How to troubleshoot my rockets? How to build an intuition?

[NK_]

So I just started playing the game, and while i have fun, i still have some problems. And one of the biggest sources of frustration is that i don't know how to fix my issues, besides trial and error.

So i have played the first orbiting mission, which also kind of explains customization of engines. It all worked fine and i understood it, but then i tried building my own rocket to get a small satellite into otbit. I used the numbers from the tutorial as a guidline as far as i remembered them, but the whole rocket doesn't feel balanced. Some issues i noticed in-flight:
-Boosters were quite a bit too strong
-2nd (of 3 + deploying payload) stage was quite powerful and lasted too long
-I had no chance stabilizing an orbit with my 3rd stage, which i tuned for vacuum

I fixed it as far as i could, and i got close to an orbit by banking way earlier and harder than in the tutorial mission, like 55 deg at 6k altitude, and by further forcing the rocket to gain horizontal speed rather than using prograde (My guess is nozzle diameter too wide? But I reduced it already).

I was surprised that there were such big differences and that i did not even get to establish an orbit, as i was generous with fuel and did not plan as tight as the tutorial did.
So, my questions are: Can someone more experienced tell me what is wrong with my rocket? Do i make an obvious mistake? And: How to get better with this? Except, of course, to keep playing and trying. I tried to google my questions, but for specific problems there seem to be not many sources. Are there great resources i have overlooked?
TIA

P.S. Here are screenshots of the configuration https://imgur.com/a/G0vsZuK

[[BLK] Telu]

I know, there is barely any source on internet who talk about it. Looks like nobody really know how to do it properly and just put random number to get in orbit.

Apparently, you need to respect TWR to be able to make it.

The idea is to look at which altitude will go your first stage (with the payload of the two other stage + the deploying payload), tweak the engine of the second stage in consequence to get the max deltaV for the starting altitude where it will light up.

Then, for the overall flight, you really need to use the "go to apoapsis" feature on the navball.

The goal is to reach 3300m/s like in the tutorial, it's the minimum speed for being in orbit. (A guy said to let a vessel in orbit to know the end velocity needed)

It's not easy like in KSP. Some guys tried to help me, i made a guide about it. I think it work but between what the guys said and the reality, it's day and night.

The end payload weight is really important. It's what change the size of the rocket. There is also the atmosphere who scrumble things up and make the math wrongs in this game. You really need to tweak your engine by testing every stage to see where it go.

I think you did everything right in your screenshot. Can you give me your end velocity at the end of the flight ?

Do your 1st Stage turn off at 6km ?

You also don't want to go too fast with your boosters, because of atmosphere. The best is to reach the end velocity of the 1st Stage in the tutorial.

Note : It's better to share your rocket on the Juno Website, so we can try it.

[toinkertoy]

First off I wouldn’t go with a three stage to orbit rocket! I know the tutorial craft is built that way but that’s because of the engines available in a career game at the point that contract is given (only solid fuel who’s engines don’t gimble and pressure fed engines that in the actual world have never been used exclusively to launch a rocket into space) get the gas generator cycle engine for your first stage and build a two stage to orbit rocket.

Too some extent you will have to just test launch you’re new rocket designs and don’t expect to get it perfect the first time. You’ll want between 3600 and 4000 dv in the booster and 1300 to 900 in the second stage. It’s difficult to give a specific number because a lot also depends on your flight profile and getting a proper gravity turn going. Just like in the tutorial you’ll want to start by going vertically then at around 1000 meters or so conduct a pitch over maneuver! At that point your direction of travel (green arrow) will begin to turn towards your new heading (white arrow) when they meet you then lock heading to track the green arrow and the rocket should conduct a smooth gravity turn.

The real trick is getting that gravity turn so that it is not too steep but also not so shallow you end up going horizontal when you’re still in atmosphere (and won’t ever achieve orbit). The key here is the thrust to weight ratio (TWR). If TWR is too high the gravity turn will be slow and you’ll end up in a ballistic trajectory like a mortar. To low and the gravity turn will be too fast and you’ll level out while still in the atmosphere! So test out the booster, and see how it turns …. Then adjust TWR on the engine accordingly based on weather it turns too quickly or too slowly!

ADD: in addition you can also adjust a bit while in flight by throttling down (lowering TWR) at certain points to adjust the gravity turn.

