Getting fuel to Station

[Foxdemon]

I have a station around kerbin (equatorial) and the mun (polar) and i want to build one around minmus, but i have trouble refuelling.

Can someone give me some inspiration (only pics, no craftfiles) to make a reusable spaceplane SSTO to transfer this to LKO and/or minmus:

-Jumbo fueltank

-Largest RCS-tank

-HECS probe-core

-A few RCS ports

-2 1x6 solarpanels

-A docking port

PS and what kind of orbit should i choose for the station around minmus, because equatorial has the advantage that it can better sustain interplanetary refuelling, but with polar orbit i can use my miningrover anywhere.

Edited June 11, 2015 by Foxdemon

[Warzouz]

A full Minmus exploration will need only half an orange tank. The biggest RCS tank is overkill if you only use it to dock procedure. You can size it down.

Your payload is around 50T with fairing. For a cheap price, you can use SSTO rocket stage : http://forum.kerbalspaceprogram.com/threads/123195-Cygnus-family-Recoverable-SSTO-Rockets-from-12-to-236-tons. There is a 52T launcher that can fit you needs. You only have to add a transfert stage which will be able to carry you payload to Minmus orbit and rendez-vous with your station (around 1200dV).

Personnally, I usually create space stations with predesigned docking ports

- Docking ports for ships (lander and return ships)

- Docking ports for extensions

- Docking ports for refuelling tanks

Refueling tanks are minimal : an orange tank, 2 docking rings and RCS packs (no RCS fuel). I handle them with a separate mini tug powered by RCS. This minimize part count.

Now, I even embed the fuel tanks in the station. I orbited a 2 NASA biggest tanks with the station on top in one launch. The solar pannels on top, the extension at the bottom and te rings for ships in the middle. I don't use dock for refueling tanks. I just send tanks, fill the station and dump the tanks immediatly.

My Kerbin station. Minmus station is the same but only with a oragne tank (already overkill)

EDIT : Think your station ahead or you'll probably need to trash it quite quickly.

Edited June 9, 2015 by Warzouz

[Wanderfound]

Pics only as requested:

Javascript is disabled. View full album

I'd throw the station into an equatorial orbit, even at Minmus. Minmusian orbital speeds are so low that inclination changes are very cheap.

[Foxdemon]

A full Minmus exploration will need only half an orange tank. The biggest RCS tank is overkill if you only use it to dock procedure. You can size it down.

Your payload is around 50T with fairing. For a cheap price, you can use SSTO rocket stage : http://forum.kerbalspaceprogram.com/threads/123195-Cygnus-family-Recoverable-SSTO-Rockets-from-12-to-236-tons. There is a 52T launcher that can fit you needs. You only have to add a transfert stage which will be able to carry you payload to Minmus orbit and rendez-vous with your station (around 1200dV).

Personnally, I usually create space stations with predesigned docking ports

- Docking ports for ships (lander and return ships)

- Docking ports for extensions

- Docking ports for refuelling tanks

Refueling tanks are minimal : an orange tank, 2 docking rings and RCS packs (no RCS fuel). I handle them with a separate mini tug powered by RCS. This minimize part count.

Now, I even embed the fuel tanks in the station. I orbited a 2 NASA biggest tanks with the station on top in one launch. The solar pannels on top, the extension at the bottom and te rings for ships in the middle. I don't use dock for refueling tanks. I just send tanks, fill the station and dump the tanks immediatly.

My Kerbin station. Minmus station is the same but only with a oragne tank (already overkill)

http://tof.canardpc.com/preview2/87a04a29-f68b-4eb4-9842-d0b7e84769c1.jpg

EDIT : Think your station ahead or you'll probably need to trash it quite quickly.

Yeah i know i need to plan the station, but i already have 2 of the same stations in orbit of kerbin and the mun like i said. I want to fill the predesignated dockingports (which i set up on the space stations) with the tanks so other crafts can refuel, not just the station (the station will be there forever). The reason im doing this is because i want some fuelcapacity on the station so i can transfer fuel from my miningrover to my station (to keep it full)

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Pics only as requested:

http://imgur.com/a/Y2VUG

I'd throw the station into an equatorial orbit, even at Minmus. Minmusian orbital speeds are so low that inclination changes are very cheap.

