need an addon to calculate

[SimonSyz]

as titel tells. I need an addon to do the math, tell me weight and deltaV of my constructions. By now I only do it be try and error

[baseballlegend09]

MechJeb has those tools and there's one called Kerbal Engineer that does that as well.

[hobbsyoyo]

You are looking for Kerbal Engineer. It's pretty great and does exactly what you are looking for. Recently found it myself, before then I was calculating everything in spreadsheets.

[Ralathon]

I can vouch for Kerbal Engineer as well. Can't live without it, modded all my pods so they have the build engineer so I know how much dV the monstrosity I'm building has.

[fatfluffycat]

I like the look of MechJeb information screens, they look better.

[MalfunctionM1Ke]

I can vouch for Kerbal Engineer as well. Can't live without it, modded all my pods so they have the build engineer so I know how much dV the monstrosity I'm building has.

I also prefer Kerbal Engineer before Mechjeb. Allthough, Mechjeb teached me how to get into Orbit and how to dock, but I dont need its automation features anymore, so I switched to KE.

[Ruedii]

Kerbal Engineer or MechJeb are your best solutions for calculations.

Mechjeb's interface is nicer, and it has more features, but some players think it has too many features and can take the fun out of the game. You can always turn off the visibility of the features with the advanced settings. (For instance you can remove the execute maneuver buttons from the maneuver planner, and remove the autopilot enable button from the ascent guidance panel.)

[Oddible]

Kerbal Engineer has a more sophisticated interface for exactly what you're looking for than MechJeb.

MechJeb is an awesome addon with an absurd number of features. I primarily use it for ideas about maneuver nodes (it will create your nodes for you), and lately for turning Prograde / Retrograde (save my wrists from repetitive stress injuries), but it can literally do everything for you from take off to intercept to landing - which is why many people criticize it - almost like not playing the game at all. Don't use it as a crutch and it is still a great addon.

I slap both on all my ships.

[Kerbart]

Mechjeb has my preference as it's easier to put out of sight when you don't need it (unless I'm missing something monumental with Engineer)

[hobbsyoyo]

The one issue I have with Kerbal Engineer is that if you place your engines at the top of a stack and drain the tanks at the bottom of the stack and ditch them, working your way up, it won't have a clue of how to calculate that deltaV and will only tell you the deltaV of the top tank with the engines on it. The work around is to attach all of the tanks without decouplers, check the deltaV and then add your decouplers and fuel lines. Your deltaV will be higher than what you were first told since you will be dumping empty tanks - but not a lot higher in most cases.

Edit: No Kerbart, Kerbal Engineer's interface does tend to get in the way - particularly on a smallish old-style CRT monitor like the one I use.

[SimonSyz]

Thanks I'll try both

[Kromey]

Last time I considered adding KE to my game (just after 0.19 was released I think), it hadn't been updated for a while and many were saying it wasn't working anymore. You guys who love it, I'm assuming you're using it in current version without issue? Is it in the tech tree for Career mode, or would I have to hack it in if I wanted to install it now? (I do want it, much more than MJ (no disrespect to those who use MJ, I just wouldn't be able to resist the autopilot features, and that's not how I want to play the game), but what's the point if it doesn't work?)

The one issue I have with Kerbal Engineer is that if you place your engines at the top of a stack and drain the tanks at the bottom of the stack and ditch them, working your way up, it won't have a clue of how to calculate that deltaV and will only tell you the deltaV of the top tank with the engines on it. The work around is to attach all of the tanks without decouplers, check the deltaV and then add your decouplers and fuel lines. Your deltaV will be higher than what you were first told since you will be dumping empty tanks - but not a lot higher in most cases.

Edit: No Kerbart, Kerbal Engineer's interface does tend to get in the way - particularly on a smallish old-style CRT monitor like the one I use.

Do you have any pics of a design like this? Not to hijack the thread, I've just always thought that dumping tanks rather than tanks+engines would be a great way to save on weight (and, eventually, cash) and to more efficiently stage, but so far my attempts at this have used radially-mounted tanks only; I've wanted to try this with engines at the top dumping tanks from the bottom, but haven't been able to come up with an effective design for it yet...

[lewisd]

One thing Engineer has that I don't think MechJeb has is the ability to tell you your thrust-to-weight ratio for various planets and moons. I use this a lot for making sure my Mun/Duna return vehicles have enough thrust to actually lift off.

[Oddible]

One thing Engineer has that I don't think MechJeb has is the ability to tell you your thrust-to-weight ratio for various planets and moons. I use this a lot for making sure my Mun/Duna return vehicles have enough thrust to actually lift off.

