Drag-to-mass ratios for Duna aerobraking

[Ninety-Three]

I'm about to try my first mission that involves aerobraking on Duna, and since I don't want to figure out how to do the terminal velocity calculations myself, I thought I'd ask the forums: About how much parachute drag/ton do I need to safely land something on Duna? If someone has a rough sense, but no numbers, I'd appreciate even just a description like "A little bit less than on Kerbin". Also, because Duna's atmosphere is thinner, am I right in thinking that abruptly deploying parachutes are much less likely to tear themselves off the ship than they are on Kerbin?

[M5000]

I don't know of numbers, but this was a rover/skycrane/parachute system I had built for a Duna mission a while ago.

It used two large chutes and two drogues. The skycrane ended up not even being needed and actually caused more of a problem than anything..

I did use the drogues before deploying the main ones, Duna's atmosphere is a weird thickness. It's thinner than Kerbin but it's certainly thicker than you think at first..

I've also moved the thread to Help/How To where it should be

[Ruedii]

Generally I use one drogue chute and two main chutes for a small lander. The only reason I use that combination is there are radial drogue chutes yet.

For something heavier you probably want more power.

As of the aerobreaking altitude, if you take several passes, anything below 40,000 should be sufficient to reduce your speed.

[tavert]

I'm about to try my first mission that involves aerobraking on Duna, and since I don't want to figure out how to do the terminal velocity calculations myself, I thought I'd ask the forums: About how much parachute drag/ton do I need to safely land something on Duna? If someone has a rough sense, but no numbers, I'd appreciate even just a description like "A little bit less than on Kerbin". Also, because Duna's atmosphere is thinner, am I right in thinking that abruptly deploying parachutes are much less likely to tear themselves off the ship than they are on Kerbin?

Why no numbers? It's not that complicated, just plugging in some masses, density, gravity, and taking a square root. I posted the formula earlier tonight here http://forum.kerbalspaceprogram.com/showthread.php/31724-IF-i-use-parachutes-what-is-the-delta-v-required-for-a-Laytrhe-Landing?p=391610&viewfull=1#post391610

Your terminal velocity will be higher on Duna than on Kerbin, so you'll probably actually be moving faster if you deploy the chutes abruptly. Though there is less drag force involved, so hard to tell whether the jolt would overall be milder or worse.

The sturdiness of your lander design is an important variable here. What kind of landing speeds can you withstand? If you need a very low landing speed to survive, it may be best (depending on lander mass, planet and altitude you're landing at, and Isp of your engines) to do a powered landing, or a combination chutes-and-powered landing.

And note that aerobraking is a different thing entirely than landing with parachutes. Aerobraking is skimming through the upper atmosphere to reduce your speed from interplanetary velocities into a captured orbit (technically called aerocapture), or to slow down from a high eccentric orbit to a lower more circular orbit.

Edited May 26, 2013 by tavert

[M5000]

Your terminal velocity will be higher on Duna than on Kerbin, so you'll probably actually be moving faster if you deploy the chutes abruptly. Though there is less drag force involved, so hard to tell whether the jolt would overall be milder or worse.

This. This is the one thing you have to really think of when Duna-ing.