Better Stock Crafts 2: This Time it's Personal!

[advil]

I forgot to mention something about my craft. As you can see in the cropped image here, all four of the tug robots are connected with a stack decoupler, I flipped those upside down so the left over part stays attached to the center portion rather than the tug. The upper docking port is underneath that so it is not visible until the unit is decoupled. Each unit gets detached one at a time by hitting space. Once a unit is detached you will want to switch to it and turn on the SAS and RCS and stop it from drifting or else it will slowly drift backward away from the main ship. On these modules I went with surface PVs and batteries to avoid having an excess of parts sticking off of the sides such as retractable PVs which enables the tugs to get in close and attach to other parts. I will also note that the two tugs that have a liquid fuel engine also have two chutes on them to enable returning small parts and even capsules holding kerbals safely to the surface but I have not tested that so would recommend quick save and try to aim for water.

Also don't forget to activate the engine while throttled down or else you will take off once you turn it on.

[manni01]

manni01: Completely separate from the competition I love that your tug somewhat resembles an R2 unit Or maybe I'm just seeing what I want to see.. the fact that you were able to incorporate all different sizes of docking ports puts you ahead of the rest of us because rather than purpose build, this tug can just go up and grab onto whatever it needs to. I suppose depending on the mission all one would need to modify is the lower stages. If I was planning an orbital station at Duna for example I would need more fuel to get one of these guys there but it would get the job done once there. I'll have to check out the maneuverability for myself when I can as that is one of the most important aspects when you're trying to grab onto something and move it. Have you had trouble towing anything from the side with those two small docks?

Thanks, and I haven't really had a problem. The small docking ports are rarely used, but when they are used, they are often attached to small crafts, and the center of mass won't be alter too much (don't forget the 40.5 torque). Also, if it you really have problems, dock the same craft to the other docking port. I should maybe mention that if you use the tug to pull/push any payload without rcs ports, you will find your craft rotating because when you have a decently big payload without rcs, the rcs thrust will not be aligned with the center of mass. The Energy module I brought to the space station was a fairly heavy one because of the fuel tank, yet in docking it preformed pretty easy. just mentioning it.

[advil]

Thanks, and I haven't really had a problem. The small docking ports are rarely used, but when they are used, they are often attached to small crafts, and the center of mass won't be alter too much (don't forget the 40.5 torque). Also, if it you really have problems, dock the same craft to the other docking port. I should maybe mention that if you use the tug to pull/push any payload without rcs ports, you will find your craft rotating because when you have a decently big payload without rcs, the rcs thrust will not be aligned with the center of mass. The Energy module I brought to the space station was a fairly heavy one because of the fuel tank, yet in docking it preformed pretty easy. just mentioning it.

I guess what I was getting at is if you were trying to move something long distance or de-orbit it you might find that the whole thing is trying to rotate because of the additional mass off to one side. I ran into this with one of my mother ships trying to bring a lander in closer to a moon, lander was docked along side it and it started off okay but as the burn progressed my ship started to turn in the direction of that additional mass. Considering both craft had RCS and the huge difference in mass between the two.. Where's a picture..

Right. So take away two of those landers. I wouldn't have thought that additional mass would do as much as it did. I tried deactivating RCS on the lander, even tried rolling it's fuel back into the mothership, I tried activating the engine on the lander and varying it's output. Nothing helped.

I'm thinking you can't move much with it docked to the side.

Also this is the HMS Ganymede capable of hauling up to 10 Kerbals all the way to Jool for science and returning to Kerbin orbit on a single tank of gas It's also capable of operating unmanned. But this isn't the thread to talk about motherships in. I digress.

[John FX]

Make a craft that demonstrates a space-tug that can dock either two stock Space Station Cores together, or dock a stock Space Station Core to a pre-existing space station, then either de-orbit or dock to another node on the station.

Ok, So my tug will have the ability to reach GKO, dock with an unspecified space station core, move it with precision and dock it with another craft (which I will assume has SAS on) It can then de-orbit itself from at least GKO. I will try to include the ability to move a relatively small station core from LKO to GKO.

[Pecan]

...dock with an unspecified space station core...

"Stock Space Station Core" is not unspecified, it is specifically the "Space Station Core" VAB vehicle supplied and marked "[stock]" when you click load.

[Pecan]

...all four of the tug robots are connected with a stack decoupler...

...so would recommend quick save and try to aim for water.

Why decouplers, they alreay have docking ports, don't they? If never required to re-dock then just the ports on the robots will be sufficient, otherwise ports on the core would add flexibility (not that it's part of the task).

On landing, note that KSP's physics can be a bit harsh on splashdowns. Like the Soviet Union in real life, most people in KSP prefer dustdowns.