[toinkertoy]

Originally posted by BLK Telu:

I know, there is barely any source on internet who talk about it. Looks like nobody really know how to do it properly and just put random number to get in orbit.

Lolololololololololol

Barley any resources on the subject, yes. That no one playing really knows how to build a rocket .... well that's just laughable to be honest!

I promise you none of us are just "putting in random numbers" to build a rocket, we know very well how much dv a stage should need and what TWR is required!

Now there is always going to be some variation in the numbers for the reasons i mentioned above (your exact launch profile, orbital altitudes, inclination, etc.) so you may build a booster with 4000 dv and end up only needing 3870. Small discrepancies like that are to be expected without having a room full of engineers sitting behind you while you're at your computer (and why test flying your rockets is a good idea just like with any craft). But once you actually get a handle what all those parameters mean it's not really guessing game anymore, just a mater of constructing the appropriate rocket for the appropriate mission and payload size.

[toinkertoy]

There’s a lot more I could add here about engine performance and how to tweek it …. But it really sounds like from your description (having to bank harder then the tutorial, use of “too strong” boosters) that really your thrust to weight ratio was too high to use the same flight profile that the tutorial used.

About boosters: they can be quite difficult to figure out. And this is because of how dramatically they change your crafts TWR once they’re expended and jettisoned. You really are gonna want to have your liquid fueled engines start at something like 45-55% until the boosters burn out then throttle them up to maintain TWR.

[[BLK] Telu]

Originally posted by toinkertoy:

Originally posted by BLK Telu:

I know, there is barely any source on internet who talk about it. Looks like nobody really know how to do it properly and just put random number to get in orbit.

Lolololololololololol

That's true. People talk a lot about hardware like engine and all but most none of them is talking about how to build a rocket. Even on reddit. It's a pain in the butt to find real information.

I start to believe than they are doing random stuff. I challenge you to find me a youtube video where the guy know what is he doing and explain why he make those choices.

[[BLK] Telu]

A minority know how to do it. But the majority is just bringing random stuff to make it happening. It's not laughable, it's the truth. I'm still waiting for the video of a guy who show why he choose those settings to make his rocket successful. It doesn't exist.

it's maybe not a guessing game, i never said it was a guessing game. The player can really tweak his rocket to make it successful if he get the knowledge (without the need of becoming an engineer in rocket science). But the majority dumped the manual and nobody really manage to explain how to run a rocket.

So, at the end of the day, it's just the same. People are guessing to be able to make it happen.

[[BLK] Telu]

I think i know why there is no video tutorial (KSP have ton of tutorial video, Juno should be the same). Because the majority doesn't know what they are doing. They can't explain what they don't know. And the minority who know is not really interested into making video on internet. I don't say they are selfish, i say than it's not their thing (I'm also not interested into making videos).

Last time i asked a guy why he choose those settings, he just answered me to just "copy his rocket". Great, thanks ... !

But, anyway, just look at the guide on steam or even the wiki of the game. Nothing is about making a rocket from top to bottom.

Edit : Man, stop playing dumb, you know what i mean. Everything is not black or white. You know than i wasn't including everyone in my speech. Stop taking personal my statement. There is no contradiction, you just don't understand what i wrote. We know, you are so awesome in Juno. We don't care, we don't talk about you, we talk about the others !

If people don't explain what they are doing it's because they don't understand what they are doing else they will explain it ! That's a fact. If they knew what they were doing why are they unable to explain it then ? You are the first struggling to explain how to build a rocket properly in this game, you always go high into engineer/nasa team non-sense in an arcade game.

[NK_]

Originally posted by toinkertoy:

First off I wouldn’t go with a three stage to orbit rocket! I know the tutorial craft is built that way but that’s because of the engines available in a career game at the point that contract is given (only solid fuel who’s engines don’t gimble and pressure fed engines that in the actual world have never been used exclusively to launch a rocket into space) get the gas generator cycle engine for your first stage and build a two stage to orbit rocket.

Too some extent you will have to just test launch you’re new rocket designs and don’t expect to get it perfect the first time. You’ll want between 3600 and 4000 dv in the booster and 1300 to 900 in the second stage. It’s difficult to give a specific number because a lot also depends on your flight profile and getting a proper gravity turn going. Just like in the tutorial you’ll want to start by going vertically then at around 1000 meters or so conduct a pitch over maneuver! At that point your direction of travel (green arrow) will begin to turn towards your new heading (white arrow) when they meet you then lock heading to track the green arrow and the rocket should conduct a smooth gravity turn.

