why not always use vernor engines rather than monopropellant-based RCS engines?

[not enough fuel]

when i'm making this ship i don't understand why i wouldn't just put vernor engines on it for translation rather than monoprop engines, because that would require me to take up extra space with monopropellant tanks. so why aren't all RCS thrusters done with vernor engines? (assuming the ship uses liq/ox fuel)

[king of nowhere]

2 hours ago, not enough fuel said:

when i'm making this ship i don't understand why i wouldn't just put vernor engines on it for translation rather than monoprop engines, because that would require me to take up extra space with monopropellant tanks. so why aren't all RCS thrusters done with vernor engines? (assuming the ship uses liq/ox fuel)

vernor engines are practical on large ships. but they weight 80 kg each. even just having one for each of the six directions requires 480 kg of extra mass.

so, if you build motherships in the hundreds or thousands of tons, vernor is the way to go. for smaller crafts, using something lighter is better. and the small amount of monoprop held by most crew pods is enough, no need for extra tanks

[Superfluous J]

Build 2 ships, one with monoprop and one with vernors. Check their dV stats and decide if the drop is worth it.

I tended to find it is, so much that if my ship needs more monoprop than is in the capsules, I use vernors.

[Tecorian]

Besides the good comments above, if you play "near-reality", monoprop is the right way.

In real life, it is very tricky to ingite a normal rocket motor more than two or three times.

The upper stage of Ariane VI failed at this point and even the engines of Space x, which are especially designed to do this, have their themes.

Like @king of nowhere i use them in KSP1 only with very large interplanetary ships, but mostly i use than reactionwheels to get a direction.

Subships or landers have again monoprops on board.

[king of nowhere]

to be specific, I only use vernors on fuel tankers.

normal ships are too small to justify the extra mass, and they don't really need rcs anyway.

larger motherships don't need rcs, it's other ships that move around them.

but a dedicated fuel tanker, in the 100-500 tons range, is big enough that reaction wheels aren't all that comfortable to use, and it has to dock lots of times. they are the only case when spending half a ton for easier docking feels justified.

[ColdJ]

On 8/8/2024 at 7:05 AM, not enough fuel said:

when i'm making this ship i don't understand why i wouldn't just put vernor engines on it for translation rather than monoprop engines, because that would require me to take up extra space with monopropellant tanks. so why aren't all RCS thrusters done with vernor engines? (assuming the ship uses liq/ox fuel)

Vernors are way to powerful too. Once you try to do a rendezvous in orbit, let alone a docking, you will see why you want a monoprop RCS system. If you tend to use them for corrections when in atmosphere, then well placed canards can actually do a better job for you. Landing and taking off from the Mun can actually be achieved with monprop.