Help with sending an an armada

[Mr.Rocket]

So, I am currently in the process of building a Duna base/ space station. The problem is, Duna windows don't come that often, about once every 180 days, so i'm trying to send more than one ship at a time. In fact this time, i am sending four. I have some questions on how to do this.

1. Does it matter what order i "send" the ships in? biggest to smallest, vice versa, manned first then unmanned, most thrust?

2. How do i know which one will arrive first?

3. How do i send an armada in general, i want to do the Duna burn for one, then move on to the next?

4. Any other tips?

I am hoping some people who have sent multiple ships could help me out, or who have done this before. I have the Kerbal Alarm Clock Mod to make sure i have the right transfer window. Thanks for your help in advance

Edited January 1, 2014 by Mr.Rocket

[KvickFlygarn87]

1. Any way you want, but you might wanna fit the ship with the tightest budget in the cheapest window.

2. By hovering the mouse over the encounter.

3. Yes

4. Nope.

[el_coyoto]

So, I am currently in the process of building a Duna base/ space station. The problem is, Duna windows don't come that often, about once every 180 days, so i'm trying to send more than one ship at a time. In fact this time, i am sending four. I have some questions on how to do this.

I am hoping some people who have sent multiple ships could help me out, or who have done this before. I have the Kerbal Alarm Clock Mod to make sure i have the right transfer window. Thanks for your help in advance

I've just sent a few armadas to Duna before and in fact have just returned from the game where I've sent 2 probes to Moho (one for a flyby + experiments return, the other for a landing), so I thought I'd share my tips and tricks on the subject, before going to bed and further develop my robotic invasion of Moho...

1. Does it matter what order i "send" the ships in? biggest to smallest, vice versa, manned first then unmanned, most thrust?

You can do as you like, but if you mean the order in which they eject from Kerbin, well, not really : the slightest difference in the burn would change the arrival time.

But you can tweak your transfer orbit so that your scout rover arrives a few weeks in advance with a faster trajectory for example...

2. How do i know which one will arrive first?

As KvickFlygarn87 mentioned, you can hover the maneuver node to read the arrival time of each ship. Even better, Kerbal Alarm Clock lets you add a clock when the sips arrives at its destination.

3. How do i send an armada in general, i want to do the Duna burn for one, then move on to the next?

Yup, that's it. Depending on how you closely packed you want your armada, you can setup a "bead of pearls in orbit" of ships and then launch them in turn with ejection angles that are very close to the optimal one : plan trajectory, burn one ship, switch to the next one, mess around with maneuver node, burn, rinse, repeat. Of course, the longer the ejection burn, the more you have to space your ships.

But this can quickly become a task switching fest as you add ships, especially as they will also tend to arrive at the same time at their target...

Personally, I forget about pure efficiency, and don't mind a few tenths of degrees wrong on my ejection angle and space apart launches by at least one orbit and more commonly 6 or 8 hours just to be cool.

The loss of delta v is not so bad, and it leaves much more time to adjust orbits and aerobraking trajectories without sweating too much.

4. Any other tips?

Well, if you go for closely packed armada during your mass invasion of Duna, here is a quick and dirty trick I often use is to "copy" one ship trajectory by setting it as a target and zeroing your relative velocity.

This works well with dense armadas, but also on ships launched with fairly different trajectories : my Moho dual probe launches had been spaced by ~10 hours and each disrupted differently by the Mun. A few days after the launch, I found a (big) correction for my first probe that saved at least a net 1500 m/s in plane change at the cost of an inclined Moho orbit. I applied the same correction the second probe by using the first as a target and got more or less the same intercept for more or less the same delta v savings...

Hope this helped.

Cheers and happy new year!

Edited January 1, 2014 by el_coyoto

[celem]

I generally sort out arrival order mid-course. They depart based on dV spare, the guys with tight mission profiles get the launches closest to the optimal window. Once in flight, tiny burns will shift arrival time considerably.

When it comes to armadas I tend to treat them like el-coyote above. I generally have the whole fleet in parking orbit and chuck them outwards as each ship approaches ejection angle. Low TWR interplanet stages means i'll often let a ship do another lap so that I can start a burn properly before the node (i like to split my burns 50/50 across T+0).

I would add that you should be wary of spacing the arrivals too tightly, especially with Duna as destination (im assuming you will aerobrake). You need enough time for each vessel to complete its brake before the next one starts, since only the vessel you are 'riding' will actually brake (the rest will rip through on rails and escape).

[Mr.Rocket]

Thanks guys. Il'll mark this one as answered. I think I'll send the manned one on the fastest path since i don't need a scout rover, it's already there. Although i don't plan on aerobraking with Duna's atmosphere, i only do that at jool and i have enough delta-v. Happy New Year

[Zzabur]

I tried to build some kind of Duna's base in 0.22. Kerbal alarm Clock definitely help to check which vessels is near a maneuver node or change SOI.

[JumpsterG]

If you're interested in figuring out good departure dates, travel times, and sub-optimal (but still within dV budget) launch windows, the charts plotted with this tool are amazing:

http://alexmoon.github.io/ksp/