Think i discovered a way to do cheaper interplanetary transfer

[Kiershar]

Basically its doing a direct ascent to the Mun and then warping trough it at x100k time with near Kerbin escape velocity. Can be done toward the inside planets and outer planets and it saves about 500 delta v over direct ascent. Was this discovered before?

The steps :

- Line up Kerbin and the destination planet at the correct phase angle

- For inner transfer, launch closest to midnight possible, for outer transfer launch closest to noon.

- Line up the moon so your launch site is leading it by 10-20 degrees (faster speeds needs slightly less degrees, but too much speeds might make you overshoot orbits like duna's)

- Do one burn all the way to the moon, aim for center mass until it starts flipping out your inclination but do not flip it, just stay at the very edge (At this point the orbit predictions will lie to you, do not believe it)

- When properly lined speed up to x100k time and the ship should pass right trough the mun

- Reach sun orbit with relative boost to speed, wait till periapsis and correct for planet's SoI interception.

Pretty easy to do, not much turning involved. Its not exactly 100% legit, I guess, but it works reliably. Call it quantum warping? Getting the full benefits of the Mun's gravity and velocity while passing trough the matter. 500 delta v is kinda a big deal right? Anyways, i'm not sure if this was discovered before. If not i call this cheaty transfer the kiershar transfer Will post screenshots and stuff if anybody is interested and can't reproduce it.

EDIT : Here's an album showing how i perform the transfer : http://imgur.com/a/TxLlI

Pre launch

Slinger mk1 : http://i.imgur.com/9TQfq.png

Duna phase : http://i.imgur.com/HWw71h.png (i overshot duna by a little but it would still work with some corrections)

Launch at Noon ish leading the Mun : http://i.imgur.com/5PMEOh.png

Post Launch - Pre warp

Finished launch burn, aimed at moon center mass http://i.imgur.com/RaRAph.png

Orbit prediction pre-warp, it lies http://i.imgur.com/DddOQh.png

Post warp

Orbit prediction adjust itself. Pretty close, could have hit Duna's SoI right away if i had eyeballed it better http://i.imgur.com/yFjmVh.png

Proof of having only used the Rockomax. Still some delta-v in that to perform corrections http://i.imgur.com/Tzxz3h.png

Edited October 3, 2012 by Kiershar

[Pingonaut]

Good find, but I wouldn't use it, since it's exploiting the fact that you pass through planets and moons at 100 times time acceleration.

[zapy97]

wait wait wait are you kiershar as in does minecraft tutorials about pvp traps with redstone?

well anyway it is hard to be at the correct allinement to do it but it is possible

[Kiershar]

wait wait wait are you kiershar as in does minecraft tutorials about pvp traps with redstone?

well anyway it is hard to be at the correct allinement to do it but it is possible

Yea that's me

The alignment does not take much time to achieve. You line up the destination planet with max warp, then you line up the moon and noon/midnight with slightly less warp speed. I eyeball my transfers all the time because im sloppy and lazy but they work. Most of times anyways.

[-Gamah]

Jeb is excited about passing through the moon.

*awaits the new "you cannot warp beyond 50x with no periphrasis" tooltip*

Edited October 2, 2012 by -Gamah

[Kiershar]

Nobody tried it out? I though this was a big deal. I mean, i can get unto Duna's Orbit with the delta-v budget most ships takes to just circularize around Kerbin. Is there even more efficient ways to do transfers?

Anybody wants to give it a shot? skip the first step and just lead the Mun by 10-20 degrees and launch at noon, check your apoapsis after the maneuver. It's really not hard to execute.

[princessjane]

I've used mun gravity assisted transfer's before. I don't know if it's more efficient but i think it would be close.

[RoboRay]

Why would exploiting this bug be a big deal for people to try out? If people want to cheat, there's a menu for that.

[Moach]

well, this is something of a big deal -- you have found a bug! -- enjoy it as you'd like before this gets patched up

using the Mun's gravity well to sling out into a further orbit is a real thing tho - and since it has no atmosphere, you can get pretty low (should be safe to go as far down as 1km PeA)

at this altitude, your velocity should be quite high - this is good, grip that throttle handle and open up! -- for the faster you're moving through the gravity well, the more "bang" you get for your proverbial "buck"

but going 'through' the Mün is as cheatful to me as using infinite fuel.... i mean, knock yourself out - but it's a cheat

cheers!

Edited October 2, 2012 by Moach

[LaydeeDem]

well, this is something of a big deal -- you have found a bug! -- enjoy it as you'd like before this gets patched up

using the Mun's gravity well to sling out into a further orbit is a real thing tho - and since it has no atmosphere, you can get pretty low (should be safe to go as far down as 1km PeA)

at this altitude, your velocity should be quite high - this is good, grip that throttle handle and open up! -- for the faster you're moving through the gravity well, the more "bang" you get for your proverbial "buck"

but going 'through' the Mün is as cheatful to me as using infinite fuel.... i mean, knock yourself out - but it's a cheat

cheers!

Well, I will enjoy hitting the Mun at high warp when the bug is fixed.

