Optimum nose design for mach 3...

Can anyone comment on what happens at these speeds to aerodynamics over the nose? I've been told that with a nose too long at speeds well over mach, more heat is generated than with an ogive shape due to shock wave formation. I'd like to get some input to decide whether the nose for the 6" rocket needs to be conical or ogive to withstand 15+ seconds at over mach 2. I may have it metal plated as well. Thanks,

look at the phoenix missile,, it's somewhat pointy but rounded as well to spread the heat over a larger area.

Yes, I'd go with something like the Phoenix

From what I know about aerodynamics, mach 5 is when heating becomes a big concern.

Von Kaarman is a popular shape for nosecones. I heard that it's pretty efficient for it's volume and surface area. It's got a slightly rounded tip but it long and sleek

look at aircraft and missiles designed to go that fast. FAS is a good place to see photos of them.

As far as performance, I understand that for supersonic flight, conical is more efficient than ogive. Ogive is usually cited as a good compromise between reasonable sub- and super-sonic performance, whilst also giving a large internal volume.

Playing with fast rockets in RocSim indicates that conical is the way to go, I haven't experimented with any of the more 'exotic' styles yet - mainly because they're not readily available.

On this subject, anyone know where to get a decent 2.6" conical nosecone from?

Originally posted by nialloswald
Playing with fast rockets in RocSim indicates that conical is the way to go, I haven't experimented with any of the more 'exotic' styles yet - mainly because they're not readily available.

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I'm no expert on optimal nose cone shapes, but here is an excerpt from Apogee Newsletter #75:

"... a lot of people will tell me that the
cone shape gives them the best performance in RockSim (that it has the lowest drag of all the shapes). Unfortunately, RockSim uses the DATCOM method, which is an semi-emperical method of computing drag that isn't specifically designed for this purpose.

The equation that governs the nose cone drag for the DATCOM
method (and hence, RockSim) is listed in the book: "Topics in
Advanced Model Rocketry."
If you look at chapter six, equation 166, you'll see that the
software calculates the Cd based on the "wetted surface area of
the body" and the "maximum cross-sectional area" of the body.
The shape of the nose really is ignored and only is taken into
account by the affect it has on the surface area of the nose.
Since the "cone" has the smallest surface area, the DATCOM
method predicts that it will have the lowest drag. The DATCOM
method gets us in the ballpark, and it is easy to calculate, but it is
not a perfect method."

ok, i read a whole bunch about this, and here is the best reference i have found. it even has a chart to shor which shapes are best for which speeds. conical nosecones are easy to make, that's why people use them, they are not very aerodynamic. you want a von-karman profile, and for something that big and fast, most likely carbon fiber, so you will probably need to get one custom made.

https://projetosulfos.if.sc.usp.br/artigos/NoseCone_EQN2.PDF

So bi-conic is what I'm looking for? How do I figure the correct cone angles for these speeds? I've been speaking with Jon at Soller composites, I'm having a custom fincan and a custom nosecone built. We are trying to figure out if a 500-600 degree hi temp epoxy will be needed over the standard stuff, my guess is yes. What would you guys say? Anyone know just how hot this might get?

I know you are talking about speeds of Mach 3, but have you calculated everything to know if you will be going that fast, and Max Q at those speeds? Seems like you would want to know those parameters first so that then you can design your rocket to them.

Edward

Originally posted by cjl
I'd go with something like the Phoenix

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Yes, the AIM-54 can go fast and has a suitable nose shape. No, it is not necessarily the optimum shape for going fast.

Keep in mind that the Phoenix also carries a large internal radar antenna. Since the missile nose is actually a radome, through which the radar must be able to 'see,' there are constraints on the shape of the nose to control and avoid internal signal reflections that interfere with radar performance.

Purely conical nose cones are reasonably good designs and probably offer the most simple aerodynamic analysis for supersonic flight----if there is no requirement to install anything of significant size inside the nose. Check out the shapes of sounding rockets and you will see some conics (WAC Corporal, others), some ogives (Black Brant VI, others), and many other shapes.

What you are primarily seeking is a reasonably efficient shape to get through the supersonic drag rise that typically occurs from about Mach 0.9 to 1.2. That shape should be something quite pointy and slender. Also, don't overlook that your overall vehicle finess ratio (body length to diameter) should be 10 to 12 or higher.

I can't tell you where I read it, I read so much but a 5-to 1 ratio conical worked out to be the best. Mr. Wickman at CP Technologies can turn you one as well as BMS or I understand that Sandman makes nosecones.

Perhaps this thread might help.

https://www.aerospaceweb.org/question/aerodynamics/q0151.shtml


heres a little blurb from the page

The faster the vehicle is designed to go, the more pointed the ideal aerodynamic nose shape becomes. Compare the nose of the Mach 2 F-15 with that of the Mach 5 Phoenix air-to-air missile shown below. The limitation on nose shape is temperature. At very high Mach numbers, the nose must become more rounded than the ideal low-drag shape in order to spread the high temperatures over a larger area and prevent the nose from melting.

Ya. 5:1 conical is best for those speeds. Performance rocketry has one and can make it carbon fiber if you need it.

Curious what motor you plan on using and more details on the design and materials used.

GL.....Bill

Actually, it even states in that article linked earlier that the tests were for transonic speeds (the ones that reccomend the Von Karmon), and a conical is the best once the rocket is smoothly supersonic, esp. at above Mach 3

Originally posted by Monte SS
Ya. 5:1 conical is best for those speeds. Performance rocketry has one and can make it carbon fiber if you need it.

Curious what motor you plan on using and more details on the design and materials used.

