Roads to Duna: No Moar Boosters (UPDATES!)

[Kergarin]

If I see this right, it is now possible to get more than -100% bonus, which would lead to negative score, which means the heaviest ship with all these bonus will win 

[sevenperforce]

6 hours ago, mk1980 said:

i don't want to re-do an optimzed version of my original mission just with smaller stuff. that would be kinda boring.

currently thinking of a new and (somewhat) different mission profile that involves a separate ascent vehicle and a small rover.

i can see a fairly high potential for bonus stacking in such a mission (thanks to the new rover bonus).

a transfer ship with extra cabins that ends the tour in kerbin orbit is already worth 33%.

bringing 2 separate landers (one that brings the crew and a small rover down, another one that lands unmanned and is used as the ascent vehicle) adds another 33%. i guess the ascent lander could also be shot to duna as a separate launch indpendent of the main ship?

we don't have to worry about full reusability of those landers since we don't aim for elon style this time, so they can be more efficient than an SSTO design that must make it back to the mothership in one piece.

slow climb & old school are easy enough to get and if we roughly standardize the size of the individual modules, we can also get the "consistency" bonus for using the same launcher.

with those stacked bonuses, we're already at 79% which gives us some "wiggle room" for design since individual launches of ~4 tons or less would result in a score roughly on par with current top score.

if we go one step further and also use propulsive landings rather than chutes, that's another 10% bonus, ie. a total bonus of 89%. so the modules could be really big - a little less then 8 tons per module with 89% bonus end at roughly the same score as the current leader.

 

That's about what I'm aiming for as my second entry as well (still cropping and collating the album from my first entry), so I'm interested to see how you pull it off!

Note that a solid-fueled ascent vehicle gives an added boost, but obviously is heavier.

6 hours ago, Kergarin said:

If I see this right, it is now possible to get more than -100% bonus, which would lead to negative score, which means the heaviest ship with all these bonus will win 

How exactly? Enough of the bonuses are mutually exclusive that I don't think you could hit 100%.

[mk1980]

hmm the highest i can think of would be 96% and that would require a bit of sillyness already.

similar to the powered landing mission idea i had , but this time also squeezing a rover in there (large servicebay or something) and somehow design it so the rover can also re-dock and be taken back along with all the other stuff.

well and i guess if you could *somehow* make that thing solid rocket powered without dropping the solid rockets and also bring the empty SRBs back, that could push it to 102%. no idea if it's possible to squeeze all that insanity into one mission, but since the bonus would be 102%, that mission would be completely unrestricted by mass and would always default to 0 score (or actually negative score that would be improved the bigger the mass gets, lol )

don't know if that's feasible at all, but in theory it is.

easiest way to avoid this specific case would be to make the rover automatically rule out elon style, so i don't feel compelled to make a stupid monster mission that lands a rover and brings it back home with an SRB powered ascent vehicle

[sevenperforce]

4 minutes ago, mk1980 said:

hmm the highest i can think of would be 96% and that would require a bit of sillyness already.

similar to the powered landing mission idea i had , but this time also squeezing a rover in there (large servicebay or something) and somehow design it so the rover can also re-dock and be taken back along with all the other stuff.

well and i guess if you could *somehow* make that thing solid rocket powered without dropping the solid rockets and also bring the empty SRBs back, that could push it to 102%. no idea if it's possible to squeeze all that insanity into one mission, but since the bonus would be 102%, that mission would be completely unrestricted by mass and would always default to 0 score (or actually negative score that would be improved the bigger the mass gets, lol )

don't know if that's feasible at all, but in theory it is.

easiest way to avoid this specific case would be to make the rover automatically rule out elon style, so i don't feel compelled to make a stupid monster mission that lands a rover and brings it back home with an SRB powered ascent vehicle

The highest I had come up with was 95%, using Old School, Consistency, Slow Climb, Tongues of Fire, Stayin' Alive, Loop the Loop, Justin Case, A Solid Plan, and Rollin'.

