Lightest Mun Lander (+return) you can build w/o upgrading Buildings

[thyriel]

As i liked the idea of the thread so much i would like to open up a challenge here:

http://forum.kerbalspaceprogram.com/threads/103878-18t-%28or-less%29-Returnable-Manned-Mun-Lander

Goal:

Build a rocket capable of landing on the mun and returning to kerbin that does not need any upgraded buildings. So it's limited to:

- 30 Parts

- 20m Height

- 15m Width

- Tech 5 parts (the nodes that cost 90 science to unlock)

- obviously stock parts only

Current Weight to beat: 6400 kg

And that's the ship you need to beat at the moment:

http://steamcommunity.com/sharedfiles/filedetails/?id=358350971

http://steamcommunity.com/sharedfiles/filedetails/?id=358351585

[Jasonden]

Goal:

Build a rocket capable of landing on the mun and returning to kerbin that does not need any upgraded buildings. So it's limited to:

- 30 Parts

- 20m Height

- 15m Width

- Tech 5 parts (the nodes that cost 90 science to unlock)

- obviously stock parts only

Current Weight to beat: 6400 kg

Good idea for a challenge in the new 0.90! But why evaluate based on mass? That's something that we did Back In The Day before kerbucks --- I don't see that it makes any sense anymore. Why not optimize cost instead? Just an idea. And could there be different leaderboards at different tech levels, maybe, too? Like I'd be interested to know who can do the best at just Tech Levels 3 & 4 as well, for instance Is it even possible on Tech Level 3? How about 2?

Edited December 19, 2014 by Jasonden

[Quintis]

Well in a way he is optimizing for cost. All the limits are based on the stating buildings. If you go over any of the limits you need to upgrade the building, withs in itself will cost more then what you can ever get back in cheaper parts. Being able to build a mun lander at that building / tech lvl wil make career mode a lot easyer.

[chengong]

How can you be at tech 5 and still not have any upgraded buildings in the first place?

[thyriel]

Good idea for a challenge in the new 0.90! But why evaluate based on mass? That's something that we did Back In The Day before kerbucks --- I don't see that it makes any sense anymore. Why not optimize cost instead? Just an idea. And could there be different leaderboards at different tech levels, maybe, too? Like I'd be interested to know who can do the best at just Tech Levels 3 & 4 as well, for instance Is it even possible on Tech Level 3? How about 2?

I don't think there is much room to play if doing it by costs instead mass. See it like in real life people trying to build an amateur rocket that gets into orbit. They aim for lowest possible mass and not lowest possible costs.

For the tech levels: I doubt it's really possible before tech 5, you need at least some solar panels or will run out of electricity to control it.

How can you be at tech 5 and still not have any upgraded buildings in the first place?

You don't need the building upgrades at all to get everything at tech 5 I doubt anyone would do it that way in a serious career game, but with the contracts its just grinding to get enough science for it

Edited December 19, 2014 by thyriel

[hoioh]

this challenge has a LOT of overlap with the other mun challenge in the top 10 current topics, maybe you should team up!

http://forum.kerbalspaceprogram.com/threads/103297-0-90-Mun-science-challenge

[Yemo]

I like those construction challenges.

This is my weight optimized, mun capable probe. Elevons for lightweight landing gear (15m/s impact tolerance, upside downand locked or it will screw up your ascent) and dual 48-7S for the middle stage (girder segment + offset/rotate feature) and a basic jet pack as boosters.

Learned the 48-7S placement from katateochi and his "Chimera" manned mun vessel: http://forum.kerbalspaceprogram.com/threads/103878-18t-%28or-less%29-Returnable-Manned-Mun-Lander?p=1616865&viewfull=1#post1616865

m: 4.8t

Edited December 22, 2014 by Yemo

[bitslizer]

Yemo, your design can be further enhanced by replacing more parts with mass-less parts (landing gear, battery). This end up being 2.5Ton as display by 0.90 info dispaly, or 2510kg. Make it to orbit with 3k+ dv left in final stage, which is plenty for Mun and return (only need about 2000 to 2300dv to transfer to mun, capture, land, launch, and return to kerbin), we can also delete the chute... if you have 2 seconds of fuel left in the tank you can do a power landing..... that save another 100kg, the landing gear can take 50m/s impact without breaking with a ship this light.

Optimizing the fuel load some more we can probably trim this down to below 2500kg for sure

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Edited December 24, 2014 by bitslizer

[thyriel]

nice weight bitslizer But how do you return to kerbin without chute ?

[bitslizer]

nice weight bitslizer But how do you return to kerbin without chute ?

power landing, terminal velocity near sea level is about 120m/sec? the landing gear can take upto 50m/s impact, even without mechjeb you have a pretty wide margin of error to do the power landing as long as you can save about 2 secs worth of fuel, (2 quick blast by the engine is enough to put the craft in upward velocity again). Note that I tested this landing on solid ground, not sure what would happen if you try to land in water at <50m/s

I actually tried using radial decoupler mounted on the bottom of each cylinder tank, since those are lighter than the stack decoupler, but they causes the craft to spin out on staging *shrug*

Edited December 24, 2014 by bitslizer

[Kesa]

Terminal velocity is 100m/s for a drag coefficient of 0.2 (up to 140m/s for 0.1), but you often fall slighty faster as you come from higher (110, 120) and don't have time to be slowed down to terminal v.

For water landing, I guess landing gears won't break, but joint could, as well as anything above. not a big deal since the only point of returning such a probe is for the 'return a vessel from mun surface'. If I saw well, final stage is ~600kg, so a 3s perfect suicide burn should kill all velocity (far harder than suicide burn to 50 m/s though). If you can trim the fuel down, you probably can have 3s of landing burn

[thyriel]

it's a nice idea but i doubt the fuel needed for that weights lesser then a chute

[Yemo]

Very nice design, bitslizer!

Not using the chute is much more efficient. It saves more than 600m/s, while the powered landing costs only 100 or so.

The Jet Booster can be enhanced by adding more intakes, which have very low weight, but high costs. With 8 intakes, the jet only flames out at about 38km or so, saving dV from the rocket stage.

Edited December 25, 2014 by Yemo

[Superfluous J]

it's a nice idea but i doubt the fuel needed for that weights lesser then a chute

You doubt wrong. The fuel is a pittance compared to the chute.

[bitslizer]

Very nice design, bitslizer!

Not using the chute is much more efficient. It saves more than 600m/s, while the powered landing costs only 100 or so.

The Jet Booster can be enhanced by adding more intakes, which have very low weight, but high costs. With 8 intakes, the jet only flames out at about 38km or so, saving dV from the rocket stage.

What kind of thrust is it producing? Kitchen by 32k it's already slowing down instead of acclerating, it is worthy of investigation though

[Kesa]

6.6 t Manned return.

Part count : 15

More info

Mission report

I had two idea designing this vessel :

- EVA thrusting and landing

- low science requirement. The mission is doable in a real career right after your first orbit (and some landed testing contracts), not needing probes related parts (so does many other manned vessel I've seen, as 48 7s and jet engines are close to each other in the tech tree)

Edited December 25, 2014 by Kesa