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Returning Old Player Cannot Rocket (Mods/Help/Suggestions/Comfort and Solace Requested)


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Wasn't sure whether this properly belonged in Welcome Aboard, Gameplay Questions, General Add-On Affairs, or here. To here it is!

So I've been in and out of KSP for quite a while (I don't remember the version I started with, but that's not important), and now I'm finally drifting back in for the first time since "real-release". I wasn't particularly adept at Kerbal rocketry even before, and now I find myself spending a lot of time being frustrated at myself, so I'm hoping some folks here can at least get me oriented in the right direction.

My main issue to-date is primarily one of planning and efficiencyâ€â€namely, I don't know how to do either. I struggle to get a rocket into LKO effectively and efficiently (if I slap enough explosions on the thing I can get there inefficiently, but that's heinous), and when I do manage it I rarely have enough fuel left to do a whole lot elseâ€â€I've flown by the Mun and back, and that's it (technically I've also smashed an unmanned probe into the surface, but that's not much of an accomplishment). I understand the "first-level basics"â€â€prograde/retrograde, apoapsis/periapsis, Center of Mass/Thrust/Lift, what Delta-V is, that "specific impulse" basically means "gas mileage", etc. I don't understand how to efficiently/effectively use Delta-V, Thrust-to-Weight Ratios, how to deliberately plan a gravity assist instead of missing the Mun and hitting Minmus through sheer luck, etc. That is, the sort of stuff that "opens the doors" of the game, so to speak.

So I'm turning here primarily because my search-fu is awful and because I rely on the wisdom of the mob in making recommendations.

Specifically, here's what I'm hoping to find:

1) A good tutorial on being efficient/effective with Delta-V.

2) A good tutorial on Thrust-to-Weight Ratios and what to do with them in order to properly rocket.

3) How to get into orbit around Kerbin efficiently instead of just flailing around and spraying probably-wasted fuel all over the place.

4) A good tutorial on how to intentionally plan to go places.

5) Any mods to help with any of the aboveâ€â€I know the game doesn't always provide information (like TWR), and even though I don't currently know what to do with that information, once I do know that I would like to also actually have access to it.

Currently the only mod I have installed and used is PreciseNode. I have also installed (as of this morning), but not yet used, KW Rocketry and Kerbal Engineer Redux (again, in the latter case, I wouldn't know what to do with the information it provides anyway).

While written tutorials would be excellent so I can read them at work (so diligent, I know), I won't turn away a good video or video series if it'll help me get myself properly oriented.

So, in short: Little help?

(Edit: I know the Tutorials subgroup has a library, but it seems like the overwhelming majority of the information there is out of date with regards to version 1.0.x)

Edited by Landwalker
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Mechjeb. Mechjeb. Mechjeb. It is how I learned to get to Kerbin orbit. Just watch it go a few times.

Just to make sure I'm clear on what you mean: Do you mean "build a rocket, turn on MechJeb autopilot*, watch happen"?

* I know very little about MechJeb from a practical standpoint, other than "it has autopilot maybe?" I see it mentioned often and looked at the mod page, but there were so many dialogue boxes in the screenshot that I immediately said "Waaaaay too advanced to me" and moved on. I'll have to find some "MechJeb Tutorials" or something when I get home later.

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An alternative to MechJeb is Kerbal Engineer Redux... it doesn't autopilot for you like MechJeb does, but it has the (IMHO) superior UI when it comes to displaying info to the user.

Regarding your questions - I'm not enitrely sure what you mean in some cases. Like "how to be efficient with dV". How do you mean? Like, picking the direction to burn in which results in the smallest dV costs for adjusting your orbit in a certain way? That actually can't be explained just like that. A lot of it is practice, practice, practice because it completely depends on the situation, your current orbit, your parent celestial, your desired maneuver and so on and so forth.

A first start to this, I would say, is to grok what the six maneuver directions signify. Like, really internalize it. Not just knowing that if you pull the green thingy on the maneuver node then that makes the orbit bigger - but having the intuitive understanding that burning radial-in rotates your orbit in the same direction as the direction of your orbit around the body, around the normal-antinormal axis through the position of your vessel, constrained by the position of the body you're orbiting. If what I just wrote made you blink in confusion, you still lack that intuitive understanding. Instead, if you saw the maneuver happen in front of your inner eye while nodding in agreement, you have it down pat.

You need this intuitive understanding of the six degrees of freedom that you have, if you want to execute the most dV-efficient maneuvers. Else you'll just end up trying to get a Duna intercept while wondering why in the world does pulling Prograde or Retrograde both make your closest approach increase instead of decrease past a certain point, even though you did exactly the same thing as the tutorial you're following! That situation exists, and it's trying to tell you something. I can tell you now that that something is "check your inclination", but the understanding of why that is, and how to transfer that knowledge from that one specific case into general use, needs to come from you.

