Monomun

[sevenperforce]

Send Jeb to the Mun.

Plant a flag.

Bring Jeb safely back to Kerbin.

Use monopropellant ONLY for your propulsion.

Extra points: no electricity or reaction wheels for pointing; use monoprop for all attitude control.

Lowest launch mass wins.

I can do it at 127 tonnes...let's see who can do better.

Edited April 26, 2022 by sevenperforce

[Admiral Fluffy]

This should be pretty hard. Getting to orbit with only monoprop isn't too hard. How hard should the Mun be?

[sevenperforce]

2 hours ago, Admiral Fluffy said:

This should be pretty hard. Getting to orbit with only monoprop isn't too hard. How hard should the Mun be?

The sea level thrust/area ratio of the Puff engines is horrible so unless you clip them wildly you end up with a ridiculously fat first and second stage, which tends to make parallel staging prohibitive. 

[Akagi]

This should be amusing...

[Poppa Wheelie]

Using only stock engines?  I think the O-10 "Puff" is the only stock monoprop engine.

[QF9E]

My submission: 15.888 tons. Only monoprop, no electrics used at all.

Full report: https://imgur.com/a/Y5fxohp

On the launchpad (sorry for cutting of the borders. Nothing went as planned with KSP today, including the fact that it is supposed to run in 1920 x 1080 and not in 1920 x 1200 as it did today).

My spacecraft. I used Munar orbit rendezvous with both lander and command module based on a command chair. Getting from one chair to the other was more than a bit stressful as Valentina was not wearing her EMU to save weight.

Landed on the Mun, flag planted

Kerbin landing

Edit: slightly different overall mass. My earlier reported mass was 15.803 tons, the corrected mass is 15.88 tons, including Valentina. Due to my optimization process I have a lot of different versions of the same launcher, and I inadvertently used an old one. Main difference between the versions is that the new version has a more optimized payload fairing, which made it a bit lighter, and one extra Puff engine as the old version was slightly underpowered.

Edited May 2, 2022 by QF9E

[sevenperforce]

5 hours ago, QF9E said:

My submission…

Impressive. And I thought I was coming in well with a single-stage Mun lander and return vehicle.

I’m assuming you could shave that significantly lower by angling your Puff engines to reduce cosine losses, no?

Edited May 2, 2022 by sevenperforce

[camacju]

Does EVA propellant count as monopropellant?

[sevenperforce]

3 minutes ago, camacju said:

Does EVA propellant count as monopropellant?

Yep! Go for it.

[QF9E]

12 hours ago, sevenperforce said:

Impressive. And I thought I was coming in well with a single-stage Mun lander and return vehicle.

I’m assuming you could shave that significantly lower by angling your Puff engines to reduce cosine losses, no?

Thank you!

My earlier experiments with angling the Puff seemed to indicate that it does not matter, so I did not look into it any further. However, your comment has made me check again, and it turns out you can increase dv by about 1.5% by optimizing the Puff angle.

That said, I did not go overboard with optimizing my launch vehicle: the bulk of the mass savings came from optimizing my spacecraft and lander. For instance, I suspect that there is quite a bit of mass to be saved by optimizing the staging sequence. Or find a way to not need a heatshield (which makes up 10% of the overall spacecraft mass in LKO) or use a single stage Mun lander (which saves a command chair, which makes up 5% of the spacecraft mass).

[camacju]

I like spaceplanes, so I tried a spaceplane approach. It didn't go as well as I had hoped - I think QF9E's design will have an edge over mine once properly optimized.

14.1 tons on runway

Spoiler

Launch

Steep climb to increase Isp of Puff engine.

Continuing climb. The drop tanks have just enough fuel to get to Mach 1, where they're dropped to decrease drag.

Spaceplane runs out of fuel and coasts to above the atmosphere

Very large circularization burn

Kerbin orbit

Mun transfer

Deep space maneuver to massively reduce capture burn

Mun orbit insertion and landing burn

Final descent

Flag!

Ascent from Mun

In orbit

Return to Kerbin

A bare Kerbal can survive reentry, but it's a narrow margin. This took a lot of trial and error.

Landed

 

[QF9E]

56 minutes ago, camacju said:

A bare Kerbal can survive reentry, but it's a narrow margin.

Really? I've tried many times, but never successfully. And getting back from the Mun, no less!

How did you do it, if you are willing to share your secrets with us?

[sevenperforce]

15 minutes ago, QF9E said:

Really? I've tried many times, but never successfully. And getting back from the Mun, no less!

How did you do it, if you are willing to share your secrets with us?

Head-down, back to windward, and very very gradually.

[Poppa Wheelie]

Wow!  I'm super-impressed by the 14 - 16t solutions from @QF9E and @camacju!  I have a lot to learn about thinking smaller when the challenge is all about minimal mass.

Question for you pros:  What was your process for building your booster stages?  There was no obvious way to sum up stage dV to the 3200m/s called for in the dV Map.  Do you have a method or rules of thumb you could share?  My process was trial and error until I got something to work.

Here is my submission in the "amateur" category.  47.018t at launch.

Full Report:  https://imgur.com/a/tE0SCca

Edited May 4, 2022 by Poppa Wheelie
changed "add" to "sum up"

[QF9E]

6 minutes ago, Poppa Wheelie said:

Question for you pros:  What was your process for building your booster stages? 