And in atmo vs vacuum. So you can see how efficient those nuke engines are!

Yeah I wish the Engineer UI had a minimize button that could collapse it to a small icon (like MechJeb or Kerbal Alarm Clock).

Never seen the problem of KE failing to correctly calculate - I can't even imagine the rocket you're constructing that goes from top to bottom!? And adding everything without staging wouldn't show you correct dV anyway as one of the primary features of staging is dumping your extra weight during liftoff.

I DO believe that Engineer has been updated to work with R&D. Again, once you add it you have to go to the first node in your tech tree and click it on the right to turn it on. Either way you can find the fix in the MechJeb thread - it is adding 2 lines to the part file.

[lewisd]

And in atmo vs vacuum. So you can see how efficient those nuke engines are!

Yeah I wish the Engineer UI had a minimize button that could collapse it to a small icon (like MechJeb or Kerbal Alarm Clock).

Never seen the problem of KE failing to correctly calculate - I can't even imagine the rocket you're constructing that goes from top to bottom!? And adding everything without staging wouldn't show you correct dV anyway as one of the primary features of staging is dumping your extra weight during liftoff.

I DO believe that Engineer has been updated to work with R&D. Again, once you add it you have to go to the first node in your tech tree and click it on the right to turn it on. Either way you can find the fix in the MechJeb thread - it is adding 2 lines to the part file.

With Engineer, if you're only using the build engineer, the "compact" button does make it quite a bit smaller, and then you can stick it down at the bottom of the screen so you can only see the title bar, and just drag it up when you need to see the values. That's how I minimize the space it uses.

I can confirm that Engineer has been updated for R&D. If you add it before you start a game, you'll have the parts right away. Otherwise, you just have to go into R&D and unlock (for free) the parts.

[hobbsyoyo]

I haven't tried Kerbal Engineering in career mode but it works like a champ in sandbox mode.

I just got out of Orbital Dynamics class and I'm still on campus so I don't have pictures, but I'll try and add some later. By the way, as a new user, are there any restrictions on posting pictures? Also, I'll have to sign up for imgur or some other image hosting site because we can't upload pictures directly, right? (I've been lurking for a long time and I think someone mentioned this once)

Anywho, here's how my tank dropping design works:

This design is for an interplanetary transfer stage with very low T/W (for reference).

I have the payload at the top of the stack. This is the item that I want to push out into deep space. In my case, it is a 60ton reusable lander for use at Laythe and it launches with the transfer stage (I'm into big MEGA launchers - my transfer stage doesn't get itself into orbit with the payload, it is placed there by a massive rocket and then goes on to Laythe with the payload attached already as they launched together). Docking with your payload in orbit (so you don't have to have a massive rocket to launch them together) will work as well so long as you place the clampotron at the top of your transfer stage (you don't want your payload docked at the bottom of this stack where it will be dumped mid-flight).

The transfer stage itself has 3 orange fuel tanks, 8 NERVAs and support gear. I will start at the top tank. The top tank has a decoupler on it to seperate from the payload and a remote control unit under that because I want to be able to use this stage (which is the final stage in the stack) as a communications hub when it arrives at Laythe and dumps off it's cargo. No need to waste the infrastructure of a usable (if empty) tank if you've bothered to take it all the way there! I also attached solar panels and a battery, as well as 2 large RCS tanks and some RCS thruster units to this tank to provide attitude control and to keep it 'alive' after the lander has seperated and taken it's power and RCS systems with it. Towards the bottom of this tank, I place 8 cubic octogonal struts with radial symmetry onto the side. Then I take 8 more cubic struts and place them over the other struts but making sure that they are facing 'down' so that things can be attached to the bottom. Then, on these 'downward' facing cubic struts, I place 8 NERVA engines with symmetry. They will overlap a bit and are a bit tricky to attach, but they will stick on their eventually. You do NOT need to turn on part clipping to do this even though they overlap a smidge.

