rescuing two kerbals in the same launch

[putnamto]

ok, so i have the dude on the surface, and the dude in orbit i want to rescue them both in the same launch, i have my vehicle figured out, but i dont know how to go about my flight plan.

ive had a couple ideas,
set up a polar orbit of mun, intersept dude in orbit, land, then pick up dude on surface. this would probably take the least bit of dv
match orbits with the dude in space, pick him up, then change inclination to polar then land and pick up the other dude. this would probably take more.
land pick up the dude on the surface, make orbit around mun, change inclination, pick up other dude. i think this one would take the most dv.

am i correct in these three options? any suggestions?

[Human Person]

8 minutes ago, putnamto said:

land pick up the dude on the surface, make orbit around mun, change inclination, pick up other dude. i think this one would take the most dv.

try to make orbit around the mun with the right inclination with respect to dude in orbit.

All these inclination changes you're talking about that's where you can save on delta v. minimize these and you have the perfect plan.

Edited May 3, 2018 by Human Person

[putnamto]

alright, so land at the pole, pick up dude, then launch north in time with dude in orbit, intercept dude, fly home.

in my head this means i would be setting up a perpendicular intercept and not a parralel one, is this possible?

Edited May 3, 2018 by putnamto

[4x4cheesecake]

Well, there is a option you haven't considered yet:

one launch with two seperate crew modules with their own tanks/engines and splitting up half the way to the mun. One vessel goes for orbit dude, the other can perform a pretty cheap correction burn to get in polar mun orbit and goes for surface dude.

Edited May 3, 2018 by 4x4cheesecake

[Zeiss Ikon]

If  you can land direct (without orbiting first) precisely enough to get the Kerbal on the surface, do that first.  Then, when you launch from the Mun, launch northeast but just make a "hop" that will barely keep you above terrain until you cross the other orbit, then make your plane change at the same time you turn your suborbital into an orbit.  From there, it's a standard rendezvous from below.

If your aren't confident you can land direct in the right spot (I wouldn't be), then get the one in orbit first.  Wait until the Mun rotates to put the Kerbal on the suface as close to the southern end of your orbit as possible, then make your deorbit with a side vector to push your landing point enough further south to reach the one on the surface.

Any time you can combine maneuvers, you save dV -- in this case, you're combining your plane change with your launch from the Mun or your deorbit, thrusting on the diagonal instead of two maneuvers at right angles to each other.  With no atmosphere, you only have to compensate for the Mun's rotation in setting your landing point from the maneuver node -- and a six day rotation doesn't move an impact point an hour out very far, so you should be able to land pretty close to the Kerbal on the surface.  Hopefully, the surface isn't too rough there...

[putnamto]

10 hours ago, 4x4cheesecake said:

Well, there is a option you haven't considered yet:

one launch with two seperate crew modules with their own tanks/engines and splitting up half the way to the mun. One vessel goes for orbit dude, the other can perform a pretty cheap correction burn to get in polar mun orbit and goes for surface dude.

i attempted this, came into munar orbit in the wrong direction, my transfer stage still had enough DV to reverse orbit and match planes with the orbital dude.

then when i went to transfer my engines wouldnt fire, turns out i had ran out of electricity and all of my solar panels are on the sides of the command pods, and my ship was stuck pointing retrograde to the sun. i skipped time forward for a very long time and i could never get any juice.

tommorow ill attempt again, this time with more panels.
this is the fixed craft, i think it looks neat, should have probably gone with stacked pods instead of a fork shape, but whatever.


it doesnt look nearly as cool as this one though. to bad it cant even make orbit, doesnt have a high enough TWR after the boosters seperate, it just kind of gets slower and slower till it falls back to kerbin.

[putnamto]

ok, so i got the dude that was in orbit, he's on his way home.

ive tried to land near the dude on the surface and i either run out of dv, or i land waaaay to far away from him.

give me some tips on pinpoint landings please.

[bewing]

Landing on a pinpoint requires extra fuel. You also have to lead your target by a fractional amount, depending on how close to the equator the target is, and the rotation rate of the CB. It also depends on whether you are coming in on a hyperbolic direct landing or whether you are already in orbit. (In your case, your target is almost at the pole, and the Mun rotates very slowly -- so don't even bother leading your target.)

