Parachute help?

[Will_hynes]

Hello all, I have a question about parachutes and atmospheric planets. Whats the highest speed you can go before a deployed parachute rips off? So when iI'm landing on Duna, I'll know when its safe to use my parachutes to save fuel.

[draeath]

I thought the parachutes will stay stowed at low pressure, deploy at moderate pressure, and finally fully envelope near the ground? You'd want to deploy them as early as possible?

[Will_hynes]

Yeah but if you're going to fast, they'll break. So i want to know how fast you can go BEFORE they break.

[Monkster]

I would like to quote what draeath said and agree but I could be quoted on that I think that is correct though like I said before, don't quote me on it

Edit: Ah that's what you meant, like trbinsc says below, it's all to do with what they're attached to and the strength values of that object.

Edited September 30, 2012 by Monkster

[trbinsc]

It depends what the're attached to.

[EndlessWaves]

They're easy to break if you deploy them going fast but given they don't have that much more drag when semi-deployed (0.22>1>500) I'd be surprised if it was that easy to rip off an already deployed chute.

As it's atmospheric drag that rips them off, the highest speed will depend on the atmospheric thickness so there won't be a simple answer even if someone does know the equations used to calculate it.

I would think you can safely deploy in space if you're descending from orbit but if you're aerobraking from an interplanetary transfer it may be worth waiting until you've shed most of your speed and/or pick a trajectory that takes you back above the atmosphere so you can deploy and re-enter at suborbital speeds.

[Will_hynes]

Alright, I just landed on Duna, (in two attempts). First attempt: I got to the fully open parachute altitude wile traveling 200 m/s, the upper half of my lander (Pod and ASAS) seperated from the rest. Second attempt: This time i came in at 150 m/s and my parachutes deployed perfectly. In other words, I just answered my own question...

[draeath]

Mass is important too. A lighter vehicle can be going faster when the chute deploys, since it doesn't yank on the parachute so hard. Drop everything useless (spent tanks and engines, etc) before you use em, and you're more likely to have a successful deployment.

[stargazer1235]

Placement of the parachutes is important. Having the chutes too high up the will the capsule to break off at high speed. This was the problem with my first lander.

[SyX]

I have experimented with this fairly extensively. The most simple answer is: the more mass you have per parachute, the slower you need to be.

You can counteract this by using struts to anchor the parachute to the ship better and spread the force.

[Khiro]

All the above things seem to be correct. The mass it is trying to slow down X the speed you're going at = the force of your momentum. That is countered by the drag value of the chute, the thickness of the atmosphere, and the shear strength of the parachute part. You can reduce the force of your momentum by aerobraking and retro-thrusting, and burning off fuel reduces your mass as well. On the other side of the equation you can reinforce your chutes with struts, or you can add additional chutes to distribute the force.

When I'm developing vehicles, at some point I'll inevitably launch the re-entry portion up about 100K, let it fall back to Kerbin, and see what the chutes do. You get used to the needed values for the command pods pretty quickly, but if you're trying to chute-land a lander vehicle, testing is in order. As far as the atmospheres of other planets, napkin calculations based on their relative densities is probably your best bet.

[The Destroyer]

It depends on mass. they will genereally rip off at 100 m/s at 500m, however in the "drag chute" mode, they should not rip offf.

[Ghery88]

In my experiences 8 smaller parachutes (which are stronger than the big one) can be safely deployed on a 60-ton craft between 100 and 120 m/s. If you have the roughly 500m fall at that point, only minimal thrust is required to achieve a safe landing.

[hjalfi]

I've found that if I connect the parachute directly to the capsule it's much less likely to break off. Putting a ASAS between the capsule and the parachute generally didn't work.

Many kerbals died to bring you this information.