[1.1.2] Realism Overhaul v11.0.0 May 8

[Starwaster]

Well, ok. I am well familiar with module manager configs, but so far I won't change anything.

A few more questions if you don't mind.

Is it possible to make an engine switch modes in flight but retain "fuel type switch in hangar" functionality? I want to make NERVA with afterburner. I've did it in stock KSP and got so much used to it that it's difficult to do without one.

Are there any additional escape towers out there? E. G. for the small capsule.

Raptor's stock alike engine pack for RF has an example of how to do such an engine (known as LANTR or sometimes, trimodal because it has three functional modes: NTR, LOX Augmented NTR (your 'afterburner', LANTR) and power generation)

[Guest]

So stock KSP's unrealism, in terms of rocket delta-V, creeps in through how heavy the rocket engines and empty fuel tanks are, and real rockets have very large rises in acceleration (due to decreasing mass but constant engine thrust) just before they stage?

Stock gets around the problem of a tiny solar system not only by having unrealistic atmospheric drag and not using isp correctly, but also by artificially inflating everything's mass. This isn't that big of an issue when you consider game balance, but it is not realistic. As far as gee force increases during launch, which can be very pronounced when using larger lower stages, a good way around that is to use even larger lower stages with SRM boosters. SRMs give you a good on-pad TWR for an anemic core stage, which keeps the TWR low during later flight.

E: So, believe it or not, "MOAR BOOSTERS" is sometimes appropriate in RO.

E2: Also, now that I'm thinking about it, Engineer (and MechJeb, I think) will show you the min and max TWR for a stage, and it will take into account a +1 stage's (boosters with core firing) firing time. This is very helpful to see if the fat core stage with extra boosters to get off the pad will still have the TWR you want when you jettison those boosters.

Edited March 12, 2015 by regex
fat-fingering my phone.

[NathanKell]

You're most welcome!

Regarding high burnout TWRs--in real life, there's the issue called "propellant residuals". Basically, the turbopump can't suck the tanks dry; the engine will flame out before the tanks are 100% pressurant and 0% propellant, and what's left is called the residuals. First stages often have residuals on the order of 0.5%, which means that your burnout mass in real life will be higher than just the dry mass, it'll be (wet mass - dry mass) * 0.5% + dry mass. For upper stages, the residuals are often higher, like on the order of 1%, and the residuals will (AFAIK) also be higher for pressure-fed stages, where there isn't a pump to 'suck', only the pressurant to 'push'.

Consider the Titan II upper stage, used for Gemini. The upper stage is 29t wet, 2.4t dry, and Gemini (payload) is 3.8t. Thrust is 45.4 tonnes force (444.82kN). Naively we'd assume (and this is how it performs in KSP) that burnout TWR is 45.4 / (2.4+3.8) = 7.323 Gs. However, with the 1% residuals (guess), burnout TWR is actually, in real life, only 45.4 / (2.4 + 3.8 + (29-2.4)*1%) = 45.4 / (6.2 + 0.266) = 7G.

That also means that delta V in real life will be less than KSP: In KSP, the simple rocket equation gives you 316s [isp] * 9.80665 [g0] * ln((29+3.8) / (2.4+3.8)) = 316 * 9.80665 * 1.666 = 5162m/s. Counting the residuals, however, the natural log yields 1.624, so delta V drops to 5032m/s.

On a large first stage / small upper stage rocket like Thor-Delta, however, that could mean the difference between a 9G burnout and an 11G burnout for the first stage, though...

Modeling residuals is not something we've attempted yet, both because there would be no easy way to tell MJ or KER about it, and because there's enough other unrealities that make life harder than real in KSP-RO that we think it's safe to leave one unreality in that makes things easier. :]

If your burnout TWRs are too high, rather than MOAR BOOSTERS, try MOAR STAGES. Going to a three-stage vehicle might let you have peak TWRs of only 4G each, whereas a two-stage version might peak at 8 in both cases.

