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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?

  • By the way: I just updated the wiki article and removed that no longer meaningful table. – Philipp Aug 25 '15 at 13:27
  • @Philipp I thought about doing the same thing, but I think we should keep the table while adding a note about the fact it only works with KSP < 1.0. – A.L Aug 25 '15 at 13:30
  • Any discussions about the wiki should be done on the wiki, not here. – Philipp Aug 25 '15 at 13:32
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    important note about terminal velocity on ascent in 1.0.4: It doesn't matter. It rises so quickly with altitude that you need truly insane TWR, something of order of 10 or more, to ever catch up with it on ascent in a standard gravity turn (which you can now start some 500m above the landing pad!). So for all practical purposes, you just don't need that table anymore. You can use "atmospheric efficiency" of Kerbal Engineer Report to see if you exceed it currently - but you'll need to try really hard to see it climb above the "optimal" 100%. – SF. Aug 26 '15 at 16:41
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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.

  • I thought the terminal velocity in the original table was calculated, was I wrong? Did it came from experiments? If I create a rocket with nose cones and other aerodynamic parts, it is impossible to calculate the terminal velocity like in the above table? Is the table from the wiki totally wrong or relatively close to the real values? – A.L Aug 25 '15 at 12:43
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    @A.L. The table was calculated, but back then calculating it was easy because the drag was always exactly proportional to the mass of the rocket. It was completely irrelevant how you arranged the parts and how you oriented it. With the new aerodynamics model the drag depends on shape and orientation of the rocket which is different depending on how you build and fly your rocket. – Philipp Aug 25 '15 at 12:54
  • Let's imagine that we create a tool with contain drag values for nose cones and other parts exposed to airflow, is it sufficient to estimate terminal velocity with a calculus like 1 big nose + 2 big nose → drag value → terminal velocity? – A.L Aug 25 '15 at 13:06
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    No, because the amount of drag on your ship is dependant on much more than just the drag of the leading parts. – MBraedley Aug 25 '15 at 13:10
  • @A.L. Mass is also a relevant variable. A sheet of paper falls slower than a sheet of metal, even though they have the same shape. This is further complicated by the fact that your rockets mass changes during flight. – Philipp Aug 25 '15 at 13:14

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