Problem Can't Seem To Reenter The TX

[Nicholander]

When I try to fly to TX back to Earth from orbit, and even though I follow the instructions, it still doesn't work.

What happens:
1. Do deorbit burn until perigee is 0M (What I think the PDF means by "The Earth's radius")
2. Wait until 120Km
3. Make Aerobrake MFD make my AOA 50.
4. Try to wait until my altitude starts going back up to go to phase C, but even though the diagram in the PDF that the altitude will start going back up at around 70 Km, and the you go to phase C at 76 Km, it never happens, and I just continue going down until I crash into the ground.

It was made for 060929, but I did the same things it tells me for ascent and it worked fantastically, so the aerodynamic properties can't be off. So I suppose I'm just doing something wrong, so what am I doing wrong?

Thanks in advance for helping!

 

[PeterRoss]

The main problem here is that you can't entrust AerobrakeMFD with controlling Tx AoA. It never worked for me, all of my succesfull Tx reentries were made manually by the book.

 

[Ripley]

I've never flown the TX, but I remember AerobrakeMFD needs an per-ship, in-atmosphere 360° flip to record lift/drag parameters, followed by Shift-S to permanently save it.

Orient your ship pro- or retrograde and do the flip.

File will be created in ..\modules\plugin and its name will be "ship_name.LD".
If you go into MFD's L/D page you'll see the parameters building up while performing the 360.

Original gp's post here (in Italian)
orbiteritalia.forumotion.com/t206-aerobrakemfd

Scroll down to 4th post.

 

[Nicholander]

Ripley, I did what the post said, and I got the graph to appear in AeroBrakeMFD, but after I did the 360 degree flip and press SHIFT-S, nothing appeared in the Modules/Plugins folder, and that is the same folder with the ld files. (There's DG and XR files in there)

 

[Ripley]

Right SHIFT if you open AerobrakeMFD on the right MFD (no external MFD).
Left SHIFT in the other case.

 

[Nicholander]

Ah, thanks!

---------- Post added at 05:10 PM ---------- Previous post was at 04:52 PM ----------

Hmm... I tried doing the same procedures the PDF says (Still using AeroBrakeMFD, with the tx.ld file now) and I still never start gaining altitude at 70 Km. Seriously, what the heck am I doing wrong? Is the PDF slightly wrong and I should have a AOA of 47 instead of 50? And there doesn't seem to be any video tutorial either.

 

[dgatsoulis]

It's been ages since my last flight with the TX, so take the following with a grain of salt.

1. Just a clarification: when you say:

Do deorbit burn until perigee is 0M

you mean the PeA in OrbitMFD right? Not the PeD.

2. I don't recall the need for AerobrakeMFD's Attitude hold AP.
IIRC the procedure is:
A) Make the deorbit burn at the opposite side of the planet from your landing site. Aim for a PeA of 0 km.
B) When @ 100 km alt, pitch at 50° AoA and full trim up.
C) @ ~70 km the spacecraft's nose will drop to ~ 13° AoA, adjust trim as needed by watching the projected groundtrack on AerobrakeMFD.

If you are "falling short" of your target base with this procedure, try making a slightly smaller deorbit burn, aiming for a higher PeA. Try increments of 10km until you get it right.

Hope this helps

 

[Nicholander]

Thanks for the help dgatsoulis, but this is what I think you mean and what happens when I do that:
1. Deorbit until PeA is 0
2. Wait until 100Km.
3. Set trim to full up and make AoA 50, I don't use AeroBrakeMFD and I then turn off the RCS, just the trim doing anything.
4. At about 70km I start to go backup and my AoA is around 13 degrees, but it makes my ApA 150 Km and I go back into space, far above my landing location.

So did I misinterpret your instructions, or something else?

 

[dgatsoulis]

No, that sounds about right, except the bouncing out of the atmosphere bit.
Perhaps, holding the AoA near 50° for a little longer (with the use of RCS) might help. Like I said, it's been very long since my last TX flight.

Can you post the scenario just before the deorbit burn?

I think I have an Orbiter 2006 installation with the TX on my old laptop. I'll check and get back to you.

 

[Nicholander]

No, that sounds about right, except the bouncing out of the atmosphere bit.
Perhaps, holding the AoA near 50° for a little longer (with the use of RCS) might help. Like I said, it's been very long since my last TX flight.

Can you post the scenario just before the deorbit burn?

I think I have an Orbiter 2006 installation with the TX on my old laptop. I'll check and get back to you.

