Vehicle Construction in Space

[wolverine79936]

Hello, everyone. I have successfully launched a Mir style satellite, a science satellite and several communications satellites. Now, I'm finally getting ready to start working on my space station - no, I haven't left Kirbal orbit yet, wanna get to the moon soon. Anyway, I was wondering, after I finish construction of my space station, is it possible to build a rocket at the space station so that I don't have to deal with terrestrial-based fuel costs and just launch from space? Any help would be greatly appreciated.

Perhaps I could even just build a space shuttle with some extra fuel and a rover in the hanger for a Mun expedition at the space station...? Thanks.

[Jimbimbibble]

It all depends what you want to build. It's possible to do orbital construction like that but not always necessary or practical. I think that unless you want to build a massive ship, it's better to launch in one piece and refuel in orbit if necessary.

[moogoob]

You're talking about one of two things.

1. Assemble in multiple parts a craft of some sort in orbit. That's doable, but your biggest limitation's gonna be the wobblyness of the docking ports needed to assemble in orbit.

2. Launch a full vehicle, then refuel at the station, using it to do mun missions then come back to the station, never returning to kerbin except through other craft. This is much easier and more practical - I have a station around Minmus for this very reason, the re-fueling of landers.

Are either of these any help?

[Uzric]

[...]is it possible to build a rocket at the space station so that I don't have to deal with terrestrial-based fuel costs and just launch from space?[...]

Extraplanetary Launchpads (MOD).

Edited December 13, 2014 by Uzric

[Starman4308]

There's no way to skip getting fuel to orbit. The Extraplanetary Launchpads mod might let you assemble craft in space (once you get suitable materials there), you can refuel in space by docking, and various mods allow ISRU (In Situ Resource Utilization, making fuel from stuff you find on planets or asteroid), but you cannot magic up rockets from the aether.

In any event, it is really not difficult to get to the Mun and back in 2-3 stages. Are you using sandbox or career/science? I'm testing out a slight modification to my first attempt at a "this is how you get to the Mun with barebones tech" rocket.

[Raptor9]

Just my technique...

First off, the only non-space station vessels I make that are big enough to require orbital assembly are interplanetary. It will depend on your specific ship design, but I can normally separate it into several modules joined by large (2.5m) docking ports. This is practical if your ship is of longer shape. If it's a wider design requiring you to place modules radially around the main module, it will start getting tricky with multiple docking ports and such. Anyway, after I have my ship assembled (all docked together), sometimes I will use the EVA-placeable struts from Kerbal Attachment System mod to reinforce certain key areas while in orbit. This helps with the wobble of your ship and it also adds to the realism of actually going out on EVA and assembling a craft in orbit.

The main consideration I have to make on how many modules I can separate it into is the weight of each section. Fewer modules means fewer launch vehicles, and less wobble of your finished ship, but those individual modules may be very heavy, requiring extremely robust launchers. If it's a heavy module and contains fuel, defuel it in the VAB and launch a fuel lifter later to fuel the ship after assembly is finished. Defueled modules are also easier to move/manipulate during docking.

It's all about cost vs benefit of your designs. It's why KSP is so fun. Hope this helps

EDIT: BTW, wolverine I noticed this was your first post. Welcome to the forums, and welcome to Kerbal Space Program.

Edited November 23, 2014 by Raptor9

[Wanderfound]

While there's no way to skip getting fuel to orbit, there is a way to do it on the cheap. A good spaceplane tanker can put up better than a Rockomax 64 per flight for less than √1/unit.

It's not necessary, but interplanetary is a lot easier if you can ditch the boosters, lift off with your transit stage and refuel it in orbit.

OTOH, as has already been mentioned, you can get to the Mun and back for about √25,000 using nothing more than the first couple of tech nodes.

[wolverine79936]

Thank you, very much, everyone. Now to get to work on my station. Hopefully I can actually make that work. Satellites are a peace of cake, but this will be my first time putting large things up there.

And I was not positive how refueling would work. Is it possible to do my secondary idea of refueling a shuttle up there and then using that to get to the moon and drop stuff off? Or is that totally impractical and I'm just dreaming Star Trek stuff now?

I prefer how the shuttle works versus the rockets, btw.

[Raptor9]

If you can think it up, try and figure it out. Very little is impossible in KSP.

[Starman4308]

Thank you, very much, everyone. Now to get to work on my station. Hopefully I can actually make that work. Satellites are a peace of cake, but this will be my first time putting large things up there.

And I was not positive how refueling would work. Is it possible to do my secondary idea of refueling a shuttle up there and then using that to get to the moon and drop stuff off? Or is that totally impractical and I'm just dreaming Star Trek stuff now?

I prefer how the shuttle works versus the rockets, btw.

You can refuel anywhere: your plan is possible, albeit hardly the most efficient way to do it. The primary issue is that space shuttles are a bad idea for space: the wings are dead mass when there's no atmosphere*. For efficiency, you want to use SSTO jet-powered spaceplanes to bring stuff up (particularly fuel and light payloads), but dump off the SSTO's payload in LKO and immediately return them. You might, say, bring a probe to orbit in a cargo bay, dump it off, and the probe will propel itself to its destination. If you really like space shuttles, go for it, but wings do you precisely 0 good in vacuum.

*It's also really difficult to stick a landing on airless worlds without placing dedicated VTOL engines, which are more dead mass for getting to and from that place.

[LordFerret]

Thank you, very much, everyone. Now to get to work on my station. Hopefully I can actually make that work. Satellites are a peace of cake, but this will be my first time putting large things up there.

And I was not positive how refueling would work. Is it possible to do my secondary idea of refueling a shuttle up there and then using that to get to the moon and drop stuff off? Or is that totally impractical and I'm just dreaming Star Trek stuff now?

I prefer how the shuttle works versus the rockets, btw.

Refueling: answer = yes. Using docking ports, you can dock two ships together and transfer almost anything - fuel, mono, xenon, and Kerbals too. If you're already putting satellites and such up into orbit, you're already half-way there to Mun and Minmus! Try building a simple autonomous probe and do a fly-by of Mun... don't forget to bring some science to do with you. Welcome to the forums.

[Wanderfound]

*It's also really difficult to stick a landing on airless worlds without placing dedicated VTOL engines, which are more dead mass for getting to and from that place.

Vernors make for very good zero-mass low-G VTOL engines:

[Raptor9]

To emphasize what the above posters have said, if you can build an SSTO to carry payloads to Kerbin orbit (or bring them back) the cost savings (in career mode of course) is worth the investment. I launched a SCANsat to survey Kerbin; used an SSTO to put it up there, and when it's done I'll bring it back, getting money back for the expensive probe core and scanning equipment. The only costs I incur are the fuel costs of the SSTO itself for two round-trips to space.

If you can build some small efficient trans-orbital ships to go to and from the Mun, and keep them in space by transferring Kerbals and science back and forth via SSTO's, all you really have to do is worry about how you can cheaply refuel them. That way you're not buying a new capsule and/or lander for every Mun/Minmus mission launch.