Mr Awe wrote:
^ Did you think it just might be possible that Mr Sweet helped with that rocket?
Although, I have to admit that whatever benefits he provided to the symbiotic relationship was left vague.
Of course I did, but as you note, his contribution was undefined. And, given the history noted by Madam Vastra, I think JoeZhang is right to question what rocketry experience he'd bring to the relationship. It's a question someone should have been asking.
Apparently I missed the part where they explained that Mrs G was a chemist and engineer! I just assumed that Mr Sweet was supplying some information, but perhaps not. However, if his kind has been around since the Silurians, and they developed rockets, the information could well have been passed down. "His" capabilities and contributions were left vague.
However, for any implausability of such a rocket at that time, I'd put down to Mr. S! It's a viable explanation for the early rocketry.
ETA: I see that Aldijor beat me to it about the Silurian's, but that was my though during the show.