Will the RCS engines get nerfed?

[Galane]

Put a couple of them and a small probe body on a small mono tank and it can do a Kerbin escape going straight up. (Fly monopropellant only to...)

Whether or not any changes get made to those engines, I'd like to see fuel bar graphs for them like the other thrust engines have.

[cmd112]

They probably won't get nerfed too much - so far I've only seen people use them to highlight the ridiculous speeds they can reach if you stack a lot of them on a small ship. I guess they'll make it non-massless since that's where most of their OP power comes from.

[UmbralRaptor]

Pics of the craft please? I'm fairly sure you'd need to use the FL-R1 (2.5 m) RCS tank to get anything to escape Kerbin. Of course, you can do much the same with careful design with other engines. I'd look into the KR-2L in particular...

The O-10 engines have "PhysicsSignificance = 1" in their part.cfg for some reason, giving them effectively infinite TWR. This makes them far more powerful than they "should" be, although in practice Isp and mass ratio limits minimize the balance issue. Compare the payload fractions and cost per tonne to LKO for carrier rockets built around the O-10 with more conventional designs.

[Franklin]

Pics of the craft please? I'm fairly sure yâ€â€

[Franklin]

It's not an escape but I also made it in 5 seconds and that was my first test launch. I'm sure I could make an escape-able rocket if I wanted to bother.

Essentially this is your exploitables list: http://wiki.kerbalspaceprogram.com/wiki/Massless_part

[Franklin]

1x QBE

1x FL-R1

6x O-10

Little more...

[Red Iron Crown]

The O-10 engines have "PhysicsSignificance = 1" in their part.cfg for some reason, giving them effectively infinite TWR. This makes them far more powerful than they "should" be, although in practice Isp and mass ratio limits minimize the balance issue. Compare the payload fractions and cost per tonne to LKO for carrier rockets built around the O-10 with more conventional designs.

This. O-10s are good for quick "stunt" craft, but if you have any real payload their lack of mass gets overshadowed by their poor efficiency and railroading to a single tank type (FL-R1).

The OP's point about the fuel bar is a good one (same for ions for that matter).

[Rithsom]

The OP's point about the fuel bar is a good one (same for ions for that matter).

Adding a fuel bar doesn't seem that hard, but maybe there's an issue preventing the devs from doing it (probably because the ion, LV-1, and 0-10 engines all don't follow the standard fuel crossfeed rule).

Edited September 15, 2014 by Rthsom

[UmbralRaptor]

It's not an escape but I also made it in 5 seconds and that was my first test launch. I'm sure I could make an escape-able rocket if I wanted to bother.

I don't have FAR installed... how would a QBE + FL-T100 + 48-7S do? (This should be of roughly equivalent mass and have significantly higher ÃŽâ€V) The O-10's lack of mass is weird/should be fixed, but is comparatively minor.

Essentially this is your exploitables list: http://wiki.kerbalspaceprogram.com/wiki/Massless_part

I know -- check the contributors. >_>

This. O-10s are good for quick "stunt" craft, but if you have any real payload their lack of mass gets overshadowed by their poor efficiency and railroading to a single tank type (FL-R1).

The OP's point about the fuel bar is a good one (same for ions for that matter).

Also the LV-1 (though not the LV-1R). That said, I'd sort of prefer an oxidizer bar for rocket engines...

[Wanderfound]

Also the LV-1 (though not the LV-1R). That said, I'd sort of prefer an oxidizer bar for rocket engines...

Ditto. My spaceplanes get into trouble fairly regularly when I forget that "plenty of LF remaining" doesn't necessarily mean "plenty of O remaining".

Having to keep the resources tab open all the time to prevent this is a screen-cluttering PITA.

[SunChaser]

This. O-10s are good for quick "stunt" craft, but if you have any real payload their lack of mass gets overshadowed by their poor efficiency and railroading to a single tank type (FL-R1).

The OP's point about the fuel bar is a good one (same for ions for that matter).

This. Massless thrusters only work if your whole craft if a small fuel tank and a probe core (you can make it to orbit with the small SRB's and O-10's by the way).

However, there is no downside to slapping a crapload of Vernors and a few O-10's on your ship and binding them to action groups to toggle on/off. That way you can save a little fuel without having to sacrifice delta-v.

[Galane]

Just did it in vanilla KSP+MechJeb, only using MJ's terminal velocity limiter and stock SAS turned on to keep it pointed straight up.

Two stacked R1 (750 unit) tanks, six O-10's around the upper R1, topped with an OKTO2. Nothing else. The trick is to hit the TV limiter to force throttling back at least part of the time in the lower half of the atmosphere. It takes at least four of the engines to have TWR>1 but they can't go fast enough to hit TV and peak altitude is well outside Mun orbit. Put a solar panel on it for an eight part Mun craft?

With Stock Drag Fix it only needs one R1 under an OKTO2 and two O-10 engines. Shows how much the stock drag model that applies drag to the fuel in the tanks bogs things down.

Edited September 15, 2014 by Galane

[magnemoe]

They probably won't get nerfed too much - so far I've only seen people use them to highlight the ridiculous speeds they can reach if you stack a lot of them on a small ship. I guess they'll make it non-massless since that's where most of their OP power comes from.

