Building An Interplanetary Craft In Orbit

[DaveyLeo10]

I'm really interested in building an interplanetary craft in orbit using multiple launches and docking. I'd like it to be capable of going into deep space for a long term mission, for example going to Jool and being able to explore all it's moons in one long mission.

I've seen many YouTube videos but they all include ridiculous rocket designs to launch the whole thing in one go. While that's cool I'd prefer to use multiple launches and docking.

Does anyone have an design ideas or any tips or advice on how to build something like this.

Cheers!

[Red Iron Crown]

I would build the whole interplanetary ship in the VAB first. Put pairs of docking ports where the ship will be split into modules, and add an RCS system and probe core for docking to each module. Save the modules as subassemblies and build rockets under them. Launch, rendezvous, dock, repeat until all modules are reassembled in orbit.

[Jodo42]

If at all possible, use the 2.5m docking ports with appropriate strutting. They'll provide a more secure connection than the 1.25m ones will. Unless you're building a rather small/efficient IP ship.

I'd also strongly recommend building the entire ship in the VAB first. It lets you figure out exactly how you want to final ship to be configured, and will also alert you if your design in mind will have an off-center COM/T. If you have Kerbal Engineer Redux or Mechjeb it can let you see dV and TWR values as well, if you thrust limit engines you don't want considered to 0.

Generally my IP ships have either 2 or 3 sections. A 2-section ship either has the lander & return capsule as its first section, and the transfer vessel (fuel and engines) as the second, or a combined lander&science module as the first and the trasnfer as the second. If you're going for a thorough scientific survey or you want reusability the 3 section plan may be useful, which splits the lander and the science module.

[Vanamonde]

What do you think of mine? Load 'em up and fly 'em around.

[Slam_Jones]

This is the first one I built in orbit, using 2 launches. One for the science lab/control area, the other for the fuel tank/boosters. Connected with a Clamp-O-Tron Sr (the 2.5m one).

I've since realized that having boosters at the front means a lot less wobble while accelerating.

The first pic is a basic 2-launch one, the second pic is the same ship with three extra modules (two fuel and one lander). I like to make each pod with a probe core, battery, and rcs so they can be easily re-arranged as needed.

Edited April 6, 2015 by Slam_Jones

[juanml82]

Some thoughs

Why did you bother with wings on the orange tank?

Are those ion engines? They give you a lot of delta-v, but I wonder if you'll need days long burn times to move such a thing

Also, that's a lot of monopropellant you have there. I doubt you'll need as much. Radially mounting the white monopropellant tanks might work best.

[celem]

@OP: The advice to assemble the entire thing in the VAB is definately sound, it lets you get an overview of your completed ship and pick where the joins will be. You have a couple of options regarding how to actually plug the bits together in orbit. Some people will take the module they are installing, add a probe core, torque, power and rcs, then launch it, rendezvous with the assembly point and use the rcs to dock it to the ship under construction. The drawback to this method is that every module must have control, torque, rcs, power, all that stuff. Once your ship is assembled you then more than likely have to disable some rcs ports and torque rings to make the craft balanced. In the longrun this reduces the dV of the finished ship by a bit due to the dead-weight of unnecessary parts (not to mention escalating the part-count)

To avoid over-engineering each module like this you can either mount a small docking tug to it and then strap on the launcher, or make the upper-stage of the launcher into the tug. This lets you launch each module exactly as you want it to be on the finished ship, without superfluous control mechanisms. The beauty of this method for me is that you only need 1 tug, usually sent up with the second launch. Future launches can drop immobile/uncontrollable modules next to the assembly and the tug can then slot them in. It takes a little practice to design a tug suitable for installing a variety of modules, its RCS/torque needs to be well balanced with somewhat varying dimensions/masses of module.

