Calculating The Capabilities Of A Parachute

[The Flying Kerbal]

Hey guys!

A simple question this time: is there any way of calculating the impact speed of an object using a Mk16 parachute to land on Duna (or indeed any planet)?

This is what I'm hoping to drop on the red planet.  I've done something similar before, but this one has exchanged drogue chutes for extra solar panels.

Thanks, everyone.

[4x4cheesecake]

I don't know how the drag is calculated in KSP, so I cannot tell you if it is possible to do it on your own...but you can use a mod for it

Switch to the 'parachutes' window via the arrow buttons at the top, click on 'Kerbin' to change it to 'Duna', 'Eve', 'Jool' or 'Laythe' (or sun xD) and you will see the velocity of your Vessel at a given altitude. You can even increase the altitude by clicking on the '0 m' behind 'touchdown' which will open a slider

[OhioBob]

A vessel should fall about 1.65 times faster on Duna than it will on Kerbin.

The equation for terminal velocity is,

V_t = SQRT( (2mg)/(ρAC_d) )

m, A and C_d are all characteristics of the vessel and parachute, so if we assume those are the same regardless of where we are, we can delete those terms and simply say

V_t ∝ SQRT(g / ρ)

That is, terminal velocity is proportional to SQRT(surface gravity / air density).

Duna's surface gravity is 0.3 times Kerbin, and it's air density at the surface is about 0.11 times Kerbin.  Therefore,

V_t_duna / V_t_kerbin = SQRT(0.3/0.11) = 1.65

So just test it on Kerbin and then you can compute what it will be on Duna.
 

Edited July 25, 2018 by OhioBob