Trekkie148's unstable rockets question.

[EdwardB3020]

Hey um KSP developer's um could you fix this glitch on whenever i build a rocket, it highly relies on rocket fin's being on the center of mass and when I do that, it looks very very ugly, and if I don't the rocket just flips for no darn reason but if I go to say for example version 1.4.2, 1.4.3 or even 1.4.4 that won't happen. Say for example I put together this very simple basic rocket containing of the mk1/3 command pod from the new update 1.4 with the big orange tank and a mainsail with a decoupoler for the pod to land safely in the kerbin ocean with none other than a parachute to coast it down safely. But the twist is or more or less "Bug" is what i'm calling it, in the latest update 1.4.5 if I launch a simple rocket with no fin's and I do know that the pods are lifting surfaces BTW, The rocket flips out of control even with reaction wheels and also I did not add reaction wheels to the rocket and I do know that they make stuff in KSP more stable well because KSP logic, I felt like not adding one and even with them the rocket still flips out of control and i've only concurred this event on none other than this update which is a pain in the @$$ because it's annoying to fix every time I try to build a darn rocket that flips for no apparent reason,

 

KSP developer's please fix this bug if you can and I do not have any log's or videos showing this and I am not lying to you for real, 

 

I have to add rocket fins inside of the darn fuel tank and it increases part count and my memory hates it! 

4 minutes ago, Trekkie148 said:

Hey um KSP developer's um could you fix this glitch on whenever i build a rocket, it highly relies on rocket fin's being on the center of mass and when I do that, it looks very very ugly, and if I don't the rocket just flips for no darn reason but if I go to say for example version 1.4.2, 1.4.3 or even 1.4.4 that won't happen. Say for example I put together this very simple basic rocket containing of the mk1/3 command pod from the new update 1.4 with the big orange tank and a mainsail with a decoupoler for the pod to land safely in the kerbin ocean with none other than a parachute to coast it down safely. But the twist is or more or less "Bug" is what i'm calling it, in the latest update 1.4.5 if I launch a simple rocket with no fin's and I do know that the pods are lifting surfaces BTW, The rocket flips out of control even with reaction wheels and also I did not add reaction wheels to the rocket and I do know that they make stuff in KSP more stable well because KSP logic, I felt like not adding one and even with them the rocket still flips out of control and i've only concurred this event on none other than this update which is a pain in the @$$ because it's annoying to fix every time I try to build a darn rocket that flips for no apparent reason,

 

KSP developer's please fix this bug if you can and I do not have any log's or videos showing this and I am not lying to you for real, 

 

I have to add rocket fins inside of the darn fuel tank and it increases part count and my memory hates it! 

Oh also when I looked at the reentry particle effects with no mods installed, I do know that they added a new reentry effect in version 1.4 and when I go to 1.4.5 the effect goes to the old 1.3 one... can someone help me out here please?

[AVaughan]

@Trekkie148 It's a bit hard to be sure without a screenshot, but it sounds like your design is aerodynamically unstable.  In other words flipping out of control is to be expected.  You normally fix that with some fins near the base of the rocket, to move the centre of lift backwards.  Check the centre of lift and the centre of mass display in the VAB.  For a rocket to be stable, the centre of lift needs to be behind the centre of mass (ie like a dart or an arrow with the mass concentrated forward, and feathers aft).  Note that this needs to apply during flight, not just at launch time.  For a rocket with a heavy mainsail, and no upper stage, your centre of mass is probably moving backwards during the flight as the mass of fuel decreases.  Going too fast in the atmosphere is also likely to lead to extra drag, which might have the effect of moving the centre of lift forward.  (A Mailsail sounds overpowered for the rest of your rocket, so unless you are throttling down, you are probably going too fast in the lower atmosphere).  All of this is reflects reals physics and is not a bug.

 

Edited September 10, 2018 by AVaughan

[Wallygator]

11 hours ago, Trekkie148 said:

Hey um KSP developer's um could you fix this glitch on whenever i build a rocket, it highly relies on rocket fin's being on the center of mass and when I do that, it looks very very ugly, and if I don't the rocket just flips for no darn reason but if I go to say for example version 1.4.2, 1.4.3 or even 1.4.4 that won't happen. Say for example I put together this very simple basic rocket containing of the mk1/3 command pod from the new update 1.4 with the big orange tank and a mainsail with a decoupoler for the pod to land safely in the kerbin ocean with none other than a parachute to coast it down safely. But the twist is or more or less "Bug" is what i'm calling it, in the latest update 1.4.5 if I launch a simple rocket with no fin's and I do know that the pods are lifting surfaces BTW, The rocket flips out of control even with reaction wheels and also I did not add reaction wheels to the rocket and I do know that they make stuff in KSP more stable well because KSP logic, I felt like not adding one and even with them the rocket still flips out of control and i've only concurred this event on none other than this update which is a pain in the @$$ because it's annoying to fix every time I try to build a darn rocket that flips for no apparent reason,

 

KSP developer's please fix this bug if you can and I do not have any log's or videos showing this and I am not lying to you for real, 

 

I have to add rocket fins inside of the darn fuel tank and it increases part count and my memory hates it! 