As far as splitting it into reasonable modules I tend to launch the control unit first, this is capsules/pods/probe cores, batteries/solar and RCS tanks (since they ignore fuel-flow rules). I then add the fuel section, which isnt particularly easy to break up further if you are planning on dropping tankage during your mission (highly advised). Anything that is going to involve a fuel-line needs to be 1 module for instance, since you cant set these up after the VAB, likewise anything on decouplers. I then usually launch the drive section last since engines are massy (though compact). If your craft is to carry landers, satellites, anything like this then these can be plugged into their docking ports once everything else is assembled. Remember to leave a port free if you need to refuel any of the tanks in low kerbin orbit, i usually refuel through the nose where my lander will ultimately sit. Dont be scared to launch empty/part-empty fuel tanks if the mass of a module is getting too much for your launch vehicles.

@juanml82: Those wings are probably cosmetic, they are well overblown even assuming he has FAR and might need aerodynamic stability at some point. They look pretty pimp, so I think we'll let him off. If you look really close, I suspect he has landing gear mounted on the end of each fin, which in that case is designed to clear the mainsail and let him land the mothership. His Ions are probably meant for fine-tuning, you are quite right in assuming day-long burns. The mainsail on the back of that ship will be too overpowered to fine-tune distant intercepts.

The RCS is probably so that the individual modules of his ship can undock and rearrange themselves, if you look carefully you realise every independant section has its own RCS fuel/ports, probe core and Torque. Finally, RCS is oft-overlooked as an actual propulsion method. With the number of ports on that thing he can thrust harder with RCS than the Ions and it becomes a third propulsion option. (Never forget that 'h' turns your RCS into an engine)

Edited April 6, 2015 by celem

[DaveyLeo10]

Thanks for your advice! Designing it in the VAB is a really good shout. Having rockets at the front of the craft isn't something I had considered either!

Is there no way to add struts via EVA to increase the structural strength of the craft?

[Red Iron Crown]

Is there no way to add struts via EVA to increase the structural strength of the craft?

Not in stock. There are mods that add that functionality, KAS is popular for it.

[EtherDragon]

I have done this before on an old Let's Play (0.24?) anyway, it was really fun to build the craft in stages by docking modules together.

The first module to go was the engine cluster. It was first because the engines could not have any stages below them - this module was flown up "backwards" that is, engines facing forward and placed into a 100x100 parking orbit. It came with a pair of LV-Ns for deep space efficiency and a pair of LV-T30s for critical maneuvers where higher TWR was needed.

The second module docked to the first was the fuel module. It had a lot of extra fuel tanks which could be staged off radially - feeding into a central fuel tank to fuel the core engines.

The third module was the science kit, it was a central section with all the science instruments that I wanted to bring along, and a handful of probes as well.

Lastly the cockpit flew up with the crew, could position and dock itself (had RCS) and connected to the mother-ship. Then we were ready to depart for Jool!

The real trick, on such a craft is to allow for a single central control authority. Like one reaction wheel at the center of mass. Each module may have its own control mechanism, but that needs to be disabled in favor of the central one.

Another idea is to have each of the modules be kinda dumb - no probe core or SAS - and use a reusable tug to connect all the modules.

Also, since all the module will be docked together, there will be some stretch and wiggle - make sure you don't have too much thrust, or the thing will be really unruly to pilot! You can improve this by launching the engine and fuel core all in one go, but that will be a heavy payload - probably heavier than all the rest of the ship put together.

[Axelord FTW]

I used to build huge ships either in orbit (or before I switched to FAR/Career was a thing on the ground) but I eventually got tired of playing a Powerpoint game so I switched to multiple ship per missions.

For example,

1: Crew + Science Lab section ship*

2: Light lander + Probes ship

3: Heavy lander (for tylo or multiple landings) ship

4: Engineering section (KAS stuff, more fuel, RemoteTech long range antenna) ship.

(* if I run something like Near Future Technologies, this part will usually house the main reactor. Otherwise, the engineering section might. Everything else will usually run off of solar panels)

I'd wait for my transfer window and rapidly get everything on the way to jool.

