Lowest Mass To Duna and Back Challenge

[herbal space program]

3 hours ago, Kergarin said:

Wait... It was my understanding, that this rule means ISRU refuelling with all the needed equipment built in to the ship itself!? And not any external refuelling?!

If external refuelling is allowed, this changes everything and breakes the challenge.

We then could just send up a verry simple and lightweight ship that makes it barley to orbit, then external refuel at orbit, duna, Ike, and for the way back...

My apologies if OP already made this clear somewhere upthread. What it says is " Refueling IS Allowed, As Long As Total Refueler and Other Rocket Mass is 150 tons or less combined", which clearly implies external refueling but is a bit ambiguous about what counts towards total mass. FWIW I am totally with you on your interpretation, as pretty much anything that can make LKO could do the rest of the mission easily if you don't also have to include the mass of the refueling vessel. But of course if you do have to include it,  then refueling of any kind is totally pointless. So. Regardless, my vote is with you, that we need to have everything you launch from Kerbin count period, or else the challenge is more or less broken, and I hope OP will see it that way as well.

Edited March 22, 2019 by herbal space program

[sevenperforce]

3 minutes ago, Kergarin said:

I also can't land at 6000m. I use the chute plus powered landing, which only works below 4000m.

The chute's impact resistance is 12 m/s and a chute slows a 1.5-tonne stack to around 16 m/s at 3000-4000 m. My plan is to cut the chute just before impact and use the reaction wheels to flip chute-down and lithobrake it. 

3 minutes ago, Kergarin said:

I've also tried to skip the Spark on ascend, going below 5t, but the dawn alone is just to weak to circularize. The best I can get out the whiplash is 1500m/s with ap around 80km. Still far away from what the dawn would need. I've also tried it with more than one dawn, but they are heavy and energy hungry.

I guess it just needs a little push from the landers engine using a little drop tank, but that's not possible in my actual linear stack. I'm trying to change this without making the fairing too draggy.

My lander engines are arranged radially so they can burn around the rest of the stack. The Dawn can fire through the drop tank.

3 minutes ago, Kergarin said:

Wait... It was my understanding, that this rule means ISRU refuelling with all the needed equipment built in to the ship itself!? And not any external refuelling?!

If external refuelling is allowed, this changes everything and breakes the challenge.

We then could just send up a verry simple and lightweight ship that makes it barley to orbit, then external refuel at orbit, duna, Ike, and for the way back...

Yeah, that would make no sense.

[Johnster_Space_Program]

On ‎3‎/‎20‎/‎2019 at 4:53 PM, Kergarin said:

That's what i got actually:

5.794 tons

 

that Ike Landing was absolutely unintended. 
I just realized how much dv i had left in Duna Orbit, and gave it a try.
 

Combining a Whiplash first stage with a Spark turned out to be more efficient than an rapier.
The solar panels are mounted asymetrical to always ensure all 4 can get into direct sunlight
 

 

 

Good Job @Kergarin! Your 1st currently in pods now, here is your badge, you also got 936 points (im finally getting around to updating leaderboards):

Edited March 22, 2019 by Johnster_Space_Program

[Kergarin]

1 hour ago, sevenperforce said:

The chute's impact resistance is 12 m/s and a chute slows a 1.5-tonne stack to around 16 m/s at 3000-4000 m. My plan is to cut the chute just before impact and use the reaction wheels to flip chute-down and lithobrake it. 

My lander engines are arranged radially so they can burn around the rest of the stack. The Dawn can fire through the drop tank.

 That chute thing is an interesting idea. You also need one decoupler less. 

The problem is, my lightest lander uses the Spark... I'm now trying my other lander designs again with 4+2 ants, and let the 4 ants fire around the ion stage while dropping some dumplings in succession. Sadly this stack becomes so draggy, that I have to keep the fairing and wait until 40km until I can fire them...

[herbal space program]

3 minutes ago, Kergarin said:

 That chute thing is an interesting idea. You also need one decoupler less. 

The problem is, my lightest lander uses the Spark... I'm now trying my other lander designs again with 4+2 ants, and let the 4 ants fire around the ion stage while dropping some dumplings in succession. Sadly this stack becomes so draggy, that I have to keep the fairing and wait until 40km until I can fire them...

I'm just blown away that you guys are able to get that lander can to perform adequately in any phase of the mission. I found the 1.8m profile so draggy early on that I abandoned it after only a few iterations. I  guess I gave up on it too soon!

[Kergarin]

4 hours ago, herbal space program said:

I'm just blown away that you guys are able to get that lander can to perform adequately in any phase of the mission. I found the 1.8m profile so draggy early on that I abandoned it after only a few iterations. I  guess I gave up on it too soon!