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A few starter tips:

1) There are engines you just do not want to use at sea level. The ISP or MPG as you put it just goes through the floor under any sort of atmospheric pressure. This is an easy pitfall. Right-Click on an engine in the parts list for more information and pay attention to it's ISP at sea level (I_ASL) and in a vacuum (I_VAC). 1st stage engines should have I_ASL of 275 or greater at sea level. Later stages should be I_VAC 320 or better.

2) KER is a great mod. To begin with the info you want to pay attention to is TWR (thrust to weight ratio) and DV. You need TWR to get off the pad and DV is how much useful work your built configuration can manage.

3) Accent speed. You want a TWR of 1.1 to 1.3. If you over-engine a craft you're both wasting DV hauling up engines that you don't need and flying too fast in atmosphere that's too thick. The overpowered rocket is also likely to have stability issues. If you're using an engine that can throttle, TWR of up to 1.5 is acceptable as long as you throttle down a bit around Mach1 (~350ms) to about 75-80% until you're above 10km. The key to an efficient accent is to match terminal velocity. Faster and you fight air resistance too much. Slower and you're basically spending some of your fuel hovering by eating time. For this reason Solid rocket boosters are acceptable to get quickly up to speed (TWR ~2) as long as they are discarded before you overspeed (You can also limit their thrust in the VAB to keep TWR down). It's tricky to tell the terminal velocity, but if you get re-entry heating on ascent you're definitely going too fast.

4) Ascent angle. There's a bit of an art to this. I nose-over to 10 deg at about 100ms and try to aim for 45 deg by 15km, 70 deg by 30km and hold that until my apoapsis breaks atmosphere. Then I shut down engines and circularise at Apoapsis of about 75km.

5) Burn efficiency. The most efficient place to change apoapsis is to burn at periapsis. Similarly to change periapsis burn at apoapsis.

Edited by RCgothic
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I too consider Mechjeb a valuable learning device. From it, I learned everything except basic orbit and interplanetary transfers. It's not too terribly complicated unless you want to start tweaking it's efficiency.

It's also a tremendously useful tool of convenience and can do quite a lot without you even paying attention (if you're into that). You tell it what you want to do, it orients the ship, warps you to the execution point, and executes the maneuver then shuts off. On rare instances, it will sometimes activate HAL 9000 mode, so watch for that.

And fair warning: You will encounter tons of people who scoff and mock Mechjeb, saying how terrible it is to use it, do it yourself... then they'll promptly direct you to watch a video of somebody else doing something so you can copy that person instead. It's silly.

Edited by Randazzo
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Specifically, here's what I'm hoping to find:

1) A good tutorial on being efficient/effective with Delta-V.

Check out some DasValdez or Scott Manley videos. You pretty much want the least number of engines possible for your purpose. Which means as low a TWR as possible, but still able to meet the mission requirements.

2) A good tutorial on Thrust-to-Weight Ratios and what to do with them in order to properly rocket.

TWR is dependant on if you're landing, or in atmosphere. In vacuum, most of the time TWR doesn't matter. Unless you're trying to accelerate quickly (i.e. direct launching to a station.)

3) How to get into orbit around Kerbin efficiently instead of just flailing around and spraying probably-wasted fuel all over the place.

High TWR crafts are less of a draggy mess in atmosphere now. Just keep the mach effects (white vapor) away until you're at least at 15,000m or higher.

4) A good tutorial on how to intentionally plan to go places.

You need to check out a few videos by someone like DasValdez; and use a mod called "Transfer Window Planner". This way you get efficient transfers, and it gives you all the information you need for the transfer burn; including how much prograde and normal/antinormal you need.

5) Any mods to help with any of the aboveâ€â€I know the game doesn't always provide information (like TWR), and even though I don't currently know what to do with that information, once I do know that I would like to also actually have access to it.

Please please please don't use mechjeb, making mistakes is part of KSP. It's more fun to figure out stuff yourself anyhow :). Use the afformentioned Transfer Window Planner for interplanetary transfers. Use Kerbal Alarm Clock to set alarms that automatically alert you to a specific item that needs your attention (the warp-to function has some bugs, and sometimes warps too far.) Precise Node is great to get your burns just right. And, of course, Kerbal Engineer; for all of your informational needs.

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Since you know the basics, I recommend mucking about in sandbox modeao you don't have to worry about funds and science limitations.

For take off youll want to keep your COM(center of mass) in the middle or top. You can do that by having a stage for space(lv-909 is a great engine for smaller vehicles). You'll want your COL(center of lift) aka center of drag at the bottom of your rocket. You do that by adding wings as far bottom as you can go, but they don't have to be very large because it will add mass and take away from your delta v. COT(center of thrust) isn't too important but is conventionally and most likely going to be towards the bottom.

