Am I trying to get into Munar orbit incorrectly?

[jmr106]

I understand the general principle of getting into Kerbin orbit and have no problem with that. Generally, I shoot for (what is probably overkill) about 2,500m/s @100,000m to what usually ends up as about 300,000m after the upward momentum has subsided. Then I perform a burn at the apoapsis to make my orbit proper and circular around Kerbin.

Then I initiate another node to create a prograde burn that becomes a larger, oblong orbit that is much farther out than the Kerbin orbit. Then I do another burn to make the oblong orbit circular.

Is there a more direct path to the Mun other than this method of oblong and then circular orbits using burns to try to line up my circular orbit with the exact orbit of the Mun? I'm still learning and so far I don't know how to use the other symbols yet (apart from the prograde and retrograde orbit bar when creating a new future burn). Theoretically, using this method of circular orbit turned oblong orbit, turned circular orbit again...is this the proper way to make it to any of the planets? Or is there a more direct route and is my way using up way too much fuel? It's a bit hard to describe, so I have included an image that consists of 5 images of different burn stages. It ends with the start of the oblong orbit in trying to branch out from Kerbin orbit.

I'm basically just trying to make sure that this circular orbit and then the oblong orbit (until the 3rd burn to make it circular) are the right way that I should be using this?

Edited September 15, 2013 by jmr106

[BrokeAsAJoke]

ok, so you have mastered the difficult part of achieving orbit. there are two ways of getting to the mun 1. watch kerban as you orbit around it.. when you see the mun rising over the horizon then initiate a prograde burn, switch to the map view and wait for your encounter with the mun. 2. spin the map view until the mun is at the 12 o'clock position. then create a maneuver node at 5 o'clock position and add prograde (this is essentially the first method except youre using a maneuver node). Continue to add prograde juice until your orbit touches the muns orbit. If you don't get an encounter with the mun... no worries. just grab the center of the node and slide it around on your orbit until you get one! once you get an encounter just warp to the Pe you will get from the mun and burn retrograde until you get a capture orbit. I hope this helped!

[blizzy78]

Perhaps you might want to try out my in-game moon travel tutorial I've just released yesterday. (see signature)

[Scarecrow88]

I don't usually make my orbit around Kerbin quite so high, but carry on doing whatever works for you in that respect. As to getting to the Mun, I did a few screen shots of one of my trips that I have added a few comments to. It's not a tutorial as such, but may help with some information or ideas that you are not familiar with.

[MatzahMan]

Another idea might be to get into a 70-80,000m orbit instead of a 100,000m or 300,000m. I don't know if it saves any fuel, but its a lot easier to get to, and since its only a temporary orbit, you don't need to make it all nice and pretty and circularized.

I know I'm not answering your main question, but it might be an idea you want to consider. Hope this helps!

[Kasuha]

I understand the general principle of getting into Kerbin orbit and have no problem with that. Generally, I shoot for (what is probably overkill) about 2,500m/s @100,000m to what usually ends up as about 300,000m after the upward momentum has subsided. Then I perform a burn at the apoapsis to make my orbit proper and circular around Kerbin.

It is unnecessarily high, about 100 km is perfectly fine. But you can get there later.

Then I initiate another node to create a prograde burn that becomes a larger, oblong orbit that is much farther out than the Kerbin orbit. Then I do another burn to make the oblong orbit circular.

Try this: make the oblong orbit end above the Mun's orbit. Then move the node around your orbit till you see something color change and Mun "shadow" at where it intersects the Mun orbit - that's a Mun encounter. At that point you can play with the maneuver parameters to decrease needed velocity change while still getting the encounter.

Then execute the maneuver and make sure you get the same color change on your real trajectory. Then time warp till you get to that area and in there burn retrograde (best at periapsis but if you don't see one then just anywhere) to get to Mun orbit.

Of course even more direct approach is to time your start correctly and get on trajectory for Mun encounter using just single burn without getting on any orbit. But it's not necessary to try that too soon.

[karolus10]

I would like to suggest You using free return trajectory to get to the mun - it appear to be more complicated, but in fact it made entire mission much easier and smoother.

# First, try go into 80km parking orbit, going anywhere higher is unnecessary .

# Click on mun in map view to set is as target.

# Create maneuver node on ascending/descending node (green markers) on our orbit to correct our inclination difference to zero.

# Create maneuver node behind our spacecraft and add ~875 m/s in pro-grade axis (forward/back), we will use only pro-grade axis.

# Slide node on orbit to find proper orbit, we need to encounter mun Head-On (unlike normal transfer chasing mun from behind) with smallest Mun periapsis as possible.

# Click on purple mun Pe marker to lock it's value visible.

# Made fine correction to maneuver node prograde/retrograde axis until Mun peripasis is set at 50km, You can get lower, but you risk hitting the Mun due SOI change error.

# Perform injection burn.

# Create and execute course correction node half way to the mun (or place where green marker crossing inclination axis on picture above) and made necessary correction (50km Mun peripasis).

# After reaching Mun SOI made correction burn to change mun periapsis to 20 kilometers or you can made first braking burn 5 minutes before Mun periapsis, lowering Pe to 20km.

# Perform braking burn at mun periapsis for Mun orbit insertion .

Edited September 15, 2013 by karolus10

[DisarmingBaton5]

WARNING: Text-based tutorial ahead!

Notes:

This tutorial goes all the way through landing.

This tutorial assumes you have an appropriate amount of dV in your vehicle and an appropriate TWR in your lander.

If you can reliably get to ~100km orbit, skip to step 8.

Remember to keep quicksaving! Save early, save often.

