Re: Paper rocket
It must be a right bugger getting all the power / size / weight / redundency trade-offs "right" on these things. For a given value of right, as there's no correct answer. Then for all the different instrument teams to come back saying can they please just have a bit more. Then after months of back and forward with that, you go to a funding committee who tell you to change everything as you're now going on a different rocket with more/less payload. Or to build that bit in this other country/constituency. Or that they want it all painted purple and shaped like Barney the dinosaur...
OK, that last one probably hasn't ever happened.
It certainly make the kind of engineering I do look bloody easy. Which, to be fair, it is. Otherwise I wouldn't be doing it. Plus, if I do screw up, I can apologise humbly, run the calcs again, and we can send an engineer round to replace the part with the right one. Our service engineer call-outs start at about £300, less outside central London, not sure what it is once you go past the asteroid belt.
I did once try to sell a pink water storage tank for a bet, but failed. Never any purple ones.