Help me get a Rockomax Jumbo-64 Fuel tank into orbit

[Delta_scientist]

I've tried countless rockets, but I cant seem to get a simple Rockomax Jumbo-64 Fuel tank into orbit (250km up). I try to get a rocket with around 4.5k dV but everytime it flips over during ascend. Or it gets to heavy (200+ tons). I tried everything but that thing is to big and heavy

[h=3][/h]

[Wanderfound]

Heavy bits at the top, draggy bits at the bottom, gimbal is good. Do a proper gravity turn (i.e. not "climb to 10km, then wrench the nose to 45°") and keep the nose close to prograde. That's all there is to it, really.

So, if you're flipping: tailfins. And gimbal. Strapping a quartet of Thuds to your core booster is an easy way to substantially boost your gimballing ability. You'll also gain a large benefit from onion or asparagus staging; run fuel lines from the radial boosters to the core, so that the core is still fully fuelled when you drop the boosters.

Something like a Skipper/Thud core surrounded by onion-staged Mainsail LFBs should do the job fairly easily. But, yes, it's going to be a bit heavy; a 36 ton payload is not a small lift.

[Delta_scientist]

I'm using Mechjeb.

[capi3101]

<snip /> But, yes, it's going to be a bit heavy; a 36 ton payload is not a small lift.

Yep. Very much this - let's see what we can do with '>Temstar's guidelines to help you out. 36 tonne paywad = 240 tonne rocket. 1.5 TWR on the pad = 3528 kN thrust. 22% thrust in the core = 776.16 kN (a Mainsail set to 56% thrust). Three booster pairs = 458.64 kn (Skippers set at 81% thrust). Mainsail weighs six tonnes, Skippers weigh three = 24 tonnes of engines. 240 tonnes total - 36 tonnes paywad - 24 tonnes engines = 180 tonnes remaining. Three tonnes (conservatively) for decouplers, FINS, and nosecones = 177 tonnes left, divide that into seven stacks for fuel = 25.28 tonnes per stack. You could do that with an X200-32 and partially drained X200-16 tank.

I'm using Mechjeb.

Makes absolutely no lick of difference. Set your Mechjeb up such that you begin turning at 5 kilometers and you're at 45 degrees at 15,000 kilometers. If you've added fins and still have problems, try adding a Large ASAS module or two. And MOAR FINS. Finny finny fins...might suggest fins on the core too, not just the boosters; no telling where you'll be when Mechjeb decides to cut loose that last booster pair. If you're high enough, great; if not, you'll want them.

Edited June 9, 2015 by capi3101

[Warzouz]

I've built some SSTO rockets : http://forum.kerbalspaceprogram.com/threads/123195-Cygnus-family-Recoverable-SSTO-Rockets-from-12-to-236-tons

Try the M3-39 model. It can lift 39T to LKO. You just have to add a probe core and cone on top of your orange tank. If you want to add fairing, small transfert stage and or RCS, you could use the M4-52 model. All those rockets are reusable so you get a very cheap price per ton in LKO.

Before those test payload, I used orange tanks. The biggest rocket stage was tested with a 5 orange tank stack and a nose cone...

If you want to build it yourself (which is the point of the game, isn't it ?)

- Add wings at the bottom of your rockets. If it flips, change to bigger wings.

- Check your upper stage still have fins after staging, at least up to 30/35km

- Don't put too high TWR (1.4 - 1.7 is good)

- Streamline your payload

- Beware of SAS : do it manually until 40km.

- Start turning at 60m/s

- You can reduce throttle, it helps.

- You can add winglets in the middle of the rocket, it helps to control (far from necessary)

[Snark]

And while you're adding fins... consider choosing AV-R8 Winglets (or some other active control surface).

Not only do they work as fins, but they have active control and will be able to contribute active steering to SAS. One steerable fin can get you as much bang for your buck as two or three fixed fins.

[Warzouz]

I'm using Mechjeb.

Well, don't. Autopilots and SAS do some harsh maneuvers which aren't compatible with the new aero... You can activate MJ when you've crossed 40k.

