MacLeod-Industries

Over 400 hours in KSP... and apparently I have never orbited correctly.

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9 hours ago, HebaruSan said:

Since we're supposed to start vertical and gradually turn to 45° by 10 km altitude, I tend to treat the upper-eastern quadrant of the nav ball as a progress bar correlated to my altitude. If I'm X% of the way to 10 km, then both my prograde vector and my nosecone should be pointing about that far through the turn at that point. This gives me a way to get back on track if my initial tilt off the pad is too strong or too weak; I can switch to stability assist to get my prograde vector where it should be, then lock prograde.

ZAZT4Xs.png

(Note, nosecone and prograde vector are misaligned in this picture because I borrowed it from someone's blog before adding the numeric annotations.)

I do VERY similar to this, but with double the numbers and looking at my Apoapsis instead of current altitude. So when my Apoapsis is 20km, I'm about at the 40 on the navball.

The reason I do this is it's a lot more TWR agnostic. If your TWR is too low, it takes longer to get your Ap up to 20 so you tend to aim up more. If it's high, your Ap rockets up to 20 quickly so you need to crank it down more aggressively. Of course, TWR too low or too high is bad but still. I like it :)

Of course, the stock game doesn't tell you your Ap height without having to switch views and click on stuff (over and over as you switch views back and forth) so I recommend KER to tell you your Apoapsis (and dozens of other things) in flight view.

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13 hours ago, Rocket In My Pocket said:

Especially when going to the Mun for example, you can just leave the science parts on the surface and take the data with your Kerbal back into space, and back home to Kerbin.

I usually leave behind stuff like Science Jr. and Mystery Goo, but I generally like to bring back the small lightweight science experiments so that I can recover some of the cost.  Some of those experiments get a little pricey, so why throw them away if we don't have to. 

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Oh. Was somebody inspired my thread?

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So I did a simple test using the readouts from MechJeb for gravity and drag losses. (These have to be selected manually and added to a window.)  Full info is in the descriptions.  

TL;DR - Higher TWR and a more aggressive start to the gravity turn will result in lower delta V cost to orbit, and lower total losses from gravity and drag combined.

 

Edited by Norcalplanner
typos

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On 7/7/2016 at 7:25 AM, MacLeod-Industries said:

I am approaching 450 hours in KSP. I have accomplished many achievments...

I have:

landed on the moon... once (I never returned because I can't dock a lander to an orbiter... I was going to land again, but my new heavy lifter rocket was super glitchy for some reason. Testing the stages seperate it would have had enough delta V to go there and back... Possible even to minmus.)

Made a plane that goes suborbital with only jet engines

recreated Apollo 11

Made a rocket to carry my Saturn V rocket into orbit (WHILE it is thrusting down!)

 

While I have never recreated Apollo 11 I have recreated many Apollo 1 and 13 missions... 

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Am I the only one who is usually flat by 30km?

I think I OD'd on RSS and 64k a few months ago.

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  Well, I'd like to say that there is no such thing as a perfect orbit.

"PERFECT ORBIT!"

                        -Jacksepticeye 

he's wrong.

   Secondly, the average required /\v is 3600m/s. However, if you to launch straight up, and then do a prograde burn at the apoapsis to orbit, the required /\v would be around 4200m/s. That's the maximum required /\v to get into orbit. Just remember to have your orbit's apoapsis and periapsis must be above 70km, otherwise you'll enticing and leaving the atmosphere. Another useful tip is to make sure your rocket is angled to 45 degrees before 10km.

  That's a lot more typing then I expected, and I there are more helpful recommendations out there, but these are mostly the basic principles of launching a rocket into orbit.

  Good job renacting the Apollo 11!

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On 2016-07-07 at 3:58 PM, Van Disaster said:

MaxQ isn't really a problem in FAR either, because these parts are so enormously strong. Aero losses on Kerbin are tiny, don't worry about them. Aero losses in real life are also tiny ( 50m/s for Saturn V I think, about 250m/s for current satellite launchers ).

This is in many ways a function of rocket size. Bigger rockets lose proportionately less energy to drag, and also tend to have lower TWRs (Apollo's liftoff TWR was around 1.1, as I recall). KSP actually models this, too; try building 0.625m meter rockets and it feels like you're flying in molasses. :(

 

On 2016-07-07 at 2:08 PM, Norcalplanner said:

One thing to keep in mind - ignore the heating visual effects on ascent.  Unless you actually have thermometers popping up on your parts, there's no need to slow down.  The benefit in reducing gravity losses far outweighs any minor increase in aero losses.

