So, you can limit SRB thrust with the thrust limiter.

[gompasta]

Is this intentional? Is there any practical uses for it? Is there any impractical danny-style uses for it?

[Thiel]

It quite handy if you have an asymmetrical design.

[KerbMav]

The SRB will burn its fuel slower, burn longer, the rate of acceleration will be lower - makes sense if you need boosters but do not want to lift off with a TWR of 2+ and you also fight drag less in the lower atmosphere as when you push at full "throttle".

[Red Iron Crown]

It's useful if you want an SRB to burn for a longer time but don't need its full thrust potential.

[pauix]

You mean you can limit their thrust mid-flight or you can only tweak them at the VAB?

[Red Iron Crown]

You mean you can limit their thrust mid-flight or you can only tweak them at the VAB?

In the VAB. Once lit, you're committed to the thrust setting.

[biohazard15]

You may want to tweak their thrust if you're launching something light, or something sensitive. I've staged one of my light rockets this way (it's made from mod parts, but the same principles work for stock):

- 1st stage: Launch clamps and SRBs ignition (2 SRBs). They're tweaked to 60%.

- 2nd stage: Jettison spent SRBs and ignite main engine

Main engine is not very powerful, but has a high vacuum Isp. So the idea is: use SRBs to bring it to high altitude and ignite it there, instead of wasting fuel during initial ascent.

What I gain: without boosters, this rocket can put 1.5 ton to LKO. With non-tweaked boosters, it can put up to 4 tons to LKO. With tweaked boosters, it can put up to 5 tons to LKO or 1.5 ton to Munar or Minar orbit.

[cantab]

It's extremely useful. As mentioned, lower thrust means a longer burn time. If your boosters are giving more thrust than you need, you'll get more out of them by reducing it, just the same as if you're using liquid engines. If they're overheating, taking the thrust limiter down a bit can stop that too.

Indeed, it's probably more useful on SRBs than on liquid engines, since it's the ONLY way to control the behaviour of SRBs.

[RoboRay]

You can actually design a proper, efficient launch profile using just tuned SRBs. Say, for a small satellite launch:

S1: A small RT-10 at full thrust, but only half fuel quantity. It gives a lot of thrust to get you up to speed quickly, but burns out rapidly so that you don't get pushed way past terminal velocity (or into dangerous atmospheric heating if DRE is installed).

S2: A big Rockomax BACC at 30% thrust and full of fuel. It provides a long-burning moderate thrust to lift you up out of the atmosphere and build most of your horizontal velocity.

S3: A ring of several Sepratron pairs mounted around a stack decoupler. Fire as many pairs in sequence as are required for final orbital insertion.

Another tuned RT-10 or even another BACC can be inserted between S2 and S3 as needed, depending on the payload. It may take a few tests to figure out the best thrust-limits and fuel-quantity for your launch.

Edited April 4, 2014 by RoboRay

[Vanamonde]

Yes, it's intentional, and it's been in the game since .23 or so. (Also, moved to gameplay questions.)

[Claw]

You can also tweak the amount of propellant if you want some TWR boost at launch but don't need all the extra dV. Or if you put some artificial weight limit on yourself.