Trying to reach Mun, any advice?

[Tokoshoran]

Some launches after I finally got a satellite into low orbit, I took on a mission which required me to launch another satellite to a specific orbit. I figured it'd be an easier one, only to need to launch it slightly beyond Mun. After a few failures I decided to work on other jobs, and eventually came back and managed to do it.

I figured, hey, if I could reach a Mun-like orbit, surely I could slap a few struts onto a manned rocket and get it up there with some science experiments, but after testing around with a few different parts, I'm finding it difficult to even get up there. Maybe I hit the sweet spot on my satellite launch, or maybe I'm just using the wrong parts now. I have everything up to the 90-science research, of which I only have Electricity (recharging my reaction wheel is vital). Looking back at the Into Orbit build, it used Hammers instead of Thumpers, AV-R8 instead of Tail Fins, etc. Where do advantages and disadvantages lie with the various pieces I have available?

[Snark]

24 minutes ago, Tokoshoran said:

Where do advantages and disadvantages lie with the various pieces I have available?

Going to the Mun doesn't really require much more advanced tech than just getting to LKO.  It does take about one Kerbin day to make the transition, so you probably want to have batteries and/or solar panels available, but even those aren't an absolute requirement if you're careful with your electricity usage and don't have a probe core sucking power the whole time.

It can even be done under the 18-ton limit of the level-1 launchpad, and under the 30-part limit of the level-1 VAB, though upgrading the launchpad once can make things a bit easier on you.  (Upgrading the launch pad one level, so you can go over 18 tons, can be handy, though-- lets you add a couple of Thumpers to get going, and those guys are heavy.)

Basically, all you need to get to the Mun is an extra 850 m/s of dV after reaching low Kerbin orbit.  If you want to brake to low Mun orbit, that'll be another couple hundred, then it'll be another couple hundred to return to Kerbin if that's what you're doing.  Landing on the Mun takes another 600+ m/s from low Mun orbit, with another 600+ to return.

As for how to get there:

Picture this top stage.  Mk1 command pod, heat shield, decoupler, 2-ton LFO tank, Terrier engine, parachute.  (Plus whatever other little odds and ends you need, like antenna, batteries, science instruments, etc.  They don't mass much.)  That combination right there has nearly 2500 m/s of dV, which is enough to go from LKO, to the Mun, capture to low Mun orbit, then return to Kerbin, with something like 1000 m/s of dV left over.

So.  Build that top stage, then all you need to do is to put a booster stage under it that's capable of getting that stage most of the way to orbit.  If you can do that, you're home free.  You can do that, for example, by putting a 4-ton LFO tank under it with Swivel, and then some SRBs to get it off the pad and on its way.

Main thing is to make sure you're navigating reasonably efficiently.  Get to LKO first.  Go to map view, rotate it so you're looking straight down at Kerbin's north pole.  Rotate the view so that the Mun is located at about the 2:00 position, or perhaps 2:30.  Drop a maneuver node at 6:00, drag it until you get a Mun intercept, keep dragging until you get your Mun Pe down to something low like 15 km.  (This should take you about 850 m/s on the maneuver node).  There, done. 

[Tokoshoran]

What building do I need to upgrade to get maneuvers? They're not available for me.

[Snark]

3 minutes ago, Tokoshoran said:

What building do I need to upgrade to get maneuvers? They're not available for me.

Two buildings.  Mission Control, and Tracking Station.

(Upgrading just the tracking station will give you patched conics, meaning you'll be able to see where and how you'll intercept the Mun's SOI, what your projected Pe will be, etc., but you won't be able to actually place a maneuver node until you've upgraded Mission Control, too.)

That said, though, you can do a Mun trip even if you haven't upgraded either one, i.e. without maneuver nodes.

Just do the same thing described above (go to map view, put the Mun at about 2:00 or 2:30), wait until your ship is at 6:00, then burn until your Ap is out at the Mun's orbit.  That'll get you there.  Once you enter the Mun's SOI, you'll be able to see your path past the Mun, which might be on a collision course, so you'll likely need to do a correction burn, but it won't be a big one if you do it as soon as you enter the SOI.

