Unplayable after FAR

[ComradeGoat]

TWR of over 5? That seems … excessive!

[hansman1982]

Ok, I took off the SRB's and fins and finally got to outer space. I guess I'll have to wean my addiction to those SRB's.

[ComradeGoat]

It's doing 200 m/s at 600 metres. If you wanted the effects of drag to utterly dominate, trying to break the sound barrier at sea level is a very good way to do it!

[Brabbit1987]

I do have to ask, do you all recommend this mod over vanilla? If so, why? If not, why? I kinda wanna know the up sides and down sides of using this mod.

[Scottiths]

Also of note, your center of lift was above the center of mass. That equates to an unstable rocket. Stable rockets need the center of lift below the center of mass.

*edit*

The further below CoM the CoL is the more stable the rocket. If it is really far below CoM you might actually have trouble turning at all

[hansman1982]

Ok, I lengthened the rocket. Now it just wobbles it's way up until the SRB's separate and then they collide into the rocket (another problem lately is they tend to release in to the main core of the rocket) and destroy it.

[hansman1982]

Here's my latest attempt. Destroyed at 1500 M.

It's frsutrating because I have NEVER had these issues before and I have had similar rockets with 6 SRB's firing at main stage.

[Scottiths]

According to all the indicators in that last SS it should work. The only think I can think of is that KSP does not tend to like pendulum rockets much, and your stage 4 TWR is a little high but within acceptable limits.

*edit*

Actually, I was thinking about it. Your boosters are set over your fins such that if there is any rotation at all they are going to collide when you decouple...

[Eric S]

Keep your SRBs low. Yes, that keeps their mass positioned low, but it also keeps their drag positioned low. In addition it gives them a better chance to stage without colliding with your ship.

Edited May 11, 2013 by Eric S

[xclusiv8]

Ask yourself, would those rockets fly in real life? No way. There is a reason for the way rockets look. You cannot install an aerodynamics mod and then say stuff like they flew without it and expect your rockets to fly with the mod. Insane.

[Daze]

If you want to use 4 SRB use this configuration:

@Brabbit: I had the same question some time ago... I want to use it but i want to know if the future improvement of aerodynamic would be similar to FAR

[sadron]

Well there's your main problem. Your rockets are too small. They're unfit for having enough thrust to get to orbit. You're not building model rockets here, you're trying to get to space.

[ferram4]

@hansman1982: Your main problem is that huge TWR and your push to speed like a maniac through the lower atmosphere. In general, aerodynamic forces are proportional to the dynamic pressure q:

q = 1/2 * air-density * velocity²

Now, consider the fact that you're going about 2 times as fast as my rockets tend to go at that altitude, so you're dealing with aerodynamic forces that are 4 times as strong as my designs. If you were to maintain control you'd probably end up getting into even stronger aerodynamic forces and destroying your vehicle as a result.

Here's what I'd do with your rocket: get rid of the SRBs, switch out the LV-T30 for LV-T45 so you have more control; this is especially important near Mach 1 where your fins won't be as effective at maintaining control.

When you launch, wait until it's going about 60 m/s and then start your gravity turn; that should allow you to reach orbit effectively. Leave the MJ ascent autopilot off and instead try using Smart ASS's KillRot function.

[Eric S]

According to all the indicators in that last SS it should work.

KSP doesn't have a center of drag indicator, and even if it did, it probably wouldn't match the FAR drag model, and the center of drag depends on the angle of attack, so it would move as soon as the craft wasn't aimed directly prograde.

[SalmonellaDingDong]

People using mechjeb to launch with FAR should change the ascent profile to 90% or so, and have it start at 0km. Be sure to have winglets on your rockets.

[ferram4]

@Eric S: FAR modifies the CoL indicator to model the updated aerodynamics; also, the CoL / CoD should not vary significantly based on angle of attack; you are mistaking the Center of Pressure with the Center of Lift / Drag. The Center of Pressure moves significantly; the Center of Lift does not unless you start to get stalling and flow separation.

[zzz]

Oh, I see. 4srb is overkill for such rocket. I ignite them in pairs and still need to throttling down main engine. It flies but it's not very good design.

Edited May 12, 2013 by zzz

[hansman1982]

Ok, it appears that maybe I was using a bit too much DeltaV before. Just restarted a new game, built a reasonable rocket and achieved orbit. Actually a very decent SSTO light lifter.

[hansman1982]

Here is my new ultra-light lifter (good for 10-15 tons to LKO):

[Van Disaster]

Excess TWR is ok too!:

Just not the best idea.

( heh, and an SSTO rocket too ).

[WafflesToo]

@OP

I do feel your pain, but it says more about how bad the aerodynamic modeling is in vanilla rather than how it broke your rocket (or my beloved spaceplanes for that matter).

It looks like you're on the right track now (it took me about a week's worth of rage-quits before I started to get it).

[Tw1]

I could launch things fine, most of my launchers are semi-asparagus, but still rocket-looking. They only needed bigger and better fins. But as it threw all the telemetry from mechjeb of, I decided to wait until the base game aerodynamics get improved, as mechjeb will be updated for that.