• 0 Posts
  • 17 Comments
Joined 1 year ago
cake
Cake day: June 25th, 2023

help-circle



  • I’m wondering if the remaining fuel in the lower segments of the ship gave those sections more momentum, causing the whole hull to pivot around those heavier sections (especially with the loss of thruster capability being discussed).

    With the Space Shuttle, this tendency was largely offset by the delta wings also causing greatly increased drag at the rear of the hull, but with fins folded the Starship doesn’t really have this. That plus the seeming loss of control due to thruster malfunction…






  • Like the other comment says, concrete is rocks of various sizes (called “aggregate”) mixed with a cement and other additives to change its particular properties.

    The cement is the really important point, because once water is added to the cement, it undergoes a chemical reaction which hardens it. Saying cement “dries” isn’t quite correct - yes, it stops being wet, but some of the water actually ends up incorporated into the molecules of the final cement. This is also why cement is really hard to recycle - you have to undo that chemical reaction, as opposed to asphalt which stays the same material.

    Fun fact: When concrete is mixed at a big plant, it begins curing immediately. Concrete being carried in those big mixer trucks needs to be delivered before it cures in the truck!



  • Specifically talking about asphalt vs. concrete:

    • Asphalt is relatively cheap vs. concrete. This is partly because asphalt is a whole lot easier to recycle than concrete, which is almost un-recyclable, but also because asphalt is a relatively “simple” material - it’s mostly petroleum byproducts and gravel.

    • Concrete doesn’t grip very well, compared to the relatively textured surface of asphalt. Especially when wet! This is why you often see concrete formed with “ridges” or “bumps” cast into it. However…

    • This also makes concrete noisier and bumpier to drive over, making drivers less happy. It’s why it’s often used for short, low-speed uses like driveways, parking lots, or side streets.

    Just about the only thing concrete has going for it is it’s endurance, which it definitely wins handily.

    Every few years another engineered road solution is conceived - I’ve seen variations that would use glass which could be ‘re-fused’, concepts for recycling plastic waste, and many more. Most of these run into the issue that they’re either less ‘grippy’, or that they simply cost more even accounting for the longer lifespan.






  • So by all means correct me if I’m wrong, but is this really that bad?

    Like, people always freak out about “turning one falling object into many” because they would still share the same collective kinetic energy, but smaller objects are far more likely to burn up high in the atmosphere rather than penetrate for a destructive impact.

    The article describes 37 boulders, each with a ~15kT kinetic energy. We have record of meteor events in this magnitude, and they aren’t terribly destructive. Nor is it more than a footnote in terms of Earth’s daily total energy budget; the Earth isn’t going to be cooked by a meteor-swarm of this scale.

    It’d seem to me that the biggest risk would actually be peppering Earth’s orbital region with far smaller objects that could still damage satellites, no?