Also, finally, and this is just a guess, but--what do you consider reasonable TWR? Often people coming from KSP think you should launch at 2Gs, and your upper stages should be just as high thrust. Try a lower stage that gives you 1.2 on the pad (sea level TWR, not Vac TWR) and an upper stage that starts at no more than 1.0 in vacuum (if you have delta V to spare, so you can loft high, or you're going high anyway like to >2000km orbit, your upper stage can start with a much lower TWR). Consider that the EELVs (Atlas V, Delta IV) have upper stages that start around 0.2 TWR! Now, that's optimized for geostationary launches, but even going to LEO a starting TWR of 0.6 or 0.7 is totally fine if you loft a bit high and circularize after apogee (Saturn IB is an example of this approach: a long-burning high-energy upper stage with a low TWR).

Edited March 12, 2015 by NathanKell

[-Velocity-]

You're most welcome!

Regarding high burnout TWRs--in real life, there's the issue called "propellant residuals". Basically, the turbopump can't suck the tanks dry; the engine will flame out before the tanks are 100% pressurant and 0% propellant, and what's left is called the residuals. First stages often have residuals on the order of 0.5%, which means that your burnout mass in real life will be higher than just the dry mass, it'll be (wet mass - dry mass) * 0.5% + dry mass. For upper stages, the residuals are often higher, like on the order of 1%, and the residuals will (AFAIK) also be higher for pressure-fed stages, where there isn't a pump to 'suck', only the pressurant to 'push'.

Consider the Titan II upper stage, used for Gemini. The upper stage is 29t wet, 2.4t dry, and Gemini (payload) is 3.8t. Thrust is 45.4 tonnes force (444.82kN). Naively we'd assume (and this is how it performs in KSP) that burnout TWR is 45.4 / (2.4+3.8) = 7.323 Gs. However, with the 1% residuals (guess), burnout TWR is actually, in real life, only 45.4 / (2.4 + 3.8 + (29-2.4)*1%) = 45.4 / (6.2 + 0.266) = 7G.

That also means that delta V in real life will be less than KSP: In KSP, the simple rocket equation gives you 316s [isp] * 9.80665 [g0] * ln((29+3.8) / (2.4+3.8)) = 316 * 9.80665 * 1.666 = 5162m/s. Counting the residuals, however, the natural log yields 1.624, so delta V drops to 5032m/s.

On a large first stage / small upper stage rocket like Thor-Delta, however, that could mean the difference between a 9G burnout and an 11G burnout for the first stage, though...

Modeling residuals is not something we've attempted yet, both because there would be no easy way to tell MJ or KER about it, and because there's enough other unrealities that make life harder than real in KSP-RO that we think it's safe to leave one unreality in that makes things easier. :]

Why couldn't you pseudo-model residuals by making the dry tank mass a bit higher?

If your burnout TWRs are too high, rather than MOAR BOOSTERS, try MOAR STAGES. Going to a three-stage vehicle might let you have peak TWRs of only 4G each, whereas a two-stage version might peak at 8 in both cases.

That's exactly what I did last night to finally get a satellite into orbit. I used those procedural SRBs. I didn't even need to adjust the throttle on my stages, the TWR remained "reasonable" through all of them. Thank you and all the other modders for helping to make KSP fun again, I needed something challenging. I can't wait till I get experienced enough with these mods to send a manned mission to the Moon or Mars.

Also, finally, and this is just a guess, but--what do you consider reasonable TWR? Often people coming from KSP think you should launch at 2Gs, and your upper stages should be just as high thrust. Try a lower stage that gives you 1.2 on the pad (sea level TWR, not Vac TWR) and an upper stage that starts at no more than 1.0 in vacuum (if you have delta V to spare, so you can loft high, or you're going high anyway like to >2000km orbit, your upper stage can start with a much lower TWR). Consider that the EELVs (Atlas V, Delta IV) have upper stages that start around 0.2 TWR! Now, that's optimized for geostationary launches, but even going to LEO a starting TWR of 0.6 or 0.7 is totally fine if you loft a bit high and circularize after apogee (Saturn IB is an example of this approach: a long-burning high-energy upper stage with a low TWR).