Well that's mostly @sevenperforce

I'm focusing more on the pod. But actually it looks like this will stay around 5.6t

 

5 hours ago, Johnster_Space_Program said:

Good Job @Kergarin! Your 1st currently in pods now, here is your badge, you also got 936 points (im finally getting around to updating leaderboards):

Thank you!

[sevenperforce]

5 hours ago, herbal space program said:

I'm just blown away that you guys are able to get that lander can to perform adequately in any phase of the mission. I found the 1.8m profile so draggy early on that I abandoned it after only a few iterations. I  guess I gave up on it too soon!

Lander can sucks on Kerbin but it is perfect for Duna provided you launch at high altitude.

[Johnster_Space_Program]

22 hours ago, sevenperforce said:

Lander can sucks on Kerbin but it is perfect for Duna provided you launch at high altitude.

That makes sense. Its also good on non atmospheric bodies like ike.

Edited March 24, 2019 by Johnster_Space_Program

[Kergarin]

Any progress on this?

While I can definitely go lower than my 5.8 ton submission, I did only chase approaches wich looked promising to end under 5 tones, but did not breakthroug until now.  

Saving 0.1t by using the landers engine always ended up with needing larger fairings. I have never before realized how heavy they are.

@sevenperforce?

[herbal space program]

Speaking of fairings, I'm at 5.7 tons right now using a Rapier engine and a 1-piece Mk1 upper stage:

 

Unfortunately I won't be able to make Ike with this unless I ship another can of xenon for .025 tons, so I'll probably try it one more time before my final submission. The reason I wanted to mention it now is that the fairing that you can see in the second shot, which bulges out the smallest amount possible and then tapers very slowly, seems to have magical properties in terms of reducing drag. With that fairing, I was able to get to as much as 1650 m/s with the Rapier engine, while I was topping out just above 1500 with its flush equivalent. I suspected this before, but now I know for sure it's true. Anyway, I'm going to get this rig to where it can do Ike for another .025 tons and call it a day...

[Johnster_Space_Program]

For those of you who have already completed this challenge, I have a new one for you!

 

 

Edited March 27, 2019 by Johnster_Space_Program

[Kergarin]

On 3/25/2019 at 5:34 PM, herbal space program said:

Speaking of fairings, I'm at 5.7 tons right now using a Rapier engine and a 1-piece Mk1 upper stage:

 

Unfortunately I won't be able to make Ike with this unless I ship another can of xenon for .025 tons, so I'll probably try it one more time before my final submission. The reason I wanted to mention it now is that the fairing that you can see in the second shot, which bulges out the smallest amount possible and then tapers very slowly, seems to have magical properties in terms of reducing drag. With that fairing, I was able to get to as much as 1650 m/s with the Rapier engine, while I was topping out just above 1500 with its flush equivalent. I suspected this before, but now I know for sure it's true. Anyway, I'm going to get this rig to where it can do Ike for another .025 tons and call it a day...

That's also pretty lightweight! The question is, if the dawn firing through the Spark is legal?

[herbal space program]

26 minutes ago, Kergarin said:

That's also pretty lightweight! The question is, if the dawn firing through the Spark is legal?

It's the only engine in the game that lets you do that and OP said nothing about it, so I don't see why not.

[Kergarin]

2 minutes ago, herbal space program said:

It's the only engine in the game that lets you do that and OP said nothing about it, so I don't see why not.

So I would have to go back to the drawing board 

[sevenperforce]

11 minutes ago, Kergarin said:

So I would have to go back to the drawing board 

I am not sure that doing this is any better than Duna Orbit Rendezvous with the Dawn and ions waiting up there.

[herbal space program]

1 minute ago, sevenperforce said:

I am not sure that doing this is any better than Duna Orbit Rendezvous with the Dawn and ions waiting up there.

I was going to say the same thing. Also, I had a version before with the ions mounted on the front that didn't do this, at the cost of only  0.12t in extra parts and some loss in efficiency getting to orbit, but it looked dumb and was just a royal pain in the engine plate to fly.

[mrhexed]

On 3/22/2019 at 1:10 PM, STORMPILOTkerbalkind said:

WE KNOW!

This was posted before it was a rule because I got confirmation from johnster on discord

[Mopoii]

Hi everyone,

Here's my entry (command pod category) :

Mission screenshots : https://imgur.com/gallery/I1ciw4C

Managed to get it done with just over 10.4 tons

[PhoenixRise86]

I'll give it a shot. Not sure I can beat 3.95 tons, but it'll be fun to see how close I can get.

Any there any rules against using the kerbal's EVA pack for part of the maneuvers? Provided it doesnt get refilled from a command pod, that would feel like cheating (I'm planning on flying by command seat).

Edited April 20, 2019 by PhoenixRise86