Now assuming your rocket is designed decently, and your thrust to weight is enough to lift your rocket, you'll want to slowly tilt your rocket shortly After liftoff. I personally wait till I'm going between 50 and 100m/s and then tilt my rocket over Bout 10 degrees then have my rocket hold prograde vector. Your rocket will want to go up but gravity is pulling the tip of your rocket slowly down. It's OK to make minor corrections but the initial tilt is key and if done perfectly. There is no need for sas. Your tilt should be around 45 degrees when you reach 15km and between 60 and 80 when you get to 30-35km. After that it's All about getting your apoapsis at the desired altitude and circulizing at apoapsis.

I highly recommend installing the mod Kerbal Engineer Redux as it will tell you your delta v for all stages. I will aim for 3200-3500 delta v for atmosphere at 0km since your delta v will most likely go up at least a little bit aa you accend

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An alternative to MechJeb is Kerbal Engineer Redux... it doesn't autopilot for you like MechJeb does, but it has the (IMHO) superior UI when it comes to displaying info to the user.

Good to know. I'm looking forward to getting a chance to try it out tonight, and hopefully it'll help me start to understand some of what's going on with my so-called rockets.

Regarding your questions - I'm not enitrely sure what you mean in some cases. Like "how to be efficient with dV". How do you mean? Like, picking the direction to burn in which results in the smallest dV costs for adjusting your orbit in a certain way? That actually can't be explained just like that.

That sort of is what I'm trying to get at. Another way to put it would be this:

3) Accent speed. You want a TWR of 1.1 to 1.3. If you over-engine a craft you're both wasting DV hauling up engines that you don't need and flying too fast in atmosphere that's too thick. The overpowered rocket is also likely to have stability issues. If you're using an engine that can throttle, TWR of up to 1.5 is acceptable as long as you throttle down a bit around Mach1 (~350ms) to about 75-80% until you're above 10km. The key to an efficient accent is to match terminal velocity. Faster and you fight air resistance too much. Slower and you're basically spending some of your fuel hovering by eating time. For this reason Solid rocket boosters are acceptable to get quickly up to speed (TWR ~2) as long as they are discarded before you overspeed (You can also limit their thrust in the VAB to keep HER down). It's tricky to tell the terminal velocity, but if you get re-entry heating on ascent you're definitely going too fast.

4) Ascent angle. There's a bit of an art to this. I nose-over to 10 deg at about 100ms and try to aim for 45 deg by 15km, 70 deg by 30km and hold that until my apoapsis breaks atmosphere. Then I shut down engines and circularise at Apoapsis of about 75km.

That's very much the kind of stuff I'm thinking of: What are appropriate TWRs, how do I leverage that to the appropriate ascent speed and angle when trying to leave Kerbin, etc. My concern now is that I'm lifting very inefficiently and wasting a heinous amount of fuel in the process, leaving me with barely enough to circularize an orbit, let alone head off to do other fun stuff (and Great Kerb forbid actually landing on the Mun). Part of that may be wasting fuel by trying to blow through the atmosphere at hilariously wrong speeds and angles, and part of it may just be gross design failures on my part.

A first start to this, I would say, is to grok what the six maneuver directions signify. Like, really internalize it. Not just knowing that if you pull the green thingy on the maneuver node then that makes the orbit bigger - but having the intuitive understanding that burning radial-in rotates your orbit in the same direction as the direction of your orbit around the body, around the normal-antinormal axis through the position of your vessel, constrained by the position of the body you're orbiting. If what I just wrote made you blink in confusion, you still lack that intuitive understanding. Instead, if you saw the maneuver happen in front of your inner eye while nodding in agreement, you have it down pat.

Sounds like I need to get a probe into orbit so I can do this and see what it meansâ€â€you lost me at the bold text.* I'm functional with Prograde/Retrograde and even somewhat with Normal/Antinormal (in that, if I actually manage to get into LKO in the first place, I can line up my inclination with another object), but beyond that is something that I'm just going to have to play around withâ€â€and playing around with it requires a few fundamental capabilities first that I don't feel like I have yet.

*I looked this up on the KSP Wiki and it thankfully had images showing exactly this, so I now know what you mean. I just had never done it before and needed to see it in order to completely process it.

Please please please don't use mechjeb, making mistakes is part of KSP. It's more fun to figure out stuff yourself anyhow . Use the afformentioned Transfer Window Planner for interplanetary transfers. Use Kerbal Alarm Clock to set alarms that automatically alert you to a specific item that needs your attention (the warp-to function has some bugs, and sometimes warps too far.) Precise Node is great to get your burns just right. And, of course, Kerbal Engineer; for all of your informational needs.

