Artemis - Duna Mission Architecture

[jinnantonix]

Thanks @camacju,  I really appreciate your effort. It helps to get the rules straight.  The lander cans are not re-entry vehicles, so cannot be used in atmospheric flight.  Also, after landing on Kerbin, the orbital craft only has 4 seats, and 8 seats must be maintained.  I have clarified in the rules.

With the extra 4 seats and heavy pods, plus relays and probes (which you didn't include) I am getting a 40% higher initial setup including mining rig, and about $25k per resupply.  The difference is that with mining, there is continued fuel supply, but without an additional Rossum is needed every 5 missions.  So I am going to call it a draw. 


 

 

[QF9E]

I've been quietly following this fascinating discussion, and I've come to the same conclusion as @camacju. Although I prefer using the humble Terrier engine - same thrust as the NERV, much lighter and a price that is almost completely negligible. With that in mind I built my own architecture. I copied @camacju's hab design and simplified it a bit, hope you don't mind. I used 4 Mk1 Capsules as entry vehicle, stacked on top of the hab, which I used as landing gear substitute as well (the thing has a 40 m/s impact tolerance, which is madness, in my opinion).

Note: my architecture does not include the space station, as it isn't really needed for an all-up mission. Like @camacju I also did not include the probes and relays. If desired I think I can do another launch of the same rocket design, with probes and relays in lieu of the entry vehicle and a repurposed Duna hab as space station.

Anyway, here's my rocket:

My rocket in the VAB. This is an all-up mission with no component reuse whatsoever. Cost for a single flight is $27543.

All the components. Top to bottom: Fuel tank for the Trans-Duna burn (will be discarded afterwards), fuel tank for the Trans-Kerbin burn (will be left in low Duna orbit), entry vehicle / tug, hab, 2nd stage, 1st stage.

I've not yet flown a full mission, but testing so far indicates:

1. The 1st and 2nd stages are more than sufficient to reach LKO (with about 300 m/s left)
2. The Trans-Duna tank suffices for reaching Duna's orbit
3. Duna descent, landing and ascent all work, although ascent propellant is a bit tight
4. Entry vehicle will withstand Kerbin entry from low Kerbin orbit

I haven't tested Kerbin aerocapture, but I am quietly optimistic, as you don't need to shed much speed at all to get into a highly elliptical Kerbin orbit when returning from Duna. I'll keep you updated on my progress.

As to why this compares favourably to Munar ISRU: I think it is a combination of two factors:

1. Compared to the real world it is trivially easy to do missions like this in KSP. Yesterday I did a direct ascent mission to Duna with a 3-man crew, using the Mk1-3 capsule for less than $23000
2. RTGs and fuel cells appear to be much more expensive in KSP compared to the real world. For the price of the mission I did yesterday you can barely buy 1 RTG in KSP, which sounds off to me.

My suggestion would be to do this challenge in a modded solar system. A scaled-up version of the stock system would do nicely, in my opinion. Although if you insist on stock parts only, RSS would be a bit too much.

Edited July 25, 2021 by QF9E

[The_Nico]

Hello I liked the challenge idea and I'm working on stock Starship replicas (I call them Storship) that might fit the challenge.  If they fit I will be able to recover the 100% of the rockets, including the 1st stage. I would have to make a cargo variant to deploy the satellites and the habitat modules.

Storhip Crew and Storship tanker in LKO transfering fuel

https://kerbalx.com/The_Nico/Storship-Crew-Block-1b

https://kerbalx.com/The_Nico/Storship-Tanker-Block-1

Storship Fuel Factory (WIP). I guess I will have to remove the solar panels on this one.

Spoiler

Belly reentry

Belly reentry

Skydiving

Landed after belly flop maneuver

 

 

The idea will be to put a Tanker in Munar orbit and use the Fuel Factory to fill it with fuel mined from the Mun. Then it will be another pair Tanker/Factory in Duna's orbit that will make the fuel from Duna's surface.

The mission:

- Launch 2 Tankers and 2 Fuel Factories. One Pair goes to the Mun, The other goes to Duna.

- When the tankers a full, launch the crew module and a Tanker. In LKO Crew will make it's first refuel and then go to the moon.