 

Ironically enough the only planet I've ever found the need to throttle down on ascent on is actually Eve. Even going straight up to clear the soup as quickly as possible, the huge thrust gains as your engines get into the upper atmosphere can get you moving so fast your capsule blows. :(

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4 minutes ago, foamyesque said:

This is in many ways a function of rocket size. Bigger rockets lose proportionately less energy to drag, and also tend to have lower TWRs (Apollo's liftoff TWR was around 1.1, as I recall). KSP actually models this, too; try building 0.625m meter rockets and it feels like you're flying in molasses. :(

I thought some of it was current launchers being chubbier, but Ariane 5 diameter/height is the same as S-V ( although that's the first S-V stage presumably ). S-V is definitely more conical overall.

This thing seemed ok, but then width/height is very low ( and it was a test for my own amusement rather than useful... )

27179027670_4781ea41db_c.jpg

0.625 spaceplanes are handy things though.

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17 minutes ago, Van Disaster said:

I thought some of it was current launchers being chubbier, but Ariane 5 diameter/height is the same as S-V ( although that's the first S-V stage presumably )

I don't mean diameter in proportion to height, I mean absolute size. The same proportions, scaled up, will lose less energy to drag. It's a consequence of the square-cube law. Same reason long-distance planes are generally big, or why terminal velocity for a boulder is higher than a rock chip. The Ariane is half the diameter and half the height of the Saturn, and masses about 1/8th of what the Saturn does; and so it has larger drag losses.

KSP accurately reflects this. I built a rocket that hits orbit on under 650kg, but my deltaV budget is well in excess of what I'd need for larger ones, simply because the drag losses are so much larger.

 

Edited by foamyesque

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On 2016. július 7. at 4:25 PM, MacLeod-Industries said:

I am approaching 450 hours in KSP. I have accomplished many achievments...

I have:

landed on the moon... once (I never returned because I can't dock a lander to an orbiter... I was going to land again, but my new heavy lifter rocket was super glitchy for some reason. Testing the stages seperate it would have had enough delta V to go there and back... Possible even to minmus.)

Made a plane that goes suborbital with only jet engines

recreated Apollo 11

Made a rocket to carry my Saturn V rocket into orbit (WHILE it is thrusting down!)

And I have never once orbited correctly...

Apparently there is such thing as a "gravity turn..."

Normally I would just rocket until my apogee is above 70 km, wait until I am near the apogee, and then thrust prograde to orbit.

It worked, but turning the rocket 90 degrees was a little irritating. (Usually I needed vernier engines or a LOT of RCS for heavy rockets)

I don't know how I learned to orbit this way, but today marks the day I will do my first (correct) orbit...

But you learned from it. That's the best part :)

What works best for me I straight up until about 100 m/s, then gradually tilt right while always keeping within the prograde marker. You should be at about 45 degrees at 10000m, but it also depends on your rocket. At this point your ideal time to pe I about 50 sec. I know, sounds confusing and difficult but that's what YouTube is for :). 

I'm sure there are better and more efficient ways but for me this has worked best. I usually need around 3300dV to LKO, sometimes less. 

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On 7/10/2016 at 1:16 PM, legoclone09 said:

Am I the only one who is usually flat by 30km?

I think I OD'd on RSS and 64k a few months ago.

Some of my rockets have ridiculously low TWR upper stages.  If I'm not careful I end up circularizing into a 50km orbit.

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2 minutes ago, Corona688 said:

Some of my rockets have ridiculously low TWR upper stages.  If I'm not careful I end up circularizing into a 50km orbit.

Almost happened to me once.

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On 7/7/2016 at 6:54 PM, Trann said:

My usual ascent profile is similar to @michaelhester07 but differs in that I'll hold 30 degrees until Ap reaches 70k then I'll cut power and coast uphill until the time to Ap is under 20 seconds, at which point I burn at 90 degrees, keeping the time to Ap close to 10s while bringing my Pe up to circularize.

That's the way I used to do it too, until I downloaded some craft with tight dV budget and learn to fly it, after talking to Rune. You are wasting some 300-500 dV potential, which is quite a lot if you're into Micro SSTO's for example.

Try this. Do your normal launch, tip slightly and make sure by 10 km you're at 45 degrees. You can hold it there for a while, until your TIME to Apo is over 1 minute. Once there, hold prograde while at same time, reduce throttle so your time to Apo stays the same, aprox. 1 minute. Once you reached your target Apo height, tip to 90 degrees and continue burning horizontally, while maintaining the time to Apo constant. Obviously, once you hit 70 km mark, you can shut off engines and do next burn 5s to Apo.

