Rocket stability(center of mass)

[cjl]

UGHHH.. makes the a-12 right by it look like a match box... (not that i am be littling...)

It might be bigger than the A-12, but the A-12 wins for elegance and design

(The blackbird is probably my favorite airplane though, so I could be biased...)

 

[cjl]

yes, but if you stall you are not stable...

Umm...

Duh.

This would only matter if airplanes were routinely flown while stalled. What matters is the flight characteristics at just ABOVE stall speed, not just below.

(And, to be pendantic, there are some airplanes which stall in a stable fashion, such that the stall is self-correcting)

 

[ClayD]

Umm...

Duh.

This would only matter if airplanes were routinely flown while stalled. What matters is the flight characteristics at just ABOVE stall speed, not just below.

(And, to be pendantic, there are some airplanes which stall in a stable fashion, such that the stall is self-correcting)

the a12 doesnt fit in that category....

 

[new2hpr]

Like they say about the greased pig....

Squeal Boy!!!:y::no:

 

[cjl]

the a12 doesnt fit in that category....

The category of airplanes which are self-correcting from a stall? No. Interestingly enough, the A-12 actually was very difficult to stall. A highly-swept delta is very stall resistant. However, they have some interesting high-alpha characteristics. The A-12 would become unstable in pitch before it would stall because of this.

And, once again, it has nothing to do with wingtip vortices. Also, I don't see how you think the A-12 fits into any of this, since it has fixed wingtips which are in the same plane as the rest of the wing.

 

[new2hpr]

Now then, can we just go build some rockets with straight fins, so none of this matters? Not that it does.

-Ken

 

[ClayD]

And rather pointlessly.

I could help someone who is getting his information off the backs of cereal boxes (or wherever), but if they refuse to listen and learn, we are just wasting our time (and amusing everyone else).

Like they say about the greased pig....

i like pig, it is delicious..

i think you are wasting your time, which is why CJL and others dedicate to this.. its self fulfilling egos... Frankly, i have nothing better to do at the moment. you at post 70ish were stuck on my post 51.. so at indifference of oppinion arent teaching me anything.
You have worked tirelessly, and or paid lots of money, to find yourself arguing over the internet... we all see the futility, But, you can let it go...
who's the one that needs learnded....
theres an engineering principal, of "i am an engineer, if your not an engineer you cant say i am wrong cause you cant prove it."
I see this DAY IN AND DAY OUT... promlem is, when an engineer is wrong, everyone knows it...

 

[ClayD]

The category of airplanes which are self-correcting from a stall? No. Interestingly enough, the A-12 actually was very difficult to stall. A highly-swept delta is very stall resistant. However, they have some interesting high-alpha characteristics. The A-12 would become unstable in pitch before it would stall because of this.

And, once again, it has nothing to do with wingtip vortices. Also, I don't see how you think the A-12 fits into any of this, since it has fixed wingtips which are in the same plane as the rest of the wing.

the wintips have drop... later versions this is removed. previous versions did this to enhance low speed.

Yes, but they were prone to spin/stall.. engine out.. one of the best pilot reads ive ever read was from SR-71 extended CP test, that flame out decentigrated his plane...they lost several this way...
this led to developments in the XB-70 and in turn modeled into the B1.

 

[cjl]

i like pig, it is delicious..

i think you are wasting your time, which is why CJL and others dedicate to this.. its self fulfilling egos... Frankly, i have nothing better to do at the moment. you at post 70ish were stuck on my post 51.. so at indifference of oppinion arent teaching me anything

You have worked tirelessly, and or paid lots of money, to find yourself arguing over the internet... we all see the futility, But, you can let it go...
who's the one that needs learnded....
theres an engineering principal, of "i am an engineer, if your not an engineer you cant say i am wrong cause you cant prove it."
I see this DAY IN AND DAY OUT... promlem is, when an engineer is wrong, everyone knows it...

