The usefullness of deep-space re-fueling

[KerikBalm]

Im gonna be blunt. What is the point of re-fueling on another planet? Are you really getting more dV per distance ratio? Here is some situations people have been known to do.

Arrive with empty tanks, don't bring any fuel for the return trip... refuel there, seems pretty good to me.

Before this addition, I already used large SSTOs to lift large amounts of fuel, and set up fuel depots at planets of particular interest. Landers would be SSTOs (allexcept Tylo and Eve). Now I can make larger SSTO landers to lift fuel from the surface to the orbiting fuel depot.

1. Go to Jool and re-fuel at Minmus - I honestly think this produces a negative net value of fuel consumption. By the time you have retro-captured , rendezvous or aero braked to your re-fueling point, and then to break that orbit all over again, you have wasted more fuel than you have gained overall.

How about: Launch to LKO, transfer to minmus, top up tanks there. If you did that with an SSTO, you should now have thousands of m/s of dV, and a Jool intersect only takes ~1,200 m/s from the orbit of minmus.

On the return from Jool, you can aerobrake to get your AP out to the orbit of minmus, and do a capture + refuel, and be ready to go again (remember, it takes much less dV to get to Jool from Minmus than it does from LKO)

2. Land at the Mun , then land again, and again to explore more - This one seems really efficient as your using 0 dV to arrive at a re-fueling point. Providing you landed at a rich drilling area.

How about: Fuel station on the Mun sends tankers up to an orbiting fuel depot. Your exploration craft can just repeatedly refuel at that orbiting fuel depot. It can land where-ever it wants in this case, without worrying about the richness of the drilling area, or taking the drills and processing equipment with it.

3. Refueling at a LEO station to then go interstellar - Im not totally sure on this. If you can brute force rendezvous from the surface with pin point accuracy , topping off fuel can actually give you a pretty chunky net gain of fuel. If your rendezvous are sloppy and use like 6 burns, well not so much.

#1) I think you mean interplanetary.

#2) I'd rather refuel farther out from LKO, so there is less dV to spend after refueling. How about refueling in high Mun orbit? The dV difference for interplanetary trajectories from high Mun orbit vs high Minmus orbit isn't that much.

But I could also see simply using SSTOs to get a payload with empty tanks to LKO, and then a tug that fils those tanks and ejects the payload from the kerbin SOI. The tug then refuels at minmus

Feel free to discuss, add your unique situations, and tell us did it give you the results you were looking for. I voted that interplanetary re-fueling using planets as checkpoints is far detrimental to your dV.

The way I see it, its best for sustained operations. I expect the initial equipment to be so heavy, that you don't want to take it very far*, and thus you won't get much out of using it - for a single mission.

Once you have set up a mining operation, all future craft there can arrive with empty tanks. It also would be a massive help for biome hoppers.

* for example, if the mining setup weighs 50 tons... you really don't want to build a craft to take 50 tons of to Moho... and if you did, 50 tons of fuel should get you far more dV for the return trip anyway.

I suppose you could stop at gilly and refuel, to make it a little easier to get 50 tons to Moho... but then your mission takes a lot longer.

You could also leave your refueling gear at Gilly, and do a gilly -> moho transfer. This would require a dV of about 1,100 m/s less.

Coming back (with an eve aerobrake)... you'd need roughly 800 m/s less. SO if you set up a Gilly fuel station... you could do a moho round trip with a craft dv between refuelings of about 2,000 m/s less

My goal is to have fuel stations on pretty much every body ... except Eve.

Maybe even Eve. With the aero changes, SSTO might be possible... and an empty lander weighs much less than a full one. It would be more economical in the long run to send empty landers, and refuel them on the surface.

[Musil]

I am currently planing a Moho mission and I would certainly like the option to refuel at Eve. Maybe not on the way there, since the point of this mission is to use the gravity assist of Eve to help me get to Moho with as low a relative speed as possible (and salve all the d-v of the plane change), but at return it would certainly be nice to go Moho-Eve instead of the aggressive Moho-Kerbin.

For the Jovian system it would be endlessly useful. I also like the idea of having a refueling base at the Mun or Minmus to explore that moon. In my last career, I ended up sending like a dozen Apollo style missions... I would have saved a lot of money and time by just refueling the lander there.

[lextacy]

@RoverDude Hey arent you that guy that made the Karbonite mod?

@Musil - I think that is not a good idea becasue you have to retro 1500 m/s just to slow down into Eve orbit. You would rather save that 1500 delta to extend you to Moho. I think having a refuel depot at Moho is a better option.

@General Posters - What you guys are posting is from expierence in deep space travel/colonization and now I have new light on the subject. My space program has just only made 1 manned trip to Duna. So my knowlege is rusty here. It does look form all your posts that deep space refueling is prominent more than I thought. What is the deltaV hit for slowing down to Minmus anyways?

[Bill Phil]

?