What will happen is basically combine the circularize burn and take off burn INSIDE the athmosphere, so you take full advantage of Oberth effect, will have to expend very little dV to finish off circularization. Using this technique, you can take crafts into orbit that seemed impossible before. 3400 dV, it can be done with 3300 dV after a bit of practice, even less.

Edited by Zamolxes77

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On 7/7/2016 at 10:50 AM, Rocket In My Pocket said:

 

If it makes you feel any better I played for a year or two before I realized you could EVA, collect all your science data, then decouple the science parts so you didn't have to take them down through re-entry with you.

 

Well, if not for that off-handed tip, I'd be continuing to play years in ignorance.   Sheesh.  Many thanks.

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5 hours ago, Zamolxes77 said:

What will happen is basically combine the circularize burn and take off burn INSIDE the athmosphere, so you take full advantage of Oberth effect, will have to expend very little dV to finish off circularization. Using this technique, you can take crafts into orbit that seemed impossible before. 3400 dV, it can be done with 3300 dV after a bit of practice, even less.

How much energy are you losing by pushing your way through all the additional atmosphere? I've been trying various ascent profiles too and always wondered at the tradeoff between the benefits of having a smooth ascent curve against the benefits of getting out of thicker atmosphere.

Edited by tjt

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20 minutes ago, tjt said:

How much energy are you losing by pushing your way through all the additional atmosphere? I've been trying various ascent profiles too and always wondered at the tradeoff between the benefits of having a smooth ascent curve against the benefits of getting out of thicker atmosphere.

I believe they had the numbers earlier in this thread, and drag losses were 1-2 orders of magnitude smaller than gravity losses, so pretty trivial for rocket-shaped rockets.

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On 7/7/2016 at 8:24 AM, Snark said:

That's way too high (at least, for the sake of dV efficiency)-- if you're having flipping problems, that's a rocket design issue with aero stability.  It's readily addressed by tweaking your design; they'll fly themselves and won't ever flip.  Hard to give really specific advice without seeing a screenshot of the ship, but the general maxims are "heavy and pointy in the front, light and draggy on the back."

is there any good guidelines for reducing drag and being able to execute these sorts of turns? I often do a similar maneuver to these two you quoted and would really like to use a more efficient route, but suffer from severe drag forces that always want to tip my rocket over from even the most slightly out of center petrograde before the 20km mark where I often hit 45 until I near whatever my preferred apeostasis is. I knew this was a waste of delta-v but I have no idea how to stop drag from making my craft flip otherwise.
 

On 7/7/2016 at 8:37 AM, michaelhester07 said:

As for the rocket flipping:  First add Winglets to the bottom.  If that doesn't fix the flip do a fairing over the payload.  If both of that doesn't work, drag the payload into orbit behind a lift structure, making sure your thrust origin is ahead of the payload.  It will naturally fix itself this way (but could be hard to gravity turn).  This is especially needed if you launch biospheres from the civilian population mod.

The first 2 I have already tried a lot, the second I am less familiar with in terms of Kerbal rocket design. I might add this is something that happens to me with even very benign stuff like I last launched a hitchhiker with mk1 command + reaction wheel and 3 small comms satellites to setup an omni-LKO sat network.probably wasn't that heavy at all, but it just would not stop with causing drag and I will likely have to launch more satellites to setup the network to cover the other bodies in the SOI. With this 3rd option am I building a number of smaller lift payloads with no central engine or something around my vac stage payload? It just seems like a counter-intuitive ship design (usually the cart goes before the horse), but makes sense on considering I can see how the main problems I am having are probably from loss of drag on the back when I jettison spent fuel containers and boosters. How far forward does thrust need to be? Just ahead of the COG of the non-atmospheric payload?

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A really easy way to fix the aerodynamic stability is to use a two stack stage rocket. The mass of the upper stage will act to keep the CoM forward while the lower one drains, until you're clear of the major atmospheric effects and the upper stage attitude control (TVC, generally) can point you however you like.

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typically that works ok until I drop boosters then it flips same with when I go to drop depleted asparagus staging. I am thinking this is because of reduction of drag from the bottom portion but if I have to not use boosters or asparagus staging, I am definitely not saving on delta-V.

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1 hour ago, SpaceCommunism said:

 

is there any good guidelines for reducing drag and being able to execute these sorts of turns? I often do a similar maneuver to these two you quoted and would really like to use a more efficient route, but suffer from severe drag forces that always want to tip my rocket over from even the most slightly out of center petrograde before the 20km mark where I often hit 45 until I near whatever my preferred apeostasis is. I knew this was a waste of delta-v but I have no idea how to stop drag from making my craft flip otherwise.
 

