Launching a 44t payload

[James M]

2 hours ago, Anonymous49 said:

my first booster only costs 6k each, over 2 minutes of burn time, 400kn thrust in vacuum, TWR of over 1.6.

Well there you go. The boosters you're currently using are the same cost with approximately one third of the power.

[Guest]

Nobody's said it but everybody's thinking it so I guess I might as well be the party-pooper. 

Caveat: The only wrong way to play KSP is the one where you're not enjoying yourself. So if you're having fun, ignore anything anyone else tells you to do.

That said, it sounds like you @Anonymous49 are more frustrated than having fun. So at the risk of being That Guy, here's a bit of advice you probably don't want to hear – but it just might end up saving your enjoyment of KSP. Right now you're struggling with a lot of different problems at the same time, and you're doing so in a situation which is already pretty complicated in and of itself.

So here's the advice.

Forget your 44 ton payload and multi-module space station. Ditch MechJeb. Take a deep breath. Then go back to first principles and learn the basics of spaceflight and efficient rocket design:

1. Study up on how to get to orbit easily and efficiently: what kind of craft you need, and how you need to fly it to get it there.
2. Apply that study by designing the cheapest, simplest rocket you can, that is (1) easy to fly, and (2) will get Jeb in a command pod to LKO and safely back again.
3. Fly Jeb to orbit, and back.
4. Repeat steps 2-3 until you can do it easily  every time, adjusting your design for every flight so it's a little better every time -- a little lighter, a little cheaper, requires a little less control input.
5. Then do the same for a Mun fly-by and Mun orbit.
6. Then do the same for a Mun landing and return. Still just Jeb in a single command pod, no fancy Apollo-style missions.
7. Then figure out how RV and docking works and do the same for that.

Once you get to this point, the game really opens up – you'll be able to build stations, go to Duna, drop a probe on Eve, set up a base on Laythe, go on a ski vacation on Vall, plant a flag on Eeloo, whatever you like. But you do need to get these core skills first: how to design efficient, controllable rockets, how to fly them efficiently, how to re-enter, how to land and return to orbit, how to RV and dock. MechJeb can be great to automate away busywork but you're doing yourself a disservice if you're relying on it as a substitute for learning to operate things manually. 

KSP will frustrate you, a lot, because you'll be trying to do something that you don't know how to do. I've been playing this for years and it still keeps throwing curveballs at me. The problem is that if you bite off more than you can chew, you'll be simultaneously struggling with a dozen different problems and won't know how to address any of them, and none of it will work until they're all solved. If you scale back your ambitions and start small, you'll be able to tackle the problems one by one, and when you hit them again in your more ambitious designs, you'll know what you need to do to fix them.

/end sermon

[Anonymous49]

23 hours ago, James M said:

Well there you go. The boosters you're currently using are the same cost with approximately one third of the power.

burn time?

[Guest]

13 minutes ago, Anonymous49 said:

burn time?

If you want them to burn longer, adjust the thrust limiter.

[Anonymous49]

22 hours ago, Brikoleur said:

Nobody's said it but everybody's thinking it so I guess I might as well be the party-pooper. 

Caveat: The only wrong way to play KSP is the one where you're not enjoying yourself. So if you're having fun, ignore anything anyone else tells you to do.

That said, it sounds like you @Anonymous49 are more frustrated than having fun. So at the risk of being That Guy, here's a bit of advice you probably don't want to hear – but it just might end up saving your enjoyment of KSP. Right now you're struggling with a lot of different problems at the same time, and you're doing so in a situation which is already pretty complicated in and of itself.

So here's the advice.