[radonek]

37 minutes ago, Snark said:

Just do the same thing described above (go to map view, put the Mun at about 2:00 or 2:30), wait until your ship is at 6:00…

There is IMO easier way. On low circular equatorial orbit, burn when Mun is rising over horizon. That's it.

[GoSlash27]

2 hours ago, Snark said:

Just do the same thing described above (go to map view, put the Mun at about 2:00 or 2:30), wait until your ship is at 6:00, then burn until your Ap is out at the Mun's orbit.  That'll get you there. 

Or even easier: Go to flight view, point , and step on the gas once you see the Mun rise above the horizon. Then go to map view and shut it off once your Ap reaches the Mun's orbit around Kerbin. This is the standard "caveman" way of doing it.

*EDIT* @radonek beat me to it.
 

 

2 hours ago, Snark said:

Landing on the Mun takes another 600+ m/s from low Mun orbit, with another 600+ to return.

 I personally double the DV budget for landing. A lot of unforseen circumstances tend to crop up during landings...

 This means that while a manned landing and return is technically possible with starting facilities, it's not recommended due to lack of safety margin.
 If you engineer everything *just right*, you could just barely make it... But if you know enough to pull that off, you'd also know that you really shouldn't risk it.

You should at least upgrade the pad before attempting a manned Mun landing.
*EDIT* And besides... you can't properly "science" at that point anyway. Can't EVA, can't collect soil samples or the science from your experiments before reentry. Better to save the "one small step" for when most of the facility is level 2.

Best,
-Slashy

Edited March 21, 2018 by GoSlash27

[Tokoshoran]

Can't seem to boost myself into orbit anymore. Maybe my science gear is just too dang heavy.

 

28 minutes ago, GoSlash27 said:

Or even easier: Go to flight view, point , and step on the gas once you see the Mun rise above the horizon. Then go to map view and shut it off once your Ap reaches the Mun's orbit around Kerbin. This is the standard "caveman" way of doing it.

*EDIT* @radonek beat me to it.
 

 

 I personally double the DV budget for landing. A lot of unforseen circumstances tend to crop up during landings...

 This means that while a manned landing and return is technically possible with starting facilities, it's not recommended due to lack of safety margin.
 If you engineer everything *just right*, you could just barely make it... But if you know enough to pull that off, you'd also know that you really shouldn't risk it.

You should at least upgrade the pad before attempting a manned Mun landing.
*EDIT* And besides... you can't properly "science" at that point anyway. Can't EVA, can't collect soil samples or the science from your experiments before reentry. Better to save the "one small step" for when most of the facility is level 2.

Best,
-Slashy

What should I be sciencing, then? Should I be trying to orbit around to the "Above altitude" mission objectives (and if so, how do I go about ensuring I actually am above them, even when I normalize/abnormalize my orbit to look like it's going over the point it doesn't work)? I can EVA but I can't collect samples yet.

Edited March 21, 2018 by Tokoshoran

[GoSlash27]

Tokoshoran,
 It'd depend on what capabilities you currently have and how much of a hurry you're in. Mun flyby science (high and low) is easily achievable in early caveman using probes, as is Minmus surface science. And of course, you have Kerbin itself and low/ high space.

 The most powerful "caveman" rocket I've constructed so far uses a reliant and 4 twitches for vernier + additional thrust in the first stage (no fins), and a Terrier for the 2nd. This can place up to 3.8 tonnes in LKO, which can accomplish a lot. Perhaps that would be able to get your experiments up there?

 Best,
-Slashy

[Streetwind]

9 hours ago, Tokoshoran said:

Can't seem to boost myself into orbit anymore. Maybe my science gear is just too dang heavy.

Or perhaps some of your issues in general lie with piloting.

I'm not trying to be mean to you - it's just that KSP is a game where personal skill has an extremely large impact, and at the same time, those skills can take a good long while to learn. Especially when one gets used to solving piloting problems by overbuilding rockets instead of practising how to fly well. It's a trap that a lot of new players fall into. I once fell into this trap and got frustrated, too.

