Rocket to the Mun

[locustgate]

Ok...I have no clue what I'm doing wrong, all I'm able to do is get the...to stages up to 4k dv but anytime I try to get it over, no matter what the fuel/rocket types, it then starts to decline. I'm able to get to the moon and land but not get back from it as I use the return fuel to land, used infinite fuel to test it out and the lander is able to return to kerbin even after using fuel to land. So the main problem I'm having is wasting fuel to get to orbit and to Mun. SO I have 2 theories either I'm making the transit stages to big/ not big enough or my lander is to big.

[TheDarkStar]

If the math shows you have a good enough rocket, you just need to practice your piloting skills.

[locustgate]

Not really doing the math using MJeb.

[Specialist290]

Yeah, that lander definitely looks Mun-capable, assuming you can get there first. If I might make a few suggestions:

1. Can you upload a few screenshots with the launch vehicle attached? That might help us get a better picture of where you might be going wrong with the engineering. It might be as simple as just adding a "kick stage" between the main launcher and the lander.

2. What does your Mun approach look like? Are you circularizing in a low orbit before you begin the actual landing, or are you basically shooting straight at the Mun and trying to kill your velocity before you hit it going too quickly? The first way is much less delta-v intensive, essentially because you're letting gravity do part of your work for you instead of having to try to fight it the whole way down like in the second way.

EDIT: And a third one: What does your typical launch from Kerbin look like? How high up do you get before you start your "gravity turn" to get your horizontal velocity going? About how high up do you usually circularize your orbit? (It might seem against standard logic, but lower is actually better here in the long run.)

Edited September 8, 2013 by Specialist290

[locustgate]

Note 3 Is meant to be intercept rocket.

2 Circularize then rapid decent.

3: Orbit 75k-100k.

[Specialist290]

It really looks like that rocket should be able to make it as-is, although I do already see a few points where you might be able to "tweak" it to make it perform a little better. It might just be that your piloting technique needs a little work. I'm working on rebuilding a copy from what I can see right now to test a few things out, but in the mean time, a few more questions:

Can you go into a little more detail about what your launch from Kerbin as a whole looks like? About how high up do you start tilting your rocket after liftoff, and by how much?

EDIT: Another thing I'm noticing: It apparently doesn't have any sort of flight stabilization other than the reaction wheels in the pod. I'd advise adding some fins to the base of the rocket for atmospheric control, plus an Advanced SAS to the top of the launcher for extra reaction wheel torque. That might give it a little more control, which should help with efficient maneuvering.

Edited September 8, 2013 by Specialist290

[Tiron]

That rocket should definitely be able to make it to the Mun, as I'm fairly certain the stock Kerbal-X is perfectly capable of managing it.

[99TheCreator]

Fuel lines. You need to put fuel lines from your outer stacks into your center stack. Drastically increases the range your rocket can travel.

[SRV Ron]

You should be able to get into low, 10k mun orbit with fuel left in the boost stage. Use it to start the landing phase and for slowing down all horizontal speed prior to landing. Then jettisoned it and do the final phase of landing on the descent stage. You should have fuel left in that for the accent, stage when it is gone, get into Mun orbit. Finally, plan your burn to Kerbal to hit a retrograde escape that results in an elliptical orbit with a parapsis of 15k. That is the most efficient way to return to Kerbal for an aerobraking re entry and safe return.

If your launch vehicle stage 3, reading from the event markers on the right of the posted pic, is not giving you enough fuel for the transfer from Kerban to close orbit Mun and have enough left for most of the landing phase, add two more strap on boosters to the first stage for a total of six and asparagus stage them.

The one recommended rocket for beginners, when flown correctly, had sufficient fuel left in its transfer stage to use for the landing phase leaving plenty of fuel in the descent, in your case, the four outboard engines, for landing with some to use for launch to start your return.

Edited September 8, 2013 by SRV Ron

[Specialist290]

Prelimiary flight testing notes: Holy cow, does this baby have a lot of thrust. Forget what I said about fins and reaction wheels; you don't need 'em. If anything, I'd say you're probably trying to go too fast too quickly with this thing, and drag from excess air resistance is eating into a good-sized chunk of your delta-v budget.

EDIT: To clarify, for about the first 10,000 meters or so, you should try to keep your ascent velocity in the 150-200 m/s range; otherwise, you're going to be losing quite a bit of delta-v because the atmosphere is going to try to push your rocket back down. After that, start tilting over until you're nearly flat (~5-10 degrees off the horizon on the navball), then push the throttle to the floor once you get above 20,000 meters until you've got an apoapsis of 80 km or so. Then cut waay back on the thrust and try to get as much horizontal velocity built up gradually as you can. You should be able to circularize using about a quarter or so of your Munar injection stage's fuel, leaving plenty for the injection burn itself.

From there, should be pretty smooth sailing.

Edited September 8, 2013 by Specialist290

[SRV Ron]

Can't tell if he onion stage this or not. If he did, or better yet asparagus stage the design, it is not over powered but would fly more efficient getting into orbit without having to use or using very little fuel from the transfer stage.

[locustgate]

Well I go Full throttle until I hit 100 m/s then cut to the minimum a I can. When I hit 9.5k m I begin turning to 90 45 when the AP gets to 75k m I circle my orbit till both ap and..Pa?. reach 75k m, then burn at a 90 angle from the moon then circulate asap then descend.