If you are just about to enter the SOI and you are coming in for a direct landing -- then you just burn N/S/E/W in order to make your trajectory in map mode hit the ground where your target will be. Then do a massive suicide burn when you get there.

If you are in an orbit, then you first have to incline your orbit so that it passes over where your target will be. When you get reasonably close to your target, quickly make a mental note of which directions are N/S/E/W, and then burn retrograde. Make sure the impact point of your trajectory in map mode stays beyond your target. After you slow down a lot, adjust your trajectory normal/anti-normal to make it pass closer to being above your target. But don't trust the position of your target in map mode. You may easily be off a handful of kilometers if you trust map mode too much. So flip to flight mode. With the rocket pointed retrograde, from the orientation of your rocket, decide whether your target is to the left or right -- and whether that means N/S/E/W. Then do a little burn in that direction, go back to retrograde, and eyeball whether you are pointed right at the target. Once you appear to be right directly over your target, burn retrograde at the horizon level to cancel out all your horizontal velocity. Your retrograde marker will move to match Radial Out. Then just come straight down on your target. Doing this you will almost always end up within 500 meters. If you want to stop halfway down to the ground and do another tiny correction, you can -- but that's dangerous because your retrograde markers will be going all over the place when you stop in midair.

[putnamto]

i hope 3k dv is enough to land, get him, and get back to kerbin.

[bewing]

Yup, 600 for an inclination change, 750 to land, 650 to get back to orbit, 280 to get back to kerbin. = 2280. And you can spend the rest during Kerbin reentry.

 

[putnamto]

1 hour ago, bewing said:

Yup, 600 for an inclination change, 750 to land, 650 to get back to orbit, 280 to get back to kerbin. = 2280. And you can spend the rest during Kerbin reentry.

 

numerous failed attempts at getting close enough i got within 1.2km and had a very very VERY long walk.......in the dark.....up and over the lip of a crater........the only problem is that the ship only has 500dv left

tell me theirs still hope.
my ship is the one at the south pole.

Edited May 5, 2018 by putnamto

[bewing]

1 hour ago, putnamto said:

i got within 1.2km and had a very very VERY long walk.......in the dark.....up and over the lip of a crater........the only problem is that the ship only has 500dv left

Heh. A 1.2km walk on the Mun is nothing. Just wait until your first 20km hike.

And Kerbals don't have to walk tiny little distances like 1.2km on the Mun -- they can fly. Flying is fun. And anyway, you may need the practice, because ...

1 hour ago, putnamto said:

tell me theirs still hope.

Of course there is. 500 dV gets you almost to orbit. You go EVA and bail out. Use your jets to finish getting you into orbit around the Mun. Suddenly your new kerbal is ever so much easier to finish rescuing.

 

[putnamto]

34 minutes ago, bewing said:

Heh. A 1.2km walk on the Mun is nothing. Just wait until your first 20km hike.

And Kerbals don't have to walk tiny little distances like 1.2km on the Mun -- they can fly. Flying is fun. And anyway, you may need the practice, because ...

Of course there is. 500 dV gets you almost to orbit. You go EVA and bail out. Use your jets to finish getting you into orbit around the Mun. Suddenly your new kerbal is ever so much easier to finish rescuing.

 

i would have flown him but it was dark.
he was on the opposite side of the crater that i landed on, and i when i went to cross the crater i lost track of the ground and suddenly i had gained a crap ton of altitude, decided to come back down, didnt burn retro fast enough and he bounced and bounced....and well kept bouncing lol.

[putnamto]

success!!! i dont know if i did it right but it worked.

full throttle from the mun straight up to 5k, turn horizontal and burn all of the fuel, then jettison the pod, then bail out of the pod, use dudes rcs to thrust up and forward depending on how far from my ap and i ended up with a 10k orbit and 2.5 mono prop left in the tank, launched a rescue vessell, picked him up and came back home.

i still need to work on my landings though, for some reason no matter what i do i always land on the dark side of kerbin.

oh, and i realized that trying to fly eva while on the map screen is a very very bad idea, on the map screen everything looked nominal but my pe kept dropping, when i switch back to flight screen my dude spinning out of control and plummeting to the surface at an alarming rate.

[bewing]

It's possible to fly it a little more efficiently than you did. But you only used half your RCS and it worked.

So you get full points for success; no question about that.