What are the stats of the Vernor engine?

[Sharpy]

I've been making a very light lander for Minmus, and as I realized I will need RCS anyway, and absolute minimum of engines and any other extra weight, why not forfeit standard engines altogether and just go with Vernor engines only?

But I'd like to know how much dV I have, etc, and the stats on the RCS thruster are far more scarce than what normal engines get. So, how does Vernor compare to, say, Ant?

Edited July 8, 2015 by Sharpy

[Feradose]

Well, Vernor has a lot of more thrust (12kN thrust on Vernor) than Ant. And I think it has a vacuum Isp of 240. It makes a good... vernor engine.

[Xannari Ferrows]

You need the mass of your lander with and without fuel to figure that out. If you know those, it should be easy to find your Delta-V.

[BlkBltChemie]

The Vernor engine actually runs on liquid fuel and oxidizer not RCS monopropellant. I think a lot of people actually use it on launch stages when reaction wheels/regular RCS thrusters are not sufficient.

You might want to check out the O-10 "Puff" monopropellant engine instead. Here's a link back to when they were first added http://forum.kerbalspaceprogram.com/threads/86152-O-10-Monopropellant-Engine-Vernor-LFO-RCS-Thruster, but I am not sure if this information still applies. If you do go with this engine, bear in mind that it is radially attached so you will need at least two.

[rofltehcat]

Two problems I see with it:

1. To fly around you'll have to manually fire the RCS controls nonstop. Can't just set it to thrust and do other stuff meanwhile.

2. If the lander is light enough to completely maneuvre with 1-2 Vernor engines then also having Vernor engines for RCS (I assume for docking?) means the TWR will be far too high to make it a feasible docking aid.

Suggestions: Go with monoprop engines. Or go with a normal LFO + monoprop. Or stick 1-2 Ants on there for normal flight (small nose cones make good attachment points; or use the radial ones if you have them unlocked yet). If you really want to dock in orbit but worry about the monoprop fuel weight etc. why not stick the Vernor engines on the transfer stage instead (will be heavy enough not to be overpowered by Vernors, won't have to take the fuel down to the surface)?

[Sharpy]

Thanks to Vernor using LF+Ox I'm getting a far better delta-V than with monoprop engines - seriously, have you seen ISp of these? It's pathetic! Plus if I used Ant, the lander would need both monoprop and LF+Ox tanks.

For docking, there's the precision mode (capslock). And just three days ago I did use Vernor-based RCS for orbital capture, plane alignment, rendezvous and docking to a station.

That was quite a story actually. A typical Kerbal SNAFU - contract to build a Minmus station with a lab - a station I just needed. Except I didn't have access to any sensible solar panels, just the smallest. And not enough money to start an expedition that would earn me that much science. The contract for the lab would let me get enough money to get the science for the panels, except then the lab is already in Minmus orbit... well, a quick decision: deploy the lab now, with a few token single panels, develop gigantors and send them as a module for the lab.

The plan went without a hitch until the actual delivery: the module consisted of a small fuel tank (used more as a structural element than a tank), with a docking port, four gigantors and a few Vernor engines. Oh, and a probe core plus a small battery. This attached by a decoupler to a transfer stage, a large tank and a good-ISp engine.

The launch didn't go as intended. The rocket refused to lean into gravity turn, I came out with a very high apoapsis and no horizontal speed to speak of. Most of transfer stage fuel went into getting the orbital speed.

Well, entering Minmus SOI I noticed I won't have enough fuel to meet up with the station. A quick decision: dump the heavy transfer stage, transfer all the remaining fuel into the small tank and use RCS for the rest of the travel. Orbit+plane alignment (the station was in polar orbit), then rendez-vous, then the approach, then docking - It went... surprisingly smoothly. I docked with 10 units of fuel left.

Seriously, the fact you need to hold a key down, instead of pushing Z to start the engine and X to stop it, for stuff like that is actually better. Lack of throttle doesn't hurt much - the two settings (standard and precision) are perfectly sufficient. If anything, I might be worried the engines are too strong for Minmus - seriously, on Kerbin I was able to hover my lander off the landing strip, tip it over, and then set it back upright!