The real trick is getting that gravity turn so that it is not too steep but also not so shallow you end up going horizontal when you’re still in atmosphere (and won’t ever achieve orbit). The key here is the thrust to weight ratio (TWR). If TWR is too high the gravity turn will be slow and you’ll end up in a ballistic trajectory like a mortar. To low and the gravity turn will be too fast and you’ll level out while still in the atmosphere! So test out the booster, and see how it turns …. Then adjust TWR on the engine accordingly based on weather it turns too quickly or too slowly!

ADD: in addition you can also adjust a bit while in flight by throttling down (lowering TWR) at certain points to adjust the gravity turn.

OK, so first let me thank you for taking the time to write such a detailed response. I built a new rocket, trying to implement as much of your advice as possible (https://www.simplerockets.com/c/v14DRv/Orbit) but i still got some issues.

While the total dv should be enough with 4200 (should'nt it?), i still don't have the power to get to an orbit. I didn't get enough dv out of the boosters, as obviously the mass increases with bigger fuel tanks, resulting in a minimaly bigger dv. Do I need to inflate the boosters to a giant size? Then, the 2nd stage has more power than you suggested, simply because... yeah as i'm writing this i realize i could just make the tank smaller. Idk what i was thinking, but this shouldn't cause a problem i think. I turned 70deg at ~2500m agl by teh way, it achieved best results for me.

So it seems like my main problem is getting more dv out of my boosters, maybe the missing 800m/s out of the total dv make me not getting to an orbit. And if you see any anomalies with my build, please point them out. Chances are, i didn't do it on purpose.

Oh yeah, one more quiestion: I set the fuel profile of my solid motors to "ramp down", my reasoning behind it was to help my rocket to overcome initial high gravity with lots of power early. Is that correct or do I better stick with the basic profile?

[NK_]

Originally posted by BLK Telu:

I know, there is barely any source on internet who talk about it. Looks like nobody really know how to do it properly and just put random number to get in orbit.

Apparently, you need to respect TWR to be able to make it.

The idea is to look at which altitude will go your first stage (with the payload of the two other stage + the deploying payload), tweak the engine of the second stage in consequence to get the max deltaV for the starting altitude where it will light up.

Then, for the overall flight, you really need to use the "go to apoapsis" feature on the navball.

The goal is to reach 3300m/s like in the tutorial, it's the minimum speed for being in orbit. (A guy said to let a vessel in orbit to know the end velocity needed)

It's not easy like in KSP. Some guys tried to help me, i made a guide about it. I think it work but between what the guys said and the reality, it's day and night.

The end payload weight is really important. It's what change the size of the rocket. There is also the atmosphere who scrumble things up and make the math wrongs in this game. You really need to tweak your engine by testing every stage to see where it go.

I think you did everything right in your screenshot. Can you give me your end velocity at the end of the flight ?

Do your 1st Stage turn off at 6km ?

You also don't want to go too fast with your boosters, because of atmosphere. The best is to reach the end velocity of the 1st Stage in the tutorial.

Note : It's better to share your rocket on the Juno Website, so we can try it.

Thaknk you for writing such a detailed response, it helped me a bit so far. I have managed to get to orbit with some tweaks to my 3 stage rocket, but i didn't feel confident yet, more like i randomly changed the numbers and somewhen it barely worked out.
I had my boosters twr at 2.5, which is quite on the high side but shouldn't cause friction problems (or does it?). Somewhere i read takeoff twr >1.5 and space maneuvering twr > .75, so that's what i tuned my new rockets twr after.

Unfortunately i dind't save the design i took screenshots of, but i built a new rocket after the 2 stage design toinkertoi suggested. You can find it here: https://www.simplerockets.com/c/v14DRv/Orbit and i explained my issues with it in another comment.

[toinkertoy]

Ok yes I was first gonna note that the link didn't work (or was blocked) but i got it too it and you fixed it in the second post so...

So I read your first stage as having 2.8 km/s dv. That won't be enough it needs prolly 3.6 to 4.0 dv. Second stage looks sufficient at 1.8 (assuming first stage dv has around what i listed above). Perhaps I wasn't clear about that, I meant 3.6 to 4.0 dv in the first stage PLUS the 0.9 to 1.3 in the second stage (so total around 4.9 to 5.3).

