To Mech-Jeb or not to Mech-Jeb, that is the question...

[Vanamonde]

I'll tell you one thing that's making me reconsider my dislike for autopilots, and that is that it would be nice if my stupid ships would sit still while I'm EVA or in another ship for rendezvous. Right now I'm hardly doing any spatial EVAs because I'm not sure my guys could get back inside a ship that's wallowing around like it's having a bad dream, and when I did my first rendezvous in .16 yesterday, I couldn't keep the ships close together because of the risk of the spinning one smacking parts into the one I was flying. > Does Mechjeb keep one ship still while you're flying another ship? And I seem to recall reading that it takes up space so there's less room for crew?

Edited August 18, 2012 by Vanamonde

[Naiba]

In a game where failing is, arguably, a fair amount more fun than succeeding, (Or at least adds to the gratification of eventual success while still being a fun process) I don't know why anyone would want to use mechjeb before they've learnt to do what they're using mechjeb to do for themselves.

[Czman007]

I only use mechjeb for putting satellites in precise orbits or orbital rendevous. I think it is a great convience.

[spikeyhat09]

I agree with this post 100%, and have felt this way ever since learning of mechjeb. its like learning to drive an automatic before stick-shift.

[darkwolfpaw54]

well i use it to get to the mun and minus at least a few feet away from the pleant and i land the lander my self

[4 IN 1]

It is a mod, use it if you like, HTFU if you don't.

[Ascensiam]

In the beginning i didn't even know about ASAS, seriously, i stabilized craft with the controls all the way to orbit.

Then i learned about it, and i've found it to be just precisely that of a tolerable level of assistance. The ASAS is a massive automatic help, but i prefer doing as much as possible by hand.

So i have extremely few mods installed, and not Mechjeb, i want to continue sharpening my skill for the planet update.

[trekkie_]

I think mechjeb should be built into the game. when I first got the game, I manually traveled to and landed on everything I could, eventually. but now....it's more trouble than it's worth, especially since the controls aren't all that precise in a game where you tap directional keys. pretty much all things that go into orbit in the real world have an autopilot.

after you do it, and know you can if you wanted....the challenge isn't there anymore. mechjeb allows you to not waste hours on a simple mistake, and allows you to try out different ship designs and see if they have what it takes to be successful. with mechjebs auto throttle, you know that if a ship can do it using auto pilot, then there's plenty of room for error and fuel left over if you did it manually. anyone can strap some fuel tanks to a rocket and blast it off, but not everyone can create an elegant ship that combines form and function.

so for me the game has shifted to creating new cool ships rather than tediously navigating it manually. ask any astronaut whether they'd like to manually control the ship or use autopilot, and all of them will say auto pilot because manually piloting a real ship is tedious while having your life in your hands. in fact, it's virtually impossible for astronauts to manually pilot every aspect of a space craft in the real world.....even the apollo landing used computers. granted they still have to use inputs....but it's not like they had a joystick controlling the whole thing. even then, computers would be programmed in newer space craft to keep a pilot from doing specific maneuvers at specific speeds, etc. the gforces could rip a ship apart or damage it enough to kill everyone on board. so even when an astronaut is allowed to manually control the vessel, most of that control is limited to what the software will allow, while at the same time it's activating a dozen systems to do what it thinks the pilot wants it to do.

[Kosmo-not]

with mechjebs auto throttle, you know that if a ship can do it using auto pilot, then there's plenty of room for error and fuel left over if you did it manually.

What exactly do you mean by that? Mechjeb can outperform most KSP pilots.

[Zacho]

I use Mech-Jeb. Sure ive done landings and take offs by hand before, many times. But coming from orbiter, doing all that by hand gets old fast. (Try doing a real maned mars mission in orbiter, even with AP modes and ships made for the mission its hard.)

I play KSP for the sim parts, sure its fun to blow stuff up sometimes. But doing a full mission and coming home feels a lot better. And Mech-Jeb makes that easier. I find it funny that people call it cheating, this game is a sim at its heart. Using AP modes in a sim about space is not cheating. No manned craft did it all by hand, launch most of all.

