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The Afrodite Project (1-way interplanetary trips) [Stock .17 / MechJeb + Protractor]

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Ok, after some days without playing KSP , even with the new version bells and whistles ;), I decided to go back to the issue of doing a Eve-going ship ( yeah, I know that there was already someone that gone there and back ... ) ... but I was sidetracked by the more basic problem of making compact and lightweight 1-way interplanetary ships ( by the fact that you need one of those as the return vessel to Kerbin :P ). I actually had some designs from the .16 time ( I have a unmanned Evenera series to be posted someday that was the basis of this one ), but what really pushed me on this was

where he got to Kerbin orbit with enough fuel for a interplanetary burn with a 1m capsule , a big tank ( they call it Rockomat or something in this days ... ) and a aerospike. OFC that if you don't want to end the mission by breaking the ship like he did, you need to add some more things, but the amount of fuel needed became a benchmark for my testings. And I obviously started by testing for reaching celestial bodies with a surface and a decent atmosphere ( because Kerbin is one of those ): Eve, Duna and Laythe...

So without further delay, I present you the Afrodite series ( I know for you English speaking people, it is Aphrodite, but in my native language we use a f ;) ), starting with Afrodite IV ( the previous 3 were test versions that were far inferior to this two ):


It actually has 12.5% more fuel than Manley minimal rocket but also has more weight due to the things you need for a lander and some you don't ( like the decoupler for emergency use if the rocket gets out of fuel ;) ), so it is a fair trade IMHO ( BTW I tried a version with 1 + 6 fuel tanks ( that is 87.5% fuel of the Manley rocket ) but it came short of my Munar test ( that is: if your ship can land on the Mun and come back to Kerbin it has the dV for a 1-way trip to any place in the Kerbin system so far ... if you don't expect that the rocket fully powers the braking when you get there ) so I scrapped it ). The 8 lateral tanks feed on the central one in asparagus fashion . The ship can get quite unbalanced when you drop empty tanks ( it gets the occasional collision if you're flying manually ) so I would not recommend to use this ship without mechanical help unless you are a good pilot ( I am not that good :P ).

Anyway I sent Bob to do a Eve mission after the Munar and Minmus tests on this ( Jeb and Bill were already testing the Afrodite V ), and after a quite bumpy trip with 5(!) aerobrakes in Eve atmosphere and a lot of unneeded corrections, Bob sent a postcard of the sunset in Eve:


( btw, as you can see, I'm using mechjeb and the protractor mods. Mechjeb because, like I said, the ship can get problematic in the ascent and the protractor not because of the angles ( I can get those from the math or, if I'm lazy, from the web-based calculator ) but because it gives the distance for the closest approach of the orbit you are in to the planets ... and that is invaluable intel for the inevitable corrections for getting to the SoI of anything that isn't Jool ).

In spite of successful, the Afrodite IV showed some flaws. The powerful aerospike engine made the slight corrections that were needed to get to Eve SoI difficult to control leading to a lot of wasted fuel and the aerospike mass was a very significant part of the interplanetary stage total mass. Taking that in account, the Afrodite V was developed:


P.S By some reason the VAB pics have the parachute in top barely visible. The ships in the saves have it, don't worry ;)

It is basically a Afrodite IV with the central engine replaced by one LV-909 for the interplanetary stage, keeping the aerospike for the ascent stage. It has a even lower TWR than Afrodite IV ( that already has a dismal count of less than 1.2 ) and it gets a little less fuel to LKO, but the lighter engine makes up for that.

As Bob was already going to Eve, I sent Jeb to Jool ( for a Laythe landing ) and Bill for Duna ( P.S Actually Jeb went out first Bill the second, and Bob the third, given that the devs were cool enough to make that you can do a Duna 1-way mission and then a Eve 1-way mission in the time you take to get a ship to Jool if you launch in the first window possible ( between day 45 and 50 (?) with a gap in between because the Mun and Minmus get in the way ) ). Both sent some postcards of the sunset there:



The Duna mission was the least dramatic of them all: one aerobrake and a smooth landing ( Bill will tell otherwise, since he only stopped freaking out after he got in EVA ). I even got the ship up to a Martian low orbit ( 51*51 km ) after that with the ship having 37 L of fuel left. The Laythe one ... well I accidentally got of a Laythe encounter while still in the orbital plane corrections, so I called it a go. Only when I got close enough of Jool, I noticed that the encounter was after the ship passed 15 million Km above the Jool south pole and in a grazing passage in the inside side of the Laythe SoI ( hence it was expected to have 5+ Km/s when entering Laythe atmosphere ). After two very dramatic aerobrakings ( both around 8 g ) I finally got in a decent descent to a small island in the southern hemisphere. And obviously Jeb was all smiles in between all of this :D

To end, things to solve:

- Neither of this ships would get out of Eve :( The TWR in Eve would be less than 1, not counting with the extra atmosphere to drag out ... ;). It probably would not have the power to get out of Moho and return to Kerbin even if the engines would not melt down ...

