Rover EDL questions...

[MaverickSawyer]

I'm trying to design a capsule to enclose a Duna rover during the Entry, Descent, and Landing sequence. Normally, that's no big deal... but I want to do it in a horizontal format, similar to the ones shown in the now-defunct Constellation mission:

I'm using Procedural Fairings, so I can eject the backshell, and that's working fine. Even got a theory as to how I can keep the nose up during the late part of the entry as the air thickens. It's keeping the dang craft horizontal after I eject the backshell that's the issue. Granted, I'm testing it on Kerbin and the flip happens low in the atmosphere, but it's still a fair ways up when it does flip, and I'm afraid that it could happen on Duna during the terminal descent.

Anyone have any pointers on how to keep these things going the right way?

[Snark]

When you say it "flips", what do you mean, exactly? What orientation does it take? Also, why does it matter if it flips on fairing separation-- won't it right itself when the chutes deploy? If you're looking for practical feedback on your rover design, screenshots would help

[Alshain]

There is no easy way to do this. I even recently suggested a mod to help but no takers. Unfortunately I'm not good enough a mod developer for this kind of undertaking or I'd do it myself.

http://forum.kerbalspaceprogram.com/threads/135188-Parachute-Build-Aid

[Razgriz1]

So were I to guess, I would imagine that those engines on the lander in the video have at least some form of attitude control, which would provide some control to counteract the aerodynamic forces. Additionally, I think I remember reading that the actual design of the Aeroshell landers had control surfaces that did not make it onto all of the artists' renderings, such as the one in the video.

My advice would be to not worry about sticking to that video too much and instead trying to do it in a way that works. For example, you could try to decouple the heatshield first, to keep it upright.

[MaverickSawyer]

When you say it "flips", what do you mean, exactly? What orientation does it take? Also, why does it matter if it flips on fairing separation-- won't it right itself when the chutes deploy? If you're looking for practical feedback on your rover design, screenshots would help

It goes from a prograde and level orientation to a retrograde and inverted orientation.

As for the orientation, two reasons:

Practical: my test flight ended badly when the wheels phased through the bottom fairing piece, my "heatshield", and hung up on it. Parachute deployment promptly tore them off. If I can get a clean separation in a level attitude, I suspect this issue will disappear.

Aesthetic: I strive to do things as realistically as possible, sometimes leading to overly complex systems. Yes, I could probably just blow the fairings and the base off all at the same time and freefall the rest of the way. Probably the option I would use if going to Laythe or Eve. And I want it to emulate a system that NASA was eyeing for real flights.

I'll get some screenshots right away, though. Hopefully the airbrakes will work properly this time, instead of only two of the six performing as intended. :/

- - - Updated - - -

So were I to guess, I would imagine that those engines on the lander in the video have at least some form of attitude control, which would provide some control to counteract the aerodynamic forces. Additionally, I think I remember reading that the actual design of the Aeroshell landers had control surfaces that did not make it onto all of the artists' renderings, such as the one in the video.

My advice would be to not worry about sticking to that video too much and instead trying to do it in a way that works. For example, you could try to decouple the heatshield first, to keep it upright.

I have 66kNm of torque in each axis, enough to flip it around just fine up high, and a set of airbrakes that I deploy down low. Still doesn't make a difference.

Maybe I should be doing this in FAR, instead of stock aerodynamics.

- - - Updated - - -

Hmmm.... maybe I need to use a drag/drogue chute instead of airbrakes. Time to go back to the drawing board...

Oh, and here's the capsule in flight on Kerbin...

[Temporal Wolf]

What does the payload look like?

My guess is the drag on the payload is flipping it around, which means you may want to have airbrakes or a few drogues on the payload rear end deploy when you pop the fairing endcap.

There is no easy way to do this. I even recently suggested a mod to help but no takers. Unfortunately I'm not good enough a mod developer for this kind of undertaking or I'd do it myself.

http://forum.kerbalspaceprogram.com/threads/135188-Parachute-Build-Aid

This might not be as easy as you might think, as it is not just the parachutes, but the entire drag of the craft that matters... and that is based largely upon the direction of travel... there may be multiple 'stable' decent angles depending on which direction the craft is traveling.

Edited October 13, 2015 by Temporal Wolf

[MaverickSawyer]

What does the payload look like?

My guess is the drag on the payload is flipping it around, which means you may want to have airbrakes or a few drogues on the payload rear end deploy when you pop the fairing endcap.

I tried airbrakes, but they were not enough to get proper orientation. I wound up adding a RealChute drogue chute "above" (relative to the crew orientation) and aft of CoG to stabilize the craft for now. Some testing will be required to see if it'll perform as expected.

Speaking of which, other than HyperEdit, anyone have any bright ideas as to how I can get a proper test of my EDL system to see how it'll behave on Duna? I have zero experience landing there with the new aerodynamics, and my only landing was rocket powered and a tail sitter. :/

[Temporal Wolf]

I finally broke down and installed HyperEdit to test Eve's new atmo before sending my very high cost mission... that's the only easy way to get a true test I know of.

EDIT: Although you could start a sandbox, copy your craft, launch it with a mammoth engine and infinite fuel on and just blast it over... HE would be easier, but I guess that would work... just quicksave before you get there so you can test multiple reentries.

Edited October 13, 2015 by Temporal Wolf