RCS choice

[Jestersage]

When should I go with the LOX vernor RCS instead of the monopropellant Anywhere RCS?

Yes, I know the short answer is "When the Craft is heavy", but How do I know it's heavy enough that it requires the vernor instead of spamming the Anywhere RCS?

[Foxster]

A better question would be: "When do I need RCS at all?". 

I never use RCS except for docking small craft.  

[Jestersage]

Docking and rotating

[Magzimum]

You know you need the Vernor Engines instead of the regular RCS:

• When you are too impatient for normal RCS
• When your craft is so large that part count becomes a major issue
• When you don't mind losing RCS control when you run out of fuel
• When "Moar Boosters" is your answer to speeding up your docking procedure

Some of those sound like material for a meme:

[Blaarkies]

Just look at the thrust values. Once the sum of RCS thrust values on one side is greater than that of a single Vernor, then it is time to make the switch.

This would be at 12kN, but I make the switch much sooner, because RCS needs those heavy ugly yellow tanks to function...and those need to be topped up after you forgot to refill them, with an ISRU basee that wasn't designed with MonoProp fuel storage in mind.

[Spricigo]

7 hours ago, Foxster said:

A better question would be: "When do I need RCS at all?". 

and the answer is "I dont, but sometimes is convenient"

[Snark]

8 hours ago, Jestersage said:

When should I go with the LOX vernor RCS instead of the monopropellant Anywhere RCS?

Yes, I know the short answer is "When the Craft is heavy", but How do I know it's heavy enough that it requires the vernor instead of spamming the Anywhere RCS?

Totally depends on your play style.  The two big variables are,

• just how enormous do you tend to build ships, and
• how impatient are you

I never use the Vernors.  For me, they're heavy overkill.  I just use the regular RCS thrusters and am done with it.  My typical design is to have a ring of four the 4-way thrusters at one end of the ship, and a ring of the 1-way thrusters at the opposite end of the ship.  That's it.  That's all.  Works great.  And that works just fine up to ships massing a couple of hundred tons.

For me, "how big is too big" for these thrusters ends to be "effective infinity", since I don't generally play with really gargantuan ships; I very rarely need to dock something weighing more than a couple of hundred tons.

The reason why more powerful thrusters are "unnecessary" is that you really, really don't need high speeds or accelerations.  I never go faster than 0.3 m/s relative speed while docking, and usually keep it down to 0.2 m/s or less.  Even a really big ship maneuvers just fine with the tiny thrusters when the speeds are that low. 

And when I do build something really huge... then I generally don't need to dock it to stuff, because I dock the other stuff to it.  I put the RCS on the little guys, not on the big guy.

The only time I'd ever need to worry about RCS for a ship over a couple of hundred tons is if I have two huge ships that I need to dock together, which very rarely comes up in my gameplay.  On the rare occasions I do need to build something really huge like that... then I generally use SpaceY, which is an excellent parts pack for building really big ships (including 5m parts).  Beautifully designed, nicely balanced, provides a good set of parts in just about every part category.  That includes some beefed-up 4-way and 5-way RCS thrusters that run on monopropellant, basically just scaled-up big brothers to the stock thrusters.  So I just use those if needed.

[Jestersage]

Yes, it was two relative big ship. One is a slightly lengthen shuttle, and the other a same size fuel depot that will re-enter Kerbin. It's a mini ITS.

[Soda Popinski]

I feel Vernors are better on SpacePlanes.  The ISP is better in atmosphere than the monoprop RCS.  The higher Force also works well to counteract atmospheric forces, and looks cleaner.  I have no idea the effect on aerodynamics compared to the monoprop versions in stock aero.

[Snark]

1 hour ago, Jestersage said:

Yes, it was two relative big ship.

Out of curiosity, roughly how big are we talking, here?  50 tons?  100?  1000?  More?

[paulprogart]

7 hours ago, Snark said:

The reason why more powerful thrusters are "unnecessary" is that you really, really don't need high speeds or accelerations.  I never go faster than 0.3 m/s relative speed while docking, and usually keep it down to 0.2 m/s or less.  Even a really big ship maneuvers just fine with the tiny thrusters when the speeds are that low. 

This.  In fact most of the time during docking I find myself switching to fine adjustment mode because normal mode RCS is too abrupt (and I'm too lazy to adjust the limiter).  Of course that may also mean I'm building ships with too many thrusters, but better that than too few!

My experience is still somewhat limited but the only time I've used Vernors so far is for a rescue ship built specially to dock to stranded vessels landed on the Mun.  They seemed ideal for that because they give lots of lateral movement, and the rescue ship would have to use the main engine to control descent anyhow so being unidirectional wasn't a big handicap.  Maybe it could be done with RCS too, but in any event they worked pretty well.  (I'll ignore the fact that I forgot to include some kind of longitudinal thruster for regular docking.  )  They might have other legit applications but for me RCS has worked for everything else so far.

[Jestersage]

9 hours ago, Snark said:

Out of curiosity, roughly how big are we talking, here?  50 tons?  100?  1000?  More?

235 tons for the ship and 120ton for the Orbital Refueler.

Edited February 11, 2017 by Jestersage

[Aegolius13]

I tend to avoid monopropellant RCS thrusters in most situations.  I never dock a lot of my ships, so any RCS on those guys is unnecessary.  For the small-to-medium ships, I tend to dock without any RCS, using the "point each ship and the other ship and then go forward method."  

For most things too large for that method, I use Vernors.  Not really because of the ISP or thrust, but because I'd just rather not deal with a whole extra fuel system.  That often means extra tanks to place, dead weight if not used, risk of running out if used heavily, etc.  The Vernors also look better in my opinion, and handle heat better than the thruster blocks (though the linear RCS ports do too).  

And as mentioned above, for the really big stuff, like space stations, you can generally leave RCS off because the other ship will be maneuvering in.  

The only thing I really use monopropellant RCS on these days are recovery craft for those "retrieve scrap from orbit" contracts. 

Edited February 13, 2017 by Aegolius13

[Blaarkies]

On 2/10/2017 at 6:44 PM, Soda Popinski said:

I feel Vernors are better on SpacePlanes.  The ISP is better in atmosphere than the monoprop RCS.  The higher Force also works well to counteract atmospheric forces, and looks cleaner.  I have no idea the effect on aerodynamics compared to the monoprop versions in stock aero.

They are also the cure to VTOL aircraft