I only use them for orbital RSC tugs where they are excellent as they just need one fuel type, for probes and that sort of stuff the 48-7S are better as its have better ISP.

however I should probably use it more for small landers who dock with mothership again as it would let me dock the lander to mothership and not the other way around.

[Frank_G]

I didnt use them, until i tried to built a very efficient and compact lander for a mission to Tylo... since then, i use them constantly. Excellent piece of hardware.

This little ship can lift off Tylo, reaching a low orbit with ease... It packs 3.1k of delta V. No mods, no part clipping.

[edit] It was also the core part of my Eve ascend ship.

Edited September 15, 2014 by Frank_G

[Renegrade]

[edit] It was also the core part of my Eve ascend ship.

http://i.imgur.com/Rf0xIoO.png

I like the look of your interplanetary Eve unit there, very neat. What are the cones behind the aft fuel tanks? The lil A10 adapters?

[Kasuha]

I don't think O-10 engines need a nerf. But I think something could be done about lost mass of "massless" parts. It should be added to the mass of the ship somehow, my personal favorite is distributing it proportionally over all remaining "massy" parts. For normal ships that don't use massless parts too extensively, it would mean negligible change.

[Corw]

I don't think O-10 engines need a nerf. But I think something could be done about lost mass of "massless" parts. It should be added to the mass of the ship somehow, my personal favorite is distributing it proportionally over all remaining "massy" parts. For normal ships that don't use massless parts too extensively, it would mean negligible change.

Create virtual part in the centre of the mass and add all mass belonging to the massless parts to it?

[Red Iron Crown]

Create virtual part in the centre of the mass and add all mass belonging to the massless parts to it?

I've heard that suggested before but I see some problems with it. First, it is entirely possible to construct a ship with the center of mass in empty space, which may cause problems for the engine. Second, it reduces the polar moment of inertia (resistance to turning), though that is probably not significant unless a significant portion of the ship's mass is composed of physicsless parts.

I prefer the alternate suggestion I've heard of assigning the mass to the nearest physically significant parent part in the tree.

Of course, the best solution would be to do away with physicsless parts in the first place, but without knowing the reasons why it was done it's hard to say if that's good idea or not.

[Kasuha]

Of course, the best solution would be to do away with physicsless parts in the first place, but without knowing the reasons why it was done it's hard to say if that's good idea or not.

I'm quite certain important part of the reason is to reduce load on the physics engine. Major part of currently massless parts was made massless in a release which was (among others) aimed at performance improvements.

[Red Iron Crown]

That's a suspicion that I share, but I haven't heard anything definitive from an official source as to the reasoning.

[Wanderfound]

That's a suspicion that I share, but I haven't heard anything definitive from an official source as to the reasoning.

Most of the problems with physicsless parts stem from their abuse as infinite TWR thrusters. It may be best to keep struts etc as physicsless but not anything that produces thrust; RCS/Vernor/O-10's.

If you're sticking enough of those on your craft to strain the physics engine, it's probably because you're trying to do something silly and physics-defying anyway.

[Franklin]

I don't have FAR installed... how would a QBE + FL-T100 + 48-7S do? (This should be of roughly equivalent mass and have significantly higher ÃŽâ€V) The O-10's lack of mass is weird/should be fixed, but is comparatively minor.

FAR probably makes the exploit easier really, as it thins the soup you need to shove through in stock. You just need to watch your speed. That's why my second attempt had FAR off.

With what Galane said though, using a thrust limiter makes the engines even more efficient in the soup. If they were asparagus-able they'd be even better.

But making it so no parts were massless would go a long way in dialing back these exploits, as you've pointed out.

[Red Iron Crown]

With what Galane said though, using a thrust limiter makes the engines even more efficient in the soup. If they were asparagus-able they'd be even better.

They are asparagus-able, it just has to be assembled a little differently. Instead of attaching each pair of boosters to the core stage with a radial decoupler, instead attach them to the previous pair of boosters. Monoprop fuel tank drain order is determined by the number of decouplers between tank and root part, the more decouplers the earlier it drains.

[Franklin]

They are asparagus-able, it just has to be assembled a little differently. Instead of attaching each pair of boosters to the core stage with a radial decoupler, instead attach them to the previous pair of boosters. Monoprop fuel tank drain order is determined by the number of decouplers between tank and root part, the more decouplers the earlier it drains.

How strange. This almost seems like a patchy approach to them getting mono to work like fuel. I hope it's updated down the road to work exactly as an alt-fuel.

[Eric S]

I prefer the alternate suggestion I've heard of assigning the mass to the nearest physically significant parent part in the tree.

For most things, I'd agree, but I've had a few times where the airplane-style landing gear were mounted non-symmetrically (from the VAB point of view, not SPH) and if the mass of them was added to the tanks they were attached to, it would still be shifting the mass off center. I prefer Kasuha's idea of spreading it out proportionally to all the non-massless parts.

Of course, the best solution would be to do away with physicsless parts in the first place, but without knowing the reasons why it was done it's hard to say if that's good idea or not.

I'm quite certain important part of the reason is to reduce load on the physics engine. Major part of currently massless parts was made massless in a release which was (among others) aimed at performance improvements.

One other possible reason is that the Unity engine has problems if you have two rigid body masses connected where one part significantly out-masses the other. From what I understand, this is a fairly common issue amongst most physics engines.