Try and build the following training rocket: Mk1 pod with a mk16 parachute on top. 1.25m heatshield below it. 1.25m decoupler. Two FL-T800, or equivalent (four FL-T400, or eight FL-T200). Finally, a Swivel engine.

Put a pilot Kerbal into it. Your mission: launch this Kerbal into orbit, and then return him/her safely to the surface of Kerbin.

This training rocket is built in a way that makes an experienced player go "that's a comfortable margin", while it makes a new player go "how can that possibly ever get into orbit?!" It intentionally does not have fins for stability, so you need to focus on steering thoughtfully; and it intentionally only has a single stage, so you have to manage your engine throttle. It is not the most comfortable and easy rocket to fly. But it is perfectly capable of doing the job, and it might teach you something along the way.  

If you can get this into orbit on the first or second try, then congratulations: piloting is probably not your problem. You're good enough to fly efficiently. If it takes you more than that - practise until you can successfully (and reliably, repeatedly) pull it off, and then see if you can apply the same techniques you just learned to your own rockets, and if that helps them get into orbit better as well.

Edited March 22, 2018 by Streetwind

[Gogi]

If electricity is problem I'd recomend a free return. You will need manouver nodes unlocked. Just get into circular orbit (doesn't have to be circular, but it is a lot easier). Place a node. Pull prograde until it shows somewhere around 13.5M. Than move the node around the orbit until you get a loop around the Mun. Than tweak prograde, retrograde until you get Mun PE above 12k and Kerbin Pe bellow 40k. After you execute shut down everything. The only power you need now is to turn retrograde when you enter Kerbin atmo.

[Orc]

Hi all and in particular Tokoshoran

 

My experience is that if you can get into LKO you can upgrade that launch vehicle to 18 tons (the maximum mass allowed by the starting launch pad) and with some careful planning do a Munar Flyby and back. The hints suggests by others in this thread about how to achieve your Flyby trajectory sound right. The minimum technology level needed is the tech that unlocks the Terrier rocket engine, because trying to do the burn to a Munar Flyby with a Reliant is just plain stupidly hard (I am sure it can be done - but I am not doing it). 

 

Your problem is going to be Electricity. If you don't bring a battery you are going to find your reserves getting awfully low by the time your Munar Flyby-er starts the homeward bound part of its trajectory. You can avoid this by turning off SAS as soon as the Munar Flyby burn is completed. Without batteries you can not even dream of taking an antenna along to transmit data back. 

To maximize your scientific return on the way to and from the Mun, pack try pack four Mystery Goo containers, and do EVAs while in Kerbin's orbit, while in Space High above Kerbin, and in Space high above the Mun. A well planned and executed Munar flyby can net you enough Science to unlock the parts necessary for a Munar orbit mission and possibly even a Munar landing.

You don't need a heat shield for the aerobraking, unless you have really messed things up (like getting the pre-re-entry periapsis below 35Km) the Mk1 capsule can manage the re-entry heat abuse. 

 

Anyway, take care, have fun, and try not to kill too many Kerbals.

 

Regards

Orc

 

[Tokoshoran]

22 hours ago, Streetwind said:

Or perhaps some of your issues in general lie with piloting.

I'm not trying to be mean to you - it's just that KSP is a game where personal skill has an extremely large impact, and at the same time, those skills can take a good long while to learn. Especially when one gets used to solving piloting problems by overbuilding rockets instead of practising how to fly well. It's a trap that a lot of new players fall into. I once fell into this trap and got frustrated, too.

Try and build the following training rocket: Mk1 pod with a mk16 parachute on top. 1.25m heatshield below it. 1.25m decoupler. Two FL-T800, or equivalent (four FL-T400, or eight FL-T200). Finally, a Swivel engine.

Put a pilot Kerbal into it. Your mission: launch this Kerbal into orbit, and then return him/her safely to the surface of Kerbin.

