Several questions related to aerodynamics....

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Julian

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I think i have mentioned this before, but I am working on a 38mm min-dia rocket that I want to fly to mach 2. I am using a modified blackhawk from wildman.

I know that many people have flown things very like this, but I would like to not ust fly this rocket for fun, but also do some aerodynamic research with it.

When i was doing research before o started building i was found that there was very little hard data for aerodynamic heating for rockets for this size.
I foremost want to measure the temperature of nose and fins at different points. I have some questions on how to do this....
My goals are these
1 measure at multiple points on the fins for temp. at at least 10 samples per second. question: is there a color changing paint based on heat that is possible to use, or is there some small digital thermocouple data logger
2 do the same with the nosecone.
3 See if a nose aerospike would be feasible and if it would really reduce drag fro something this small. Is this practical?

any ideas on how to do these things, and how to make them practical from a cost and size (38mm) perspective?

Thank you all

Julian
 
It is easy to measure temperatures, but determining what the temperatures represent is not. The design of the temperature sensor and instrumentation package and the interpretation of the data is what it's all about. If you don't know what you are trying to measure and the physics behind the measurement, you'll certainly measure "temperatures", but that's not research unless you can interpret the results.......

Bob
 
With respect to number three, an aerospike is only used where you have some other constraint on the shape of the missile. The most famous case being the Trident D-5. Its length is constrained by the hull diameter of the Ohio class submarine, which had already been set by the time the D-5 project started. The diameter was constrained by the launch tube diameter. To get the required range they needed a certain amount of propellant, this in turned pushed the ordnance package up, this made it impossible to get a decent Haack nose. Thus the aerospike. You never see aerospikes on pad launched missiles because they don't have the length constraint.

This paper, https://www.cs.odu.edu/~mln/ltrs-pdfs/aiaa-95-0737.pdf, shows some interesting data at Mach 6 but doesn't comment on whether the observed drag was higher or lower than an equivalent length Haack series.
 
With respect to number three, an aerospike is only used where you have some other constraint on the shape of the missile. The most famous case being the Trident D-5. Its length is constrained by the hull diameter of the Ohio class submarine, which had already been set by the time the D-5 project started. The diameter was constrained by the launch tube diameter. To get the required range they needed a certain amount of propellant, this in turned pushed the ordnance package up, this made it impossible to get a decent Haack nose. Thus the aerospike. You never see aerospikes on pad launched missiles because they don't have the length constraint.

This paper, https://www.cs.odu.edu/~mln/ltrs-pdfs/aiaa-95-0737.pdf, shows some interesting data at Mach 6 but doesn't comment on whether the observed drag was higher or lower than an equivalent length Haack series.
Actually the Trident I C4 was designed to fit into the 33' diameter James Madison and Benjamin Franklin class Poseidon missile subs as well as the 42' diameter Ohio-class boats with longer silos to accommodate the larger and more accurate Trident II D5 missiles. The aerospike concept appears to have been developed by the Navy in the early '70s with the first C4 missile launched in 1977 and deployed in 1979 prior to the commissioning of the first Ohio class subs. The D5 was developed in the '80s and deployed in 1990. The C4 was decommissioned in 2005, and the D5 is our current SLBM.

The paper you referenced was published in 1995 by NASA and the USAF more than 2 decades after the Navy developed the concept so I'm not sure what's new in it, however as the angle of attack of the Trident missile is near zero, so the paper may be going into new aerodynamic regimes. The missile aerospike significantly reduces the missile drag by effectively lengthening the missile and by shock heating the air behind it which reduces the density and increases the sound speed in the airflow around the nosecone, lowering the effective Mach number of the missile. As drag is proportional to Mach number squared, a little heating goes a long way in drag reduction.

Bob
 
OK, aerospikes can be forgotten. However what about heat measurement?

If you place 6 thermocouples a long the fin at various points and measure the temperature from lift off to apogee then cant one deduce that the resulting temperature spikes are from the heating?
Then If you fly at multiple speeds you can get a sense of what to expect for fins of this sise at, say mach 1.5 and 1.8 and mach 2. Correct?
 
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