Lowest Mass To Duna and Back Challenge

[Guest]

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Requirements/Rules:

- All Participants Must Show Either Photo or Video (YouTube) Evidence (Including VAB Total Vessel Weight)

- No Mods Allowed (Except for KER)

- Maximum Vessel Weight Is 150 tons

- Refueling IS Allowed, As Long As Total Refueler and Other Rocket Mass is 150 tons or less combined

- Due to Request, Command Seats Are Now Allowed!

- Only VAB and SPH, but you must somehow launch your SPH Vehicle on The Launchpad, Not Runway. Wings Are Allowed

- Pods and Chairs Have Separate Winner Categories Now

Your rules don't seem to forbid the use of cheats. Theoretically, someone could put a chair on top of a small rocket engine, turn on Unlimited Fuel and get 1st place without violating any rule.

[sevenperforce]

@Kergarin

I'm doing everything from SL and I'm doing 2.010 tonnes with 147.7 m/s left in LDO. Way overweight but that's SL for you.

If I can manage to land above 3 km then I have good feelings about parallel-staging a Dumpling (with one Ant) with a Doughnut (3 Ants) underneath, using a linear thruster and extra monoprop for circularization and rendezvous. Would only shave down to 1.441 tonnes, though. And that's before the chute.

Edited March 21, 2019 by sevenperforce

[Johnster_Space_Program]

2 hours ago, Aperture Science said:

Your rules don't seem to forbid the use of cheats. Theoretically, someone could put a chair on top of a small rocket engine, turn on Unlimited Fuel and get 1st place without violating any rule.

oh, i will make a change to that now. thanks for pointing out. @Aperture Science

Edited March 21, 2019 by Johnster_Space_Program

[herbal space program]

11 hours ago, Kergarin said:

That's true, dunas thin atmosphere is almost like vacuom, even at the ground.

Besides from this, I think we are coming to that point where we have to figure out dunas highest equatorial mountain, to minimize the drag problems.

Are you sure it's still that thin? I know what it says on the Wiki page, but I have a feeling it's been thickened since that was last updated. What I remember is it's around 0.2atm at ASL now. That would certainly be consistent with how well the chutes seem to work in slowing me down. My earlier ~3t lander was slowed to just over 10 m/s by two radial chutes near ASL, and also a couple of years back I made a plane that could land and reach orbit again with a large but not insane amount of wing area.

 

...So I just took a barometer down to the surface and what it says is indeed consistent with the Wiki, i.e. .067 atm at SL. Funny, it sure does seem thicker than that!

Edited March 22, 2019 by herbal space program

[Kergarin]

5 minutes ago, herbal space program said:

Are you sure it's still that thin? I know what it says on the Wiki page, but I have a feeling it's been thickened since that was last updated. What I remember is it's around 0.2atm at ASL now. That would certainly be consistent with how well the chutes seem to work in slowing me down. My earlier ~3t lander was slowed to just over 10 m/s by two radial chutes near ASL, and also a couple of years back I made a plane that could land and reach orbit again with a large but not insane amount of wing area.

Would have to measure that. It really feels extremely draggy for such a thin atmosphere, but has almost no impact on vacuum optimized engines.

[Kergarin]

@sevenperforce

Im now at 1,605 using the pod. Using a spark on an oscar b and a todorial. But it's almost empty on orbit...

[sevenperforce]

Just now, Kergarin said:

@sevenperforce

Im now at 1,605 using the pod. Using a spark on an oscar b and a todorial. But it's almost empty on orbit...

What's your liftoff altitude?

[Kergarin]

30 minutes ago, sevenperforce said:

What's your liftoff altitude?

This was from around 3000m.

[sevenperforce]

Just now, Kergarin said:

This was from around 3000m.

I tried parallel-staging four Ants and two Oscar-Bs from 6400 m and came up woefully short. I wonder if the drag of the lander can would be less punishing at that altitude.

[sevenperforce]

13 minutes ago, sevenperforce said:

I tried parallel-staging four Ants and two Oscar-Bs from 6400 m and came up woefully short. I wonder if the drag of the lander can would be less punishing at that altitude.

...........and as it turns out, it is. I came up less than 100 m/s short of orbit. This is promising. Would have been easy enough to get out and push, though I was avoiding that on principle.

What's the highest elevation on Duna?