[Mensa]

What exactly do you mean by that? Mechjeb can outperform most KSP pilots.

MechJeb uses way too much throttle most of the time. If someone makes the same flight manually they will have better fuel management.

[Kosmo-not]

MechJeb uses way too much throttle most of the time. If someone makes the same flight manually they will have better fuel management.

When does MechJeb use too much throttle? The only time this can be the case is during atmospheric ascent, but it performs just fine there.

MechJeb doesn't use too much throttle, unless you are talking about the fuel consumption bug.

[AncientAstronaut]

Mensa, without the bug, lower throttle does not save fuel. So what you just said makes no sense.

[KAO]

well personally, mechjeb is a must for planetary landing probes

[trekkie_]

Mensa, without the bug, lower throttle does not save fuel. So what you just said makes no sense.

I'd have to say that it does save fuel, without being affected by the bug. ascent eats most of the fuel, especially early ascent. once you're in space/orbit you don't have to worry about drag or heavy gravity.

the reason why it works well is because it's time vs thrust. you can go farther using less throttle as long as you're not losing speed, but of course you have to go at a decent speed to begin with so full thrust for a time in the beginning is obviously beneficial to gain momentum since this is when you are heaviest and more affected by drag. also the faster you are going once you reach orbit, the more power it takes to align into orbit.

it's not as simple as half throttle, half gas consumption, half as far. max throttle may produce more speed, but more speed/thrust is not always more efficient. the higher you get and the lighter you get from fuel consumption, the less thrust that is needed to maintain the same speed or speed increase rate, which can allow you to throttle back quite a bit. for example, if you're going 1000m/s at 50K meters and throttle back enough to keep that rate or that rate with slow growth (which might only need 1/10th the throttle), it will take you around 50 seconds or a little less to get to 100K meters. but if you keep it at full thrust, you might only end up with ~3000m/s by the time you reach orbit, which will get you there quicker (maybe 20 seconds quicker), but consume much more fuel. 1/10th throttle while only taking twice the time is obviously a beneficial trade off.

now you might not save 10 times the TOTAL fuel because most fuel is expended early launch (such as 50-20K meters and below), but you can end up with quite a bit more left over once you reach orbit than you would have otherwise. in many larger vessels, this can mean the difference between having no fuel once you reach orbit altitude, or only having enough fuel to align into orbit and go nowhere else. even a little throttling back can mean the difference between having just enough fuel left for getting into orbit or transferring to mun/minimus.

Edited August 18, 2012 by trekkie_

[r_rolo1]

Well, there is a part of the fuel and orbit management that MechJeb does not get very well: landings, both in atmospheric environments and in vacuum. Sure , it does a serviceable job, but the fact that it does not correct the horizontal velocity first and then dive to the suicide burn, that is the best way fuel wise, makes it waste fuel in ships that normally already don't have much of it by that time. It also does not handle the suicide burns very well in terms of timing too ( I normally end activating the autopilot manually instead of letting it figure the time to make the suicide burn, because it tends to start burning too early and too high, especially in landers that can deliver high Gs )

Anyway, as you can deduce from the above, I use mechJeb. Being myself a lousy pilot ( I have really bad eye-hand coordination ...a lot of kerbals died already because of that ) and especially enjoying the rocket scientist part of the game far more than the piloting one, it is only normal to use mechjeb, especially when doing flights with experimental rockets. And this in spite of being perfectly able to do all the orbital manoeuvres needed by myself ( if you can tolerate a 20-40% failure margin, that is ) ...

[ramses]

I'm with Vostok. Never used it never will!

When I started playing ksp it was seriously gut-wrenchingly heartbreaking:/

But in saying that, I refused to give in and with every failure I'd learn something new, pick up the pieces and try again. And I have to say, that first mun landing was a feeling I will never forget:) I truly believe I wouldn't have felt anything like that if I used mech-jeb.

But that's just me.

In the end it's up to the player and what they want out of the game.

I'm just glad more and more people are playing the game, which in turn helps the squad make it even better!