This training rocket is built in a way that makes an experienced player go "that's a comfortable margin", while it makes a new player go "how can that possibly ever get into orbit?!" It intentionally does not have fins for stability, so you need to focus on steering thoughtfully; and it intentionally only has a single stage, so you have to manage your engine throttle. It is not the most comfortable and easy rocket to fly. But it is perfectly capable of doing the job, and it might teach you something along the way.  

If you can get this into orbit on the first or second try, then congratulations: piloting is probably not your problem. You're good enough to fly efficiently. If it takes you more than that - practise until you can successfully (and reliably, repeatedly) pull it off, and then see if you can apply the same techniques you just learned to your own rockets, and if that helps them get into orbit better as well.

I don't doubt that lack of skill is the problem, while I've learned a number of the other tricks, existing the atmosphere fluidly is not one of them. Even after repeatedly doing that tutorial mission over and over. I'll go ahead and try out the recommended build and probably swap back into the tutorial a few times to try and hammer the skill in.

Edited March 23, 2018 by Tokoshoran

[Gargamel]

On 3/21/2018 at 5:30 PM, GoSlash27 said:

Or even easier: Go to flight view, point , and step on the gas once you see the Mun rise above the horizon. Then go to map view and shut it off once your Ap reaches the Mun's orbit around Kerbin. This is the standard "caveman" way of doing it.

I was going to suggest this too.  This is how we used to do it before we had manuever nodes in the game at all. 

[Tokoshoran]

On 3/22/2018 at 12:35 AM, Streetwind said:

Try and build the following training rocket: Mk1 pod with a mk16 parachute on top. 1.25m heatshield below it. 1.25m decoupler. Two FL-T800, or equivalent (four FL-T400, or eight FL-T200). Finally, a Swivel engine.

Put a pilot Kerbal into it. Your mission: launch this Kerbal into orbit, and then return him/her safely to the surface of Kerbin.

This training rocket is built in a way that makes an experienced player go "that's a comfortable margin", while it makes a new player go "how can that possibly ever get into orbit?!" It intentionally does not have fins for stability, so you need to focus on steering thoughtfully; and it intentionally only has a single stage, so you have to manage your engine throttle. It is not the most comfortable and easy rocket to fly. But it is perfectly capable of doing the job, and it might teach you something along the way.  

If you can get this into orbit on the first or second try, then congratulations: piloting is probably not your problem. You're good enough to fly efficiently. If it takes you more than that - practise until you can successfully (and reliably, repeatedly) pull it off, and then see if you can apply the same techniques you just learned to your own rockets, and if that helps them get into orbit better as well.

Hmm, looking into how the Tutorial works, I go straight up until 60m/s, then curve to 70º until the boosters die off, around 400m/s. Finally, once the Ap reaches 80k, cut throttle and wait until you're over 70k altitude, and then burn around 15º.

...On a west heading, following these directions gets me to the desert, which is a new biome for doing some reports, but I'm definitely not reaching orbit. In my goal to reach Mun, I suppose my first step definitely needs to be entering orbit with a "comfortable margin" ship. My reading into the tutorial must be looking at the wrong things, or else the boosters throw it off that much, so what do I have to do?

[Streetwind]

1 hour ago, Tokoshoran said:

Hmm, looking into how the Tutorial works, I go straight up until 60m/s, then curve to 70º until the boosters die off, around 400m/s. Finally, once the Ap reaches 80k, cut throttle and wait until you're over 70k altitude, and then burn around 15º.

One thing to keep in mind that things like "your heading and/or speed should be this when the boosters cut off" is extremely vessel-specific. The tutorial tells you this because it is holding your hand and guiding you with respects to the tutorial rocket, but it won't help you with something like this training rocket, which doesn't have any boosters that cut out. In fact, it doesn't even stage.

