Chutes over Duna

[ohlookabirdie]

So i'm trying to land a rover to refuel my lander so i can get Jeb home. all was going well until the landing, it was way too fast. the chutes deployed (5 of them) but didn't deply fully before making a streak of rubble across Duna's Southern Ice Sheets.

are chutes not going to be enough or did they not deploy because i was going to fast?

any ideas?

[Xephirious]

Deploy those chutes soon as you're in the atmosphere, they will work to slow you from orbital velocities with the drag from the atmosphere to get you to terminal velocity quicker. It's a thin atmosphere so depending on your lander's weight, you may to have a partially powered descent to achieve "soft landing".

[Soda Popinski]

Probably a moot point, since you need to labd near Jeb, but I suggest landing in a valley or plains area. Lots of mountains means thinner atmosphere up high. Bad for aerobraking and chutes.

[Liowen]

Depending on the weight you are dropping to the surface as well you may need more chutes. I would use 4 drogue chutes (orange tops) and some of the square radials (I normally put 8 of them on even light crafts). While some will say to use the engines to land, personally I have not needed to use the throttle on my 2 crafts I set on Duna for more than a second or 2 max as I come in around 6.5m/s. I am far from an expert on landing there though and all stated information is from my personal experiences, hopefully it helps some.

[maltesh]

With Duna, dependent on your design, and your landing location, it may behoove you to drop directly down instead of doing a long aerobrake when landing on chutes.

Because of the way chutes work in KSP, if there's enough atmosphere to partially deploy chutes, the regular chutes will fully-deploy at exactly 500m above the surface regardless of where you are. Full chute deployment doesn't care about local atmospheric pressure in the game as it is.

If you're coming in at a shallow aerobrake over Duna, variations in the terrain when you're moving horizontally at several hundred meters per second and low over the surface can result in the ground rising up to smack you before the chutes realize that they should have fully opened.

It's one of a few reasons that I started designing my chutelanders to drop straight down from up to 600 km over Duna.

[strongest_2hu]

It's one of a few reasons that I started designing my chutelanders to drop straight down from up to 600 km over Duna.

If you have the fuel and engines for a stop-and-drop, couldn't you just aerobrake to a powered landing? I don't see the point of landing with parachutes if you're still going to waste all that fuel by stopping your motion about the planet first.

[capi3101]

There was a good site at http://ksp.freeiz.com/ that would calculate the number of chutes you would need for a certain set of parameters. It appears to be non-functional today (either that or Chrome's just being persnickety).

You need to hit the button to deploy your chutes early on Duna and burn like mad to get your speed below 100 m/s before they deploy (otherwise they'll rip right off 500 meters above the ground just like they'd do on Kerbin).

[Liowen]

There was a good site at http://ksp.freeiz.com/ that would calculate the number of chutes you would need for a certain set of parameters. It appears to be non-functional today (either that or Chrome's just being persnickety).

You need to hit the button to deploy your chutes early on Duna and burn like mad to get your speed below 100 m/s before they deploy (otherwise they'll rip right off 500 meters above the ground just like they'd do on Kerbin).

Hmmm I deploy the drogue chutes first and once I am down to about 150m/s I pop the other ones before the drogues fully open. By the time the drogues open I am nearly down to 50m/s and once all my chutes go I am down to 6.5m/s give or take (this is on Duna.). While I did not know about the chute site myself I did something a bit more trial and error. I would launch my ship into an orbit around Kerbin and deorbit, and see what my chutes would do on the own. I figure if I could get under 6m/s on Kerbin I would be fine for Duna. I know not the most scientific way of doing it, but I had fun seeing if my ideas would work or not LOL.

[kurja]

So i'm trying to land a rover to refuel my lander so i can get Jeb home. all was going well until the landing, it was way too fast. the chutes deployed (5 of them) but didn't deply fully before making a streak of rubble across Duna's Southern Ice Sheets.

are chutes not going to be enough or did they not deploy because i was going to fast?

any ideas?

So the chutes did not fully deploy before you hit the ground? I don't think that's supposed to happen ever, at least I've never seen this, maybe someone knows if there's a known bug..?

[Liowen]

So the chutes did not fully deploy before you hit the ground? I don't think that's supposed to happen ever, at least I've never seen this, maybe someone knows if there's a known bug..?

It could be a bug, I have not had that experience myself so I do not know. If there was a video of it it could shed light on to further understand. One habit I do is if I know I will be landing, even extremely high up, I will deploy my drogue chutes. By doing this I will then have a gauge for how soon after they half open that I need to deploy my others. Might not be the best practice again but it works for me personally, also setting chutes to an action group is not a bad idea either.

[stupid_chris]

In my personal experience, the best with stock chutes is to come in as shallow as possible. The parachutes will only semi deploy at about 10km ASL of Duna, because the pressure is low. You want them to deploy as early as you can, and you want to be going as horizontal as you can so that the predeployed state can slow you as much as possible before hitting 500m.

Alternatively, you could try my mod (link in sig), it was made with a few things in mind concerning landing on Duna, such as predeployment based off altitude. You could arm your parachute in space and set it to predeploy at 20km and fully deploy at 1km to be sure to have it slow you down as much as it can before landing

Edited December 5, 2013 by stupid_chris

[DrMonte]

Just run tests on Kerbin and add twice as more chutes for Duna. capi3101 nice site by the way.

I didn't find the speed for chutes to rip off (didn't run any special tests with high speeds). They might break your ship if you will not place them right. So don't place them all on a single part. If your ship is heavy placing few even on the lowest parts could be a good idea too.