[Ziff]

I'd have to say that it does save fuel, without being affected by the bug. ascent eats most of the fuel, especially early ascent. once you're in space/orbit you don't have to worry about drag or heavy gravity.

the reason why it works well is because it's time vs thrust. you can go farther using less throttle as long as you're not losing speed, but of course you have to go at a decent speed to begin with so full thrust for a time in the beginning is obviously beneficial to gain momentum since this is when you are heaviest and more affected by drag.

The only time lower throttle saves fuel is once you hit Max-Q. At that point more thrust produces little speed increase because of atmospheric drag and is otherwise wasted. Rocket engines don't save fuel with lower throttle, once they are traveling faster than the exhaust speed of the engine they are at maximum efficiency and throttle amount has no affect on efficiency. The only thing that increases efficiency would be a higher Isp.

also the faster you are going once you reach orbit, the more power it takes to align into orbit.

Er, what? What do you mean by power? Once you reach orbit, you're uh, in orbit. There is no aligning left to do.

it's not as simple as half throttle, half gas consumption, half as far. max throttle may produce more speed, but more speed/thrust is not always more efficient. the higher you get and the lighter you get from fuel consumption, the less thrust that is needed to maintain the same speed or speed increase rate, which can allow you to throttle back quite a bit. for example, if you're going 1000m/s at 50K meters and throttle back enough to keep that rate or that rate with slow growth (which might only need 1/10th the throttle), it will take you around 50 seconds or a little less to get to 100K meters. but if you keep it at full thrust, you might only end up with ~3000m/s by the time you reach orbit, which will get you there quicker (maybe 20 seconds quicker), but consume much more fuel. 1/10th throttle while only taking twice the time is obviously a beneficial trade off.

now you might not save 10 times the TOTAL fuel because most fuel is expended early launch (such as 50-20K meters and below), but you can end up with quite a bit more left over once you reach orbit than you would have otherwise. in many larger vessels, this can mean the difference between having no fuel once you reach orbit altitude, or only having enough fuel to align into orbit and go nowhere else. even a little throttling back can mean the difference between having just enough fuel left for getting into orbit or transferring to mun/minimus.

This doesn't sound right at all. Rocketry and orbits are all about the speed you need to travel to fall correctly around the orbital body, this is why it's all about delta-v delta-v delta-v. If the orbit height you want to have takes a delta-v of 4500m/s to obtain, and I give you a rocket with an engine with a certain Isp and fuel quantity that gets you 4200m/s of delta-v, you can throttle however you want, you are not getting into orbit. It just doesn't work that way. You can't increase delta-v by lowering your throttle, if you are, what you are seeing is the fuel bug.

Back on topic , I love MechJeb. I love all the information it provides, it's just a plethora of wonderous streaming data that I can use in so many ways! I tend to use it a lot on new craft so I can monitor everything, but then I usually get rid of it once I have flown a craft repeatedly. Probably for me the best thing about it is instantly seeing my apoapsis and periapsis without having to check the map. That's what I use the most often. I rarely use the automated features except for simple testing purposes, because it can repeat almost the same maneuvers exactly.

Edited August 18, 2012 by Ziff

[karolus10]

Also atmospheric drag is going into account too - so keeping acceleration above some threshold don't get you much faster from the atmosphere (especially lower part), because you must fight with stronger drag and this meant you need more power for only keeping momentum .

Finding best coefficient between time to get into orbit and thrust energy produced by rocket was told "Goddard problem".

[CobraA1]

Well, I've done the manual mun and minimus landings (and return to kerbin) manually, so I figure I've already done the hard stuff so far.

For the most part, I use MechJeb for "what if?" scenarios and testing spacecraft.

In fact, I'm actually using it to plan a possible future mission to another planet - assuming that KSP will have a Mars-like planet soon. I've already built a ship that has made it to a Mars-like orbit and back. I like the fact that it automates launches and provides lots of useful info.

[flaillomanz]

My newest rocket design has a mandatory half-corkscrew after the first stage separates. Without MechJeb I would have scrapped the design; as it is, it's my highest performer yet, able to (barely) perform a sun-drop.

