Flotillas: A Primer in 3 Chapters PLUS APPENDIX FOR 0.25

[Geschosskopf]

I've just gone down a path more along the lines of "writing good notes to myself in the KAC 'notes' field for an alarm". I've even started using that just for notes about things, with no ship really required (though of course, hooked to one via KAC), such as "Jool Transfer Window in 7 days" -- "Verify that you've got everything in place and launch any manned craft you intended to send.."

Yeah, I do some of that myself. For instance, I typically set transfer window alarms, not tied to any ship, between all planets. This is so I can remember to get the next flotilla ready to go by then, or know when operations somewhere have to end for ships to come home. These alarms have a different icon from the slew of maneuver and SOI alarms on the list so are relatively easy to spot

Also, Rottielover: thanks for the props. And good points about kethane.

[Grunf911]

Awesome read, thx for that.

I think it would benefit from some pictures. I have actually made a similar guide on Reddit, so i figured not to duplicate content here, but add some Images to complement your text if that is OK

Guide Part 1: Preparations, Craft design, and Infrastructure

Guide Part 2: Destination Duna - or How did it go ?

I have launched pretty similar flotilla to both Duna and Jool. With Jool i am still struggling due to:

- Significantly less power from Kerbol

- Significantly less MicroWave power

- Much more TAC resources (food, water, oxy) needed

- Duna-Range RT2 Comm Dishes mostly do not work (need stronger ones)

- Trying to aerobrake at Jool, but keep hitting moons sometimes, still figuring out if it is a good thing

If you have any special tips regarding flotillas for Jool, I would love to hear them

Edited April 1, 2014 by Grunf911

[Geschosskopf]

I think it would benefit from some pictures. I have actually made a similar guide on Reddit, so i figured not to duplicate content here, but add some Images to complement your text if that is OK

[DerekL1963]

Have you considered updating this to take advantage of MJ's new porkchop plot feature?

[Geschosskopf]

Have you considered updating this to take advantage of MJ's new porkchop plot feature?

No, I haven't considered that because until this very moment I was unaware of its existence and now that I know, I still have no idea what it is. But I shall now go research this, figure out what it is, and how it might impact flotillas. Thanks for the heads-up.

[DerekL1963]

No, I haven't considered that because until this very moment I was unaware of its existence and now that I know, I still have no idea what it is. But I shall now go research this, figure out what it is, and how it might impact flotillas. Thanks for the heads-up.

No prob. Feel free to drop a PM if I can be of assistance.

[Geschosskopf]

0.25 UPDATE: MJ's Porkchop Plot

In 0.25, MJ added a new feature: "Advanaced Transfer to Another Planet" (ATTAP). This is a real game-changer, making flotilla departures MUCH less of a hassle. In fact, it takes so much of the stress out of flying a flotilla that there's no excuse not to do them now .

ATTAP uses the same "porkchop plot" as shown by Allex Moon's Launch Window Planner. Not only that, it uses ballistic (non-Homman) transfers taking the target's inclination into account, so obviates the need for a mid-course plane-change burn, at least when you're flying only 1 ship. If you've got a flotilla, for reasons discussed below you'll still need a mid-course correction for each ship but it won't be much, just a slight tweak instead of a major burn because you're already nearly in the same plane as the target after the departure burn.

So how does this have such a big impact on flotillas? Because it allows spacing out the departure burns so they don't overlap, meaning you don't have multiple KAC alarms popping up during your burns, and then all the ships leave Kerbin's SOI spaced out as well. Because the departure burns don't overlap, you don't have to worry about initially launching the flotilla ships into different orbits and spacing them out within orbits. The purpose for the care in initial launching was to make it easier to find and select the next ship in the flotilla to burn when they were all leaving essentially simultaneously. But if you space the departure burns out a few hours apart using ATTAP, then you can burn each ship in the order shown on KAC without needing to select, visually using the map view, the one best positioned to burn next.

Another handy feature of ATTAP is that you're no longer a slave to the tyrrany of clockwork transfer windows. You can go anywhere at any time, provided you're willing to spend extra delta-V for a non-optimum departure time, and/or able to cope with non-standard times of flight (faster or often much slower). All this impacts the design of the design of the flotilla as a whole (as in the overall mission plan) and the design of each ship in it (more or less delta-V, life support supplies, etc.). So before you can design the flotilla, you need to see what your options are for departure date, pick the one you like, and build to that one. This means doing some recon and tinkering as the 1st step.

