I think some lights are going on somewhere

[GoSlash27]

4 minutes ago, Starchaser said:

v3 is only to do a scanning contract orbiting kerbin.

Starchaser,

 That's cool. Still a dramatic improvement over where you were.

 A few pointers I can give you:

 *The DV to LKO should be roughly split evenly between the first and second stage. First stage DV calculated at 1,800 m/sec DV at 1/2 ATM, and 2nd stage 1,700 m/sec DV at vacuum. This results in a good approximation of a minimum total launcher mass.
 *I think you can rein in your t/w quite a bit. I generally use 1.4:1 t/w for LF&O first stage (1.2 for SRB), 0.7 for transstage, and 0.5 for orbital ops.  Where this allows you to use lighter and cheaper engines, the benefits will compound backwards down the stack. If you wind up with the same engine, don't bother throttling back once you're past Max Q.
 * For this short a DV budget, you should check to see if a 2 stage rocket is a more efficient solution.

Best,
-Slashy

 

 

 

[Starchaser]

32 minutes ago, GoSlash27 said:

 *I think you can rein in your t/w quite a bit. I generally use 1.4:1 t/w for LF&O first stage (1.2 for SRB), 0.7 for transstage, and 0.5 for orbital ops.  Where this allows you to use lighter and cheaper engines, the benefits will compound backwards down the stack. If you wind up with the same engine, don't bother throttling back once you're past Max Q.
 * For this short a DV budget, you should check to see if a 2 stage rocket is a more efficient solution.

On t/w, I mentioned I hadn't adjusted the thrust limiter on the SRB yet, but it was on my "to do" list.

I hear you on the efficiency. However, with this as a 3 stage rocket, I had to wait to deploy the fairing because it was still flaming when the second stage ran out of fuel. I don't want to expose my very blunt probe to those kinds of atmospheric forces....but maybe there's another way I could apply the fairing....hmm...

[GoSlash27]

3 hours ago, Starchaser said:

with this as a 3 stage rocket, I had to wait to deploy the fairing because it was still flaming when the second stage ran out of fuel.

Starchaser,
 If you tone down the thrust, you won't have to worry about that because you won't be flaming on the way up.

Best,
-Slashy

[Starchaser]

3 hours ago, GoSlash27 said:

 If you tone down the thrust, you won't have to worry about that because you won't be flaming on the way up.

At that point I had. I was about 1.4 on the launch pad. (I target 1.35 to 1.45 myself.)

 

[GoSlash27]

3 minutes ago, Starchaser said:

At that point I had. I was about 1.4 on the launch pad. (I target 1.35 to 1.45 myself.)

 

Ah, but your second stage was like 1.7, ramping up to 3.8 as the fuel burned. I understand in your case that you'd need around 1g to start with, given the early termination of the boost phase, but 1.7-3.8 is still way more acceleration than you need. Likewise, the 3rd stage is 3.4 minimum, where 0.5 would be fine.

Best,
-Slashy