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Question

Hello!

I'm quite a beginner to the game but has gotten as far as orbiting Kerbin.

Now, im trying to get to the mun with a lander, the landers i've come up with are pretty big since i want a bit of everything with me. 

So my real question is, my spaceship turs too heavy at the top and tips at 10k meters. What do i need to do prevent this?

I'll post pictures if anyone wants them :)

 

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5 hours ago, Abbin21 said:

I'll post pictures if anyone wants them :)

For troubleshooting ship design issues, pictures are pretty much required.   If you're in Career or Science mode, a picture of your tech tree will be useful too.

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5 hours ago, Abbin21 said:

Hello!

I'm quite a beginner to the game but has gotten as far as orbiting Kerbin.

Now, im trying to get to the mun with a lander, the landers i've come up with are pretty big since i want a bit of everything with me. 

So my real question is, my spaceship turs too heavy at the top and tips at 10k meters. What do i need to do prevent this?

I'll post pictures if anyone wants them :)

 

They flip because they are too light at the top.

Using fins usually helps, but it would be better with images.

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This thread has been moved out of Tutorials, since it is seeking help rather than offering it. 

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12 hours ago, Abbin21 said:

So my real question is, my spaceship turs too heavy at the top and tips at 10k meters. What do i need to do prevent this?

Are you following a normal turn and slowly turning over from launch to 10km, and then having problems? Or are you launching straight up to 10km and then cranking it over 45 degrees? If you're doing the latter, you're following old tutorials and should instead slowly turn your ship as you rise.

Even a well-done gravity turn though will flip if your ship is back heavy, like many ships tend to be. As you burn fuel the center of mass of your rocket tends to go downward as engines are very heavy.

As others have said, pictures of your craft will be needed for more specific advice.

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As others have said, can't really speak to the design issue without pics or more info about what the craft looks like now.

But one issue is: you might want to do some intermediate missions rather than going straight from Kerbin orbit to munar landing.  For example, you could do what Apollo did: test out a lunar craft in Kerbin orbit, then fly by the Mun, then orbit it, then try a landing.  Or maybe check out Minmus at some point in there.  You might even think about landing on Minmus first.  It takes less fuel overall, and the lower gravity is more forgiving.  

There are a couple reasons to take things in steps.   If you're playing Science or Career mode, you can get a ton of science points from the lunar SOIs, and that will help unlock some of the better parts for landers, like the Terrier and Spark engines.  But beyond that, you can just get more familiar with what works and what doesn't, find ways to optimize your design, and so forth.  

So for purposes of your present issue, you could consider starting with a simpler orbiter that has enough fuel to get to the Mun and back.  And once that works, add in a lander component for the final mission.  

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3 hours ago, 5thHorseman said:

Or are you launching straight up to 10km and then cranking it over 45 degrees? If you're doing the latter, you're following old tutorials and should instead slowly turn your ship as you rise.

I turn at 45 degrees, and i Will test what you said! I Am watching Scott manleys 3 years old tutorial. But i Will post pictures aswell later today!

 

52 minutes ago, Aegolius13 said:

 

But one issue is: you might want to do some intermediate missions rather than going straight from Kerbin orbit to munar landing.  For example, you could do what Apollo did: test out a lunar craft in Kerbin orbit, then fly by the Mun, then orbit it, then try a landing.  Or maybe check out Minmus at some point in there.  You might even think about landing on Minmus first.  It takes less fuel overall, and the lower gravity is more forgiving.  

I'll try this but i Will post pictures aswell :)

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1 hour ago, Abbin21 said:

I turn at 45 degrees, and i Will test what you said! I Am watching Scott manleys 3 years old tutorial. But i Will post pictures aswell later today!

Yeah don't follow that tutorial :) You still want to be about 45 degrees at 10km, but you want to start turning almost immediately and slowly work your way over. A good and easy first approximation is to get to 50-100m/s, then turn 5 degrees. Then slowly turn in 5 degree increments every 1km you rise, so after you go 10km you've turned about 50 degrees. There are far better ways to do it but that's at least better than what you're doing.