Forget your 44 ton payload and multi-module space station. Ditch MechJeb. Take a deep breath. Then go back to first principles and learn the basics of spaceflight and efficient rocket design:

1. Study up on how to get to orbit easily and efficiently: what kind of craft you need, and how you need to fly it to get it there.
2. Apply that study by designing the cheapest, simplest rocket you can, that is (1) easy to fly, and (2) will get Jeb in a command pod to LKO and safely back again.
3. Fly Jeb to orbit, and back.
4. Repeat steps 2-3 until you can do it easily  every time, adjusting your design for every flight so it's a little better every time -- a little lighter, a little cheaper, requires a little less control input.
5. Then do the same for a Mun fly-by and Mun orbit.
6. Then do the same for a Mun landing and return. Still just Jeb in a single command pod, no fancy Apollo-style missions.
7. Then figure out how RV and docking works and do the same for that.

Once you get to this point, the game really opens up – you'll be able to build stations, go to Duna, drop a probe on Eve, set up a base on Laythe, go on a ski vacation on Vall, plant a flag on Eeloo, whatever you like. But you do need to get these core skills first: how to design efficient, controllable rockets, how to fly them efficiently, how to re-enter, how to land and return to orbit, how to RV and dock. MechJeb can be great to automate away busywork but you're doing yourself a disservice if you're relying on it as a substitute for learning to operate things manually. 

KSP will frustrate you, a lot, because you'll be trying to do something that you don't know how to do. I've been playing this for years and it still keeps throwing curveballs at me. The problem is that if you bite off more than you can chew, you'll be simultaneously struggling with a dozen different problems and won't know how to address any of them, and none of it will work until they're all solved. If you scale back your ambitions and start small, you'll be able to tackle the problems one by one, and when you hit them again in your more ambitious designs, you'll know what you need to do to fix them.

/end sermon

i already did fly them myself, check how to get into a circular orbit. I finished step 1-5 myself before I even DOWNLAODED mechjeb. Unfortunately I crashed on the mun in step 6. I rendezvoused without mechjeb in "Rendezvous" but still I'm not good at docking

sometimes i use mechjeb as a backup when I forgot to bring a parachute when landing tourists, mechjeb knows how to do a landing burn.

in my first thread "Why my vessel crashes before reentry", I learned how to reenter and land manually

obviously with chutes

[Hotel26]

OK, to be constructive, you are asking a very difficult question about an extremely complex operation.  Bravo for taking it on.

I think the only person in the forum with any chance of helping you with this would be ... @Snark

Edited February 13, 2021 by Hotel26

[Anonymous49]

ok

i guess i will make tutorials instead

[VoidSquid]

Please be aware that the in game tutorial missions are still using the original parts (to be precise: the original part characteristics) which have been tweaked in the mean time, this can lead to false assumptions how things work in the game nowadays, see here:

https://bugs.kerbalspaceprogram.com/issues/27250

Edited February 13, 2021 by VoidSquid

[king of nowhere]

wait, i have an idea. you said you had still 1.1 twr, but with very complex crafts, the game gets unreliable. Ever since i launched the Dream Big, I had to do calculations by hand. so perhaps the game is telling you wrong and you don't have all the thrust you think you have?

then again, we all spent a lot of words on how exaggeratedly big that rocket is. it should still be capable of lifting 44 tons.

perhaps you are just tilting it too fast? maybe try to fly up for a longer time before turning the rocket.

another option is, perhaps you discard a command pod with a particular stage and then the rocket is commanded by a pod that is oriented backwards? this is quite common, and it screws up a flight. maybe take some screenshots of the moment when your rocket starts going bad (you can reload afterwards, we don't want you to lose more money just to give us a test)

[Snark]

On 2/7/2021 at 8:58 PM, Anonymous49 said:

Perhaps pictures can help

Thank you, the pics are really helpful!

So, verbose thoughts below, but they boil down to:

• I think your TWR in the early part of the ascent is way too high
• You may want to look at the aerodynamics of those clipped engines at the bottom of the radial boosters
• What does your ascent profile look like?

