On 14 Feb 2016 at 19:04, Craig Berry wrote:

> Exactly. If you want to handwave it, you can couple it to the
> volume-based nature of the jump bubble version of jump H2 usage.
> There's a threshold at 100dt below which you can't form a reliably
> stable jump bubble around a craft.

So far as I'm concerned, you're welcome to put a jump drive in a vessel that's under
100 DTons. However, the drive can't be smaller than 2 DTons (nobody has managed to
make a smaller one that works), and it will always consume at least 10 DTons of H2 per
parsec of jump. That is to say, your jump drive and fuel are as if the ship was 100
DTons if it's smaller than that.

For my current game I use GURPS Spaceships plus houserules for ship design, but the
same principle applies.