The first 2 I have already tried a lot, the second I am less familiar with in terms of Kerbal rocket design. I might add this is something that happens to me with even very benign stuff like I last launched a hitchhiker with mk1 command + reaction wheel and 3 small comms satellites to setup an omni-LKO sat network.probably wasn't that heavy at all, but it just would not stop with causing drag and I will likely have to launch more satellites to setup the network to cover the other bodies in the SOI. With this 3rd option am I building a number of smaller lift payloads with no central engine or something around my vac stage payload? It just seems like a counter-intuitive ship design (usually the cart goes before the horse), but makes sense on considering I can see how the main problems I am having are probably from loss of drag on the back when I jettison spent fuel containers and boosters. How far forward does thrust need to be? Just ahead of the COG of the non-atmospheric payload?

The design I finally settled on for launching the large farm unit from civpop was a gantry that put the rocket bells just above the top of the farm sphere.   I had ended up welding it to reduce part count but it was able to fly without welding.   I'd imagine about 1/8th of the ship's length ahead of the "center of drag".  Basically the part that drags the most goes at the back.  The center of mass as you fly will eventually end up behind the center of thrust so that you maintain stability when the engines are fired up.

Think about how you would drag a class E asteroid into kerbin orbit.  It works the same way when launching the heavy non atmospheric payload.

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2 hours ago, tjt said:

How much energy are you losing by pushing your way through all the additional atmosphere?

 

2 hours ago, Terwin said:

I believe they had the numbers earlier in this thread, and drag losses were 1-2 orders of magnitude smaller than gravity losses, so pretty trivial for rocket-shaped rockets.

Well, there's this recent thread:

Apparently the user is on a realism mod or two, but not FAR in the initial post at least, so the dVs are a lot higher than stock, but there's some interesting discussion on the subject.

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@FyunchClick That thread's intro: "Based on an idea born in another thread "

The thread @Norcalplanner is referring to in the intro? It's this one! :D

Norcalplanner helpfully posted some experiments in this thread, and then expanded upon it in a separate thread.

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@SpaceCommunism:

If you're having a problem with your rockets flipping, you're in good company.  Lots and lots of people have run into that since 1.0 came out.  Just do a search on the word "flipping" in the Gameplay Questions forum and you'll see a lot of chatter.

It boils down to:  pointy on the front, draggy (i.e. fins) on the back, CoM near the front.  And the CoM needs to stay near the front as you stage and drain fuel.

There are many ways to "do it wrong"-- and the fix for any given rocket depends on just what exactly that particular rocket is doing wrong.  Therefore, giving advice (other than the very generic advice above) really needs a screenshot.  If you could post a screenshot of a rocket that you're having problems with, we can give you suggestions on how to fix it.

2 hours ago, SpaceCommunism said:

is there any good guidelines for reducing drag and being able to execute these sorts of turns? I often do a similar maneuver to these two you quoted and would really like to use a more efficient route, but suffer from severe drag forces that always want to tip my rocket over from even the most slightly out of center petrograde before the 20km mark where I often hit 45 until I near whatever my preferred apeostasis is.

The problem with flipping is not that you have too much drag.  The problem is that your drag is in the wrong place.  You could build the sleekest, most streamlined, lowest-drag ship in the history of ever... and it's still going to flip if its CoM is at the back of the rocket.

Making your rocket stable is not about reducing drag per se-- it's about arranging where your CoM is, relative to the aero forces (such as drag) on your rocket.  Again, screenshots please!  :)

 

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http://imgur.com/a/U7YZL

http://imgur.com/a/AyJNK

 

This would be a good example of the problem I had to work on this one for a long time the other night just to get it up into orbit so that it wouldn't flip. COM is obviously closer to the bottom around the engine for the no atmos stage. For reference those solids on the side are from interstellar and have gims (also set to 40% so they last till I clear atmos), the attached AV-R8 are scaled up to 200% and the booster are set in a separate group to trigger when I start to have difficulties with control. The central thruster is a t30 tweaked to 3.75 on an x200-8 tweaked the same and the tanks around it are 2 stage asparagus with regular t45s (just for the gim thrust) The 4 nacelles on the top are just for the orbital stage, they are fuel tanks setup in a 2 stage asparagus with no engines feeding to an x200-8 tank that has a single terrier scaled to 2.5.

Even though I was able to use this rocket to achieve the mission this is the best working model of all the ones I had that kept tipping over I could never do the gradual side shift you guys are talking about or even keep it going without flipping most of the time, Clearly the COM is on the bottom but always above the drag however as I drop the solids and the first liquid stage I have a massive shift that causes me to loose control and usually flip.

The reason why I am asking general tips is because this is a very typical design style for me so if you have advice it may be generally helpful.

Edited by SpaceCommunism

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