Speculative equations that were wrong?

[Maximum7]

I just read that a Rod from God or Kinetic Kill Vehicle may not be as destructive as science fiction predicted it would be. Are there any speculative things that have been decided to not work as we think we would?

[40lightyears]

There exist several experimental cases to illustrate these points. The physiological energy reaction known as cold fusion proved promising in the late 1980s until scientists failed to validate the original proposed mechanism. Current technology requires impractical amounts of energy for the proposed method of faster-than-light travel with warp drives. Scientists label this development more fictional than real. Cool imaginative concepts fail to reach the expectations many people had envisioned.

[FuturismFan]

- Carbon nanotubes might be just like asbestos. https://pmc.ncbi.nlm.nih.gov/articles/PMC9145953/

- Room temperature superconductors would be pretty useless unless they are metallic, since otherwise you wouldn’t be able make wires out of them. https://www.youtube.com/watch?v=p3hubvTsf3Y

- Solar roadways

- Vactrains (aka the Hyperloop)

- The Space Shuttle was originally thought to be as simple to operate as an airliner. Rapidly reusable spacecraft were thought to be easy to make, but it turns out that they have been much more difficult to develop than originally thought. https://en.wikipedia.org/wiki/Criticism ... le_program

- Resurrecting the mammoth (and other extinct animals): sadly it wouldn’t really be a mammoth, it would technically just be a genetically engineered elephant. Colossal Biosciences admits that they will only be producing cold-resistant Asian elephants. https://gizmodo.com/colossal-bioscience ... 1851312096

- Project Excalibur and the Boeing YAL-1 were both failures.

[Jakob]

I just read that a Rod from God or Kinetic Kill Vehicle may not be as destructive as science fiction predicted it would be. Are there any speculative things that have been decided to not work as we think we would?

I've actually found an alternative in Fight for Hope. Basically a nuclear explosion is used to propel the rods instead of just dropping them, allowing them to reach speeds approaching 100 km/s, allowing them to impact with a force of around 2 kilotons instead of a paltry few tons. It's basically like a reversed Project Plumbbob. What's the use of this instead of just using a nuke? One, there's no warning whatsoever, no time for laser defenses to engage, which is useful if the enemy has laser defenses or if you think they do. Two, instead of using one rod, you can use a ton of carefully aimed nuclear shot to precisely distribute the force of a nuke and wipe out enemy assets while leaving your own untouched (the Kyanah like doing this, for various technical and cultural reasons).