What i did wrong with my rocket?

[Pawelk198604]

Craft

http://1drv.ms/1rAYh4O

How to make my rocket more efferent, i use stock parts, i know maybe i should look for mod, when i adding fuel tanks, twr ratio of 1st stage falling bellow 1

Edited August 27, 2014 by Pawelk198604

[CavemanNinja]

I'll assume you're asking for efficiency.

First, it looks like you're pulling a gravity turn way early. You typically want to start at 10k, and slowly turn over, increaseing both your vertical speed and horizontal speed for an optimal ascent.

Second, i would think to make your rocket wider, and have more efficient engines burning rather than one big one slugging through the lower atmo. by itself.

Third, you don't need an apoapsis above 75km, unless you're looking for something other than LKO (low Kerbin Orbit)

Finally, ditch the escape tower once you don't need it. A little Delta V can go a long way!

(I've found stock parts to be just a good as mod parts, if not better!)

[Superfluous J]

First, use the video tags:

[noparse]

[/noparse]

Second, your TWR is terrible. You want 1.5-2.0 (I prefer about 1.6 usually) off the pad. The solution there is either moar boosters (solids radially attached) or less payload (send one guy in a mk1 capsule. It's a lot lighter)

Third, your turn was too early, especially because your low TWR meant you were going slower than you should be at that height. Make your turn at about 10km, hopefully going about 250m/s

Fourth, once your apoapsis got much above 80 you should have cut the engines and coasted up, to circularize there. Burning low just pushed your apoapsis up and up and up.

The biggest thing though is your TWR (as you suspected). Having enough dV to get to Mun and back doesn't mean anything if you burn twice as much of it as you should for the first few minutes of your launch.

EDIT: Fifth, I got ninja'd!

[SRV Ron]

How to make my rocket more efferent, i use stock parts, i know maybe i should look for mod, when i adding fuel tanks, twr ratio of 1st stage falling bellow 1

I'll give this a test when I get back home. Quick observation is it is so heavy that the first stage is using up it fuel to fight gravity. A set of SRB and some weight reduction above may be enough to get it to the ideal TWR for the first 10K or so.

Have you done single Kerbal flights to Mun and back non apollo style? That is so much easier to do.

An example rocket below from Career. (Mods used but not required. The lander is stock.)

This probe will go to Mun and return.

Edit, Found the all stock design that did the mission

If you need more boost, this design gave more fuel for landing and return.

Early Career, nothing complex, no separate lander, no complicated asparagus staging.

Edited August 27, 2014 by SRV Ron

[Pawelk198604]

I think i just try to do few more unmaned mission to get more tech, than unlock mechjeb ascent feature, maybe computer do this better

[sojourner]

Sometimes less is more. Reduce the fuel load a little bit on the first and second stages to get your TWR up. You'll be surprised how much better it flys.

[kStrout]

Your rocket is way to tall and skinny. I find that if you need struts stopping the rocket from wobbling, it's too tall. period. Try building outwards more instead (if you really want to do this 5 mainsails for the first stage gets you the right amount of TWR and looks very saturnVish)

[cantab]

There's more problems with your flying than your rocket. Try and avoid having to pitch back up again after you pitch down, and you can stand to throttle back on the second stage too, keep the TWR below 2 or so. And of course you can use a lower parking orbit.

The first two stages on that rocket are very similar to one of my most successful designs, except I use just one big tank in the second stage. Gets 45 tons to LKO no problem and with a mere handful of parts so it keeps the lag at bay. Low launch TWR has some upsides - you're lifting less mass of engine and will spend less money on said engines. You do need more delta-V for orbit, but that's no big deal as long as you're mindful of it.

[Reactordrone]

Your lander/command module combination is very heavy. You could make a single stage lander command pod with a single rockomax X200-16 tank, that would save all the weight of the lander and its massive RCS tank. If you want a separate lander I'd reduce the fuel on the first stage and add a small third stage for transfer and strip out as much weight as possible from the lander and command pod.

[Kryxal]

I'd probably toss a pair of the big SRBs on there radially and throttle the main engines down till they're done with ... possibly 4 SRBs instead. I actually like where you started your pitchover, you might even do so earlier, but only by a few degrees. Of course, losing mass off the top of the rocket works very well too...

