Landing with DRE and RSS

[BadRocketsCo.]

So I have a question related to using Duna's atmosphere to go straight for a landing when using DRE and RSS. Let's say, that I have an unmanned craft going to Duna and I would like to go straight for the landing without any orbit insertion. How high should my Periapsis be, so that I could land without burning up and G-forces ripping my craft apart?

[Hodo]

If you are talking about trying to come straight down and landing from orbit, you will have to burn A LOT of delta V to bring the craft to a stop and basically fall straight down. Even then I can't say for sure if your craft would survive the fall. Honestly Duna is one of the easiest planets to land on with an atmosphere due to its thin atmosphere. As long as you have a heat shield and a pretty conservative decent angle you shouldn't have to much of an issue with burning or G forces. The hard part on Duna is slowing down for landing without hitting the ground at 20+m/s. Most people use retro rockets and parachutes to land pretty softly on Duna. I used nothing but rockets, and I think everyone else had it right.

[BadRocketsCo.]

No no, I men't to aerobreak to slow myself down straight from interplanetary speeds to speeds, that are slow enough to not enter orbit again and land., kinda like Curiousity did.

Edited March 23, 2014 by BadRocketsCo.

[Hodo]

Yes, you can. But you will need heat shields. Go for a shallow PE, that just barrely breaks the atmosphere but deep enough to slow the craft down to bring your AP down to the new PE. You may have to do several burns to get there but it is possible to do it in one aerobreak.

[BadRocketsCo.]

But as I understand, I wouldn't need to worry about how low the periapsis is? Even with RSS?

[Hodo]

But as I understand, I wouldn't need to worry about how low the periapsis is? Even with RSS?

You will still need to worry about it. To low and your craft will burn up or lawn dart into Duna, to high and you will just skip through the atmosphere and back into space.

[BadRocketsCo.]

Oh, my bad, the page didn't refresh to show the new post

[BadRocketsCo.]

But what Periapsis hight would be good with the RSS atmosphere scale? Around 30 000 meters?

[Hodo]

But what Periapsis hight would be good with the RSS atmosphere scale? Around 30 000 meters?

That I can not answer for you, I haven't been to Duna with the RSS atmosphere scale yet, last time I went there was when I had stock sized Kerbin system and then I set my PE for 20km and that worked fine. 30km might be to low though, but it would be worth a try.

[BadRocketsCo.]

Oh well, I will try somewhere around 40 000 meters and hope for the best. I hope my cute rover won't fly off into deep space

[BadRocketsCo.]

But still, thank you for trying to help!

[CrazyCanadian]

im curious as to your results?

EDIT: I just did this with a probe from earth in RSS. I hit duna from Transfer at 40km and was supprised the atmo started around 150km..?!?! being a thin atmosphere I figured lets see... it did go alright in the end for me but I had extra sections still attached to my probe from over construction of the initial launch craft "MOAR FUEL!!" **I used my Apollo Mission Launch vehicle, so since this probe was a lot smaller than my moon landing mission the rocket had a lot of extra punch left.

either way I lost all my engines on the exposed section and eventually lost that fuel tank.. . no g force issues though... and I would have come into a reentry but I jettisoned the 2nd last stage (survived aerobrake) and fired the probes little engine up, giving it the boost out of the upper atmo...

it currently sits just above Duna's atmosphere .

Edited March 29, 2014 by CrazyCanadian

[NathanKell]

Mars's atmosphere is not dense or high-pressure, but it does extend outwards a ways.

[maccollo]

The altitude where you should put the periaps depends on the drag coefficient of your lander. If it's higher you can put the perhaps higher without skipping out again. The inflatable heat shield have amazing for slowing down at Mars, so good I think they might be completely unrealistic.

My most recent attempt to go to Mars involved a 140 ton lander. I entered with a periaps a 25 km or so.

The hard part is not smashing into the ground. If your landing site is high up and/or you don't have sufficient thrust to kill the last bit of velocity smashing into the ground can happen very easily =P

Edited March 29, 2014 by maccollo

[BadRocketsCo.]

Oh, things have been happening here! Anyways, I set my Periapsis at 30 000 meters and I landed without a problem, atleast reentry wise, my poor rover crashed into the ground because I made the parachutes to open too fast, thus ripping everything apart... :'(

Edited April 1, 2014 by BadRocketsCo.