On the bottom of this tank, I place a single clampotron docking port. This is so that on the occassion that I have a really efficient burn and have some fuel left over, I can dock later craft back to this tank in Laythe orbit and get at that sweet, sweet rocketsauce. Because I am placing a payload and decoupler on top so that I can launch the payload with the transfer stage, you can NOT place a clampotron on the top. The problem is that when you decouple this tank from the payload, the decoupler will stay attache to it, blocking the clampotron. So you have to put the clampotron on the bottom if you want to ever dock with this thing after seperation. You probably won't care about docking with an nearly empty tank, I do it as a Just-In-Case measure. I *think* there are decouplers that will detach from both parts that are being seperated but I'm not sure. Anywho, under the clampotron, I attach a large decoupler, then strut that decoupler to the tank so it is firmly attached. Then, under this decoupler, I attach a second orange fuel tank. On this tank, I place a single cubic octogonal sturt to the side near the top. Then on the tank above it, I also place a cubic octogonal strut in line with the one on the other tank, attaching them as close close together as practical. Then I run a fuel line from the bottom octogonal strut to the top one. This will allow the bottom tank to feed the top one so that when it is empty, I can jetison it with the decoupler.

Lastly, I repeat the proceedure by placing a decoupler on the second tank (no need for a clampotron, this tank will be jetisoned mid-route and will be empty) and then attach a 3rd orange fuel tank to that. I place cubic octogonal struts on the bottom of the 2nd tank and the top of the 3rd tank and then connect them with a fuel line going from the 3rd tank to the 2nd one.

Now you have to make sure you get the staging right: Your 8 NERVA's, being in the top tank, will automatically be set up to not activate until the other tanks are jetisoned. Move them down the staging list so that they fire when the entire interplanetary cruise stage seperates from your booster. DO NOT place any of the decouplers in the same stage with them. Now, when you pop off of your launch vehicle, the NERVA's will be pulling your entire cruise stage tractor-style. Place your 3rd tank decoupler on the stage above the NERVA's and your 2nd tank decoupler on the stage above that. This way, when your bottom tank empties, you can hit space bar and dump it. Doing this will not do anything to your NERVAs - they will keep firing as they are not attached to the stages being dumped (remember they are on the very first tank in the stack) and they don't have any decouplers of their own. Then, when your second tank is empty, hit space bar again and it too will be dumped. This set-up can take a 50-60ton payload all the way to Laythe with good piloting without ever touching the fuel load of your payload. You should even have some fuel left over - though you have to aerobrake at Laythe to get captured into orbit as you will not have enough fuel to do a powered orbital capture.

Notes:

The fuel lines will not automatically drain the bottom tanks for some reason. You have to alt+right click on the tanks and manually drain the fuel out as you go. If you are burning and you begin a fuel transfer, then the fuel will continue to be drained out of the bottom tank until you either close the fuel management window or the tank empties.

The NERVAs will provide 0 attitude control until either the 3rd or 2nd tank is dropped (I'm not sure why to be honest but I think it is because the vectored exhaust is hitting the fuel tanks below the engine and being deflected). You will thus have to use RCS fuel to steer until those tanks are out of the way and then the NERVAs will provide effective thrust vectoring.

The NERVAs will not overheat at full throttle. I think the tanks they are attached to absorb some heat or something. In any case, I observed that while the 'overheat' warning came on, it stopped climbing about a fifth of the way to maximum and held steady even through a 20 minute burn. Go figure.

The advantages of this system:

*You get to take full advantage of staging without having to haul around engines for each stage. In effect, this is kind of a pancake/asparagus staging hybrid as you are pulling fuel from tanks that you then drop to cut down on deadweight while not having to carry engines for each stage as you do in both asparagus and pancake staging.

*It is much easier to integrate an in-line staging system like this with a launch vehicle than it is to integrate a wide, radially-attached asparagus stage. As this is intended for an interplanetary cruise stage and is itself a payload on a launcher instead of a launcher in it's own right, it needs to be 'fit' within a launch vehicle - which is hard to do when you have lots of radial tanks hanging off the side.

*More efficient that standard asparagus staging - this allows you to drop off one tank at a time while still transfering fuel to later stages instead of having to drop off pairs as is the case with asparagus staging. This is more efficient as you drop deadweight sooner than you would with asparagus staging. You also only have to have one set of engines to power all the stages instead of seperate engines for each stage as is the typical set up for asparagus staging.

*You can avoid the problem of being top-heavy that you might otherwise have with attached radial stages. Your center of mass will be roughly in the center of the stack rather than up at the top (or at the bottom if you radially attach there).

*Easier to ditch RCS thrusters when you don't need them - you can see where your center of mass is for each stage as you build it and place RCS thrusters accordingly. Then, as each stage drops, any RCS thrusters attached to it get dumped as well and since you are now much lighter and compact, you don't need them anymore.

Disadvantages:

*The lack of powered steering from the engine gimbals is definitely a headache and you need lots of RCS gas to overcome this.

*A long, skinny rocket can be hard to turn without lots of RCS gas and thrusters. Consider adding in-line reaction wheels.