So you're going to have to do this scary thing called "knowledge transfer" that we all used to hate in school, where the questions in the exams were not the same ones we knew from the textbooks, and we had to apply what we learned in new ways. In this case, you'd examine the general situation the tutorial rocket it is when the boosters cut out. You'll be at a certain altitude, going a certain speed, pitched at a certain angle, having flown a certain shape of trajectory from the pad. Maybe you can reproduce that combination of factors with a different vessel, too. Maybe it'll work for that rocket, or you'll find that you'll be too steep, or too shallow. And it gives you information over the arc (the so-called gravity turn) your vessel is taking from being vertical on the pad to being horizontal in orbit. The largest part of being good at launching rockets is being able to judge how well that turn is going for you, based on the individual characteristics of the rocket you're currently flying. And that takes a lot of experience to get right in a reliable fashion.

...That said, there are a few rules of the thumb that work with almost any rocket. Meaning, with all rockets that have a reasonable thrust/weight ratio and stage distribution. The most widely circulated key indicator for a good flight path is the rule of hitting a 45 degree pitch at 10 kilometers altitude. If your rocket has low-ish thrust, you probably want to be a little steeper (hitting that pitch only at 12 km, for example), and if you're going like a bat out of hell, you'll want to be more shallow. The training rocket is special in the way that it doesn't stage at all, so it isn't approaching a stage burnout at that point, and has a little less thrust than a two-stage rocket in the first half of the flight. But at the same time, it's going to have a massive overabundance of thrust in the second half of the flight. This is part of what makes it a little tricky to fly. But with some throttle work, you should be able to emulate a weaker second stage engine where it's convenient for you.

Another one is not letting your time to apoapsis (visible in map mode when mousing over the apoapsis) come too close to you, or run away from you. Having it between 40 and 60 seconds is very good. If it falls to 30 seconds, you'll probably want to pitch up and increase the rate at which you gain altitude, unless you are already most of the way to orbit. If it's climbing past 70 seconds, you want to flatten out your trajectory, and/or throttle down. In both cases, beware of straying too far from the prograde marker on your navball while you are still below ~35km.

 

1 hour ago, Tokoshoran said:

...On a west heading, following these directions gets me to the desert, which is a new biome for doing some reports, but I'm definitely not reaching orbit.

And here's another one of those rules of the thumb that work with ny rocket: Don't launch on a west heading unless you absolutely, positively have a mission requirement to do so. Always launch on an east heading instead.

Launching westwards puts you into something called a retrograde orbit, meaning you're orbiting against the rotation fo the planet. Launching east puts you in a prograde orbit, with the rotation of the planet. And that is important, because it has an effect on your dV cost to orbit. Launching with the rotation of Kerbin gives you the speed of that rotation for free; launching against it, you have to first zero out the rotation and then also pay for the amount you are not getting for free. One case gives you an extra 175 m/s for free, the other one costs you an extra 175 m/s. And while the training rocket I gave you has margin, a difference of 350 m/s will mean it's probably not getting into orbit unless the pilot works a sheer miracle. And even then, it'll probably be stuck up there without the fuel to deorbit again.

(A polar orbit, launching south or north, is in the middle of the two extremes - you neither get any bonus, nor do you have to pay any penalty. The training rocket is capable of a polar orbit if flown really well.)

So, for starters, get used to launch on a strict east heading whenever at all possible, and see if that makes a difference in how well you get to orbit.

 

Edited March 23, 2018 by Streetwind

[Tokoshoran]

12 minutes ago, Streetwind said:

One thing to keep in mind that things like "your heading and/or speed should be this when the boosters cut off" is extremely vessel-specific. The tutorial tells you this because it is holding your hand and guiding you with respects to the tutorial rocket, but it won't help you with something like this training rocket, which doesn't have any boosters that cut out. In fact, it doesn't even stage.

So you're going to have to do this scary thing called "knowledge transfer" that we all used to hate in school, where the questions in the exams were not the same ones we knew from the textbooks, and we had to apply what we learned in new ways. In this case, you'd examine the general situation the tutorial rocket it is when the boosters cut out. You'll be at a certain altitude, going a certain speed, pitched at a certain angle, having flown a certain shape of trajectory from the pad. Maybe you can reproduce that combination of factors with a different vessel, too. Maybe it'll work for that rocket, or you'll find that you'll be too steep, or too shallow. And it gives you information over the arc (the so-called gravity turn) your vessel is taking from being vertical on the pad to being horizontal in orbit. The largest part of being good at launching rockets is being able to judge how well that turn is going for you, based on the individual characteristics of the rocket you're currently flying. And that takes a lot of experience to get right in a reliable fashion.

