Flight Question Mars Landing / Re-entry: AeroBrake or not?

[orbekler]

I reached successfully Mars with a UCGO Arrow Freighter + docked XR-2, I undocked and tried a re-entry with Aerobrake MFD, but at Olympus arrival I was too fast (1000m/s +). I had a second try, but this time I just burned retrograde until I almost stopped, and enabled the auto-land feature of hover autopilot, and this time I was successful, but the point is that it seemed to me a drunk Yuppi ya way to land.
Do you use AeroBrake for Mars? In this case, which is the altitude of your initial orbit, and when are you going to burn retrograde (my values were far from realistic - 300km ALT, from the Arrow Freighter and 1/2 orbital period)?

 

[Fabri91]

Mars can be pretty annoying, since its atmosphere is not dense enough to enable wingborne flight at usefully low speeds, but still too dense to be ignored. I normally slow down pretty quick at orbital altitude, and then do a powered descent, using hover thrusters to both slow down and manage the descent rate, starting with a high pitch-up attitude and then slowly leveling off as I slow down relative to the ground.

 

[orbekler]

So, basically AeroBrake it's not involved, right?

 

[Fabri91]

I don't use it on mars, no.

 

[orbekler]

Grazie mille, allora nel descent farò solo balar l' oec!:lol:

 

[exe-c]

But what if we think about enegry-effective way of the mars landing? Esp. ni DG/XR class winged vessels it should definitely involve aerobraking and gliding. But when to stop aerobrake, and start using hover engines? I don't like much idea of braking by the main engines and flying like a brick (engines forvard) at the planet with relatively thick atmosphere.

 

[Milenko44]

I use IMFD 4.2.2's basesync program and then kept an AoA of 40 until I was close to the base. Then I use the auto hover for the rest.

Good Luck!:thumbup:

 

[exe-c]

I use IMFD 4.2.2's basesync program and then kept an AoA of 40 until I was close to the base. Then I use the auto hover for the rest.

Good Luck!:thumbup:

Do you use retro thrusters to brake at the final approach? What's you altitude and distance from the base when you start hovering?

 

[Adelanthal]

A way that I found works is to set your perihelion fairly low, usually just below ground level, ~5 or 6 degrees before where you're trying to land. Get your altitude between 15 and 20 km from the ground and use pitch and bank to hold it there. If you've aimed and flown right, you'll be transitioning from aerobraking to hover engines at 400 - 500 m/s, slower if you're accurate enough that you're dropping onto your target directly. As with all things Orbiter, it's something that takes practice, and it's easier with the DG to get the feel for the technique.

 

[C3PO]

I usually try to save fuel with a 40° AoA reentry followed by a series of S-turns at around 10-20 km Alt. When I'm close to the landing spot I pull up as high as possible. When I reach apoapsis I pitch up to ~90°, and use the hovers to land like you would on a non-atmospheric body.
It requires a bit (or in my case, a LOT) of practise.

 

[orbekler]

Thank you very much, for your suggestions!
After some try I was eventually landing safely, and I did it using different ways: the easiest was a "geostationary" hovered descent directly over Olympus, the other way I used Aerobrake MFD, Reentry MFD, a LOT of retro thrust and a bit of aileron brake. I also made tests using hover with high pitch instead of retro thrust to lower speed, kind of "autorotation" brake, not a very confortable way though successful.

 

[Milenko44]

Do you use retro thrusters to brake at the final approach? What's you altitude and distance from the base when you start hovering?

I generally start hovering at 10km and use the retro engines to slow to a reasonable speed (usually around 300-400) and slow down according to how far I am from the base. Now I am still a beginner as well so I am sure there is a better way out there. Also, so far I have found this does not work on Venus because it rotates backwards and still have been unable to land there...