- Crew will refuel from the tanker on Mun's orbit, then go to Duna.

- In Duna's orbit, Crew will refuel again to be able to land and get back into orbit. If needed, another refuel will be performed in Duna's orbit and then back to Kerbin.

- Storship Crew will land in Kerbin and can be reused.

- For the subsequent missions the same Storship Crew can be used.

- If necessary Tankers and Factories can return and land in Kerbin to reduce costs.

 

If this fits, the costs will be the fuel plus the satellites and the habitat modules

 

 

 

 

[QF9E]

Very nice! I've played with the idea of using lots of airbrakes as Starship flaps, but I haven't been successful so far. Are the airbrakes sufficiently heat-resistant to withstand aerocapture when returning from Duna?

[The_Nico]

12 minutes ago, QF9E said:

Very nice! I've played with the idea of using lots of airbrakes as Starship flaps, but I haven't been successful so far. Are the airbrakes sufficiently heat-resistant to withstand aerocapture when returning from Duna?

I don't think they will survive if fully deployed on reentry. I'm using them mostly as attitude control. The increase in drag while belly diving/reentry seems to payoff. I started exploring this idea because I make a lifter so big, that I couldn't stop it with airbrakes during reentry.

I have some ideas to increase drag during aerocapture, but I have to test them.

[jinnantonix]

1 hour ago, QF9E said:

I've been quietly following this fascinating discussion, and I've come to the same conclusion as @camacju
 

As to why this compares favourably to Munar ISRU: I think it is a combination of two factors:

1. Compared to the real world it is trivially easy to do missions like this in KSP. Yesterday I did a direct ascent mission to Duna with a 3-man crew, using the Mk1-3 capsule for less than $23000
2. RTGs and fuel cells appear to be much more expensive in KSP compared to the real world. For the price of the mission I did yesterday you can barely buy 1 RTG in KSP, which sounds off to me.

 

@QF9E I  agree that direct missions (minus space station/fuelling infrastructure / relays and comms) is economically competitive when modelled in 'stock KSP, for the reasons you state.   KSP isn't a perfect model to the real world.  I am reluctant to start reaching into mods, because it will increase complexity, raise more questions than it answers, and limit participation.

I would add that any genuine attempt at Duna exploration would involve a two tiered approach, with autonomous equipment delivery, and an entirely separate system, highly safety oriented, for human delivery.  For example, humans returning from Duna would definitely do a direct re-entry in robust re-entry vehicle with heat shields, rather than a vehicle aero capture.

Regardless, the primary concept behind the challenge is to see how to get an Artemis style Mun ISRU architecture as efficient as possible.  The comparison with the direct approach is useful in developing the rules so I appreciate the feedback.

[jinnantonix]

1 hour ago, The_Nico said:

If necessary Tankers and Factories can return and land in Kerbin to reduce costs.

If this fits, the costs will be the fuel plus the satellites and the habitat modules

 

Thanks @The_Nico I really like the idea of using Starship replicas as you have suggested. 

Please note that there is no recovery of  costs for craft landing at Kerbin, it is assumed that re-entry makes them uneconomical for re-use.  The focus is on re-usability of infrastructure once launched, with minimisation of expendables -  being launch vehicles and re-entry capsules.

[QF9E]

55 minutes ago, jinnantonix said:

I am reluctant to start reaching into mods, because it will increase complexity, raise more questions than it answers, and limit participation.

Understandable. How about making the mission harder then, by targeting a different body? If you want another body with an atmosphere that is a bit harder than Duna, Laythe could be viable.  I'd be willing to do this challenge on Eve as well, but that might be too much for some.

[jinnantonix]

7 minutes ago, QF9E said:

Understandable. How about making the mission harder then, by targeting a different body? If you want another body with an atmosphere that is a bit harder than Duna, Laythe could be viable.  I'd be willing to do this challenge on Eve as well, but that might be too much for some.

If you want it harder, then my inclination is toward rules like :

• no aerobraking for any craft with Kerbals aboard, except Duna direct re-entry at Kerbin.  (I am seriously considering this one)
• adjust settings to increase sensitivity to re-entry heating
• set part pressure and G-force limits

Thoughts?