Rollin', Justin Case, and A Solid Plan are all presumed to rule out Elon Style, but I'll make that clearer. Maybe add a list of bonus collisions.

[Kergarin]

1 hour ago, sevenperforce said:

How exactly? Enough of the bonuses are mutually exclusive that I don't think you could hit 100%.

Using the same reusable launch system for all payloads which lands without chutes.

Using old school engines.

Assembling a separate direct ascend vehicle without chutes which has ladders and extra space and carries a rover and later brings it back to kerbin.

Bring the crew in a transfer stage with extra space  plus lander without chutes which later remotely returns to the transfer stage which then remotely returns to kerbin orbit and stays there, while the crew gets back in the separate ascend vehicle which land on kerbin without chutes too.

So everything including the rover and lander is reusable and returnees 

And I think it gives:

• On Tongues of Fire. Use no chutes; propulsive landings on both Duna and Kerbin. 10%decrease in highest payload mass.
• Old School. No nukes or ions. 3% decrease in highest payload mass.
• Brute Force. Assemble a Direct Ascent vehicle in LKO; no ISRU, no propellant transfer, no Duna orbit rendezvous. 12% decrease in highest payload mass.
• Slow Climb. Put ladders on your vehicles so you don't have to jetpack around on the Duna surface. 4% decrease in highest payload mass.
• Elon Style. Make the whole system fully reusable without using nukes, ions, or airbreathers. 25% decrease in highest payload mass.
• Stayin' Alive. Bring extra living space (at least one extra seat per Kerbal) for the transfer to and from Duna. 18% decrease in highest payload mass.
• Loop The Loop. Make your transfer vehicle a fully-reusable solution that can brake back into Kerbin orbit and be used again for the next trip. 15% decrease in highest payload mass.
• Consistency, Good Sir. Make all of your launches with the exact same launch vehicle. 6% decrease in highest payload mass.
• Justin Case. (NEW) Provide your crew with a separately-landed ascent vehicle as a reliable way to get off Duna (inspired by The Martian). 18% decrease in highest payload mass.
• They See Me Rollin'. (NEW) Bring a rover for your crew to get around Duna. 15% decrease in highest payload mass. 

Which is 126%? 

Even if I exclude brute force, because parallel to the direct ascend vehicle there is a second ship, which docks to the transfer stage before it returns, it's still 114?

Edited September 11, 2017 by Kergarin

[sevenperforce]

1 minute ago, Kergarin said:

Using the same reusable launch system for all payloads which lands without chutes.

Using old school engines.

Assembling a separate direct ascend vehicle without chutes which has ladders and extra space and carries a rover and later brings it back to kerbin.

Bring the crew in a ransfer stage plus lander without chutes which later remotely returns to the transfer stage which then remotely returns to kerbin orbit and stays there, while the crew gets back in the separate ascend vehicle which land on kerbin without chutes too.

So everything including the rover and lander is reusable and returnees 

And I think it gives:

• On Tongues of Fire. Use no chutes; propulsive landings on both Duna and Kerbin. 10%decrease in highest payload mass.
• Old School. No nukes or ions. 3% decrease in highest payload mass.
• Brute Force. Assemble a Direct Ascent vehicle in LKO; no ISRU, no propellant transfer, no Duna orbit rendezvous. 12% decrease in highest payload mass.
• Slow Climb. Put ladders on your vehicles so you don't have to jetpack around on the Duna surface. 4% decrease in highest payload mass.
• Elon Style. Make the whole system fully reusable without using nukes, ions, or airbreathers. 25% decrease in highest payload mass.
• Stayin' Alive. Bring extra living space (at least one extra seat per Kerbal) for the transfer to and from Duna. 18% decrease in highest payload mass.
• Loop The Loop. Make your transfer vehicle a fully-reusable solution that can brake back into Kerbin orbit and be used again for the next trip. 15% decrease in highest payload mass.
• Consistency, Good Sir. Make all of your launches with the exact same launch vehicle. 6% decrease in highest payload mass.
• Justin Case. (NEW) Provide your crew with a separately-landed ascent vehicle as a reliable way to get off Duna (inspired by The Martian). 18% decrease in highest payload mass.
• They See Me Rollin'. (NEW) Bring a rover for your crew to get around Duna. 15% decrease in highest payload mass. 

