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The Mun and back Cheapskate Challenge


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On 11/4/2020 at 7:54 PM, camacju said:

I have no idea what happened between Mun insertion and low Mun orbit - I obviously didn't have infinite fuel enabled but I somehow gained fuel.

This mission cost me 159 funds but I feel bad about that glitch so I'll subtract another 200 m/s worth of fuel from my score, bringing mission costs to 160 funds even.

Unfortunately with that glitch no-one can know what the actual fuel consumption was - so I can't accept that entry officially but I appreciate your honesty about it.

However it's pretty clear that you go can lower than your current 1st place score, perhaps even lower than 160 funds by iterating on your current design. If you want to enter again with a tweaked version of your current 1st place entry, I'm happy to update your slot.

(It's fine to do named quicksave regularly just in case that unexplained fuel glitch strikes again, so you could revert to a known good point without having to start the entire mission over)

Edited by ManEatingApe
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  • 1 month later...
5 hours ago, camacju said:

https://imgur.com/a/Npdmi5B

Mini submission, 2643 funds command chair category. This was for a ksp discord challenge

As always, a neat and efficient entry. Added you to the leaderboard.

 

For anyone who is following this thread, the latest 1.11 version brings in some interesting changes. Kerbal's EVA packs and parachutes now add mass to the craft, which has the following implications:

  • Podded entries are mildly more efficient (you can omit the jetpack and personal parachute)
  • Command chair entries are potentially much more efficient (a 0.05 versus 0.09 ton Kerbal is a more significant change)
  • A personal parachute vs a chute on the command chair entries is now more balanced (both add mass)

I'm sure that enterprising cheapskates will find a way to leverage the inventory system for costs savings and look forward to the entries!

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  • 1 month later...

@ManEatingApe First submission of 1.11.1. I waited until now because of the Kerbal drag glitch with service bays and fairings. The craft is similar to last entry except stripped down even further. Total cost is 142 funds and it could probably be even cheaper.

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16311 funds in SPH

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I pitch up to 30 degrees and then do a standard gravity turn. Centripetal acceleration begins to kick in at this point.

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Rapier switches to rocket mode

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I've got just enough delta-v to circularize. Note that I didn't launch with a full oxidizer load because the jet ascent would use too much fuel.

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In orbit with 29m/s of delta-v left.

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Carrier plane deorbits

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Approach

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Landed

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14302 back. Cost so far is 2009 funds.

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Mun transfer

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I have way more delta-v than I expected since the dry mass doesn't include the jetpack anymore, so I don't need to do any fancy gravity assists. However it's always fun to do a ballistic capture - or at least as close as I can get with patched conics.

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200 m/s circularization burn, instead of 280 or so from a direct transfer

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Landing burn

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Flag

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Ascent

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Direct return - easier to aim for KSC

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On course for KSC

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Chute deployed

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Landed

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1867 funds back - total cost is 142

Edited by camacju
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15 hours ago, camacju said:

First submission of 1.11.1. I waited until now because of the Kerbal drag glitch with service bays and fairings. The craft is similar to last entry except stripped down even further. Total cost is 142 funds and it could probably be even cheaper.

Nice work on the ruthlessly reduced reusable refinement. You retain the top spot in the category.

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@ManEatingApe  Will the following techniques be allowed? I have an idea for an even cheaper mission using one or more of these.

-Node occlusion: reducing drag cubes of parts with nosecones and then putting them in a fairing or service bay (and not necessarily clipping them - they'd all be next to each other but not clipped)

-Magic wings: using flags or heat shields to produce lifting surfaces with less drag than normal wings. Can be combined with node occlusion but is not necessary, does not require clipping either

-Gaining altitude (and energy) using Breaking Ground propellers to reduce fuel cost

-Magic propellers: propellers that generate their thrust through magic wings, producing less drag than normal propellers for the same amount of thrust. Again does not require clipping

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15 hours ago, camacju said:

@ManEatingApe  Will the following techniques be allowed? I have an idea for an even cheaper mission using one or more of these.

Thanks for asking for clarification in advance,  I appreciate it. This spirit of this challenge is to get as cheap as possible, within the constraints of the normal intended physics of the game. Excessive clipping is just one aspect of that philosophy. Bearing that in mind...

15 hours ago, camacju said:

-Magic wings: using flags or heat shields to produce lifting surfaces with less drag than normal wings. Can be combined with node occlusion but is not necessary, does not require clipping either

<snip>

-Magic propellers: propellers that generate their thrust through magic wings, producing less drag than normal propellers for the same amount of thrust. Again does not require clipping

Hard no on both of these. (they would come under the Wheaton rule category). The heat shield trick is amusing, but falls under the same category of unintended physics glitches as the (now fixed) drain valve exploit or various other Kraken-tech. Any entry using this would go straight to the Rogue's Gallery. You could submit a clearly labelled entry just for fun on that understanding.

15 hours ago, camacju said:

-Node occlusion: reducing drag cubes of parts with nosecones and then putting them in a fairing or service bay (and not necessarily clipping them - they'd all be next to each other but not clipped)

I'm a little dubious on this, but perhaps a little more explanation would help before making a decision.
As I understand it parts that are completely contained within a service bay or fairing are not considered for aerodynamic drag, so I'm not sure about the advantage of adding a nosecone inside the bay.

