Kerbals in Spaaaaace!

[Eldan]

Man that's awesome. I love how every explosion lights up the entire night half of the planet.

[Cikomyr]

It's pretty cool. But is he using a maneuver-maker?

[Mando Knight]

Yup, often it's best to stay small.

As your payload weight goes up, the required fuel also increases. As the required fuel increases, so does the structural mass. Since the structure has weight, you have to factor in that mass increase to your fuel budget...

*Which, while nice, really isn't as awesome as much of the community seems to think. It's better than pancake staging but not by a huge amount. Once aerodynamics become more realistic, it'll be even less of a difference, and if anything pancake staging will likely become better. I've started to shy away from it even now because it leaves a lot of mess around and too often ejecting the stages causes explosions.

There's a reason vertically stacked stages are more common than asparagus stages in real rockets, after all... (also, such stages are much simpler to produce)

[Eldan]

Well, I just successfully smashed my first lander into the mun.

Because I can't manage to get enough fuel on it. I ran out of fuel, including everything for the return trip, just to get into a descending moon orbit. I keep packing more rockets on the thing and just burning up everything just to get into orbit. Oh, well, back to planning. It's farther than I ever got. 90% of my landers can't get out of Kerbal orbit.

[nhbdy]

Well, I just successfully smashed my first lander into the mun.

Because I can't manage to get enough fuel on it. I ran out of fuel, including everything for the return trip, just to get into a descending moon orbit. I keep packing more rockets on the thing and just burning up everything just to get into orbit. Oh, well, back to planning. It's farther than I ever got. 90% of my landers can't get out of Kerbal orbit.

are you perchance just building your landers too big? because most of the people I see struggling are building landers far bigger than needed, for scale, I can make a mun landing and return mission using only demo parts, you really don't need much, it's all in efficiency.

[Mando Knight]

The Apollo Lunar Modules were quite small themselves... the whole thing was just under 14.7 metric tons, and two thirds of that were the descent stage. The CSM that ferried it into place was only about twice that.

That's another trick you can try: use a CSM to tow your lander into orbit.

[Trekkin]

What does your ascent profile look like, Eldan?

Also, where in the trip are you staging and how are you planning to intersect the Mun's sphere of influence?

It sounds to me like you're starting the gravity turn too late or with too low a thrust-to-weight ratio.

[Eldan]

I found it rather easy to get into a Mun-orbit once I got into Kerbal orbit. That part was easy. In fact, I find that generally, I don't have much of a problem understanding how I have to change orbits.

The problem was getting up there. My moon vehicle is really quite basic. The smallest capsule, four small side engines, one of the smallest fuel tanks, four lander legs. It should be enough to land on the Mun and then get back to Kerbal.

But, well.
It seems to need giant amounts of fuel to get anything into orbit. I started with four small-sized engines then started scaling up from there to see what I'd need to get the lander into a good orbit and then on a Mun trajectory. Now I'm building with three exponentially growing stages, the lowest of which is four of hte giant orange tanks with Mainsail engines and 16 of the largest boosters. And I still barely get to the Mun before running out of fuel.

[AgentPaper]

You need ~8000 delta-V to go to the moon and back.

If you're having trouble, you might want to look at an existing design for inspiration. This guide for example provides you with the details of a ship can can do it, plus step by step instructions for how to do all the maneuvers.

If you don't want to do a step by step guide, I would suggest posting screenshots here of your designs so that we can give more accurate advice. Use F1 to take screenshots.

[Trekkin]

Spoiler

Show

Here. I flew it to the Mun and back manually; MechJeb is just there to show the delta-v. Getting into orbit eats into stage 3's fuel; by that point you have around 1000 m/s to crash into the Mun, and another ~2900 to land, take off, and crash back into Kerbin. The whole thing is overbuilt by a factor of at least two.

Now, when I fly manually, there's a feeling of spontaneity to the whole trip: I'm going to reach another celestial body, but I'm not sure which one. I twitch the throttle from "the engines are overheating" to "the engines exploded" in lieu of gradual thrust adjustment, I forget to turn until halfway through a burn, and I generally skip all the nice things like orbits and just aim for things until the map says I'll hit them, then take the appropriate steps to not die. I am a horrible space pilot. If I can still get something that small to the Mun and back, you know it's too heavy for the job.

[factotum]

The problem was getting up there. My moon vehicle is really quite basic. The smallest capsule, four small side engines, one of the smallest fuel tanks, four lander legs. It should be enough to land on the Mun and then get back to Kerbal.

Does it really need four engines? Would a single bottom-mounted engine be lighter? If you're really struggling, you could always do what NASA were originally planning to do for the Moon mission before they decided to go with the single massive rocket approach--namely, an Earth orbit rendezvous; put up several separate ships into Kerbin orbit and get them to hook up together. Multiple launches means each one can be smaller. In the case of a Mun voyage two ships should be ample; one to actually perform the trans-Munar injection burn, and one as the lander you'll use when you get there.