I was using MJ a lot for ascent, now I'm doing it myself. Safer and cheaper. I use MJ a lot for other thing though, it's a great mod.

At least check you have the latest release.

[oglommi]

just pump some fuel from the bottom tanks to the top tanks during ascend to keep you CM high. Alt left click 2 different tanks lets you move fuel.

[Delta_scientist]

What else are you dragging up there? Your payload should consist of the tank, a probe core, and a docking port.

This but I add monopropellent fuel (very small tanks) and monopropellent

[Michael R]

Maybe you're over complicating your design? I just tested this payload:

RCLo1 probe (heaviest core)

Z4K battery (heaviest battery)

FL-R1 RCS tank (heaviest RCS tank)

Rockomax Jumbo 64

8 x RV 105 RCS thruster blocks

6 x OX-STAT solar panels

Total overkill as far as RCS and electricity. Weighs 40.5t.

I put that onto this 9 part rocket:

Rockomax decoupler

Kerbodyne S3-7200 tank

Kerbodyne S3-14400 tank

Kerbodyne S3-14400 tank

Mammoth engine - 4 Delta-Deluxe Winglets

Set mechjeb ascent to 250KM, automatic altitude turn, 39.5% turn shape. Engage autopilot, hit space, and fly to orbit with 30 m/s dV left (plus another 180 dV in RCS)

Sure, it weights 259.1t, but is that really a problem? BTW, this configuration starts with 3453 atmo dV, 3687 vac dV. You don't need 4.5k dV.

Or try this two stage, 10 part rocket, and end up with 240 dV:

Rockomax decoupler

Kerbodyne S3-14400 tank

Rhino engine

TR-38-D decoupler

Kerbodyne S3-14400 tank

Mammoth engine - 4 Delta-Deluxe Winglets

Edited June 9, 2015 by Michael R

[Delta_scientist]

Seems nice, but I lack the science to unock those mammoth and rhino engines.

[capi3101]

Seems nice, but I lack the science to unock those mammoth and rhino engines.

What kind of engine tech do you have available? That would help us give you better answers...for example, could you do the Mainsail/Skipper setup I suggested earlier today?

[Delta_scientist]

I can build up everything (except Kerbodyne S3-14400 tank (but chance this for 2xKerbodyne S3-7200 tank I guess) and the Mammoth/Rhino engine)

I have been successful been to the Mun and Minmus.

[Finndibaenn]

hi,

just a stupid question ... do you want only the tank ? or do you want it full ? If you empty it before launching, it's ll only weigh 6 T instead of 36, and that will be a lot easier ! Might be an easy solution if you have a minmus/mun mining op. and even if you want your tank to go to minmus by itself 1500 m/s dV should be ample, and that would not require a full tank.

[Delta_scientist]

Hi thanks for your reply. I ment to build a space/refuelinging station outside Kerbin in a High orbit so I can plan planet interstellar missions.

[Kryxal]

Getting an orange tank up is actually fairly easy ... under it, put two orange tanks on a Mainsail, then four orange tanks around that with Skippers in asparagus configuration, some fins (you don't need control surfaces, you have enough with the gimbal of the Mainsail), a few struts and you're there. I'd suggest locking the gimbals on the Skippers. I tossed together a quick design for 93k, yours may be a bit more or less, and TWR is 1.3 or greater the whole way up.

Actually, for a craft like that, MechJeb can do a good job on the ascent. Start your gravity turn at just over 1 km up, turn coefficient of .5, limit AoA to 5 degrees and acceleration to 20 m/s, and you're pretty much there.

[Michael R]

Kryxal's answer works fine. Nevertheless, I decided to try to find a different way to do it, and here's what I came up with (I believe you said you have all these parts):

Rockomax decoupler

Advanced Reaction Wheel

Kerbodyne S3-7200

Kerbodyne S3-7200

Mainsail

To each side of the bottom tank, attach TT-70 radial decoupler, one S3-7200 and a Mainsail, and fuel lines from boosters to center. Orient the boosters so they're on the side after the turn, not top and bottom.

