Nucular Issues

[Bakkerbaard]

Hello! I've got yet more questions.

I'm designing a long distance spaceship. It's gonna be way heavier than it probably needs to because I'm more concerned with looks, so I figured I'd give that fancy StarLifter Nuclear Reactor a whirl, but it turns out that I have no clue how to work it. So... how does it work? I seem to have no engines that work on depleted fuel and my best guess is that DF is a side effect of the reactor generating the electricity that is needed to power the atomic or nuclear engines. However, it seems that all the engines I have require LH2 on top of that.

My goal is to have a self sufficient ship and I'm reasonably sure I have all the puzzle pieces in my parts list, but I can't figure out how they all go together, especially since I mostly have no clue as to how a lot of these parts work. I think it's possible to generate some kind of go-juice if I run dry in the middle of The Void, but how... Am I making any sense with these questions?

The plan is to send it all up in parts, ofcourse, and since I'm still sandboxing funding is no issue.

I've done some light experimenting myself, but any conclusions I'd dare bring to space elude me and since I don't think NASA has just one engineer firing off rockets to see what they do, I'd figure I'd try some fellow rocket scientists too.

[Mark Kerbin]

Depleted fuel is a waste product made when firing the nuclear engines. Said engines also usually produce a kraken ton of heat, so bring radiators. Other than that, those parts sound modded so I can’t help without more info.

[Bakkerbaard]

Yeah, stock is rather outnumbered in my list.

[blakemw]

Even nuclear engines still need reaction mass to throw out the back of the ship, so that is why hydrogen is needed. The reactors do the throwing, by heating that reaction mass up (either heating it directly, or indirectly via electricity).

[Zhetaan]

@Bakkerbaard:

Depleted fuel can be reprocessed into usable fuel (with diminishing returns), thus saving somewhat on the extraordinary cost.  However, the reactor itself doesn't reprocess depleted fuel; that's a different part (from a different mod, I think).  Unpatched USI reactors also produce a bit of xenon as a byproduct, though if you have designs on using xenon to move a StarLifter-class freighter around, I suggest writing a will first:  your grandchildren may live long enough to complete the burn.  More practically, you can collect the xenon for use in small tenders or probes or return it to Kerbin for recovery, but that's not really a concern for a sandbox player.  In any case, the reactor dumps the excess if you don't have storage, so you don't need to worry about everything shutting down because you didn't bring enough waste containers.

USI tends to avoid breaking the laws of thermodynamics; if you want to go from Point A to Point A+dA, let alone Point B, then you need to expend propellant mass.  What this means is that while you are free to include resource harvesters in your design, there's no such thing as a 100% self-sufficient vessel using USI parts.  It can be self-sufficient when provided with an ample supply of asteroids, it can be self-sufficient on a planetary surface (maybe--the random number generator may make it impossible on some planets), but it cannot be self-sufficient in the purest sense unless it is a solar-electric rover.

The large StarLifter engines that come with Freight Transport Technologies run on LH2 instead of LF, so it's not quite like the stock LV-N.  On the other hand, FTT includes dedicated LH2 tankage, so you aren't stuck using either large LFO tanks with the O removed or Mark 3 aeroplane LF tanks as often happens in stock; the tanks you need are provided in the sizes you will likely want.  These engines do not require electricity to function;  you don't need a reactor for them.

The reason for the large reactor is to power the 5-metre reaction wheel and Karborundum-based torch drives, if you have them, because those do use immense amounts of electricity.  You do need an electrical supply for the LH2 tanks if you have Cryo Tanks installed:  without electricity to run the cooling unit, the tanks will suffer from boiloff (a leak by another name), but the power requirement for that is not large.

[Bakkerbaard]

5 hours ago, Zhetaan said:

there's no such thing as a 100% self-sufficient vessel

I expected as much. Laws of physics simply prevent that. My initial plan did in fact include two dropships to harvest resources from whatever's nearby (relatively speaking), but without actually landing somewhere I'm limited to atmospheric gases and aside from the lacking thrust they provide planning for things I have only very little incling about would make the dropships the size of the mothership, which didn't seem like a very good idea.

