How do people get through Duna's atmosphere without getting the heating effects?

[yarknark]

I've seen people go through the Duna atmosphere and land without burning up before. I'm not entirely sure how it's done, and I'm curious.
My assumption is that they go at slow enough speeds to where the atmosphere doesn't take as much effect, but I'm not sure that's the case. If it is, yay! And if it is, I wonder how quick you can go without burning up?

By burning, I mean seeing your craft get the big fiery effect around it.

That's really all I wanted to ask. Thanks
 

[king of nowhere]

4 hours ago, yarknark said:

I've seen people go through the Duna atmosphere and land without burning up before. I'm not entirely sure how it's done, and I'm curious.
My assumption is that they go at slow enough speeds to where the atmosphere doesn't take as much effect, but I'm not sure that's the case. If it is, yay! And if it is, I wonder how quick you can go without burning up?
 

yes, it is exactly the case. there is no trick, it's just that duna is particularly good for aerobraking.

for you see, when you come to duna from another planet, you have an intercept speed. in addition to that intercept speed, you fall towards the planet, going faster and faster until you hit the atmosphere.

but duna is small. it has low gravity. so even when you fall towards it, you don't pick up much speed. And so, it is possible to come from an interplanetary trajectory and still hit atmosphere at less than 1800 m/s, which is a safe speed in most cases.

that is a general rule. the smaller a planet, the better it is for aerobraking - if it has an atmosphere.

 

As for how fast you can go, it depends on the ship, and whether it has some thermally sensitive components. those have breaking points at 1200 K, and they tend to explode over 1500 m/s unless they are in a shielded position. a normal ship with all components having a thermal breaking point of 2000 K.... you can hit atmosphere between 1900 and 2000 m/s. With a thermal shield? I managed to survive a reentry at 10 km/s.

Your profile also matters. In the high atmosphere you don't heat much, but you brake even less, so you can take a short passage in the atmosphere if you stay high - useful to circularize, but it won't help you with an interplanetary capture burn. On kerbin you can enter the atmosphere with a normal ship at 2300 m/s because your trajectory is almost circular, you're staying up high, and by the time you drop in the denser atmosphere you already lost enough speed to survive. On duna, if you want to get captured, you have to go low on your first pass, and that means hitting dense atmosphere at full speed, so your maximum safe speed is lower.

By the way, somebody may claim that it's better to go deep immediately for convoluted reasons of heat transfer, but it's a urban legend. it's potentially true only in rare corner cases. Perhaps it was true in a previous version.