*You have to manually drain lower tanks in flight. I have no idea why the fuel lines don't work the way they are supposed to in this setup. The engines will pull fuel out of the tank they are attached too and not the lower ones until you manually drain them to fill the top tank. Maybe if you connect a fuel line from the second tank to each engine (instead of attaching a single fuel line to the top tank) it will work. I haven't tried this, so I don't know. However, even if you do do this you will now have the added mass of 7 additional cubic struts and fuel lines. It's not much, but every bit counts.

*Kerbal Engineer definitely cannot correctly calculate your deltaV with this setup. However, I suspsect this is because the fuel lines will not automatically drain the tanks rather than a problem with KE itself. Like I said, to get around this, build the stack first without decouplers and fuel lines and stick the engines at the bottom. KE will now tell you how much deltaV this unoptimized stack will get. Now go and add all of your decouplers and fuel lines and just keep in mind that your total deltaV will be somewhat higher than what KE told you before.

Things to investigate:

*I did not have any 'reverse steering control' issues with this rocket. I've heard that when you attach engines to the top of a rocket instead of the top, that the control inputs will be reversed so long as the Center of Mass is below the engines. I didn't have this issue - in fact, I had no steering capability at all from the engines because they were blocked by lower stages (they are very close to the tanks, nearly clipping). However, the RCS system worked fine and didn't suffer from reverse steering. By the time the 2nd tank was dropped, the blockage of the engines was gone and now the CoM had shifted above the engines so I never had reverse control issues but I can't prove these were the reasons why I didn't have reverse-steering problems.

*This design *should* work with big launch vehicles and not just interplanetary stages, though you'll have to use much more powerful engines. It is worth investigating in any case. You may even be able to crossfeed multiple booster stages somehow for even more effiiciency though I haven't tried it.

Edited October 23, 2013 by hobbsyoyo

[hobbsyoyo]

With Engineer, if you're only using the build engineer, the "compact" button does make it quite a bit smaller, and then you can stick it down at the bottom of the screen so you can only see the title bar, and just drag it up when you need to see the values. That's how I minimize the space it uses.

I can confirm that Engineer has been updated for R&D. If you add it before you start a game, you'll have the parts right away. Otherwise, you just have to go into R&D and unlock (for free) the parts.

The compact buttong? I haven't seen that (in the VAB at least), though I know if I click on the first button on the top right, it will collapse the menu down. However, it's still a long skinny bar and since I use a smallish CRT, every inch of real estate on screen is precious. I think you can collapse the whole thing flight as well but I can't remember.

[lewisd]

The compact buttong? I haven't seen that (in the VAB at least), though I know if I click on the first button on the top right, it will collapse the menu down. However, it's still a long skinny bar and since I use a smallish CRT, every inch of real estate on screen is precious. I think you can collapse the whole thing flight as well but I can't remember.

Do you have the "Compact" button that's in this screenshot?

It makes it look like this:

I drag that to the bottom of the screen then, so that only the title bar is showing.

[hobbsyoyo]

LOL I probably do but I have never noticed. Thanks and I hope that massive lolwtf post helped explain my staging method.

[wilt57]

I like MechJeb's interface better, but I like KER's better when in the VAB, if only for the ability to calculate TWR in relation to the body you are gonna visit. It's amazing how little an engine one needs on places like Minmus.

[tavert]

MechJeb's fuel flow simulation is a bit more sophisticated when it comes to SRB's and mixing SRB's with liquid engines. The TWR on other planets/moons is pretty simple to scale, atmospheric dV on Duna/Laythe slightly less so.

Otherwise, it's mostly a matter of personal style preference. Or inability to resist clicking the automation buttons in MJ...

[Eric S]

I think you can collapse the whole thing flight as well but I can't remember.

In flight, you can right click the part providing the KER ability (the Kerbal Flight Engineer part or modded capsule) and toggle the KER interface.

I drag that to the bottom of the screen then, so that only the title bar is showing.

Actually, if you turn off the other displays (usually main display, reference bodies if you have it open) and then compact it, you get a window that's just barely larger than the "Compact" button.

[Kerba Fett]

I've been using MechJeb for quite a while so would give it my vote. One of the things I like about it is that you can make your own custom windows to display whatever you need. I made one for docking that shows closest approach distance and velocity, current distance and approach rate and RCS delta V.

I also find the orbit info window to be more than I normally need so I made another with just AP, PE, and time till I reach each.

You can even make a super window that has functions you use from other mechjeb windows. It's a bit limited in it's input options, but you can get a lot of needed info on just a couple of windows if you get rid of all the less used stuff.