Yeah looks nice, but for some reason i always end up not having enough fuel or thrust,m even with 6 rapiers... (i used LV-N, but those dont have enough thrust and rapiers use a lot of Lf/O). Can you give me your ascend profile and some fueldata?

[Wanderfound]

Yeah looks nice, but for some reason i always end up not having enough fuel or thrust,m even with 6 rapiers... (i used LV-N, but those dont have enough thrust and rapiers use a lot of Lf/O). Can you give me your ascend profile and some fueldata?

I'm flying with FAR, so there will be some differences if you're in stock. You can see the profile and fuel remaining in the album above, but in general:

1) Climb to above 10,000m at a sufficiently steep pitch that you remain subsonic until you're out of the thickest bits of the atmosphere.

2) Level off to about a 10° pitch so as to crank up the speed to at least Mach 3 (and preferably 4+) by the time you hit 20,000m.

3) Keep it mostly level as you approach the jet ceiling (between 20 and 30km, depending on ship and piloting) in order to maximise your jet speed.

4) Light the rockets and gently lift the nose as soon as you maximise your jet speed.

In all of this, keep an eye on temperatures. If you start to cook, climb more steeply. Kerbal Flight Data is very useful for this (and for other stuff, too; highly recommended for all spaceplaners).

The profile will vary a bit based on the design. If you're well within your temperature limits, a shallower climb is usually worthwhile; if you hit the jet ceiling before you get up to speed, a Silbervogel style "climb and bounce" ascent (as shown above) can be helpful.

That trick works better in FAR than stock, though; stock tends to apply excessive deceleration as you lift the nose during the "bounce". The stock ascent profile is fairly similar to FAR these days, but with a slightly lower jet ceiling and a greatly reduced ability to maintain speed while manoeuvring. Design-wise, FAR allows you to get away with a bit less in the way of engines, but tends to require a bit nore in the way of wings and tailfins.

If you're just trying to get a heavy load to LKO, stick to jets and high TWR oxidising rockets (e.g. RAPIERs, or a Turbojet/Skipper combo etc). Nukes are best kept for interplanetary.

[RuBisCO]

Every time I haul up cargo I leave left over fuel up at the assembly station or in the cargo. I use Minmus mining primarily for for fueling up though.

[Foxdemon]

Pics only as requested:

http://imgur.com/a/Y2VUG

I'd throw the station into an equatorial orbit, even at Minmus. Minmusian orbital speeds are so low that inclination changes are very cheap.

I build something similar with 2 engines extra and it doesnt have enough twr :/. The twr is about 0.7 and the speed decreases slowly under a 20 degree ascend. I dont think your plane has that problem?

[Reactordrone]

Basic rocket version, about 80,000 funds. All skippers on the first stage with onion staging will get a full orange tank with some fuel left in the first stage core into Kerbin orbit.

[cybersol]

A stock 1.0.2 heavy orange spaceplane SSTO:

Javascript is disabled. View full album

A rocket SSTO for 50t payloads:

[Warzouz]

@cybersol : On your rocket SSTO, why do you have so much fins ?

I only use wings, one per engine. (here is 40 and 60T) Your 50T would be the 60T without the central skipper and less fuel.

Event my heaviest 240T have onlys the same wings.

[Wanderfound]

I build something similar with 2 engines extra and it doesnt have enough twr :/. The twr is about 0.7 and the speed decreases slowly under a 20 degree ascend. I dont think your plane has that problem?

Spaceplanes can fairly easily be made to work with TWRs much lower than that. But the ascent path is not a straight line.

Climb above the thick/hot/draggy lower atmosphere, level off and/or go into a shallow dive while you crank up the speed, then climb. Jet thrust increases with speed (up to a point) but decreases with altitude; you need to balance the two against each other. Climb too fast and you won't have enough thrust to accelerate; climb too slow and you'll cook. So climb fast through the thick atmosphere, and slow through the thin.

[cybersol]

@cybersol : On your rocket SSTO, why do you have so much fins ?

