Originally posted by Tom Kalbfus:
Objection 1: You need fantastic materials to hold the ringworld in place.
Objection 1' (1 Prime): making cables, even out of steel, to the size and specifications required
would be an engineering feat bordering on magical. At the very least, you'd need orbital production facilities and the ability to move
really big pieces of steel over very long distances.
Objection 2': what you propose is more complicated mechanically than the Niven design, hence more likely to fail over the
geologic lifetime of an artifact such as the ringworld. You have set the system up in such a way that you guarantee eventual catastrophic failure, unless you commit to a maintenance program on a massive scale, spanning tens of thousands (or maybe even millions) of years. It will also require a lot more material, most of it heavy elements which are more scarce. Though he doesn't come out and say this, Niven implies that the Pak were able to manipulate substances at the atomic level, which means you could even tease scrith out of lighter, more common elements such as H or He.
Objection 3': The Niven design, once built, needs only energy input from the star it encircles. The star provides light and heat to drive the ringworld's ecological carbon cycle. The star also provides fuel, in the form of cast off hydrogen "wind" for the ringworld's Brussard station-keeping jets. Being a much
simpler design overall, there's less to go wrong, hence fewer opportunities for catastrophic failure over the geologic lifetime of the artifact.
Once "spun up", Niven's ringworld maintains a constant velocity because nothing is left in the system, besides the star, to slow it down. (Niven didn't deal with interstellar dust clouds, etc. and their effect on an object as massive as the ringworld would probably be negligable). That's why he makes a point of stating that the ringworld system was empty except for the structure and its star. You either need to start with a star that never developed a planetary accretion disk or one in which the builders removed everything else. So all that the ringworld needs is light and heat for its ecosystem and a minimal amount of "fuel" for station keeping.
Your ropeworld will need constant input of energy sufficient to create the maglev effect between the rope structure and the ringworld, proper. Do you get that from the star? If so, how? And how do you spin the maglev track up to speed? Oh yeah, how do you make cables that massive out of tungsten? Isn't it one of the more difficult metals to work with?
I ask because you've said that "maglev" is the only superscience involved here and I think that the ability to completely clear a planetary system, build a structure the size of a rope/ringworld and then accelerate it to greater than orbital velocity is a
leetle beyond what we can do now.
Objection 4': You've envisioned your ropeworld as a structure which is pulled rigid by gravity, but that assumes the ropeworld would be
stationary in space!
An object stays in orbit around a star because it's angular momentum equals the gravitational force exherted by the star. Your ropeworld isn't moving and it's centre of gravity overlaps the star's center of gravity. So what holds it in place?
Niven's ringworld spins faster than orbital velocity, which counteracts the star's gravitational pull. That's why in
Ringworld Engineers Niven had to explain the presence (or lack thereof) of attitude jets along the rimwall. Your design doesn't address this problem and your "ring" of cables would eventually drift off-center until it contacted the star.
So you see no tech magic is required except fot magnetic levitation.
You've proposed a design which assumes all of the complexity of desigining and building a massive, unstable structure, but none of the simplicity which would be required to allow this structure to survive for a long period of time. Niven's idea is better than yours because, magic tech aside, it's
simpler and less prone to catastrophic failure.