First... does this craft really have a TWR of 2.47 while sitting on the launchpad?  That strikes me as being way too high.  Having a TWR higher than 2 likely means that you're wasting too much of your dV fighting aerodynamic drag.  It also means you're lugging a huge amount of dead weight with all the engines you need to give you that high value.  Typical launchpad TWR for most players tend to range from around 1.3 up to 2.0 depending on one's design preferences.

Not only do you launch off the pad with that sky-high TWR, but it looks as though your first several stages also have extremely high TWR values.  Same concerns with aerodynamic drag and wasting dV on engine dead weight.

So, my first suggestion would be to get rid of a bunch of engines and lower your TWR values.  How low you go is up to you, but I'd strongly suggest that:

• your TWR on the launchpad should be no higher than 2.0
• each successive stage should have a lower TWR than the one preceding

To take my own play style as an example:  my typical rockets (both large and small) are usually about 3 stages to orbit.  The first stage is always exactly TWR 2.0 (I like to keep it consistent to make it easy to nail the gravity curve accurately).  Second stage is usually around TWR 1.0 or slightly above when it kicks in (by which time the rocket is already at a 45 degree angle), and third stage is generally fairly low, like TWR 0.5.   That's just me, of course-- nothing says you need to follow a similar approach, yourself.    It's worth noting, though, that my approach is on the high side of what most people go for, in terms of TWR.

Also... it was hard for me to tell exactly what you've got going  on with those engines on the radial boosters.  Are those... multiple engines all clipped together with a thrust plate?  What kind of engines are those?  Not totally sure how much I'd trust the aerodynamics on those-- the game can be odd when clipping things like that.  Maybe it's okay, but it may be possible that they're generating a lot more drag than you think.  Have you looked at the aerodynamic overlay (F12) to see how they're doing during the draggy part of ascent?

Finally, could you describe your ascent profile?  For example:

• When you reach 10 km altitude, how fast are you going and what angle from the vertical are you?
• When you hit a 45 degree angle from vertical, how fast are you going and what altitude are you?

[paul_c]

5 hours ago, Anonymous49 said:

i already did fly them myself, check how to get into a circular orbit. I finished step 1-5 myself before I even DOWNLAODED mechjeb. Unfortunately I crashed on the mun in step 6. I rendezvoused without mechjeb in "Rendezvous" but still I'm not good at docking

 

So you have the basics, you can launch and fly a rocket with ~1t payload (the command module). But you can't with 44t. Yes the same principles apply but you need to know those principles.

I'd suggest getting happy with flying say 3-5t into the same kind of missions and you'll get an idea of the kind of vehicle that can do that. 

[Spricigo]

4 hours ago, Anonymous49 said:

I finished step 1-5 myself

OH, well...I'd really like to not be "That Guy" either but can't be helped.

No, you didn't. The "easily and efficiently" part @Brikoleur mention is nowhere to be seen in what you had shown so far.  KSP is forgiving enough that you can do some glaring mistakes and still manage to get to orbit or get to the Mun. But if you don't learn to avoid those mistakes, don't take too long to be overwhelmed.

So, it seems you really need to take your time doing those basic things, looking for how other people do it and figuring out what you are doing different that is causing you trouble.  

[Anonymous49]

On 2/13/2021 at 9:40 PM, Snark said:

Thank you, the pics are really helpful!

So, verbose thoughts below, but they boil down to:

• I think your TWR in the early part of the ascent is way too high
• You may want to look at the aerodynamics of those clipped engines at the bottom of the radial boosters
• What does your ascent profile look like?

First... does this craft really have a TWR of 2.47 while sitting on the launchpad?  That strikes me as being way too high.  Having a TWR higher than 2 likely means that you're wasting too much of your dV fighting aerodynamic drag.  It also means you're lugging a huge amount of dead weight with all the engines you need to give you that high value.  Typical launchpad TWR for most players tend to range from around 1.3 up to 2.0 depending on one's design preferences.