Which is 126%? 

Brute Force requires that the ascent stage be stacked on top of the descent stage, which stacked on top of the transfer stage. The rules also indicate that if you use a separate ascent vehicle, you need to have a rover to take the crew from the descent vehicle to the ascent vehicle. 

I updated the OP with a list of conflicts.

[Kergarin]

5 minutes ago, sevenperforce said:

Brute Force requires that the ascent stage be stacked on top of the descent stage, which stacked on top of the transfer stage. The rules also indicate that if you use a separate ascent vehicle, you need to have a rover to take the crew from the descent vehicle to the ascent vehicle. 

I updated the OP with a list of conflicts.

Sorry, had just edited the post while you were answering. I have taken brute force out. But it is still 114%.

My plan includes a rover, which is later returned to kerbin or kerbin orbit. So having a rover doesn't seem to exclude anything else?

Edited September 11, 2017 by Kergarin

[sevenperforce]

2 minutes ago, Kergarin said:

Sorry, had just edited the post while you were answering. I have taken brute force out. But it is still 114%.

My plan includes a rover, which is later returned to kerbin or kerbin orbit. So having a rover doesn't seem to exclude anything else?

Note that I updated the OP to specify that Rollin' conflicts with Elon Style. So there's no use trying to reuse the rover. Justin Case also specifically conflicts with Elon Style. Using a rover and a separate ascent vehicle gives a combined bonus of 33%, which beats Elon Style's 25%.

You can bump it up a bit more if the Ascent Vehicle is solid-fueled. I'm working on a solid MAV now.

[Laie]

10 hours ago, sevenperforce said:

I'll take the LES bonus off (even though I did it on my own rocket). It does restrict launch types somewhat, though. Not going to remove the ladder one, just because people have already gotten bonuses for it. 

I'm a bit torn on that one. LES gave things a nice touch, but yeah... as soon as sepratrons are no longer sufficient, it becomes a problem. Standard SRBs are heavy. Some "solutions" I came up with were outright ridiculous.

About ladders, on my lander I had trouble during entry because they cause a lot of drag. I guess it needs to be a small ship with off-center ladders to feel it, though.

[Kergarin]

8 minutes ago, sevenperforce said:

Note that I updated the OP to specify that Rollin' conflicts with Elon Style. So there's no use trying to reuse the rover. Justin Case also specifically conflicts with Elon Style. Using a rover and a separate ascent vehicle gives a combined bonus of 33%, which beats Elon Style's 25%.

You can bump it up a bit more if the Ascent Vehicle is solid-fueled. I'm working on a solid MAV now.

Ok. So I'm forced to leave the rover and separate lander back at duna, and also returning them both doesn't give Elon Style?

[sevenperforce]

15 minutes ago, Kergarin said:

Ok. So I'm forced to leave the rover and separate lander back at duna, and also returning them both doesn't give Elon Style?

The point of having an crew ascent vehicle separate from the crew lander is that your means of leaving Duna is assured before you land. So, if you come down hard, crack a landing leg, and crush an engine on touchdown, it's not a death sentence. However, with this approach, it doesn't really make sense to have your crew lander also be an ascent vehicle, because you have a separate one. If you use a separate ascent vehicle, you leave the landing vehicle behind.

[sevenperforce]

So I thought I should probably actually post my first mission before I finish my second one!