TWR looks good (a bit higher then I usually go for which is 1.63 but it should work)

Can you make the side interstages smaller? This is not a Major issue I think but they're yuge!!! and you could save some weight (getting better dv) by making em a bit smaller. But if you like the look of it this isn't a must do.

Overall it's an interesting design, one I've never tried, because it has solid fueled booster AND a solid fueled core! I usually go with a liquid fueled engine on the core so it can gimble and help steer the rocket AND I can throttle the engine and better control my TWR.

How do you steer this rocket? Is it sluggish to turn with the solid rocket engines that don't gimble?

Also it looks like there's about as much fuel in the boosters as in the core stage. Do they burn out about the same time? (withing a 2-3 seconds). If so you might consider getting rid of the side interstages and just attaching the boosters to the core directly! The advantage of boosters is they burn out before the core and you can dump the weight (you may already know this but just in case) it's an advantage you don't get if they burn the same length of time!

[NK_]

So,
I just managed to get orbit with this https://www.simplerockets.com/c/GG0YQ1/Orbit design on the 2nd attempt. I steered different the 2nd time, pitching more aggressive and earlier. Does that make a big difference? I figured it wouldn't, as long as your boosters give you an apoapsis somewhere between your targeted apoapsis and the atmosphere border, but that you just need the raw dv to get out of the atmosphere.

Also, I noticed that i can increase my boosters dv by increasing their size individually rather than multiplying them (with higher symmetry). That seems to be my core problem, i cannot get enough power into my boosters on the first launchpad with its size restrictions.
Also, i wanted to build a rather small rocket (you know, to function somewhat profitably. My working design basically cost as much as i got as a reward for the orbit mission. That gotta go cheaper doesn't it?).

The side couplers are simply that big because i dodn't know i can adjust them (my rocket is quite small in diameter, its the couplers standard size). The boosters are distributed like that for no reason, i made them the same size so they burn simultaniously and i can decouple them all at once, before firing my main engine. I always activate my engine after the boosters ran out of fuel, is that wrong?

The design got those flaps (because the very first tutorial did it that way, so...) but my new one doesn't and it's still steerable. Idk how, maybe the game isn't too realistic here. All i can say is that it works.

After all it looks like my rocket doesn't have enough dv. That's the main problem if i understood you right, to know how much dv an action approximately takes (like escape atmoshere and get to orbit, then later line up apoapsis with moon, get into moons orbit, safely land on moon and stuff) and plan your stages accordingly. Then balance the other things around (exit pressure, twr, efficiency etc.)

[toinkertoy]

Ok I test flew it!

So definitely not enough power (delta-v) in the first stage, ramp that up quite a bit to 3.6 - 4.0 km/s

It steers ok at first, but then gets very wobbly! I think this is because the only mechanism it has to steer with is the gyroscope. This is one of the big problems with using ALL solid fueled stages in the game, those engines don't gimble and so controlling your heading is difficult. Consider a liquid fueled engine on the core tank even if it's a pressure fed genome engine.

The core tank burns out before the boosters! So having detachable boosters really has no advantage. Consider making the core tank bigger (longer, wider or both) so it burns longer then the boosters (the rocket needs more fuel/dv anyhow) or consider ditching the side interstages and attaching the the booster tanks directly to the core tank. They'll be treated as one single tank then and all engines will burn out at the same time (and you'll save some weight not having the interstages)

Also your second stage engine nozzle throat size is way too small (at 50%). That small a throat size is for vacuum optomized engines! If you burn them too at too low an altitude for too long they will get destroyed!

[toinkertoy]

Originally posted by NK_:

After all it looks like my rocket doesn't have enough dv. That's the main problem if i understood you right)

yes and that second rocket you posted (3.8 km/s dv) should have, and apparently did, do the trick!

[NK_]

Originally posted by toinkertoy:

Originally posted by NK_:

After all it looks like my rocket doesn't have enough dv. That's the main problem if i understood you right)

yes and that second rocket you posted (3.8 km/s dv) should have, and apparently did, do the trick!