Most of all, it was carrying a long, awkward, draggy payload in an fairly early career save (mainsails were experimental). Also, I was just coming to realize it was all about control and the delta fins have a relatively small deflection edge. A more modern version uses a large reaction wheel, which was unavailable in my career at that point, and "only" 12 lower and outside AV-R8 fins instead. I was intrigued by you thoughts though, so I dug the design out and re-tried out some wings. Wings are simply not as effective on this rocket with this payload. With both 4x type A (your pictures) and even 4x delta (2x lift) instead of the control fins the rocket simply doesn't have enough control authority to get through the transonic region effectively (in stock career, with that crazy payload and no larger fairings available).

[Sharpy]

3) Keep it mostly level as you approach the jet ceiling (between 20 and 30km, depending on ship and piloting) in order to maximise your jet speed.

4) Light the rockets and gently lift the nose as soon as you maximise your jet speed.

Looking at different atmosphere vs vacuum ISp and thrust profiles of various rocket engines, trying to find one good for the 20km-50km range, between jets and whatever orbital, I found one more alternative: "None."

Make the final leg of the jet-powered climb somewhat more steep, like 45 degrees. Let them sputter out, then do nothing until you reach 50km. Only then power up your rockets. They work at maximum efficiency now. Sure you lose quite a bit of your speed, but slower atmospheric ascent means less wasted thrust(=fuel) against air drag, and whatever you need to make up for the lost speed, you'd use up on keeping it high in the first place.

The funniest trajectory was when the jets were only at some 1.6 TWR. I'd climb to some 6-8km until their thrust totally dies, then dive at a sharp angle downwards. After some 500m/s they gain enough thrust to let me go steeply up and still keep gaining speed, toss me high above the atmosphere and then speed up with my rockets.

[Foxdemon]

Sorry, i should have said it, but im not looking for a rocket SSTO, because i really dont like them :/. So to be clear im looking for 1 or 2 reusable spaceplane SSTO's which can go to kerbin and minmus respectively (it doesnt need to be able to land on minmus)

[OddFunction]

I'm a little confused. How can there be a rocket SSTO, especially one with multiple stages? I thought the point of an SSTO was that it didn't jettison any parts, you control its engines with actiongroups and it just goes to orbit and back in one piece?

[Foxdemon]

Havent thought about the diving yet, ill try that.

http://imgur.com/DCrVsVU,VUYBz6a,lppg8BS,541peg0,XRIcFE4

Think this is good enough, or is it too draggy/needs more thrust?

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I'm a little confused. How can there be a rocket SSTO, especially one with multiple stages? I thought the point of an SSTO was that it didn't jettison any parts, you control its engines with actiongroups and it just goes to orbit and back in one piece?

A rocket SSTO doesnt have multiple stages, otherwise it isnt a SSTO...

Rocket SSTO's mostly use a crapton of parachutes to get back on kerbin as a whole.

[OddFunction]

Havent thought about the diving yet, ill try that.

http://imgur.com/DCrVsVU,VUYBz6a,lppg8BS,541peg0,XRIcFE4

Think this is good enough, or is it too draggy/needs more thrust?

Just a tip, I don't believe you need fuel lines at all. I'm almost positive that for spaceplanes the fuel just goes to the engine automatically. I remember testing this just the other day.

A rocket SSTO doesnt have multiple stages, otherwise it isnt a SSTO...

Rocket SSTO's mostly use a crapton of parachutes to get back on kerbin as a whole.

Seems madly inefficient compared to a well-built plane.

[Foxdemon]

Just a tip, I don't believe you need fuel lines at all. I'm almost positive that for spaceplanes the fuel just goes to the engine automatically. I remember testing this just the other day.

Sorry, but the tooltip in the SPH says that those engines are not getting any oxidizer. Is it a bug that it says this or am i right? (Not playin KSP when typing this, so cant test now)

[UnusualAttitude]

Air breathing engines draw liquid fuel from all tanks without fuel lines. Rockets, including RAPIERS in closed cycle do require them however.

[cybersol]

For me, SSTOs deliver fuel, stations, and mission ships to LKO. Re-usuable space tugs, usually nuclear, then take them to their destination and back. For Minmus, I sent a station with fuel and a reusable lander with a scientist in it. That mission returned over 4000 science.

Seems madly inefficient compared to a well-built plane.

More efficient than throwing most of the rocket away. Able to handle large and awkward payloads easier (unless your KerikBalm). Available earlier in career mode.

