RCS/monoprop amount - or what are good simple test to do so?

[Jestersage]

So I am building a spaceplane, and is currently debating how many mono-tanks -- and thus, how much parts -- should I actually have on it.

I am looking at this, but the only answer that I can even find is at the end, implying about 5-10 unit of mono per ton with the desired payload.

So what is the rule-of-thumb of monoprop amount, if one desired this ship to be able to dock to a station in LKO?

Edited July 11, 2020 by Jestersage

[bewing]

It depends on how good your docking capabilities are. A newb needs 50 units per tonne. An expert needs less than 1.

[Draalo]

Build a vessel - any kind, using RCS.

Launch. Hit ALT-F12, use cheat menu getting into otbit.

Activate RCS, press and hold the H-key.

Stop the time until monoprop is done and compare orbital speed at end and beginning.

Get an idea

[Jestersage]

5 hours ago, bewing said:

It depends on how good your docking capabilities are. A newb needs 50 units per tonne. An expert needs less than 1.

The problem with designing for self vs designing for publishing (and others to use)... Oh well. will have to think about it.

[Spricigo]

On 7/12/2020 at 1:40 AM, Jestersage said:

The problem with designing for self... 

Since I become aware of independent throttle and Axis Groups, crafts I use don't have RCS anymore, just small retroengines if necessary. 

On 7/12/2020 at 1:40 AM, Jestersage said:

...vs designing for publishing (and others to use)...

Gut feeling says 5-10 units/t (45-90m/s RCS Delta-V) is OK for most pilots. That assuming RCS thruster are balanced and reaction wheels take care of rotation. 

 

 

 

 

Edited July 13, 2020 by Spricigo

[Daveroski]

A craft needs only enough monoprop to get you onto the next station where your stock can be resupplied. Any more than that and you are wasting fuel carrying mono that you won't use.

Taking a small space plane that only carries crew to orbit and back (10 inc crew) I only need the mono in the cockpit and most of the time even that is 100's of % too much.

One thing that most people tend to neglect is the strength of the thrusters. Much mono can be wasted by having thrusters that are too powerful causing one to overshoot and have to compensate. It is quite surprising how  much mono can be saved simply by turning down the power of the thrusters.

On the space plane mentioned above I have the thrusters turned down to about 25% power. And always try to make sure that they are not overpowered for any ship I design.

I put one of the largest tanks on each station and usually never have to refill them. There is usually enough for the whole game.

Any ships that become obsolete on the station will donate their resources before leaving the station to be scrapped.

D.

 

[Zhetaan]

On 7/11/2020 at 6:21 PM, Jestersage said:

So what is the rule-of-thumb of monoprop amount, if one desired this ship to be able to dock to a station in LKO?

I tend to dock with what's in the cockpit or pod on-board tank.  If I have an exceptionally heavy payload or other factor that calls into question whether I'll need more, then I usually include the extra with the payload, either as part of it or at least in the docking bay.  However, I also use Kerbal Construction Time, which rewards minimal redesign for recoverable craft; I have a strong incentive to include extra anything with the payload.

Admittedly, I have been docking for a long time, but the thing to remember is that there is a tremendous gap between the on-board tank and the same-size monopropellant tank; the dedicated tanks are absolutely enormous compared to the typical need.  If you need one, then you need only one.

[king of nowhere]

the amount of rcs fuel is really variable by individual. for example, i don't use the rcs at all, so i need none