Not only are you nearly guaranteeing that you'll have problems in ascent, if you manage to get into orbit you're wasting over 1000m/s. The old "45 degrees at 10km" ascent costs somewhere near 4500m/s, while the gradual turn is something more like 3000-3500 depending on aerodynamics and other factors.

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You don't want the prograde marker on the nav ball getting too far away from the direction your spacecraft is pointing. :wink:

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You don't need RCS or monoprop if you aren't going to dock with anything. It's dead weight. And with a decoupler below the monoprop tank you are going to reenter with the unspent fuel, which will make slowing down enough for the parachutes to work a real pain.

The engine on your lander is at least twice as long as your landing legs. That's not going to work.

 

And to the launcher: Fins go on the bottom of the rocket. The higher up they are the less usefull they are. If they're above the center of mass they even become counter productive and start working against you. All those SRBs will give you an insane amount of thrust but add actually not much in terms of delta v. With no nocaps they will also produce a lot of drag that will also work against you. All you're doing with those designs is ramming your ship as hard a possible against the air while giving the air a lot of options to push you over.

There's a nice explanation of how aerodynamics work in the game in the tutorial section:

If you're looking for youtube tutorials, basically disregard anything made before May 2015.

Edited by Harry Rhodan

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55 minutes ago, Harry Rhodan said:

 

And to the launcher: Fins go on the bottom of the rocket. The higher up they are the less usefull they are. If they're above the center of mass they even become counter productive and start working against you. 

 

I'm always keeping the center of airodynamics at the same place as the center of mass. If I understand you correct i have to much stuff with me in all "Sections"

Your help was useful, Thanks!

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47 minutes ago, Abbin21 said:

I'm always keeping the center of airodynamics at the same place as the center of mass

You want that for airplanes, but not for rockets.  I never even worry about the CoA on rockets.  And you really need to do everything you can to keep the mass down, so don't try to bring EVERYTHING with you on every mission.  Think about what you really need and bring only that.  Remember that more mass in your payload means you will need more fuel(and possibly even a more powerful engine) in your final stage...which then means even MORE mass that the previous stage will need to lift, meaning that it will need to be even larger.  And so on for every stage.  It's not nearly as bad as real life(where it costs thousands of dollars per pound of payload), but still something you want to think about. 

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1: Get rid of the monopropellant.
2: Get rid of 1 of those batteries. They store a lot, and with the panels, you'll be fine.
3: Is that a drill I see? That's not necessary. You have no isru or ore tanks, and you don't really need them anyways.

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5 hours ago, Abbin21 said:

So here are 3 of my tries but all have failed more or less.

On those second two examples you are using the nuclear engine. I would seriously suggest against that for two reasons. First, you're using fuel tanks that have both liquid fuel and oxidizer (LFO), but that engine only uses liquid fuel. That means you're carrying around a bunch of oxidizer that you don't need. And even if you drain the oxidizer out before you launch, it is still not very efficient because now you start with a half-empty tank. Better to use the LF only airplane fuel tanks. 

The second reason is the mass of the the nuke engine. It's really heavy, which means that it's better efficiency only counters that heavy mass when your ship is really heavy. For a craft that small the heavier engine is hurting you more than the better fuel efficiency it gives you. You'd be better off with the small Terrier engine. 

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22 minutes ago, FullMetalMachinist said:

 

The second reason is the mass of the the nuke engine. It's really heavy, which means that it's better efficiency only counters that heavy mass when your ship is really heavy. For a craft that small the heavier engine is hurting you more than the better fuel efficiency it gives you. You'd be better off with the small Terrier engine. 

Thanks!, i used the terrier in my new design. I built another rocket from scratch :)

2 hours ago, Hodari said:

You want that for airplanes, but not for rockets.  I never even worry about the CoA on rockets.  And you really need to do everything you can to keep the mass down, so don't try to bring EVERYTHING with you on every mission.  Think about what you really need and bring only that. 

Thanks! That helpful since i'm a horder of everything :P I Guess i need to learn to not take everything everywhere.

So after all the tips and a few hours of trial and error i did it!!

Moon Orbit

Approaching The Moon

Moon Surface

LANDED!

Thanks a lot for all the help! I've learned a lot of useful things today!

