Parachute issue on Duna

[Philoman]

Hi, I don't know if it's because I'm still a bit mad after my last fatal accident, which occured during re-entry in Duna's atmosphere, but there is something about the way it happened that have kept me thinking. I have landed several things on Duna before with the use of parachutes, of course, but this time the chutes ripped off of the command module when they deployed completely.

I suppose almost every KSP player has experienced this at some point, but why does it really happen? I try to think of all the elements with different values (compared to Kerbin) that when added up could lead to this accident. I'm thinking that the thinner atmoshpere will naturally lead to less braking before time of deployment. On the other hand, the gravity of Kerbin is significantly stronger than Duna's and thereby the initial speed you have when you enter the atmoshpere (I had an apoapsis of aprox. 100km) is much lower than it would be on Kerbin.

It should be mentioned that I did not make use of the drogue chute and that I had a periapsis of around 5km before hitting 42km. Is the relatively weak atmosphere really the factor here that dominates? Can't see what i did wrong.. other than not burning retrograde before deployment

[Vanamonde]

You do less aerobraking on the way to the altitude where the chutes trigger, and so it happens at a higher speed and is more violent, despite the thinner air. Generally, free falling on Kerbin gets you down to around 80m/s by the time the chutes open, whereas you're frequently going 300-500m/s when they deploy at Duna. (These are rough numbers based on experience, of course, and will vary by ship size and other factors.)

[Yalin Hawk]

^^ What he said. Duna's atmosphere really starts to grab (for what it's worth) around 6~8km. For maximum effectiveness, I would plan your landing in a very shallow aerobraking approach. Spend as much time as possible in that 6-8km band. Pop a drogue around 5km (thanks to the new tweakables) and once you're below 50-60 m/s you *should* be safe to pop your mains. Or, you can propulsively land with chutes just as an assisting system. My early career mode Duna-I landed mainly on chutes, but I needed to get my speed down below 100 m/s with the main engine before chute deployment.

[thereaverofdarkness]

Since Duna has less atmosphere, you can either try a longer aerobrakinng excursion or a dual-deceleration descent in which you use a combination of engine power and parachutes to bring you down safely. The second one is much easier if you have powerful lander engines and at least enough parachute for landing on Kerbin. Just wait for the air to slow you most of the way and when it's close to time for the parachute to deploy, use your engines to slow you down most of the rest, then deploy the chute with very little downward velocity. Let the parachute take you most of the way to the ground after that, and use the engine at the end for some extra stopping power since the air is thin. This method doesn't take much fuel or parachute, and is an effective compromise between only parachutes and only engines.

[Soda Popinski]

Adjust your periaps higher. Try 8 to 10 km. Otherwise you're going in too steep, hitting the dense atmosphere too quickly without shedding enough speed.

[Skorpychan]

It should be mentioned that I did not make use of the drogue chute and that I had a periapsis of around 5km before hitting 42km.

Well, THERE'S your problem! Shallower descent for more aerobraking, and USE A DROGUE CHUTE. Even partially deployed, a drogue chute does wonders for your speed. And since it fully deploys high up, you brake down to a speed with it that doesn't mean your regular chutes tear off.

Chute shock is a common thing unless you brake slowly. A drogue chute is the best way, with engine thrust a close second.

Also, I refer you to the parachute caluclator: http://ksp.freeiz.com/

Note how much a single drogue chute does to any lander.