[Spaceships] External clamps and delta-v

[SCAR]

On p15 of Spaceships, under the External Clamp, the effect on Acceleration (G's) for clamped vessels is covered, but there is no mention of the effect on delta-V.
There obviously is an effect, but is there an easy way to calculate the combined delta-V?

[Anthony]

Originally Posted by SCAR

On p15 of Spaceships, under the External Clamp, the effect on Acceleration (G's) for clamped vessels is covered, but there is no mention of the effect on delta-V.
There obviously is an effect, but is there an easy way to calculate the combined delta-V?

Yes. (Available Delta-V) * (Ship Mass) / (Combined Mass).

[Ulzgoroth]

Originally Posted by Anthony

Yes. (Available Delta-V) * (Ship Mass) / (Combined Mass).

This is faulty if some of your ships have high fuel fraction, though, since the composite ship may not.

To avoid that, instead treat the combined ships as having a number of fuel tanks equal to (actual fuel mass) / (combined ship mass) * 20, and recalculate accordingly.

If the two ships have engines with different delta-V per tank, base the high fuel fraction multiplier for the total fuel of all sorts aboard.

[malloyd]

Originally Posted by Anthony

Yes. (Available Delta-V) * (Ship Mass) / (Combined Mass).

Although this will systematically overestimate the true result by neglecting changes in acceleration as the fuel burns off. But then so do most games standard delta-v calculations - integral signs or even natural logarithms are said to scare off the customers.

The more the weight of your original ship was fuel, the larger the error. It's fine if you only had 5 or 10% fuel tankage to start with. If you were 90% fuel tank and using a formula with a mass ratio in it to compute your original delta-V, it could be off by quite a bit. You should recompute your mass ratio and stick it into the formula again instead.