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Pretty cool website and concept, but unfortunately mostly a delusional pipe dream until we develop fusion-based propulsion that makes orbital travel dirt cheap.

Pretty cool website and concept, but unfortunately mostly a delusional pipe dream until we develop fusion-based propulsion that makes orbital travel dirt cheap. Here's a good summary of why it's mostly pipe dreams at the current tech level: https://www.nasa.gov/mission_pages/station/expeditions/expedition30/tryanny.html https://www.nasa.gov/mission_pages/station/expeditions/exped...

JumpCrisscross 3y ago
> until we develop fusion-based propulsion that makes orbital travel dirt cheap…here's a good summary The tyranny of the rocket equation describes the exponential fuel cost of lifting propellant, with propellant, out of a gravity well. One workaround is non-propellant launch [1], e.g. an orbital rail gun. (Fusion propulsion is still tyrannical because you’re carrying your propellant.) The other is in-situ resource utilisation, i.e. not lifting out of a gravity well. [1] https://en.m.wikipedia.org/wiki/Non-rocket_spacelaunch https://en.m.wikipedia.org/wiki/Non-rocket_spacelaunch
- antisthenes 3y ago
  Ah, yes. The response that just hand-waves a bunch of really hard problems or invents tech that doesn't exist. I get it, HN has a lot of tech-optimists, but these responses are very tiring. Has there been legitimate significant progress on orbital guns or space elevators since 2012?
  - jandrese 3y ago
    Wasn't the "super cheap fusion launch" predicated on discovering a non-Newtonian rocket engine? As long as you're suffering under the third law the idea of a super cheap launch is a pipe dream. This is also why concepts of reaching distant solar systems by maintaining 1G of thrust for the entire trip don't work. Plug the numbers for that into the rocket equation and even with absurd ISP values it requires more mass than is available in our solar system for a trip to even just Proxima Centauri. The only maybe possible exception would be to pump so much energy into your reaction mass that it gains a significant amount of mass from relativity, but even that is engineering in the "it's probably easier to build a space elevator" realm.
  - JumpCrisscross 3y ago
    > response that just hand-waves a bunch of really hard problems or invents tech that doesn't exist The tyranny of the rocket equation is irrelevant to the problem of extraterrestrial manufacturing, at least in the short term. It’s all ISRU. > Has there been legitimate significant progress on orbital guns or space elevators since 2012 Actually, yes. I’m sceptical of SpinLaunch. But they are making real progress on the technology, even if they aren’t the ones to complete the package to orbital delivery.

JumpCrisscross 3y ago

> until we develop fusion-based propulsion that makes orbital travel dirt cheap…here's a good summary The tyranny of the rocket equation describes the exponential fuel cost of lifting propellant, with propellant, out of a gravity well. One workaround is non-propellant launch [1], e.g. an orbital rail gun. (Fusion propulsion is still tyrannical because you’re carrying your propellant.) The other is in-situ resource utilisation, i.e. not lifting out of a gravity well. [1] https://en.m.wikipedia.org/wiki/Non-rocket_spacelaunch https://en.m.wikipedia.org/wiki/Non-rocket_spacelaunch

antisthenes 3y ago
Ah, yes. The response that just hand-waves a bunch of really hard problems or invents tech that doesn't exist. I get it, HN has a lot of tech-optimists, but these responses are very tiring. Has there been legitimate significant progress on orbital guns or space elevators since 2012?
- jandrese 3y ago
  Wasn't the "super cheap fusion launch" predicated on discovering a non-Newtonian rocket engine? As long as you're suffering under the third law the idea of a super cheap launch is a pipe dream. This is also why concepts of reaching distant solar systems by maintaining 1G of thrust for the entire trip don't work. Plug the numbers for that into the rocket equation and even with absurd ISP values it requires more mass than is available in our solar system for a trip to even just Proxima Centauri. The only maybe possible exception would be to pump so much energy into your reaction mass that it gains a significant amount of mass from relativity, but even that is engineering in the "it's probably easier to build a space elevator" realm.
- JumpCrisscross 3y ago
  > response that just hand-waves a bunch of really hard problems or invents tech that doesn't exist The tyranny of the rocket equation is irrelevant to the problem of extraterrestrial manufacturing, at least in the short term. It’s all ISRU. > Has there been legitimate significant progress on orbital guns or space elevators since 2012 Actually, yes. I’m sceptical of SpinLaunch. But they are making real progress on the technology, even if they aren’t the ones to complete the package to orbital delivery.