Flight Question [Orbiter 2016] Atlantis re-entry and landing

[coussini]

Hi everybody. Happy earth day for us. I have a question on the re-entry and the landing for the default Atlantis. I watched and read several tutorial on re-entry ... but all are not concerning the default Atlantis for Orbiter 2016.

I use several tool (MFD)... but i can reach my goal. Saddly.

Goal : Land the Atlantis at Cape Canaveral at RWY33

Question 1 : If you use BaseSync, do you use a specific Angle, Ant and Alt value in De-Orbit Program

Question 2 : Do you use GlideSlope or AeroBrake MFD to monitor your re-entry

Question 3 : I tried to use GlideSlope using config (BASE: Cape Canaveral, Rwy: RWY33, GS: Space Shuttle) and mode DATA for monitoring... but that's really tough to reach the reference according to the actual. For that... which value are important for you. To reach the goal.

Special Request : If you can give me some snapshot... I can understand well the procedure.

Final Word : I know that I should pitch up to 40° and bank left of right increase the Vertical Speed Rate. But what's more... Thanks for your participation and I appreciate you help for me.

Best Regards

 

[N_Molson]

Final Word : I know that I should pitch up to 40° and bank left of right increase the Vertical Speed Rate. But what's more... Thanks for your participation and I appreciate you help for me.

That's the idea, you perform "S-turns" and keep the AoA (Angle of Attack) high. You have to keep in mind where is the airflow relative to your ship attitude. Enabling the forces/axis display in external view might help you. From my own experience trial and error works, eventually.

 

[coussini]

That's the idea, you perform "S-turns" and keep the AoA (Angle of Attack) high. You have to keep in mind where is the airflow relative to your ship attitude. Enabling the forces/axis display in external view might help you. From my own experience trial and error works, eventually.

(If you speak french... Toulouse... can you explain this in French... that’s my language... )

What do you mean about the airflow relative to your ship attitude. Can you explain more this point with example or value to be more clear fore me.

What is the force/axis display that you said. Can you explain more this point... and what kind of mfd do you use for that. What are the variable or values that
I must check (monitoring)...

Thanks and wait for any awnser.

 

[Marg]

I used GlideSlope2, you tu see those two curves\slopes during reentry
One is for altitude, another curve -speed. If your flying curve (I think yellow - altitude one) goes not as steeply down as "REFERENCE" curve, you have to roll almost 85-90 degrees (and watch direction to Canaveral, so Roll must be reversed several times), so you are going down, but it all happens with some latency!

 

[N_Molson]

Dans la section 22 du manuel d'Orbiter : "Visual Helpers" (Ctrl-F9). Cette fonctionnalité permet d'afficher les axes XYZ ainsi que les forces comme la portance (lift), la poussée (thrust), la traînée (drag)...

La valeur à surveiller est "AoA" (Angle of Attack = Angle d'attaque) sur "Surface MFD". Cette valeur indique l'angle entre le nez du vaisseau et le flux aérodynamique (le vent-vitesse pour simplifier). En général, un AoA positif (dans des limites raisonnables) génère de la portance et de la traînée. Le principe des "S-turns" (virages en S) est de garder un AoA très élevé (40°) pour générer beaucoup de traînée et freiner le vaisseau progressivement. On ne peut pas laisser le nez du vaisseau pointé vers le haut, car la portance générée ferait rebondir le vaisseau sur l'atmosphère (puis décrocher). Donc on garde bien ces 40° d'angle, mais on bascule le vaisseau sur le côté, ce qui transforme la portance en virage. Dans le même temps on surveille la vitesse verticale (vertical velocity) et on la contrôle avec l'angle de roulis (roll).

L'idée générale c'est de toujours exposer le ventre du vaisseau qui est la seule partie protégée contre la friction de l'air, tout en gardant le contrôle de la trajectoire, en faisant des virages plus ou moins longs.

 

[Urwumpe]

Keeping the AOA constant during reentry is not only easier for thermal protection (since the air always comes from the same direction), it also makes the guidance and navigation part easier. You let the computer hold the AOA and sideslip constant and depending on the decelleration (in g), you only need to vary one variable: The bank angle.

The simplest way is to keep bank zero until you reach zero vertical velocity, and then bank to the sides to steer towards the landing site while controlling your decelleration. If your decelleration becomes too high, you reduce bank angle gradually. If it is too low, you increase it, if needed until you are flying upside down and have the maximum force pulling your trajectory downwards (gravity + lift)

If you have a MFD that can calculate how much decelleration you need for reaching your target, you only need to keep the current decelleration close to the target value.

Everytime your course goes too far away from the target, you invert your bank angle. The result is automatically these S-turns. Initially, you can allow quite large difference (Real shuttle allowed up to 10.5° deviation between current ground track and heading towards landing site). Later you use different strategies (TAEM) to prepare for landing.

Also for the Space Shuttle, you start reducing your AOA from Mach 8 downwards to turn from a blunt body reentry capsule to a better glider.

In SSUs aerodynamic model, it is important to keep the speed brakes deployed during reentry, it is not that important in the default Atlantis.

 

[coussini]

Merci n molson pour tes trucs. Je vais essayer. Merci grandement cher ami.

Urwumpe... that’s interesting. I try this also. Thanks a lot. Dear friend.

 

[N_Molson]

In SSUs aerodynamic model, it is important to keep the speed brakes deployed during reentry

I wasn't even aware it was possible at all. I thought they were too fragile to be deployed during reentry and were only used for final approach. But now that I think to it, a 40° AoA protects the tail from the plasma flow, and the dynamic pressure isn't that high. And yes, having more drag in the tail certainly helps to stabilize the orbiter :thumbup:

 

[DaveS]

I wasn't even aware it was possible at all. I thought they were too fragile to be deployed during reentry and were only used for final approach. But now that I think to it, a 40° AoA protects the tail from the plasma flow, and the dynamic pressure isn't that high. And yes, having more drag in the tail certainly helps to stabilize the orbiter :thumbup:

The speedbrake is automatically opened to 81% at Mach 10. Besides, the RSB panels aren't that flimsy and they are protected with mixture of thermal blankets (on Columbia and Challenger these were LRSI tiles) and HRSI tiles.

 

[coussini]

Thanks for these precisions. Best regards.

 

[Marpilot]

Hi, I am very new to this and like it!

I am always overshooting Atlantis reentry 2.
Maybe too heavy? I have 18T of fuel.
At alt 70.000m I am unable to maintain 40 deg pitch. Should I use RCS ROT all the time?
Please help me.
Thanks

 

[Swisslady]

I am unable to maintain 40 deg pitch.

Yes, me too.... unable to maintain during hole Re-entry...

Any help?

Thanks