Before you can do that, however, you need to understand how ATTAP works if you've never used it before. First off, you select a ship in orbit, then go to the map and pick the target planet. Then open MJ's Maneuver Planner and select ATTAP (1st function on the new drop-down list). On this screen select "porkchop" (may have to do this twice). Then the porkchop plot (it looks like a spectrum as seen during an acid trip) will appear in the MJ window. The horizontal axis is the time from the present (left end) to about 1 year in the future (right end), so the further to the right you go, the longer in the future will be your departure date. The vertical axis is the time of flight: lower means a shorter, faster trip, higher means a longer, slower trip. The colors in the field refer to the delta-V required. Red is the highest, then on through the spectrum down to blue, which is the lowest. So, to minimize delta-V, you want to pick a spot in the deepest, darkest blue you can find. To minimize time of flight, you want to pick a point as close to the bottom as you can. To leave as soon as possible, you need a point close to the left edge.

So that's basically all there is to it. As you mouse over the display, text below it will show your departure date, time of flight, and delta-v required. This enables you to see all your options. When you find a combination of delta-V, departure date, and time of flight you like, you click on that spot on the display, then select "Create Node", and there you are.

NOTE, however, that because the display is very small and initially displays the entire year in the future, its scale is very small. So small, in fact, that small blue "sweet spots" might not be visible. Fortunately, you can zoom in with the mouse wheel, which might reveal such hidden treasures. And the whole display has a reset button in the lower right corner so you can start over any time you want. So be sure to zoom in and take a good look so you really know what your options are.

So, now you're ready to give this a go with flotillas. That works like this:

1. Departure Date Recon

First, you need a ship in LKO. It needs no fuel or engine, just as long as it's got a functional MJ on it, so a previously launched probe will work fine, as long as it's in an orbit approximately like what you want to leave from. Select this ship, go to the map, select the planet you want to send a flotilla to, and bring up ATTAP in the MJ Manuever Planner (ATTAP is the 1st thing on the drop-down list of funtions). Select the Porkchop Plot option and start reviewing your departure/time of flight/delta-V options as described above. This can be a bit tricky, however, so you need to do 1 more thing before making your decision.

That thing is to click on the selected spot on the display, then actually create a node there. Once you have the node, zoom out and look at the trajectory this will give you. What you're looking for is the angle between your ship's path and the target planet's orbit when they intersect. The greater the angle between ship path and planet orbit, the more delta-V it requires to capture at the planet, while the more parallel the ship is to the planet's orbit, the less delta-V you need to capture. Now, if the target planet has an atmosphere you can aerocapture with, this doesn't matter (unless you have Deadly Reentry), but it becomes a big deal at airless planets, especially if they're small (Moho, I'm talking to you). So don't be fooled by a lower-than-expected departure burn delta-V from Kerbin. The amount of delta-V needed to get anywhere (including capture) for a given departure date is roughly the same no matter how you slice it, so anything you save on the departure burn will have to be paid for during capture (unless you can aerobrake). So, be sure to keep both ends of the trip in mind because this will affect the design of your transfer stages.

Anyway, you'll eventually find something you're happy with. Write down the departure date, time of flight, departure delta-V, etc. Also note the position of this point on the overall plot display so you can find it again when doing the real flotilla. This is especially true if you had to zoom way in to find a blue sweetspot. Now you're ready to finalize the plans for the overall mission and design the flotilla ships both for the mission and the chosen departure date. So get that done, and then you can start flying the flotilla.

2. Initial Launches

Launch each ship whenever you want to whatever orbit you want. You should aim as low as possible to maximize Oberth on the departure burn, keeping in mind that the longer the departure burn, the more altitude you need. This is because if the burn is long enough, the ship will be aiming below the horizon at the start of the burn, which can put it into the atmosphere. Burn time is a function of the TWR of the transfer stage, which is a design issue, and the delta-V needed to reach the target, which you decided on in the recon stage. In general, you want a TWR of at least 0.75 on the departure stage to avoid as much of this problem as possible and to keep the burn times short enough to not be a total buzzkill for you. You won't need to worry about overlapping burns, but there's still the amount of your real time to consider.

