Best engine for a huge ship?

[KerbalKid]

What is the best engine to perform an interplanetary transfer with a big ship that dosen't take

30 minutes. Were talking a ship over 100 tons....

[TheEpicSquared]

Well, considering you don't want 30 minute burns, the nuke probably isn't the best way to go. Maybe a Skipper or two? They have an acceptable vacuum Isp.

[Streetwind]

If you want massive amounts of thrust in space, the KR-2L "Rhino" is pretty hard to beat IMHO. Isp almost like a Terrier, but more thrust than a Mainsail.

[problemecium]

I'd recommend getting used to long ejection burns and design the ship to not spontaneously disassemble at 4x physics warp.

[DrLicor]

I prefer ISP over burntime, normally I use persistent thrust, So I can throttle and timewarping  

[Hannu2]

Do you have part limitations? I use several LV-Ns. I try to get acceleration to about 2.5-3.5 m/s^2. It gives typical departure burns at about 10 minutes. About 4-6 LV-Ns per 100 t should give suitable thrust.

[eddiew]

Since you don't have to carry oxidiser for them, it quickly makes sense to use a pack of LV-Ns as your primary interplanetary engine, no matter what weight of ship you're shunting around. They're always going to be the most efficient engine and will keep your fuel mass down every time.

Personally I just add them until my TWR is ~0.4 or better.

[magnemoe]

4 hours ago, Hannu2 said:

Do you have part limitations? I use several LV-Ns. I try to get acceleration to about 2.5-3.5 m/s^2. It gives typical departure burns at about 10 minutes. About 4-6 LV-Ns per 100 t should give suitable thrust.

yes an 9 pack of LV-N below an MK3 tank works pretty well, benefit is that you save in fuel weight. 
Other option is the rhino, good vacuum performance and mainsail trust. 
100 ton payload, two large 3.75 meter tanks and rhino gives 2.5km/s, 4 minutes burn time and 0.75 in twr, total weight is 275 ton.
9 LV-N with an long MK3 tank gives 2.4 km/s, 12 minutes burn, 0.3 in twr and 185 ton total weight. 

it depend a lot where you are going / how much dV you need, an advanced option is an LV-N second stage and rhino first stage. 
 

[Streetwind]

16 minutes ago, eddiew said:

Since you don't have to carry oxidiser for them, it quickly makes sense to use a pack of LV-Ns as your primary interplanetary engine, no matter what weight of ship you're shunting around.

That's not really an advantage. In fact, it's a disadvantage, since it limits your part selection greatly, and most LF tanks don't even match the rockets in form factor and art style.

The thing that makes the LV-N's efficient is their Isp, not their fuel selection.

[stenole]

For anything below 0.3 TWR and larger than small, I would recommend LV-Ns (unless cost is a factor). Aerospikes and poodles work well if you need higher TWR in the 100t range. Rhinos are great for even more massive high thrust ships. Add as many engines as you need to get the appropriate TWR. 

Source:

http://meithan.net/KSP/engines/ (best KSP web tool in the universe)

 

[RoboRay]

10 hours ago, KerbalKid said:

What is the best engine to perform an interplanetary transfer with a big ship that dosen't take

30 minutes. Were talking a ship over 100 tons....

The bigger the better.  If you're concerned with burn-time instead of efficiency, thrust is all that matters.

[Guest]

Whatever engine you want is the best one.

[Aegolius13]

Rhino, if you are not inclined to put up with nukes.  It is designed to be a sustainer and vacuum engine for very large ships.

[DerekL1963]

9 hours ago, Streetwind said:

In fact, it's a disadvantage, since it limits your part selection greatly, and most LF tanks don't even match the rockets in form factor and art style.

That's what mods like Modular Fuel Tanks were invented for...

[Vanamonde]

This question about how to play the game has been moved to Gameplay Questions.