Yeah, my preference is to avoid complete automationâ€â€learn by doing, even though I may need some more foundational learning before the doing becomes practical. At the same time, if I'm doing something wrong and don't know it's wrong (or I strongly suspect it's wrong but don't know in what way it's wrong), I can't really learn much, which feels like my biggest current problem: Something is wrong. But I don't know what it is, or what's causing it, or how to fix it, and I don't have any reliable way to compare what I'm doing in different situations, so it's very difficult to learn by doing without... well, without knowing what I'm doing. :huh:) I'll take a look at KAC later today, and TWP as well. (I'm still a ways away from interplanetary transfers at the moment, so it may be a more down-the-road itemâ€â€gotta land on the darn Mun first. And get back. Intact.)

Will also go on the hunt for some Scott Manley / DasValdez videos when I get home. The names ring a bell, although mostly a bell that says "Here are crazy, crazy things that you will never be able to do." As long as they have some videos that include "Here's what we're doing and here's why", though, I should be able to benefit from them. It's always the "Why" that feels out of reach.

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Glad you found my post helpful. Note that the TWRs I mentioned are for atmospheric ascent only. One you're in space TWR matters little compared to engine ISP. I once sent a ship to Duna that was hilariously underpowered. I had to make four burns on successive orbits to break free of Kerbin's influence. But it had great ISP, which is what really matters in space.

For an early career mode game I'd have a 1st stage of ~1500 DV powered by an LT-30 engine. Great first stage, but had no gimbal so you'll need a few fins at the bottom.

2nd stage should be sufficient to get you into orbit - use an LT-45 as it has better ISP, ~2200DV should give you enough to reach orbit and complete orbital insertion with a little left over. Should be taking over from the first stage after 15km. It has less thrust but by now you've jettisoned some mass and it has a gimbal so you shouldn't need fins anymore.

If you want to actually go anywhere from LKO add a third stage powered by an LV909 which has excellent vacuum I SO.

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Just to make sure I'm clear on what you mean: Do you mean "build a rocket, turn on MechJeb autopilot*, watch happen"?

* I know very little about MechJeb from a practical standpoint, other than "it has autopilot maybe?" I see it mentioned often and looked at the mod page, but there were so many dialogue boxes in the screenshot that I immediately said "Waaaaay too advanced to me" and moved on. I'll have to find some "MechJeb Tutorials" or something when I get home later.

And then try the same.

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Engine gimbals are seem more effective than in previous versions, and for my rockets I usually tone them down to ~25-30%. Right-click on the engine to set the gimbal range. For my launches, I tilt right starting at 50m/s, and stop at 10* by the time it hits 100m/s. Make sure to hit F to reset the SAS to 10*. From there, I leave it holding position until the direction indicator just starts to leave the prograde indicator, then I turn on Follow Prograde. (with full gimbal range this causes my rockets to oscillate and fly apart, with the 25% setting I can usually just leave it there). Throttle down to stay below 350m/s (or just keep your TWR < 1.8ish) until 15km or so. With new aero, if you go fast your drag gets high enough your control surfaces can't compensate. Hit F12 to see your drag indicators, once they get long and the indicators point past the sides of your rocket's bottom instead of in the center, it's flipping time - prevent this by lowering speed, staying prograde, and getting higher in the atmo.

If you see red re-entry heat on your rocket, you're definitely going too fast too low.

Once I get about 28km, I open up the throttles full until my Time to Apoapsis (Kerbal Engineer) hits about 2 minutes, then I gradually throttle down keeping ToA ~2 minutes, until Apoapsis hits my target altitude, usually 100km. Then I keep minimal thrust to keep my Apoapsis up until I leave atmo at 70km. Circularize as normal. My circularization burn is typically 50-60m/s.

Now, advanced situations may require changes. I was lifting my Moho Support Vehicle for an Elcano run, which is ridiculously draggy with all the exposed wheels, ore containers, drills, etc. So I lifted straight up for a longer time before starting my turn to the right. Also had to deal with near-flipping when my drag hit max, but managed to save it.

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I'm running an old version of the game, so I can't be of any help with the aerodynamics, but I think some of this may still be helpful. . .

