Kerbal Dynamics: The Insane Golf Shot

[ihtoit]

A long time ago, on a planet not too far from here, somebody said that if you hit a golf ball hard enough, it'll go right round the planet and land back where it started.

This seems like a good place to try out that theory.

THE CHALLENGE:

Send a probe on a ballistic trajectory that takes it precisely ONCE AROUND the planet and land as close as possible in an uncontrolled freefall to the point of launch (ie, KSC).

THE RULES:

- You may use a MINIMUM of two up to as many stages as you like, but your terminal stage MAY NOT include any aerodynamic or RCS control (other than parachutes), or ASAS systems - these must all be in the second to last stage (or, in the case of a two-stage system, in the first (boost) stage).

- You may use MechJeb in the terminal stage for informational purposes during the descent but Smart A.S.S. must be showing and set to OFF for screenshots.

- Your flight MUST take you above the atmosphere (70km altitude).

- You may set an orbital trajectory for your flight during boost phase (in fact this is sensible), but your periapse must allow terminal aerocapture.

- All boost/RCS/ASAS stages MUST be jettisoned before you reach apoapse.

- Your terminal stage (ie the top stage, with the probe core) will be the deciding factor in how close you land.

- All structural parts valid.

- Your boost phase must use rockets. Creeping around with jets is NOT an acceptable method! Neither is pushing apoapse until you're back over KSC.

- No cheats, exploits, infinite fuel or anything else that violates the laws of physics.

- Terminal stage aerobraking may only be achieved using parachutes, with a maximum opening altitude of 1000m AGL (set this in the VAB when you attach your chute (v .23+).

- Powered flight must take place entirely within the ASCENT phase. No thrust may be used during the descent phase (ie any point after achieving apoapsis). This includes RCS. Not that anything should be attached to the core at this point apart from a chute or two, and maybe a battery anyway...

- For the purposes of this challenge, "AROUND" does not mean a 6 hour ballistic arc straight up and back down, it means a suborbital track AROUND the planet. Total MET for each attempt should not realistically exceed 45 minutes.

SCORING:

As in golf, lower is better.

Birdie (-1): anywhere on the KSC Peninsula.

Eagle (-2): anywhere within the ground boundary the KSC Complex (bounded between either end of the runway and the "flat grassed" enclosing perimeter of the Complex).

Hole in One! (-3): Land on any roof at KSC.

Bogey (+1): Overshot the Peninsula.

Mulligan (+2): Fell short of the Peninsula. This is determined by the imaginary line described approximately North to South 5km to the West of the centre of the Complex, that also just happens to bound the plateau. Also score this if you land anywhere else on Kerbin not described above.

You may make a MAXIMUM of 18 attempts (launch to landing, quickloads do NOT count to number of attempts but please indicate whether you actually used them, I'll decide later whether to inflict penalties for this), please keep these within the same post (that's what the edit button's for), your total score and the number of holes played will determine your leaderboard position. Please be honest and document failures as well!

BOARD:

Kasuha Hole: 1 Score: -3

(Challenger's Note: I know this is possible, I have (accidentally, following a failed orbital insertion) bounced a probe off the runway after a single orbit.)

Honourable Mentions:

Kasuha for showing us how it shouldn't be attempted. Good roof landing, though.

Edited April 28, 2014 by ihtoit
clarifications and slight rule change on parachute deployment

[TJPrime]

I know you said we can't use mechjeb for control, but can we use it for information, such as apoapsis height/time and delta-V?

[MaverickSawyer]

Challenge accepted.

EDIT: Can we enter an orbital trajectory at all? It seems difficult to do this while maintaining a suborbital trajectory with a periapsis below the surface...

Edited April 27, 2014 by MaverickSawyer

[Kasuha]

Okay I understand this does not qualify as it is a ballistic arc straight up letting the planet rotate under the ship once which is against rules, and I did use quicksave/quickload extensively. Even with that, this was still more of a lucky shot than something I could reliably repeat. Doing the same thing in prograde orbit should not be much more difficult, though. I may try that later. I just don't know how quickloads count to number of attempts.

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[Kasuha]

Challenge accepted.

EDIT: Can we enter an orbital trajectory at all? It seems difficult to do this while maintaining a suborbital trajectory with a periapsis below the surface...

Completely agreed. Trying to hit KSC from apoapsis at the opposite side of Kerbin is impossible without periapsis at least at 35 km. And if I just push the apoapsis ahead of my ship it feels like I'm beating the spirit of the challenge because nothing prevents me to continue doing so until I'm right above KSC again and then just let the ship fall down.

[ihtoit]

Completely agreed. Trying to hit KSC from apoapsis at the opposite side of Kerbin is impossible without periapsis at least at 35 km. And if I just push the apoapsis ahead of my ship it feels like I'm beating the spirit of the challenge because nothing prevents me to continue doing so until I'm right above KSC again and then just let the ship fall down.

As I was writing this challenge I did consider this, and came to the conclusion that from the way my failed flight turned out, I ran out of fuel pre-apoapse and figured, hell with it and jettisoned the lifter stage in preparation for reentry/landing. At that point the periapse was at 30km and short of a KSC landing by about 50km. By the time I got to 30km, p<0 was some way past KSC and I was seeing atmospheric effects and slowing down. I'll make a clarification, and to answer the other question - you can use MechJeb in the probe stage for informational purposes during the descent phase.

Edited April 27, 2014 by ihtoit

[Kasuha]

Okay, here's my second attempt.

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[SpaceK531]

*golf claps*

Nice job! a pinpoint landing.

[Floppster]

Wow, impressive

[MaverickSawyer]

As I was writing this challenge I did consider this, and came to the conclusion that from the way my failed flight turned out, I ran out of fuel pre-apoapse and figured, hell with it and jettisoned the lifter stage in preparation for reentry/landing. At that point the periapse was at 30km and short of a KSC landing by about 50km. By the time I got to 30km, p<0 was some way past KSC and I was seeing atmospheric effects and slowing down. I'll make a clarification, and to answer the other question - you can use MechJeb in the probe stage for informational purposes during the descent phase.

So, as long as the PeA is below 70 km, it's fair game?

[ihtoit]

Okay, here's my second attempt.

...

nicely done! Who said it was "practically impossible"??

@MaverickSawyer: Pe<35km<70km isn't really practical for a single-orbit aerocapture, sure it will brake (a little) and bring the apoapse down, but at those altitudes you're looking at a second orbit. The rules stipulate a single orbit.

[Kasuha]

Who said it was "practically impossible"??

Nobody. What I wrote was

Trying to hit KSC from apoapsis at the opposite side of Kerbin is impossible without periapsis at least at 35 km.

And sure enough, my periapsis was above 35 km.

[ihtoit]

Nobody. What I wrote was

And sure enough, my periapsis was above 35 km.

it was? I missed that...

[godefroi]

Impressive.

Edited April 29, 2014 by godefroi