Preferred engine for a satellite?

[Invader Jim]

I typically use a terrier or spark on my satellites.  I saw a thread where someone suggested using RCS only for the final stage of a satellite.  It makes me curious how efficient that would be.  I need to build one and see what kind of DV I get.

What do you like to use for satellite propulsion?  I am especially interested in long range satellites.  I have no problem getting to the Mun, Minmus and Duna but really want to try some missions to other planets and their moons.  In addition to satellites I might do some probes.  I like the idea of landing and then not have to worry about ever leaving, especially for Eve.

 

[FancyMouse]

Depending on the size of the satellite, but most of my satellite use Ant. Efficient, enough, and when it comes to fine-tune the orbit, it's so handy.

[Hodari]

It depends a lot on the mass of your satellite and what you plan to do with it.  If you just want to make occasional adjustments to the orbit of a small satellite, RCS is perfect.  If you're going to another planet with it, terrier, nuclear engine, or ion engines could be good. 

[Empiro]

It depends on the mass of the satellite and the amount of delta-V you need after LKO. In general, the more delta-V you need and the heavier the satellite, the more the equation favors engines with the best ISP, even if they're heavier.

One of folks on the forum made a pretty nice tool for making this determination:

 

Edited April 15, 2016 by Empiro

[regex]

I prefer RCS for satellites, mainly because the control is generally finer than engines.  IIRC the isp of RCS is 240, which really isn't that good but they're so light I've never really had a problem.  Tsiolkovsky gives you the delta-V it provides.

I find RCS great, in fact, did the last part of this mission entirely on RCS:

 

Edited April 15, 2016 by regex

[wibou7]

Ion engines all the way. Satellite is really the use case for them, since they are typically very low weight.Sure they are a tad more expensive than liquid fuel engine but you get more delta-v that you will know what to do with.

Ion engine: never again will you wonder if you have enough dv to relocate (tm).

[Wemb]

The problem with small engines, even on small probes, is that while you can get huge amounts of dV, you may also have excessive burn times to get out of the Kerbal system due to a low TWR which can complicagte getting a good transfer to another body.

Typically a Spark engine is probably a decent compromise for a very small satellite. But as dV needs go up, you'll need to take more fuel, which means more mass and there super-efficient engines really come into their own.  You could also consider other options such as saddle tanks, and asparagus staging - their benefits aren't restricted to the launch.

Kudos to Empire for linking to that tool, I'd not seen it before - very nice.

Wemb

[FancyMouse]

1 hour ago, regex said:

I prefer RCS for satellites, mainly because the control is generally finer than engines.

Actually, in stock KSP, Ant engine can give finer control than RCS because you can use both thrust limiter and throttle which give two 5% multipliers, while RCS only has one multiplier of thrust limiter.

However, I admit it's kind of exploit. IRL (including RO) engine can't throttle all the way to 5%, which kills the only advantage of this approach over RCS.

[regex]

11 minutes ago, FancyMouse said:

Actually, in stock KSP, Ant engine can give finer control than RCS because you can use both thrust limiter and throttle which give two 5% multipliers, while RCS only has one multiplier of thrust limiter.

Well, if you're using the RCS 4-ways and point towards prograde you can make all sorts of orbital adjustments with the IJKLHN keys, so there's that.  Really up to personal preference.

[mrclucks]

I typically will use RCS for the final stage.  I get pretty good final control and the thrusters are relatively light.  I've never thought of using ion engines for probes but they do make alot of sense and the only problem would be power generation/battery life

[Pecan]

LV-1R - leaves room for a docking-port because, you know, no satellite left behind. (I am kidding, but the engines are still good)

Edited April 16, 2016 by Pecan