That's it. No nose cones, no fins, no control surfaces. 2 stages. Mechjeb was able to get that to a 250kM Orbit with 30 dV to spare. 13 parts under your payload, cost is 82,800, weight with payload is just over 218t.

I use the Auto Altitude Turn setting, and pull the altitude slider all the way to the left, so it starts as soon as possible. I also never use the AoA limit setting. It seems to do unpredictable things (at least unpredictable to me) and my rockets don't approach 5 degrees AoA until they're at high altitude anyway. But, as you can see, there are very different approaches to successfully designing and flying rockets to accomplish the same goals. If you still are having difficulty, let us see what you're trying to fly.

[bigcalm]

I don't trust MechJeb to do the full launch from Kerbin - it rarely works except with small uncomplicated vessels. That said, MechJeb *does help immensely* but not using the "launch" thing - use Smart-ASS with "Surf-Up" and "Kill-Rot".

If stability is an issue, there's several fixes.

1) Add a reaction wheel preferably somewhere near to the centre of mass of your craft. This will need power so some batteries on your craft is recommended.

2) More fins.

3) More struts.

Below is my refueller for refuelling stuff in low Kerbin orbit. The payload at the top is 61.7 tons - in other words, more than sufficient for launching a full orange tank (weight: 36t). It's parallel staged (http://wiki.kerbalspaceprogram.com/wiki/Stage#Parallel_Staging) rather than asparagus, so could be made more efficient. It's also relatively easy to get into orbit and is pretty stable throughout.

Launch intructions: MechJeb-Smart-ASS-Surf-Up-Fire. This should take you directly up the first 10k and MechJeb will handle pointing you in the right direction. Immediately after you make the solid booster fall off, change Smart-ASS to "Kill Rot". It's then fairly simple to get into any orbit you like using the standard gravity turn. After rendezvous and docking with a craft at a 200km orbit I have around 400ms ^v remaining. Costs 140k a pop though!

[Reactordrone]

This is a relatively cheap, all skipper solution. Booster stages feed into the core and are jettisoned together.

[rkman]

Well, don't. Autopilots and SAS do some harsh maneuvers which aren't compatible with the new aero...

MJ is very well capable of performing gentle maneuvers.

Set it up to start turning at ~90m/s, limit AoA to some 4 or 5 degrees, limit thrust to 18 to 19m/s until ~20km alt. Set turn shape to about 55 to 60%.

Above ~40km use "final flight path angle" and throttle to keep apoapsis at about 1 minute.

And for a large rocket it helps to set "Tf max" (in "Attitude Adjustment") to about 0.7 to 0.9 (Tf auto-tuning "on").

[Warzouz]

I had some mishaps with rockets I easily fly to orbit without SAS.

[Delta_scientist]

http://img.photobucket.com/albums/v499/swampmonster/Kerbal%20space%20program/orange%20tank%20lifter_zpsbjpr0vbx.jpg

This is a relatively cheap, all skipper solution. Booster stages feed into the core and are jettisoned together.

Used this rocket and came quite far. I kinda dont wanna waste any fuel on my refueling tank, but I think that is inevitable.

- - - Updated - - -

Kryxal's answer works fine. Nevertheless, I decided to try to find a different way to do it, and here's what I came up with (I believe you said you have all these parts):

Rockomax decoupler

Advanced Reaction Wheel

Kerbodyne S3-7200

Kerbodyne S3-7200

Mainsail

To each side of the bottom tank, attach TT-70 radial decoupler, one S3-7200 and a Mainsail, and fuel lines from boosters to center. Orient the boosters so they're on the side after the turn, not top and bottom.

That's it. No nose cones, no fins, no control surfaces. 2 stages. Mechjeb was able to get that to a 250kM Orbit with 30 dV to spare. 13 parts under your payload, cost is 82,800, weight with payload is just over 218t.