In the early part of the launch, I find my "pitch over" altitude is often determined more by the specific rocket than by the desired orbit. I've had some rockets that can start pitching over immediately, and some that had to stay vertical until the boost stack separated. Each new rocket is going to give you a slightly different ascent path depending on how they fly and how the various bits fall off. Don't worry too much about "optimal". "It works" is good enough. :)

Once you're clear of the worst of the atmosphere and have started your pitch over in earnest, your current altitude is largely irrelevant. At that point, I'm looking at two things. . .Apoapsis and Time to Apoapsis. You want to keep your Apoapsis ahead of you, but not too far. Roughly speaking, you want to keep your Apoapsis about 30 seconds in front of you. . .sometimes I'll push it out to 60 seconds if my upper stage is underpowered and I want more of a cushion. Burning straight at the horizon should cause your Time to Apoapsis to slowly decrease, depending on how much power your rocket has. If it drops below 30 seconds or so, bring the nose up a little bit until it pushes back out to 30. If your rocket "catches up" to the Apoapsis, that means your Periapsis is closer than your Apoapsis and you're going to drop back into the atmosphere before you start to climb up again. And that means more drag, and possibly the loss of the rocket.

Once your Apoapsis reaches your desired altitude, cut your engines and coast until you reach it. You may need to periodically give the throttle a little tap to keep your Apoapsis altitude where you want it until you climb all the way out of the atmosphere. Burn prograde at Apoapsis to lift your Periapsis out of the atmosphere, and you're in orbit.

I had to rely on orbital refueling for my first Mun missions. Given that I was going to top off the tanks before the spacecraft left for the Mun, I kept trying to push my Kerbin parking orbits higher and higher, on the logic that it would take less energy to get to the Mun from a higher orbit. It was exactly the wrong thing to do, and thus I ran into my first inkling that "delta-v" is not a fixed value, no matter what MechJeb or Kerbal Engineer might tell you. A rocket does not have a set amount of "delta v" in the tank.

Because of the Oberth effect, the faster your rocket is moving, the more efficiently it converts fuel into delta v. This means you get more "bang for your buck" from a lower orbit. Burning for the Mun from my 300 x 300 km orbit took a certain amount of delta v. Performing that same burn from an 80 x 80 km orbit took a little bit more delta v. . .but it also resulted in a shorter burn time. Leaving from a lower orbit gave me more delta v for less fuel.

Also, I got a surprise the first time I tried a "high speed" transfer to the Mun. I'd been using a trajectory that took about 6-7 hours to transit to the Mun. A slightly longer burn gave me a three hour transit. But the resulting burn to brake into Munar orbit was much worse. Just a heads up. :)

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1.1 to 1.3 TWR seems really low. You're trading drag losses for gravity loses. Until you've gained some decent horizontal speed, you're bleeding 9.8 m/s of delta-v to gravity losses every second. Of course, if you push too hard you'll bleed off a lot of delta-v from atmospheric drag. There's a balance, and 1.1-1.3 TWR seems way too low. I try to stick around 1.7 or so.

If you ignore transonic drag, a TWR of 2 is ideal, because you'll approach terminal velocity, where gravity drag and atmospheric drag are equivalent (at least initially). The main reason to not go quite that high, though, is because of the aforementioned transonic drag. You'll end up in the transonic region fairly low in the atmosphere at that level of TWR which generates too much extra drag.

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1.2 to 1.5 is pretty much the sweet spot for my designs, and is one of the most reliable ways of making sure you're not too low when going transonic. Part of it depends on how much the Isp changes the thrust of the engine, which wasn't modeled properly in earlier versions of KSP. For example, the KR-2L is now terrible as a lifter engine, but is still great as a heavy upper stage engine. The Skipper now increases thrust by 14% as it goes from sea level to vacuum.

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First off, welcome back! Things have changed a bit since the transition to 1.0 and beyond. Launch methods that worked pre-1.0 don't necessarily work the same now.

My main issue to-date is primarily one of planning and efficiencyâ€â€namely, I don't know how to do either. I struggle to get a rocket into LKO effectively and efficiently (if I slap enough explosions on the thing I can get there inefficiently, but that's heinous), and when I do manage it I rarely have enough fuel left to do a whole lot elseâ€â€I've flown by the Mun and back, and that's it (technically I've also smashed an unmanned probe into the surface, but that's not much of an accomplishment).

Landwalker, can you provide us an example of a rocket design that you use, and can you also describe how you currently launch it into orbit? We might be able to better determine how to help you with that information.

Also, if you have not paid a visit to the Kerbal Space Program Wiki, you might want to take a look. Yes, some of the pages/tutorials on there are outdated, but the general concepts covering some of the things you want to do still apply... especially those things that don't involve atmospheres such as going places outside of Kerbin's sphere of influence.

Currently the only mod I have installed and used is PreciseNode. I have also installed (as of this morning), but not yet used, KW Rocketry and Kerbal Engineer Redux (again, in the latter case, I wouldn't know what to do with the information it provides anyway).

I have found Kerbal Engineer Redux to be incredibly helpful for understanding thrust to weight and delta-V. Definitely make use of its displays when designing rockets and when piloting them.