There already is a before deorbit scenario, or do you have an older version of the Tx? Anyway, here's the scenario that comes with it:

BEGIN_DESC
LEO, TX before deorbit burn (T + 1914 s.)
END_DESC

BEGIN_ENVIRONMENT
  System Sol
  Date MJD 53125.1837264468
END_ENVIRONMENT

BEGIN_FOCUS
  Ship TX
END_FOCUS

BEGIN_CAMERA
  TARGET TX
  MODE Cockpit
  FOV 70.00
END_CAMERA

BEGIN_HUD
  TYPE Surface
END_HUD

BEGIN_MFD Left
  TYPE Orbit
  PROJ Ship
  REF Earth
END_MFD

BEGIN_MFD Right
  TYPE Map
  REF Earth
  BTARGET SRC - Space Port
END_MFD


BEGIN_SHIPS
ISS:ProjectAlpha_ISS
  STATUS Orbiting Earth
  RPOS -3298133.31 -5458725.97 2179730.81
  RVEL -6556.838 4011.656 139.074
  AROT 110.02 -10.09 79.99
  PRPLEVEL 0:1.000
  IDS 0:588 10 1:586 10 2:584 10 3:582 10 4:580 10
  NAVFREQ 0 0
  XPDR 466
END
Mir
  STATUS Orbiting Earth
  RPOS 6019872.13 -174976.48 -2861098.92
  RVEL 3322.492 426.756 6971.048
  AROT -0.00 -45.09 90.01
  IDS 0:540 10 1:542 10 2:544 10
  XPDR 482
END
Luna-OB1:Wheel
  STATUS Orbiting Moon
  RPOS 1992689.07 -1019426.11 -689.87
  RVEL 674.259 1317.895 0.707
  AROT -0.00 -0.00 60.58
  VROT 0.00 -0.00 10.00
  IDS 0:560 10 1:564 10
  XPDR 494
END
GL-01:DeltaGlider
  STATUS Orbiting Earth
  RPOS -5871481.16 1123804.67 -2713880.42
  RVEL 3470.756 2827.653 -6385.258
  AROT -25.41 72.60 -1.89
  PRPLEVEL 0:1.000 1:1.000
  NAVFREQ 0 0 0 0
  XPDR 450
  NOSECONE 1 1.0000
  GEAR 0 0.0000
  AIRLOCK 1 1.0000
  LIGHTS 1 1 1
END
TX:tx
  STATUS Orbiting Earth
  RPOS -5872441.98 1123074.05 -2713728.31
  RVEL 3469.331 2828.325 -6385.049
  AROT -23.88 25.45 -0.62
  PRPLEVEL 0:0.109 1:0.981
  IDS 0:1 100
  NAVFREQ 0 0 0 0
  XPDR 450
  MAINDOCK 1 1.0000
  GEAR 0 0.0000
  COVER 0 0.0000
  WINGS 1 1.0000
  AIRBREAKS 0 0.0000
  MT_MODE 2
  WING_MODE 1
  RCS_MODE 2
  LIGHTS 1 1 1 0
END
END_SHIPS

Also, I'll try reentering while holding the AoA of 50 for a bit longer an tell you what happens.

---------- Post added at 06:32 PM ---------- Previous post was at 06:17 PM ----------

I tried it again, same result, and actually I used AeroBrakeMFD to hold my AoA at 50 until 70 Km, and then I made it stop and turned the trim up, same result. ApA at 150 Km right over the target.

 

[dgatsoulis]

I now remember why I stopped flying the TX. Wonderful bird, but the reentry was a drag. (pun unintended).

I've had some success with this method:
-Wait until you are less than a ¼ of an orbit away from the base (~9000 - 8000 km) and make a retrograde burn until your ground track in MapMFD shows that you'll be crashing on the surface exactly at the base.

-At ~100k altitude, level the wings and pitch to an AoA of ~58.7°

-Open AerobrakeMFD, hold the AoA and bank a little if needed.

-Release the Numlock (if you had it on) and press Shift and "8" on the numpad, adjusting your AoA and looking at the ground track of AerobrakeMFD. Right or Left Shift depends on the side AerobrakeMFD is on.

- When you start pulling about 7g -altitude should be ~40k- release the AoA button and trim all the way down. Trim back up to get the velocity vector close to the horizon.

It is fast and pulls a lot of gees, but you should end up at ~25k alt, with the base a few hundred km ahead of you.

 

[Nicholander]

I guess it works, I haven't completely tried it (I messed up and released the AOA autopilot at around 20-25 km instead of 40), but everything previous to that worked fine! But, I wasn't able to change the AeroBrakeMFD's AOA setting with Shift-8, and I'll try it again later.

 

[Aeadar]

4. At about 70km I start to go backup and my AoA is around 13 degrees, but it makes my ApA 150 Km and I go back into space, far above my landing location.

IIRC it was at this point that I needed to begin performing S-turns in order to keep the lift vector from taking the ship back up, out of the atmosphere.

 

[dgatsoulis]

I guess it works, I haven't completely tried it (I messed up and released the AOA autopilot at around 20-25 km instead of 40), but everything previous to that worked fine! But, I wasn't able to change the AeroBrakeMFD's AOA setting with Shift-8, and I'll try it again later.

NumLock. If it's on, then it won't work. Also the Shift key is on the side of the MFD.