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Fastest Time to Circular Orbit, e < 0.1


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The Kerbal budget meeting is in 2 minutes and you forgot to build any rockets all year.  You need to get to a nice looking circular orbit as fast as possible to impress everyone.

This is a fast challenge of piloting skills and quick thinking, and using a much different launch profile than you're used to.  The circularization step is the hard part - a test of your understanding of changing orbits under pressure, as well as a game of "chicken" when to start circularizing, so you don't drop your periapsis or apoapsis below 70k in the process.  It was inspired by various other challenges.

  • Objective: Get into circular kerbin orbit (peri/apoapsis > 70,000m with eccentricity < 0.1) as fast as you can (based on time since launch).
  • Use 40 or fewer parts (this helps level the playing field).  Fewer parts is better.
  • Provide uncut video of the whole attempt
  • Stock game, no DLC parts, no part or physics mods, no cheats, no part clipping, no craft file editing type stuff (all the standard rules like that).
  • You probably want Kerbal Engineer for convenient readouts.
  • kOS and autopilots allowed, but note if you used them, and it should be considered a separate category.
  • Finish time is the mission time in the upper left, when you achieve the orbit described in the first bullet point.
  • Landing afterwards is optional, taking a kerbal is optional, it just adds a little weight.

Limiting to 40 parts is mostly out of concern for framerates, and to level the playing field.  Kerbal Engineer can display part count but this can go on the honor system.

Kerbal Engineer is good for displaying orbital info, but the stock game can display eccentricity as well, (bottom left, in maneuver mode under advanced orbital info), just not the precision needed (e.g. it will display .1 when the actual eccentricity is .149).  It can also be calculated from periapsis/apoapsis if you know how.  But I am assuming you will use kerbal engineer.

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Here is my own best (1:26) after several attempts and I'm sure it can be done better.  Instead of Mammoth engines I used groups of 4 vector engines on an adapter, and with onion staging, so there is definitely room for improvement.  It's 40 parts exactly.

 

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After about 150 more attempts and lots of craft redesign, I got down to about 1:00.7 (judging from the first frame I got in the desired orbit).  This was pretty hard to get.  I used 4 "boosters" in onion staging, each consisting of 2 mammoth engines and 2 kerbodyne s3-7200 fuel tanks (plus 1 nose cone, 1 strut, 1 fuel line, and 1 decoupler), to accelerate off the ground really fast but still have a good amount of fuel.  I used a more vertical launch profile, and also cut the engines for a few seconds while approaching the point to start thrusting sideways/downwards to get into orbit, because using delta V vertically in this region has minimal benefit on total time.  The craft only had 56.7 seconds of thrust time, so it was critical to use it well and I just barely did it, with many failed attempts.

In a basic theory, the best launch profile of this challenge is go almost straight up to get out of the dense atmosphere quickly, then at a certain point thrust down/forward at a ~45 degree angle, so that the following 4 parameters reach their needed value simultaneously: the vertical speed reaches zero, the horizontal speed reaches a bit above orbital velocity, the current altitude reaches > 70km, and the craft runs out of fuel.  I used something close to this profile.

This is stock version 1.7.3.  Also I wonder if additional categories are needed.  What I did here is going to be hard to beat.  Perhaps categories <20 parts or <80 parts, or under a certain mass would be good.

 

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