[maltesh]

well, this is something of a big deal -- you have found a bug! -- enjoy it as you'd like before this gets patched up

using the Mun's gravity well to sling out into a further orbit is a real thing tho - and since it has no atmosphere, you can get pretty low (should be safe to go as far down as 1km PeA)

at this altitude, your velocity should be quite high - this is good, grip that throttle handle and open up! -- for the faster you're moving through the gravity well, the more "bang" you get for your proverbial "buck"

The thing is, you were moving faster, in a deeper gravity well, when you were over Kerbin, and your fuel would have been more efficiently turned into kinetic energy back there. If you start at Kerbin, there's no point in doing a powered gravity assist with either of Kerbin's moons.

[The Destroyer]

I have gone through the mun before. in 0.14.

it happened when going at high speed, trying to land, then lag got me, and i went right through the mun.

I also noticed in 0.16 that when i ejected my skycrane, it was actually orbiting, but going INTO the mun.

Sure, this is a good booster, but lets face it, who wants to use a bug to get there? i never used the fuel glitch either.

(jeb probably wants to tho)

[Kiershar]

The thing is, you were moving faster, in a deeper gravity well, when you were over Kerbin, and your fuel would have been more efficiently turned into kinetic energy back there. If you start at Kerbin, there's no point in doing a powered gravity assist with either of Kerbin's moons.

There is no burn at the mun, its all done from launch to low kerbin orbit while in direct ascent. I don't exactly understand what you're saying here about being more fuel efficient at Kerbin. I've done dozens of tests to get the maximum velocity out of a preset rocket and slinging into the moon as fast as possible is definitely the best option (and only option to reach Duna's orbit with my preset rocket, regular direct ascent always fell short a couple million km).

What is the most efficient way to spend fuel for interplanetary transfers? Get the lowest periapsis possible and burn there? I think i'm missing something here but every time i try to establish orbit of Kerbin it cost nearly the same delta-v as doing a direct ascent and build up to kerbin escape velocity.

[zapy97]

it isn't technically a bug it is a gravity slingshot basically it pulls you with its own momentum and that launches you further with less fuel

[maltesh]

There is no burn at the mun, its all done from launch to low kerbin orbit while in direct ascent. I don't exactly understand what you're saying here about being more fuel efficient at Kerbin. I've done dozens of tests to get the maximum velocity out of a preset rocket and slinging into the moon as fast as possible is definitely the best option (and only option to reach Duna's orbit with my preset rocket, regular direct ascent always fell short a couple million km).

What is the most efficient way to spend fuel for interplanetary transfers? Get the lowest periapsis possible and burn there? I think i'm missing something here but every time i try to establish orbit of Kerbin it cost nearly the same delta-v as doing a direct ascent and build up to kerbin escape velocity.

That was a response to Moach's comment about using the Mun as a gravitational slingshot. As a powered gravitational slingshot, burning from low kerbin orbit gives your spacecraft more kinetic energy than burning anywhere above the Mun's surface, as per the Oberth Effect.

As an unpowered gravitational slingshot target, you can't get close enough for the Mun's center of mass for it to give an appreciable boost at the speeds you should be travelling by that point for an efficient interplanetary trip. Minmus is even worse.

Is it possible to build a ship that can only reach the desired interplanetary target by slingshotting past the Mun? Yes. But nobody's going to be able to diagnose what the issue is with your spacecraft without at least a screenshot, and probably not without a screenshot and .craft flile.

[RoboRay]

it isn't technically a bug it is a gravity slingshot basically it pulls you with its own momentum and that launches you further with less fuel

The bug is not the gravity slingshot... it's flying THROUGH the planet or moon producing the gravity effect.

[Kiershar]

Ah sorry Maltesh, i derped there. You seem to know your stuff so maybe you can help me Before trying to phase trough the Mun i practiced doing Oberths on the Mun and I had noticeable boost for doing it at 3-5k altitude and i believe even non-cheaty Mun slingshots are definitely worth it.

Here's the craft and screenshot of the rocket. Using my transfer and only the Rockomax part i can set the ship on Duna's orbit which is around 20 million km orbit around the sun. With direct ascent/Kerbin escape and no Mun fly trough i can reach at slightly more than 17million km.

If you can figure out a way to set this ship unto Duna's orbit or kinda close using only the jet and Rockomax mainsail i would very much like to know how you did it. No using the lv-909, no decoupling from the Rockomax.

Ship screenshot: http://imgur.com/iKkDw

For reference, I fire the Rockomax mainsail at 2 TWR (Should be very close to the transition from pale blue to dark blue) and decouple the jet blocks at 2.2 TWR (about 3rd line in the dark blue)

EDIT : Here's an album showing how i perform the transfer : http://imgur.com/a/TxLlI

Pre launch

Slinger mk1 : http://i.imgur.com/9TQfq.png

Duna phase : http://i.imgur.com/HWw71h.png (i overshot duna by a little but it would still work with some corrections)

Launch at Noon ish leading the Mun : http://i.imgur.com/5PMEOh.png

Post Launch - Pre warp

Finished launch burn, aimed at moon center mass http://i.imgur.com/RaRAph.png

Orbit prediction pre-warp, it lies http://i.imgur.com/DddOQh.png

Post warp

Orbit prediction adjust itself. Pretty close, could have hit Duna's SoI right away if i had eyeballed it better http://i.imgur.com/yFjmVh.png

Proof of having only used the Rockomax. Still some delta-v in that to perform corrections http://i.imgur.com/Tzxz3h.png

Edited October 3, 2012 by Kiershar

[maltesh]

I can't actually load the spacecraft as I appear to be missing parts it contains. "Kosmos.VA.Mumech.Autopilot."

