Fuel lift for orbital refuel station.

[Billyk88]

Hi I am looking for any ideas how to make a rocket that can lift 3 Rockomax X200-32 Fuel Tank put together up to 200,000 m orbit where my refuel station is around kerbin.

thank you for any ideas.

[TheDarkStar]

You might want to do it with a few separate launches to make it easier. I usually do that instead of taking twice as long to make something to do it in one launch.

[Jouni]

That payload is quite nice, because you still have a lot of options how to get it into orbit. With 4-5 fuel tanks, you would already require a lot of boosters or excessive asparagus staging, because the stock engines are not powerful enough.

For example, my heavy lifter should be able to get the fuel tanks (and a docking port and the parts required for docking) to a rendezvous at 200 km orbit.

Basically there are four boosters in asparagus configuration, five Mainsail engines, some radial engines, and a lot of fuel. Here is another picture of the lifter after booster separation.

[Armchair Rocket Scientist]

Hi I am looking for any ideas how to make a rocket that can lift 3 Rockomax X200-32 Fuel Tank put together up to 200,000 m orbit where my refuel station is around kerbin.

thank you for any ideas.

That payload is about 100 tons (give or take extra for RCS, reaction wheels, probe cores, girders, etc). With a payload fraction of 15% for an asparagus-staged rocket, you should have a launch mass of about 750 t. Six mainsail-powered boosters and a core with 4 LV-T45s and 8 LV-T30s should lift that comfortably. For equal fuel on each stack, give each 2 orange tanks and one of the smallest 2.5m tanks on the bottom.

Now add struts as necessary.

If you want it serial-staged, you'll probably need 900-1000 tons of rocket: 9 mainsails in the first stage would be a good choice for getting it off the pad.

Now might be a good time to read up on construction techniques for large vehicles, such as thrust plates. In addition, if you don't have a fast computer (or even if you do) you should consider downloading Kerbal Joint Reinforcement. On large vehicles, probably the biggest contributor to CPU-melting part counts is the huge number of struts required.

Edited February 18, 2014 by Armchair Rocket Scientist

[Jouni]

That payload is about 100 tons (give or take extra for RCS, reaction wheels, probe cores, girders, etc).

Note that the fuel tanks were X200-32s, not Jumbo-64s. That's why I said the payload is nice, as you can still handle it without super-heavy lifter construction techniques.

[Billyk88]

I am in career mode so I do not have the mainsail engine or the big orange tanks. thanks for the ideas but any ideas for career mode lifts?

[SpaceGremlin]

When I wanted to push 90 tons of equipment out to Jool early in my career I needed a monster drive section. Here's how I launched it:

The final payload is a bundle of 7 Rocko 32's with a Skipper (130 tons). Has roughly 4600 dV in the first two stages so its not burning payload fuel. Its all Rocko 32's and skippers, so you should be able to adapt a smaller design for your purposes.

[Jouni]

Career mode makes things more complicated. Two X200-32 fuel tanks and some struts can easily replace a jumbo tank, so your real problem is the lack of powerful engines. If you don't have Mainsails, you probably don't have cubic octagonal struts either, so clusters of small engines are much harder to set up.

You could try something like this:

- The core has three X200-32 fuel tanks and a Skipper engine.

- Around the core there are six boosters with two X200-32 fuel tanks and a Skipper engine each.

- There are two large solid fuel boosters attached to each of the main boosters.

- The payload has one extra X200-8 fuel tank to account for the mass of the other components you may need.

All boosters fire at liftoff. The core engine is ignited when the solid fuel boosters are separated. In this configuration, the lifter has barely enough fuel to reach orbit, so some tweaking is needed. You may also want to add some Rockomax 24-77 radial engines to the payload for orbital maneuvers.

[breakthrough]

...you probably don't have cubic octagonal struts either, so clusters of small engines are much harder to set up.

An FL-R10 RCS Fuel Tank (the probe sized inline mounting one) only weighs 0.05 tons empty, can surface attach, and has nodes on both ends. Its much lower in the tech tree and besides not being weightless can do anything a cubic strut can.

Also, even though the starting girder segment has some weight to it, a six way symmetry cluster of LV-T30's is still better than a mainsail, even with the extra ton or so in mounting equipment.

[Jouni]

An FL-R10 RCS Fuel Tank (the probe sized inline mounting one) only weighs 0.05 tons empty, can surface attach, and has nodes on both ends. Its much lower in the tech tree and besides not being weightless can do anything a cubic strut can.

Also, even though the starting girder segment has some weight to it, a six way symmetry cluster of LV-T30's is still better than a mainsail, even with the extra ton or so in mounting equipment.

You don't have the space to attach engines radially, when you have a core stage surrounded by boosters. You also can't attach multiple FL-R10s to the bottom of a fuel tank without part clipping, which many people consider cheating. Six LV-T30s attached with modular girder segments have 2.25 tonnes more mass and 14% less thrust than a Mainsail, and they come without thrust vectoring.

[breakthrough]

You don't have the space to attach engines radially, when you have a core stage surrounded by boosters. You also can't attach multiple FL-R10s to the bottom of a fuel tank without part clipping, which many people consider cheating. Six LV-T30s attached with modular girder segments have 2.25 tonnes more mass and 14% less thrust than a Mainsail, and they come without thrust vectoring.

Both the TT70 decoupler and sepatrons will be available if you have the parts the OP has.

As for the Mainsail, I did indeed forget that I always mount a LV-T45 on the node and put the girders+LV-T30s around it. You are right that the thrust will be lower, but 1.2 TWR will make orbit just as well as 2 will. In addition to that, the Isp will be far higher and is far more important once you are in orbit.

[beardysi]

I managed to get 5 oranges up (full) in one go a while back... (think it was in 0.19) though it did take me the guts of a week to get it right! Each of the outer tanks had a stage consisting of 2 orange tanks and cluster of LVT-30's around a central LVT-45. Outside those was a layer of mainsail LRB's. It was an absolute ***** to fly (and dock with my fuelling station!) but it did the job. Sadly I don't think I've got any pics of the finished station...

Just about scraped a 75k orbit and I sent down a heavy tug to bring it up to the station.

[Jouni]

http://i.imgur.com/KZI5CDA.png

Both the TT70 decoupler and sepatrons will be available if you have the parts the OP has.

As for the Mainsail, I did indeed forget that I always mount a LV-T45 on the node and put the girders+LV-T30s around it. You are right that the thrust will be lower, but 1.2 TWR will make orbit just as well as 2 will. In addition to that, the Isp will be far higher and is far more important once you are in orbit.

Now try adding those engine clusters to all of the 4 or 6 boosters as well. It's probably doable, but it takes a lot of effort. We were talking about lifting large loads, so we should be aiming at something like a Mainsail at the core and at each of the boosters. And while TWR 1.2 gets you eventually to the orbit, it will waste a lot of fuel before that. 1.5 to 2.5 is generally the best range, until you are high in the atmosphere, moving almost horizontally.