Not only do you launch off the pad with that sky-high TWR, but it looks as though your first several stages also have extremely high TWR values.  Same concerns with aerodynamic drag and wasting dV on engine dead weight.

So, my first suggestion would be to get rid of a bunch of engines and lower your TWR values.  How low you go is up to you, but I'd strongly suggest that:

• your TWR on the launchpad should be no higher than 2.0
• each successive stage should have a lower TWR than the one preceding

To take my own play style as an example:  my typical rockets (both large and small) are usually about 3 stages to orbit.  The first stage is always exactly TWR 2.0 (I like to keep it consistent to make it easy to nail the gravity curve accurately).  Second stage is usually around TWR 1.0 or slightly above when it kicks in (by which time the rocket is already at a 45 degree angle), and third stage is generally fairly low, like TWR 0.5.   That's just me, of course-- nothing says you need to follow a similar approach, yourself.    It's worth noting, though, that my approach is on the high side of what most people go for, in terms of TWR.

Also... it was hard for me to tell exactly what you've got going  on with those engines on the radial boosters.  Are those... multiple engines all clipped together with a thrust plate?  What kind of engines are those?  Not totally sure how much I'd trust the aerodynamics on those-- the game can be odd when clipping things like that.  Maybe it's okay, but it may be possible that they're generating a lot more drag than you think.  Have you looked at the aerodynamic overlay (F12) to see how they're doing during the draggy part of ascent?

Finally, could you describe your ascent profile?  For example:

• When you reach 10 km altitude, how fast are you going and what angle from the vertical are you?
• When you hit a 45 degree angle from vertical, how fast are you going and what altitude are you?

i died before reaching 10km

srry if i was not really online in the past few days it was new year

[paul_c]

why?

ETA.....Why did you die? What specifically is happening, if the spaceship you built has the thrust and fuel to get to orbit? Is is pointing in the wrong direction? Are you trying to point it in the right direction? If not why not? (Do you know where you should point it, at various stages of the ascent?)

Edited February 15, 2021 by paul_c

[Snark]

33 minutes ago, Anonymous49 said:

i died before reaching 10km

I'm confused.  According to the problem as you've described it,

On 2/7/2021 at 8:58 PM, Anonymous49 said:

the first boosters started to jettison around 20 seconds into the flight and fell back to KSC harmlessly, around 30 seconds later, the second set of boosters fell back. Around 90 seconds into the flight, the last set of boosters jettisoned. The main rocket is still having a TWR of 1.1.

...By my count, that's 140 seconds of thrust, all at a TWR well over 2.0.  How could you possibly still be less than 10 km after all that?

[king of nowhere]

 

1 hour ago, Anonymous49 said:

i died before reaching 10km

srry if i was not really online in the past few days it was new year

 

On 2/13/2021 at 1:57 PM, king of nowhere said:

perhaps you are just tilting it too fast? maybe try to fly up for a longer time before turning the rocket.

 

another option is, perhaps you discard a command pod with a particular stage and then the rocket is commanded by a pod that is oriented backwards? this is quite common, and it screws up a flight. maybe take some screenshots of the moment when your rocket starts going bad (you can reload afterwards, we don't want you to lose more money just to give us a test)

have you checked on that?

i think the most likely option at this point is that your rocket is commanded backwards. that's the only thing that could tilt a rocket with so much thrust and gimbal.

we need INFORMATION!!!! PICTURES!!!! DATA!!!! even a full video of an attempted launch would be great

we have no idea what went wrong if you don't give us the means to figure it out

[paul_c]

I've given up guessing.

[Spricigo]

8 hours ago, king of nowhere said:

we need INFORMATION!!!! PICTURES!!!! DATA!!!! even a full video of an attempted launch would be great

Let me stress that.

@Anonymous49, there are many thing you may be doing wrong, that is why you need to give the better explanation you can about of what is happening. "I died before reaching 10km" tells us absolutely nothing about the chain of event leading to this result and, as a consequence, we are unable to know the issue (let alone pointing a solution).

