Terminal velocity table for KSP v1.0 and later?
The KSP wiki presents an interesting table of terminal velocity in Kerbin’s atmosphere preceded by an useful advice:
Note: this table is useless with KSP version 1.0 and later, see the explanation in the answer below.
You can save fuel by being close to your terminal velocity during ascent. Lower velocity wastes delta-V on gravity, higher is wasted on air resistance:
| Altitude (m) | Approx. terminal velocity (m/s) | |--------------|------------------------------------| | 500 | 105 | | 1,000 | 110 | | 2,000 | 120 | | 3,000 | 130 | | 5,000 | 160 | | 6,000 | 180 | | 7,000 | 200 | | 8,000 | 220 | | 10,000 | 260 (remember to start your turn!) | | 13,000 | 350 | | 15,000 | 425 | | 16,000 | 470 | | 32,000 | 2250 |
But this table is more than a year old, it doesn’t take into account the new Aerodynamics features added with version 1.0 (released on April 27th, 2015). I’m looking for an updated version of this table for KSP v1.0 and later.
According to Philipp:
With the new aerodynamic model, determining the optimal and maximum speed for a given altitude are quite non-trivial because it greatly depends on how aerodynamic the vessel is as a whole. Also, the orientation of the vessel now matters.
Source: How fast should I be going through Kerbin’s atmosphere during launch?.
you will have a hard time getting even close to terminal velocity in most flight phases. So just go for maximum thrust.
Source: What role does terminal velocity play in a rocket launch?
Does non-trivial means impossible? Can terminal velocity can still be estimated for a common spaceship?
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Can terminal velocity can still be estimated for a common spaceship?
It can be found out experimentally.
The terminal velocity of an object is the speed it reaches during freefall. So when you drop the rocket from orbit top-first you can observe the terminal velocity at different speeds.
Launch your rocket, but don’t decouple the first stage. Let it continue on its sub-orbital trajectory. After reaching the apoapsis, turn the rocket so the top always faces the prograde direction and observe the falling speed at different heights. When it impacts the ground, revert the flight to vehicle assembly.
During the fall it is important that you mimic the orientation during ascent. A rocket which flies/falls sideways has a higher aerodynamic drag and thus a lower terminal velocity than one which flies straight.
Real-life engineers in the early days of space exploration used wind tunnel tests to optimize the atmospheric drag of their rockets. Today, computer simulations are used.