Vent holes in nosecone

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My opinion is the shoulder is not an optimum location as it can be below where flow can separate. A location on a converging surface may be better.
It's quite counterintuitive, but it's definitely something worthy of more investigation. This is the first time I've heard about locating it *on* the actual nosecone.

TP
 
Well, not everyone has access to the latest FEA and CFD tools to challenge such tales the "easy" way :)

But Scott, what I'm still missing is your primary rationale for placing the vent holes there in your project: was it all settled theoretically in the early design phase or was it a constraint of the layout for a record breaking configuration and receiving the barometric logged profile (w/o transonic spike) post flight was just a pleasant (unexpected) surprise? Is this common practice or at least with multiple precedents? Apologies for my ignorance with much of this aero stuff.

BTW: that was a superb construction.

TP
 
The tribal knowledge and wive’s tales haven’t kept up with the technology.
My experience with nosecone mounted alts and static ports is not..."tribal"...been there done that using a Missleworks RRC3 Extreme, in all three cases where I have used it in a nosecone application the data has not been nearly as pretty as Johns was, even Johns looked like it wasn't exactly smooth. Yes the events happened at the proper times, but pressure curve was pretty messy. I will post the files if I can find them.
 
My experience with nosecone mounted alts and static ports is not..."tribal"...been there done that using a Missleworks RRC3 Extreme, in all three cases where I have used it in a nosecone application the data has not been nearly as pretty as Johns was, even Johns looked like it wasn't exactly smooth. Yes the events happened at the proper times, but pressure curve was pretty messy. I will post the files if I can find them.

Some probably tolerate it better than others. They might even smooth the data to make it more representative of what actually happened. Ravens and Marsas are the only flight computers I’ve mounted like this, so maybe my samples are seriously influencing my opinion. 😬

I’m going to fly an RRC2L in the nose at our October launch. I’ll be interested to see how it looks.

So let me ask this-

why the requirement for “pretty” baro data during the boost?

Other than pouring over data after the flight, why is this important? It’s actually more fun to look at when it’s got some burbles and bobbles so you can try and deduce why.

Well, not everyone has access to the latest FEA and CFD tools to challenge such tales the "easy" way :)

But Scott, what I'm still missing is your primary rationale for placing the vent holes there in your project: was it all settled theoretically in the early design phase or was it a ..

BTW: that was a superb construction.

TP

The rationale was strictly space-savings. I wanted the shortest possible rocket and no airframe tubes. Organizing it in the order I did helped.

and thanks! 😊
 
From viewing high speed tests MANY years ago. There is definitely strange and erratic pressure transients at mach transition that can do very real things to objects like rockets.
But there is a BIG difference between "punching thru" mach transition on the way to mach2 or mach3 etc. (or) a flight profile that "just makes" it to mach1 and spends a long time in transonic region.
 
I flew a 38mm MD on a pretty good sized J a few years back, with an Eggtimer TRS in the nose, vents in the shoulder. Deployments were normal, the baro data was a little noisy but good, and both the sim and the data suggested that it exceeded Mach by a comfortable margin. If data accuracy is what you're looking for, yes, by all means find another place for the altimeter and the vents, if you're more concerned with getting the laundry out then shoulder vents are fine. BTW, all the HED Wildman kits have their AV bays and vents essentially in the NC shoulder... and I haven't heard of any reports of deployment issues with them.
 
Some probably tolerate it better than others. They might even smooth the data to make it more representative of what actually happened. Ravens and Marsas are the only flight computers I’ve mounted like this, so maybe my samples are seriously influencing my opinion. 😬

I’m going to fly an RRC2L in the nose at our October launch. I’ll be interested to see how it looks.

So let me ask this-

why the requirement for “pretty” baro data during the boost?

Other than pouring over data after the flight, why is this important? It’s actually more fun to look at when it’s got some burbles and bobbles so you can try and deduce why.



The rationale was strictly space-savings. I wanted the shortest possible rocket and no airframe tubes. Organizing it in the order I did helped.

and thanks! 😊
I have zero requirement on nosecone mounted altimeter for pretty data plots, as long as the alt does what its supposed to when its supposed to thats whats important, since I learned that a normally non-recording altimeter (like a Quark) will do the same job and be smaller they now fill that location. Not everyone is me though.
 
Altimeter baro filteri
Some probably tolerate it better than others. They might even smooth the data to make it more representative of what actually happened. Ravens and Marsas are the only flight computers I’ve mounted like this, so maybe my samples are seriously influencing my opinion. 😬

I’m going to fly an RRC2L in the nose at our October launch. I’ll be interested to see how it looks.

So let me ask this-

why the requirement for “pretty” baro data during the boost?

Other than pouring over data after the flight, why is this important? It’s actually more fun to look at when it’s got some burbles and bobbles so you can try and deduce why.



The rationale was strictly space-savings. I wanted the shortest possible rocket and no airframe tubes. Organizing it in the order I did helped.

and thanks! 😊
Baro filtering. Yes Marsa's filter the baro altitude data, because in a rocket altitude shouldn't oscillate. If it does then there are other issues beyond baro altitude accuracy. Fluctuating baro pressure != Fluctuating altitude. So best practice is to filter the lie out
 
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