[Sirine]

@Pawelk19860(OP) : That rocket is pretty much efficient. It is just you need to improve your driving skill.

How is how.

http://forum.kerbalspaceprogram.com/threads/29364-When-to-start-Gravity-Turns?p=1365808&viewfull=1#post1365808

Staging 2 & 3 got mess up. (Check decoupler and engines)

After load your craft and tested, it is lower Kerbin orbit (LOK) achieve-able (70x70km) with 2 stages + 1 little bit 3rd stage..

Javascript is disabled. View full album

Edited August 28, 2014 by Sirine

[SRV Ron]

I think i just try to do few more unmaned mission to get more tech, than unlock mechjeb ascent feature, maybe computer do this better

That explains your nonstandard parts when I went to load it for testing.

I would suggest a ring or six or eight SRBs to assist the launch stage of the flight. That will get it moving high and fast enough for the first stage engine to operate more efficiently. Proper bracing on the command to lander to booster will stop the wobble during launch.

[Reactordrone]

If you change one of the S3-14400s on the first stage for an S3-7200 and change the S3-7200 on the second stage for an S3-3600 on the second stage and ditch the RCS ascent stage on the lander the rocket will get to the Mun and back just as well as it does now and it won't have a sub 1:1 TWR on the pad.

[Ikaneko]

Add some SRBs to the rocket on the first stage to raise your TWR. Also, scale your second stage down to 2.5m for greater efficiency.

Edited August 28, 2014 by Ikaneko

[KerikBalm]

Ok, after looking at image 16, I see the problem...

The simplest answer would be a ring(4?) of SRBs around your lower stage, or flying it better.

I see you are trying to do an apollo style rocket, you even use a monoprop Munar ascent stage, you probably do not want to strap SRBs to the sides and call it an SLS.

however... lets look at this:

http://imgur.com/a/YocF4/embed#16

I've done an apollo style landing with SLS parts, 3 stages, it was much smaller than yours, I can't load it up now... but... I'll look later.

I kept having to make my upper stage smaller because I was always left with way too much dV.

Looking at image 16... your lander descent stage: you use 2* Rockomax200-8 tanks -> you should only need 1 (in fact, to make it worthwhile doing a 2 stage on mine, I had to not even do a full fuel load).

If you want to do mono-prop like Apollo did, switch this for the large RCS tank - you'll save weight on tanks (3.4 vs 4.5 tons of tank), and engines (I recommend 3x monoprop engines)

Then for your lander ascent stage-> that RCS tank is way more than you need. I haven't used those low ISP RCS engines.... but I suspect just 2x cylindrical fuel tanks should be enough for orbital rendevous.

Then we get to your top stage... using 2* Rockomax X200-16 Fuel Tanks.... reduce this to 1. My design had a x200-8, not a 16, but it looks a bit short like that... And since you don't fly very efficient (based upon your launch), I won't tell you to go down to a -8 instead of -16, although, consider filling it only 2/3 full

Next: Your SAS module - entirely unneeded for the upper stage (at least once you size it down)

Now, back to your launcher... again, assuming a desire to be like apollo... where is your 3rd stage?

I recommend:

Stage 1 - S3 KS-25x4 Engine Cluster + Kerbodyne S3-14400 Tank for stage 1

Stage 2 - Kerbodyne KR-2L Advanced Engine + Kerbodyne S3-7200 Tank, and *maybe* a Kerbodyne S3-3600 Tank

Stage 3 - Rockomax "Skipper" Liquid Engine + Rockomax X200-32 Fuel Tank

Relative to the previous launcher design:

Your first stage is not lifting: 1x 14400 tank from the 1st stage (82 tons), 1x 14400 tank from the 2nd stage (82 tons): -164 tons

It is lifting (optionally) 1x S3-3600 tank in the 2nd stage (20.5 tons), 1x x200-32 tank in the 3rd stage (18 tons), 1x Skipper engine (3 tons), 1x decoupler (0.4 tons)

In total it is lighter by 164 - 18 - 3- .4 - 20.5 = 122.1 tons lighter.

It is also now 3 stages like the Saturn V, and the 3rd stage should be getting you most of the way to the moon (again, like the Saturn V) if you build your upper stages light enough.

You are simply asking your single engine to lift too much fuel.

You don't need more engines, you just don't need to lift as much fuel.