No, I've been launching with a fairly low TWR (like 1.3) and using reasonably low TWRs on my upper stages (like 0.5-1). Well, I WANTED to launch with TWRS like that, but a lot of the problems I was running into was just the limited selection available of engine thrusts, which I solved with the expanded/rebalanced stock engines mod.

[sashan]

Are there any guidelines about fuel tank sizes, masses etc? I want to make an config for one mod, but it's extremely tedious job to calculate every volumes, mass fractions etc. from scratch.

Also, why is the deployable radiator listed as non-RO?

[jandcando]

Are there any guidelines about fuel tank sizes, masses etc? I want to make an config for one mod, but it's extremely tedious job to calculate every volumes, mass fractions etc. from scratch.

Also, why is the deployable radiator listed as non-RO?

Anything that doesn't have a RO module is automatically listed as non RO. So that deployable radiator has no RO config. I'm not really sure why we would need radiators as this project currently stands, though.

[Starwaster]

Anything that doesn't have a RO module is automatically listed as non RO. So that deployable radiator has no RO config. I'm not really sure why we would need radiators as this project currently stands, though.

Long term storage of cryogenic propellants. Example: Nuclear propulsion stage travelling to Mars. Using hydrogen as the propellant, the tank will completely boil off before you reach Mars.

(given that RF has alternate propellants, a better choice might be ammonia or even methane...)

[sashan]

Well, methane is nice but in KSP, everything should be done the hard way.

But I guess it still works even if it has no RO config? Small radiator has one. It has no texture tho... But that's another story. I am actually not that far away as to test them - I'm still working out the best ascent curve for my rocket.

Btw, as for engines - AIES gives a decent selection as well. The models are a little bit inaccurate inside and at the lower edge of the bell, but still looking good. They also have a very nice set of probe bodies and accessories as well as awesome lander legs. There's no smokescreen config tho, which I am planning to fix.

[-Velocity-]

Thanks again for this compilation of mods. There are so many changes that I'm forced to do a graduated series of ever more complex missions- just like real life! I have to learn what it takes to keep Kerbals alive in space, for example. I just can't go straight to the Moon/Mun or Mars/Duna like I can in stock. I built my first manned spacecraft last night, but I had to fly it on an unmanned mission first just to ensure that all the systems worked... I had no idea if I had big enough chutes, for example, or if the heat shield would hold for the re-entry trajectory I was following.

Now, Jeb's in orbit, and I'm learning how Kerbals consume resources in space and at what rate. I'll need to know this to start my Moon program. Once I start the Moon program, I'll have to first launch an unmanned flight that tests the heatshield and parachutes- just like with Orion- then, I'll probably have my Kerbals do a test flight in LEO to make sure that the craft can biologically support them for the whole duration of a lunar mission, then I'll have to do a lunar orbital mission, and finally, I can do a landing mission!

Once I start getting ready for Mars, it will be a whole new deal, I'll probably have to build a space station so I can study the life support systems/recycling I'll need for very long duration flights.

Anyway, it's just really cool how a little bit more realism has re-energized my passion for KSP, made the game so much more realistic, and forced me to follow a more realistic path of learning and development. Thanks again to all the modders.

[sashan]

Is it possible to rescale IVA's? The misaligned windows don't look good.

Also, how fast should the boiloff be? I've lost not a single unit oh LOX+LH2 during by coast to circularisation burn.

Edited March 14, 2015 by sashan

[O Nerd]

Ehrm... I made orbit with about 8400 Delta-v. What the heck.

I guess I'm way too good at flying rockets. xD (jk)

[Motokid600]

Ehrm... I made orbit with about 8400 Delta-v. What the heck.

I guess I'm way too good at flying rockets. xD (jk)

Mustve had a high twr.

[Kitspace]

I am also asking for some time already about the actual possibility of rescaling the interiors or completely getting rid of the exterior model parts on the interior view because the issue can go up to completely obstructing the windows on the rescaled pods.

[Dawnstar]

I'm having a great time with this collection of mods - it's renewed KSP for me and made it a bigger game in multiple ways.