[Kergarin]

34 minutes ago, sevenperforce said:

...........and as it turns out, it is. I came up less than 100 m/s short of orbit. This is promising. Would have been easy enough to get out and push, though I was avoiding that on principle.

What's the highest elevation on Duna?

I have no clue,  would have to check, but 6400 sounds already pretty good. Where is your launch site?

I had an onion stage with a 3+2 ant setup, using a todorial and oscar, which came verry close to orbit

[sevenperforce]

1 hour ago, Kergarin said:

I have no clue,  would have to check, but 6400 sounds already pretty good. Where is your launch site?

Western rim of one of the equatorial craters.

[sevenperforce]

[herbal space program]

6 hours ago, Kergarin said:

Would have to measure that. It really feels extremely draggy for such a thin atmosphere, but has almost no impact on vacuum optimized engines.

Based on my experience, I  wouldn't expect any engine to behave much differently in 0.2 vs. 0.06 atm, but I haven't actually looked at their curves.  I can say however that  I was able to get a landable stall speed on my Duna Moth plane with around twice the relative wing area I typically use on Kerbin, which is more consistent with a SL pressure of 0.2 atm than 0.06. Anyway, I will do some kind of a measurement later tonight to resolve this. As I said before, I'm pretty sure I saw 0.2 on a barometer near the lowest elevation like 3 years ago, but I wouldn't bet my life on it.

[dnbattley]

3 hours ago, Kergarin said:

I have no clue,  would have to check, but 6400 sounds already pretty good. Where is your launch site?

I had an onion stage with a 3+2 ant setup, using a todorial and oscar, which came verry close to orbit

Depending on how cheaty/exploity you guys think this is, I've just checked and this MH-powered monstrosity can take a Kerbal (not in a command seat) to Duna surface and orbit easily (over 200 m/s remaining on my test flight which went up to a 70k orbit). Control is limited, due to relying on a probe core (without comms), but not overly limiting.

[herbal space program]

17 minutes ago, dnbattley said:

Depending on how cheaty/exploity you guys think this is, I've just checked and this MH-powered monstrosity can take a Kerbal (not in a command seat) to Duna surface and orbit easily (over 200 m/s remaining on my test flight which went up to a 70k orbit). Control is limited, due to relying on a probe core (without comms), but not overly limiting.

Huh? Setting aside the question of whether or not an airlock constitutes a pod, how is that going to get all the way from Kerbin's surface to Duna and back with only 1,777 m/s of dV?

...oh NVM. This is just a lander module. Sorry!

Edited March 22, 2019 by herbal space program

[dnbattley]

24 minutes ago, herbal space program said:

...oh NVM. This is just a lander module. Sorry!

Exactly so. I agree it would sorely test the boundaries of decency in a "non command seat" submission, but technically that is what it is.

The airlock is also good for Kerbin re-entry modules with an absurd 2600K heat tolerance...

Edited March 22, 2019 by dnbattley

[sevenperforce]

1 hour ago, dnbattley said:

I agree it would sorely test the boundaries of decency in a "non command seat" submission, but technically that is what it is.

The airlock is also good for Kerbin re-entry modules with an absurd 2600K heat tolerance...

Fascinating!!!!  Did not think of that! Though you need a command module to enter, I assume.

I will hazard it falls afoul of the "command pod" restriction.

5 hours ago, Kergarin said:

I had an onion stage with a 3+2 ant setup, using a todorial and oscar, which came verry close to orbit

I finally managed it. Doughnut and Oscar, four Ants in 3+1 parallel, lander can monoprop to circularize. 1.363 tonnes, 6200 m to orbit with 179 m/s remaining. Still need to work out power and chutes but that's about as slim as it gets with a real command module.

[Kergarin]

9 hours ago, sevenperforce said:

 

I finally managed it. Doughnut and Oscar, four Ants in 3+1 parallel, lander can monoprop to circularize. 1.363 tonnes, 6200 m to orbit with 179 m/s remaining. Still need to work out power and chutes but that's about as slim as it gets with a real command module.

Congrats! That's really low. My best for the pod was 1.603t including the chute and docking port. But I guess again the fairing will make them equal heavy?

Mine is a spark with a fixed oscar plus a doghout which is drained first and then dropped when empty.

I have tried everything from ants over sole rcs and ions and combing everything possible, also tried versions without separate orbiter where the ship lands as whole. I have even tried ion staging and empty battery dropping.

