The Slingshot Manoeuvre Challenge

[The_Rocketeer]

Welcome to The Slingshot Manoeuvre Challenge:

Challenge details:

From LKO, reach a manned stable orbit of Eeloo using at least one gravity slingshot manoeuvre from another planet or moon. The idea is to get there using the least liquid fuel you can.

This challenge is a test of your design skills, manoeuvre planning and execution, and your understanding of orbital mechanics including the Oberth effect.

Real Life space missions such as Voyager 1 & 2 and Cassini-Huygens depended on these things to reach the outer solar system! The Rosetta probe recently featured in the news (at least in the UK) used FOUR of them!

We're not looking for a Grand Master Champion, this is just a good excuse for a trip to Eeloo! However, if you're keen to prove your space prowess by topping the table, we'll keep a top 10 list of lowest fuel costs. Everyone who makes it will be entered into the HALL OF FAME with the appropriate accolades! (There may also be a sig-badge at some point if I can remember how PSP works...)

Jeb: Gravity Assists Save Fuel!

Bill: Timing your Kerbin exit to suitable planetary alignments will be crucial to reducing your total FUEL requirements.

Bob: Keep it lightweight - this isn't a delta-V challenge, this is all about the FUEL!

This Wikipedia article should help if you're unsure where to start.

Rules:

1. Propulsion

a. You must use at least one rocket engine and at least one LF+O tank.

b. Only liquid fuel engines are allowed: No Ion drives. No SRBs.

c. You may use RCS thrusters, but propellant is limited:

i. Max 20 monopropellant per tonne of starting mass (fueled).

d. Stock propulsion parts only

2. Parts

a. Your craft must include a Mk1 Lander Can

b. Your craft must include at least one RTG

3. Starting and Finishing Points

a. Start must be from an orbit of Kerbin with Apoapsis below 100,000m

b. Finish is any orbit of Eeloo with Periapsis above the surface and Apoapsis within Eeloo's SOI.

4. Mods

a. Entrants using Mods that alter stock physics or bodies will be classified Gatecrashers (See Rule 6)

b. Other mods are assumed to be allowed as long as they do not infringe the Rules.

c. Precise Node and MechJeb are recommended for this challenge.

5. Scoring Criteria

a. Challenge scores are based solely on absolute liquid fuel used.

b. Hall of Fame (TBC)

i. Based on SOIs entered, MET:Fuel used ratio, craft mass etc

6. GATECRASHERS

a.Successful entrants who have broken rules will receive a special accolade and be commemorated in the Hall of Infamy.

Accolades:

(Note: numeral suffix indicates number of gravity assists used)

Challenge accolades:

Hammock - Basic challenge unsuccessfully attempted

Slinger - Basic challenge completed

Onagerist - Used assists from both Mun and Minmus on your way out of Kerbin's SOI

Mangonelian - Used an assist from Moho

Trebucheteer - Used a retrograde (braking) assist from Jool and still reached Eeloo

Special accolades:

Mortarman - Gatecrasher

Slipknot - Run out of fuel

Banana Hammock - Fatal collision interface during an attempt.

Ricochet - Used a retrograde assist from any moon to get a (bigger) counter-rotation assist from the parent planet.

Rebound - Leave Eeloo orbit and come home again!

Rangefinder - Use ONLY an SRB for thrust during a gravity assist and hit your next target without making another burn (RCS corrections allowed).

Jeb Mode - Use assists from every planet in order from Moho to Jool on your way to Eeloo

(I will probably add more as I invent them - feel free to make suggestions).

HALL OF FAME:

Top 10 Supermen!

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

HALL OF INFAMY:

(My own attempt will follow)

Edited November 21, 2014 by The_Rocketeer

[immelman]

Should check out Plad's challenge a while back, some of the entries had very low delatv.

The amount of LF used is just a function of engine size anyway?