5 hours ago, Zhetaan said:

unless it is a solar-electric rover.

This is one idea I toyed with, but in a spaceship obviously, since sunlight is pretty abundant. Aside from the wrong side of a planet, one could get some anywhere. But within the mods I have installed (mostly mods that are probably-not-but-at-least-seem-realistic category) there's nothing that lets me convert electricity into usable propellant without at least one other ingredient.

5 hours ago, Zhetaan said:

The large StarLifter engines that come with Freight Transport Technologies run on LH2 instead of LF, so it's not quite like the stock LV-N.

It doesn't need to be a StarLifter class ship, per se. This particular question just came up because the reactor seemed like a pretty powerful tool. 

I'm thinking I'll just have to stick on a couple of converters and squeeze LH2 out of whatever I can get my hands on then.

[Zhetaan]

15 hours ago, Bakkerbaard said:

ut without actually landing somewhere I'm limited to atmospheric gases and aside from the lacking thrust they provide planning for things I have only very little incling about would make the dropships the size of the mothership, which didn't seem like a very good idea.

Karbonite, should you decide to use it, includes an atmospheric scoop (and an ocean pump, and a mini-drill, and ...) that also functions in specific 'belts' in the space near some planets.  If you place your mothership in orbit with a few of these scoops, then you can maintain fuel independence without needing to land.  Karbonite is more plentiful in Jool's atmosphere and a couple of other places, but to get it, you need a vessel that can withstand entry heating.  If you want to play with Karborundum, then close-in harvesting of a solar belt with a large collector is one way to obtain the stuff.  (It was once obtainable in such a belt that was located only 2,000 m--that's metres, not kilometres--above the surface of the sun.  Then Squad introduced thermal radiation; I understand that the belt is much farther out now.)

15 hours ago, Bakkerbaard said:

But within the mods I have installed (mostly mods that are probably-not-but-at-least-seem-realistic category) there's nothing that lets me convert electricity into usable propellant without at least one other ingredient.

There is a light-sail mod out there, though I do not know whether it has been updated (or even whether it can work in the current version of KSP).  That would be your best option for propellant-less transportation in space.  Even the warp drive mods tend to the idea that motion does not come from nothing.

Edited May 31, 2018 by Zhetaan

[Daniel Prates]

Would you be talking about the "near future elecrical" mod reactors? If so,  they use a nuclear fuel and generate a waste resource in the process, which is not recyclable. But  both can be transfered to-and-from a separate tank,  like other resources. So you can bring along the reactor and an extra batch of nuclear fuel. It is a very heavy set of parts though. I only use them in stations and outposts,  ships tend to be impractical with them (in a hard difficulty,  no revert no quicksave career game that is).

Edited May 31, 2018 by Daniel Prates

[Bakkerbaard]

7 hours ago, Zhetaan said:

Even the warp drive mods tend to the idea that motion does not come from nothing.

I'm not sure if I have been implying that this is what I'm after, so to be sure: That's one of nature's laws I'm not looking to break. I'm just looking for ways to refuel without having to do the dangerous stuff I'm not really good at. Like landing on planets. Especially planets I'm not familiar with. Even with MechJeb I'm wholly capable of driving a dropship into the ground. ;o)

6 hours ago, Daniel Prates said:

Would you be talking about the "near future elecrical" mod reactors?

I might be... 

I've got all but one of the NearFuture mods, but I grabbed way in the beginning of moving to PC for the game, so I was just grabbing stuff that looked cool and now I have I have a lot of stuff that I'm not sure of where it came from. But, chances are, it's NearFuture.

Either way, I'm probably going to bin the current starship design and start from scratch. I'm thinking it'll be smarter (and cooler) to hook up a bunch of smaller ships to form one grand vessel ready for any eventuality. To be honest, I'm thinking planning this trip is more fun than undertaking it anyway. ;o)

Edited May 31, 2018 by Bakkerbaard

[Daniel Prates]

1 hour ago, Bakkerbaard said:

To be honest, I'm thinking planning this trip is more fun than undertaking it anyway

That's ksp all over!

[Vanamonde]

Modding question moved to the modding subforum.