I'm also experiencing some glitches and even frustrations, and perhaps should share them. Hoping this is the right thread!

Mods active: RSS, RO, all required and recommended, and just a few of the suggested. Orginally, I used our solar system, but currently am using a 10x scaled Kerbol system instead - see below. Running in career mode, but not using the RO career mode progression. So, no, I'm not asking for your help with any crashes or graphical issues - I'm on my own there.

1. When I installed this mod, I must have done something wrong because Earth had Earth's biomes and Kerbin's height map. After failing to understand why, I replaced the real solar system with a 10x Kerbol system. Now I have a Kerbin with Kerbin biomes and Earth's altitude map. Yeah, I really do have a South America-shaped ocean south of the KSC.

How do I replace a height mesh for a specific planet, please?

2. I'm appreciating the nerf to reaction wheels, but am not understanding the thrust nerf to RCS units. There are a lot of these units cluttering my parts list, but none of them produce enough thrust to control even a medium-sized craft without exploding the parts count. They're also all super-tiny, which is nice for tiny satellites, but suboptimal for a manned Munshot.

Am I missing a way (other than main thrusters) to control the attitude of my larger vessels without adding too many parts - and therefore making my game sluggish and even crash-prone?

3. Just recently, I discovered that this mod collection, with all required and recommended mods installed, but none of the suggested, doesn't really give you the engines to do a whole lot more than humans have as of 2015+early Mars/Duna manned missions. Which is unacceptable! I want to do a LOT more than that! So I removed near future engines (RSS just turns all the engines almost into duplicates, and nerfs the thrust without giving the player a way to compensate without consuming a lot of gameplay time). I than added Atomic Age, which means getting several thrusters of various sizes that deliver 500-950 ISP and acceptable TWR, and modded in a small-craft LH2/LOX engine based on the Space Shuttle Orbiter. Finally, the two ion engines left after removing NearFuture got modded to be 500-1000x the RO thrust, 50-100x the engine mass, and 100-250x the electricity consumption. Plus a substantial price drop for both engines and xenon fuel tanks. Yeah, the realism advocates may point out that the RO engines correctly mimic real-world engines but I'm not going to thrust for half a year to get an orbital insertion, or pay upwards of 10,000x the funds per unit of acceleration as I do for any chemical rocket. Sorry, both are a no-go in a game environment. That said, I'm also not going to use Ion engines as Minmus hoppers or Eve flyers! (and, with Kerbin/Earth TWRs for these units that are still less than 0.1, the temptation for such abuse is resistible).

Suggestion: Ignore all my changes - they're not important. What IS important is that this mod collection come out of the box with engines that permit full manned exploration of, and base-building on, the whole planetary system (whether our solar system or a 10x Kerbol system), at an affordable cost in funds, and in a reasonable amount of gameplay time.

[Dawnstar]

I'm having a great time with the RO/RSS collection of mods - it's renewed KSP for me and made it a bigger game in multiple ways.

I'm also experiencing some glitches and even frustrations, and perhaps should share them. Hoping this is the right thread!

Mods active: RSS, RO, all required and recommended, and just a few of the suggested. Originally, I used the RSS solar system, but currently am using a 10x scaled Kerbol system instead - see below. Running in career mode, but not using the RO career mode progression. So, no, I'm not asking for your help with any crashes or graphical issues - I'm on my own there.

1. When I installed this mod collection, I must have done something wrong because Earth had Earth's biomes and Kerbin's height map. After failing to understand why, I replaced the real solar system with a 10x Kerbol system. Now I have a Kerbin with Kerbin biomes and Earth's altitude map. Yeah, I really do have a South America-shaped ocean south of the KSC.

How do I replace a height mesh for a specific planet, please?

2. I'm appreciating the nerf to reaction wheels, but the thrust nerf to RCS units is giving me heartburn. There are a lot of these units cluttering my parts list, but none of them produce enough thrust to control even a medium-sized craft without exploding the parts count. They're also all super-tiny, which is nice for itty-bitty satellites, but suboptimal for a manned Munshot.