@Musil - I think that is not a good idea becasue you have to retro 1500 m/s just to slow down into Eve orbit. You would rather save that 1500 delta to extend you to Moho. I think having a refuel depot at Moho is a better option.

Aero-capture and subsequent aerobraking. It works wonders.

[Musil]

I think lextacy understood getting into Eve orbit and then escaping to Moho. If that's the case, that's not the plan: you use the gravity of Eve to slow you down or change your inclination; in one case you can get your Sun apoapsis at Eve's altitude and your Sun periapsis at around halfway to Moho's orbit; in the other, you get the inclination change for almost free. You don't get captured at Eve for this, so having the fuel there when going to Moho would serve no purpose. The idea is that when going back, instead of going Moho->Kerbin, you only need to go to Eve, refuel and then go back home.

Geting captured by Eve is for free: aero-capture means decelerating is no problem.

That said, having a refueling base at Moho would be very good if you are thinking about doing more than one mission. If not, geting the equipment there would probably be too d-v expensive... depending on how much the equipment ends up weighing.

[Der Kosmos]

I've considered building a massive Kethane operation on Gilly, and then shipping Orange tanks to Kerban, Duna, and Jool from there. I think if done right that would be the cheapest delta-v wise.

I've never been able to get a good Kethane set up myself, Mostly I've just fiddled around trying to make a good lander for proof of concept mining operations on the Mun. I have however, managed to make it home from Gilly with a capsule I'd normally use for a Mun Flyby, after crashing my Nuclear powered deep space exploration vessel.

Edited March 15, 2015 by Der Kosmos

[Musil]

I've considered building a massive Kethane operation on Gilly, and then shipping Orange tanks to Kerban, Duna, and Jool from there. I think if done right that would be the cheapest delta-v wise.

I don't think sending an empty tank to Gilly and then sending it full to Jool is going to be economic. Better to make that base at Minmus. Better yet, I think, would be doing it at one of the smaller moons of Jool, if that's your final destination.

[Wjolcz]

I wonder how much the resource is going to cost? Maybe it will be proftable to bring it back to Kerbin? I would like that very much actually. Would add a nice space industry element, or something.

[magnemoe]

I don't think sending an empty tank to Gilly and then sending it full to Jool is going to be economic. Better to make that base at Minmus. Better yet, I think, would be doing it at one of the smaller moons of Jool, if that's your final destination.

Gilly is an place to refuel Eve accent crafts as they use lots of fuel. One idea is to make an Eve tug, think an high TWR tug optionally with living quarters who push stuff towards Eve, they either go to Minmus or meet with an tanker in Eve orbit, drop payload tops up tanks again and wait for transfer window back. While doing so they can take fuel from Gilly to Eve orbit.

Ike and the minor moons of Jool can serve the same purpose, Laythe is the natural gathering place in Jool system, an interesting place and you can aerocapture into orbit.

[ShadowZone]

I have made good experiences with refueling in LKO. My ships are usually on the bigger side so it takes a lot to get them into orbit. But once they are there, I sometimes even have one of the stages not yet dumped, so I can refuel that and have massive dV to do my journeys.

[Van Disaster]

A couple of games back I used to ship fuel from Minmus back to LKO ( well ok it was Kethane to make fuel but essentially the same ). I'm not even sure that saved that amount of fuel overall in the end, but what it did mean was I had smaller launches, or more hardware went up on the same launch, so it most definitely saved on cost - or at least would have if we had costs back then it was most definitely more interesting than endless tanker launches to LKO.

Skipping the LKO part entirely and building ships on Minmus was even better, but you won't be able to do that in stock 1.0...

[magnemoe]

I just sent an 100 ton dryweight Moho craft on its way from Moho

it refueled on Minmus, then went into high kerbin orbit close to minmus as it made it easier to plan the drop down towards Kerbin so Pe intercepted the burn trajectory, I used an satellite as marker to get the start of drop burn then mechjeb to get the main burn then tweaked a bit, fun part is the booster stage, fallback plan was to build an minimal lander and miner probe to gather enough resources for me to land. This will not be needed as estimates shows I will have more than 2km/s left in Minmus orbit. 360 m/s adjustment and 3.2 km/s orbital injection with 5.5 km/s after Moho injection burn of 860 m/s. burn was dead accurate because of the shorter burn time.

[Der Kosmos]

An empty tank headed to Gilly can use Aerocapture at Eve. Then once it's full, it can use the Oberth effect to slingshot off of Eve and then Aerocapture at Jool. I haven't run the numbers but as far as ways to save delta-v go, Starting on Gilly and ending on a plant with an atmosphere can't be beat. It looks like a roundabout trip, but it should be the most energy efficient.

Moving an empty fuel tank from Kerban to Eve orbit shouldn't be too hard either.

[samstarman5]

I wonder how much the resource is going to cost? Maybe it will be proftable to bring it back to Kerbin? I would like that very much actually. Would add a nice space industry element, or something.

This is exactly the line of thinking that brings more out of a feature than what is usually only seen. I like your style!