Note that the weight reduction in the command and lunar module comes down to:

-1x 200-8 tank : 4.5 tons saved - switching to RCS, is another 0.5 for the engine + 1.1 for the fuel tank = 6.6 tons saved

- FL-R1 RCS Fuel Tank + 2x cylinders: 1.9 tons saved (you may want to do 3x though, if you don't dock without wasting a lot of fuel, would still save 1.15 tons)

- Rockomax X200-16 Fuel Tank = 9 tons saved

Total saved 6.6 +1.15 + 9 = 16.75 tons

Add this to the reduced launcher weight, 16.75 +122.1 = 138.85 tons lighter, and it should still have plenty of dV to get the job done, and it will be closer in design to the Saturn V

Edited August 28, 2014 by KerikBalm

[Pawelk198604]

Eagle has landed

I used 5 x Mainsails in first stage, in second stage i used parts from NASA pack

[Pawelk198604]

[KerikBalm]

#1) If you are using stock aero you were ascending too fast in the lower atmosphere, ascend at terminal velocity

http://wiki.kerbalspaceprogram.com/wiki/Kerbin#Atmosphere

#2) You are setting your orbit higher than neccessary, aim for about 75 km, not 100+, its just more efficient that way.

#3) You really should learn to do a Gravity turn properly... putting you Apoapsis out into space, and then burning at the top is pretty inefficient (oberth and gravity drag)

As soon as I figure out how to upload a craft file (I know I did it once), try doing the mission with the provied craft

[Pawelk198604]

this is my recent craft, which i used for my daring Munar mission

http://1drv.ms/1sKMIE1

While it's maybe consider as cheating but i transferred some fuel and oxidizer to second stage before TMI Burn (Trans Munar Injection)

But i have some moments of terror when it come to TKI (Trans Kerbin Injection) it was miss about 5-10 dV, but the burn was controlled by MechJeb 2, so i was avoided tragedy because than MechJeb go to SCE to AUX (literally and figuratively) it just switched to RCS thruster

[Reactordrone]

It would have been more efficient to use the remaining fuel in the second stage to go part of the way to the Mun and then ditch the extra weight and complete the burn with the command module's engine. You can even loop around and do the remainder of the burn at periapsis on the next orbit, just remember to adjust the burn for the Mun's new position.

[KerikBalm]

Try it using this craft:

https://www.dropbox.com/s/kt0954r1ix00nlr/Saturn%20V.craft?dl=0

Yes, many of the tanks are not full on purpose - its made efficiency compromises for aesthetics.

That said, it has a good margin for error, but does still require a fairly efficient flight.

If you cant do a complete mission with it now, I suggest practicing until you can.

[Kryxal]

It would have been more efficient to use the remaining fuel in the second stage to go part of the way to the Mun and then ditch the extra weight and complete the burn with the command module's engine. You can even loop around and do the remainder of the burn at periapsis on the next orbit, just remember to adjust the burn for the Mun's new position.

Adjust your second orbit before the first burn, if you have a bit over 400 m/s left you can get into an orbit with a period of 90 minutes, and with your original orbit being about 30 minutes, you just set up your burn for 3 orbits later, plan the burn, and move 3 orbits back. Bonus points if you brake some at apoapsis to de-orbit debris then re-establish your periapsis.

[Superfluous J]

Adjust your second orbit before the first burn, if you have a bit over 400 m/s left you can get into an orbit with a period of 90 minutes, and with your original orbit being about 30 minutes, you just set up your burn for 3 orbits later, plan the burn, and move 3 orbits back. Bonus points if you brake some at apoapsis to de-orbit debris then re-establish your periapsis.

Nice technique. I'm going to explore the possibilities around it. I recently totally boned up an Eeloo ejection that this technique could have really helped on.

[Pawelk198604]

Try it using this craft:

https://www.dropbox.com/s/kt0954r1ix00nlr/Saturn%20V.craft?dl=0

Yes, many of the tanks are not full on purpose - its made efficiency compromises for aesthetics.

That said, it has a good margin for error, but does still require a fairly efficient flight.

If you cant do a complete mission with it now, I suggest practicing until you can.

I used you craft in sandbox and it's realty great, i must admit with sadness that's is even better than my own , but I would not be me if I did not have any objections.

After separation cm from lb, the shroud that cover LM is still in place, i docked but it's covered the CSM windows.