TLI Burns from ISS inc.

[pete.dakota]

Howdy. Today I decided that I would try doing a KSC-ISS-Brighton Beach-KSC using IMFD. Big fun, right? Sadly, I can't work out for the life of me how to plan an efficient off plane TLI burn from the ISS's inclination.

I've placed a DGIV at the ISS and have been tinkering around with IMFD. Automatically, IMFD gives me an 880s main engine burn, so I'm guessing that IMFD is also trying to make a plane change during the burn, and not targeting the Moon off-plane.

I know that these off-plane lunar transfers are possible. I just need some help learning how to use IMFD to make them.

Thanks for any replies.

 

[agentgonzo]

An off-plane transfer from ISS to the moon is VERY inefficient. The best thing to do in that situation is to do a burn to raise your Apogee a lot (to lunar distance or part way there, but definitely above 100,000km or so). Then, when you reach apogee, do your plane change burn there. It's much more efficient.

 

[pete.dakota]

An off-plane transfer from ISS to the moon is VERY inefficient. The best thing to do in that situation is to do a burn to raise your Apogee a lot (to lunar distance or part way there, but definitely above 100,000km or so). Then, when you reach apogee, do your plane change burn there. It's much more efficient.

Is this what the Russian moon probes did? It's an interesting idea, though very hard to plan I would imagine. Also surely this would mean having to come back around to the Earth at perigee after the plane change and then heading off to the moon, doubling the transfer time.

 

[Urwumpe]

An off-plane transfer from ISS to the moon is VERY inefficient. The best thing to do in that situation is to do a burn to raise your Apogee a lot (to lunar distance or part way there, but definitely above 100,000km or so). Then, when you reach apogee, do your plane change burn there. It's much more efficient.

That is a slightly higher dV as just arriving at the moon with a inclination. You will have a higher relative speed to the moon when you enter its SOI, but finally, you will need less for capture as the excessive speed does not increase the perilune velocity as strong as it is outside the SOI.

I can't understand why people are so nervous about plane alignments. if you would do such transfers without the use of an advanced MFD, I could understand you want to use simpler math, but with IMFD or TransX, this makes no sense.

Remember which factors increase and decrease the offplane dV of your maneuvers, but plan your trajectory according to it, instead of making extra plane alignments.

 

[jarmonik]

Proper timing (launch window) is very important when planing a flight otherwice you will endup in a huge burns and plane alignments.

In order to find a launch window from ISS to the Moon. Load a scenario "Docked at ISS".

1. Open IMFD and Target Intercept
2. Target the Moon
3. Switch "TOF-Unlocked" to "TOF-Locked". This will lock the time of flight keeping it constant.
4. Start increasing TEj until you reach minimum or zero EIn. This will happen somehere around TEj=330k.
Non-spherical gravity is turning the orbital plane of the ISS towards the Moon and the Moon is moving into a better alignment at the same time.

5. Switch "TOF-Locked" back to "TOF-Unlocked"
6. Wait until you have one more orbit to go before TLI.