Delta-V (dV), thrust to weight (TWR), and specific impulse (Isp) are all interrelated. I tend to think of them as follows:

Delta-V: How much you can change your rocket's velocity (not necessarily just it's speed, as velocity is a combination of both speed and direction).

A rocket with greater dV can do more "stuff".

Thrust to weight: How quickly you can apply some of your delta-V.

A rocket with a higher TWR can change its orbit more quickly.

Specific impulse: Bang you get for your buck... how efficiently you burn fuel to apply your delta-V.

A rocket with a higher Isp can do "stuff" with less fuel.

To get into orbit around Kerbin, you need a rocket with on the order of 3500 dV. Add a bit more for piloting errors, and you end up around 4000 dV to get to low Kerbin orbit (LKO). As your piloting skills improve, this number will decrease a bit. If you're using a lot more dV than that to get into orbit, then you need to examine with a critical eye how you pilot yourself into orbit. "But how do I calculate my dV?" Well, you can look at the Tsiolkovsky Rocket Equation and crunch some numbers (I would recommend doing this a couple of times by hand to fully understand what's going on), or you could one of the game modes to compute it for you. MechJeb and Kerbal Engineer Redux come to mind.

If you want to do something once you're in orbit, you will need more than 3500 dV. There are a number of dV maps available that tell you how much additional dV you need to get from one celestial body to another. For example, to go from LKO to a low Munar orbit, you will need around 1170 dV. This is in addition to what you used to launch yourself into LKO originally. When you plan to modify your orbit by placing a maneuver node, a bar appears next to your navball telling you how much dV that maneuver will cost. I have a contract satellite rocket with a dV of around 6500 that I use to complete pretty much any "position a satellite" contract that is around Kerbin, Mun, or Minmus. In some cases, I can complete two or more contracts with the same satellite. I also have in orbit around Kerbin, just waiting for a good transfer window for Duna/Ike.

"How do I design a rocket that has more dV?" dV is related to the Isp of the current rocket stage and the current wet and dry masses of the rocket (wet mass is the rocket's mass including whatever fuel it currently has in it, dry mass is a rocket's mass excluding the current stage's fuel). So to end up with a higher dV you need to use an engine with a higher Isp, or make the ratio of wet mass to dry mass larger.

Also important is TWR. If your thrust is less than your rocket's weight, you are not going into space today. In the Vehicle Assembly Building, each rocket engine lists its thrust at sea level on Kerbin (ASL) and in space (Vac.). When designing a rocket to get off the launchpad, use the ASL thrust values to determine TWR (Kerbal Engineer Redux appears to compute TWR using the Vac. number instead for some reason... maybe I missed a setting somewhere). The engine thrust values are listed in kilonewtons (kN). To compute your TWR, you need the weight of your rocket in the same units of kN. To obtain this, take your rocket's mass in metric tons and multiply it by the gravity of the celestial body you're on (9.81 kN/ton for Kerbin, I believe). Then simply divide the rocket's thrust by its weight, and you have TWR. If it's greater than 1.0, you can get off the launchpad.

During launch you are fighting two things -- gravity and air resistance. The less time you spend getting to orbit, the better... you use less dV to gravity on your way up if you go quickly. "So why not just make my TWR something like 10.0 then?" Well, there's that other thing -- air resistance -- that you need to worry about. Air resistance increases as your speed increases, and (generally speaking... others will correct me, I'm sure) does so roughly as the the square of the speed increase... double your speed, and air resistance goes up by a factor of 4. A TWR of 10.0 would get you to supersonic speed before you reach 1000m off the launchpad, and you will experience a very strong drag force as a result. You end up using dV to fight the air resistance. As you ascend through the atmosphere, the air density decreases and so does the air resistance; getting out of the lower atmosphere before really piling on the speed helps.

So you end up with a balancing act... you want to get to orbit quickly so that you don't use up too much dV fighting gravity, but you also don't want to get moving so quickly that you use up too much dV fighting air resistance. Tweaking your TWR up or down affects where you are in this balancing act.

Try this experiment:

Build a very simple rocket... a Mk1 Command Pod with a Mk16 Parachute on top, powered by an RT-5 "Flea" Solid Rocket Booster. In the Vehicle Assembly Building, right-click on the booster and set the thrust limiter to some value. Go and launch this test rocket straight up and see how high it goes. Then change the thrust limiter to some other value and repeat the test. You will find that you can get vastly different maximum altitudes, depending on what you set the thrust limiter to. You are effectively dialing up and down the rocket's TWR. Note that the rocket's dV remains constant at 650 m/s, no matter what you set the TWR to.

