Did the Space Shuttle loose delta V due the shifting of CoM?

[Albert VDS]

So I guess it would loose delta V by performing the balancing act of keeping the engines pointed at the CoM, but was it negligible or did it cut off a huge amount?

Before you post anything, this is not a thread to discuss your personal opinions about the Space Shuttle. It's only meant to for a discussion concerning it's performance.

[Kulebron]

Since the SRBs were burning downwards and main engines were burning at some angle, the CoM was at the crossing of the thrust vectors, and some delta V was lost in one vector pushing against the other:

/|

If you find that angle, you can calculate how much force was cancelling out. Or better, you can calculate a "what if" situation: what if both kinds of engines were burning in the same direction pointing at CoM, what the difference would have been.

The angle seems to be about 15 degrees, so losses are 1-cos(15deg) = 3.5%.

[EzinX]

So you have 3 main engines. The center of mass is ideally at a point located perfectly between all 3, and they must have carefully load balanced the cargo to achieve that, but obviously is not quite there. So you vary your throttle slightly, throttling back slightly on engines away from the CoM and throttling forward (or leaving them maxed) on the engines towards it.

Why would you tilt the engines at all?

That doesn't help, it adds lateral velocity components and torque which you don't want. You only lose delta v with throttling back in the sense that the burns will take slightly longer and gravity drag makes the delta v needed slightly more. If you have slightly more engine thrust available than your setting at "100% throttle" you won't have any change in net acceleration and won't lose any delta-v at all from your planned ascent.

[Ralathon]

It only really matters until booster separation. During the booster assisted flight they needed to burn the SSME at a slight angle to compensate for the uneven mass distribution. Post separation they'll just keep pointing the thrust along the prograde vector and tilt the ship to keep the thrust aligned. So the only point where you have engines pointed at an angle to the prograde vector (And thus the optimal launch trajectory) is the booster assisted section. And that only lasts 2 minutes.

So I reckon they did lose a bit, but not much.

[Bill Phil]

I wouldn't say it lost deltav, just that it used it inefficiently.