Need help with Duna craft

[jfull]

I'm pretty familiar with KSP, but one thing I've never actually done is take off from another planet for a return trip to Kerban.

I've also never actually landed anything on Duna, so I don't have a feel for its atmosphere.

This is a lander design for my next mission to Duna, It needs to be able to take off and return to orbit, then dock with my transfer vehicle to go home. Does it look up to the job?

Also, between the de-orbit and the landing, am I going to use up enough fuel that it would be worth it to add some Kethane processing parts to refuel it?

[rryy]

I suggest replacing the two parachutes with drogue chutes and place some radial chutes. Duna's gravity is also much weaker, so you could probably switch the two LV-T45s with two LV-909s or a single aerospike.

[jfull]

I suggest replacing the two parachutes with drogue chutes and place some radial chutes.

I actually already made that change

Duna's gravity is also much weaker, so you could probably switch the two LV-T45s with two LV-909s or a single aerospike.

You're sure I won't need the power? I know Duna's atmosphere is thinner and the gravity weaker, but I don't want to underestimate the power I'll need to lift off

Edit: I've been experimenting a bit on Kerban, and I think I'll end up using 2 Aerospikes on the lander.

I know I could get away with one, but I'm gonna use the space between them to mount a Rover

Edited August 9, 2013 by jfull

[NoMrBond]

If you want to check exactly, you could use the Kerbal Engineer Redux mod, it'll give you exact TWR and dV numbers for your ship including its performance on other planetary bodies (such as Duna).

[SeventhDurandal]

I've used a design very similar to yours for trips to Duna and back many times.

The NERVAs have no problem lifting off, especially since I usually leave the lander behind. With this ship I don't even need a transfer stage, with aerobraking it makes the trip all on its own.

Like you I also found it easier to launch upside-down with this design.

[sojourner]

Get rid of the big center tank and replace the aerospikes with LV-N's. More than enough to do powered landings from 100km orbit and then takeoff again to a 150km orbit:

http://s479.photobucket.com/user/seattle221/media/Kerbal/nukelander/screenshot17.png.html?sort=3&o=16

No parachutes needed.

[SeventhDurandal]

psuedo-double post

Edited August 9, 2013 by SeventhDurandal

[Geschosskopf]

Parachutes aren't strictly required on Duna but they do save fuel during landing, which you can then use to take off again. But this is somewhat counterbalanced by then having to lift a couple tons of parachutes, although the weak gravity and thin atmosphere generally (for just your average lander, not some huge thing) make having parachutes work in your favor.

Kerbal Engineer Redux is a must to make sure you've got enough TWR to get off the ground and enough burn time to land and take off. A couple minutes is about all you need. If you want to see what parachutes do for you, take a look at the Parachute Calculator: http://ksp.freeiz.com/

Just remember to pop the chutes at like 19km or they won't open in time to do you any good and also come in low and flat for the same reason (and also to get more benefit from aerobraking).

But as Sojourner says, it's not THAT hard to get off Duna. If nuclear engines have enough TWR, despite their own heavy weight and generally low thrust, then you should feel pretty confident.

[jfull]

Thanks for the input guys

I actually ended up having to redesign a bit after I realized that it wouldn't actually fit in the payload bay I want to use to hold it.

Now I'm trying to work out if its still possible to replace the aerospikes with the nuclear engines

Edited August 9, 2013 by jfull