Is there something wrong with my design?

[ISmokeThis]

Hey guys,

I have managed to get a kerbal onto Mun but I do not have enough fuel to head back home. The vessel required to get him there was already quite large, but I went about adding more fuel and thrust to it and intended to launch a rescue ship that could arrive (unmanned), pick up the stranded kerbal, and head home. Unfortunately I am unable to build this spacecraft. I've gotten to the point where it has become very difficult to keep my ship symmetrical while also adding more thrust. Currently the ship I have designed looks like this:

I get a feeling that I don't need a ship this large to bring a lander to Mun and back. What am I doing wrong? Thanks

Also, currently in career mode, I do not have enough points to unlock the multi-manned pod, so I need an empty (and thus an unmanned) ship. To do this I need to add the Stayputnik part as well as a pod. Is there a way I can save the ship with the game also remembering that the ship is designed to be unmanned? Every time I am about to begin the launch I need to clear the pod of its crew.

Edited December 29, 2013 by ISmokeThis
ANSWERED

[AmpsterMan]

You can get to Mun, back to Kerbin, to Mun again, go to gilly, change it's orbit, land on Tylo, and then return to Kerbin and still have enough fuel to land on Mun again.

In all seriousnes, you might want to go a bit smaller. If you need some help, try using the Kerbal Engineer mod if you need to know how much delta-v, twr, etc your craft has.

Also, to make your craft unmanned by default, save your current ship as a subassembly, then make a new ship with the stayputnik probe as the main part. Attach your subbassembly.

[Landge]

That is impressive but way over designed for a trip to Mun. Here is one I made to travel to mun before I unlocked batteries.

Edit: The little lander at the top can make it back to Kerbin on it's own. 3 FL-T200's with 3 LV-909's are used. 2 for landing and 1 for the return trip, jettisoning the 2 side tanks at take-off.

Edited December 28, 2013 by Landge

[ISmokeThis]

You can get to Mun, back to Kerbin, to Mun again, go to gilly, change it's orbit, land on Tylo, and then return to Kerbin and still have enough fuel to land on Mun again.

In all seriousnes, you might want to go a bit smaller. If you need some help, try using the Kerbal Engineer mod if you need to know how much delta-v, twr, etc your craft has.

Also, to make your craft unmanned by default, save your current ship as a subassembly, then make a new ship with the stayputnik probe as the main part. Attach your subbassembly.

I haven't been doing serious calculations or anything. Are you guys sure you haven't considered the fact that I'm trying to get my lander there? Its much heavier than a single pod. If you were to guess, what do you think my ship needs more or less of? Also, I'll be sure to give the mod a try but I doubt I'll make any use of the stats I'm given...

[Specialist290]

Out of curiosity, could you post a screenshot with just the intended lander, not the launcher or transfer stages? Your current rocket does strike me as a bit overengineered for its intended destination, and I think we could give some better, more specific advice if we knew exactly what the payload we're dealing with is.

[Taki117]

I never thought I would say this to someone playing KSP...but you need less boosters.

[Clockwork_werewolf]

Firstly about the Unmanned ship getting remanned every time, I wish I knew a way to do this. I will often send a ship to launch, check everything doesn't break then send it straight back to put the whole crew in because I forgot to tell it I wanted 3 crew. Again. Like last launch. And the one before that.

I would say the most important parts to remember with any ship are

1. Keep it at the right speed

2. The space engines should be efficient not powerful

3. Each stage should be a bit or a lot smaller than the last.

1. This is hard but I suggest the kerbal space program wiki's page on Kerbin. You want to be going at 100m/s on launch (impossible but worth getting near) So bottom most stage can have very little thrust but LOTS of thrust to weight. In your ship I would suggest more small SRB's on the bottom stage. They should burn fast get you to 90-120m/s then the trust should fall so that its only accelerating a bit and hitting about 120m/s @ 2K 140m/s@5k or something near that (I forget the exact numbers). It is strange but it will greatly help with efficiency and save fuel and therefore size.

2.Easy enough to do make sure space engines are the little ones, though I think I can just see in the picture this is right.

3.You have some stages that are the same size as the one below, this does mean you get to drop their engine weight and empty tanks but the bottom one is trying to lift the full tanks and an extra engine. This is a hard balance to get and I still struggle with it sometimes.

[ISmokeThis]

Out of curiosity, could you post a screenshot with just the intended lander, not the launcher or transfer stages? Your current rocket does strike me as a bit overengineered for its intended destination, and I think we could give some better, more specific advice if we knew exactly what the payload we're dealing with is.

Sure, here you are:

Edited December 28, 2013 by Specialist290
Fixing broken image link.

[ISmokeThis]

Also, to make your craft unmanned by default, save your current ship as a subassembly, then make a new ship with the stayputnik probe as the main part. Attach your subbassembly.

This didn't work for me, but thanks for the idea.

[Peppe]

Looks like boosters are lifting more boosters and maybe not contributing to actually lifting the payload.