I use the Auto Altitude Turn setting, and pull the altitude slider all the way to the left, so it starts as soon as possible. I also never use the AoA limit setting. It seems to do unpredictable things (at least unpredictable to me) and my rockets don't approach 5 degrees AoA until they're at high altitude anyway. But, as you can see, there are very different approaches to successfully designing and flying rockets to accomplish the same goals. If you still are having difficulty, let us see what you're trying to fly.

Somehow when I do this mechjeb screws over and wont even reach 250k orbit.... When I fly manually I wont reach it either.. Did you use any fuel from the refueling tank?

[StormKat]

Try my fuel pod: http://kerbalx.com/StormKat/SK-Fuel-Pod

Change it up. Hopefully it will give you some ideas.

Doh! Nevermind, I didn't realize this was a career game.

[Michael R]

Somehow when I do this mechjeb screws over and wont even reach 250k orbit.... When I fly manually I wont reach it either.. Did you use any fuel from the refueling tank?

When you say Mechjeb screws over, do you mean it loses control on ascent? I didn't use any of the cargo fuel, but I guess I might not have mentioned that I used some smaller parts on the fuel drone. OKTO2 probe, Z-200 battery, FL-R25 RCS tank, giving 64.2 ms dV. My cargo was 37.6t. By using the small probe and moving the reaction wheels down to the middle of the rocket, I get better control and shed some weight. You don't need reaction wheels on the fuel drone because of the RCS.

I just rebuild this and tried it, and it makes it to orbit. But, since the point of this vehicle is to send fuel to a station, you probably want to throw in a little more fuel in case you don't perfectly burn to orbital rendezvous. I just tested again (adding a docking port on top this time so it can actually serve its purpose) adding a KS-3600 tank on top of each side booster KS-7200 for a little extra fuel. This gets me to orbit with 437 dV left for rendezvous, and 63.3 RCS dV for docking. There's plenty of room to optimize this design.

My Mechjeb settings: 250 km, no limit acceleration, no corrective steering, auto turn set to lowest altitude, final flight angle 0, turn shape 40. Pretty much all default settings. The only mods that I can think might have any effect are Kerbal Joint Reinforcement and Stock Bug Fix Modules, and I doubt they have much effect on this case.

- - - Updated - - -

Try my fuel pod: http://kerbalx.com/StormKat/SK-Fuel-Pod

Change it up. Hopefully it will give you some ideas.

Doh! Nevermind, I didn't realize this was a career game.

It looks like your docked fuel pod adds only 3 parts to the station and doesn't tie up a docking port. I like that.

[Delta_scientist]

When you say Mechjeb screws over, do you mean it loses control on ascent? I didn't use any of the cargo fuel, but I guess I might not have mentioned that I used some smaller parts on the fuel drone. OKTO2 probe, Z-200 battery, FL-R25 RCS tank, giving 64.2 ms dV. My cargo was 37.6t. By using the small probe and moving the reaction wheels down to the middle of the rocket, I get better control and shed some weight. You don't need reaction wheels on the fuel drone because of the RCS.

I just rebuild this and tried it, and it makes it to orbit. But, since the point of this vehicle is to send fuel to a station, you probably want to throw in a little more fuel in case you don't perfectly burn to orbital rendezvous. I just tested again (adding a docking port on top this time so it can actually serve its purpose) adding a KS-3600 tank on top of each side booster KS-7200 for a little extra fuel. This gets me to orbit with 437 dV left for rendezvous, and 63.3 RCS dV for docking. There's plenty of room to optimize this design.

My Mechjeb settings: 250 km, no limit acceleration, no corrective steering, auto turn set to lowest altitude, final flight angle 0, turn shape 40. Pretty much all default settings. The only mods that I can think might have any effect are Kerbal Joint Reinforcement and Stock Bug Fix Modules, and I doubt they have much effect on this case.

- - - Updated - - -

It looks like your docked fuel pod adds only 3 parts to the station and doesn't tie up a docking port. I like that.

Gonna try t his, since it looks close to my fuel tank with the part added! Thanks for your help.