Aero Gravity Assist, kerbin to Duna, Aldrin cycler challenge.

[meyst]

Objective, fly the provided experimental AeroGravity Assist craft on the persistent file here in the categories of your choice for fun and profit.

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Category 1 (Fuel, who needs that?)

Fly an AeroGravity Assist maneuver with the ship incoming to Kerbin and set up a Duna encounter using the least fuel.

Post an image that shows your ships mass and fuel with a Duna encounter.

The contestant who uses the least Delta V takes our top spot.

If you want to do the math yourself the Delta V used is calculated with the Rocket equation assumptions of Isp 350 and a pre maneuver mass of 1.39 tons. Plus any additional correction needed for an encounter.

Category 2(Best cyclist)

Fly the ship incoming to Kerbin on as many cycles as you can/want. You get 1 point for every Duna flyby picture you post that also shows the encounter and the ships time in flight. You don't need to fly close to Duna if you don't want to, any encounter is enough.

Category 3 (Twinsies!)

Rendezvous the cycler in orbit with the incoming cycler and fly both together as they cycle. Keep them within 100KM of each other, they may fly further apart only when they are within 10 days of a Duna or Kerbin encounter (or leaving such an encounter). Post screen shots of the ships together as you fly the Kerbin to Duna leg and an additional one on the Duna to Kerbin leg. Each leg they fly together gets you 2 points. Most points wins. (Hard)

Rules

Use the provided craft on the provided persistent file, do not alter the craft, only mods that do not alter the flight characteristics of the craft are allowed (ie no hyper edit, alarm clock is okay). Note the file and ship provided are stock so no mods are required.

Notes

I will update this as often as I can.

All categories are scored independently

Make a quick save as soon as you can.

The ships are experimental and fly like Kerbals built them, they are light on the nose when in atmosphere and fly on a 90 degree roll (sounds scary, but easy to figure out). Action group 1 toggles the solar arrays. These are Aero Gravity Assist craft and use the wings to keep them down as much as possible (like race car 'airfoils')

This challenge was inspired by proof of concept testing I was doing for the Duna Permanent outpost mission challenge. It is my hope that your insights will lead to bigger and better things. Besides, I was having fun and figured I should share.

Current Scores

Category 1 (Fuel, who needs that?)

1. Johnno (100 M/S, 1.35 tons, 48.93 fuel remaining)

Category 2 (Best cyclist)

Category 3 (Twinsies!)

Edited August 16, 2013 by meyst
Rules updated

[Johnno]

Are we allowed to use the fuel on the ship or is this supposed to be done just by aerobraking?

[meyst]

You can use all the fuel on board the ship.

[Johnno]

You can use all the fuel on board the ship.

Great, thanks for the fast reply. I didn't quite know what aero gravity assist meant, so I gave it a few tries. First dryrun just to see how the craft handled, then one run with just full burn, and here's a screenshot from my third run after I kinda figured it out but wanted clarification on if I could use the engine.

Guess I'll go finetune my technique.

Sweet challenge btw, very different and interesting.

[meyst]

Johnno, you burned your engine before the propulsive correction, so most of the used delta V doesn't show on that maneuver node correction. The intent of the challenge is to use the least delta V / fuel on the maneuver.

Given the intent of the challenge and that I want to limit people as little as possible. I used the mass you had left to figure out how much was used. The Tsiolkovsky rocket equation came up with 476.16 M/S. I added that to the displayed 13 M/S correction burn for a category 1 score of 489 M/S, a very good start.

I also pulled the following off Wikipedia

An aerogravity assist, or AGA, is a spacecraft maneuver designed to change velocity when arriving at a body with an atmosphere. A pure gravity assist uses only the gravity of a body to change the direction of the spacecraft trajectory. The change in direction is limited by the mass of the body, and how closely it can be approached. An aerogravity assist uses a closer approach to the planet, dipping into the atmosphere, so the spacecraft can also use aerodynamic lift to further curve the trajectory. This enables the spacecraft to deflect through a larger angle, resulting in a higher delta-v (change in velocity). This in turn allows a shorter travel time, a larger payload fraction of the spacecraft, or a smaller spacecraft for a given payload.