[advil]

Why decouplers, they alreay have docking ports, don't they? If never required to re-dock then just the ports on the robots will be sufficient, otherwise ports on the core would add flexibility (not that it's part of the task).

On landing, note that KSP's physics can be a bit harsh on splashdowns. Like the Soviet Union in real life, most people in KSP prefer dustdowns.

Good question, and one I was already prepared to answer. It's two things really. First, If you have ever launched something with another part attached with a docking port you will notice that it tends to dangle there like an uncooked hot-dog, or some other non scientific thing. That is something I didn't want to be given crud for, since we are nearly to the end of the contest and beginning to split hairs.

The second reason, as if the first wasn't sufficient is that I didn't want to have to bother with turning crossfeeds off and on and didn't want the central portion to draw fuel off of the bots during flight. Mostly though i don't like floppy space ships.

[John FX]

"Stock Space Station Core" is not unspecified, it is specifically the "Space Station Core" VAB vehicle supplied and marked "[stock]" when you click load.

Oh, cool. I`ll get one of those in orbit now. Thank you.

EDIT got two in orbit and I`ve made it hard for myself. I`ve decided to have to dock two cores that are both on a 120km orbit but about 30 degrees apart. On top of that the tug is on the other side of the planet and I have decided that the whole station, after docking, has to be taken to a geostationary orbit and then the tug deorbited with one of the station cores which was found to be defective on the way up so now jeb will have to stay with bill and bob.

Here is my starting position.

Edited July 9, 2014 by John FX

[manni01]

I guess what I was getting at is if you were trying to move something long distance or de-orbit it you might find that the whole thing is trying to rotate because of the additional mass off to one side. I ran into this with one of my mother ships trying to bring a lander in closer to a moon, lander was docked along side it and it started off okay but as the burn progressed my ship started to turn in the direction of that additional mass. Considering both craft had RCS and the huge difference in mass between the two.. Where's a picture..

http://i.imgur.com/2sn5Xkd.jpg

Right. So take away two of those landers. I wouldn't have thought that additional mass would do as much as it did. I tried deactivating RCS on the lander, even tried rolling it's fuel back into the mothership, I tried activating the engine on the lander and varying it's output. Nothing helped.

I'm thinking you can't move much with it docked to the side.

Also this is the HMS Ganymede capable of hauling up to 10 Kerbals all the way to Jool for science and returning to Kerbin orbit on a single tank of gas It's also capable of operating unmanned. But this isn't the thread to talk about motherships in. I digress.

I get what you mean, but the tug has 1.25 m and 2.5 m docking ports. The 0.65 m docking ports will usually have 0.65 m payloads which really don't weigh much. plus your mothership doesn't have much torque other than the capsule torque. What i mean is there is a certain amount of torque needed for certain amounts turning it has to deal with. I'm no scientist, but rcs isn't really anything for torque, but rather for docking. In real life rcs is used, but thats because kerbal's reaction wheels are OP. Really, if you build a mothership, put a torque module on it (sounds like twerk module, eww).

[John FX]

So I finished doing the mission with my tug and it is a sweet machine. I could grab a station core and it felt light and easy to move, easy to move to different orbits without wobble, dock two cores together then move both of them to geostationary orbit, undock the tug and a station core and deorbit them both and still have over 1000Dv spare. I could have dumped the defective core on Duna...

Here is a gallery The first few images are from an older version of the craft but they show direction changing well so I included them anyway.

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It can be placed in the stack and partially replace stage 3. It`s a functional, easy to launch stock tug. It has a normal docking port (green) and a large docking port (red), they are selectable with action groups 1 and 2 which select the direction

Just remember to select the lit up docking port and `control from here` (would be nice to have that change with the action group too)

Here is the craft file.

[Mathman]

recalled comment .. .. .. .. .. .. ..

Edited July 10, 2014 by Mathman

[Mathman]

Deleted......

Edited July 10, 2014 by Mathman

[Mathman]

I like it. The launch platform even looks smooth. Has every size dock but an AGU, and who needs to attach asteroids to space stations?. The mission illustrations are detailed. The mission does not illustrate either of the two challenge missions but it is clear that the Adaper Tug MKIII would be able to do that too. As long as the people being towed behind the nuclear engines don't mind glowing green that is. Oh.. they already do.

Mathman

[Mathman]

I had an even more unbalanced conglomeration in another personal challenge. The main propulsion module was nuclear powered for high efficiency but I was hanging a spaceplane on the side with almost half the mass of the main module. I had designed the spaceplane and nuke module with a good bit of torque (over 50 Nm each), which helped. What also helped was to keep the thrust from the spaceplane from overriding the thrust from the nuke, I set the thrust limiters on the spaceplane engines to a value which balanced the thrust. iT CAN BE DONE. Something to keep in mind when making modular mission craft. (sorry, no photos left)

[Pecan]

Mathman - I find it hard to follow what you are saying because I don't know to whom these are addressed. Can you please quote the posts you're replying to or at least tell us! (eg; "I had an even more unbalanced conglomeration than manni01's in another personal challenge.")

