Lagrange MFD for Orbiter 2016 – Co-planar transfer from LEO to E-M L1


Hello and welcome to this Orbiter 2016 video We will be trying out the new Lagrange MFD 1.0 that has just been released for Orbiter 2010 Let’s jump right in I am placing a DG in a Moon co-planar LEO (300 km) Checking the Moon’s inclination and LAN in Orbit MFD Entering the parameter in the scenario editor for a parking orbit at 300 km altitude Here we are. Checking my R.Inc with Align Planes MFD All set. R.Inc: 0.00° Opening 3 instances of Lagrange MFD (left – right and external) Selecting the target (E-M L1) The doted curve shows the position of the L1 and the gray curve show the position of the Moon This page shows the S4I’s settings. (4th order sympectic intergrator) That’s the “engine” of Lagrange MFD The “Calc Rng [d]” line show how far into the “future” the S4I’s prediction extends. Changing the “deltaT” changes the engine’s time-step, resulting in a change in the range of the prediction The ITER changes the # of iterations the engine runs, affecting the range of the prediction and also the calculation time of each step I’ve set it to 6 days prediction with 10 seconds time-step. Setting the RNG to “28d” will extend the prediction out for a whole orbit of the Moon around Earth You can play around with these settings until you have the prediction extending where you want, with the resolution (deltaT) you desire. For a tranfer to L1, I want a range of ~6 days with a deltaT of ~10 seconds. YMMV Time to setup the transfer On one side I want the PLAN page That’s where I’ll enter the variables of the Trans-L1 burn On the other side I want the ENCOUNTER page So I can see the concequenses of the planned burn. First I “ARM” the plan and then enter the prograde dV I’ll need In the middle MFD I can see the shape of the planned trajectory On the right the “Enc.Pos.” shows me how close I’ll get to the target if I perform this burn A little bit of fiddling with the variables, until I get the encounter position AND velocity to a minimum I can also see the encounter position and velocity in the PLAN page on the left That seems ok. 3090.2 m/s Prograde to arrive at L1 352k seconds later with a relative velocity of 701.6 m/s Time-warping to get closer to the burn That’s close enough. Now switching to the AUTOPILOT page. The AB button will “AutoBurn” my plan. Time-warping until the burn. At 200 seconds before the burn the AP will lower the time-accel at x10 At 20 seconds the AP will return the time-accel to x1 Burning. I recommend performing the burns @ 1x time, but I will time-warp here to keep the video a bit shorter Returning to x1 10 seconds before the burn ends. (not automatic) Burn completed. “Cleaning up” with a bit of linear RCS. All done. Coasting to the first MCC. I am looking at the Enc.dTime on the right to see when I arrive and the Enc Pos to see if the prediction holds Looking pretty good. I’ll perform my MCC just 1 day away from the L1 Changing the S4I settings to get a better “resolution” (lower deltaT and range) Since I am outside of Earth’s SOI, I am switching the reference in the FRAME page Changing the S4I settings to get a better “resolution” (lower deltaT and range) The prediction now extends out only for 2 days I could enter the MCC as a burn in the PLAN page, but I am arriving so close, that there is no need I have the spacecraft oriented Prograde relative to the SUN and using linear RCS, while watching the ENCOUNTER (LIVE) page Arriving ~50 meters away from the target. Time-warping to ~ 3 hours from encounter Rinse and repeat. There is no need to try and be so accurate. A few km away from the L1 are fine. But I can’t help myself! 😀 Time-warping to ~1000 secs away from L1 Another needless MCC. All 3 of them cost less than 3 m/s in delta-V Arriving 0 meters away from L1. This will probably confuse the AutoHold AP. Time to setup the arrival burn. I need to match my velocity with the L1 To do that, I need to enter a burn with the same dV as the Enc.Vel, but with opposite signs in the velocity components Without arming the plan, I set the 3 velocity variables first Remember: OPPOSITE signs! Now I can arm the plan. The time of the burn needs be BEFORE the encounter time Checking the distance I’ll travel during the burn with BurnTimeMFD ~ 9 km. I’ll adjust the Time to get the Enc.Pos at ~ 1/3 of that The prediction is “jumpy” That’s because the S4I engine finds more than one “arrivals” at the L1. after the burn When that happens, simply raise the deltaT a bit. This will keep the prediction stable. Time-warping to the burn AB to engage the AutoPilot Still a bit jumpy. But the orientation is correct, I’ll be fine Autoburning All done. I am 5.4 km away from the L1 with a relative velocity of 0.077 m/s I’ll try the AutoHold AP. Not sure how it will work this close and with this low velocity from L1 Nope. I’ll do it by hand. (The AH isn’t optimized in this version of Lagrange MFD) It’s not that the AutoHold AP doesn’t work. It’s just that I am so close to the L1 that I can do better (dV wise) if I perform the rest of the approach manually. Using linear RCS to get closer. I am looking at the Rel.Pos and Rel.Vel. The goal is to make sure that each component of the Rel.Pos has a different sign than the corresponding component of the Rel.Vel. This way I know that I am “closing” the distance to L1 Of course this is a ridiculous level of accuracy. There is nothing wrong with matching the velocity right here But I will end this video exactly at L1 There. 0 meters from L1 with 0 m/s velocity Let’s extend the prediction to see how long we’ll stay here Right now we are “riding the rail”. IMFD’s map also agrees. Looks like we’ll be in the vicinity for at least 15 days. A bit of station-keeping every week or so should keep us nice and close. Thanks for watching!

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