Here's what the transfer vehicle was planned to look like in orbit (yes, I forgot you can set radial decouplers to allow crossfeed):

It's tidily split into four dockable segments:

Spoiler

Duna Ascent Stage Core (plus docking assembler).

Parallel stages for Duna Ascent.

Transfer stage with drop tanks.

Crew capsule and return stage.

All used the same exact ascent vehicle (with slightly different fairings, and an LES on the final, crewed launch).

All four launches (I could have launched each component empty and sent up a refueling mission, but then I couldn't claim Brute Force).

Ascent and docking highlights:

Spoiler

First launch progressing nicely.

Staging.

Fairing sep.

Circularized.

Payload deployed.

Deorbiting upper stage.

Here's what she looks like in orbit!

Timing the second stage ascent for ideal intercept.

Nominal staging.

Nice intercept.

Fairing separation. Note that I had to mount the parallel stages backwards on the upper stage.

Burning to match velocities.

Using the vehicle already in orbit for docking approach.

Starting to slide in. The monoprop tanks act as guides for lining up the docking port more easily.

Docked!

Undocking the upper stage of the LV.

Deorbiting.

Transfer module on its way up.

If stock KSP had "standard" fairings, I would totally have made it a bonus to use not only the exact same launch vehicle, but the exact same fairings. That would have made design a bit more challenging.

Got a lot of practice with rendezvous launches.

Because the drop tanks are different sizes, it does end up looking a little cockeyed.

Matching orbital velocity.

This should be close enough for using RCS for the rest of everything.

Closing.

Docked!

Finally, setting up for the rendezvous with the manned launch.

Limiting thrust so as to spare my poor Kerbonauts the high-gees.

Separation.

Blowing the fairing and LES.

Looks a little like an oversized Gemini capsule with the chutes and monoprop tank up top.

Will use Intersect 2 to rendezvous.

Almost there.

Heading for docking approach on RCS.

Solar panels on my unmanned assembly got blocked, so I lost power. As a result I had to do the docking solely with the manned capsule...not that it was too hard, but I couldn't point the unmanned assembly or anything.

Almost there!

And here we are in orbit, ready to head to Duna!

Warped for a while, and set up the transfer window...

We're off!

Heading to Duna:

Spoiler

Watching my drop tanks closely. I ended up making this WAY overpowered.

First drop tanks away.

Raising apoapsis bit by bit...

Almost there.

That should do it!

Lowering Duna periapsis while I still have my nuke.

Dropping the transfer stage (it was still about half full).

Lowered periapsis a bit more with RCS.

Coming in, I set Ike as my target so I could correct inclination.

Got inclination to a more reasonable point.

RCS to lower periapsis.

Inside the atmosphere! I actually dropped it to around 13 km.

Here goes nothing:

Spoiler

Expecting some heat.

I put it into a pretty rapid spin with reaction wheels in the hopes of maintaining retrograde attitude.

This did not work.

Thankfully, I didn't lose anything, though it did get toasty.

Captured and on an impact trajectory.

First drogue out. I don't want to jettison the heat shield yet, lest I collide with it.

All chutes open, heat shield jettisoned.

Landing legs down.

Braking burn.

Zeroing velocity.

Landed!

Bill getting out to repack the chutes. I skipped the ladders, obviously.

On Duna:

Spoiler

Gotta get these stowed for the entry at Kerbin.

Some EVA activities.

Woot woot!

Good to know for ISRU, right?

Couldn't resist.

Everybody hanging out on Duna.

Back in the capsule.

Liftoff!

Ascent and homeward journey:

Spoiler

Dropping tanks.

Dropping more tanks.

Burning through as much monopropellant as I can, to lower mass.

Almost there.

Circularizing on remaining monoprop.

Just a little bit of fuel left in the ascent stage.

Warping around to get a transfer window.

Transfer set up.

Burning off remaining monoprop along with fuel in ascent stage.

Explosive decoupling FTW!

Ran into Ike SOI, like an idiot.