The problem with this is that I'm not saying that I'm right because I'm an engineer (or, more accurately, an engineering graduate student). I'm saying I'm right because I have evidence and math to support my position. Everything I have said is fairly standard basic aerodynamics, and a quick perusal of an undergraduate aerodynamics textbook will show that I (and Powderburner) am correct.

As for your statement that "when an engineer is wrong, everyone knows it"? Why is it then that everyone here but you knows that you are wrong? You seem to overestimate your own knowledge significantly. You might want to look up the Dunning-Kruger effect...

 

[cjl]

the wintips have drop... later versions this is removed. previous versions did this to enhance low speed.

Yes, but they were prone to spin/stall.. engine out.. one of the best pilot reads ive ever read was from SR-71 extended CP test, that flame out decentigrated his plane...they lost several this way...
this led to developments in the XB-70 and in turn modeled into the B1.

None of the A-12 wingtips ever had any droop. I've attached an image of the first A-12 in final assembly. Also, the A-12 was never prone to stalls, and it never really had a problem with spins either. It did have a problem with the engines for a while, but they reprogrammed the inlet spikes and changed the way that the spikes reacted to in-flight events and fixed that.

Also, the XB-70 was developed mostly independent of the SR-71, and the SR-71 had significantly better performance than the XB-70 (which is why the Air Force chose the SR-71, which was a modified A-12, rather than a reconnaissance version of the XB-70).

Finally, the B-1 is a separate airplane, and again, one without any wingtip droop. It does have variable sweep wings, but that's a completely different design feature, added in for a completely different reason.

 

[new2hpr]

You might want to look up the Dunning-Kruger effect...

Ouch!

 

[ClayD]

The problem with this is that I'm not saying that I'm right because I'm an engineer (or, more accurately, an engineering graduate student). I'm saying I'm right because I have evidence and math to support my position. Everything I have said is fairly standard basic aerodynamics, and a quick perusal of an undergraduate aerodynamics textbook will show that I (and Powderburner) am correct.

As for your statement that "when an engineer is wrong, everyone knows it"? Why is it then that everyone here but you knows that you are wrong? You seem to overestimate your own knowledge significantly. You might want to look up the Dunning-Kruger effect...

soo, is this thread to reverse your end of the effect... build up your confidence in the knowlege you have so you dont feel underatted.
CITE YOUR LINK HERE...
while the highly skilled underrate their abilities, suffering from illusory inferiority.

 

[ClayD]

None of the A-12 wingtips ever had any droop. I've attached an image of the first A-12 in final assembly. Also, the A-12 was never prone to stalls, and it never really had a problem with spins either. It did have a problem with the engines for a while, but they reprogrammed the inlet spikes and changed the way that the spikes reacted to in-flight events and fixed that.

Also, the XB-70 was developed mostly independent of the SR-71, and the SR-71 had significantly better performance than the XB-70 (which is why the Air Force chose the SR-71, which was a modified A-12, rather than a reconnaissance version of the XB-70).

Finally, the B-1 is a separate airplane, and again, one without any wingtip droop. It does have variable sweep wings, but that's a completely different design feature, added in for a completely different reason.

the 3 are completely different generations of aircraft, and A-12 has wingtip drop! i have seen it in person.

 

[cjl]

the 3 are completely different generations of aircraft, and A-12 has wingtip drop! i have seen it in person.

Nope. Here are the four types of blackbird:

The first image in the attachments is an A-12, specifically, the first. This was before they painted it. The second image shows a side view of the first YF-12. The third image shows an SR-71 in a high bank. The final image shows an M21 with D21 attached. This covers all 4 types of blackbird. None of them have wingtip droop, as clearly seen in the photos.

 

[powderburner]

hey, cjl,

You're gettin that greasy mess all over you too!

 

[cobra1336]

Amazing, a new member asks a somewhat simple question and it turns into a 134 post

 

[jsdemar]

theres an engineering principal, of "i am an engineer, if your not an engineer you cant say i am wrong cause you cant prove it."
I see this DAY IN AND DAY OUT... promlem is, when an engineer is wrong, everyone knows it...