In the end the sparks insane twr >4 on this lander at duna seems to be a big advantage over the lighter and/or more efficient engines, as it almost immediately goes ballistic instead of loosing a lot of dV while fighting gravity. 

With this 1.6t lander, I was able to bring the entire rocket down to ~5.6t by tweaking the fuel.

But while the old one was easy and reliable, this one has a verry small margin and doesn't forgive any mistakes.

Edit: what do you need power for? For me the pods battery is enough for landing, ascend and docking.

And is monopop really efficient for your? I always ended up with less dV, when trying this.

Edited March 22, 2019 by Kergarin

[sevenperforce]

10 hours ago, Kergarin said:

Congrats! That's really low. My best for the pod was 1.603t including the chute and docking port. But I guess again the fairing will make them equal heavy?

Mine is a spark with a fixed oscar plus a doghout which is drained first and then dropped when empty.

In the end the sparks insane twr >4 on this lander at duna seems to be a big advantage over the lighter and/or more efficient engines, as it almost immediately goes ballistic instead of loosing a lot of dV while fighting gravity. 

With this 1.6t lander, I was able to bring the entire rocket down to ~5.6t by tweaking the fuel.

Nice!!

10 hours ago, Kergarin said:

What do you need power for? For me the pods battery is enough for landing, ascend and docking.

And is monopop really efficient for your? I always ended up with less dV, when trying this.

I may need to land at a low altitude and lithobrake off the chute, then roll uphill to a better ascent point. If I do that, I'll need renewable power. 

Monoprop is not worth it with the command pod, but the lander can has 50% more monoprop and is significantly less massive.

[sevenperforce]

@Kergarin

I've got the orbital stack down to 1.807 tonnes and the launch vehicle down to 5.074 tonnes but I'm still having trouble with the ascent profile. I know it has sufficient dV to make orbit but only if every drop of propellant is used to the max. Using only a Whiplash, a Dawn, and Ants.

Switching out for Panther was not worth it...the Whiplash can get me more extra dV than switching out the mass savings for extra S2 props.

The lander can is just so damn bulky or I would try using Junos and Sparks with a horizontally-climbing spaceplane.

 

[Stormpilot]

On 3/11/2019 at 4:57 AM, mrhexed said:

 

To anyone who reads this:
Refueling is allowed.

 

WE KNOW!

[herbal space program]

25 minutes ago, STORMPILOTkerbalkind said:

WE KNOW!

What we don't know however is if either the refueling vessel or the delivered fuel counts towards the total mass.  If the vessel does, then there's no point at all in including a refueling mission, because it will just require a lot of duplication of mission components.  If only the delivered fuel counts, then significantly lighter missions than what we've seen so far would definitely become possible, much more so if none of it counts . Perhaps OP @Johnster_Space_Program can provide a clarification on that point. Some people who have been working hard under the assumption that it would all count could definitely use one.

[Stormpilot]

1 minute ago, herbal space program said:

What we don't know however is if either the refueling vessel or the delivered fuel counts towards the total mass.  If the vessel does, then there's no point at all in including a refueling mission, because it will just require a lot of duplication of mission components.  If only the delivered fuel counts, then significantly lighter missions than what we've seen so far would definitely become possible, much more so if none of it counts . Perhaps OP @Johnster_Space_Program can provide a clarification on that point. Some people who have been working hard under the assumption that it would all count could definitely use one.

Ok then...

[Kergarin]

4 hours ago, sevenperforce said:

I may need to land at a low altitude and lithobrake off the chute, then roll uphill to a better ascent point. If I do that, I'll need renewable power. 

Monoprop is not worth it with the command pod, but the lander can has 50% more monoprop and is significantly less massive.

That makes sense.

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

The Panther even brings the more aerodynamic pod to only to around 8-900m/s before flameout and drains fuel like crazy. It's stated as the same Isp on wet mode as the whiplash but I guess they have different curves.

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.

 

53 minutes ago, herbal space program said:

What we don't know however is if either the refueling vessel or the delivered fuel counts towards the total mass.  If the vessel does, then there's no point at all in including a refueling mission, because it will just require a lot of duplication of mission components.  If only the delivered fuel counts, then significantly lighter missions than what we've seen so far would definitely become possible, much more so if none of it counts . Perhaps OP @Johnster_Space_Program can provide a clarification on that point. Some people who have been working hard under the assumption that it would all count could definitely use one.

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...

Edited March 22, 2019 by Kergarin