[Jimorian]

Strangely, I haven't tried any landings yet, so most of you are way beyond me for that. I'm just fascinated by the logistics of space, so putting stations everywhere is a natural extension of that. Of course, once they're in place with all these massive tanks of fuel, all I have to worry about it getting the probes and landers to them and I can top them all off for whatever mission I want.

Building up my support fleet for the Jool station.

Train with the 3 extra fuel tanks, RCS lower extention, and 2 tugs being pulled by a 4-nuke-engine tug. This will be enough to "complete" the station, but most of the orange tanks will be empty by then. When it was full, it weighed in at 184 tonnes.


So here's 1 of the resupply tanks I'll send with the fleet. No idea yet how many I'll need to top off the station, though it's looking like it will get there with maybe half the fuel left, so perhaps 6 will do.


The main station has left Kerbin influence, but with the nuclear engines, it takes several passes to get enough delta-V for the full trip, so here's the current orbits of the parts train, and 2 fuel tanks (the 3 highly eccentric orbits). That represents about 1/3 of the total delta-V to get to Jool, the rest of which I'll supply on a long burn at Periapsis for each of them. I'll probably have time to get a couple more fuel tanks in orbit while waiting.

[Eldan]

Hm. That seems a solid design, Trekkin. I'm just wondering. No nose cones on your side engines? I mean, half the numbers in the game mean more or less nothing to me, but I'd assume those would be worth it.

Oh, and for the central engine, why three stacked smaller tanks instead of one big one? Is that in some way more efficient?

The four side engines for my lander were mainly for symetry. The way I had it set up, I couldn't place the engine directly under the tank, there were attachment points there. So I placed them around the central fuel tank. Tree might work too, or even two.

[Trekkin]

You'd think they help, but the way drag works, I don't believe they do. I'll just go run off and test it.

EDIT: And the two stacked smaller tanks are so the engines line up nicely to sit on the pad; if I could do 3/4ths of an orange tank I would.

I'm not sure how you're seeing three tanks. above the decoupler is a Poodle engine inside the cowling, and above that is a Rockomax X32 tank. Below it are an X32, an X16, and a Skipper engine.

[Eldan]

Hm. My lander looks almost identical to yours, but yours has more fuel, it seems and a central instead of a side engine. I think I'll follow your lead on that.

[Zorg]

At the moment nosecones are purely cosmetic and only add to your drag. The plan is that they will subtract, but the system can't handle that yet.

[AgentPaper]

Spoiler

Show

Here. I flew it to the Mun and back manually; MechJeb is just there to show the delta-v. Getting into orbit eats into stage 3's fuel; by that point you have around 1000 m/s to crash into the Mun, and another ~2900 to land, take off, and crash back into Kerbin. The whole thing is overbuilt by a factor of at least two.

Now, when I fly manually, there's a feeling of spontaneity to the whole trip: I'm going to reach another celestial body, but I'm not sure which one. I twitch the throttle from "the engines are overheating" to "the engines exploded" in lieu of gradual thrust adjustment, I forget to turn until halfway through a burn, and I generally skip all the nice things like orbits and just aim for things until the map says I'll hit them, then take the appropriate steps to not die. I am a horrible space pilot. If I can still get something that small to the Mun and back, you know it's too heavy for the job.

Looks like your design is mostly solid, although you definitely have way too much RCS on there. Cut out the large tank, and replace it with 4-8 of the small radial ones. You should only use RCS at all when you're landing, and even then it's not really necessary if you do it right.

More importantly, it sounds like your issue is that you're not transferring to Mun correctly. Pointing yourself at Mun and thrusting will get you there, but is extremely inefficient. This is why you're running out of fuel so early. Orbital mechanics aren't an optional nicety, they're absolutely essential. I would suggest doing some of the tutorials on the wiki to familiarize yourself with them, starting with Luna 9, which teaches you how to do a transfer and land on Mun.

[Trekkin]

More importantly, it sounds like your issue is that you're not transferring to Mun correctly.

You're right, but that wasn't the point of the design. Usually I fly with the maneuver nodes and a healthy respect for orbital mechanics; to put this to a more rigorous test, I flew the design there and back by guesswork and overcorrection. I figured if it could survive my least sensible flying style it was probably fairly forgiving so it might make a nice starting point for other people trying to figure out Mun rockets. Sure it's not perfect; I tried to make it easy to fly, not efficient.

The RCS is there for a similar purpose. I don't usually land with it, but back when I was learning how to land, it was great for stopping slight lateral movement without tilting the ship away from vertical. It's there as a big, overly massive, hydrazine-filled security blanket. I mean, I usually land on my engines, too, but again, going for forgiving here. The point was to have enough RCS that someone trying to land it couldn't possibly run out--and enough fuel in the main engine to boost the full RCS tank back into orbit. I never actually used the RCS.

Also, directly confirmed on the nose cones being worse than useless. They're outperformed by not having anything and on par with random junk of equivalent mass.