- Most likely neither of this ships can land on Moho or any of the massive Jool moons that have no atmosphere if you launch it from Kerbin. Like I said before, both of this ships have the dV requirements to get to the orbits of all of the bodies above in a good day, but : a) Moho inclination requires a good bunch of extra dV to compensate and in the tests I made, the fuel left after the interplanetary burn was not enough to correct it ( technically you could always wait for a encounter when the Kerbin and the Moho orbital planes cross, but I didn't had the patience to way for that ), B) the fuel budget for those bodies is not enough for a powered descent ( well, it might be enough for the Jool moons if you aerobrake in Jool and have the luck of getting a encounter right there, but it will be a tight one most surely ). Bop could work, though ... and Gilly as well, if you could actually land there :( The final fuel budget in the Duna mission also points to the feasibility of a Ike landing after a well timed aerobrake in Duna.

- You can't put anything below a aerospike. To whoever in Squad designs parts ( most likely C7 or Nova nowadays ) for when a aerospike with a casing that allows to attach stuff below, like the other engines ( or, if you want to go basic, for when a aerospike that actually attacks to the other parts without crazy tricks ? :P ) ? I've seen some motors with casings in the modded parts somewhere, so why not ? Anyway,, this complicates a lot the job of putting a decently performing rocket below any of this ships :/

- Unfortunately you can't just scale up for the 3m capsule. For starters, unlike the 1m tanks you can't put 8 3m tanks around a single one even the lengthiest of the decouplers we have in stock ( the ones from the planes parts ) ... then there is no 3m aerospike ( aerospikes are the more efficient takeoff rocket engine, far surpassing any of the LVs by weight unit ) and the weight ratio between the tanks and the capsule is different for 3m than it is for 1m ... Will need some extra work, definitely

Anyway, this is getting too lengthy ... Here are the files, neatly packaged in zip files. Both contain the stock version and the Mechjeb + protractor version I actually used for those pics :

Afrodite IV

Afrodite V

Hopefully I'll make some more of this series :D I definitely want to make a 3m counterpart of the Afrodite V atleast ...

EDIT: Subsequent developments gave us Afrodite VIII and IX. You can find them some posts below

Edited by r_rolo1
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Well, I am pretty sure that both could go with one less fuel tank atleast for Duna and maybe Eve ( I got to Laythe with a pretty low fuel budget ) , but asparagus does not like even numbers ( 1+7 ) :/ Well I could do 1 + ( 1 + 6 ) ... let me try :D

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Ok, after some extra development, I present you Afrodite VIII:


and Afrodite IX:


As you can see, significant decreases in the fuel budget were made but both ships are able to get to Laythe and land there. In fact I made a double mission to Laythe with both ships:

First of all I forgot to take pics until the interplanetary burn of the first ship... Anyway, after the Afrodite IX burn it made a very close flyby of the Mun:


It was not planned ( basically the Mun SoI got in the way ), but it meant that the two ships, with only 8h of difference in launch, got to Jool with almost 40 days of interval ( Afrodite VIII got a far less close flyby ). I would had preferred that the Mun had not gotten in the way TBH.



Afrodite VIII orbit after burn and fuel in stock


Afrodite IX orbit after plane correction and minor adjustments. Laythe encounters are relatively easy to get, fortunately.



Orbit after entering Jool SoI and after corrections. Almost 48 L of fuel left, that is perfectly enough if the aerobraking is done well.


Details after entering Laythe SoI. A minor burn to reduce Pe made for a 7.1g aerobrake and a almost polar orbit with a decent 2g landing:




Using mechjeb landing autopilot to deduce where in Laythe the predicted landing spot is in preparation for corrections for a landing on dry ground ... and with so little fuel we can't let mechjeb to do the manouver ( it tends to burn idiotically to change planes ). I ended correcting a little to land in the island to the left of the landing spot in the pic.


Parachuting in ...



Bill postcard with Jool in the backround and fuel left.

Meanwhile Afrodite VIII was still going ... btw I got a very infuriating ... er, feature of the game that decided to recalculate the orbit of the ship when I got to +/- 7 days before getting to Jool SoI making it 29 days to Jool (!) and wasting my Laythe encounter. Attempts to correct it were sucessful ... until 12h later when it got to the same 22 days of difference ( note, all of this while still supposedly "on rails" orbit. I even tried to warp while focused in other ship but the result was the same ). So I ended passing the last 7 days of the Jool approach trying to correct this issue and ended spending almost 20 L of fuel in this feature. I'll post a bug report later ...

