Prototypes of what the Spaceships jet engine is meant to represent, absolutely. But again we’re talking about chemical energy levels, not nuclear, being mixed with the outside air. In summary I’m not saying your approach is wrong but I don’t have a major problem with “5× cost” either.
Cost wasn’t as critical a concern most of the time because it was a military campaign, but broadly, yes – in particular it meant they were expensive enough that merchant shipping had to use antimatter-catalysed rather than antimatter-boosted hydrogen. (And therefore took multi-month trips across systems, which is interesting and leaves a niche for fast couriers.)
Let’s talk beanstalks. Because I like great fiery rockets, I am a recent convert to the idea. How does the beanstalk beat the fusion torch?
- the individual capsule is cheaper to build (doesn’t need precise aerodynamic shaping, expensive fusion drive, etc.) and operate (solar electricity plus a share of beanstalk maintenance).
- you can scale up the launch rate quite a long way without needing more runways, bold space pilots, traffic control, etc.
In W&S (GURPS TL11) a beanstalk is seen as the sign of a colony world that had “arrived”, that was a proper part of civilisation rather than somewhere primitive. But W&S doesn’t have divergent tech levels like Traveller, and every settled world is either part of or reasonably closely aligned with one of the eight or so big interstellar polities, so there’s some subsidy from the centre. Broadly I think the development stages might look like:
- outpost - research station, you come in, do your job and go away again.
- colony - this is your home, but it’s pretty basic. You have the high-tech gear that came on the colony ship, which includes a nanofac, so there’s plenty of stuff; but getting to and from orbit takes specialist hardware, messages off-world take a while to transmit, you probably don’t have a courier boat on station by the wormhole, and ships may not visit very often. Though I suspect the biggest part of feeling primitive is a low population: there’s nobody else to talk to about your obscure hobby.
- more successful colony - you have a beanstalk, so orbit is a permanent part of your world rather than a place only visited by specialists. (There’s an obvious incentive to start doing this before it really makes direct financial sense, because like a public transport system it enables other productive things to happen.)
- independent world - this is really only a financial shift, given the political realities imposed by large space navies, but it feels good.