That's easily a major problem for me. If I'm told to look for something, I take the directions literally and look for those specific circumstances. Vaguer explantions may take more time to figure out, but they're so much more worth it for me.

15 minutes ago, Streetwind said:

...That said, there are a few rules of the thumb that work with almost any rocket. Meaning, with all rockets that have a reasonable thrust/weight ratio and stage distribution. The most widely circulated key indicator for a good flight path is the rule of hitting a 45 degree pitch at 10 kilometers altitude. If your rocket has low-ish thrust, you probably want to be a little steeper (hitting that pitch only at 12 km, for example), and if you're going like a bat out of hell, you'll want to be more shallow. The training rocket is special in the way that it doesn't stage at all, so it isn't approaching a stage burnout at that point, and has a little less thrust than a two-stage rocket in the first half of the flight. But at the same time, it's going to have a massive overabundance of thrust in the second half of the flight. This is part of what makes it a little tricky to fly. But with some throttle work, you should be able to emulate a weaker second stage engine where it's convenient for you.

Another one is not letting your time to apoapsis (visible in map mode when mousing over the apoapsis) come too close to you, or run away from you. Having it between 40 and 60 seconds is very good. If it falls to 30 seconds, you'll probably want to pitch up and increase the rate at which you gain altitude, unless you are already most of the way to orbit. If it's climbing past 70 seconds, you want to flatten out your trajectory, and/or throttle down. In both cases, beware of straying too far from the prograde marker on your navball while you are still below ~35km.

Thanks, that gives me something to work off of. I didn't even think of looking at the time to apoapsis.

42 minutes ago, Streetwind said:

And here's another one of those rules of the thumb that work with any rocket: Don't launch on a west heading unless you absolutely, positively have a mission requirement to do so. Always launch on an east heading instead.

Launching westwards puts you into something called a retrograde orbit, meaning you're orbiting against the rotation fo the planet. Launching east puts you in a prograde orbit, with the rotation of the planet. And that is important, because it has an effect on your dV cost to orbit. Launching with the rotation of Kerbin gives you the speed of that rotation for free; launching against it, you have to first zero out the rotation and then also pay for the amount you are not getting for free. One case gives you an extra 175 m/s for free, the other one costs you an extra 175 m/s. And while the training rocket I gave you has margin, a difference of 350 m/s will mean it's probably not getting into orbit unless the pilot works a sheer miracle. And even then, it'll probably be stuck up there without the fuel to deorbit again.

(A polar orbit, launching south or north, is in the middle of the two extremes - you neither get any bonus, nor do you have to pay any penalty. The training rocket is capable of a polar orbit if flown really well.)

So, for starters, get used to launch on a strict east heading whenever at all possible, and see if that makes a difference in how well you get to orbit.

 

I didn't think that would play any effect  I guess that explains the weird behavior of the arc.

[90VG]

I just tried that MK1, Coupler, 2 FL800 tanks and a swivel.  Gives me 3790 d/v.  I did a nice climb to 80km, tried to circularize and the PE stopped at 44km.   That isn't enough.  I don't have MechJeb ascent on this playthrough, but I doubt it could make it to 80km.  When I get to the launch pad, Kerbal Engineer says 2900 d/v.  That doesn't really seem like enough to make it to me.  I kept it below 250 m/s until 10k, then tilted over to 45.  I left power at 2/3rds, once about 30k I opened up the throttle.  I got my AP to 72K on 2nd attempt, but that just made more time in the air and I was not able to get to orbit.

This is version 1.3.1, and I have gone to the moon and mun, landed, came back, but with KE showing 3K d/v on the launch pad???