Got to a Kerbin intercept, anyway.

Lowering that periapsis.

Already corrected inclination, now burning radial-in to lower periapsis into atmosphere.

Almost home!

Spoiler

Burning off remaining fuel as I wait for my tank to blow.

Aaaand there it went.

Coming back up out of the atmosphere.

Lowering periapsis a little further at apoapsis.

Second pass.

Chutes out!

Dropped the heat shield, though it really wasn't necessary.

Burning off remaining monoprop.

Splashdown!

Made it back safe.

So, let's see here. Heaviest launch was 11.745 tonnes (the totally overpowered crew module), I earned the Brute Force bonus, making my score 10.3356. Yuck!

Edited September 12, 2017 by sevenperforce

[mk1980]

 

1 hour ago, sevenperforce said:

was that a retrograde reentry into kerbin atmosphere? looks like it on that image.

nice mission! i liked the tree-like mid section where the terriers and tanks are separate from the fuel tank that is moved in between them. that's some orbital precision maneuvering

[sevenperforce]

1 minute ago, mk1980 said:

was that a retrograde reentry into kerbin atmosphere? looks like it on that image.

nice mission! i liked the tree-like mid section where the terriers and tanks are separate from the fuel tank that is moved in between them. that's some orbital precision maneuvering

Having the monoprop tanks in the center helped with alignment! Once I got it lined up, it slid right in.

Pretty much all the stages were WAY overpowered, which is why I was so ridiculously overmass compared to everybody else.

And yeah, it was a Kerbin-retrograde reentry, which explains why my tank blew on the aerocapture.

[mk1980]

trying to figure out a way to make the duna ascent vehicle solid rocket powered, able to land without chutes or wings and small enough. no luck so far.

got one to the ground without breaking important stuff. can also get it back into some sort of ascent trajectory, but not enough fuel to make it. 

https://imgur.com/a/aJ3op

not sure if "partial" SRB launch is enough for the bonus anyway. i packed a pair of fleas on the vehicle and they push it but to ~20 km (at which point the surface speed meter auto-switches to orbit speed), but that's about it. to get further, i'd have to bring something even heavier. a pair of hammers could shoot the capsule to orbit, but then it will probably mass something like 8 tons or more. don't remember if the projected bonus for that mission profile was high enough to improve the current top score with such heavy machinery.

 

[sevenperforce]

1 hour ago, mk1980 said:

trying to figure out a way to make the duna ascent vehicle solid rocket powered, able to land without chutes or wings and small enough. no luck so far.

got one to the ground without breaking important stuff. can also get it back into some sort of ascent trajectory, but not enough fuel to make it. 

https://imgur.com/a/aJ3op

not sure if "partial" SRB launch is enough for the bonus anyway. i packed a pair of fleas on the vehicle and they push it but to ~20 km (at which point the surface speed meter auto-switches to orbit speed), but that's about it. to get further, i'd have to bring something even heavier. a pair of hammers could shoot the capsule to orbit, but then it will probably mass something like 8 tons or more. don't remember if the projected bonus for that mission profile was high enough to improve the current top score with such heavy machinery.

I've got a Duna Ascent Vehicle that's solid-fueled and lands with a liquid-fueled skycrane...it'll mass just over 6 tonnes. I've got a Tongues Of Fire one-way lander that's even lighter. Just trying to get the rover to work properly, now.

Remember that it's ok to put command seats on your ascent vehicle as long as it still docks with the orbiter -- no Watneying up.

 

Edited September 12, 2017 by sevenperforce

[mk1980]

another attempt. geting closer, but really huge now.

https://imgur.com/a/DdioZ

good to know that the ascent vehicle can have command seats. that should make things a lot easier the only difficulty with the SRBs is that they are really heavy and you need quite a lot to shoot 2 lander cans to orbit. i guess a single flea would be almost enough to get the near massless command seats up.

not sure about the other bonuses, though. the original lander remains on the duna surface, so the ascent vehicle is also the part that eventually has to land on kerbin, isn't it? 

also, the command seats probably don't count for the 2 seats per kerbal bonus, so the transfer ship will require 6 seats (ie probably 3 mk1 cabins ).

