Favourite engine?

[Phoenix Aerospace]

LV-T45 all the way. It has fair ISP in both in a vacuum and atmosphere. Its TWR is terrific. The thrust vectoring helps for control on probed rockets, or for very heavy ones that lack RCS. It's useful for first stages on small rockets, upper stages on larger ones, and for liquid strap-ons. You can even cluster them with LV-T30s to make a composite engine more powerful (and many times more efficient) than a Mainsail. All hail the LV-T45!

[DisarmingBaton5]

Skipper, for the simple reason that it looks AMAZING

[SciMan]

So far, I have yet to build a satellite that lacks a combination of a PB-Ion engine, a Xenon tank, and 8 of the OX-4L 1x6 solar panels, even if the sat also has more conventional liquid bipropellant engines. Mostly, this is so I can adjust or maintain it's orbit without needing to worry about petty concerns like "running out of fuel"... simply because it takes so darned long to run out of fuel with one! For satellite station-keeping, the amount of Delta-V needed per maneuver is low, so the burn times rarely exceed a minute. Since a single ion engine at full throttle takes roughly 98 minutes to consume the fuel in a stock Xenon tank, the often-mentioned "long burn times = boring" complaint some players have with the stock ion engines actually works in my favor, because it doesn't matter that much if I accidentally leave the throttle up while I go to get a drink or something, the satellite won't have changed it's orbit much , and it won't have expended much fuel, so it's an easy enough thing to correct.

That being said, the Rockomax 24-77 small radial engines make EXCELLENT retro-rockets (exhaust pointed towards nose of ship) for ships that need to dock, but are heavy enough that turning them around to use the main engine takes too long. Essentially, I like to use them as "space brakes" instead of holding down the "N" key and using RCS monopropellant. An added bonus is that the 24-77 has a vacuum specific impulse either comparable to or slightly better than any RCS thruster.

I would have to give 1st place to the Rockomax 24-77 small radial, for being instrumental in preventing more than a few costly and time-consuming ship-to-ship collisions between parts OTHER than docking ports while building space stations.

A close 2nd place goes to the PB-ION, for it's "slow but steady" approach to providing large amounts of Delta-V to the many satellites I have in orbit, and it's tolerance of my not-so-unwavering attention to the state of the throttle.

Edited May 31, 2013 by SciMan

[CtrlAltEL1TE]

This suckers nuclear!

[Rainbowtrout]

The NERVA. Possibly the most useful thing ever to grace my laptop screen!

[Cordeos]

Mainsail! Most power is best power!

[Ford_Prefect]

For some irrational reason I love the 909. I think it's cute.

[Themohawkninja]

Either the Skipper, because I use it on my second stage of my rocket that helped construct a space station, interplanetary ship, and launch a massive satellite telescope into orbit, or the nuclear engine, because I use that for 99% of my interplanetary missions.

[way2smrt]

Lv45... Not always the best choice but a very well rounded engine, fits most situations. Also it let's me down the least and very Kraken proof.

[way2smrt]

For some irrational reason I love the 909. I think it's cute.

Same... Even though it normally let's me down from lack of power

[jpem]

Always use the Nerva.

[EvilotionCR2]

Favourite engine? CryEngine...Uh,that one,then my word goes to the mainsail,it's the main sail of every big rocket.

[Boffinbox]

i like the small 48-7s from KSPX, because when combined with a FL-T100 from KSPX (or a T-200) you have yourself a tiny retropack. yes, the lv-909 is more fuel efficient, but really, if you're doing your final retro burn to return to kerbin, fuel should not be an issue. the 48-7s is 1/5 of the weight of the 909

[rasheed]

Mainsail.

I am trying to make spaceplanes run purely on mainsails

[hazarada]

Skippers are my fav. They are great for keeping the item count down since they provide great thrust and don't need lots of struts like mainsails to keep them from ripping large crafts apart.

[leax256]

For some reason though, I never use the Mark 55. Not sure why.. maybe I find it too powerful for most practical applications as a radial.

booster for helping your rocket assend.

[SiliconPyro]

By simple merit of being the engine I've used to reach the most interesting places, I have to vote the Nerva. I certainly could have done it without, but I love that efficiency.