 

 

[QF9E]

3 hours ago, jinnantonix said:

no aerobraking for any craft with Kerbals aboard, except Duna direct re-entry at Kerbin.

If you mean "no aerobraking in Kerbin's atmosphere except when doing a direct re-entry" then I'm all for it. I think endless aerobrake passes to avoid overheating because you skimped on heat shields is more than a bit gamey as it is. I also find it really boring to fly a mission like that. That said, would a skip re-entry still be allowed, where you briefly go out of Kerbin's atmosphere? Apollo could do a skip re-entry (but some googling indicates it was never used), and the Soviet Zond did use a skip re-entry when coming back from the Moon.

I do hope, however that you don't mean to forbid aerobraking at Duna. The way it's worded confused me at first, as it can be read to preclude the use of aerobraking at Duna as well. The different interpretations arose because it wasn't clear to me whether "at Kerbin" is part of the "except" clause or pertains to the rule as a whole:

(no aerobraking for any craft with Kerbals aboard, except Duna direct re-entry) at Kerbin.     [i.e., the rule only pertains to Kerbin, no limitation is put on aerobraking at Duna]

vs.

no aerobraking for any craft with Kerbals aboard, (except Duna direct re-entry at Kerbin.)    [i.e., the rule forbids aerobraking in all circumstances, except when doing a direct re-entry at Kerbin]

If that makes sense.

 

 

I've never really played with anything other than the default settings before, so I cannot really comment on the re-entry heating, pressure and g-force settings. Will definitely experiment with setting these to more realistic values in the future though.

[camacju]

Wow, relay probes are really expensive. Good thing my launcher has enough margin that they can hitch a free ride. Even cutting out all possible costs from the other modules, the main mission is 80k funds.

I got the resupply missions quite a bit cheaper however - 16578 funds. DLC parts are pretty good for saving costs.

Cost for three missions: 113132 funds

Edited July 25, 2021 by camacju

[jinnantonix]

2 hours ago, camacju said:

Cost for three missions: 113132 funds

Any chance you can show the images with the fairings deleted?

Note, you need to drop a probe onto Duna with each mission.  Also I added a requirement that Kerbals returning to Kerbin must directly re-enter the atmosphere.  You no longer need ore.
 

[camacju]

1 hour ago, jinnantonix said:

Any chance you can show the images with the fairings deleted?

I forgot about that. Here you go:

Large fairings are actually pretty expensive. Three Duna missions total 108.7k funds now. (And with that, I think I'm definitely under QF9E's Terrier based architecture, assuming a fourth launch is needed to put up probes and the orbiting space station)

1 hour ago, jinnantonix said:

Note, you need to drop a probe onto Duna with each mission

That won't be too difficult. The three probes are really small so they can hitch a ride wherever - I have enough margin for it. I'd just move one probe onto each of the two resupply missions at no change to total cost

1 hour ago, jinnantonix said:

You no longer need ore.

That will barely make a difference to my mission - the Nerv is pretty efficient anyway so mass ratio won't change much.

1 hour ago, jinnantonix said:

Also I added a requirement that Kerbals returning to Kerbin must directly re-enter the atmosphere.

That won't be hard to do  - I was well within heat margins even with the lander cans so a deeper aerobrake will be fine. I'll just need to use a little more fuel to adjust the trajectory of the tug and orbital habitat.

Edited July 26, 2021 by camacju

[QF9E]

I've tested the comms requirements, and I am now wondering why you specified the RA-2 as it has insufficient range to reach Kerbin unless Duna is close by. The RA-15 and RA-100 have sufficient range for continuous coverage, except for the short period that the Sun is in the way. I don't think a real mission would have a radio blackout for something like 75% of the time. Or am I missing something related to launch windows that ensures that whenever there's Kerbals on the surface the distance between Kerbin and Duna is small?

[camacju]

I think it's just that the RA-2 is a small relay antenna

[The_Nico]

On 7/25/2021 at 4:06 PM, jinnantonix said:

If you want it harder, then my inclination is toward rules like :

• no aerobraking for any craft with Kerbals aboard, except Duna direct re-entry at Kerbin.  (I am seriously considering this one)
• adjust settings to increase sensitivity to re-entry heating
• set part pressure and G-force limits

Thoughts?