[sevenperforce]

7 minutes ago, mk1980 said:

another attempt. geting closer, but really huge now.

https://imgur.com/a/DdioZ

good to know that the ascent vehicle can have command seats. that should make things a lot easier the only difficulty with the SRBs is that they are really heavy and you need quite a lot to shoot 2 lander cans to orbit. i guess a single flea would be almost enough to get the near massless command seats up.

not sure about the other bonuses, though. the original lander remains on the duna surface, so the ascent vehicle is also the part that eventually has to land on kerbin, isn't it? 

also, the command seats probably don't count for the 2 seats per kerbal bonus, so the transfer ship will require 6 seats (ie probably 3 mk1 cabins ).

I do not believe the Flea would be enough to make orbit, not once you add Kerbals to the command seats. In order to earn the bonus, it actually needs to reach stable Duna orbit, though I would recommend throwing some RCS on there so you can dock it to a waiting orbiter, and then using the orbiter to head home. 

This approach does require a Kerbin lander which is separate from the Duna lander and Duna ascent vehicle, but there are ways of pulling that off.

You are correct that command seats do not count for the 2 seats per kerbal bonus.

[mk1980]

i doubt i will be able to get the ascent stage to an orbit that is anywhere near that of the mothership with the SRBs. might use a hammer with thrust limiter that burns long enough get above 50km and can also push the PE out of the atmosphere. or maybe a flea that just pushes the AP up and a second stage made of separatrons (they are also SRBs, after all) that push the PE up once the capsule reaches AP.

i guess i would still put a small LF engine on the ascent vehicle to maneuver it towards the mothership once it reached *some* orbit with the SRBs. doesn't have to be much. maybe an oscar tank and an ant engine or something along that line. would be much cheaper (mass-wise) than maneuvering the whole mothership to a rendezvous with the ascent vehicle.

will have to think of a clever solution for the kerbin lander. i guess it would be possible to cannibalize the mothership and have some of it's extra crew capacity actually being the kerbin lander, but that would (imo) violate the whole "transfer ship ends trip in orbit ready for next mission" idea.

does the kerbin lander need a proper crew capsule or can we also use command seats? that would make it a whole lot easier, of course

[sevenperforce]

35 minutes ago, mk1980 said:

i doubt i will be able to get the ascent stage to an orbit that is anywhere near that of the mothership with the SRBs. might use a hammer with thrust limiter that burns long enough get above 50km and can also push the PE out of the atmosphere. or maybe a flea that just pushes the AP up and a second stage made of separatrons (they are also SRBs, after all) that push the PE up once the capsule reaches AP.

i guess i would still put a small LF engine on the ascent vehicle to maneuver it towards the mothership once it reached *some* orbit with the SRBs. doesn't have to be much. maybe an oscar tank and an ant engine or something along that line. would be much cheaper (mass-wise) than maneuvering the whole mothership to a rendezvous with the ascent vehicle.

will have to think of a clever solution for the kerbin lander. i guess it would be possible to cannibalize the mothership and have some of it's extra crew capacity actually being the kerbin lander, but that would (imo) violate the whole "transfer ship ends trip in orbit ready for next mission" idea.

does the kerbin lander need a proper crew capsule or can we also use command seats? that would make it a whole lot easier, of course

 Both Kerbin and Duna landers need a proper crew capsule. However, the crew capsule can be used as extra crew capacity.

[Human Person]

In my opinion, Elon Style would be also to build a very large ship for 100 or more tourists.

May I suggest to do the scoring per Kerbal, so if you bring 3 Kerbals you divide your final score by 3 and if you bring 100 Kerbals, you divide your final score by 100?

