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Do you use command pods monopropellant?

Tell me...   102 members have voted

  1. 1. Do you use the monopropellant stored in Command Pods?

    • I do use the monopropellant stored in Command Pods
    • I do not use the monopropellant stored in Command Pods
    • I wasn't aware they had monopropellant tanks!
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52 posts in this topic

I think the space for monoprop should still be there, but empty by default when you select the part from the parts list, like how ore tanks are empty. Another thing I would like to change the default for is brakes. They should be on by default, unless it will break craft. Or am I being silly and there is a way to toggle this in the SPH/VAB?

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I use it when I need it and drain it when I don't. For many craft, the command pod/ cockpit carries just the right amount of monoprop for the mission and I don't have to add a tank.

Best,
-Slashy

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Posted (edited)

Yes, because infinite EVA fuel is a silly idea, and I mod my game to have as few silly ideas as possible.

17 hours ago, Rocket In My Pocket said:

Personally I don't really see a lot of fun stemming from having to keep track of EVA fuel

Do you have fun keeping track of Liquid Fuel and Oxidizer?

Edited by klgraham1013

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I use the monopropellant if I'm using RCS, but if not I drain it.

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Posted (edited)

3 hours ago, klgraham1013 said:

Do you have fun keeping track of Liquid Fuel and Oxidizer?

Yeah, because it's the meat and potatoes of the game.

In a stock game without KIS/KAS stuff (I don't use either), there really isn't much use for an EVA'd Kerbal except to move him to another craft without docking ports. Complicating this with fuel requirements really serves no game play purpose.

By comparison building rockets with the right combination of weight, fuel, and TWR to get the Delta V you need is literally the point of the game and has actual game play with challenges and choices.

Edited by Rocket In My Pocket

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Well doh. Considering that the Mk-I lander can has enouh RCS for docking at least a dozen times before you need to refill it, of course I use it. Beats adding external RCS tanks by a long shot. And the rest of the pods have bigger RCS tanks (except the Mk I capsule maybe, but there's another "more than you'll ever need" case)

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well, I play with realfuels in a stockalike config. This means ullage motors are required to restart many vacuum engines.
The little bit in the command pods is just about spot on for driving ullage burns. 

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Sometimes I slap a "Last Chance Drive" on my command pod, which is three or four Puffs which use the internal monoprop. Usually it is useless (and harmless, since Puffs AFAIK have no drag and minuscule mass), but sometimes the "Last Chance Drive" provides the final bit of dV to reach home.

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Yep. Use it all the time.

Especially since I'm now dependent on the M.O.L.E. mod (for happiness and wellbeing, naturally), which has the ports built in to the crewed capsules.

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Posted (edited)

I use whatever I have if it looks like it's needed. What is missing seemingly from this game is the ability for the command pods to use the mono propellent from it's nose to slow down as it balantantly is suppose to by those wholes in the front. Why did they never add this in. It's much easier on design than needing to add extra parts. It seems obvious it was meant to be able to do this. I'm pretty sure this is why they have the mono propellient in them. All like parts should have automatic RCS mono thrusters in them to aid in craft control.

Edited by Arugela

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On 20.6.2017 at 2:49 AM, ave369 said:

Sometimes I slap a "Last Chance Drive" on my command pod, which is three or four Puffs which use the internal monoprop. Usually it is useless (and harmless, since Puffs AFAIK have no drag and minuscule mass), but sometimes the "Last Chance Drive" provides the final bit of dV to reach home.

There is no free lunch, and there definitely is no free delta v; Isp of RCS thrusters is so poor that even though they are small, you'll have more delta v by just not attaching them and draining the fuel from the pod.

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20 hours ago, kurja said:

There is no free lunch, and there definitely is no free delta v; Isp of RCS thrusters is so poor that even though they are small, you'll have more delta v by just not attaching them and draining the fuel from the pod.

I said Puffs, not RCS thrusters.

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3 minutes ago, ave369 said:

I said Puffs, not RCS thrusters.

I should have said "monopropellant thrusters", I guess. But it doesn't matter, Puffs are just as bad or even worse as they're heavier while their Isp is only ten seconds higher.

