Freighter thoughts

my son had the following thoughts about FTL freighters:

A freighter with a jump drive must use 10% of its mass for drive and an
aditional 5% of its mass is for a thrust one drive. Plus to make it
worse 10% of your mass must be hull. This means that a freighter can at
best only devote 75% of its total mass to cargo. Now this seems like a
huge ammount but when compared to the 90 or so percent a modern oil
tanker or bulk frighter gets it makes an FTL frighter uneconmical for
any sort of low value goods as the ship is going to have to make
something like 100 trips to pay itself off. By this time its likly to
have broken down. So if you have intersteller trade it must be all non
perishable high value goods.

posted for Matt
by
andy