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# could someone help?

## Question

I want to get to laythe, and make a reasonable sized base there. The other times i make a laythe rocket, It weighs around 10,000 tonnes and has Only an Lander can (the larger one) with a parachute one it. I need some tips to get my base to laythe, and use minimum fuel. And, I only use stock. Anyone who helps me is totally epic.

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The biggest tip is going to Laythe at a time when the transfer there is cheap, a "transfer window". You can find cheap transfer windows using online tools like http://ksp.olex.biz/ (simple) or https://alexmoon.github.io/ksp/ (more complicated). Learning how to leave at the right time and do the burn from low Kerbin orbit are essential skills for efficient interplanetary missions.

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10,000 tons for a 3-ton one-way payload to Laythe is... extravagant.  That ought to be doable for a tiny fraction of that mass.  And by "tiny", I mean "a lot less than a twentieth".

If you're spending that much mass to get there, then what that means is that there's something (or possibly several somethings) inefficient in the way you're building and/or flying to get there.  So the key is to figure out where you're going off the rails.  KSP has many, many ways to "do it wrong" ... so more info from you is needed to help folks be able to give you more specific advice.

A few questions for you:

Q:  What does your overall flight plan look like?

A typical bare-bones mission to Laythe will look something like the following.

Spoiler

This is the simplest form.  (There are other ways to do it, this is just the basic.)

1. Wait for a good launch window for transit from Kerbin to the Jool system
2. Launch to LKO (low Kerbin orbit)
3. At the appropriate point in orbit, do a single burn of around 2000 m/s or a bit less (this is enough to send you to Jool)
4. Possibly use some retro-thrust to slow down before hitting Laythe's atmosphere, if you're going too fast
5. Aerobrake at Laythe
6. Land.

If you want to get a little fancier (more complicated flight, but saves a lot of dV), you can replace step 4 with this:  upon arrival at Jool, use a reverse gravity assist from Tylo or Laythe to capture to Jool (this saves you from having to use your engines), then do a small burn at the appropriate spot to get a Laythe intercept.

Does your flight plan look basically like that, or are you doing something significantly different?

Q:  Maybe you're inefficient at getting to LKO (low Kerbin orbit).

Look at the mass of your ship on the launchpad, then look at the mass once it's in low Kerbin orbit.  What percentage of your launchpad weight is your orbital weight?

If it's really really low, this is a sign that you need to work on your "get to orbit" technique.

Q:  Maybe your lifter is inefficiently built.

Launchpad screenshot?  What's your launchpad TWR?

Q:  Maybe your flight technique to LKO is really inefficient.

Can you describe what your flight profile looks like?  At what altitude/speed do you start your gravity turn?  What is your ship doing (angle and speed) when it reaches 10 km altitude?

Hint:  at 10 km, you should be tipped at approximately 45 degrees from the vertical (not a lot steeper or shallower) and going roughly 300-400 m/s.  If you're a lot different from that, we should talk.

Q:  Maybe your Kerbin-Jool transfer stage is inefficiently built.

Screenshot of your ship when it's in LKO?

Hint:  You want a fairly low TWR, and an engine (or engines) with the highest Isp possible.

Q:  Maybe your Kerbin-Jool transfer is inefficient.

When you do your ejection burn from Kerbin orbit, how many m/s are you using?

Ideally it should be under 2000 m/s; if it's a lot higher than that, you've got a problem.  Perhaps you're not picking a good transfer window.  Tools like http://ksp.olex.biz can be very helpful for that.

...There are other possibilities, too, but those seem like the most likely potential culprits.

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Nuclear engines are great for long-haul trips of this nature (just make sure to use LF only tanks).  If you have a very small payload, you may want a stage or two of small chemical rockets before you get to the nukes.  But if you're sending a sizeable base, nukes probably make sense for the top stage.  It's also helpful to design so you can discard your empty tanks (and possibly some of your nukes) as you burn out the fuel.

As far as flight plan, agree with Snark that you really need to nail the ejection burn.  You want your transfer orbit to be just tangent with Jool's orbit at your apoasis. If you can set up your ejection so that Jool is at the new AN or DN, you may not need to do a plane change en route.  Or sometimes you can do some of the plane change at the same time you eject, which can save a lot of fuel (this works best if Kerbin is at or near the AN or DN when you leave.  Whether this is the case depends on what launch window you pick).