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Still, having an emergency reserve of dV is a good thing.

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37 minutes ago, ave369 said:

Still, having an emergency reserve of dV is a good thing.

Even when adding that reserve reduces your delta v?

Just do the math; let's consider a small craft with a pod, heatshield, decoupler, flt 400 tank and a 'spark' engine. That's 3.5 tons total, 2.5 tons of propellant, dv 2659.8 m/s.

Now let's add monoprop to the pod and two radial puff engines. Added mass drops our earlier dv to 2421.6 m/s - 238 less than before. Decoupling the LF tank and engine, monoprop & puffs give us 95.2 m/s, less than half of what was lost by adding them. In actual use it gets even worse as mass of the monoprop and puffs penalize every earlier stage as well.

Not a very good thing?

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Posted (edited)

That's not what my typical upper stage looks like. It usually has NERV engines and a way larger tank (or several, usually at least a quarter-length Rockomax, often more than that). This way, the dV loss is within statistical error margins. It is even more reduced by the fact that I never remove any monoprop from pods, so any loss is from the puffs only, and therefore negligible.

 

I'm a sort of person who will rather launch a giant Fender guitar or an Imperial Star Destroyer into space than a micro-optimized mosquito.

Edited by ave369

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8 hours ago, ave369 said:

That's not what my typical upper stage looks like. It usually has NERV engines and a way larger tank (or several, usually at least a quarter-length Rockomax, often more than that). This way, the dV loss is within statistical error margins. It is even more reduced by the fact that I never remove any monoprop from pods, so any loss is from the puffs only, and therefore negligible.

 

I'm a sort of person who will rather launch a giant Fender guitar or an Imperial Star Destroyer into space than a micro-optimized mosquito.

Certainly, as the final stage fuel & engine masses becomes some very small fraction of the whole vessel's mass, the delta v penalty diminishes. A 100 ton NERV-propelled stage might suffer by only two or three meters per second, out of ten thousand.

If using puffs as a final stage is something you like, by all means do, it's just not going to give you an "emergency reserve of delta v", be the rocket small or large.

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Posted (edited)

8 hours ago, ave369 said:

I'm a sort of person who will rather launch a giant Fender guitar or an Imperial Star Destroyer into space than a micro-optimized mosquito.

That is perfectly fine. However, you're more likely to get that Star Destroyer into orbit if you leave the Puffs and Monoprop at home.

No matter the ship, bringing extra mass and a worse engine to get extra delta-v is like driving a car faster to get to the gas station before you run out of fuel. It feels like it might work but it actually makes it worse.

Edited by 5thHorseman
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Posted (edited)

1 hour ago, kurja said:

 A 100 ton NERV-propelled stage might suffer by only two or three meters per second, out of ten thousand.

it's just not going to give you an "emergency reserve of delta v", be the rocket small or large.

First, if the dV of the stage with NERVs and rockomax fuel and all the jazz suffers merely by two or three m/s, and when I jettison all this stuff and leave only the command pod, the puffs, the parachute and the heatshield, I get 95.2 m/s of dV in the super-final stage, I win.

 

Second, I think you misunderstand what the "emergency reserve of dV" means. It is not some extra dV that the ship would not otherwise have. It is dV that is not consumed during normal flight, and is only used when really needed. It is reserved for emergencies, and this is why it's called an emergency reserve. It isn't for fuel efficiency, it is for not being stranded. Even if I reduce the total dV, having a bit of dV the ship will not gobble until I tell it to is still a win.

Quote

is like driving a car faster to get to the gas station before you run out of fuel.

No, it's not like that. It's like having a scooter in the car on which I can ride if I run out of gas. The scooter has its own independent little gas tank, and if the car's tank runs dry, the scooter's won't.

Edited by ave369

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29 minutes ago, ave369 said:

First, if the dV of the stage with NERVs and rockomax fuel and all the jazz suffers merely by two or three m/s, and when I jettison all this stuff and leave only the command pod, the puffs, the parachute and the heatshield, I get 95.2 m/s of dV in the super-final stage, I win.

