Monoprollent Launcher

[Vladthemad]

So I was watching Scott Manly video, and he was showing off that many parts have no mass and how monoprollent engines with a unlimited fuel cheat can get you to light speed and beyond. Now, I thought I'd try something different, not being a dirty little cheater, and that's to use the rockomax sized RCS tanks and those engines to get things into orbit. You know, only using an exploit. Hah. Turns out it's surprisingly easy...which of course begs the question should RCS parts have mass? I know it lists them as having it, but when you put them on it doesn't actually change the mass of your ship.

[Vectura]

A number of small parts don't have physics to save on CPU power and whatnot

[cptdavep]

I often put a couple of those on command pods, the built in mono propellant gives you a couple of hundred delta-v for emergencies and costs you zero mass. Can even use them to land on Kerbin if you forget your chutes!

[GoSlash27]

So I was watching Scott Manly video, and he was showing off that many parts have no mass and how monoprollent engines with a unlimited fuel cheat can get you to light speed and beyond. Now, I thought I'd try something different, not being a dirty little cheater, and that's to use the rockomax sized RCS tanks and those engines to get things into orbit. You know, only using an exploit. Hah. Turns out it's surprisingly easy...which of course begs the question should RCS parts have mass? I know it lists them as having it, but when you put them on it doesn't actually change the mass of your ship.

Vlad,

While the o-10/ Rockomax RCS tank combo does make an SSTO lifter, the lifter winds up being heavier and more expensive than a rocket/ LF+O tank for the same performance.

What you gain from having weightless engines you lose in empty tank mass, poor Isp, and expense of parts.

Best,

-Slashy

[cantab]

The O-10 engine definitely shouldn't be physicsless IMHO. It allows funny stuff, but an engine with a TWR of Very Large is just silly really. It's not some piddly little thruster, it's a 20 kN engine, and is meant to be comparable to the 24-77.

[Vladthemad]

Vlad,

While the o-10/ Rockomax RCS tank combo does make an SSTO lifter, the lifter winds up being heavier and more expensive than a rocket/ LF+O tank for the same performance.

What you gain from having weightless engines you lose in empty tank mass, poor Isp, and expense of parts.

Best,

-Slashy

The O-10 engine definitely shouldn't be physicsless IMHO. It allows funny stuff, but an engine with a TWR of Very Large is just silly really. It's not some piddly little thruster, it's a 20 kN engine, and is meant to be comparable to the 24-77.

I didn't look into the cost comparisons, but I did check the cost of the Rockmax MP tanks. They are 750, which is dirt cheap. I used ten in a staged in a stack, dumping each tank as it emptied. I didn't even bother with parachutes to recover because chutes would have doubled or tripled the price. 7500 in fuel tanks alone, not counting the pod, engines, or decouplers, is dirt cheap...and I'd be surprised if a standard fueled rocket would even come close.

I've personally used RCS engines often. Clustering the inline ones make a great way to put lander cans on Minmus for example, and even the radial control ones have brought me back to Kerbin numerous times when I neglected to bring enough fuel. Hell, Jeb has even pushed his return vessel to a deorbit a few times with his jetpack...but it's been awhile since I've had to do that

While I feel that as a sandbox game it really is up to you what you use and don't use, I think I tend to agree with Cantab that they are a bit overpowered due to the fact they are really massless. Of course someone using a ladder to climb to space is a little ridiculous too....

[UmbralRaptor]

[FL-R1 tanks] are 750, which is dirt cheap

They're 1300 funds for a 3.4 tonne full / 0.4 tonne empty tank. The comparable LFO tanks are 850 funds for a 2.25 / 0.25 tonne tank and 1600 funds for a 4.5 / 0.5 tonne tank. (The LFO ones are cheaper in $/kg)

What sort of payload were you getting with that 7500 (which I suspect is more like 13000) + engines (800 per, 94% the cost of an LV-T30) + decouplers (400 each?) launcher?

[Red Iron Crown]

O-10s being massless isn't as big a deal as it first appears. The poor Isp of the engines and only having one tank available that doesn't have an awful mass ratio limits their exploitability. For almost every situation it's better to use an appropriate LFO engine and tank combination.

[Streetwind]

And then there's ModuleManager

@PART[omsEngine]:FINAL
{
	@PhysicsSignificance = 0
}

I do this for my own savegames for all parts which I think really should have mass (such as the OX-STAT panels). I leave a few that are physicsless for very good reasons (the landing gear bay) or only exist as workarounds for editor limitations (the radial attachment points) and so on. It makes the game feel more consistent to me, which enhances my gameplay experience.