P.S. The engines are

Lv 909 x4

Poodle

Skipper

Mainsail x 5

[Tiron]

...then burn at a 90 angle from the moon...

Errrr....no. You want to burn Prograde shortly after Munrise (assuming you're on a 90 degree inclination, Eastward orbit.)

Edited September 8, 2013 by Tiron

[Specialist290]

Errrr....no. You want to burn Prograde shortly after Moonrise (assuming you're on a 90 degree inclination, Eastward orbit.)

I think that's what he means -- he burns when his ship is at 90 degrees in its orbit from where the Mun is now, which will put him where the Mun should be.

I've updated my second post in the thread based on my own experience with the rocket, but just for the sake of visibility, I'll quote it here, too:

for about the first 10,000 meters or so, you should try to keep your ascent velocity in the 150-200 m/s range; otherwise, you're going to be losing quite a bit of delta-v because the atmosphere is going to try to push your rocket back down. After that, start gradually tilting over until you're nearly flat (~5-10 degrees off the horizon on the navball), then push the throttle to the floor once you get above 20,000 meters until you've got an apoapsis of 80 km or so. Then cut waay back on the thrust and try to get as much horizontal velocity built up gradually as you can. You should be able to circularize using about a quarter or so of your Munar injection stage's fuel, leaving plenty for the injection burn itself.

I'm still en route to the Mun as we speak, but I know the injection stage and the lander should definitely make it to the Mun and back from what I've already seen.

Edited September 8, 2013 by Specialist290

[Thomas Cook]

Stage 4 and 3 give you around 4600 delta-v in atmosphere. In a perfect ascend to an orbit around Kerbin that should *barely* be enough, but I don't see much elbow room for margin errors. If you change stage 4 in an asparagus stage, I bet you could pump extra delta-v out of your rockets.

And another hint I'm slightly sure of: removing stage three and add some extra power and fuel to stage 2 would make your ship a bit lighter. Then the lifter also has extra delta-v. After that the trip to the mun should be doable with the lander alone.

Dropping the amount of fuel and using skippers instead of mainsails could also do the trick. Use a mainsail in the middle and skippers on the side. Mainsails are awesome in thrust, but they drink like templars.

But as Specialist290 said: how does your launch look like from Kerbin. With those thin margins I can imagine you get in Kerbin orbit almost, just not yet.

[Specialist290]

Stage 4 and 3 give you around 4600 delta-v in atmosphere. In a perfect ascend to an orbit around Kerbin that should *barely* be enough, but I don't see much elbow room for margin errors. If you change stage 4 in an asparagus stage, I bet you could pump extra delta-v out of your rockets.

Those numbers are deceptive, though; atmo delta-v assumes an atmosphere of 1 atm of pressure, which by the time you get high enough to separate the stages, it most certainly isn't. The atmosphere scales logarithmically, mind.

As a matter of fact, here I am with the replica I just built, just outside the Mun's SoI:

Edited September 8, 2013 by Specialist290

[Thomas Cook]

Those numbers are deceptive, though; atmo delta-v assumes an atmosphere of 1 atm of pressure, which by the time you get high enough to separate the stages, it most certainly isn't. The atmosphere scales logarithmically, mind.

As a matter of fact, here I am with the replica I just built, just outside the Mun's SoI:

It's true that the atmosphere gets thinner while you ascend, which should make your engines more efficient. Did you make that ascend easily though? I mean with a decent amount of delta-v left?

[Specialist290]

I circularized at ~90 km and still had about three-quarters of the fuel in Stage 3 left in my tank, which was plenty to do a Munar insertion with as well.

By the math, your engines should reach about 90% of their atmospheric efficiency once you've cleared about 11,000 - 12,000 meters altitude. I'd have to do a little bit of testing to be absolutely certain, of course.

EDIT: Just did a brief test and recorded my results:

Javascript is disabled. View full album

Edited September 8, 2013 by Specialist290

[locustgate]

I tried switching the 4 outside engines with skippers...well....I didn't get off the launch pad.

[Specialist290]

I tried switching the 4 outside engines with skippers...well....I didn't get off the launch pad.

As I've noted before, your original launcher should have enough power and fuel to reach orbit. You're probably not being aggressive enough with your gravity turn. Have you tried launching it using the procedure I've mentioned yet?

[Rainbow-Dashie]

I'm still a bit noobish at this game, so my advice may not be the best... but might as well try.

You probally dont need the other 4 engines on that lander, The poodle should be more then enough for a lander that size, I've been using something similar to yours, even a bit bigger, and a single poodle is more then enough to slow it down, from 25,000 meters up( and thats to soon ). ( though I get into a 50,000m orbit first )

My lander had an extra fuel tank (360 unit silver one i think) and landed with about 340 fuel. (not sure if that can get back to Kerbin, lost the lander before I could try.)

[locustgate]

I haven't had any luck in doing it.

[Dortmunder]

You're just trying to get it to the Mun and back?

If you send me the file I can stream for a trip there and back, maybe sort out what the problem is.

[Dooz]

I am sure based on the screen shot it should get you to the mun i dont trust mechjeb for landings

[Slugy]

As you already have mechjeb let it do the ascent and pay attention to the speed it goes as it ascends.

Letting it do a landing from a circular orbit will also give you a *reasonable* descent to watch.