Visit the sights of the Kerbol system by only going retrograde.

[Galane]

Mistress Mary, quite contrary.

How does your orbit go?

Retrograde!

Simple rules.

One point for each body visited and orbited.

One point for each body landed on and returned from.

All orbits, including takeoff from Kerbin, must be retrograde.

Any mods you want except for infinite fuel mods or anything that warps like hyperedit or interstellar or extraplanetary launchpads.

MechJeb's Ascent Guidance isn't real good for this because when set to go West it first angles towards the East then wastes a ton of fuel twisting the trajectory around. You may also find MechJeb difficult to work with getting into and out of orbit, it seems to prefer doing everything in a prograde fashion.

I expect such a mission to use quite a bit more fuel since you're going against the usual gravity slingshot assists and velocity assists taking off prograde from rotating planets and moons.

[SirJodelstein]

Umm, if taken literally, "all orbits must be retrograde" includes solar orbit. This would mean leaving Kerbins SOI at more than 9200 m/s to offset its orbital velocity. And then spending a similar amount on each planet SOI encounter to match the planets sun-relative velocity (or aeorcapturing at velocities that make DRE/FAR impossible)?

[MarvinKitFox]

hmmm. Delta-v penalties.

Kerbin Launch: 350m/s

Mun:

-capture: 1000m/s

-landing: 20m/s

Minmus: Capture 550m/s

-landing: 20m/s

so you could visit all sport inside Kerbin's SOI for a cumulative penalty of only about 350+2*(1000+20)+2*(550+20)=3520. Very doable.

HOWEVER, put one toe outside Kerbin's SOI, and you are in trouble!

Getting to Duna:

Normally, getting from Kerbin's SOI edge to Duna's SOI edge only costs 110 delta-v.

Now it will cost you.. 2*9284 + 110 + 2*7500 = 33678

That is right on the very edge of feasibility, using ion drive.

Getting back....... your ship would need a blob of xenon larger than Jool, at launch.

(for moho, the penalty is well over 60000 m/s, and well into Plaid)

Edited September 14, 2014 by MarvinKitFox

[Kasuha]

There's nothing special about retrograde parking orbits, at the end of any transfer you are free to decide which direction you want to end up orbiting your target for no extra dv. And since most bodies in the system rotate rather slowly, it's almost irrelevant even for landing. If you have a ship that can do a grand tour of the system, you can almost certainly do a "retrograde" grand tour with it as well.

Of course, Sun-retrograde interplanetary transfers or Jool-retrograde transfers between moons would be absolutely insane. But I kind of doubt that's the requirement in this challenge as regardless of direction of the transfer, as soon as you park around any planet or moon, you're already traveling prograde relative to the higher level body (Jool, Sun).

[MarvinKitFox]

There's nothing special about retrograde parking orbits

2/3 of my (equatorial) Mun orbits are retrograde

This is because I launch to a free-return Mun approach, and only commit once I'm happy everything is working out. This leaves me in a retrograde orbit.

BUT i do start from a prograde Kerbin orbit.

[Galane]

hmmm. Delta-v penalties.

Kerbin Launch: 350m/s

Mun:

-capture: 1000m/s

-landing: 20m/s

Minmus: Capture 550m/s

-landing: 20m/s

so you could visit all sport inside Kerbin's SOI for a cumulative penalty of only about 350+2*(1000+20)+2*(550+20)=3520. Very doable.

HOWEVER, put one toe outside Kerbin's SOI, and you are in trouble!

Getting to Duna:

Normally, getting from Kerbin's SOI edge to Duna's SOI edge only costs 110 delta-v.

Now it will cost you.. 2*9284 + 110 + 2*7500 = 33678

That is right on the very edge of feasibility, using ion drive.

Getting back....... your ship would need a blob of xenon larger than Jool, at launch.

(for moho, the penalty is well over 60000 m/s, and well into Plaid)

Thus the challenge. Could you cancel out Kerbin's orbital velocity and let Kerbol's gravity pull you in to an intercept with Eve or Moho then get into a retrograde orbit around them? Of course to do that you'd have to thrust the ship prograde to catch the planet.

[metaphor]

hmmm. Delta-v penalties.

Kerbin Launch: 350m/s

Mun:

-capture: 1000m/s

-landing: 20m/s

Minmus: Capture 550m/s

-landing: 20m/s

so you could visit all sport inside Kerbin's SOI for a cumulative penalty of only about 350+2*(1000+20)+2*(550+20)=3520. Very doable.

HOWEVER, put one toe outside Kerbin's SOI, and you are in trouble!

Getting to Duna:

Normally, getting from Kerbin's SOI edge to Duna's SOI edge only costs 110 delta-v.

Now it will cost you.. 2*9284 + 110 + 2*7500 = 33678

That is right on the very edge of feasibility, using ion drive.

Getting back....... your ship would need a blob of xenon larger than Jool, at launch.

(for moho, the penalty is well over 60000 m/s, and well into Plaid)

You wouldn't need that much delta-v for interplanetary transfers. You could just get into an orbit barely skimming the surface of the Sun (and retrograde) for about 9 km/s from low Kerbin orbit. Then when you're at Sun periapsis raise your apoapsis to Duna/another planet which should only take a couple hundred m/s.

[stanleywinford]

You wouldn't need that much delta-v for interplanetary transfers. You could just get into an orbit barely skimming the surface of the Sun (and retrograde) for about 9 km/s from low Kerbin orbit. Then when you're at Sun periapsis raise your apoapsis to Duna/another planet which should only take a couple hundred m/s.

This. The Oberth effect is very powerful.

[stanleywinford]

Mistress Mary, quite contrary.

One point for each body visited and orbited.

One point for each body landed on and returned from.

Do flybys count for points, or do you have to get into orbit? If I land on a body but can't return to Kerbin, does that count for any points? What if I land on a body and get back into orbit, but can't get back to Kerbin?

[Galane]

Have to get into orbit. Have to get back from all landings.

I didn't mention returning to Kerbin so I'll stick to that, though I'm sure any Kerbals you send on this flight would appreciate coming back home.

[MarvinKitFox]

You wouldn't need that much delta-v for interplanetary transfers. You could just get into an orbit barely skimming the surface of the Sun (and retrograde) for about 9 km/s from low Kerbin orbit. Then when you're at Sun periapsis raise your apoapsis to Duna/another planet which should only take a couple hundred m/s.

true, i stated the case for direct hohmann (reversed) transfers.

Using a very low Kerbol orbit would cost you just over half as much, both for going there and for intercept on arrival.

With eve, kerbin, duna, jool(also laythe), you can even use aerobraking to virtually null the intercept energy.

Still be rather hard, and I'd **really** like to see anyone manage a return trip to MoHo under this ruleset.

[Galane]

Nice to see people thinking outside the command pod about how to do something.