Edited November 21, 2014 by immelman

[PLAD]

Yup, I had a lowest dv challenge for getting from LKO to Eeloo's surface some time ago. I did that for 1934m/s, just the part from LKO to low Eeloo orbit was 1324m/s. But I didn't note the fuel used anywhere and the ship wasn't manned so I can't use that. We had a great discussion over the best path to follow.

I then entered in an SSTO to Eeloo and back challenge, and that ship was manned, and because it was SSTO and I recorded the weight at various points I see I got from LKO (74x74km) to a stable ~5x75 orbit around Eeloo for 1.56 tons of fuel+oxidizer (and 1192m/s). It used a command pod MK1 instead of the lander can MK1 though, since that is heavier is it allowed? I'd like to use that to enter in this if I can, though I can see a few ways that it can be beat by optimizing for fuel use instead of dV. It wouldn't be too easy though.

[The_Rocketeer]

Should check out Plad's challenge a while back, some of the entries had very low delatv.

The amount of LF used is just a function of engine size anyway?

Well shoot, I even scanned thru to see if I could find anything similar and totally missed Plad's challenge. So much for originality.

Still, this challenge is more of an accolade than a race to the top, though the uber-competitive are welcome to try and out-do each other. I'm not interested in finding the minimum possible delta-v, I'm more interested in seeing people practice some RL techniques for reaching the outer system, and giving poor old Eeloo a little extra attention out there on the edge of nothing.

I chose LF rather than delta-V because it's more accessible for the uninitiated to understand. Less fuel is more efficient, simple as. Fuel isn't just a function of the engine's size/ISP, it's also a question of overall mass - delta-V doesn't account for force (and fuel) required, just speed.

Yup, I had a lowest dv challenge for getting from LKO to Eeloo's surface some time ago. I did that for 1934m/s, just the part from LKO to low Eeloo orbit was 1324m/s. But I didn't note the fuel used anywhere and the ship wasn't manned so I can't use that. We had a great discussion over the best path to follow.

I then entered in an SSTO to Eeloo and back challenge, and that ship was manned, and because it was SSTO and I recorded the weight at various points I see I got from LKO (74x74km) to a stable ~5x75 orbit around Eeloo for 1.56 tons of fuel+oxidizer (and 1192m/s). It used a command pod MK1 instead of the lander can MK1 though, since that is heavier is it allowed? I'd like to use that to enter in this if I can, though I can see a few ways that it can be beat by optimizing for fuel use instead of dV. It wouldn't be too easy though.

Cool challenge - wish I'd seen it! But as I said this is less about who can be the best and more about who can use these techniques to get to Eeloo. Gravity assists are a big deal in RL space exploration, but they're easily overlooked in the face of a delta-v tree.

You can enter whatever you want if you don't mind winding up in the Hall of Infamy! I went for the Lander Can because it makes sense to use the lightest pod to minimise your fuel demands.

Given these early responses, I'm rewording the challenge description slightly to make it more challenge-y and less competition-y. I'll keep a high-score table for the hardcore space troopers, and I'm planning to come up with some higher difficulty versions too.

Edit: As a footnote, this is the first challenge I've submitted, so please bear with me while I tweak this and that

Edited November 21, 2014 by The_Rocketeer

[SRV Ron]

A ship from a 10 part challenge fully capable of such a mission with slingshot maneuvers, direct intercept from Kerbal orbit, and taking advantage of when Eeloo crosses Jool's orbital plane. Using turbojets could easily place the LV-N payload section in orbit with far less fuel then what the Skipper needed for that challenge. (It was even done with five parts by elimination of all safety devices including solar panels and explosive staging of the orange tank using the LV-N.)

[The_Rocketeer]

Yup, building an Eeloo capable rocket isn't the hardest part of this challenge.

This also isn't supposed to be incredibly difficult. It would be great if this did for slingshot manoeuvres what the Kerbal Prize challenge has done for SSTO SPs.

Tho, you're using the Mk1 Command Pod, not a Mk1 Lander Can