However, of the stock liquid-fuel engines, the only thing worse for flight in vacuum than the Rockomax Mainsail is the jet engines. Once you're safely orbitable, you really should be using a different engine.

Most people wind up using the LV-N atomic rocket motor as the interplanetary transfer stage: With a vacuum specific impulse of 800 seconds, it's the most efficient space rocket in the stock game. Attatched to the same set of fuel tanks, you'd get almost three times the delta-V out of the LV-N in vacuum than the Rockomax can give you.

Swap out the LV-909 for the LV-N and in that last stage alone, you'd have a spacecraft with more than enough delta-V to go from low Kerbin orbit to Duna's surface, and land.

[Kiershar]

Ah my bad. It's using the mechjeb from the Kosmos pack. Well i added an album for people to see exactly how it worked out.

I'm very well aware of the delta-v performance of every engines, it's just that i benchmarked my transfer using this specific rocket. The mainsail is fired in atmospheric condition for quite a while also. The pieces above the decoupler is irrelevant because i'm not using them for the benchmark. I used a lv-909 because it has better TWR, making my tests a lot faster to execute. I use this most of times for landings : http://imgur.com/hmSk7

Anyways, check out the album really there's the magical orbit prediction swap after the warp and im pretty sure i'm gaining nearly the full moon velocity in delta v.

EDIT: I've reuploaded the ship with only stock parts. Just pop your own mechjeb on top of it, if you're still interested. I'd love to be proven wrong

Edited October 3, 2012 by Kiershar

[randyrules711]

Yea that's me

Can you verify this? If it's true, you could be the perfect person to help KSP get some more recognition. I know plenty of people who would enjoy this game but, won't risk buying it because there isn't enough media.

[Kiershar]

Can you verify this? If it's true, you could be the perfect person to help KSP get some more recognition. I know plenty of people who would enjoy this game but, won't risk buying it because there isn't enough media.

Send me a message to my youtube account i guess? Say "The fox is in the house" and I'll reply "The carrots are cooked".

I though about making KSP videos since 0.16 but my computer is not strong enough to handle decent recording and sometimes i get huge frame rates jumps that makes the footage real awkward. I'll likely make some videos in the future, not sure how much it would help KSP tho, as i'm not as popular as a year ago.

[maltesh]

Grabbed the Kosmos mechjeb. Flew it up on the jets about 10km, then lit off the main engine, dropped the jets, and began the gravity turn.

I probably would have done it sooner, but the thing spins like a whirling dervish, and I lost some fuel trying to get it back under control and wrangled eastward for orbit.

Gravity turn saves you fuel because your velocity isn't pointed directly downwards so the force of gravity isn't directly opposing the thrust you're applying, you're just letting gravity do something that you want to do anyway; pull your spacecraft so it's pointing the direction you want to go in. Almost every real-world spacecraft launch does this.

At any rate, circularized at about 80 km, then waited until I was about 1/8 of the way around the night side, then burned prograde until I got a hyperbolic trajectory. Moost real-world interplanetary spacecraft do their transfer burn from low earth orbit altitudes, and I can't think of a single one that's ever used the moon as a slingshot (Outside of movies that are terrible on their science, anyway)

Wasn't watching the map screen, so I overshot a bit when the tanks ran dry. Apoapsis 29Gm. Definitely could have pushed it farther if I'd stopped the spin and pulled off a more proper gravity turn, but it was my first time flying the craft.

Well, actually, it was my second time. The first time I didn't throttle down when dumping the jets and they took out the booster.

[Kiershar]

Very nice, how much fuel on the rockomax did you used to establish stable orbit? Never managed to perform a gravity turn good like you did.

[maltesh]

Didn't really check on it. I want to say about 3/4 of that last large tank. On a later flight, where I added four winglets to control that hideous spin, I was able to establish a booster orbit with almost the entire tank, but lost the flight when the decoupler ruptured under pressure.

A subsequent flight with four winglets and some extra struts managed to push the apoapsis to 31 Gm before running dry. Under a better pilot than I, I'm sure further distances are possible.

[Kiershar]

A couple days ago i came across an article while googling that said direct ascent was very slightly more efficient (by noise margin) than doing a Hohmann. I'm not too good at hardcore math but i was convinced then. Obviously the Hohmann is a lot more efficient with this evidence. I'm still thinking i can add up the velocity of the moon to that transfer by going trough it.

What's your rule of the thumb for doing the gravity turn? I can never seem to get it right.