 

Well, that might appear so, but if you'd have left the extra mass behind you would have had those 95.2 in the previous stage. There is no winning in the mathematical sense. I think this is what people where trying to explain and what you also understood.

I get what you are saying about putting some fuel away into an additional stage as a kind of emergency stage. Makes a lot of sense from a mission or story point of view too.

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Posted (edited)

26 minutes ago, Dafni said:

 you would have had those 95.2 in the previous stage.

I don't want them in the previous stage. I want them in the emergency stage. If I leave them in a previous stage, a slight miscalculation, and the ship is stranded, and I have to either launch a grappler ship with extra fuel to dock with it or use the cheat menu. If I do it my way, there's a chance to rescue the crewman. It's not called the "Get there amazingly fast drive". It's called the "Last chance drive". And when I, say, return from Minmus, a 95.2 m/s burn in the apoapsis can make all the difference between being stuck in orbit and lowering your periapsis enough to aerobrake. During interplanetary burns, 95 m/s also can make all the difference between flying by Kerbin and aerobraking when you use them in the beginning of the Hohmann transfer

 

If I leave those 95.2 m/s in the main ship, any goddamn unplanned event can eat them up. And I'm not just talking about stuff like confusing prograde and retrograde because I'm too sleepy, or missing a key and pressing Z instead of Shift. Basic maneuver planning can go wrong as well. Miscalculating a suicide burn and having to do it twice - bye-bye some m/s. Seeing I've still got a lot of fuel in a tank and breaking orbit in the wrong direction because "I've got a nearly full tank, what can go wrong?" - bye-bye some m/s. When these m/s are in a special strongbox marked "Do not open unless you really need to", it's a whole another matter.

Edited by ave369

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Posted (edited)

3 hours ago, ave369 said:

First, if the dV of the stage with NERVs and rockomax fuel and all the jazz suffers merely by two or three m/s, and when I jettison all this stuff and leave only the command pod, the puffs, the parachute and the heatshield, I get 95.2 m/s of dV in the super-final stage, I win.

 

No, you don't. I accounted for the delta v available in the final stage versus delta v lost in the previous stage; loss of only a few m/s is the best case scenario in total delta v.

No point in having any sort of argument over this, it's just a fact of math that adding monoprop thrusters & fuel to drive a final stage will amount to less delta v, than omitting them and their fuel. If it rocks anyone's boat to use them anyway, awesome, I have no problem with yours or anyone's gameplay. I'm just pointing out that if anyone is thinking that they'd gain some extra dv this way, they won't.

Edited by kurja

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1 hour ago, kurja said:

No, you don't. I accounted for the delta v available in the final stage versus delta v lost in the previous stage; loss of only a few m/s is the best case scenario in total delta v.

No point in having any sort of argument over this, it's just a fact of math that adding monoprop thrusters & fuel to drive a final stage will amount to less delta v, than omitting them and their fuel. If it rocks anyone's boat to use them anyway, awesome, I have no problem with yours or anyone's gameplay. I'm just pointing out that if anyone is thinking that they'd gain some extra dv this way, they won't.

To be fair, it does add a bit of operational flexibility; if, say, you eject the pod from the service module and want to tweak your reentry a bit, it's nice to have that RCS available. It's why I often slap a couple of the linear RCS ports onto Mk 1 pods and a ring of quad-ports onto larger capsules. I will, however, grant that with many types of staging design, it probably overall reduces available delta-V; it just adds a bit of delta-V that isn't gone even after service module separation.

Part of what ameliorates things for me is that Real Fuels drops the mass of the parts significantly (11 kg for the linear ports, 15 kg for the extra-light quad blocks added by KW Rocketry), so there's less lost by adding the RCS ports. It doesn't help with the heavy, low-Isp hydrazine, but it's a tradeoff I'm willing to make for a small amount of last-second maneuverability.

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On my orbital utility vehicles, the command pod is a fully functional "escape pod" with balanced RCS thrusters so that I can dock a few to my space stations.

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9 hours ago, kurja said:

than omitting them and their fuel.

I NEVER omit the fuel anyway. So I don't lose anything significant by adding the puffs.

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