Am I missing a way (other than main thrusters) to control the attitude of my larger vessels without adding too many parts - and therefore making my game sluggish and even crash-prone?

3. Just recently, I discovered that this mod collection, with all required and recommended mods installed, but none of the suggested, doesn't really give you the engines to do a whole lot more than humans have as of 2015+early Mars/Duna manned missions. Which is unacceptable! I want to do a LOT more than that! So I removed near future engines (RSS just turns all the engines almost into duplicates, and nerfs the thrust without giving the player a way to compensate without consuming a lot of gameplay time). I than added Atomic Age, which means getting several thrusters of various sizes that deliver 500-950 ISP and acceptable TWR, and modded in a small-craft LH2/LOX engine based on the Space Shuttle Orbiter. Finally, the two ion engines left after removing NearFuture got modded to be 500-1000x the RO thrust, 50-100x the engine mass, and 100-250x the electricity consumption. Plus a substantial price drop for both engines and xenon fuel tanks. Yeah, the realism advocates may point out that the RO engines correctly mimic real-world engines but I'm not going to thrust for half a year to get an orbital insertion, or pay upwards of 10,000x the funds per unit of acceleration as I do for any chemical rocket. Sorry, both are a no-go in a game environment. That said, I'm also not going to use Ion engines as Minmus hoppers or Eve flyers! (and, with Kerbin/Earth TWRs for these units that are still less than 0.1, the temptation for such abuse is resistible).

Suggestion: Ignore all my changes - they're not important. What IS important is that this mod collection come out of the box with a tech tree and with engines that permit full manned exploration of, and base-building on, the whole planetary system (whether our solar system or a 10x Kerbol system), at an affordable cost in funds, and in a not-too-exorbitant amount of gameplay time.

4. So, what's the deal with all the super-heavy AI pods, even at highest tech? There are two AI pods I still use in RO, and they mass 0.18 and 0.05 tons. Right now, the rest are just clutter in the parts list, and I'm hoping to learn of a good reason to use them as-is before I chop their masses down closer to their stock values.

[O Nerd]

Mustve had a high twr.

And how does that reduce the amount of Delta-v needed? Wouldn't a higher TWR mean higher drag losses?

[NathanKell]

|Velocity|: We certainly could! But as above, so far I've felt that there's enough other things that make it harder to reach orbit than in real life that the bit extra delta V worked out ok. I think we might reasses after KSP 1.0 comes out, though, and it's a good time for more savebreaking changes.

Congratulations on your orbit, and glad it's fun for you!

Ah, apologies for assuming LOLSOKERBAL when it wasn't there. Good work.

sashan: It's technically possible, but no one's had time to sit down and write the plugin.

O Nerd: drag losses are on the order of 100m/s. Gravity losses are on the order of 1800m/s. Even if you triple drag losses from a high-speed ascent, if it cuts gravity losses by 17% you're ahead. And since gravity losses are dependent on time to orbit and time spent with little horizontal velocity, you can see how a high TWR takeoff can massively decrease them.

Dawnstar: First, welcome to the forums! (And to RO.) Glad it's fun for you!

Second, you might want to edit one of your posts to consolidate, and delete the other; looks like when the first post didn't appear you reposted, and a moderator approved both? (Every user's first few posts are moderated, after which they're able to post immediately unless re-queued due to infractions).

1. Sounds like you missed the big installation instructions bit in the RSS Opening Post about needing a texture pack. (We recommend using CKAN for this reason amongst others; it makes installation far easier.) My suggestion is to nuke both the RealSolarSystem and RSSTextures folders and install both RSS and a texture pack fresh from the Real Solar System OP.

2. Recall that the 45 ton Apollo spacecraft stack (CSM+LM) was controlled using four .45kN quads on the Service Module (and a few even smaller ones on the LM). The standard size RCS block is that size, so you certainly shouldn't need more than 4 of them for vessels < 30 tons. One thing RO teaches you is patience (you burn RCS a bit to start turning, then wait until you get close to done turning and kill rotation).