Its technically cheaper to do the transfer off a single engine section comparatively but I think it's less of a hassle. Part count can then be lowered further by feeding Jool some of the engine stacks from each sections if you don't intend to bring them back (I never do). You also don't have to deal with docking port Sr (and their weight) since any sort of docking you will do will not have to handle any maneuvers or thrust and subsequent wobble. In fact, I've done a mission without any docking port by using KAS for fuel and science transfer.

[EBAO]

I have a large space station with a central core, a forward command bridge, and aft engine bay with 3 nukes. Around the core I have several docking ports in groups of 4. I play with the space station mod, flight engineer, and others. The station can make trips to Mun and Minmus, but I always must balance the CG first.

Here is my trick:

Flight engineer redux will give engine gimbal vector info. (If trying to fight an off center CG)

I have 4 solar arrays in 4 directions, each has a small fuel tank at the end. By transferring fuel to one of the tanks I can shift the CG to get the gimbal vector value close to zero. This allows my 150ton station to fly straight without too much RCS draw. (Frame rate is another issue)

Second tip: make a detachable small root part. This allows contracts with new requirements able to use the old station. Need a station in Minmus orbit for 11 kerbals, a lab, power, docking... I have all that already. I just send up a new Resupply ship with a fresh root part and detach the original and leave in LKO. 150 tons to Minmus here we come! (After 4 or 5 periapsis kicks! )

[William Nye]

You can also use some mods which let you use your kerbals to make struts. This will help with orbital construction and the such. I don't know the name of the mod though- I know it's not KAS- maybe KIS or sommin'?

[Red Iron Crown]

You can also use some mods which let you use your kerbals to make struts. This will help with orbital construction and the such. I don't know the name of the mod though- I know it's not KAS- maybe KIS or sommin'?

KAS definitely allows kerbals to create struts.

[HafCoJoe]

I made this video about a month ago for my interplanetary mission to Duna. It may have what you're looking for .

[Majorjim!]

This might give you some ideas too:

Javascript is disabled. View full album

MJ

[DaveyLeo10]

I love the gliders!

[Wanderfound]

I'm really interested in building an interplanetary craft in orbit using multiple launches and docking. I'd like it to be capable of going into deep space for a long term mission, for example going to Jool and being able to explore all it's moons in one long mission.

I've seen many YouTube videos but they all include ridiculous rocket designs to launch the whole thing in one go. While that's cool I'd prefer to use multiple launches and docking.

Does anyone have an design ideas or any tips or advice on how to build something like this.

The main problem with orbital assembly for interplanetary craft is ending up with an overly wobbly structure that is a nightmare to fly. There are a few things that help with this:

* Keep the structure linear and symmetrical.

* Snr Clamp-o-trons are your friend.

* Pull, don't push.

A demonstration of possibilities:

Javascript is disabled. View full album

Craft files at https://www.dropbox.com/s/8xexx9dpsewt719/Kerbodyne%20Expedition%20Leader.craft?dl=0 & https://www.dropbox.com/s/7qeyivobrr23jho/Kerbodyne%20Expedition%20LabHab.craft?dl=0 & https://www.dropbox.com/s/no7sjpxmgxh6vd5/Kerbodyne%20Expedition%20Fuel%20Module.craft?dl=0

[Warzouz]

For space station, why building around Kerbin then go to target instead of build it at target ?

I recently finished a Jool mission (basically a space station with 5 SSTO landers (+1 staged lander), return ship and 6 orange tanks and RCS which was assembled orbiting Laythe.

All 13 parts where sent every 20 minutes. They arrived within 400 days time span, which gave me plenty of time to do the double aerobrake (Jool +° Laythe).

Finally I have a 400T space station on a 500km Laythe Orbit. The mission is now finished. I managed to get 41000 science points by 2 landings on each moons and some flyby. The crew went back to Kerbin. The station is now uninhabited.