 

 

How about nerfing the engines thrust? The idea will be to make a list with the thrust limit for each engine. Any engine can be used, but with this limitations. Example KS-25 at 50% thrust, Poodle at 75% and so on.

[jinnantonix]

23 hours ago, QF9E said:

I've tested the comms requirements, and I am now wondering why you specified the RA-2 as it has insufficient range to reach Kerbin unless Duna is close by. The RA-15 and RA-100 have sufficient range for continuous coverage, except for the short period that the Sun is in the way. I don't think a real mission would have a radio blackout for something like 75% of the time. Or am I missing something related to launch windows that ensures that whenever there's Kerbals on the surface the distance between Kerbin and Duna is small?

Good point, I only briefly tested the RA-2 and it worked.  But i didn't take into account Kerbin-Duna distance.  I will mandate 3 x RA-15 as a minimum.

Edited July 27, 2021 by jinnantonix

[jinnantonix]

Here is an example of the aesthetics standard required for full points.

 

Edited July 27, 2021 by jinnantonix

[jinnantonix]

9 hours ago, The_Nico said:

How about nerfing the engines thrust? The idea will be to make a list with the thrust limit for each engine. Any engine can be used, but with this limitations. Example KS-25 at 50% thrust, Poodle at 75% and so on.

Not sure why that would be a good thing to do.  

[jinnantonix]

@camacju I have set the rules so that direct to Duna entry is valid, you lose 8 points by not building the Mun mining facility, but this may be offset by 80k lower costs.  This hopefully accounts for the unusually high cost of ISRU in KSP.  The only thing that I would need to see is that the resupply missions are fully sustainable, and include all of the fuel needed for that mission, so that the same resupply launch could be used for additional  subsequent missions.

 

Edited July 27, 2021 by jinnantonix

[The_Nico]

14 hours ago, jinnantonix said:

Not sure why that would be a good thing to do.  

The reasoning will be that a worse engine will impact the size of the rocket and the amount of fuel needed. Worse engine, bigger rocket, more fuel, more costs. Maybe it can reach a point that sending a direct rocket to Duna, will be equally or more expensive than having a fuel factory on the Mun.

Or maybe I'm overthinking.

[QF9E]

Would the aesthetics of the places you go to also figure in the overall score? I found this peak of eternal light near the lunar south pole from which you have a magnificent view of Kerbin, as well as the large crater just below it. It would be an excellent spot for a relay station, to keep in touch with the mining rig doing its thing in the eternal darkness below (which also happens to have an excellent ore concentration in my campaign).

I dub thee Kackleton Crater (https://en.wikipedia.org/wiki/Shackleton_(crater)). About 89 degrees south, 52 degrees east on the munar surface.

Prototype communications rover on top of the peak. The boulder marks the highest point. That slot on the opposite site of the crater wall acts as a funnel for sunlight, with a beam of light sweeping across the crater floor once a week. There's not even a need for a movable dish antenna as Kerbin remains stationary in the munar sky.

By the way, the interior of Kackleton crater has some large flat areas suitable for landing, but also a bunch of ridges running north to south through the crater. It's a difficult and eerie place explore.

Edited July 28, 2021 by QF9E

[jinnantonix]

Any more comments before I post this as an official challenge?

[jinnantonix]

44 minutes ago, QF9E said:

Would the aesthetics of the places you go to also figure in the overall score?

Obviously, no.  I added the aesthetics score to address the problem that the proposed low cost entries just looked ridiculous.  I am hoping for this challenge to really think about what a real mission in 2030 might look like.

[QF9E]

1. Can you have multiple orbital craft, for instance an additional one in Mun or Duna orbit, to also be able to do fuel transfers at Duna?

2. Would it be allowed to launch raw ore from the Munar surface and refine it in orbit, with the help of solar power)?

2. How will points for aesthetics be judged for vehicles with multiple roles? For instance, my current plan uses the same craft as the Duna transfer vehicle (with an additional transfer stage), Duna lander and re-entry vehicle.