Have you sought professional help for your compulsive inferiority issues? You'd probably just tell the therapist you already know more about psychology than they do. And their high-falootin' skoolin' was a waste of time.

 

[georgegassaway]

ClayD wrote to Powderburner:

You have worked tirelessly, and or paid lots of money, to find yourself arguing over the internet... we all see the futility, But, you can let it go...
who's the one that needs learnded....
theres an engineering principal, of "i am an engineer, if your not an engineer you cant say i am wrong cause you cant prove it."

Usually, typos and misspellings are left alone in forums (I sure make my share of typos) . But there are so many in that last sentence and a half, and the thread is supposed to be about technical matters which require a greater level of accuracy, where bad spelling and bad grammar are like fingernails scraping across a chalkboard.

>>>>>
....who's the one that needs learnded....
<<<<

Learnded? What is learnded? That whole part of the sentence does not make any sense.

>>>
.....theres .....
<<<

There is, or “there’s, not “theres”. You need to work on your use of contractions as this error is common throughout your posts.
https://www.enchantedlearning.com/grammar/contractions/

>>>
....an engineering principal, ...
<<<

Engineering PRINCIPLE, not principal.

>>>>
....of "i am an engineer, ...
<<<

The word “I” (meaning the person who is speaking/writing) is always capitalized, not used as lower-case.

>>>
if your not an engineer....
<<<

“You’re”, not your. As in “you are”, used as the contraction “you’re”. The word “your” is used as a possessive, which does not apply in this case.

>>>
... you cant say...
<<<
The word is “can’t”, not cant. As in “can not”, or “cannot”, used as the contraction “can’t”. There is no such thing as “can not” or “cannot” used as a contraction spelled as “cant”.

>>>>
... i am wrong .....
<<<<

Again, the word “I” (meaning the person who is speaking/writing) is always capitalized, not used as lower-case.

>>>
...cause ...
<<<

BECAUSE, not cause.

Why? Because...

>>>
...you cant prove it."
<<<

Again, the word is “can’t”, not cant. As in “can not”, or “cannot”, used as the contraction “can’t”. There is no such thing as “can not” or “cannot” used as a contraction spelled as “cant”.

As I said at the start, normally spelling and typos are left alone in forums. But it is so hard to ignore in this case since your technical issues and terms used are about as inaccurate or mis-applied as the misspellings and improper use of words or grammar. Examples such as base drag, wingtip vortices, and total confusion over what the XB-70’s aerodynamics were about.

Take this as a “learnded oppertoonidty”.

BTW - Powderburner's reference to a pig, perhaps he meant the one about not trying to teach a pig to sing? The most appropriate pig reference to this thread is the one in the first photo below. I also repost the Inigo Montoya quote.

- George Gassaway

 

[MaxPayne]

You guys confused the hell out of me.

I second that cobra1336.

 

[ClayD]

ClayD wrote to Powderburner:

Usually, typos and misspellings are left alone in forums (I sure make my share of typos) . But there are so many in that last sentence and a half, and the thread is supposed to be about technical matters which require a greater level of accuracy, where bad spelling and bad grammar are like fingernails scraping across a chalkboard.

>>>>>
....who's the one that needs learnded....
<<<<

Learnded? What is learnded? That whole part of the sentence does not make any sense.

>>>
.....theres .....
<<<

There is, or “there’s, not “theres”. You need to work on your use of contractions as this error is common throughout your posts.
https://www.enchantedlearning.com/grammar/contractions/

>>>
....an engineering principal, ...
<<<

Engineering PRINCIPLE, not principal.

>>>>
....of "i am an engineer, ...
<<<

The word “I” (meaning the person who is speaking/writing) is always capitalized, not used as lower-case.

>>>
if your not an engineer....
<<<

“You’re”, not your. As in “you are”, used as the contraction “you’re”. The word “your” is used as a possessive, which does not apply in this case.

