Comment by ceejayoz

3 months ago

> Show civil engineers a river, tell them how much and what type of traffic needs to allow it, and they'll tell you it obviously can be done, they'll even tell you what structural elements will be needed and roughly how expensive they are.

Now ask them to do the Australia / Los Angeles one.

"lol no"

The where and the scale matter.

5 comments

ceejayoz

TeMPOraL 3 months ago

Where: Low Earth Orbit.

Scale: Lots of small satellites.

I.e. done to death and boring. Number of spacecraft does not affect the heat management of individual spacecraft.

Much like number of bridges you build around the world does not directly affect the amount of traffic on any individual one.

ceejayoz 3 months ago
> Where: Low Earth Orbit.
Challenging!
> Scale: Lots of small satellites.
So we're getting cheaper by ditching economies of scale?
There's a reason datacenters are ever-larger giant warehouses.
> Much like number of bridges you build around the world does not directly affect the amount of traffic on any individual one.
But there are places you don't build bridges. Because it's impractical.
- ben_w 3 months ago
  
  > Challenging!
  Thus, if launch costs to LEO reach $200/kg, then the cost of launch amortized over spacecraft lifetime could be roughly comparable to data center energy costs, on a per-kW basis.
  …
  If the [SpaceX] learning rate is sustained—which would require∼180 Starship launches/year—launch prices could fall to <$200/kg by∼2035.
  …
  Realizing these projected launch costs is of course dependent on SpaceX and other vendors achieving high rates of reuse with large, cost-effective launch vehicles such as Starship.
  > So we're getting cheaper by ditching economies of scale?
  The economy of scale here is count, not size. This is also why even data centres are made from many small identical parts, such as server racks, which are themselves made from many smaller identical parts.
  What makes LEO cheaper than it used to be, has been reuse. We'll see if "bigger" actually plays out as Starship continues.
  > But there are places you don't build bridges. Because it's impractical.
  What is and isn't practical changes as technology develops.
  Look, I am skeptical of space based beamed power and space based compute, but saying any given proposal must still be bad in 2035 because it would be bad with today's tech is like betting against the growth of EVs or PV in 2015, or against the internet in 1990.
  (The reverse mistake is to say that it must succeed, like anyone in 1970 who was expecting a manned Mars mission by 1980).
- TeMPOraL 3 months ago
  
  I humbly request 'dang to strike "read the damn article" off the list of guideline violations.

ben_w 3 months ago

> Now ask them to do the Australia / Los Angeles one.

> "lol no"

Given how many people dream of megastructures, I bet someone has this as an interview question, some variant of https://what-if.xkcd.com/160/ — I'd guess "a few trillion, tens of trillions of USD" for floating-bridges with anchors etc., but that's just my uninformed not-a-civil-engineer guess.