Comment by m4rtink
10 hours ago
90 minutes is a full low Earth orbit cycle. For a suborbital hop it should be about half of that at maximum for any 2 points on Earth.
10 hours ago
90 minutes is a full low Earth orbit cycle. For a suborbital hop it should be about half of that at maximum for any 2 points on Earth.
I didn't initially believe these numbers, but if you look at some real life stats, you are probably right.
Nominal SECO for the last starship mission was at ~8 minutes and it took ~20 minutes from deceleration started (well, from air resistance outweighed the forces of acceleration) to landing. So basically 30 minutes of flight is just the "getting up to speed" and "slowing down" part. Both account for some distance traveled, but still. ~45 minutes is probably a good bet.
Do note however that you may have to go around the world "the wrong way" to get some places due to launch constraints. But living in a world where going around the world "the wrong way" is the easier path is interesting. Imagine that.
90 minutes is a low earth orbit period.
A suborbital craft won’t be travelling at that speed.
Like, you could do a partial orbit & then drop down over the destination. But it would need much more delta-v & an orbital class heat shield.
It was proposed as nuclear warhead delivery method though: https://en.wikipedia.org/wiki/Fractional_Orbital_Bombardment...
Unless a suborbital trip is nearly at orbital velocity, it will involve a high, arcing trajectory. This will make the deceleration at the end unacceptably (lethally) high for all but short arcs. Some of the Mercury suborbital missions involved deceleration of 15 gees, if I recall correctly.
That was only an issue because they were fired pretty much straight up; They only went 500km down range.
You can also reduce peek deceleration forces by using aerodynamic lift to stretch out the reentry over a longer period.
1 reply →
If the capsule/rocketplane has some lift & preferably steerable aerosurfaces then you can compensate the purely ballistic deceleration somewhat.
But yeah, if it is going down almost vertically then this will not be enough.
1 reply →