Kerbal-X to Duna ?

[Warzouz]

Waiting for 1.1, I was playing with Kerbal-X. I took it to Mun, to Minmus and tested going to Duna. Obviously, I failed getting back. I had to cheat the return burn from Duna low orbit.

As of 1.0.5, Kerbal-X as 6428m/s (6463m/s is removing monoprop). dV map show 6090m/s to land on Duna, not counting aerobraking) and 1940m/s to get back. Total is 8030m/s. Kerbal-X misses 1600m/s

Obviously, in my test, I only missed 600m/s (I don't remember precisely). I used aerocapture (by putting the lander radial, the drag increased). But, when I landed, even doing the same, I had to burn to slow down (maybe 300 to 500m/s) for the chute to safely open.

• What do you think could be done without modifying Kerbal X ? Mun or Ike gravity assist ? How
• By slightly modifying Kerbal-X what would you do ? I was thinking about 2 drogue chutes or lighten it ?

Do you think it's possible to go to Duna with Kerbal-X ?

 

[Nich]

Body lift should get you slow enough to keep from using engines on Duna landing

[Warzouz]

44 minutes ago, Nich said:

Body lift should get you slow enough to keep from using engines on Duna landing

No, the speed doesn't reduce fast enough. If I don't slowdown, I crash before being able to deploy chutes. Drogues may be the only option.

I even had an issue : I deployed the chutes when the icon was "Safe" (not even risky). Chutes deployed perfectly, but speed continues to increase and get above safe limit. When the craft reached the defined altitude, the chutes were destroyed while opening.

Anyone had experience with a Ike gravity assist on the return trip ?

Edited March 13, 2016 by Warzouz

[Nich]

Hmm..  I will have to try it but I have landed some monsters on Duna with only body lift, parachutes and a powered landing.  It is really nice now that landing gear can take a bit of a hit

[Warzouz]

10 minutes ago, Nich said:

Hmm..  I will have to try it but I have landed some monsters on Duna with only body lift, parachutes and a powered landing.  It is really nice now that landing gear can take a bit of a hit

Did you do it in 1.0.4 or 1.0.5. In 1.0.4, regular chute could be open at around 500/600m/s and were very efficient to land without engine. In 1.0.5, it's not possible to open chute before 220m/s (even lower than on Kerbin).

Further more, Kerbal X is mostly full of fuel and is not design for Duna reentry. The chute only slows down the capsule to 8m/s on Kerbin. It has half the chute of my Duna-lander and weight twice...

Sure Kerbal-X is not designed for Duna. I was just wondering if it could be down.

[Alpha188]

5 hours ago, Warzouz said:

Obviously, in my test, I only missed 600m/s (I don't remember precisely). I used aerocapture (by putting the lander radial, the drag increased). But, when I landed, even doing the same, I had to burn to slow down (maybe 300 to 500m/s) for the chute to safely open.

• What do you think could be done without modifying Kerbal X ? Mun or Ike gravity assist ? How
• By slightly modifying Kerbal-X what would you do ? I was thinking about 2 drogue chutes or lighten it ?

I think you should just add some airbrakes. They are incredibly powerful, and they will lower your speed until you can deploy parachutes. I'm going to test it right now, but I think 4 airbrakes will do the trick.

 

EDIT: did some tests, turns out that with 4 airbrakes you need to burn for about 50 m/s. You can burn even less, but your landing speed will be about 27 m/s. The lander had almost full fuel load, so you won't go faster.

Edited March 13, 2016 by Alpha188

[Warzouz]

29 minutes ago, Alpha188 said:

I think you should just add some airbrakes. They are incredibly powerful, and they will lower your speed until you can deploy parachutes. I'm going to test it right now, but I think 4 airbrakes will do the trick.

2 airbrake don't do the trick. Kerbal X lander is heavy. I'm trying drogues but I can't slowdown either. I think we need both.

[Alpha188]

46 minutes ago, Alpha188 said:

EDIT: did some tests, turns out that with 4 airbrakes you need to burn for about 50 m/s. You can burn even less, but your landing speed will be about 27 m/s. The lander had almost full fuel load, so you won't go faster.

Sorry for the edit, but it looks like 4 airbrakes are about right.