Try scaling back the boosters to stack onto eachother.

[ISmokeThis]

Looks like boosters are lifting more boosters and maybe not contributing to actually lifting the payload.

Try scaling back the boosters to stack onto eachother.

Well if they can get it off the ground they're contributing even just a little . Although, I agree with all of you that this is definitely an inefficient design ><

[Burtsp]

Hey ISmokeThis I am a fairly new player, never posted before. I learned a ton at the wiki site using the DeltaV charts. Recommend using Mechjeb or the engineer mod to display data on TWR and DeltaV. Once you make sense of this data which does not require a degree in physics your designs will become easier and more effecient.

[Kerbart]

My first Mun visit was based on a tutorial by The Manley. I think it was one FLT-400 and two FLT-800 if my memory serves me right.

Then again blasting yourself to Mun using stacked SRB's... there's a certain Kerbalesque attractiveness in the concept. You can just see the reentry effects around this rocket while it's blasting through 20km altitude doing mach 4...

[SRV Ron]

As this from the demo can land on Mun and return, you are way overbuilt with boosters that can barely lift themselves into orbit let alone a payload to Mun.

[Peppe]

Sure, here you are:

http://cloud-2.steampowered.com/ugc/687095438649957275/0C2F47875D8D2010E336796E9F8F358466580249/

Looks like ~4 ton lander.

Add maybe 8 ton transfer stage, so your lift/kerbin orbit stages should be

12 / .15

Should shoot for kerbin orbit with a lower stage ~80-100 tons.

[ISmokeThis]

Here is my next design. It has the same problem; There isn't enough fuel to leave Mun.

[ISmokeThis]

Thanks for the pics Ron, I'm going to try to add more radial thrusters to the ship. For now, however, I plan on reading up on the DeltaV stuff on the wiki. Thanks for helping guys.

[LethalDose]

Uhm, how far is that beast getting? Maybe we can figure out what where you're going so very wrong. Because, yeah, that's waaaaaaayyy more than you need to get to the Mun.

Based on my experience, that lander will not be able to deorbit from the Mun, land on the munar surface safely, and make orbit again, let alone get back to Kerbin. It MAY be able to land, return to orbit, and get home, BUT only if a previous stage is used to deorbit and begin surface approach.

Instead of trying to go right to landing on the Mun, try building a rocket to go out and only orbit the Mun, and work to reduce the mass of that simpler rocket. Then build back up to get enough lifting power to get a lander to the mun.

[Kerbart]

Here is my next design. It has the same problem; There isn't enough fuel to leave Mun.

*snicker* Actually, there enough fuel to leave Mun. And probably to make a stop on Eve on the way back. However with all that stuff stacked your TWR (Thrust to Weight Ratio) is probably insufficient. Take a look at this Scott Manley video. A landing stage of a single FLT-400, a launching stage of two FLT-800's and two boosters (each two FLT-800's as well) is all he needs.

His recommendation is to go for Minmus first; it's further away but much lower gravity, making landing a lot easier. But I'm pretty sure this will work with Mun as well.

http://youtu.be/cmAMGJm-bwU

It's always good to run your mission with a white-knuckle approach towards your fuel reserves. You'll be amazed how much lighter things can be if you run your missions as light as possible.

[LethalDose]

Hey, ISmokeThis, when are you starting your gravity turn?

[ISmokeThis]

Hey, ISmokeThis, when are you starting your gravity turn?

Wow, thank you for this. I am reading up gravity turns right now. I think I was doing it wrong by going 0 degrees then 90 degrees. Instead, I need to curve my corner?

[ISmokeThis]

I had always imagined that the air drag would be too strong to make slowly tilting your rocket early on worthwhile.

[Taki117]

Generally you want to begin your gravity turn about 7km up, then just pitch over slightly (towards heading 090) and gradually turn until your apoapsis gets to your desired parking orbit (I use about 80km) then circularize and plot a maneuver that intercepts the Mun.

[LethalDose]

I had always imagined that the air drag would be too strong to make slowly tilting your rocket early on worthwhile.

Yep, the drag slows you down under 20-30 km, but above that it's not too problematic. I typically do the following during :

1. Sea Level to ~ 10-15 km, straight up
   
2. 15 km to height where my trajectory has an apoapsis > 80 km, less 15-25 degrees towards the E
   
3. Then coast until near Apoapsis
   
4. Then burn prograde until achieving orbital speed
   
5. Profit
   

This just works for me, but i'm sure there are more efficient methods. This is just an example, and even varies a bit between rockets. Most importantly, it's nice and simple.

Try building small rockets to just get into Kerbin orbit and practice gravity turns for a bit, THEN go back to engineering the rocket for Munar landers.

[ISmokeThis]

I'm currently on route to Mun. I made a gravity turn when leaving the atmosphere and I can't see any noticeable increase in fuel. However, I don't really have any idea of how much I would have if I didn't make a gravity turn.

Am I landing on Mun correctly? I just make sure I fall into its orbit then apply thrust towards retrograde motion.