>>>
... you cant say...
<<<
The word is “can’t”, not cant. As in “can not”, or “cannot”, used as the contraction “can’t”. There is no such thing as “can not” or “cannot” used as a contraction spelled as “cant”.

>>>>
... i am wrong .....
<<<<

Again, the word “I” (meaning the person who is speaking/writing) is always capitalized, not used as lower-case.

>>>
...cause ...
<<<

BECAUSE, not cause.

Why? Because...

>>>
...you cant prove it."
<<<

Again, the word is “can’t”, not cant. As in “can not”, or “cannot”, used as the contraction “can’t”. There is no such thing as “can not” or “cannot” used as a contraction spelled as “cant”.

As I said at the start, normally spelling and typos are left alone in forums. But it is so hard to ignore in this case since your technical issues and terms used are about as inaccurate or mis-applied as the misspellings and improper use of words or grammar. Examples such as base drag, wingtip vortices, and total confusion over what the XB-70’s aerodynamics were about.

Take this as a “learnded oppertoonidty”.

BTW - Powderburner's reference to a pig, perhaps he meant the one about not trying to teach a pig to sing? The most appropriate pig reference to this thread is the one in the first photo below. I also repost the Inigo Montoya quote.

- George Gassaway

To think I paid a couple grand and got "a"'s in my engrish classes for something I i could have learnded here for free. THANks --years ago...

You might as well just save your time, and say "I don't agree, shut up stupid"; leave it at that.

The reason this post is so vast, is most of the guys feel so inferior that others dont agree with them. They have to feel proved at face value. They cant'' walk away feeling like someone didn't acknowlege thier alknowing accurate non-exeplified commenting.

I have great confidence(yes) in my experiences, I am well aware of my shortcomings and limitiations.

Can I nick name you "dick." how would you feel if you said that to a dyslexic to thier face.

 

[bytesiz]

Too bad this thread has turned to name calling... if you sift thru the banter, there is actually some good info in here.

How about you all take a breath and see if you can turn this back into a discussion? Some of us beginners might be able to learn something.

 

[ClayD]

Too bad this thread has turned to name calling... if you sift thru the banter, there is actually some good info in here.

How about you all take a breath and see if you can turn this back into a discussion? Some of us beginners might be able to learn something.

That is what TRF is about. - learning stuff and being able to openly discuss things. you have a lot of patients to make it that far through.

A good example of drag induced "static" stabilizing, is oddrocs, will tie things to the outside of the fins, and drag them behind the plume creating drag far behind the rocket.

To add drag to limit ceiling of a rocket, some use deflection plates on the bottom of the rocket and finss to increase uhhhh... Base drag..
This was done at LDRS 29, on the Gates brothers summo. if you go check out the discovery channel video, you can see it.

 

[jsdemar]

That is what TRF is about. - learning stuff and being able to openly discuss things. you have a lot of patients to make it that far through.

You give yourself too much credit! You're one of our best "patients".

Without the self-declared idiot's misinformation and the corrections thereof, the thread would be shorter. And more educational to beginners. A prime example of a troll in action.

A good example of drag induced "static" stabilizing, is oddrocs, will tie things to the outside of the fins, and drag them behind the plume creating drag far behind the rocket.

More nonesense, throwing around words at random because they sound good to you, but are incorrect. "Static" means non-moving. Something that doesn't move can't induce drag.

To add drag to limit ceiling of a rocket, some use deflection plates on the bottom of the rocket and finss to increase uhhhh... Base drag..

:no:
To give you the child-like attention you crave, I'll correct you one more time. Base drag is due to the vacuum affect at the base of the rocket. It is less when the motor is burning because the exhaust gases fill the void. After burnout, the drag increases as the flow separates beneath the base of the rocket. It also affects the dynamic stability of the rocket.

Adding draggy elements to a rocket to move it's CP rearward is not "base drag". It is simply "shape drag".