[advil]

John FX how did you make the docking ports light up different colors like that? I've never seen that before.

[Mathman]

First, my apology to folks I have confused by not posing on the right part of the thread. I still may be doing it wrong, but this post should be closer.

re: Why should Sirine just use any old space station with any old adapter? or What does "stock" have to do with the garden?

----------------------------------------------

The "stock" applied to the tug, not the target so the garden module is only an example of something to which a stock core is to be attached to, assume the garden module is to be considered a "pre-existing space station. I have no problem with the garden module not being stock. However, the wording of the mission was that the space station core had to be maneuvered. I quote "Make a craft that demonstrates a space-tug that can dock either two stock Space Station Cores together, or dock a stock Space Station Core to a pre-existing space station. This does not include docking a non standard item to a space station core.

I don't, however, see why you complain. Redesigning to have a standard port is no big thing. just do it. It doesn't matter to me if you have all three sizes or just one on the end item. See my flying gold plated pig if you want to see and omnibus tug with all 4 docks/grapers. ;-) https://www.dropbox.com/s/xrrwjs2sdmd2xc7/FP%20Tug.zip https://www.dropbox.com/s/zz2cbzxbwz3njhg/FP%20Tug.zipBe inventive. Have fun.

However! if we are not going to follow the established 'rules' of the competition, why bother compete?

As for bringing up other competitors disqualifications - perfectly fair in competition. Get used to it sir. Get used to it.

Mathman

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Edited July 10, 2014 by Mathman

[Pecan]

@ advil - right-click lights in the VAB/SPH to tweak their colour and intensity.

@ Mathman - thank you; I have been wondering why you and I seem to be the only people who read the OP throughout this thread. On the other hand, GregroxMun seems to have walked away in horror ^^.

[advil]

@ advil - right-click lights in the VAB/SPH to tweak their colour and intensity.

Awesome, I'm going to have to play around with that this weekend

Also: Question for everybody. What are the advantages of the different sizes of docking ports (if any). I realize that there are different sizes to match up with different diameters of payloads, just like different sizes of stack decouplers. But I have been using the smallest all along. I think mostly because it's the first one I unlocked in career mode, but second because I haven't felt like I needed a larger one. Are the larger sizes stronger? Do they begin to attach from further away? Do they provide a greater crossfeed rate? I'm just trying to determine for myself here if there is really any point in me using the larger sizes.

[advil]

It's almost midnight, when do we get to vote on this piece?

[Sirine]

It's almost midnight, when do we get to vote on this piece?

OP seems to be away.

[manni01]

Awesome, I'm going to have to play around with that this weekend

Also: Question for everybody. What are the advantages of the different sizes of docking ports (if any). I realize that there are different sizes to match up with different diameters of payloads, just like different sizes of stack decouplers. But I have been using the smallest all along. I think mostly because it's the first one I unlocked in career mode, but second because I haven't felt like I needed a larger one. Are the larger sizes stronger? Do they begin to attach from further away? Do they provide a greater crossfeed rate? I'm just trying to determine for myself here if there is really any point in me using the larger sizes.

Two things: 1. you didn't unlock the smallest ones first (you unlocked the medium ones first) 2. if you use 3.5 m things with 0.65 m docking ports, any rotation or nonlinear (basically anything) thrust will make your craft wobble way too much and its really hard to get out of it it too(like pushing a chain). You seem like a person who just docks for space stations or refueling. The bigger docking ports provide more rigidity which is essential for big motherships with a lot individual components.

[manni01]

good that I'm in europe; its 10 am for me

[advil]

Two things: 1. you didn't unlock the smallest ones first (you unlocked the medium ones first) 2. if you use 3.5 m things with 0.65 m docking ports, any rotation or nonlinear (basically anything) thrust will make your craft wobble way too much and its really hard to get out of it it too(like pushing a chain). You seem like a person who just docks for space stations or refueling. The bigger docking ports provide more rigidity which is essential for big motherships with a lot individual components.

My main reason for using the docking ports is to attach either space station parts, or to attach a craft in orbit to something else to re-fuel or transfer kerbals / science. I have used them to de-orbit things before but I have noticed wobble and weakness at the joint no matter the diameter or mass of the object. It is good to know that the larger ports provide more rigidity though.

[advil]

In the spirit of good sportsmanship we should all agree to NOT vote for our own entry. Thoughts?