RCS and Vernor thrusters in 1.1

[Just Jim]

I have a quick question about the RCS and vernor thrusters: Have they changed since 1.1?

Reason I ask is one of my heavy duty rovers called a Chariot.  It's my all purpose heavy rover, but now I've noticed it doesn't work nearly so well in an atmosphere.  Used to be nearly as easy to drive on Kerbin as the Mun, but now....  on the Mun it's still outstanding, but on Kerbin... blehhhh.  It's especially bad now at climbing hills.

I know there are issues with wheels, but then I also noticed the thrusters now seem to work differently ASL than in a vacuum.  This particular rover design has all sorts of thrusters, including 4 rear vernor ones for speed and hill climbing.  But now they seem to be much weaker on Kerbin.

So this is my question, I can't for the life of me remember one way or the other, but didn't thrusters work differently before 1.1?  Is the ASL and VAC difference new?  
Or am I just losing it?  

Thanks

 

 

Edited May 13, 2016 by Just Jim

[Geschosskopf]

Well, 1st thing is that in 1.1.x, rover wheels all take about 5x more EC/sec than they did in all recorded prior history.  This isn't really noticeable on level ground but really kicks in going up hills.  Unless you have all the power they need, you just cain't climb hills.

Second thing is, the new 1.1.x wheel tweakable of "Traction Control".  From what I can tell, this functions exactly as in real life, reducing power to wheels that the system perceives to be slipping/spinning.  Problem is, because wheels don't actually turn in KSP, but are just lander legs that can slide over the ground, there's no real wheel RPM to measure independently of all the other variables in the situation, so going up hills seems to generate a false positive for wheel slippage, causing Traction Control to reduce power to the wheels, making it impossible to climb hills.  To fix this, set Traction Control to zero.

Third thing is, in 1.1.x, the mondo wheels used by your Chariots use differential steering like tank treads instead of pivoting like the smaller wheels. The efficacy of differential steering is inversely proportional to vehicle speed.  Rovers with the mondo wheels only have much steering authority at relatively low speeds, like 2-3m/s.  This does, of course, vary with local gravity, so in low gravity they can turn well at higher speeds but not on Kerbin.  And of course Kerbin's atmosphere hoses the efficacy of small thrusters.

One thing to be VERY careful of on Kerbin, however, is a bug with the mondo wheels where repeatedly tapping opposite steering keys can GREATLY increase your speed.  It's possible to get rovers with mondo wheels going over 60m/s in a more or less straight line, which usually ends tragically so I don't recommend doing it except for larfs

 

[NathanKell]

To actually answer your question, yes, RCS thrusters work just like engines. They don't magically use more fuel at sea level than in space, and therefore (since they have lower Isp at sea level than in space) they produce less thrust at sea level than in space. That has been true since 1.0.5.

[Just Jim]

24 minutes ago, NathanKell said:

To actually answer your question, yes, RCS thrusters work just like engines. They don't magically use more fuel at sea level than in space, and therefore (since they have lower Isp at sea level than in space) they produce less thrust at sea level than in space. That has been true since 1.0.5.

Ahhhh, this explains why I can't use them to accelerate on Kerbin like I used to, thanks!

 

36 minutes ago, Geschosskopf said:

Well, 1st thing is that in 1.1.x, rover wheels all take about 5x more EC/sec than they did in all recorded prior history.  This isn't really noticeable on level ground but really kicks in going up hills.  Unless you have all the power they need, you just cain't climb hills.

Second thing is, the new 1.1.x wheel tweakable of "Traction Control".  From what I can tell, this functions exactly as in real life, reducing power to wheels that the system perceives to be slipping/spinning.  Problem is, because wheels don't actually turn in KSP, but are just lander legs that can slide over the ground, there's no real wheel RPM to measure independently of all the other variables in the situation, so going up hills seems to generate a false positive for wheel slippage, causing Traction Control to reduce power to the wheels, making it impossible to climb hills.  To fix this, set Traction Control to zero.

Third thing is, in 1.1.x, the mondo wheels used by your Chariots use differential steering like tank treads instead of pivoting like the smaller wheels. The efficacy of differential steering is inversely proportional to vehicle speed.  Rovers with the mondo wheels only have much steering authority at relatively low speeds, like 2-3m/s.  This does, of course, vary with local gravity, so in low gravity they can turn well at higher speeds but not on Kerbin.  And of course Kerbin's atmosphere hoses the efficacy of small thrusters.

One thing to be VERY careful of on Kerbin, however, is a bug with the mondo wheels where repeatedly tapping opposite steering keys can GREATLY increase your speed.  It's possible to get rovers with mondo wheels going over 60m/s in a more or less straight line, which usually ends tragically so I don't recommend doing it except for larfs

yeah, the Chariot bogs down on hills now, bad.  I wondered how the traction control worked, I'll experiment with it tomorrow, thanks!

I did run into that turning bug, and almost flipped a Chariot in the process. Suddenly it went from something like 15 m/s to almost 50 and was airborne.  It was pretty funny, I should have gotten a screenshot.

I am very familiar with the differential turning, I drove an M113A2 APC for about 2 years when I was in the Army... and I absolutely loved it!  They're a little smaller and lighter than an actual tank, and just about the most fun you can have with no wheels!  Here's a good pic of one, except I was a medic, so my version swapped out a .50 cal for a big red cross.  This is probably why I like the big wheels so much.  If they had stock tracks in the game I'd be all over them!

Anyway, thanks!  This answers my questions

 

Edited May 14, 2016 by Just Jim

[Geschosskopf]

33 minutes ago, Just Jim said:

yeah, the Chariot bogs down on hills now, bad.  I wondered how the traction control worked, I'll experiment with it tomorrow, thanks!

There's also Friction, which is entirely intuitive.  The more you have, the steeper hills you can climb and the steeper slopes you can stop on without sliding.  However, increasing Friction increases EC/sec needed and also increases Tire Stress, which if that ever pegs out results in a flat, so speed should be reduced in proportion to upping Friction.

 

33 minutes ago, Just Jim said:

I am very familiar with the differential turning, I drove an M113A2 APC for about 2 years when I was in the Army.

The M113 is a fun thing to drive, no doubt.  I did it for a few minutes once, same for half a dozen other tracked AFVs both US and Soviet,  They're all so much more fun than bulldozers and I wish I'd have gotten more chances to drive them   But that was never my job.  I job was killing AFVs and I went to war in the back of a truck.