3. If you're intent on playing career, then without RP-0 it's not going to work. It's that simple. I recommend ditching RO and using the RF Stockalike configs if you want to play a KSP-style career.

4. Uh...use smaller probe cores? You have a lot you can use, and you can use proc fairings to hide them anyway if their small size would look weird. The large stackmount probe cores are modeled on, well, the large (and heavy) avionics rings used early on; once avionics started getting light, it also got small.

[Starwaster]

2. Recall that the 45 ton Apollo spacecraft stack (CSM+LM) was controlled using four .45kN quads on the Service Module (and a few even smaller ones on the LM). The standard size RCS block is that size, so you certainly shouldn't need more than 4 of

I don't think CSM+LM used the ones on the LM. It wasn't even powered up until lunar orbit, was it?

[O Nerd]

O Nerd: drag losses are on the order of 100m/s. Gravity losses are on the order of 1800m/s. Even if you triple drag losses from a high-speed ascent, if it cuts gravity losses by 17% you're ahead. And since gravity losses are dependent on time to orbit and time spent with little horizontal velocity, you can see how a high TWR takeoff can massively decrease them.

Thanks for your clarification . But if gravity losses are so much of an issue, why aren't there more rockets with high TWRs?

Edited March 14, 2015 by O Nerd

[sashan]

Because burning up on ascent is an unpleasant concept, believe me. I did it like 6 times yesterday, in process of fine-tuning my first RO rocket. Even still the reentry effects were showing sometimes, despite the low temperature Deadly Reentry was giving off.

Also, too high TWR in the beginning makes it impossible to perform gravity turn without flipping - you need crazy angles of attack to turn fast enough. I usually start with TWR around 1.4-1.6.

[Motokid600]

Thanks for your clarification . But if gravity losses are so much of an issue, why aren't there more rockets with high TWRs?

Sorry I meant to elaborate earlier. I think it's Nathan who taught me this too. Why don't all rockets use higher twr? Well they do iirc. unmanned rockets will have a 1.7 or so sea level twr. Manned rockets are much lower at around 1.2 - 3.

Because it's all about the twr of the stage just before burnout. A rocket with a 1.7 sea level TWR may have a 6+ twr before burnout. Thats alot of g's. A payload may only be rated at 6 or so g's. Any more and the structure will fail. You have to understand that not only is your rocket getting lighter as it burns fuel. The engines are also thrusting harder as well.

If you've ever tried for SSTO rockets in RSS this is a problem if you can't shut down engines. I've crushed a few payloads in my RSS days.

Manned rockets are even harder. They are SLOW and have a harder fight with gravity. But the end result is a tolerable final TWR for the people on board. I believe the Saturn V first stage and second both cutoff it's center engine before burnout at around 5g's to keep that from getting any higher.

Edited March 14, 2015 by Motokid600

[NathanKell]

Because rockets aren't optimized for lowest-delta-V-to-orbit, they're optimized for cost. And/or putting the most payload possible into orbit on the engines one has available without adding more engines. Fuel is cheap, and you gain more payload by accepting a lower TWR (and much more delta V from more fuel) than your approach.

Also, aerodynamic stresses and aerodynamic heating are tough. It's much less dangerous to fly a gentle ascent, and it's better to be somewhat unoptimized than have a sizable portion of your launches fail due to heat or stress (a gust of wind might disalign the stack and then boom, if Q is that high).

[sashan]

IRC that was just barely under 4G's.

That's also the reason why Vega has 3 relatively small solid-fuel stages. Solids give pretty nice fuel mass fraction, making TWR go crazy in the end.

[O Nerd]

Oh, I get it. I did not take aerodynamic stress and G tolerance into account.

You guys seem to be very used with RL stuff. Not my case though. -1 point for me

Also, sashan, I know that feeling.

[draeath]

Atomic Age doesn't seem to be in CKAN. The forum page has two download versions... which would be more appropriate to use with RO? The single-fuel mode of the full package sounds right, but the tank switcher mod seems redundant (and might actually interfere with RealFuels?)

EDIT: also, the link for atomic age is bad in the OP. drop the SSL, and slap on the forum subdomain