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In the SpaceX video Starship | Earth to Earth they show the flight time from Hong Kong to Singapore to be 22 minutes.

What's taking so long? It's only 4 hours by airplane (and US $275!)

Hong Kong to Singapore maps.google.com

SpaceX video screenshot Starship | Earth to Earth

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    $\begingroup$ Man does not like large accelerations. From this he can die. If you launch a nuclear warhead, it will be faster. $\endgroup$ – A. Rumlin Dec 19 '20 at 11:34
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    $\begingroup$ An LEO ground track of 2500 km takes roughly 6 minutes to pass over. Any ballistic trajectory over Earth that connects two points 2500 km apart will take longer than that to fly, and on top of that, Starship will have to deal with atmosphere on the way up and down. $\endgroup$ – notovny Dec 19 '20 at 13:27
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    $\begingroup$ We can easily say that the times given are consistent: i.stack.imgur.com/yIlO0.png It seems there are two different flight profiles for short and long distance travel though. 0km distance takes about 17 minutes and half-way around Earth takes 57 minutes. $\endgroup$ – asdfex Dec 19 '20 at 18:10
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    $\begingroup$ The average speed would be ~2000 m/s, nearly mach 6; the acceleration phase would eat up about 3 minutes. Given how long it takes to get to your local aerospaceport and get through the security line, Amdahl's law makes it fairly pointless to go any faster. $\endgroup$ – Russell Borogove Dec 19 '20 at 22:57
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    $\begingroup$ @uhoh, Not from my side. The time-of-flight calculation for these trajectories is too ugly. $\endgroup$ – asdfex Dec 21 '20 at 8:50
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We could compare this to the aborted launch of the Soyuz in 2018.

https://en.wikipedia.org/wiki/Soyuz_MS-10

The abort occurred at an altitude of approximately 50 kilometres (31 miles); the spacecraft reached an apogee of 93 km (58 mi) then landed 19 minutes and 41 seconds after launch. At 08:55 UTC the search and rescue team was deployed to recover the crew and the spacecraft, which had landed 402 kilometres (250 mi) from the launch site.

So the Soyuz had an emergency separation at 50 km, and this resulted in "only" 402 km of distance covered in 19 minutes. The Starship would still be accelerating past the 50 km, so it's reasonable that in about the same time (22 minutes) and if assume a similar apogee of around 100 km it would cover more distance - 2,600 km (the distance between Singapore and Hong Kong). And if one might argue that the Soyuz took so long because it was slowly landing, this seems to be countered by the fact that "the crew experienced about six to seven times Earth's gravity".

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    $\begingroup$ That section begins "A few minutes after liftoff... the crew reported feeling weightless, and mission control declared a booster had failed." So for most of the 19 minutes the trajectory was unpowered and by a capsule designed to slow down. I'm not sure this is a good model. $\endgroup$ – uhoh Dec 19 '20 at 23:40
  • $\begingroup$ @uhoh Weightlessness always occurs as soon as the engines stop working. Further free fall until the brake system is turned on (engines or parachutes). Rocket engines will not run for 22 minutes. $\endgroup$ – A. Rumlin Dec 20 '20 at 8:48
  • $\begingroup$ @A.Rumlin yes all we have to go on from that particular passage in Wikipedia at least is the definition of "A few minutes", but I think that when the engine shut down it was a lot earlier in the flight and they were going a lot slower and not at the same angle of attack as a SpaceX passenger ship when released into a suborbital trajectory destined to Singapore, so "I'm not sure this is a good model." $\endgroup$ – uhoh Dec 20 '20 at 9:18
  • $\begingroup$ The main problem here is that Soyuz obviously wasn't on an optimized (neither time nor energy) trajectory to this 402km distant target. You can take arbitrarily long to any destination by increasing the elliptical orbit up to infinity. $\endgroup$ – asdfex Dec 20 '20 at 9:21

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