15 hours ago, camacju said:

-Gaining altitude (and energy) using Breaking Ground propellers to reduce fuel cost

Absolutely yes and I would encourage it! Both DLCs are completely fine.
There's even a number of different approaches you could consider:

  • Propellers in addition to rapier/whiplash to assist in lower atmosphere.
  • A separate propeller mothership entirely, that carries and releases a more conventional rocket powered craft (e.g SpaceShipTwo / WhiteKnightTwo). This mothership could then return to KSC.
  • A propeller powered recovery vessel that is launched separately to the initial craft and recovers the parts dumped around Kerbin, returning them to the KSC for 100% recovery value.
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8 minutes ago, ManEatingApe said:

The heat shield trick is amusing, but falls under the same category of unintended physics glitches as the (now fixed) drain valve exploit or various other Kraken-tech.

What about using the decorative flags as lifting surfaces? Would that count also? The heat shield trick only is a glitch because the heat shield produces lift even when its nodes are occluded, which shouldn't happen. Using flags as lifting surfaces doesn't require that - the flags produce a good lift:drag ratio without any such adjustments.

10 minutes ago, ManEatingApe said:

I'm a little dubious on this, but perhaps a little more explanation would help before making a decision.
As I understand it parts that are completely contained within a service bay or fairing are not considered for aerodynamic drag, so I'm not sure about the advantage of adding a nosecone inside the bay.

Basically when you have a part, it has a drag cube and produces drag proportional to the area of that cube (more like a cuboid but still called a cube). When you attach another part to one of its attachment nodes, it reduces the size of the drag cube and thus generates less drag. This is the point of nose cones, which reduce the front facing drag cube area. However, nose cones have a drag cube themselves, so they generate drag. And if a nose cone is offset away from a part but still "attached," it has the same drag benefit. So the node occlusion trick would basically be offsetting the nose cones inside a cargo bay, where they won't generate any drag but still provide the same drag benefit.

The main rationale behind these questions is that since my craft is so light and has a good TWR during atmospheric ascent, the main loss of efficiency is drag losses. So I'm trying to reduce drag as much as possible. That's also the reason for using the prop engines to get some initial altitude.

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51 minutes ago, camacju said:

Basically when you have a part, it has a drag cube and produces drag proportional to the area of that cube (more like a cuboid but still called a cube). When you attach another part to one of its attachment nodes, it reduces the size of the drag cube and thus generates less drag. This is the point of nose cones, which reduce the front facing drag cube area. However, nose cones have a drag cube themselves, so they generate drag. And if a nose cone is offset away from a part but still "attached," it has the same drag benefit. So the node occlusion trick would basically be offsetting the nose cones inside a cargo bay, where they won't generate any drag but still provide the same drag benefit.

Gotcha - the parts remain outside the bay, but the nosecones are placed inside it. Clever, but I'll have to disallow it. Either live with the drag of the nosecones or streamline things into fewer stacks.

54 minutes ago, camacju said:

What about using the decorative flags as lifting surfaces? Would that count also?

Flags producing body lift at an angle is a confirmed bug. The ESA exploit challenge feels like a better home for flag related chicanery.

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  • 2 weeks later...

@ManEatingApe There's another possible route for optimization that I wanted to run by you before attempting a mission with it.

Kerbals normally have only two inventory slots, so the best way to optimize delta-v would be to have a jetpack in one slot and an EVA fuel cylinder in the other slot. With this method, the Kerbal would be able to land on the Mun with jetpack and have almost enough delta-v to return. Alternatively, the Kerbal would be able to finish off the Mun landing burn and jetpack all the way back to Kerbin.

However, if you hold an item with your mouse, you effectively gain a third inventory slot, although you can't use the held item. With this method, the Kerbal can do the Mun capture, landing, ascent, and return, all on EVA pack fuel. I would have a cylinder and a pack in inventory, drain them, and then swap the empty pack for the full pack I was holding, and this would significantly reduce both reusable and expendable mission costs.

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1 hour ago, camacju said:

However, if you hold an item with your mouse, you effectively gain a third inventory slot, although you can't use the held item. With this method, the Kerbal can do the Mun capture, landing, ascent, and return, all on EVA pack fuel. I would have a cylinder and a pack in inventory, drain them, and then swap the empty pack for the full pack I was holding, and this would significantly reduce both reusable and expendable mission costs.

That's an ingenious and entertainingly Kerbal discovery! :happy:

I like the idea of your unfortunate Kerbal clutching an extra tank of fuel all the way down and back.
Sure, I'll allow it: I'm intrigued if it will work.

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After a bit of testing I've concluded that the third slot is too buggy to rely on. I'll switch tactics but will still probably be able to shave a good amount off the cost.

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@ManEatingApe I finally ended up going the route of the Spider engine. 1738 funds, chair category

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In VAB

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Pre tilted booster for  automatic gravity turn

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Burnout, coasting

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Circularizing. This lander is built around the decoupler, with the baguette, chair, and spider attached to it.

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Kerbin orbit

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Holding the jetpack seems to increase delta-v. Not strictly required but it's helpful

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Mun circularization straight to landing burn

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Final descent. At this point the lander becomes hard to control with just gimbal so Bill bails out

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Flag

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Ditched cylinder

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Mun orbit

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Return burn

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I can't add maneuver nodes in EVA so I had to eyeball the burn. That's why I barely have any fuel left

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Bill ditches the EVA pack to shed mass, and still almost burns up

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World record high dive?

Edited by camacju
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On 2/16/2021 at 6:49 AM, camacju said:

 I finally ended up going the route of the Spider engine. 1738 funds, chair category.

Nice entry, added you the leader board in the chair category.
I liked the truly minimal design and taking advantage of the extra EVA fuel allowed by the new 1.11 inventory system.

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