When will launch pad accept larger craft?

[strider3]

I should say that I was using a gravity turn to 10% at 100m/s but that was all...no following of prograde marker. I am now working on my piloting skills to become more efficient thanks to your suggestions.

Vic the Newbal

[ag3nt108]

On 21 March 2016 at 4:55 AM, Snark said:

Yah, I like taking off on SRBs-only, partly because of the burn-the-lowest-Isp-fuel-first thing, and also for the purely irrational reason that I just really like SRBs on a visceral level and get a thrill from roaring off the pad on a spectacular column of flame. 

I usually smooth out the ride a little by arranging my radial SRBs in two symmetry groups rather than one (e.g. two groups of 4 rather than 1 group of 8), with one group having a higher thrust limiter than the other.  Take off on all of them together, but the high-thrust ones burn out first and are jettisoned while the second group continues to burn a while longer.  (I call it "poor man's asparagus".)  Smooths out the ride, TWR doesn't slam so hard near the end of the SRB burn.  Gives the SRB portion of the flight some legs.

What do you use for control authority on the way up to 10k?  I tend to use engine gimballing so even with craft that do use SRBS for a "kick" of the pad I will be burning at least 1 gimballed engine.

[Snark]

4 hours ago, ag3nt108 said:

What do you use for control authority on the way up to 10k?  I tend to use engine gimballing so even with craft that do use SRBS for a "kick" of the pad I will be burning at least 1 gimballed engine.

The answer is "practically nothing." In a well-executed gravity turn, the ship just follows prograde all the way up, and gravity plus aero forces just naturally keep things on track. It's pretty close to hands-off flying, and only occasional tiny nudges are called for.

The only real control authority needed is that initial eastward "nudge" to start the turn, which doesn't have to be much, since it's only 2-3 degrees and happens practically right off the pad, when the ship is going 20 m/s or so.

The amount needed is small enough that for most ships, reaction wheels are plenty (and I don't mean "spam reaction wheels for takeoff", I just mean the reaction wheels I'd normally have on the top stage or two anyway for attitude control in space).

For really big ships (e.g. the kind that take off on multiple Kickbacks), a couple of AV-R8 winglets down on the bottom end of the SRBs will do the trick.

That's about it. Thrust vectoring is typically not needed.

[Warzouz]

On 18/3/2016 at 0:50 AM, Victor3 said:

OhioBob...can you tell me what engines you are using here?

I really feel like I'm overkilling the entire thing??

 

You should use a delta-V reading mod, such as KER. It helps a lot to get a correctly fuelled and powered rocket. Most of us plays with such a mod.

A rocket needs 3200m/s to go to LKO (3500 with bad flight plan of non streamlined payload). It's easy to get to LKO with a 2 stage rocket.

The only issue with lowtech is you only have small tanks and you need many of them. With bigger parts, you need less parts (which is a strange constraint). Same with rocket size. You'll find that heavier rockets are easier to fly because they flip much slower and you've time to handle the situation. With smaller rockets, you must be quicker.

That's why I don't like small rockets. If my payload is too small (ex satellites), I manage to send 4 or 8 of them in one launch.

I there would be only advice : think light and simple.