Splitting an eject burn using IMFD and BTC
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This tutorial is based on the Patsayev from World of 2001, but can be trained and tested in any other vessel, which gets supported by IMFD and BurnTimeCalcMFD. It explains how to do a multi-stage eject burn when leaving from Earth to Mars.
Setting up initial transfer orbit
- See IMFD tutorials. Nothing special here.
Calculating time of single eject burn
- See IMFD tutorials. Nothing special again here. Try to keep total dV during the burn below 5000 m/s - we also want to return.
- Open BurnTimeCalcMFD in the MFD which currently holds the Course view of IMFD.
- Enter dV of first burn. A good value for Earth is 2500 m/s, which results in a 10 h immediate orbit.
- Enter the time (TEj) from IMFD into the manual time position on BTC, subtract 30 seconds for staying in sync during the next steps. Plan at least 200 seconds for orientation.
- Set the BTC mode to manual time MD.
- Arm the auto burn feature (ARM) on BTC when manual time and countdown on IMFD are equal.
Orienting for the first burn
- Switch the IMFD showing the eject burn information into BV mode, showing the cross hairs for orientation. Do a quick rough alignment.
- 30 seconds before the beginning of the BTC auto burn, manually fine tune the orientation and center the cross hairs.
- The burn should now start automatically and also get terminated right on the desired mark. Keep the cross hairs centered manually. As this burn will take a long while, I recommend a good lecture. Just keep an eye on the orientation and correct it if needed.
In the immediate orbit
- Switch the IMFD again into the eject planning mode.
- Increase TEj until again reaching a good solution for the next burn (about 30,000 seconds later, so use Adj for speeding the process up).
- Enjoy the orbit. On apogee you have a nice view of Earth.
- When getting closer to Earth, prepare for the final burn.
The final burn
- As most of the velocity is already gathered by the first burn, we now only need to trigger IMFDs autopilot for the final burn. Activate it about 350 seconds before the beginning of the eject burn (AB).
- After this burn, you should be in a nice and smooth transfer to Mars.