Most efficient 2.5m rockets

[Dr. Muttonstache]

I'm extremely good at 1.25m part rockets, I have a really great design thats capable of getting a 120km-ish circular orbit. I have made quite a few 2.5m rockets (have made it to Duna, and Moho with those, very challenging, and a pain in the ass to get off the pad, many many failed attempts.) but none of them are as efficient as I'd like them to be, nor I can't build them as easily. I would like some pointers on building 2.5m rockets, not payloads, but the lifting stage itself (from launchpad to orbit)

Some screenshots of them would be great, and flying tips on the particular rockets (I know how to fly, im far from new to this game, just never really ventured into the larger parts.)

[Giggleplex777]

This is the most efficient 2.5m rocket I've ever built. It can put up to 40.5 tons to 72 km orbit and about 35 to 120. The rocket also has retrorockets to deorbit the booster stage. It has a maximum payload fraction of 16.21%.

It jettisons engines to increase delta-v. If it doesn't jettison its engines, it does not have enough delta-v to reach orbit.

[Dr. Muttonstache]

This is the most efficient 2.5m rocket I've ever built. It can put up to 40.5 tons to 72 km orbit and about 35 to 120. The rocket also has retrorockets to deorbit the booster stage. It has a maximum payload fraction of 16.21%.

It jettisons engines to increase delta-v. If it doesn't jettison its engines, it does not have enough delta-v to reach orbit.

Is that a decoupler or an SAS module smack dab in the middle of it? Could you screen it in the VAB so I could see if I can replicate it?

[Temstar]

The highest payload fraction for pure rockets for Kerbin launch should be around 16-17%, but if you can manage >10% I would consider that design pretty good. For Earth the payload fraction is usually around 4-5%.

If you are interested in efficient 2.5m rocket design have a poke around at these:

Zenith Rocket Family

I've employed pretty much all the tricks I know about building boosters into those. The only thing really missing is the "hybrid asparagus staged SRB" thing I sometimes do.

[UmbralRaptor]

While my Mainsail-based approach lacks Giggleplex777's efficiency, I still think a 14% payload fraction is respectable. (Heaviest payload flown is 37.1 tonnes to a 70 km orbit)

In general, fuel crossfeed helps, as does running pairs of struts between vertically attached tanks.

[Dr. Muttonstache]

While my Mainsail-based approach lacks Giggleplex777's efficiency, I still think a 14% payload fraction is respectable. (Heaviest payload flown is 37.1 tonnes to a 70 km orbit)

In general, fuel crossfeed helps, as does running pairs of struts between vertically attached tanks.

That's kind of like my 1.25m design, except bigger! I don't know why i didn't try this.

[Giggleplex777]

Is that a decoupler or an SAS module smack dab in the middle of it? Could you screen it in the VAB so I could see if I can replicate it?

It's a decoupler.

Plus, I don't recommend rebuilding it as it is very complicated and requires a very good gravity turn to get to orbit and have enough to deorbit.

[Dr. Muttonstache]

It's a decoupler.

Plus, I don't recommend rebuilding it as it is very complicated and requires a very good gravity turn to get to orbit and have enough to deorbit.

Like I said, flying is not a problem for me at all, it's the construction of this size of part. I'll try this one, see what happens.

[GusTurbo]

Temstar is really the best at this type of thing. His designs are rock solid.

[Endoric]

Temstar is really the best at this type of thing. His designs are rock solid.

or rocket solid!

[toric5]

i just do an asparagus staged rocket with mainsails, it can get just about anything into suborbital and then i can just use the maneuvering stage to circularize

[Giggleplex777]

Like I said, flying is not a problem for me at all, it's the construction of this size of part. I'll try this one, see what happens.

Here's the .craft file

I used part clipping to get the engines on.

Here are the timings to jettison engines (MET):

1. 1:10

2. 1:40

-decouple-

3. 3:15

4. 3:45

Press 0 to active the retro rockets on the core booster after you decouple and switch to it.

Make sure to do a very good gravity; it can't get to orbit if you don't.