When I did this experiment, I got the following results

Limiter 100%, TWR 8.70, dV 650 m/s, 4457 m max altitude
Limiter 10%, TWR 0.87, dV 650 m/s, 895 m max altitude
Limiter 25%, TWR 2.17, dV 650 m/s, 5595 m max altitude

With the thrust limiter set at 100%, I observed supersonic shockwave effects on the rocket before it even reached 1000 m.

"Why did you end up with nearly 900 m for a max altitude when the launch TWR was less than 1.0? Shouldn't it have stayed on the launchpad?" Well, it did... for quite a while. As the solid fuel burned off, the rocket got lighter and lighter, and eventually the TWR climbed above 1.0, and up we went! Of course, around 2/3 of the fuel was burned sitting on the pad, fighting gravity and losing.

It turned out that for this rocket, a launch TWR of 2.17 (thrust limiter at 25%) provided the greatest max altitude. Setting the thrust limiter even 0.5% on either side of 25% resulted in lower max altitudes.

All three of these cases used the same 650 m/s dV, but the 2.17 TWR case found the minimum amount of dV lost fighting gravity and air resistance for that test rocket. TWR values higher than this ended up losing more dV fighting increased air resistance, while lower TWR values lost more dV fighting gravity.

Different rocket designs will have different optimal TWR values for getting up out of the atmosphere and into orbit. There is no single perfect TWR number. For example, while the test rocket above liked a TWR of 2.17, my standard LKO tourist rocket would flip around backwards mid-flight if I tried to give it that TWR. It prefers a launch TWR around 1.35. People frequently toss around values between 1.2 and 2.0. Testing is the key here. Also worth noting is that your TWR constantly changes during your ascent, as you are burning fuel and thus losing mass. What started off as a TWR of 1.4 may well end up as a TWR of 3.0 by the time the fuel runs out unless you adjust the throttle somewhere along the way. Don't let your TWR get too high until you are out of the thicker parts of the atmosphere, or else you will end up going too fast and air resistance will teach you a lesson.

So getting to orbit is a matter of sufficient dV and a TWR that gets you to orbit quickly, but doesn't go so fast that you lose a lot of dV moving air out of your way. Then all you need to do is follow a nice ascent profile (piloting skills). The ascent profile gets you up and out of the lower atmosphere promptly, so that you can start going faster, sooner. A nice ascent profile starts off vertical and ends with the rocket in orbit, travelling horizontally, all in one continuous smooth turn. As with TWR, different rockets will require different ascent profiles to maximize efficiency. Some are better off beginning the turn very early, while others need to go straight up a little longer before turning. It has a lot to do with the distribution of mass and drag sources on your rocket. Others have already posted a common ascent profile that works for lots of rocket designs (straight up to around 100 m/s velocity, then turn 5-10 degrees off vertical, and continue turning further and further, aiming for 45 degrees at about 15000 m altitude). By about 50-60 km you should be nearly horizontal, putting all your dV into increasing your orbital speed (going sideways rather than going up).

Hope that helps a bit.

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+1 to PnDB's suggestion to describe your rocket (maybe post a picture).

Broadly speaking, if you're having trouble getting to orbit, it could be a design problem or a piloting problem, and if you don't know which it is, I can see how that would be really frustrating.

So try to narrow it down... post a ship, get a critique. If you can get to a design that you're reasonably confident makes sense, then it's much easier to debug your piloting.

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One thing especially caught my eye (and probably best not to go into TOO much detail, because THIS discussion could take over the thread), the Oberth effect does not give more delta-v, it allows more efficient USE of delta-v.

Also, my usual launch TWR is 1.4 or so (sea-level value, so about 1.54 usually for vacuum value) and I try to have things start to taper off after 1-2k delta-v is used up. I also use Mechjeb and limit acceleration to 20 m/s^2.

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Wow, guys. This has been fantastic, and I really appreciate everything. Way more response than I was expecting, and some great and extremely helpful stuff. Thanks to all of you.

I got home last night and queued up some Scott Manley videos (God bless this man for his

videos), and while most (not all, but most) of the concepts he's covered through the first five episodes are ones I was already in a pretty good place on, there's a big difference between "knowing what things mean" and "watching someone who knows what they're doing". Between his examples and the help here, I was able to put together a basic rocket last night and get it into orbit much, much more painlessly than I had been (and with far fewer parts, to boot). I haven't made any more ambitious flights yet aside from "Get into and back out of LKO", but I feel a lot better about it right now.