[Nich]

Yes I have done landings in monsters on Duna.  I was able to get down to about 170 - 180 using body lift.  You have to do it at just the right altitude (about 8 -10 km)  Too high and you will speed up with the parachute deployed and rip it off.  Too low and you lose too much speed and don't have enough lift to stop your descent.  

So 6463 total dv

-1052 perfect transfer to Duna

-10 dv powered landing

-646 perfect return

gives 4755 dv

if you can get off kerbin for 3200 dv that leaves 1555 to get off duna.  It has a pretty high TWR so 3200 is definitely possible.  I normally pack 1500 dv but looking at a dv map 1450 is possible so 1400 with a perfect assent is not impossible.  Thus leaving 155 dv for errors.  4 Airbrakes eats up only 60 dv so if your spending more then this to slow down then it is worth it.

[PLAD]

I made it to to Duna's surface and back with a stock Kerbal-X, but that was in version 0.90. Back then the KX had 7333m/s of delta-V, but it took a minimum of 4358m/s to get into a 75x75km Kerbin orbit from the surface back then. Now the KX has about 6459m/s but it takes about 3350m/s to get into orbit. The number you really care about is the delta-V available once you are in your Kerbin parking orbit, so  back in 1.04 I did some experiments and got it up there with 3012m/s left. That beats the 2866m/s I had left in Kerbin orbit in my attempt, so it should be possible to do this in 1.05, as long as you can survive the aerobraking. Note that I made it from LKO to the Duna aerobraking for 878m/s (thanks to those 5 flybys of Mun), 48m/s from Duna encounter to landing, 1340m/s from Duna surface to 50x50km orbit, and finally 528m/s from LDO to Kerbin aerobraking (with Ike flyby). 2794m/s total. That leaves about 220m/s to deal with aerobraking and drag issues in a 1.0.5 attempt. I think the the stock KX doesn't have any kind of heat shield, so I imagine several braking passes will be needed to survive the Kerbin landing.

The stock K-X is a fascinating ship, I think it can just barely do a number of interesting missions. I haven't tried it for anything since a Kerbin-Mun-Minmus-Kerbin mission in 1.02 though. I would be very interested to see the mission if you do this.

Edit- Someone else did another Kerbal-X to Duna and back mission only with only one Mun flyby (and one of Ike), he chose the absolute optimal transfer windows out and back (which cost about 140 81m/s more), but landed and took off for about 100 55m/s less than I did, but I have not found that mission report yet. So the mission doesn't have to be as complicated as the one I did. His was version 0.90 too.

2nd edit- found it. Von Ziegendorf made a spectacularly efficient Duna landing and return to orbit. He did LKO to Duna arrival 985m/s, Duna arrival to landing 26m/s, Duna surface to orbit 1307m/s, LDO to Kerbin landing 502m/s. 2820m/s total. The modern aero model might make that impossible to match.

Edited March 15, 2016 by PLAD

[Plusck]

I was just plotting a Duna return: from a 55km Duna orbit, I could make a Kerbin encounter with 520 m/s using Ike for gravity assist (15km Pe at Ike: you could do better if you're lucky with mountains...).

Edited March 15, 2016 by Plusck

[Warzouz]

3 hours ago, Plusck said:

I was just plotting a Duna return: from a 55km Duna orbit, I could make a Kerbin encounter with 520 m/s using Ike for gravity assist (15km Pe at Ike: you could do better if you're lucky with mountains...).

From memory, that may be a 150m/s gain, not bad.

[sal_vager]

The Kerbal X is able to land on Duna, but it really needs some drogues as you won't have much fuel left.

I didn't use KER or anything else to manage this, but I did wait until the optimum times to make each burn and I exited the Kerbin SoI retrograde to save a little fuel.

[Warzouz]

43 minutes ago, sal_vager said:

The Kerbal X is able to land on Duna, but it really needs some drogues as you won't have much fuel left.

I didn't use KER or anything else to manage this, but I did wait until the optimum times to make each burn and I exited the Kerbin SoI retrograde to save a little fuel.

I tried only adding drogue chutes but I wasn't able to open them without burning. I crashed. I think 2 airbrakes + 2 drogues would do the trick (or 4 airbrakes).

[sal_vager]

Oh I had to made a burn as well, but only until I could open the drogues.