TWR of parachutes?

[Sharpy]

...of course parachutes don't have thrust. But they have drag, that acts somewhat similarly.

Which parachutes offer the best ratio between their mass and braking force they provide? In particular, at higher speeds (200m/s or so) - I don't care much for going from 8 to 3m/s in this case.

Edited August 26, 2016 by Sharpy

[mhoram]

Infos about Parachutes can be found at the Parachute wiki page.

The best mass/braking force ratio can be attributed to the MK-16, MK16-XL and MK2-R. (EDIT: I stand corrected by RIC)

The other two so called "Drogue" parachutes have a worse ratio while fully deployed, but they can be used at much higher velocities (400-500 m/s) to slow down your craft.

Don't know, but maybe A.I.R.B.R.A.K.E.S is something, you would take into consideration.

Edited August 27, 2016 by mhoram

[Red Iron Crown]

Drag force changes with speed, so it's not quite as simple as a TWR calculation. However, area is a good first order approximation of comparative drag, so area-to-mass is a good metric for comparing them. By this measure, the Mk-2R radial chute offers the most area per unit mass, both when semi-deployed and fully deployed.

[mhoram]

I made some tests with the different parachutes in the following setting:

- Mass of the vessel: 6.64 ton
- The number of parachutes is chosen so that 0.6 ton of mass is reached for each parachute type
- Deployment of the parachutes at a higher altitude so that at 500m altitude an equilibrium for the velocity is reached

And the results are:

Parachute	# of Parachutes	Velocity at 500m altitude
Mk16-XL	2 (300kg)	8.4 m/s
Mk2-R	6 (100kg)	4.0 m/s
Mk25	3 (200kg)	50.2 m/s
Mk12-R	8 (75kg)	27.0 m/s
Mk16	6 (100kg)	6.5 m/s

It looks like the radially mounted parachutes perform much better (masswise) than the others.

Imgur Album

 

Edited August 27, 2016 by mhoram

[Sharpy]

@mhoram Awesome job! Thank you!