Very hard to re-enter with FAR.

[FennexFox]

Yay! Re-entry!

I modified cfg of the rockomax brand adapter to make it a heat-shield, so the re-entry heat is not a problem.

(That`s a re-usable Multi Purpose Upper Stage, so it has no command pod.)

So, the real problem is aerodynamic failure.

I have no screenshot of the moment, and I don`t think that`s necessary, because it fails under any condition.

I have landed successfully lots of crew vessels and horizontal landing SSTOs even without heat-shield,

so I thought I mastered DRE&FAR re-entry but it`s very frustrating.

Do I have to turn aerodynamic failure off? That`s only way to solve this problem?

Making it more aerodynamically isn`t an option: it`s a upper stage of a rocket, and I don`t think it`s that much un-aerodynamical.

Edited September 4, 2014 by FennexFox

[Taki117]

It really depends on HOW it's failing. Looking at it if you are coming in and then try to flip engines first you are gonna have a bad time since your craft looks like it's made of multiple parts. Your best option is to come in engines first, Not the most ideal, but it will put your engines in a position where you can use them to slow down. Another option is to put a couple of radial chutes on it and use them high in the atmosphere to reorient your craft (Have them semi-deploy at a really high altitude and fully deploy at a really low altitude and then cut them before they fully deploy). If you do this though I highly recommend the RealChutes mod because it had a Drogue Chute option that I think will work wonders for you.

[Wanderfound]

Yah.

Basically, you need to fly it like an aircraft. If you let your nose get any substantial distance from prograde while you're still in the high supersonic, you're going to snap in half. That's a feature, not a bug.

If you can, reenter with a single part capsule or something with wings and control surfaces. These days, if I want to get something like a Mun lander back down intact, ti gets reinforced and streamlined just as much as a hypersonic spaceplane would be. Nosecones, struts, etc.

Also worth making sure that the parachute is directly attached to the bit with the Kerbals in it, just in case.

[FennexFox]

I appreciate your suggestions.

What I want to do is making a replica of falcon 9R upper stage, so engine-first re entry is not an option. attaching some parachute(I use realchute) is also not preferred.

I know it's very crucial to heading prograde in very high speed, so I use MechJeb smart a.s.s. to correct my heading and let aerobrake slow down my upper stage. But it heads my upper stage to orbital prograde, not atmospheric prograde. That slight difference make my upper stage disintegrated I think. So I tried free fall to keep heading prograde, but that also failed because engines are heavier then top.

I want to have a reusable upper stage just like what SpaceX has...

[Taki117]

I want to have a reusable upper stage just like what SpaceX has...

Then I suggest This mod, which gives you exactly what you want.

I also found

and the difference between what you have and what SpaceX has is that SpaceX uses a single part, where as you have at least 3.

[Wanderfound]

I appreciate your suggestions.

What I want to do is making a replica of falcon 9R upper stage, so engine-first re entry is not an option. attaching some parachute(I use realchute) is also not preferred.

I know it's very crucial to heading prograde in very high speed, so I use MechJeb smart a.s.s. to correct my heading and let aerobrake slow down my upper stage. But it heads my upper stage to orbital prograde, not atmospheric prograde. That slight difference make my upper stage disintegrated I think. So I tried free fall to keep heading prograde, but that also failed because engines are heavier then top.

I want to have a reusable upper stage just like what SpaceX has...

Mechjeb is nifty, but it can't match a good human pilot. Try switching to surface mode on the navball and keeping it headed atmospheric prograde manually.

If you must use MJ, again: surface mode, not orbital. You'll need to continuously adjust the pitch setting as you come in, by just a degree or two at a time.

But for either of those approaches to work, you need some control authority. Three options:

1) Lotsa SAS

2) Vernors/RCS for vectored thrust

3) Fins with control surfaces

Changing your engines for a few of the small radials might ease the weight distribution, too. You need your CoM to be in front of your CoL.

[steve_v]

How about fitting some deployable airbrakes to reduce your airspeed to a safe value?

[magnemoe]

Then I suggest This mod, which gives you exactly what you want.

I also found

and the difference between what you have and what SpaceX has is that SpaceX uses a single part, where as you have at least 3.

Here you are doing the upper stage flip who is not shown on the video, upper stage deorbit with nose first, then flip to engine first, its not show on the video, probably as they are not sure then to do it

As other says aerodynamic stability is critical at high speed, falcon 9 lower stage never goes very fast and does the flip in the upper atmosphere.

Upper stage has the problem that it goes fast until you get low and then you get high drag, no idea how space-x plans to do it,

[StainX]

Hmm on LazTek's mod, the reentry looks different than on that spacex video (engine first)....

Also it seems you have no monoprop on board, that would also help a lot, i guess

[Taki117]

Hmm on LazTek's mod, the reentry looks different than on that spacex video (engine first)....

Also it seems you have no monoprop on board, that would also help a lot, i guess

]

Also, keep in mind this is an earlier versson of the Mod (The current version is much different) Also, the point of me showing the animation was that, in order to get a successful lower atmosphere flip with FAR you need fewer parts that are subjected to extreme aerodynamic stresses. Tanks have notoriously weak connections when presented with FARs aerodynamic model.

This leaves two options:

A) Come in head first and wait until you are subsonic to try and perform the maneuver and do lots of praying

Use an alternate method of flipping your rocket such that it won't break apart when at high angles of attack.

[robot256]

I remember seeing at least one engine module, I think it was the latest LazTek Falcon 9 upper stage engine, that had heat shield tiles on the bottom of the fuel tank around the engine. That implies going in engine first is best. I always do it that way on stock + DRE.

But as a solution to one of your hypotheses, if you click the "Adv" button in the Mechjeb SmartASS, you can configure it to "Surface Velocity" and "Back". This will point you retrograde with respect to the surface instead of orbit.

[FennexFox]

Thank you for all your suggestions. I will try to "weld" the upper stage to improve structural strength.

[FennexFox]

Thank you for all your suggestions. I would like to try 'welding' all parts to make it more robust,

but my KSP got some weird error and can`t be opened.

As soon as I can play KSP I`ll try your suggestions.