Use Mk25 for reentry. They'll deploy much higher and will slowdown the ship to some reasonable 100m/s. Then Mk16 (better radial) will do their job.

[Starwaster]

In my personal experience, the best with stock chutes is to come in as shallow as possible. The parachutes will only semi deploy at about 10km ASL of Duna, because the pressure is low. You want them to deploy as early as you can, and you want to be going as vertical as you can so that the predeployed state can slow you as much as possible before hitting 500m.

Alternatively, you could try my mod (link in sig), it was made with a few things in mind concerning landing on Duna, such as predeployment based off altitude. You could arm your parachute in space and set it to predeploy at 20km and fully deploy at 1km to be sure to have it slow you down as much as it can before landing

If you want it to be as vertical as possible then you mean steep, not shallow. Shallow would be where you're skimming the atmosphere; more parallel than perpendicular.

[Murph]

Something which is easy to overlook, and hasn't been mentioned yet in this thread. The OP doesn't describe their full flight profile, so we don't know where they were before starting descent (apoapsis, in particular). Unless you've got an extremely robust craft with massive provision of parachutes, it's essential to start the descent from a low orbit (that's BOTH periapsis and apoapsis low). If your apoapsis is high, or you're trying to descend directly from the aerocapture inbound from Kerbol orbit (i.e. before you have actually established a circular orbit), you are carrying LOTS of velocity into the descent and parachutes. It doesn't matter that the planet has aerobraking, that velocity is a problem on a planet like Duna with a low, thin atmosphere. So, use the aerobraking to first reduce your apoapsis down to a nice low level (50-100km, lower is better if your ship is marginal on parachutes or power), before starting the actual descent to the surface. The higher your apoapsis before descent, the greater your velocity during the descent, and the more difficult it becomes to successfully land by any method.

Beyond that, trigger all chutes right at the start of your descent, before you even enter the atmosphere. They will deploy from triggered as soon as the pressure rises to a minimum level, then the partially deployed or streaming state provides additional drag (i.e. extra braking). Of course, doing it like that does make a precision landing extremely hard. For precision on chutes, you either need a massive over provision of chutes, allowing very late deployment, or very careful timing of the start of your descent.

Edited December 5, 2013 by Murph
typo

[stupid_chris]

If you want it to be as vertical as possible then you mean steep, not shallow. Shallow would be where you're skimming the atmosphere; more parallel than perpendicular.

That was a typo, I meant horizontal

[Kasuha]

I had major problem with parachutes on Duna until I found there are also drogues.

Use both drogues and main parachutes. Drogues fully deploy at 2500 m over surface with way less shock and they will bring you medium braking, preparing the ship for the shock from main chute opening. Reduced speed at the point of their opening will also allow main chutes to slow you down more before you hit the ground.

You will still need to brake your fall, but you will spend way less fuel on it.

And I definitely advise against pure vertical landing. Unless you need to hit certain spot on the surface, it is way better to enter the atmosphere almost horizontally (periapsis at 8 km is just about right even for direct descent from interplanetary space), that will provide you more atmosphere to slow down and land. Deploy your chutes and drogues at least at 10 km and let them do the work.

Edited December 5, 2013 by Kasuha

[FlamedSteak]

Drogues are your best friend for Duna and Laythe landings. Deploying a full set of regular chutes you run the risk that they either won't deploy in time or if you've placed them poorly, tear your ship to bits.

The biggest problem with drogues is they're painful to mount radially. I've done some shameful structural modifications to my vessels to get drogues closer to the centre of gravity.

[Starwhip]

Use the Drogue 'chutes to slow you down enough from Hypersonic to more reasonable atmospheric/landing speeds, with the radial/standard (smaller white ones) for the final descent. Also, it's a good idea to have an engine/skycrane, just in case the 'chutes are not enough.

[ohlookabirdie]

thanks for all the help guys. i have yet to try it again, but i will soon. problem is that i have already built the ship and it is already in orbit above kerbin so i cant add new chutes... i may have to redesign the whole thing. i have 4 of the rectangular radial chutes a one of the small white tipped ones. and a but of spare fuel to help. my flight profile was quite horizontal but it was very fast, i will be slowing it down a lot more next time before i even hit the atmosphere

[Kasuha]

Here's an example of using drogues and normal chutes together. The ship came right from interplanetary space with no braking for orbit, only adjusted its periapsis to about 6 km. I only started burning when it was about 100 m above ground.

Javascript is disabled. View full album

[Deathsoul097]

Isn't that your BSC entry Kasuha?

[Kasuha]

Isn't that your BSC entry Kasuha?

Part of it, yes. It involved descent on Duna using chutes so I thought it's a decent demonstration of the technique for landing complex ships.

Edited December 6, 2013 by Kasuha

[DrMonte]

Don't see it mentioned here. In case someone forgets you may use your Kerbin landing chutes on Duna also as they can be repacked on EVA. Note that used chutes will not work in staging.

[Kasuha]

Don't see it mentioned here. In case someone forgets you may use your Kerbin landing chutes on Duna also as they can be repacked on EVA. Note that used chutes will not work in staging.

It's done in the album I posted but it's a bit tricky exactly because they cannot be staged again so I would recommend being careful about it. The best approach is to put their deployment to action group, if you forget you must deploy them manually and if you forget before you enter the atmosphere you may have some serious problems.

[Xephirious]

It's done in the album I posted but it's a bit tricky exactly because they cannot be staged again so I would recommend being careful about it

Haven't tested it myself but I hear a quick load will allow you to stage them again.