1. Launch straight up to ~5km, full throttle. (No Mainsails directly underneath orange tanks!)

2. ~5km up, pitch over to 5* East.

3. 10-15km up, pitch over to 45* East.

4. Enter map view.

5. When apoapsis = 100km, cut engine. ("x" key)

6. ~5s before apoapsis, burn 5* up from horizon and wait until periapsis > 70km.

7. YAY! Orbit!

IMPORTANT NOTE: In map view, click the small white tab at the bottom of the screen. This will bring up the navball and allow you to navigate in the map screen.

8. *see note above first* Look at the map view. Timewarp until the center of Kerbin is directly between the Mun and you.

9. Go to the ship view. Aim prograde.

10. When the Mun appears above the Eastern horizon, (the one you are travelling towards) burn prograde.

11. Go to map view. wait until you have an encounter with the Mun. (should look like a crazy, colorful interruption of your trajectory)

12. Wait. A long, long time. (just kidding, timewarp.)

ANOTHER IMPORTANT NOTE: ENSURE YOUR MUNAR PERIAPSIS IS VISIBLE. OTHERWISE YOU WILL DIE.

YET ANOTHER NB: DO NOT TIMEWARP PAST THE MUN.

13. At Mun Periapsis, burn retrograde until your orbit is ~circular. Keep it under ~50km, for the sake of ease later. (landing is easier this way)

14. Choose a *rough* landing site. By landing site I mean sunlit side, with a view of Kerbin if you want it. Do not choose any specific craters until you have landed many times.

15. When you are on the exact opposite side of that of your intended landing site, burn retrograde.

16. Burn until your periapsis is 3-5km.

17. ~20s before periapsis, burn retrograde. Follow that retrograde marker, but stop burning if you get to 0m/s.

18. Landing legs should be down by now, if they are not, put them down.

19. Burn at the retrograde horizon (the one you came from) until you are in vertical descent. (retrograde marker should be straight up, prograde straight down)

20. Vertical descent. Do not exceed 20m/s.

21. Once you are under ~1km, do not exceed 10m/s.

22. Start looking for your shadow. This is your best indicator of altitude once you are close to the surface.

23. Landing itself. This is the most difficult part, because you are doing lots of things at once. I'll split it up into parts.

23a. Do not exceed 5m/s.

23b. It's really tempting to look at your lander when you are turning, but don't. Remember, execute all maneuvers with the navball.

23c. Stay between the retrograde marker and straight up. Ideally they are perfectly aligned, but at this low speed, they never are.

23d. Look at that shadow! Ignore the altitude indicator at the top of the screen.

23e. Don't pitch over too much. You'll regret it.

If you have accomplished all of the above simultaneously and for the last hundred(s) of meters, you have (hopefully) safely landed! Don't worry if it takes you more than one try, or more than 100. My first landing was a timewarp into the surface! Hope this helps.

[Epthelyn]

I understand the general principle of getting into Kerbin orbit and have no problem with that. Generally, I shoot for (what is probably overkill) about 2,500m/s @100,000m to what usually ends up as about 300,000m after the upward momentum has subsided. Then I perform a burn at the apoapsis to make my orbit proper and circular around Kerbin.

If you're doing that, you're going about it the 'hard' way. Use the map view to view the orbit as you burn rather than reaching a pre-defined velocity at which you know as a working orbit. A perfect 100km x 100km orbit would actually be 2245m/s.

As for what you're doing with the orbit extensions then circularising and repeating that process, well, it's most of the way there to how you should be doing it. All you need to do is extend the orbit right up to or beyond the Mun's orbit in one burn rather than multiple burns. Burn prograde when the Mun rises over the horizon on Kerbin and that single burn will give you a Munar encounter.

[iBeej]

Here is the simple easy constant I have learned when it comes to intersect any orbiting celestial body relative to a fixed position. Basically, anything orbiting your current position:

45 degrees.

Launching from Kerbin? You can intersect the Mun (or Minmus) without an orbit, simply going straight up, if you launch when your target is -45 degrees. Example, in map mode if you launched straight up, your position on the ground (relative to Kerbin) would be 12 o clock, and the Mun would be at the 2 o'clock position. What if you're orbiting Kerbin? Then the Mun should be in the same 45 degree position relative to your PROGRADE. (Your current direction).

To make this easier, don't even bother eyeballing it like a clock. Instead, simply ensure your "purple prograde target" on the nav ball is on the 45 degree mark if launching.... Or if in an orbit, simply 45 degrees FROM your prograde on the nav ball. (Obviously you need to be 45 degrees AHEAD of your target prograde, or else you miss it.)

This sounds complicated, but it's not. At 45 degrees you will hit it every time. Whether it is the Mun or Minmus. Or whether it's Laythe from a Jool orbit.

45 degrees.

Also don't forget inclination. So you should have enough Delta V to accommodate adjustments for approach velocity and inclination.

And obviously.. The 45 degree magic number does NOT apply for transfer between two seperate orbiting bodies. (Planet to Planet or Moon to Moon). That involves Phase Angles, and that's an entirely different ball game.

For me, the answer to the universe isn't 42. It's 45.

Either way, close enough.

[karolus10]

Also good rule of thumb for starters are burning pro-grade from 80km orbit, when Mun start rising from Kerbin horizon and burn until you get encounter .

[Kulebron]

I think Kasuha pretty much answered your question (that you need to drag the maneuver node around to find the perfect moment for injection).

According to Oberth effect, the lower your parking orbit is, the more delta-V you get on injection. Injecting from a higher orbit makes you use more fuel in total. When passing near Mun, lower periapsis also saves some fuel. I prefer the figure 8 orbit (Apollo style, free-return trajectory), because it saves delta-V on lunar orbit insertion.