RSS RP-0 RO Russia to Moon Launch questions

[gsamelon]

I am having trouble getting a moon intersect from Russia (above the inclination of the moon). My rocket can't park in orbit, it needs to be a strait shot. What is the best way to do this? I have heard to go for a polar launch but not sure how to set up this up.

[NathanKell]

You will need to launch during a launch window. See this thread for a planner, or at the end of the OP a spreadsheet to do just this case.

http://forum.kerbalspaceprogram.com/index.php?/topic/99228-win-flyby-finder-for-real-solar-system-mod-v082-rss1041-for-ksp105/

[Teilnehmer]

As far as I understand, one cannot launch directly into the plane of the Moon from Baikonur. It is necessary to make a dogleg maneuver, i.e. launch towards the equator (?) and then change the plane during the launch while the speed is still not very high.

Edited February 9, 2016 by Teilnehmer

[NathanKell]

No, you just need to launch during a time your AN or DN matches the Moon's AN or DN.

[Guest]

3 hours ago, NathanKell said:

No, you just need to launch during a time your AN or DN matches the Moon's AN or DN.

This exactly.  Launch from Baikonur or Plesetsk or wherever you're launching from when the site lines up under the Moon's orbit.  That is, center your view on Earth, zoom out until you can see the Moon's orbit, pan the view until the Moon's orbit is a line, and timewarp until the site is under that line or a bit in front of it.  If using Engineer, set the Moon as your target and use the relative inclination information from the rendezvous window to help guide your launch.  You'll probably still need to adjust your inclination in orbit but the maneuver will be relatively cheap.

Basically you shift all the extra delta-V requirements to your lifter, so pack a few hundred more m/s on the lifter or lighten the load.  Same procedure can be used for transfers to pretty much everywhere else from pretty much everywhere else.

[Teilnehmer]

On 07.02.2016 at 3:51 AM, regex said:

That is, center your view on Earth, zoom out until you can see the Moon's orbit, pan the view until the Moon's orbit is a line, and timewarp until the site is under that line or a bit in front of it.

Hm…

Earth’s axial tilt is 23.4° to the ecliptic. The inclination of the Moon is 5.1° to the ecliptic. Doesn’t this mean that only points inside the 28.5°S—28.5°N belt can appear under that line?

[Guest]

28 minutes ago, Teilnehmer said:

Hm…

Earth’s axial tilt is 23.4° to the ecliptic. The inclination of the Moon is 5.1° to the ecliptic. Doesn’t this mean that only points inside the 28.5°S—28.5°N belt can appear under that line?

Then launch when you're closest to it and pull a dogleg in flight.

[Teilnehmer]

2 hours ago, regex said:

Then launch when you're closest to it and pull a dogleg in flight.

What exactly is such a dogleg?

It’s 2000 km from Baikonur to 28°N (4000 km from Plesetsk), it’s several minutes of flight. It’s an interesting problem to find the optimal heading, altitude, speed etc of the flight before the turn. How much Δv does it cost?

Edited February 9, 2016 by Teilnehmer

[Geher]

You don't need to do a plane change. Just do the trans-lunar injection burn at the right time at the ascending or descending node.

So when you fly anytime into orbit, the longest time you would've to wait until the trans-lunar injection burn would actually get you to the moon is about half a month. If you're really good and wait for your launch date until the moon is at the right place, then you can do the trans-lunar injection burn in the first orbit.

This way you can theoretically fly to the moon even from a polar orbit.

[Guest]

8 hours ago, Teilnehmer said:

What exactly is such a dogleg?

It’s 2000 km from Baikonur to 28°N (4000 km from Plesetsk), it’s several minutes of flight. It’s an interesting problem to find the optimal heading, altitude, speed etc of the flight before the turn. How much Δv does it cost?

Yeah, I was clearly wrong, hadn't thought the problem through.  You can minimize the inclination change by launching as close to the Moon's orbit as possible and then transfering from AN/DN, but that's about it from launch.

[Alchemist]

The way they they sent Luna 1-3 probes was exactly like this - single burn to lunar intercept.

Launch window should be when you are as close to the orbit plane as you can be, but that's not all.
First of all you'll need to find the proper azimuth for launch. If you just launch parallel to Moon's orbital plane (which is straight east at this point), you'll cross it about halfway there. To get the plane intersection at apoapsis you'll have to launch slightly tho the north. Can tell the exact azimuth (try something around 70-75 degrees for the start), since it's also dependent on the kind of trajectory your craft really puts you in (you don't have to make it fully horizontal at engine cutoff. In fact it must be going slightly upwards, probably like 20 degrees above horizon).

Anyway, you actually have 3 main variables at this point: time of the day (your starting position relative to Moon's ascending node, but you'll most likely have to keep it around 90 degrees from the nodes), launch azimuth and angle relative to the horizon on engine cutoff. Try some simulations to find the solution that makes your craft cross the orbit of the Moon. That will be your transfer trajectory. And note the point the orbits intersect and transfer duration.

Then you need to find the day of the month when the Moon is slightly before the orbit intersect point (so that it ends there the same time as your craft). You'll need to launch that day.

[gsamelon]

Thanks for all the help folks.  Completed my Luna re-creations missions!