhiker containers and science lab and plan on doing multiple landings and ISRU makes things much easier.

It mainly has two reasons, first is to create an base who also act as fuel station at target.

Second is to create fuel station in LKO who you supply from Minmus. This takes time and resources but will save a lot then sending large payloads interplanetary.

More advanced it biome jumping on Laythe and Tylo using an lander or spaceplane with ISRU

[More Boosters]

What is the purpose in field refueling? Gee I wonder.

[Wjolcz]

People don't like ISRU because it doesn't seem very useful. In my opinion the idea of ISRU is pretty damn cool, but the problem is the game doesn't force you to use it much.

Imagine if LS became a thing. Add crew rotation and KIS/KAS-like base maintance contracts and suddenly getting fuel from the surface of the planet becomes a key to keep your base alive.

Let's say you have a Duna base and you need to keep it occupied by crew for X years because a contracts tells you to do so. There's also a contracts that tells you to rotate the crew from time to time. The base has a functioning shuttle (that needs refuelling after going to orbit and back) that carries the crew to the interplanetary mothership and retunrs back to base with new colony/base members. You also need to get some new water/other LS resource from the ground, because otherwise your base inhabitants will starve to death. So now ISRU not only keeps your shuttle functional but also keeps your crew alive!

So, yeah. We need new stuff to make ISRU more interesting because the base game doesn't cut it.

Edit: I think I might also post this in S&DD subforum.

Edited October 6, 2015 by Veeltch

[KerikBalm]

Basically, it allows unlimited travel at a destination.

I find it often makes things too easy.

Its hard to haul significant quantities for fuel to Moho with a fully reusable/recoverable system.

My last mission I sent with no ISRU had provisions for just 3 landings of a 1 man lander - although a subsequent dedicated fuel tanker could carry more fuel to the orbiting Moho station/fuel depot - since a fuel tanker could drop the mass of the hithiker, mk1-2 pod, and science bay, at the expense of having to carry more empy tanks back to kerbin.

Its a lot easier to just mine on the surface of moho, and launch the fuel to orbit, than to do another interplanetary mission, particularly one with one of the highest dV requirements in the game (just to establish orbit, i think it is the highest).

Eeloo may require less dV, but that travel time... ughhh, no, if you run out of fuel and need to send a tanker, it will take years... you can min the fuel right there if you wish though (although giving your craft enough power to mine at a reasonable rate is difficult).

A reusable tylo lander used to be very hard to pull off.

Now you only need to get down to the surface, then you can refuel... with ISRU, its so easy.

the ISRU converter is barely heavier than a mk1-2 pod. The drills are pretty light too... (0.75 tons)

You could have a complere ISRU setup for less than 6 tons, and it can produce a lot more than 6 tons of fuel

[Curveball Anders]

I like them because they give yet another type of brick in my box of toys.

Like building a fuel station on an asteroid.

Not because I need one, but because I can do it.

[Joonatan1998]

Usually you have to see ISRU as a goal in itself, not as a tool to achieve other goals.

Unless you are trying something like a grand tour, using ISRU generally makes it harder and more expensive.

Refueling Eve ascent craft could maybe work.

I think a planet pack that replaces the entire Kerbol system with a new one that doesn't any inhabited planets could be fun.

At start player would get a ship carrying ISRU and EPL equipment.

Alternatively just having harder to reach places would make ISRU more useful.

[Wjolcz]

I think a planet pack that replaces the entire Kerbol system with a new one that doesn't any inhabited planets could be fun.

At start player would get a ship carrying ISRU and EPL equipment.

That's how I imagine KSP2 if it ever happens.

Edited October 6, 2015 by Veeltch