...of course, I use ModuleManager to tweak a million other things as well, so it may just be that I'm addicted to the thing

[Vladthemad]

They're 1300 funds for a 3.4 tonne full / 0.4 tonne empty tank. The comparable LFO tanks are 850 funds for a 2.25 / 0.25 tonne tank and 1600 funds for a 4.5 / 0.5 tonne tank. (The LFO ones are cheaper in $/kg)

What sort of payload were you getting with that 7500 (which I suspect is more like 13000) + engines (800 per, 94% the cost of an LV-T30) + decouplers (400 each?) launcher?

It was a lander, with all usable science items attached headed towards Minmus, with a liquid fuel return system...which I generally use a rather large tank for, comparable to one of the smaller rockomax ones, from a mod. Nothing exceptional, but effectively enough thrust to put any crewed pod I wanted where I wanted. And if it needed more delta V I just slapped on another copy and pasted another tank/decoupler.

I'm currently troubleshooting KSOS trying to get it to work, I'll look into the specifics after I'm done with that. I also caught a glitch in my ship files, causing the game to be unplayable so I deleted them sometime yesterday. Save file was fine, just the ship files wouldn't load and locked up the VAB. If I still have the ship, I'll double check the prices/setup and get a screenshot. If not, I'll build something similar again and check

[Ikaneko]

The Monopropellant engine is used for small apoapsis kicks on satellites. Elsewhere, their poor isp really shows and the fuel tanks are quite bulky, so no good Sea Level TWR.

Well, good luck all the same!!

[GoSlash27]

They're 1300 funds for a 3.4 tonne full / 0.4 tonne empty tank. The comparable LFO tanks are 850 funds for a 2.25 / 0.25 tonne tank and 1600 funds for a 4.5 / 0.5 tonne tank. (The LFO ones are cheaper in $/kg)

What sort of payload were you getting with that 7500 (which I suspect is more like 13000) + engines (800 per, 94% the cost of an LV-T30) + decouplers (400 each?) launcher?

Pretty much this.

I built a model of a Tylo lander for development purposes using o-10s before creating a 48-7S lander for the exact same payload. Here they are side by side on the surface of Tylo:

The O-10 lander is $28,600 and weighs 26 tonnes (not counting the unnecessary engines)

The 48-7S lander is $16,000 and weighs 14 tonnes.

The price is a big deal in career mode, but not sandbox. the *mass*, OTOH, is a potential mission killer.

Best,

-Slashy

[Greep]

I think the idea is you use them on, say, the .03 ton probe, with weightless thermometers, batteries, and science gear. If your engine is weightless too... you can get some pretty crazy efficiency.

And TWR is no problem at all They're weightless just add 400 of them. Although with a probe you only need three, and only because that's needed for landing purposes.

Edit: Actually, funny that TWR was mentioned. Since they're radially mounted and are weightless...

the solution to an ion lander (Edit: this actually probably sucks, but the idea works for anything that just barely needs more TWR. Nukes e.g.):

And while inefficient generally... it is pretty hilarious...

Edited December 26, 2014 by Greep

[Vladthemad]

The ship I made and went to the moon with was a probe, about 7 tons, and the fuel system was about 50k. To be honest, at the time money wasn't a concern, but it sounded cheap.

I rebuilt it with a ten ton test weight that mechjeb can get into orbit at 71km. Here's a pic of the stats in the VAB.

And while the discussion is interesting, all the testing is cutting into my game time! Hahah...so I'll wait a day or so before designing a liquid fueled vehicle that can do the same

Edited December 27, 2014 by Vladthemad

[UmbralRaptor]

I'd like to see a more detailed breakdown of the craft's design, but I think the superiority of LFO has been proven.

For a dirty hack to get 10 (well, 11.2) tonnes into LKO with stock aerodynamics, I would use this:

(Just over 100 tonnes and just under 40k funds)

That's an SSTO using LV-T30s on the outside and an LV-T45 in the center for TVC. Taking advantage of advanced features like FAR or fuel lines would only improve its performance, giving it a mass efficiency advantage in addition to its cost efficiency.

[Greep]

Eh I've been finding the T45s more and more useless as time goes on. I'm pretty sure a T30 with a tier-2 (or even tier-1) reaction wheel outdoes it anywhere.

Edited December 28, 2014 by Greep