[sevenperforce]

44 minutes ago, Physics Student said:

In my opinion, Elon Style would be also to build a very large ship for 100 or more tourists.

May I suggest to do the scoring per Kerbal, so if you bring 3 Kerbals you divide your final score by 3 and if you bring 100 Kerbals, you divide your final score by 100?

I thought about adding a per-kerbal bonus, but there's no good way to make it balanced.

[mk1980]

well it could work as a separate multiplier as @Physics Student suggested.

basically a "scaling modifier" for the whole mission. so a mission with 3 kerbals that reaches a given score and another mission that has 6 kerbals and uses the same mission profile with twice the total mass gets the same score.

that would likely bias larger, upscaled missions, though.

some parts just have better mass ratios if you scale them up. a 2 man lander pretty much has to use 2 lander cans, but if you double the scale, you could use the 4 man MK2 passenger cabin that has an even lower mass per kerbal. or if you upscale it again and send 16 kerbals, you can use the mk3 cabin that has 16 seats at 6.5 tons (or something in that range).

or the engines - if you make it big enough it makes sense to use a dart (aerospike) rather than a spark. the dart has 10 times the mass and 10 times the thrust, but much better Isp.

stuff like that.

on the other hand, that would encourage some large scale mission, which could be fun to design (or to watch)

[Human Person]

9 minutes ago, mk1980 said:

that would likely bias larger, upscaled missions, though.

some parts just have better mass ratios if you scale them up. a 2 man lander pretty much has to use 2 lander cans, but if you double the scale, you could use the 4 man MK2 passenger cabin that has an even lower mass per kerbal. or if you upscale it again and send 16 kerbals, you can use the mk3 cabin that has 16 seats at 6.5 tons (or something in that range).

or the engines - if you make it big enough it makes sense to use a dart (aerospike) rather than a spark. the dart has 10 times the mass and 10 times the thrust, but much better Isp.

stuff like that.

on the other hand, that would encourage some large scale mission, which could be fun to design (or to watch)

Yes, exactly. It's on @sevenperforce to decide if he wants to allow this for his challenge.

also to be considered: 

- Landing much larger Craft will be harder and parashutes will help you less (especially on Mars).

- IRSU becomes a reasonable option (IRSU equipment is very heavy)

 

The mission I have in mind would be an Elon-Style mission with purely propulsive landings and IRSU for oxidizer only.

[sevenperforce]

6 minutes ago, Physics Student said:

Yes, exactly. It's on @sevenperforce to decide if he wants to allow this for his challenge.

also to be considered: 

- Landing much larger Craft will be harder and parashutes will help you less (especially on Mars).

- IRSU becomes a reasonable option (IRSU equipment is very heavy)

The mission I have in mind would be an Elon-Style mission with purely propulsive landings and IRSU for oxidizer only.

Yes, I'd like a way to scale it up to the point that ISRU is reasonable. Not opposed to the idea. But, as mk1980 said, going much bigger gives you parts with far better mass ratios, which would greatly bias against small vehicles.

One option is to provide diminishing returns. If you take more than 3 kerbals in all, divide your final score (after all bonuses) by half of the number of extra kerbals you take. So if you take the minimum (3), there's no bonus. If you take 6, then you can divide your final score by (6-3)/2 or 1.5. If you take 20, then you divide your final score by (20-3)/2 or 8.5. If you take 100, you divide your final score by (100-3)/2 or 48.5. This would also need to require that at least 2/3 of your total crew actually lands on Duna.

Another option would be if I modified Stayin' Alive so that you only need 3 additional seats in total; this rewards players with more Kerbals because they can get Stayin' Alive without having to double the size of their transfer vehicle.

Would either (or both) of those changes be enough to incentivize larger vehicles without making them too overpowered?

Alternately, I could just create a separate tier/leaderboard for an "over 20 kerbals" category that allows you to divide your final score by half the number of kerbals you take.