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Old 03-24-2017, 02:35 AM   #1
qbit
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Default LaunchMFD and throttle

I've searched for an answer to this and read the LaunchMFD manual, and I'm still not certain how to know how much throttle to apply. Apologies if this has been explained before.

I'm trying to take off from Brighton Beach in the stock Delta Glider in Orbiter 2016, and LaunchMFD keeps wanting to pitch the ship up almost 90 degrees. I hover above the launch pad a few hundred meters, rotate my ship in the right direction, and then throttle up a little bit to start moving forward. Pitch up about 20 degrees once I'm going about 200 m/s and then reduce hover until it's off. The entire time, LaunchMFD wants to go vertical.

I've found that I can get it to put the HUD target marker at a normal pitch by fiddling with the hover and throttle (seems to only start working at certain altitudes). It will be fine for a while and then shoot up to vertical again. It seems reducing throttle sometimes puts it back. As I'm climbing, the HUD target will slowly keep moving down. Throttling down the main engine will move the marker back up. If I let the marker get bellow 20 degrees pitch, it will shoot up again. Then I decrease throttle to bring it back down. Until the orbit is established and throttle is cut.

Should I be doing something else to make this a cleaner process? I don't understand why the MFD behaves this way on the Moon. On Earth, I can just give it full throttle, and it goes vertical until pretty high and then levels off into a perfect orbit at the MECO time. The MECO time is always changing for me on the moon, because I'm constantly adjusting throttle.

How should I be taking off on bodies like the Moon to make LauunchMFD behave correctly?

Thanks,
Paul
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Old 03-24-2017, 08:30 AM   #2
Enjo
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Quote:
Originally Posted by qbit View Post
 On Earth, I can just give it full throttle, and it goes vertical until pretty high and then levels off into a perfect orbit at the MECO time.
That's because DG has been designed for Earth, having its engine power adapted to enter Earth's orbit on a margin.

You're performing the right procedure, but you need minor adjustments:
- avoid high vertical velocity, because this confuses PEG. Hover up, hold altitude, enable the AP and immediately disable the hover engines
- when looking for optimal engine power, try to find the upper and lower limit of the PEG's convergence. Aim for power in the middle of the convergence range. For instance, in case of Earth, the max engine power is after the beginning of the range.
- when nearly in orbit and the PEG aims for 80*, cut the engines and wait for apogee to circularize. This means that the PEG's job is nearly done anyway.

I think it could even be possible for Launch MFD to find such optimal power, but I'm focused on totally different things right now.

Last edited by Enjo; 03-24-2017 at 10:56 AM.
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Old 03-24-2017, 02:56 PM   #3
qbit
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Thanks for the info. I've got to where I prefer to disable pitch guidance and just use the heading guidance and control my own ascent. I cannot, however, launch into a circular orbit without a circularization burn like LaunchMFD does on Earth with the DG. That's impressive.

Thanks for this addon and all the others. I also use TransX, HUDDrawer, and BurnTimeCalc.

Paul
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