Oh also when I looked at the reentry particle effects with no mods installed, I do know that they added a new reentry effect in version 1.4 and when I go to 1.4.5 the effect goes to the old 1.3 one... can someone help me out here please?

A pic, or a share of the craft file along with the mods you are using is essential if you are expecting any kind of effective help. Otherwise people will typically ignore your request, or they will just tell you what I have just said.

Also, this might be better posted in a bug/help section rather than a response to an announcement.

That said, the current version is rather good from a physics perspective (all things considered), so my gut feeling is you are likely building a craft that unexpectedly exploits something - or you are are expecting something that is different from the reality that is currently programmed.  Share your craft file and mods and people might be able to help.

Edited September 10, 2018 by Wallygator

[EdwardB3020]

56 minutes ago, Wallygator said:

A pic, or a share of the craft file along with the mods you are using is essential if you are expecting any kind of effective help. Otherwise people will typically ignore your request, or they will just tell you what I have just said.

Also, this might be better posted in a bug/help section rather than a response to an announcement.

That said, the current version is rather good from a physics perspective (all things considered), so my gut feeling is you are likely building a craft that unexpectedly exploits something - or you are are expecting something that is different from the reality that is currently programmed.  Share your craft file and mods and people might be able to help.

Ok I can try to put something together on a google drive Link with a video, craft file, screenshot, and log files if I can after when my school work is done...

[Tyko]

1 hour ago, Trekkie148 said:

Ok I can try to put something together on a google drive Link with a video, craft file, screenshot, and log files if I can after when my school work is done...

A clear, well lit screen shot (like from the VAB) would probably do the trick. All the rest is likely unnecessary.

[EdwardB3020]

5 hours ago, Tyko said:

A clear, well lit screen shot (like from the VAB) would probably do the trick. All the rest is likely unnecessary.

https://drive.google.com/drive/folders/1CHFvE7QjNKZ-VGZrBYrZxBM1SGCWoRHZ?usp=sharing

 

This is the reentry glitch

Edited September 10, 2018 by Trekkie148

[Tyko]

You're flying with your rocket's nose too far off prograde. if your nose isn't pointed into the oncoming air the air pressure is going to try to flip the rocket sideways. The more off prograde you are, the greater the forces trying to flip you. Your engine gimbal and reaction wheels can counter a certain amount of that force, but if you go too far off prograde at too low an altitude and going too fast you'll flip.

This isn't a bug, you just need to tweak you're ascent to keep the rocket pointed more to prograde.

My advice would be to reduce your TWR. The 1.25m rocket is hitting close to 2.5 TWR right off the launch pad and gets up to 5 TWR by 12000m (look at the G meter to the right of the navball to see your TWR). That's a lot more than you need and it's contributing to your issue. If you launched with closer to 1.5 TWR you'd find that you'd be flipping less and wouldn't need to oversteer as much because gravity turn would pull your rocket over naturally... Use your throttle to keep the engines under control. If you're seeing red flames you're going too fast for your altitude

Edited September 10, 2018 by Tyko

[HebaruSan]

Some fins at the back wouldn't hurt, either.

[Tyko]

3 minutes ago, HebaruSan said:

Some fins at the back wouldn't hurt, either.

(out of likes today)  Yea, I was thinking about suggesting fins, but I thought a different ascent profile would be a better thing to try because the OP is going to face this same problem with every rocket built and flown that aggressively.

Edited September 10, 2018 by Tyko

[HebaruSan]

10 minutes ago, Tyko said:

(out of likes today)  Yea, I was thinking about suggesting fins, but I thought a different ascent profile would be a better thing to try because the OP is going to face this same problem with every rocket built and flown that aggressively.

I'd say it's a "pick at least two out of three" situation. Fix the TWR and the ascent profile, and indeed you might not need fins. Fix the ascent profile and add fins, and maybe the gargantuan TWR won't be an issue. Fix the TWR and add fins, and maybe the wacky ascent profile could be viable.

[Tyko]

56 minutes ago, HebaruSan said:

I'd say it's a "pick at least two out of three" situation. Fix the TWR and the ascent profile, and indeed you might not need fins. Fix the ascent profile and add fins, and maybe the gargantuan TWR won't be an issue. Fix the TWR and add fins, and maybe the wacky ascent profile could be viable.

Yea...I like that   

[AVaughan]

Personally for such a light load, I'd replace the Mainsail with a Skipper.  That is lighter and will fix the TWR.  I also suggested fins earlier, since I want my rockets to be aerodynamically stable.

[Vanamonde]

@Trekkie148, your question has been moved to its own thread. 

[Harry Rhodan]

On 9/10/2018 at 3:49 AM, Trekkie148 said:

Say for example I put together this very simple basic rocket containing of the mk1/3 command pod from the new update 1.4 with the big orange tank and a mainsail with a decoupoler for the pod to land safely in the kerbin ocean with none other than a parachute to coast it down safely.

So you have a tank, a 6t engine on the bottom end and a 3t pod on the other end. The golden rule says the heavy end will try to move to the front. To which end will the CoM go while you drain the tank?

Also using an extremely overpowered engine for a simple testing vehicle is also not the best idea. I mean you're pulling 6g's and more. That is hardly something that happens early in a regular launch.

[EdwardB3020]

I've figured out what happened it was a mod that affected it and I did not have FAR installed, it was something else that was a mod