Anyway, here is my hardly maintained Laythe encounter when I finally entered Jool SoI and escaped those crazy orbit recalcs:


Because Jeb was already tired of being in the ship ( and because I was pretty frustrated with losing half a hour making corrections to workaround a bug ) and because he wanted to show he was more of a [email protected] than Bill, he wasted a perfectly fine Laythe equatorial approach ( the best one I got so far ) in a 19 g reentry in Laythe ( to that island in the center of the screen ):


A final 2001-style pic before entering Laythe atm. Jeb is ecstatic about the prospect of doing a 19 g reentry , as you can see :D


Parachuting in ...


And postcard, with Jeb all smiles of showing Bill how it's done. The ship had a little more than 50 l of fuel left ... I am certain that in normal non-buggy conditions it would end with more than 60 l


And the two ships in orbital view. Bill and Jeb will have to swim a lot to get to each other :/


As you can see the sacrifice of the safety decoupler alone allowed for saving almost a small tank of fuel ( note that the two ships have not the same fuel budget ). I think it is possible to shave a little more of fuel, but the margin of manouver is already quite slim on Afrodite IX and most likely I'll not risk it much more ;)

Saves below. Like the Afrodite IV and V, both links have zip files with both a stock and a mechjeb +protractor modded version ( the one I actually used in both cases )

Afrodite VIII

Afrodite IX

To be honest I think that Afrodite VIII is a pretty decent return stage for a Laythe trip. Just have to find a way of putting a rocket below ... :/

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These are pretty small, is this all that is needed to go from Kerbin to another planet, are they landers, or do you attach larger fuel tanks and engines to leave Kerbin orbit.:confused:

Yup, those are the whole rockets ;) Note that this are for 1 way travels and only for celestial bodies with a atmosphere, 2 things that reduces the dV requirements to the scale of a Mun landing and back rocket even for a Laythe trip ( Eve and Duna require even less ). They require some precise manouvering ( especially the IX version ), so automation is advised atleast in the ascent ( that is by far the trickiest part ), but even good human piloting could work with this ( just see the video from Scott Manley I linked in post #1 for a similar fuel budget in a human hand )

I'll try to put you Afrodite VIII on something i have if you are not against.

Feel free to ;) What gripes me more about this is the fact that you can't put anything below a aerospike, a thing that makes designing a delivery rocket below a bigger challenge ;)

Edited by r_rolo1
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Thanks for the compliment ;)

I must say that I left some details out of the reports that actually make a difference ( well, seasoned pilots will get there without my assistance, though ... ), especially on the Laythe trip.

First of all , the orbit I always strived to get around Kerbin while waiting for the interplanetary burn was always the closest of 70*70 km as possible, both to use the less fuel possible to get into orbit and to maximize the gains from the Oberth effect.

Second, the corrections to the planetary approach should be done the earliest possible except for the plane alignment, that obviously should be done when your orbit plane and the target planet one cross ), in spite of the fact that the current game UI makes that hard as hell. Earlier corrections = less fuel used.

Third, you must strive for a Jool equatorial approach in the Laythe case, because that maximizes the chances of getting a Laythe encounter without having to spend a lot of fuel in corrections searching for it ...

And, obviously , get your conics draw limit high enough to actually see the details of the encounters and the exit orbit planes better ( I have it on 7 (!) ). That is pretty useful in Laythe case because Jool equatorial plane is pretty close of his orbital one and the Laythe orbit is also pretty close of the Jool equatorial plane. SO, if your Jool approach orbit and the post Jool orbit are in the same plane, your Jool SoI part of the orbit will be pretty close of the Jool moons one ( except Bop ), a thing that maximizes the number and the length of the encounters with them .

Edited by r_rolo1
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My only comment is on the weight of fuel lines, decouplers, and empty small tanks. They're comparable.

In my experience, it's rarely worth dragging decouplers and fuel lines for small tanks. I'm curious how the Afrodite IX would perform with four full 400L tanks as its launch stage.

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I made that experiment ( it was Afrodite VII IIRC ) and it actually was slightly worse than Afrodite IX ( not by much but it got to the parking orbit with less +/- 10 L of fuel ) . The fact that you are dropping unneeded dry mass earlier makes up for the extra initial mass pretty soon ... if you used the 4 400 L tanks you would have to drag the dry mass of two of those tanks until you could ditch them due to symmetry reasons, unlike in the 8*200 L design where you drop the equivalent of a 1 400 L tank dry mass out per stage .

Edited by r_rolo1
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