[TheDarkStar]

I never use MechJeb anymore. I used it for a short time, but I found it more fun to manually launch rockets. My best-preforming rocket explodes easily if launched the way MechJeb does it, and the same probably happens to others.

Edited August 18, 2012 by TheDarkStar

[CobraA1]

MY best-preforming rocket explodes easily if launched the way MechJeb does it, and the same probably happens to others.

Generally the same for my rockets - some of my top performers are not compatible with MechJeb - mostly because it rotates during the gravity turn, which tends to make the stages collide with each other when they separate.

That being said, it can be overcome - the "Mars" rocket which I've designed to get to other future planets is in fact MechJeb compatible, and it's certainly one of my top performers.

Edited August 18, 2012 by CobraA1

[trekkie_]

The only time lower throttle saves fuel is once you hit Max-Q. At that point more thrust produces little speed increase because of atmospheric drag and is otherwise wasted. Rocket engines don't save fuel with lower throttle, once they are traveling faster than the exhaust speed of the engine they are at maximum efficiency and throttle amount has no affect on efficiency. The only thing that increases efficiency would be a higher Isp.

Er, what? What do you mean by power? Once you reach orbit, you're uh, in orbit. There is no aligning left to do.

This doesn't sound right at all. Rocketry and orbits are all about the speed you need to travel to fall correctly around the orbital body, this is why it's all about delta-v delta-v delta-v. If the orbit height you want to have takes a delta-v of 4500m/s to obtain, and I give you a rocket with an engine with a certain Isp and fuel quantity that gets you 4200m/s of delta-v, you can throttle however you want, you are not getting into orbit. It just doesn't work that way. You can't increase delta-v by lowering your throttle, if you are, what you are seeing is the fuel bug.

Back on topic , I love MechJeb. I love all the information it provides, it's just a plethora of wonderous streaming data that I can use in so many ways! I tend to use it a lot on new craft so I can monitor everything, but then I usually get rid of it once I have flown a craft repeatedly. Probably for me the best thing about it is instantly seeing my apoapsis and periapsis without having to check the map. That's what I use the most often. I rarely use the automated features except for simple testing purposes, because it can repeat almost the same maneuvers exactly.

"while more thrust, fuel, etc. will be needed to transfer a larger communication satellite from low Earth orbit to geosynchronous orbit, the delta-v required is the same. "

see while delta-v is the same, there is obviously lee weigh in the amount of thrust and fuel required. which means you can most certainly save on fuel by throttling, especially when you weigh less than initial takeoff and other things like drag of the atmosphere reduces the higher you go.

delta-v is the speed you need to obtain to do things like gain orbit, it is not dependent on the ships mass or fuel mass nor amount used...how efficiently you gain that speed means you can vary the amount of fuel used.

you can't call it a fuel bug when it's about throttling efficiency. I think you're on a completely different page here. I'm talking about the entire lift off from on the ground to orbit altitude, to going into orbit. you can save fuel by throttling during ascent. the delta-v may be the same for a maneuver, but the amount of fuel and throttle required can vary based on time and distance, with quite a bit in savings being possible. in essence, going 2000m/s by the time you reach your target means more fuel used than going 1000m/s instead. we can afford to lose forward momentum for a lower throttle netting us fuel savings.

Edited August 18, 2012 by trekkie_

[Bluejayek]

kerb, the point others are making is twofold.

1) There IS a fuel bug in the current version. Aparently the thrust produced scales linearly with throttle, while the fuel used scales quadratically. So essentially if I am at 1/2 throttle I get 1/2 the thrust for 1/4 the fuel, or at least this is how I understand this.

2) "Targets" in orbit is almost always not a specific location, but a specific location/speed. It does not good to get up to the position of orbit if you are going 1000m/s too slow, and therefore it is not a fuel savings to be going slower at this point.

That being said, I entirely agree with you that even in the absence of a fuel bug sensible throttling in atmosphere can save a lot of fuel. I go by the rule of thumb that you want to cruise at about 100m/s until you are out of the lower layer of atmosphere (10km or so).

As per mechjeb, I don't use it. I prefer doing things manually, although I am considering installing it just for the extra orbital information it provides, and simply not using its autopilot functions.