[Warzouz]

Seems madly inefficient compared to a well-built plane.

They may not be as efficient as plane SSTO, but they are easier to design, to fly and to land... In addition, there is no payload limit to rocket SSTO.

I use SSTO rocket familly which ranges from 12T to 240T payload.

Designing a heavy load plane SSTO is hard.

[OddFunction]

Sorry, but the tooltip in the SPH says that those engines are not getting any oxidizer. Is it a bug that it says this or am i right? (Not playin KSP when typing this, so cant test now)

Air breathing engines draw liquid fuel from all tanks without fuel lines. Rockets, including RAPIERS in closed cycle do require them however.

Ah I stand corrected. I was amazed when I saw it worked without fuel lines, so I guess I just thought it was a spaceplane specific thing instead of an engine specific thing. Thanks for the correction

For me, SSTOs deliver fuel, stations, and mission ships to LKO. Re-usuable space tugs, usually nuclear, then take them to their destination and back. For Minmus, I sent a station with fuel and a reusable lander with a scientist in it. That mission returned over 4000 science.

More efficient than throwing most of the rocket away. Able to handle large and awkward payloads easier (unless your KerikBalm). Available earlier in career mode.

Well then, maybe I'll go make an orange-tank carrying SSTO rocket and see for myself

[Wanderfound]

Havent thought about the diving yet, ill try that.

http://imgur.com/DCrVsVU,VUYBz6a,lppg8BS,541peg0,XRIcFE4

Think this is good enough, or is it too draggy/needs more thrust?

The most immediately apparent issue I see is that your engine placement is likely to burn your tailplane off...

BTW, a vertical SSTO example:

Javascript is disabled. View full album

[Warzouz]

Most of all, it was carrying a long, awkward, draggy payload in an fairly early career save (mainsails were experimental). Also, I was just coming to realize it was all about control and the delta fins have a relatively small deflection edge. A more modern version uses a large reaction wheel, which was unavailable in my career at that point, and "only" 12 lower and outside AV-R8 fins instead. I was intrigued by you thoughts though, so I dug the design out and re-tried out some wings. Wings are simply not as effective on this rocket with this payload. With both 4x type A (your pictures) and even 4x delta (2x lift) instead of the control fins the rocket simply doesn't have enough control authority to get through the transonic region effectively (in stock career, with that crazy payload and no larger fairings available).

Ok, I understand

Truthfully, early version of my rockets had much more bigger wings and even winglets just below chutes/cones. This went very well until I was fed up with winglets blowing up and remove them. There was nearly no difference. Then I reduced the bottom wings, and also, no difference except a slight sliding now and then with some rockets.

I usually build tall payload (not broad) and I always use fairing. It's heavy, but again, the real cost of one launch is very low, especially swith those mammoth SSTO variation.

For example, here is my first Duna mission

The space station flight

The mission flight (with landers, return vehicle and double stats)

(Click to enlarge)

PS : sorry for the topic squatting...

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The most immediately apparent issue I see is that your engine placement is likely to burn your tailplane off...

BTW, a vertical SSTO example:

http://imgur.com/a/aaddn

This is a very nice design. What is you payload efficiency in mass (payload mass/total wet mass) and in price (net cost [Launcher cost - recovered cost] per payload ton) ?

[Wanderfound]

This is a very nice design. What is you payload efficiency in mass (payload mass/total wet mass) and in price (net cost [Launcher cost - recovered cost] per payload ton) ?

Haven't the foggiest; if I was launching a small payload like that in my career game, I'd probably just stick it on top of a large SRB and eat the extra expense. That or stash it in the cargo bay of a spaceplane, to be dropped en-route to somewhere else. The only flight cost apart from the payload is the tiny amount of fuel consumed; one FL-T800 for LFO, plus a sniff of LF for the airbreathing portion of the flight.

The craft file is at https://www.dropbox.com/s/bki39ohbj7vr40i/Kerbodyne%20Jetlift.craft?dl=0

It would probably improve the design to ditch the intercooler and put the engines and fins straight onto the LFO tank. It has more than enough LF and intake, engine heating isn't a problem, and the weight reduction would give a bit more margin in oxidising thrust. At the moment, it has just barely enough O to deorbit after reaching LKO.