 

[ClayD]

:no:
To give you the child-like attention you crave, I'll correct you one more time. Base drag is due to the vacuum affect at the base of the rocket. It is less when the motor is burning because the exhaust gases fill the void. After burnout, the drag increases as the flow separates beneath the base of the rocket. It also affects the dynamic stability of the rocket.

Adding draggy elements to a rocket to move it's CP rearward is not "base drag". It is simply "shape drag".

what did that big acrylic plate doo on the bottom of the rocket, you dont think it chanded the base drag, that is stupid. and i dont agree...

 

[ClayD]

what did that big acrylic plate doo on the bottom of the rocket, you dont think it chanded the base drag, that is stupid. and i dont agree...

because....... when motor burnout happened...... it drag separated the nose cone....... why...... Base drag......
thanks for paying attention to me tho....

 

[jsdemar]

what did that big acrylic plate doo on the bottom of the rocket, you dont think it chanded the base drag, that is stupid. and i dont agree...

I wasn't reponding to that one particular random example of where you were partially correct.

Even a blind pig finds the feed bin once in a while.

 

[jsdemar]

because....... when motor burnout happened...... it drag separated the nose cone....... why...... Base drag......
thanks for paying attention to me tho....

Nope. It is shape drag. Base drag is defined as the vacuum cavitation beyond the transition from the body to the base of the rocket. Anything added before that to stick out beyond the body diameter is shape drag. By increasing the base diameter with these shape drag elements, you are also adding a small amount of additional base drag because of the increased base diameter. But most of the increased drag due to the rear plate is shape drag.

 

[ClayD]

Nope. It is shape drag. Base drag is defined as the vacuum cavitation beyond the transition from the body to the base of the rocket. Anything added before that to stick out beyond the body diameter is shape drag. By increasing the base diameter with these shape drag elements, you are also adding a small amount of additional base drag because of the increased base diameter. But most of the increased drag due to the rear plate is shape drag.

I would say that if MECO was such a significant change to drag separate a rocket that was proven to work with other configurations, less shape draggy profiles. shows it increased base drag, a little or a lot is no matter, IT DID.

 

[AstronMike]

We are trying to help you understand these aerodynamic concepts to help you understand a bit more of proper rocket design, .

*I'm* trying to follow all of this rather closely to assist myself in better *large rocket-powered glider* design!

The deal about the wing tip voritices is good info. If those are creating so much drag on a non-tipped wing, then wouldnt all that excess drag actually lead to increased chance of fluttering? Such 'drag production', since it would be occurring at the *furthest* portion of the wing, would have a larger moment arm effect and thereby help induce/worsen fluttering, wouldnt it?

Good time you guys are bringing this up! I have a strange looking cranked delta planform, with tip plates, that I intend to fly in a few days on a mid I motor. Wingtipwise, its very solid feeling, compared to the 'standard' deltas I have made over the years for HPR gliders. Its a larger version of what I'm posting below......

Will be following this discussion very closely although I may not have anything to add 'education-wise', only anecdotal in-field experience via large nonstandard gliders and thier behaviors.

 

[cjl]

Nope. It is shape drag. Base drag is defined as the vacuum cavitation beyond the transition from the body to the base of the rocket. Anything added before that to stick out beyond the body diameter is shape drag. By increasing the base diameter with these shape drag elements, you are also adding a small amount of additional base drag because of the increased base diameter. But most of the increased drag due to the rear plate is shape drag.

To be fair to Clay, the sumo example was indeed base drag. It did involve flow separation at the base of the rocket, which both stabilized and added a tremendous amount of drag to the rocket. It also added some form drag due to the air hitting the front of the plates, but without running some CFD, I couldn't say whether the increased base drag or form drag is more significant.

Also, I'm not sure that I would describe base drag as having anything to do with cavitation - cavitation involves a phase change of the fluid flowing around the object, and that doesn't occur in rockets.