4 ms·

Once you get out of the atmosphere, drag (and fuel consumption) is ~0. So theoretically possible, but I'm not sure if that's what he was talking about. Certainl

Once you get out of the atmosphere, drag (and fuel consumption) is ~0. So theoretically possible, but I'm not sure if that's what he was talking about. Certainly Overture won't be capable of that.

hnuser123456 2y ago
Fair, I hadn't considered the intercontinental ballistic passenger missile approach.
- dylan604 2y ago
  Isn't that specifically one of the types of travel predicted to be made possible by reusable rockets capable of landing on the ground? From Florida to Japan in 45 minutes type of thing
  - adastra22 2y ago
    Yes point to point travel was a market for Starship. I think they’ve mostly backed off that though, as Starlink offers an easier market opportunity and just as much revenue potential. The supersonic plane would have advantages over the rocket approach though. Rockers require long, inconvenient transfers to offshore launch facilities. (But would have the selling point of a microgravity transit.)
  - notahacker 2y ago
    Reaction Engines in the UK spent over 35 years working mostly on that concept (though when they eventually went bust trying to scale up last year I think they were focused on reusable space launch business model which is ironically more realistic)
    - ballooney 2y ago
      No, they were working on the latter (skylon) most of the time, though the new management that came in after their £60M investment quickly dropped SSTO in favour of more immediate RoI applications. The passenger plane was LAPCAT which was a paper study commissioned by the EU. They did some interesting real work too, such as designing and testing a hypersonic engine combustion chamber that could reduce NOx emissions, which would be a big problem in any ‘conventional’ (eg scramjet) hypersonic engine.
- blinding-streak 2y ago
  ICPM! That's a new acronym you just coined!
- pfdietz 2y ago
  > Fair, I hadn't considered the intercontinental ballistic passenger missile approach. The terminal deceleration on an ICBM trajectory would be lethal. Ballistic passenger transport at global distances has to be almost orbital so the entry is sufficiently shallow.
mppm 2y ago
Once you get out of the atmosphere, lift is ~0 too.
- Ajedi32 2y ago
  If you're going fast enough, you don't need lift. But judging by "in four hours" I'm guessing he's imagining something somewhere in between those two extremes. High enough to substantially reduce drag, low enough that you don't need to approach orbital velocity to maintain altitude.
  - mppm 2y ago
    "Fast enough" is very nearly orbital speed, though. Suborbital range is very short on the lower end, and increases rapidly and nonlinearly later. E.g. if you can boost to 2km/s (~ Mach 7), this gives you, I kid you not, around 200km of ballistic range. It's either atmospheric flight or orbital flight, and there's nothing really useful in between.
    - adastra22 2y ago
      GP is not talking about a ballistic trajectory though.
    - pfdietz 2y ago
      One possibility is a trajectory that's a series of skips.
- jjk166 2y ago
  There actually is still significant lift. We define the edge of the atmosphere to be where the lift to drag ratio of a plane would be less than 1 below orbital velocity (ie if you were going fast enough to lift your weight with conventional wings you'd be in orbit), so you can't fly conventionally in space but lift might still be generating a force which is significant compared to your craft's weight.
  - echoangle 2y ago

Once you get out of the atmosphere, drag (and fuel consumption) is ~0. So theoretically possible, but I'm not sure if that's what he was talking about. Certainly Overture won't be capable of that.

hnuser123456 2y ago

Fair, I hadn't considered the intercontinental ballistic passenger missile approach.

dylan604 2y ago
Isn't that specifically one of the types of travel predicted to be made possible by reusable rockets capable of landing on the ground? From Florida to Japan in 45 minutes type of thing
- adastra22 2y ago
  Yes point to point travel was a market for Starship. I think they’ve mostly backed off that though, as Starlink offers an easier market opportunity and just as much revenue potential. The supersonic plane would have advantages over the rocket approach though. Rockers require long, inconvenient transfers to offshore launch facilities. (But would have the selling point of a microgravity transit.)
- notahacker 2y ago
  Reaction Engines in the UK spent over 35 years working mostly on that concept (though when they eventually went bust trying to scale up last year I think they were focused on reusable space launch business model which is ironically more realistic)
  - ballooney 2y ago
    No, they were working on the latter (skylon) most of the time, though the new management that came in after their £60M investment quickly dropped SSTO in favour of more immediate RoI applications. The passenger plane was LAPCAT which was a paper study commissioned by the EU. They did some interesting real work too, such as designing and testing a hypersonic engine combustion chamber that could reduce NOx emissions, which would be a big problem in any ‘conventional’ (eg scramjet) hypersonic engine.
blinding-streak 2y ago
ICPM! That's a new acronym you just coined!
pfdietz 2y ago
> Fair, I hadn't considered the intercontinental ballistic passenger missile approach. The terminal deceleration on an ICBM trajectory would be lethal. Ballistic passenger transport at global distances has to be almost orbital so the entry is sufficiently shallow.

mppm 2y ago

Once you get out of the atmosphere, lift is ~0 too.

Ajedi32 2y ago
If you're going fast enough, you don't need lift. But judging by "in four hours" I'm guessing he's imagining something somewhere in between those two extremes. High enough to substantially reduce drag, low enough that you don't need to approach orbital velocity to maintain altitude.
- mppm 2y ago
  "Fast enough" is very nearly orbital speed, though. Suborbital range is very short on the lower end, and increases rapidly and nonlinearly later. E.g. if you can boost to 2km/s (~ Mach 7), this gives you, I kid you not, around 200km of ballistic range. It's either atmospheric flight or orbital flight, and there's nothing really useful in between.
  - adastra22 2y ago
    GP is not talking about a ballistic trajectory though.
  - pfdietz 2y ago
    One possibility is a trajectory that's a series of skips.
jjk166 2y ago
There actually is still significant lift. We define the edge of the atmosphere to be where the lift to drag ratio of a plane would be less than 1 below orbital velocity (ie if you were going fast enough to lift your weight with conventional wings you'd be in orbit), so you can't fly conventionally in space but lift might still be generating a force which is significant compared to your craft's weight.
- echoangle 2y ago