Interplanetary design for getting payload to another planet's orbits

[elkar]

Hello there,

well I've been so far flying around Kerbin quite a lot, so I know how to set up bases or space staions around minmus and Mun, now I wanted to edit my design for interplanetary flights. Of course, that meant to basically make bigget TUG and dock more payload behind it, since I figured, that you want to get as much cargo as possible in one go, because it takes a while to get there.

So what you see here is a TUG in front with 6000DV (in this setup) and basically whole space station i want to put around another planet behind it. It's storage tanks + habitat module + power module. All togeather about 40-45 tons.

But once I start my burn, it's pretty much screwed, even large docking ports cant hold it and it starts wobbling and shortly after it splits somewhere.

So I was wondering, is this design totally not usable for interplanetary flights, since I was using it for local ones for mun with smaller tug and smaller (one at the time payloads) and it worked perfectly.

So... any ideas?

[K^2]

Try disabling gimballs on all the engines.

[tek_604]

I assume it flew straight? Thats the problem I had.

Anyway, if its ripping itself apart, and you don't mind mods, try Quantum Struts. Even if you don't use the the Quantum Struts in orbit, it comes with some stronger "stock" struts.

[Sephta]

I don't see any struts - joints normally flex under acceleration, begin to swing and break eventually. If you can add struts in the Hangar, do so. If you assemble in orbit - I'd advise quantum struts or something similar.

[Stargate525]

Another way to do it is to not use full throttle or SAS. The former can tend to stress joints too much if your TtW is too high, and the latter has a tendency to induce some pretty bad snaking in long vessels.

[Francesco]

Another way to do it is to not use full throttle or SAS. The former can tend to stress joints too much if your TtW is too high, and the latter has a tendency to induce some pretty bad snaking in long vessels.

actually, SAS is fine and will help: it's ASAS which usually causes problems.

[Rhyunix]

The easiest way to get anything to another planet in one piece is to wait. Get a cuppa tea or something, cause if you plan it right, you can just burn for a long time before and after your maneuver node. That's what I'd do anyhow

[TimMartland]

Your design could probably be modified to work, but I think you should simplify it to 4 small nuclear engines on fl-t800 tanks around a x32 and x16 tank, with a lightweight pod/micro lander/probe on top. Not a very powerful design, but safe and lag free transport for small landers and probes. It can reach orbit over Duna and Eve and return and do one way trips to any of Jools moons. Hope I helped

[Merinsan]

I've got huge payloads to other planets, and the secret is to use nukes to do it. High efficiency with low thrust. The thing with the low thrust is you don't get much wobbling. Of course it can take a long time, the longest burn I had was 1hr. (fortunately I could use physics acceleration)

The other thing you can do is try pushing rather than pulling. Not sure if it'll make a big difference, but it wont hurt to try.

Edited May 29, 2013 by Merinsan

[elkar]

Apparently half the people didnt understand my question here.

That TUG ship was designed with 8x Nuclear engines with 800 ISP, 150KN each to be able to move with 150T payload from planet to planet.

Now, ive used to have quantum struts but with new docking ports i was hoping there wont be any need for those. But so far it seems that it's the way how to do it actually. I've tried to turn off asas of went for 30% throttle, problem is, it doesnt wobble anymore so those dockingports will break in straight line, so it's obvious that they just cannot hold such acceleration.

So... i guess those quantum struts will be best option to go for. I'm also trying to stay on low part count as you can see it's only 3 modules (120 parts) for the whole space station, nothing fancy, to have sem playable FPS.

Anyone knows how strong those quantum struts are? I mean i had them but is it the same like stock ones? 150?

[sturmstiger]

I haven't tugged 150ton payloads in space, so what I suggest is based on speculation rather than experience:

1. Have you tried slowly throttling up?

2. Have you tried pushing instead of towing?

[elkar]

I haven't tugged 150ton payloads in space, so what I suggest is based on speculation rather than experience:

1. Have you tried slowly throttling up?

2. Have you tried pushing instead of towing?

I havent tried to push.. i was told pulling or towing is much better. I used this design for Mun and Minmus but I was always carrying one cargo at the time. The first cargo i have now is that station it has 35t and i have scheduled the next one with 67t. So i need design that would be able to do that.