[AgentPaper]

You're right, but that wasn't the point of the design. Usually I fly with the maneuver nodes and a healthy respect for orbital mechanics; to put this to a more rigorous test, I flew the design there and back by guesswork and overcorrection. I figured if it could survive my least sensible flying style it was probably fairly forgiving so it might make a nice starting point for other people trying to figure out Mun rockets. Sure it's not perfect; I tried to make it easy to fly, not efficient.

The RCS is there for a similar purpose. I don't usually land with it, but back when I was learning how to land, it was great for stopping slight lateral movement without tilting the ship away from vertical. It's there as a big, overly massive, hydrazine-filled security blanket. I mean, I usually land on my engines, too, but again, going for forgiving here. The point was to have enough RCS that someone trying to land it couldn't possibly run out--and enough fuel in the main engine to boost the full RCS tank back into orbit. I never actually used the RCS.

Also, directly confirmed on the nose cones being worse than useless. They're outperformed by not having anything and on par with random junk of equivalent mass.

Sorry, I mistook you for Eldan, who was having trouble getting to Mun and back.

[Trekkin]

Oh. Suddenly things make a lot more sense. I think Eldan was having trouble with liftoff, though; I forget which tutorial covers that.

[Eldan]

Oh, I have no problem at all with orbital mechanics so far. I mean, I just burned six orange tanks of fuel and twelve boosters to get into Kerbin orbit, then maybe ten percent of a tiny tank to nudge myself to Mun.

Never tried pointing myself straight there, I went for a wide orbit around Kerbin, then an expanding apoapsis until I was on an approach vector that took me into a very shallow curve around the Mun. A bit of luck, really, but I landed in a fifty kilometer Mun orbit without really trying on my first try.

Then I crashed brutally because I was landing on the night side, couldn't see the ground and had way too much speed.

[nhbdy]

Oh, I have no problem at all with orbital mechanics so far. I mean, I just burned six orange tanks of fuel and twelve boosters to get into Kerbin orbit, then maybe ten percent of a tiny tank to nudge myself to Mun.

Never tried pointing myself straight there, I went for a wide orbit around Kerbin, then an expanding apoapsis until I was on an approach vector that took me into a very shallow curve around the Mun. A bit of luck, really, but I landed in a fifty kilometer Mun orbit without really trying on my first try.

Then I crashed brutally because I was landing on the night side, couldn't see the ground and had way too much speed.

I'd guess your trying to lift something too heavy, or have sub optimal staging then, because with 7 orange tanks I can get a full one, with RCS and a tug sporting twin nuclear engines to low kerbin orbit

[Mando Knight]

Oh, I have no problem at all with orbital mechanics so far. I mean, I just burned six orange tanks of fuel and twelve boosters to get into Kerbin orbit, then maybe ten percent of a tiny tank to nudge myself to Mun.

Are you dropping your extra mass as you use it up? That might help...

[Hawriel]

I finally landed my first probe on Mun. Took me three tries. I then tried to fly it to a near by object ran out of fuel and crashed it.

Now I'm working on an Apollo type capsule.

[factotum]

I'd guess your trying to lift something too heavy, or have sub optimal staging then, because with 7 orange tanks I can get a full one, with RCS and a tug sporting twin nuclear engines to low kerbin orbit

Sounds about right--I know I can get a full orange tank with RCS and a probe body attached into LKO using a five-booster setup. Don't really like to build my boosters bigger than that because of the chances of Fun happening on the way up!

[Eldan]

I must be doing something wrong, anyway. I'll make a second attempt tonight because I think the basic setup is right, I just need to learn how to land.

[Artanis]

Hat Films (whose Minecraft-related stuff might be familiar to some people) have a video of them attempting to play KSP. Their "accomplishments" in the video are the exact opposite of impressive, since one of them is terrible and the other two had never even seen the game before, but it's entertaining as hell to watch.

[Eldan]

Third try, actually managed to get the capsule down to the Mun in one piece. No fuel to get back, though. Adding more boosters.

[Trekkin]

Concerning fuel:

Is there any table or anything out there that lists the delta-V required to get back from low orbit around any planet in the Kerbol system to low Kerbin orbit? I've been using that map that looks like a subway map, but it's telling me around 4.5 km/s delta-v for returning from Jool, and the wiki says only 1.9.

I'm trying to design a reusable module for getting back; the idea is it carries the lander and a drop tank there on the outbound trip, then jettisons both and returns home on an integral fuel tank. I'd like to make it relatively light, but if I have to burn 5 km/s getting home...

[Jimorian]

I haven't checked, but the difference might be re-establishing a parking orbit around Kerbin vs. just ploughing right into the atmosphere for return because you don't have to worry about atmospheric heating for now. So yes, it is probably the higher number for what you have in mind. You can still use atmospheric braking, however, to drastically lower the dV required on board for return.

EDIT: added some mods and YouTubers to OP.