Screenshot of it sitting on the pad:  

@Streetwind

[GoSlash27]

90VG,
1) How did you come up with the "3,790 m/sec DV" figure? My calculation says that rocket will only do 2,388 m/sec (assuming you didn't remove the monoprop). Nowhere near enough to achieve orbit.
 *Edit* correction. I calculated it with a single FL-T800. With 2 tanks, I get 3,178 m/sec DV. Close if you fly it absolutely perfectly, but still probably not gonna make it.

2) You shouldn't climb to 10 km and then pitch 45°. Your nose should start falling prograde almost from the start so you wind up pointed 45° around 10 km.

3) You shouldn't throttle back to limit your speed, you should throttle back to limit your acceleration. This won't save you any DV either, it's just for controlling heat and aerodynamic stability.

HTHs,
-Slashy
 

 

Edited March 24, 2018 by GoSlash27

[Streetwind]

12 hours ago, 90VG said:

I kept it below 250 m/s until 10k, then tilted over to 45.

Then you are following extremely outdated techniques This kind of flight path was used during KSP's beta period. With the first full release in April of 2015, the aerodynamics model was made much more realistic, and you'll now fare much better if you fly a smooth, gradual turn, and stay at full throttle at all times unless you need to flatten your trajectory.

Advice on the topic of advice: make sure the advice you're relying on is relevant to the version of KSP you're playing!

Oh, and: the dV measure you're seeing on the pad is atmospheric dV. It is lower than the vacuum dV you get shown in the editor, unless you tell KER to show you atmospheric dV in the editor as well.

 

That said: I must admit I misremembered. I thought the variant with the heat shield had 3790 m/s vacuum dV. Turns out it only has 3567 m/s. Derp!  So for @Tokoshoran, I recommend to take the heat shield off for starters. You can put it back on when you feel more comfortable.

The variant with heat shield is still perfectly capable of reaching an equatorial orbit with enough fuel left to deorbit again. Here's proof in a video I just recorded. (Please excuse the low resolution and framerate - I'm still searching for good recording settings that keep the filesize low.) If Dropbox is acting prissy about playing it in the browser, as it often happens for me, then use the download button in the top right.

 

@GoSlash27 - you must be miscalculating then, because 90VG is using Kerbal Engineer, and that's showing the correct value.

 

Edited March 24, 2018 by Streetwind

[GoSlash27]

1 hour ago, Streetwind said:

you must be miscalculating then, because 90VG is using Kerbal Engineer, and that's showing the correct value.

Streetwind,

 I did miscalculate the first time, but 3,178 m/sec is actually closer to correct than KER. It doesn't account for partial atmospheric flight, whereas I do. If I calculate it as pure vacuum, I get 3,568 m/sec which agrees with KER's prediction.

Best,
-Slashy
 

Edited March 24, 2018 by GoSlash27

[Streetwind]

Yeah, if you account for atmospheric flight, you'll get a lower value. 90VG was having KER show vacuum dV only, though, on a variant of the rocket without the heat shield. And for that case, 3,790 m/s is indeed correct. It's also the amount I meant to provide Tokoshoran with, but I screwed up.

[GoSlash27]

Streetwind,

 My figures assume he didn't bother to remove the monoprop, but *did not* have a heat shield. With a heat shield and assuming pure vacuum as KER does, I get 3,390 m/sec. You might want to double check that.

Best,
-Slashy

[GoSlash27]

1 hour ago, Streetwind said:

Yeah, if you account for atmospheric flight, you'll get a lower value.

Streetwind,
 The problem isn't just that KER gives 2 different answers depending on how it's set. The problem is that it gives incorrect answers in both cases. The vacuum DV is wrong because the rocket doesn't spend all of it's time in vacuum. The atmospheric DV is wrong because the rocket doesn't spend all of it's time at 1 ATM.
 KER is flat- out incorrect every time it is used for an atmospheric stage, so how do we decide the "true" DV? Is it KER vacuum numbers because that's what KER says? Is it calculated by a mean atmospheric density, as I do it? Or is it the actual value, which can never be calculated, only simulated?