If you want to give us a chance to help you provide at least:

• a picture of the entire craft in the VAB, fairings removed (so we can see what is inside) and deltaV readout expanded.
• a step by step explanation for how you are piloting it. Include every instance you use the directional control to adjust the direction, every activation/deactivation of SAS and RCS and the time of each staging event. Include the data (at least velocity and direction the craft is pointing) after each maneuver as well at 5km, 10km and 15km.

 

Well, I'm sure you will get a good answers if you provide good input. Is up to you now.

 

[king of nowhere]

so far, the most likely explanations that we can't rule out yet are....

- your payload is installed with an inverted probe core, and that inverted all your rocket guidance

- you have a tall payload without struts, leading to lots of wobbling, that eventually capsizes the rocket

- you have a lot of drag in front; united with a launch too fast, it overcomes the gimbaling and overturns the rocket because of aerodinamics

- mechjeb is programmed incorrectly

- you try to make a gravity turn way too early

- there are other problems with the rocket construction

 

[Anonymous49]

1 hour ago, king of nowhere said:

so far, the most likely explanations that we can't rule out yet are....

- your payload is installed with an inverted probe core, and that inverted all your rocket guidance

- you have a tall payload without struts, leading to lots of wobbling, that eventually capsizes the rocket

- you have a lot of drag in front; united with a launch too fast, it overcomes the gimbaling and overturns the rocket because of aerodinamics

- mechjeb is programmed incorrectly

- you try to make a gravity turn way too early

- there are other problems with the rocket construction

 

kinda right

13 hours ago, Snark said:

I'm confused.  According to the problem as you've described it,

...By my count, that's 140 seconds of thrust, all at a TWR well over 2.0.  How could you possibly still be less than 10 km after all that?

oh i thought it is 100, around 1km/s

[Dr. Kerbal]

I would go fro the Kerbal way, more boosters and in trust we trust.

[Snark]

14 hours ago, Anonymous49 said:

oh i thought it is 100, around 1km/s

Whoa.  Yeah, that's a problem.  If you're already going 1000 m/s when you're only 10 km of altitude, that's way too fast-- your TWR is much, much too high.  A more reasonable speed would be less than half of that.  300 m/s or 400 m/s at 10 km is typical.

You're wasting gobs and gobs of dV to aerodynamic drag by going too fast when you're still too low in the atmosphere.  You're also wasting a lot of dV by carrying way too much engine mass as dead weight.

Get rid of a bunch of engines.  Your first stage off the pad should be no higher than TWR 2.0 at the absolute most, and subsequent stages should generally start no higher than TWR 1.5 or so.

When you reach an altitude of 10 km, you should be going around 300 or 400 m/s, and tipped roughly 45 degrees from the vertical.  (Plus or minus a bit, depending on your TWR profile).

[paul_c]

"Reduce the thrust" was mentioned in post #3 (posts #1 and #2 were by the OP). The discussion got into the quantitative details of what a good TWR might be, on page 1. 

I suspect the whole concept of TWR isn't fully understood by the OP and hasn't been considered in further iterations of the rocket.

[Guest]

Hey @Anonymous49, have you redesigned your rocket yet? You should be able to do this with no more than 6 Skippers, total, if you're still averse to SRBs. Last I heard you had 23 on your first stage alone. It's really hard to be helpful if you're not taking any of the advice you're being offered, you know...

[Anonymous49]

19 hours ago, Brikoleur said:

Hey @Anonymous49, have you redesigned your rocket yet? You should be able to do this with no more than 6 Skippers, total, if you're still averse to SRBs. Last I heard you had 23 on your first stage alone. It's really hard to be helpful if you're not taking any of the advice you're being offered, you know...

I know, but i cannot be online on my computer this week i think, it was new year and i had to use ios instead cuz it is smaller