Question Any reentry AP?

[Ark]

in what distance from the base should i be when RETRO burning?
i'll take this knowlegde with me and whenever (if) i'll fly the real DGIV then i'll remember you, great guys that teached me when i was so young.
but if any case somebody can make a corresponding replay scenario, then post it in this thread.

180 degrees away, drop your PeA to about 60k, then adjust your AOA to until aerobrake says you'll arrive close enough. You may have to tweak it later on if it looks like you're going to overshoot or come up short.

 

[Tommy]

Some things that have been left out here:

The main variables in a post interface re-entry (after you've entered the atmosphere, 90k to 120k altitude depending on who you ask) are temperature, altitude, vertical speed, vertical acceleration, velocity, and acceleration. For any given velocity there is a minimum safe altitude. You need to be above that to survive, so your Vertical Speed (VS) should complement your Acceleration (ACC). For most gliders (DG, DGIV, XR series) in a high drag configuration (Angle of Attack > 30 degrees) that works out to about -80/ms VS.

Of all the variables that determine whether a re-entry is survivable or a failure, VACC (vertical acceleration) is the only one of which you have direct control.
You'll want to keep this a positive number if your VS is below -100ms and negative if your VS is above -70ms (note that these are negative numbers, so if your VS is -115 you want a positve VACC). Keep the VACC close to zero, it's easy to get to much negative VACC and not be able to pull out quickly enough when you start to overheat. Plan ahead and use small adjustments early to avoid needing large adjustments (which raise the temp). Many pilots have found that pitching down causes a spike in temperature before it begins decreasing when their DGIV exploded.

AerobrakeMFD does not give you a valid re-entry plot until you are below 200k alt. Above that it doesn't consider aerodynamics. It can still be used to determine when to stop a de-orbit burn, it's close enough.

If you de-orbit opposite your target, Aerobrake will give you a re-entry that "bounces" a little, and at times you will be climbing. That's normal given the long re-entry, and just trust Aerobrake's map and hold the AoA that shows you landing on target. A better distance might be 16.5M from the base if coming in from LEO (from ISS or MIR).

Gliders have a lot of lee-way on when to perform a de-orbit. 180 degrees is safe, but a bit long, but a Glider can de-orbit quite a bit before that even, almost 360 degrees. A DG-IV with no cargo and minimal fuel can be de-orbited as close as 6M from target and still make a deadstick landing (use 6 degree ReA, and initial pitch angle of 20 degrees - when VS raises above -200 pitch up to hold -80ms VS until Aerobrake no longer shows you overshooting, then pitch down as dictated by Aerobrake.

You can also get well over 5M cross range if needed.

 

[n122vu]

Mike Norman (the author of AFCS) included guidance files (found in the modules/plugin folder in Orbiter)for both the STS and DG/DGS for versions 2 and 2P1. It will also work with the XR1 and XR2. There should be three .ini files included:

AFCS.ini
AFCS (STS).ini
AFCS (DG).ini

The module always looks for the "AFCS.ini" file for guidance data. As installed, this file has the STS data pre-loaded.

If you wish to fly the DG/DGS/XR1/XR2, you'll need to copy the data from "AFCS (DG).ini" and paste it into the "AFCS.ini" file for it to work. The last thing you'll need if flying any of the DG-based vehicles is change the EI distance from the default (8.06M) to 6.98M. Two other important things to remember when using AFCS for the DG-based vessels:

1). Make sure the retro doors are OPEN. The .dll looks to see if the vessel has retro thrusters. If found, the autopilot uses the retro thrusters for the de-orbit burn. If you don't have the doors open, you're stay in orbit. But make sure you close the doors after the de-orbit burn is completed...otherwise, you'll be turned into plasma trying to re-enter.:blackeye:
2). Make sure no attitude-hold autopilots (ie. Prograde/Retrograde/HLevel) are on. Otherwise, AFCS will be unable to orient the spacecraft

I know Doug Beachy isn't a huge fan of autopilots for the XR-series, hence his reluctance to install them. To keep in that spirit when flying one of those beautiful birds, I turn off all automatic guidance and just leave the flight director on. Flying that profile manually to an unpowered landing is one heck of a challenge...and all the more satisfying when you do it successfully.

Best,

Cale

I have version 2, and do not have the (STS) and (DG) ini files, only AFCS.ini. I checked the zip archive, which I downloaded from Mike Norman's site, and they are not included. Am I missing something?

 

[garyw]

Tommy, Thank you for that post. I've learnt a lot from that and will be putting it into practice!

 

[AlphAPollo]

escuse me gary, guess i forgot this...... no end to homework.........
ill try retro burning on opposite side of planet, and i know the DGIV reentry checklist.