I can't get there for the life of me, not within the size restrictions. The new design got barely more dv, but under 3k in the booster stage again. It reached orbit on a really tight plan again, i ended up with under 10% fuel in my 2nd stage. There must be something i'm overlooking. I want to give the boosters more dv, but i cannot.

Originally posted by toinkertoy:

Ok I test flew it!

So definitely not enough power (delta-v) in the first stage, ramp that up quite a bit to 3.6 - 4.0 km/s

It steers ok at first, but then gets very wobbly! I think this is because the only mechanism it has to steer with is the gyroscope. This is one of the big problems with using ALL solid fueled stages in the game, those engines don't gimble and so controlling your heading is difficult. Consider a liquid fueled engine on the core tank even if it's a pressure fed genome engine.

The core tank burns out before the boosters! So having detachable boosters really has no advantage. Consider making the core tank bigger (longer, wider or both) so it burns longer then the boosters (the rocket needs more fuel/dv anyhow) or consider ditching the side interstages and attaching the the booster tanks directly to the core tank. They'll be treated as one single tank then and all engines will burn out at the same time (and you'll save some weight not having the interstages)

Also your second stage engine nozzle throat size is way too small (at 50%). That small a throat size is for vacuum optomized engines! If you burn them too at too low an altitude for too long they will get destroyed!

Thanks for taking the time, i'm sorry that that one got outdated that fast haha. I ditched the design with boosters at the sides and core. I actually meant the engine of the 2nd stage to activate close to vacuum, so that's why i tuned it that way. That didn't work out obviously.

Also, i don't quite get you. Should I add a liquid fueled engine with the booster stage to make it steerable always? Does a rocket with more than one booster stages also fit the definition of a 2-stage-rocket, if it has one block of boosters and one liquid fueld engine?

E D I T:

Ok, so i buit my first rocket to consistently and comfortably reach an orbit (this abomination if you're interested: https://www.simplerockets.com/c/PX7Eei/fat-boi). It is a way simpler design than the other ones. With the previous ones (the very first mentioned and the one with 2 side boosters) i tried to go for traditional designs, with the new one i didn't give f*cks. I'm still not sure, why the slimmer version or the oneswith multiple boosters did not deliver enough dv. I mean, in reality they do, or do i grossly underestimate the proportions of boosters to engines in real rockets?

[toinkertoy]

Originally posted by NK_:

I can't get there for the life of me

Yeah I just barely got the second rocket into orbit but the first rocket you posted wasn't even close!

Originally posted by NK_:

not within the size restrictions.

Originally posted by NK_:

I want to give the boosters more dv, but i cannot.

Are these Pad restrictions in career mode? Sounds like you're stuck with Juno Village pad? I only ever launched 4 rockets from that pad, Ali pad is much better! With a bit of practice and memorizing the flight profile to a tee (or write it down) I think you can do the 5 min. to orbit using the tutorial rocket (think i did it in 4 min 56 seconds) or try this rocket I know it definitely can! just fly it on the same profile as the tutorial rocket.

https://www.simplerockets.com/c/Vyn26s/Droo-Orbit-CubeSat-Deployer-for-Career

That could be the major problem here. With the size limitations placed on Juno village pad you have to very economical with your design and stringent with the flight profile!

Originally posted by NK_:

Also, i don't quite get you. Should I add a liquid fueled engine with the booster stage to make it steerable always? Does a rocket with more than one booster stages also fit the definition of a 2-stage-rocket, if it has one block of boosters and one liquid fueld engine?

I guess I meant consider making the core tank Liquid fueled (with a liquid fueled engine) Really what I'm getting at is that gimbeling engines make it so much easier to steer the rocket (and I had some difficulty controlling your designs although not as much as I had feared). I kind of avoid solid fuel like the plague in this game because the engines do not gimble and it makes hitting your launch profile very difficult! Anytime I use solid fueled boosters they're always strapped to a core rocket that's liquid fueled with gimebling. engines!

I think strap-op detachable boosters are often called "0-stage". Certainly when I refereed to "3 stage" what I meant was 3 stages all on top of one another (like the Saturn V or tutorial rocket)

Originally posted by NK_:

So,
I steered different the 2nd time, pitching more aggressive and earlier. Does that make a big difference?

It can! You basically need to go two directions: up and laterally (parallel to droos surface). even small deviations can make a noticeable difference in performance. This is why steering the rocket is important for consistent launches.