Advanced Question Direct Ascent to the Moon

[PaulG]

How do I do a direct ascent to the moon from earth? I want to take off from earth and head directly to the moon without entering a LEO.

Can IMFD do it? If so, how?

Thanks,
Paul

 

[mbartley]

I've done it before by launching in a guessed approximate time and direction, then when above enough of the atmosphere, quickly going into IMFD's off-plane target intercept and setting up a solution.

It's not efficient, but it usually works, though I don't know how to know when and which direction to launch, beyond a wild guess anyways. Last time I tried it, I launched when the moon was high in the eastern sky and then flew towards it. I ended up ascending nearly straight up for a long time, probably with tons of gravity loss.

 

[PaulG]

I can see how it can be quite a dynamic situation. It doesn't seem like IMFD can do it alone. Is there a combination of MFDs that can help plan such a thing? Or, is it best by experimentation alone?

 

[the.punk]

You can do it with IMFD alone.
1. when you stand on the ground
Set up Imfd course programm target intercept.
2.Target as moon
3. set the time to eject to 0
4.time warp until you reach an good launch window.
(Maybe you must tweak the time for arrival)
5.When you have an good launch winow switch to BV mode and take of in the right direction.
burn until dv reached 0

Thats i you are on the way to moon.

 

[PaulG]

Hmm....I did that, but I believe when I did that, the launch window (for inclination) was on, but the moon was on the other side of the earth, so I had to rotate my (becoming hyperbolic) orbit. I didn't have enough fuel.

So, a better question, is it possible to do in the DGIV with the fuel level designed for the moon or do I need a lot more fuel than a typical LEO method?

 

[the.punk]

When your orbit becomes hyperbolic you must incrase your time for arrival.

 

[PaulG]

Ok, but shouldn't it be possible to set an arrival date and meet it by applying to correct dV? It seems as though going to the moon via direct ascent isn't much different than going to the ISS.

Am I correct in saying that I need to pick a time where the dInc is at a minimum and the moon is nearly above me?

 

[flytandem]

To make it easier as a first try I started at Habana so I could launch 090 and be fairly in plane with the moon. Then it was a matter of the window. There is one window a day to launch in plane with the moon so it came down to which day.
To approximate I first did a test run with the moon on the exact opposite side of my position as shown in Map when I launched and just went prograde to see how much the moon ended up either ahead or behind me at the point I crossed the moons orbit. Turned out that I was behind by about 22 degrees. So I simply restarted the flight but chose the day where the moon was either at or before that location when I reached my daily window. BTW, the 22 degrees is about 3/4 of one grid line in MAP. Using the stock Deltaglider scenario, Habana Spaceport, the launch time was Friday Mar 16 at 00:44 .

Launching like this I simply stayed in plane with the moon during ascent and watched TransX show my closest approach to the moon as my Ap climbed. The Cl App dropped rapidly and I cut off as it showed a nice close Pe. It first showed an arrival with an inclination at the moon of about 3 or 4 degrees then a little bit more prograde burn with forward LIN and it dropped the Pe through the moon and out the other side for a 170 or so inclination.

 

[PaulG]

So, I tried something similar out, and it worked VERY well. I launched from KSC at minim RInc. Using IMFD in the target intercept mode, I set the ejection time to 0 and the arrival time to 3 days (256k sec). Then, I varied the date using the editor to find a date where the ejection angle was small to achieve as best a tangential ejection as possible, while maintaining a direct ascent (no LEO).

It worked. But now, here is my question. I had to vary the date in the editor and set the ejection time to 0 in order to prevent IMFD from counting down and giving all sorts of wierd predictions that jumped around. It would have been better just to use IMFD to adjust the date I wanted to eject, but the display kept jumping. The workaround with the date editor is fine, but, why does IMFD have such a hard time with that, and is there a fix?

 

[PaulG]

So, after fooling around a bit, it seems as though the only way to "calculate" is to use the date editor. Is there a way around this?

 

[thammond]

I'm not proficient enough in IMFD to help. There is a addon, Luna Program, that uses a direct ascent method to reach the moon. It uses an autopilot so I'm not sure what "tools" were used to figure out the flight profile. I also have found a reference to a movie that was made showing a direct ascent to the moon in a DG, but the link to the movie is down.

I have been intrested in trying a direct ascent flight to the moon since running the Luna addon.