The related techniques of aerocapture, aerobraking, and atmospheric re-entry also attempt to use the body's atmosphere to help reduce propulsion requirements. In an aerogravity assist, however, the goal is not to use the atmosphere to slow the spacecraft down, but instead use it to achieve a larger change in direction.

Aerogravity assists are so far theoretical and have not yet been used.

Edited August 15, 2013 by meyst

[Johnno]

Johnno, you burned your engine before the propulsive correction, so most of the used delta V doesn't show on that maneuver node correction. The intent of the challenge is to use the least delta V / fuel on the maneuver.

Right, cause I've been redoing this a few times and trying to figure out why it was so easy. The thing is, the manouver nodes aren't saved when you swap ships/exit, so there was none ingame, hence I couldn't figure out what I was supposed to do with the limited explanation in the challenge. You'd have to note exactly where the manouver node is supposed to be. Also to be fair, your fuelgauge wasn't showing so I didn't know if you'd used fuel or not, so I couldn't figure out if it was supposed to be a unpowered manouver or not (hence my question).

Would've probably been easier to decouple the engine before posting the save, and explaining where the manouver node is to be set.

Edit: After a bit of testing, if we have to manually put the manouver node down around minute 39 as per your screenshot, the delta-v requirement for an encounter can differ up toward 30-40m/s within one minute. If we take into account the lacking precision of the MET time that difference would be even bigger.

Edited August 16, 2013 by Johnno

[meyst]

the delta-v requirement for an encounter can differ up toward 30-40m/s within one minute.

I was originally thinking that showing the maneuver node for the Delta V needed for the course change would make things simpler, it is clearly not.

I wonder if that difference of 30-40 M/S is showing the change from the Oberth effect decreasing as the ship flys back up the gravity well, or a reflection of how far off course the ship is. Most likely both.

So I have made a rules amendment, to score the category 1 missions we will instead post a picture with the remaining fuel and mass like you did and use that to figure out the scoring. As my old picture doesn't meet those requirements I removed it. I also update the scoreboard.

Edited August 16, 2013 by meyst

[Johnno]

I wonder if that difference of 30-40 M/S is showing the change from the Oberth effect decreasing as the ship flys back up the gravity well, or a reflection of how far off course the ship is. Most likely both.

I think it's mainly that the earlier you do a correction the less you have to spend.

So I have made a rules amendment, to score the category 1 missions we will instead post a picture with the remaining fuel and mass like you did and use that to figure out the scoring. As my old picture doesn't meet those requirements I removed it. I also update the scoreboard.

I think it'd be easiest to even just burn for the encounter and show a screenshot of remaining fuel after the aero gravity assist + correction burn and just have the remaning liquid fuel as score. Also as my entry was done on faulty premise (and I can now do better unpowered even) please go ahead and remove it.

Edit: Here's the best I've been able to do for now. By my calculations 100 delta-v spent.

1.35T final mass, 48.93 liquid fuel left.

Click for hires

Edited August 16, 2013 by Johnno
Added entry

[meyst]

That is a good idea, added.

100 M/S is an excellent score! Far better than anything I have pulled off to date, how did you do it? Also do you plan to fly any Duna encounters for a category 2 score?

[Johnno]

That is a good idea, added.

100 M/S is an excellent score! Far better than anything I have pulled off to date, how did you do it? Also do you plan to fly any Duna encounters for a category 2 score?

I made a miniscule change to my periapsis before heading in for aero gravity assist. Then just fought really hard to control the craft while in the atmosphere. I also started my correction burn while still inside the atmosphere, but high enough up that I sort of had a good guesstimate on how much velocity I'd have to change.

And yeah I'll probably see what I can come up with both in category 2 and 3. Category 3 sounds a bit iffy, but hey, it's a challenge.