GL.....Bill

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Yes, the conical shape produces a lower drag coefficient at those speeds (mach 2 and beyond). However it all comes down to materials available to determine which nose design would be most appropriate in this situation. If metals can be used or such which would permit a heat rise to extreme levels, it would be safe to use a fairly long 5:1/6:1 etc conical design, as drag from one will in fact be lower at these speeds (due to the shock angle from what I have recently understood). But realize when carbon fiber is used, the carbon itself can support the very high temperatures yes, the epoxy it is laminated with may however not. Therefore, I feel this sort of makes an epoxied-carbon setup less than an optimal material for the nose of such a project (keep in mind the time period the rocket will endure velocities above mach 2). So I've begun a search for another possible lightweight material able to remain structurally safe at high temps, and I've come to the conclusion that a carbon-carbon turned and hollowed nose may be the best way to go. I haven't really looked into who could do such a thing yet, so I don't know if this could be done that easily.

Do you have unlimited budget on this thing? Reinforced Carbon-Carbon costs THOUSANDS of dollars per pound (MANY thousands of dollars). CF should be fine - there won't be that much heating if you're only at speed for 15 seconds (this is the insane P motor project, right). I would just go for CF (and you NEED vent holes). Over just 15 seconds at only Mach 2 -3, you shouldn't hit more than 200-300 degrees at the nose tip.

Frank Kosdon's Full Metal Jacket rockets used graphite nosecones, easely avalable at a much lower cost that carbon-carbon and it has the benefit of if you get out of rocketry you can always use the rocket as a giant pencil.

Originally posted by Focal
ok, i read a whole bunch about this, and here is the best reference i have found. it even has a chart to shor which shapes are best for which speeds. conical nosecones are easy to make, that's why people use them, they are not very aerodynamic. you want a von-karman profile, and for something that big and fast, most likely carbon fiber, so you will probably need to get one custom made.

https://projetosulfos.if.sc.usp.br/artigos/NoseCone_EQN2.PDF

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woof, it really amazes me how much that pdf gets around. guess I ought to get around to finishing it someday.

GC

Yikes, I never realized the cost of carbon-carbon. Looks like I'll stay away from that. My budget for this is definitely not unlimited, I just want to build it however for the P motor as it is my goal to someday produce the motor and fly it. I realize the expense of the propellant alone for a P motor, and it gets quite scary. I figured temps would be much hotter than 200-300 degrees on the nose tip, but if that is the case I can get by with a high temp rated epoxy and carbon nose. But one thing does come to mind, would the 200-300 degrees be an estimated amount for a Von Karman type of cone which spreads heat, or a conical design which would focus heat? I feel a conical design will be used, so that must be taken into account. As far as nose aspect ratio, I have no idea if a 6:1 would be much more beneficial aerodynamically than a 5:1 in this case, knowing that the 6:1 will suffer more at the tip.

Originally posted by pr_rocket04
Can anyone comment on what happens at these speeds to aerodynamics over the nose? I've been told that with a nose too long at speeds well over mach, more heat is generated than with an ogive shape due to shock wave formation. I'd like to get some input to decide whether the nose for the 6" rocket needs to be conical or ogive to withstand 15+ seconds at over mach 2. I may have it metal plated as well. Thanks,

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Attached is a page from a good paper by Gary Crowell on the topic as it pertains to HPR. It includes a drag table based on NACA data. The full paper is too large to attach here but a search should turn it up. THE DESCRIPTIVE GEOMETRY OF NOSE CONES. 1996 Gary A. Crowell Sr.

Remember also that depending on the mission profile, trades such as mass versus drag are often taken into account. Orbital vehicles will generally trade drag for mass so you often see conical and bi-conic examples employed. The opposite is the general rule in sounding rocket applications.

Anthony J. Cesaroni
President/CEO
Cesaroni Technology/Cesaroni Aerospace
https://www.cesaronitech.com/
(905) 887-2370 x222 Toronto
(941) 360-3100 x101 Sarasota
(410) 571-8292 Annapolis

Excellent. Thank you.

You could consider a graphite tip that is attached with high temp epoxy.

While you are considering an optimum nosecone, have you optimized the whole airframe. Would seem silly to me to have a perfect nosecone and then leave everything else.


Edward

Originally posted by edwardw
While you are considering an optimum nosecone, have you optimized the whole airframe. Would seem silly to me to have a perfect nosecone and then leave everything else.


Edward

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By that do you mean airframe length, or structural design? I am mainly working on nose and fincan design currently for aerodynamics/structure, which I am then building as a 4" diameter prototype (for an N2000w). I do have the airframe layup planned for the prototype 4 incher however. It will use a base layer of 3" 700ts aerospace grade 22.2oz woven carbon sleeve, a 4" 640ts 10.6oz carbon sleeve middle layer, and a top layer of 4" 640ts 15.1oz carbon top layer. This will hopefully take care of the massive amounts of shear force on the rocket (it's long in my opinion). I will then calculate needed strength and layers for a 6" inch diameter, and if all goes well, upscale. I can then be assured the very expensive design will perform as hopefully expected.

I mean overall aerodynamic design. You want something with the least drag. Airfoiled fins, smooth lines, glass like finish. Tower launched.

Edward

Originally posted by edwardw
I mean overall aerodynamic design. You want something with the least drag. Airfoiled fins, smooth lines, glass like finish. Tower launched.

Edward

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Yes, those aspects are all being looked at very closely.

I posted the equations for HAACK series noses in the tech forum a couple months ago. Those are pretty good for supersonic flights as they are designed to make the least ammount of transonic drag. I'd focus more on transonic drag since that's where most of the flight will take place (unless your building something really crazy). Without expensive CFD software or access to a high speed wind tunnel I don't think anyone on this forum could tell you exactly what the best shape is.

True - you will probably only spend 5 seconds or so COMPLETELY smoothly supersoni - most of the time will be transonic, so look at the VK and Haack noses as well.