High Fuel Prices

[specialopsdave]

CHALLENGE: Build a spacecraft (stock only) and achieve Kerbin Orbit from the launchpad or runway at KSC using the fewest units of fuel you can.

RULES: No mods that affect this challenge (fuel/thrust affecting parts), no decoupler launching, no shockwave abuse, ending periapsis must be >70,000m

SCREENSHOTS: One before launch in external view, with resource tab open, one in orbit in map view with resource tab open and periapsis altitude highlighted (FAR Flight Data works too). MechJeb IS allowed.

JUDGING: End fuel values (LiquidFuel, Oxidizer, SolidFuel, MonoPropellant, XenonGas) will be subtracted from initial values to create that player's sore. The player with the LOWEST score wins.

LEADERBOARDS: 1: swjr-swis, 52.57 points

2: foamyesque, 80 points

Edited July 17, 2016 by specialopsdave

[foamyesque]

 

You might want to specify a payload. :v

[septemberWaves]

Perhaps score should be calculated with fuel units per tonne of payload.

[specialopsdave]

18 hours ago, eloquentJane said:

Perhaps score should be calculated with fuel units per tonne of payload.

 

On ‎7‎/‎13‎/‎2016 at 3:38 AM, foamyesque said:

 

You might want to specify a payload. :v

I'm not counting payload, meaning that you can use parts as light as you want. LKO is the only requirement.

foamyesque, correct me if I'm wrong, but is that engine modded? If so, that counts as a mod that affects the challenge, disqualifying your entry. Sorry! (P.S, It might be an Ant engine and I just can't see well) (P.S, Fuel remaining should NOT be burned, as it counts towards your score as total fuel used.)

Edited July 15, 2016 by specialopsdave

[foamyesque]

10 minutes ago, specialopsdave said:

 

I'm not counting payload, meaning that you can use parts as light as you want. LKO is the only requirement.

foamyesque, correct me if I'm wrong, but is that engine modded? If so, that counts as a mod that affects the challenge, disqualifying your entry. Sorry! (P.S, It might be an Ant engine and I just can't see well) (P.S, Fuel remaining should NOT be burned, as it counts towards your score as total fuel used.)

It's fully stock. The engine is an Ant engine I centered via the offset tool. And yes, I know fuel remaining shouldn't be burned, but in that particular run I didn't exactly have a choice -- I was out of battery power for the probe, so I couldn't tell it to stop.

[specialopsdave]

4 minutes ago, foamyesque said:

It's fully stock. The engine is an Ant engine I centered via the offset tool. And yes, I know fuel remaining shouldn't be burned, but in that particular run I didn't exactly have a choice -- I was out of battery power for the probe, so I couldn't tell it to stop.

Hm. I thought that Ant had an alternator. Perhaps an OX-STAT would work better than a battery for use on the upper stage. Otherwise, I applaud you for the use of only tiny parts. Few people could pull that off (I know I couldn't have).

 

Your score: 80.

Edited July 15, 2016 by specialopsdave

[foamyesque]

1 hour ago, specialopsdave said:

Hm. I thought that Ant had an alternator. Perhaps an OX-STAT would work better than a battery for use on the upper stage.

No, none of the probe-size parts have alternators. I misspoke, it's actually a Spider (for the gimballing), but either way, it doesn't generate electricity. The solar panel weighs too much -- and, more importantly at this size, has too much drag -- to include on the upper stage; the only power it has is what is integral to the probe core itself. There's a pretty tight time limit to getting to orbit once I detach the lower stage with its battery.

[specialopsdave]

Perhaps you could use the battery on the upper stage? I know it hurts second stage mass values, but it'd be worth it for the amount of fuel saved and not accidentally burned off (in my opinion).

[kiwi1960]

You guys do know that anyone posting a challenge must have actually done it first and posted proof of it...

 

[swjr-swis]

5 minutes ago, kiwi1960 said:

You guys do know that anyone posting a challenge must have actually done it first and posted proof of it...

I'll accept @foamyesque's entry as proof by proxy, if you will.

[foamyesque]

1 hour ago, specialopsdave said:

Perhaps you could use the battery on the upper stage? I know it hurts second stage mass values, but it'd be worth it for the amount of fuel saved and not accidentally burned off (in my opinion).

 

It isn't, trust me. When you get down to things this small, the mass of the battery becomes very significant; both for TWR and for deltaV. if it weren't for how nasty aerodynamic drag is at the 0.625m diameter I would cut the nosecone to save weight, too.

 

Heck, I had to action-group the cross-feed toggle on the decoupler to manage my fuel -- I needed a longer run on the Spark than a single Oscar-B could provide, I needed the lower tank to drain first, and I couldn't afford the dry mass of another Oscar-B.

[specialopsdave]

3 minutes ago, foamyesque said:

 

It isn't, trust me. When you get down to things this small, the mass of the battery becomes very significant; both for TWR and for deltaV. if it weren't for how nasty aerodynamic drag is at the 0.625m diameter I would cut the nosecone to save weight, too.

 

Heck, I had to action-group the cross-feed toggle on the decoupler to manage my fuel -- I needed a longer run on the Spark than a single Oscar-B could provide, I needed the lower tank to drain first, and I couldn't afford the dry mass of another Oscar-B.

You really thought this out, huh? That's actually really cool.

[swjr-swis]

An entry on a hybrid concept, taking advantage of the high fuel efficiency of jets to take care of the first stage at a fraction of the fuel cost of a rocket:

Spoiler

On the pad.

In orbit.

Some more pics of the ascent and closeup of the final stage in orbit in the album: https://imgur.com/a/fgohp

1st stage uses a set of Juno jets with just enough LF to get to their ceiling. 2nd stage uses two Spider rockets.

52.60 units of fuel on the pad, 52.57 units used to get a 70x72km orbit.

I think this rocket can probably do it with about 50-51 units. One attempt landed me on a 72x94km orbit, but used up all fuel because I fumbled the cut-off. I may try again, but for now the above is my entry.

Edited February 21, 2018 by swjr-swis
old imgur album link was no longer working

[Gauga159]

I'm REALLY Intrested but is procedural parts (for fuel tanks) allowed?

[specialopsdave]

On ‎7‎/‎18‎/‎2016 at 2:18 AM, Gauga159 said:

I'm REALLY Intrested but is procedural parts (for fuel tanks) allowed?

As long as the wet/dry mass ratios remain at or below 9/1 (LF+O).