 If we're building a subway map and we want to state the DV to orbit, what number should go in that box?

Apologies for the off- topic pedantry I guess my point is "never assume KER is right, because it's usually not".

Best,
-Slashy

[Streetwind]

1 hour ago, GoSlash27 said:

 My figures assume he didn't bother to remove the monoprop, but *did not* have a heat shield. With a heat shield and assuming pure vacuum as KER does, I get 3,390 m/sec. You might want to double check that.

The only way that can be is if our rockets are somehow not identical. The training rocket as I built it, with heat shield included and no resources removed, masses 11.780 tons wet, 3.780 tons dry.

ln(11.78/3.78) * 9.80665 * 320 = 3567.045

If you get 3390, then you have some additional mass on there that I don't have. (EDIT: yeah, that works out for a wet mass of 12.11 tons, so you're carrying an extra 330 kg somewhere.)

 

41 minutes ago, GoSlash27 said:

 The problem isn't just that KER gives 2 different answers depending on how it's set. The problem is that it gives incorrect answers in both cases. The vacuum DV is wrong because the rocket doesn't spend all of it's time in vacuum. The atmospheric DV is wrong because the rocket doesn't spend all of it's time at 1 ATM.
 KER is flat- out incorrect every time it is used for an atmospheric stage, so how do we decide the "true" DV? Is it KER vacuum numbers because that's what KER says? Is it calculated by a mean atmospheric density, as I do it? Or is it the actual value, which can never be calculated, only simulated?

 If we're building a subway map and we want to state the DV to orbit, what number should go in that box?

Apologies for the off- topic pedantry I guess my point is "never assume KER is right, because it's usually not".

My solution to that problem is quite simple, really. Let me explain:

The error that is introduced when using vacuum dV to estimate launch costs from an atmospheric body depends on the spread between sea level and vacuum Isp of the engine used in the launch stage. The larger the difference between the two, the more wrong it is.

Now, when a dV map says that it takes 3500 m/s vacuum dV to get into low Kerbin orbit, that figure already has some of the error "built-in", because it is a figure either derived from, or confirmed by, empiric experimentation with real rockets. Which means: if there was an engine that didn't change Isp between sea level and vacuum at all, it would need less dV than the dV maps advertise; their figures are meant for an engine that already loses some performance to the atmosphere.

Of course, if you use an engine with an especially large spread between sea level and vacuum performance, that number is going to be wrong again, this time in the other direction.

Here's the thing, though: an engine with an especially large performance spread stops being useful as a launch engine. KSP's engines have extremely little thrust-weight ratio to begin with, and if the thrust is further gimped by atmospheric pressure, trying to use it to muscle something heavy off the pad becomes pointless. This is why nobody lights an LV-N on the pad... it just doesn't work.

So how big can the error, the deviation from the figure provided by dV maps, possibly become? Not very large at all, as it turns out. We don't have any engines that don't gain Isp as pressure drops, so the error on the upper bound is extremely limited; and we don't really have any engines useful for launching off the pad that have a larger performance spread than that of the Swivel, so the error on the lower bound is extremely limited. So limited, in fact, that I would argue that hitting the right trajectory for your available thrust is far more important than fussing about dV calculation.

Once I realized this, I shrugged my shoulders and said "screw it, I'll just use vacuum dV for everything". It's the KISS principle, and I am a very lazy person by nature. And in practical application, this approach has never failed me.

 

Edited March 24, 2018 by Streetwind

[Tokoshoran]

2 hours ago, Streetwind said:

14 hours ago, 90VG said:

I kept it below 250 m/s until 10k, then tilted over to 45.

Then you are following extremely outdated techniques @Tokoshoran This kind of flight path was used during KSP's beta period. With the first full release in April of 2015, the aerodynamics model was made much more realistic, and you'll now fare much better if you fly a smooth, gradual turn, and stay at full throttle at all times unless you need to flatten your trajectory.

Not sure why you'd call that out to me, I've been trying to arc it. I'll probably resort to limiting the reaction wheel's authority early on so that I can eventually hold it and get that.