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39 minutes ago, Abbin21 said:

So after all the tips and a few hours of trial and error i did it!!

Awesome, congratulations! I've found that few games give me the sense of accomplishment that KSP does, mostly because you really have to earn those big moments. 

40 minutes ago, Abbin21 said:

Thanks! That helpful since i'm a horder of everything :P I Guess i need to learn to not take everything everywhere.

A bit of general advice for you going forward: less is more. In space flight, mass is everything. Best practice is generally to specifically design what you want each craft/mission to do. Then design a final stage that accomplishes that goal with as little mass as possible. Then stick that on a stage that pushes it where it needs to go with as little mass as possible. Rinse and repeat until you're sitting on the launch pad with the smallest rocket that can get the job done. 

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3 hours ago, FullMetalMachinist said:

Awesome, congratulations! I've found that few games give me the sense of accomplishment that KSP does, mostly because you really have to earn those big moments. 

Yes i know! Even tho this game takes a long time to learn it's an accomplishment to even get around Kerbin :P haha *noob* 

3 hours ago, FullMetalMachinist said:

 

A bit of general advice for you going forward: less is more. In space flight, mass is everything. Best practice is generally to specifically design what you want each craft/mission to do. Then design a final stage that accomplishes that goal with as little mass as possible. Then stick that on a stage that pushes it where it needs to go with as little mass as possible. Rinse and repeat until you're sitting on the launch pad with the smallest rocket that can get the job done. 

Right, i had half a tank over when i landed so i can probably remove at least one when i learn to gut into space properly! Thanks for your help! Love from Sweden <3 

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4 hours ago, FullMetalMachinist said:

 

The second reason is the mass of the the nuke engine. It's really heavy, which means that it's better efficiency only counters that heavy mass when your ship is really heavy. For a craft that small the heavier engine is hurting you more than the better fuel efficiency it gives you. You'd be better off with the small Terrier engine. 

Comparing the nuke to the terrier, both produce the same thrust.   The nuke is 2.5 tons heavier.  But, it uses only 43% of the fuel.   What's our break even point?

Fuel mass saving = Terrier Fuel  x 43%

subbing in the numbers..

2.5 T   =  Terrier Fuel  x  0.43

rearrange this equation..

Terrier Fuel (of break even point) = 2.5T  /   0.43      = 5.8 Tons

5.8 tons is about 1000 units of LFO .  In other words, if you're feeding more than an FT-800 and FT200 tank into a terrier engine, you should consider going nuclear instead.    Of course, for mk1 capsules, even a Terrier is overkill for Mun landings.

Incidentally I made a nuke moon lander to see if i could overcome the problems of height/stability.   Looks like a space invader .  Unfortunately I still can't make a decent set of ladders.

edit - 1200 units of LF on the lander, giving >2000dV  AND 3.5:1 TWR in Munar gravity. Total overkill.     ps.  it could really use radiators.   the only time i ever see nukes overheat something is when you attach directly to  a mk1 can (low heat part).

Edited by AeroGav

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5 hours ago, Choctofliatrio2.0 said:

1: Get rid of the monopropellant.
2: Get rid of 1 of those batteries. They store a lot, and with the panels, you'll be fine.
3: Is that a drill I see? That's not necessary. You have no isru or ore tanks, and you don't really need them anyways.

Yea, i kinda wanted to make a mining-station without even knowing what i need with me :) I'll defenetly do that in the future when i know more about building.

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One thing the editor doesn't show you is the center of drag. When you have a lot of drag at the front, it will want to tip you over. Use nosecones.

When the blue "lift" aerodynamic marker is overlapping with the yellow/black center of mass market, it is unstable - even in planes, one wants the blue market to be a bit behind the center of mass. With rockets which have less control surface area, you want it very far back.

Also note that the center of mass of a rocket stage tends to shift backwards as fuel mass is expended, but the heavy engine at the bottom remains. - another reason why you want the blue market significantly behind the center of mass marker.

Sudden turns are not good, particularly when travelling at high speed in thick atmosphere. You really shouldn't have your TWR be any higher than 2:1 at the start of any stage, or you'll probably get going really fast while still in thick atmosphere, and lose a lot ot drag.

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