My process was to first build a 2 stage vehicle with approximately equal dv for both stages (which came to about 20 - 22 tons if I remember correctly), and then to experiment with adding a third stage. For me it's very little science and a lot of trial and error.

That said, I think the best way to save mass in your launch vehicle is to build your payload (i.e., in this case your spacecraft / Mun lander) as light as possible.

[sevenperforce]

I managed an 11.47-tonne solution with a three-stage ascent vehicle where the third stage holds a command chair and is left in LEO to act as the descent vehicle. Munar orbit rendezvous, except that Jeb uses an extra EVA fuel pack to enable an EVA ascent from the munar surface to the command module, which is merely an empty tank with a couple of extra EVA packs in it to enable him to make the burn back to Kerbin. There's a personal parachute for him attached to the third stage.

I've tested all the parts independently but I haven't flown the whole mission yet.

[camacju]

I have some more ideas for mass savings:

-Are heavy aerodynamic exploits (clipping, zero-drag heat shields, etc) allowed?

-Are electric props allowed? (This one I don't see how you could enforce it, as reaction wheels and wings are both allowed)

[sevenperforce]

2 hours ago, camacju said:

I have some more ideas for mass savings:

-Are heavy aerodynamic exploits (clipping, zero-drag heat shields, etc) allowed?

-Are electric props allowed? (This one I don't see how you could enforce it, as reaction wheels and wings are both allowed)

Electric props are not allowed as the challenge says that you can use only monopropellant for propulsion.

There's certainly nothing stopping anyway from doing a heavily-clipped version to see how low they can get it, but it's always going to be in a different class than one that uses proper aero.

[jimmymcgoochie]

Reminds me of this challenge from a couple of years ago:

I might try to dig up the craft files I used then, make some tweaks and give this a go.

[QF9E]

An improvement on my previous attempt, at 10.929 tons including Jeb.

Full report: https://imgur.com/a/aWo9A16

Some highlights:

My craft in the VAB. Overall design is the same as my previous submission, with a 3 stage launch vehicle.

Landed on the Mun. I used a single stage lander, as I found that two of these cylindrical tanks, a command chair and a handful of RCS thrusters have sufficient dv to land on the Mun from Low Kerbin Orbit and make it back to Kerbin.

Back in orbit, on the way back to Kerbin. I ran my craft at less than 100% thrust; that way my attitude control thrusters (one on each corner of the craft) could generate thrust and still have room for attitude adjustment. In all, my craft used 10 of the smallest RCS thrusters in the game: 6 clustered together in the center and 4 on the corners of the craft.

Landing under parachute. I also experimented with landings without parachute. That turns out to be survivable, if you land in the water. But my craft had sufficient dv to take a parachute with me, so I opted to do so as it would make landing easier.

Edited May 6, 2022 by QF9E

[sevenperforce]

4 hours ago, jimmymcgoochie said:

Reminds me of this challenge from a couple of years ago:

I might try to dig up the craft files I used then, make some tweaks and give this a go.

Lol I completely forgot that I already did this challenge 

40 minutes ago, QF9E said:

An improvement on my previous attempt, at 10.929 tons including Jeb.

Full report: https://imgur.com/a/aWo9A16

Some highlights:

What is your mass to LKO?

Edited May 6, 2022 by sevenperforce

[QF9E]

31 minutes ago, sevenperforce said:

What is your mass to LKO?

573 kg for the lander + Jeb with parachute:

• Command chair (50 kg)
• Two cilindrical tanks (2 x 230 kg)
• One cubic Octagonal Strut to act as root part (1 kg)
• 10 Place Anywhere 1 Linear RCS ports (1.3 kg each)
• 1 Kerbal (45 kg)
• 1 Personal parachute (4 kg)

From test flights I know that this lander is able to go from LKO to Munar surface and back to Kerbin. However, on my actual flight I had some 100 m/s dv to spare in my upper stage so I used that to save a bit of lander fuel. When I returned to Kerbin the lander had 19kg of fuel remaining, which amounts to 340 m/s of vacuum dv.

In all, I could have optimized my rocket a little bit further, but at some point it becomes too frustrating to fly because every tiny mistake means the mission is over. So I prefer a bit of margin, if only for my own sanity.

Edited May 6, 2022 by QF9E

[sevenperforce]

15 hours ago, QF9E said:

573 kg for the lander + Jeb with parachute:

• Command chair (50 kg)
• Two cilindrical tanks (2 x 230 kg)
• One cubic Octagonal Strut to act as root part (1 kg)
• 10 Place Anywhere 1 Linear RCS ports (1.3 kg each)
• 1 Kerbal (45 kg)
• 1 Personal parachute (4 kg)

From test flights I know that this lander is able to go from LKO to Munar surface and back to Kerbin. However, on my actual flight I had some 100 m/s dv to spare in my upper stage so I used that to save a bit of lander fuel. When I returned to Kerbin the lander had 19kg of fuel remaining, which amounts to 340 m/s of vacuum dv.

In all, I could have optimized my rocket a little bit further, but at some point it becomes too frustrating to fly because every tiny mistake means the mission is over. So I prefer a bit of margin, if only for my own sanity.

Damn, and I thought I was doing well with 683 kg in LKO. 

I guess it's back to the drawing board.

 

Edited May 7, 2022 by sevenperforce