As I'm asking around on KLF it seems that it's actually better to make 3 trips instead of 1 and use simplier design for lag free and more controlable flight.. so

Edited May 29, 2013 by elkar

[Ferigad]

Dude, 8 Nuclear Engines for 40 tons of payload? Thats a little bit mutch to be honest. The reason why everybody thinks you dont use nuclear engines is, there are no nuclear engines on your screenshot. Only normal rocketthrusters. Or you use some kind of mod? You could also try to get the center of mass more in the middle be rearanging the fueltanks and get the thrusters more in the middle of your long structure. Could reduce the wabble.

But for a 40 tons payload, when i would play it stock, i wouldnt use not more then 2 nuclear engines max. Depending on where you would go i would only use between 1 or 2 large orange fueltanks. Should be enough to get 40 tons from A to B in the Kerbal Solarsystem without gettin to mutch wabble or ripping appart the pieces.

[elkar]

Those engines are from KSPX mod, same stats like stock nuclears but bigger, more powerful. I guess it's a overkill anyway since it was designed for 150t /3200DV. My previous tug for 30t payload for Kerbin system could landed 35t on mun using 4 of those engines...

But still I'm not sure if with small design I would be able to have more than one cargo on my back.. i mean more than 1 docking port. Because of course, as you add up cargos, modules or what ever, the first docking port is stressed more and more.. anyone have idea about how much can large stock docking port holds?

[Ferigad]

Well, the easyst way to get the stress out of the docking clamps would be to put the thruster at the backend of your Tug. I guess thats a reason why rocketage spaceship has there drives always at the back.

Dont forget, the gravity on mun isnt the same as the Kerbal Gravity. Mun gravity is 0.166 from Kerbal, dont wanna do complicate math so... if you calculcated the 30t payload at landing on a planet with 1G you can land, if you round it up to 0.2 at the mun gravity, a tottal mass of 150 tons with a drive that was made for 30t payload at Kerbal Gravitation.

I still think the wabble could be mutch better, even with this drive, if you turn the rockets around so that they are the back of the complete "ship" and not the front. It would also decrease the pressure at your clamps. My Stock-Spaceship has atm 130 tons of mass and uses 2 stock Nuclear Engines at the back. All clamps holding perfectly so far. No stress, no real wabbling.

Only long acceleration times. ^^

[Papa_Joe]

I understand you are asking a specific question.

The answer is, imho, no.

A pull configuration by it's very nature is limited in the mass it can carry based on the limitations of the docking ports. Could it be made to work? Of course, but why? A pull config is definitely more part intensive, for no gain.

A push configuration will allow you to concentrate your mass near the CoG, and compress the connections, as opposed to expanding the connections. Compression reduces flex to some degree, and the concentration of the mass near the CoG increases flight stability. Long ships will by nature flex a great deal, so reduce your height by building out. with drag, there are diminishing returns, so a balance should be struck for boost.

My heavy lifter pushes ~ 100 tons to a 600km orbit and then performs an orbital transfer to any planet desired. I'm not using nukes, and it is almost all stock, (MechJeb) Interplanetary station building simply demands it

The design could be improved to lift ~ 50 more tons without significant redesign.

the current end result is ~ 50 tons to station in orbit around another planet, using mainsail engines. Boost is 5 mainsails. Orbit insertion and Interplanetary transfer is accomplished with 1 mainsail. Orbital tug has 4 small engines for rendezvous & maneuvering, and lots of thruster fuel for tug operations and docking.

I typically add thrusters to my Station payload modules, as it makes docking more precise with heavy payloads, and provides for station maneuvering.

Push is definitely the way to go.

Edited May 29, 2013 by Papa_Joe