To conserve fuel on the capture side, you'll probably want to do one (more more) of three things: aerobrake at Laythe, aerobrake at Jool itself, or get a gravity assist (Tylo works best).  For the first two options, you'll likely need a heat shield.  The inflatable shield is ridiculously good for things like this.  Even if I plan to aerobrake at Lathe later, I generally start with the Tylo assist, since that won't kill you if you're going too fast.

Hopefully that all makes sense - if not, happy to provide some screen shots or more info.

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18 hours ago, Snark said:

10,000 tons for a 3-ton one-way payload to Laythe is... extravagant.  That ought to be doable for a tiny fraction of that mass.  And by "tiny", I mean "a lot less than a twentieth".

If you're spending that much mass to get there, then what that means is that there's something (or possibly several somethings) inefficient in the way you're building and/or flying to get there.  So the key is to figure out where you're going off the rails.  KSP has many, many ways to "do it wrong" ... so more info from you is needed to help folks be able to give you more specific advice.

A few questions for you:

Q:  What does your overall flight plan look like?

A typical bare-bones mission to Laythe will look something like the following.

Hide contents

This is the simplest form.  (There are other ways to do it, this is just the basic.)

1. Wait for a good launch window for transit from Kerbin to the Jool system
2. Launch to LKO (low Kerbin orbit)
3. At the appropriate point in orbit, do a single burn of around 2000 m/s or a bit less (this is enough to send you to Jool)
4. Possibly use some retro-thrust to slow down before hitting Laythe's atmosphere, if you're going too fast
5. Aerobrake at Laythe
6. Land.

If you want to get a little fancier (more complicated flight, but saves a lot of dV), you can replace step 4 with this:  upon arrival at Jool, use a reverse gravity assist from Tylo or Laythe to capture to Jool (this saves you from having to use your engines), then do a small burn at the appropriate spot to get a Laythe intercept.

Does your flight plan look basically like that, or are you doing something significantly different?

Q:  Maybe you're inefficient at getting to LKO (low Kerbin orbit).

Look at the mass of your ship on the launchpad, then look at the mass once it's in low Kerbin orbit.  What percentage of your launchpad weight is your orbital weight?

If it's really really low, this is a sign that you need to work on your "get to orbit" technique.

Q:  Maybe your lifter is inefficiently built.

Launchpad screenshot?  What's your launchpad TWR?

Q:  Maybe your flight technique to LKO is really inefficient.

Can you describe what your flight profile looks like?  At what altitude/speed do you start your gravity turn?  What is your ship doing (angle and speed) when it reaches 10 km altitude?

Hint:  at 10 km, you should be tipped at approximately 45 degrees from the vertical (not a lot steeper or shallower) and going roughly 300-400 m/s.  If you're a lot different from that, we should talk.

Q:  Maybe your Kerbin-Jool transfer stage is inefficiently built.

Screenshot of your ship when it's in LKO?

Hint:  You want a fairly low TWR, and an engine (or engines) with the highest Isp possible.

Q:  Maybe your Kerbin-Jool transfer is inefficient.

When you do your ejection burn from Kerbin orbit, how many m/s are you using?

Ideally it should be under 2000 m/s; if it's a lot higher than that, you've got a problem.  Perhaps you're not picking a good transfer window.  Tools like http://ksp.olex.biz can be very helpful for that.

...There are other possibilities, too, but those seem like the most likely potential culprits.

with the mission, i skipped lko and went straight to escape velocity instead. then i thrusted to a jool encounter, without caring about the transfer burn. then i had a crappy jool orbit and had to thrust for a while for a laythe encounter. then i was going realy fast, and used up lots of fuel.

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5 hours ago, Ackoli said:

with the mission, i skipped lko and went straight to escape velocity instead. then i thrusted to a jool encounter, without caring about the transfer burn. then i had a crappy jool orbit and had to thrust for a while for a laythe encounter. then i was going realy fast, and used up lots of fuel.

OK, so there's your problem right there. If you try to do it that way, you're wasting lots of dV, which is making your ship's job way harder than it needs to be. (Plus there's still the possibility of issues with your ship design on top of that.)

So, the best advice I could offer would be, "don't do that".

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