As requested, some pictures. Unfortunately, I don't have an exact copy of the ship I had been using to attempt orbit, since I kept starting new campaigns and overwriting the old ones, so the first picture is a rough recreation of about what I would have been using. The top stage has a Mk1 cockpit; Science Jr.; a service bay with two Goo Containers, two Barometers, and two Thermometers, along with a Z-200 battery and an Inline Reaction Wheel thinger); a heat shield; and landing micro-struts to soften the impact / prevent the Science Jr. from blowing up. All of that's topped off with a basic antenna, a Mk16 axial parachute, and two Mk2-R radial parachutes. The "Get into orbit" stage has a FL-T800 fuel tank (or equivalent) and a LV-909 Terrier engine. Finally, two more FL-T800s and an LV-T45 Swivel Engine, four stabilizing winglets, and four Thumper SRBs (sometimes set to all fire at once; sometimes set to fire a pair, jettison, fire the next pair). As you can see, it's a very heavy build, and it handles like a barge (when it handles at all).

(Edit: In the interest of clarification, I built this quickly in Sandbox mode this morning as a rough approximation of something I had previously been working with, which had been done in a prior (now deleted) Science Mode gameâ€â€I wasn't able to build this in my since-aborted Career Mode game that I was trying to run at the time of original posting because I hadn't upgraded my facilities enough to accommodate a rocket of this bulk. In my Science Mode, I don't honestly recall exactly what I was using this for, mission-wiseâ€â€it might have been High Kerbin Orbit, it might have been Munar fly-bysâ€â€but I remember that it always felt like a battle just to get it into LKO reliably in the first place, and that I was always just barely squeaking by (or failing at due to fuel shortage) whatever its "real" mission was. In that Science Mode game, I had managed high- and low-space single-kerbal fly-bys of the Mun when I got lucky, and a lot of aborted attempts to do a lot of other things like go to Minmus or land a probe on the Mun due to resource shortages.)

2015-06-18_00001.jpg

And this is a picture of what I actually used last night to achieve LKO of around 90-100km and then deorbit: The so-called Supercat*. It uses a mostly KW Rocketry parts for the tanks and engine, but can best be summed up as follows: Top stage is similar to the above, only with no service bay. Using two radially-mounted Z-100 batteries instead, no barometers (this is in career mode and I hadn't unlocked them yet), and no landing struts. The upper stage fuel is the KW SA-2 LFT tank, which holds 216 "units" of liquid fuel, making it just slightly less than an FL-T400 + FL-T100, sitting on top of the usual LV-909 Terrier. The lifting stage is a KW SA-4 LFT plus another SA-2 LFT, which between them have 648 "units" of liquid fuel (compared to the 720 "units" above from the two FL-T800s). The engine is, of course, the KW Wildcat-Vâ€â€it has slightly more thrust and slightly better Isp than an LV-T30 Reliant engine, and also has gimbal capability (which I limited to 35%). No boosters.

2015-06-18_00002.jpg

(As an aside, does anyone know why the flag in the background of the Wildcat is the KSP "stock" flag and not the flag I chose for this career?)

* The KW Rocketry engine I used is nicknamed the Wildcat, and I took to naming my rockets based on their primary lift engine. The ship that I used for a suborbital escape from the atmosphere was dubbed the Wildcat, and since this ship that sought to enter orbit was a "souped up" version of its smaller predecessor, it got named Supercat.

Edited by Landwalker
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(As an aside, does anyone know why the flag in the background of the Wildcat is the KSP "stock" flag and not the flag I chose for this career?)

The game does this to me too. . .KSP doesn't update the flag right away when I first load a save. Going to the tracking station gets the game to load the proper flag texture.

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Set up Engineer to show you your 'Atmospheric Efficiency' - your current speed as a % of your current terminal velocity you're going right now. The most efficient ascent is when you travel at terminal velocity all the time, thus Atmospheric Efficiency = 100%. Any higher, you lose fuel to drag, any lower you lose fuel to gravity.

In order to sit at 100% most of the time you will need VERY high TWR 2.0-2.5 on the launchpad until you reach TV, this is easy to accomplish with solid boosters that aren't completely full, you will ditch them very quickly.

Then you use your liquid fuel engines to stay at 100%, since you can throttle them. you should have at least 1.1 TWR after you lose your solid boosters.

Eventually you get high enough that the terminal velocity gets very very high, so your Atmo Efficiency drops a lot. Here a powerful engine could be very useful, however an engine like that will probably be too heavy to bring up to 50+ km, so don't worry about atmospheric efficiency once you go above 35 km.

If you're still having problems, post screenshots of the craft in VAB.

Edited by tutike2000
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(Kerbal Engineer Redux appears to compute TWR using the Vac. number instead for some reason... maybe I missed a setting somewhere).

Just click the "Atmosphere" button at the top of the KER window in the VAB to make it simulate atmospheric conditions. You will also get sliders to adjust the simulated altitude and velocity (velocity only makes a different for jet engines).

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