3. Plotting Departure Burns

When the 1st ship of the flotilla reaches orbit, go ahead and set up its departure burn using ATTAP and the departure date you chose above. Then create a KAC manuever alarm for that burn about 5 minutes prior, so the KAC list will show the time to its departure. When plotting the 2nd ship's departure, move the selected point left or right within the same blue spot on the ATTAP display to give it a departure time at least 1 hour different from the 1st ship. Usually, you'll have 1-2 days (24-hr days) of leeway on either side of the 1st ship to fill in with the other ships, within which the delta-V of the burn with only change by 10 or less, usually 5 or less. IOW, no biggie.

If your burn times are reasonably short (5-6 minutes or so), then you'll start burning 2-3 minutes before the node, so setting the alarm for the burn only 5 minutes ahead is all you need. The important thing here is to eliminate flotilla hassle by spacing the departures out by at least 1 hour. This utterly prevents overlapping and having multiple alarms popping up at once.

4. Doing the Departure Burns

So now you've got the whole flotilla set up, each ship with its burn set in KAC, and all burns at least 1 hour apart, maybe even spread over a couple of days for the whole flotilla. Now it's just a matter of burning each ship as its time comes up. So just warp ahead until the 1st ship's alarm goes off and jump to it, restoring maneuver node. At this point you should have about 2 minutes before the burn starts, although you can't see this because jumping between ships kills the burn-time calculation. So you still have to blip the throttle, same as in the old way. Rotate the ship to point at its node (which will be nearly prograde) and blip the throttle slightly until the burn time displays. Then execute the burn, either manually or via MJ.

And now you start appreciating how much easier ATTAP makes things. Just keep following this ship out from Kerbin, warping as fast as increasing altitude allows, until the alarm for the 2nd ship goes off. Jump to it, blip it, burn it, and then follow it out until the 3rd alarm goes off. Repeat until all ships have burned. And that's it. No hassle at all with multiple alarms, finding the best ship to burn, recreating maneuver nodes, etc. .

5. Leaving Kerbin's SOI

Because the departure burns were spaced out so much, the ships will also leave Kerbin's SOI spaced out about the same amount. So when the 1st ship's SOI-change alarm goes off (remember, we're still setting those to be created automatically 5 minutes prior), jump to it and ease it across the boundary. At this point, because you've got plenty of time until the next ship's SOI alarm, go ahead and uses MJ's Maneuver Planner's Fine Tune Closest Approach to Target function to create its mid-course tweak. This will always be necessary with a flotilla. While ATTAP will always give you an interecept when initially plotted, since then some days or weeks have passed, you blipped the throttles, and you crossed an SOI, so might not actually have an intercept now. But now biggie, you won't be far off target so the correction burn won't be major.

Sometimes you spaced the departure burns out so much that one ship might leave Kerbin's SOI before the next even burns. No biggie, just take things as they happen on KAC. About the only way to get simultaneous alarms with ATTAP is if you somehow get an SOI alarm at the same time as a departure alarm. But so far I haven't had this happen so I wouldn't worry about it too much.

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Anyway, that's about all there is to using ATTAP for flotillas. It's MUCH MUCH less hassle to get the show on the road using it, thanks to the ability to space out the departure burns.

Note, however, that this also increases the spacing between arrivals at the target. This is actually beneficial at Eve, where doing things the old way could get hectic with nearly simultaneous arrivals, but at other places will mean that some ships might have to wait longer to get started with their jobs while waiting on another ship to arrive. But even there, it seems that the time difference isn't that much anyway. The ATTAP ballistic trajectories tend to result in tighter flotillas than Hohmann transfers, so the additional arrival spread isn't a problem.

[Pretorian28715]

@Geschosskopf any chance of having this updated after 1.3 arrives?

This is a very useful guide, as I really was not sure how I was going to organise inter-planetary missions once I got to them. This has given me a very good picture of what and how to do them, thank you, also having any additional information the update (of this thread) might add would be helpful.

Considering what I know about KSP since the last update (adding MJ's ATTAP), I'm not aware of any changes that would affect this too much? However at only 450Hrs played I think I have a long way to go yet.

Either way thanks for this v. helpful guide.

[DerekL1963]

12 hours ago, Pretorian28715 said:

any chance of having this updated after 1.3 arrives?

There's no particular need to, none of the game changes affect the concepts here.