An "R"-powered rocket build

madcow rocketry
SilicdyneTRF
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I left my laptop running overnight and while I was at work a couple weeks ago with a quadrant section of your nosecone in M2.2 airflow
My laptop isn't made for rendering that kind of data so it's been slow going processing the results. I'll try and get a good picture sometime this weekend

Initial runs indicate a tiny portion of 500-800F at the very tip of the nosecone (ie, not even beyond the 1/4" blunted portion) with 200-250F temperatures along the shock. Your Mach number is still low so the shock doesn't hug the nose very far (high air temperatures further from surface > less heat transfer).

Considerations:
-Heat transfer isn't instantaneous. It takes time for the substrate (your rocket) to raise in temperature)
-Your flight profile so far indicates you'll be in that flight regime for a very short time
 
Nytrunner said:
I left my laptop running overnight and while I was at work a couple weeks ago with a quadrant section of your nosecone in M2.2 airflow
My laptop isn't made for rendering that kind of data so it's been slow going processing the results. I'll try and get a good picture sometime this weekend

Initial runs indicate a tiny portion of 500-800F at the very tip of the nosecone (ie, not even beyond the 1/4" blunted portion) with 200-250F temperatures along the shock. Your Mach number is still low so the shock doesn't hug the nose very far (high air temperatures further from surface > less heat transfer).

Considerations:
-Heat transfer isn't instantaneous. It takes time for the substrate (your rocket) to raise in temperature)
-Your flight profile so far indicates you'll be in that flight regime for a very short time
Click to expand...

Excellent analysis and information . . . Chuck is planning a nominal 4" long machined aluminum tip and this suggests that he will be fine in doing so.

"You, sir, are a Steely-Eyed Missile Man" !

Dave F.


hurler-5.jpg
 
Nytrunner said:
I left my laptop running overnight and while I was at work a couple weeks ago with a quadrant section of your nosecone in M2.2 airflow
My laptop isn't made for rendering that kind of data so it's been slow going processing the results. I'll try and get a good picture sometime this weekend

Initial runs indicate a tiny portion of 500-800F at the very tip of the nosecone (ie, not even beyond the 1/4" blunted portion) with 200-250F temperatures along the shock. Your Mach number is still low so the shock doesn't hug the nose very far (high air temperatures further from surface > less heat transfer).

Considerations:
-Heat transfer isn't instantaneous. It takes time for the substrate (your rocket) to raise in temperature)
-Your flight profile so far indicates you'll be in that flight regime for a very short time
Click to expand...

Many think they need a sharp point made of metal on their nosecone. I’d be curious to know the difference if it had a 3/16 inch radius instead of a point.
 
Steve Shannon said:
Many think they need a sharp point made of metal on their nosecone. I’d be curious to know the difference if it had a 3/16 inch radius instead of a point.
Click to expand...

That quadrant model has a quarter inch diameter blunt tip. Is that close enough?

I could do the full point next, provided I have another 24 hours to let my laptop' do nothing else :D
 
Rail Dawg said:
They're called "Bay Switches" from SMT Designs. This pic below shows better detail.

Chuck C.
Click to expand...

Chuck,

I can see how it would activate the switch, as the bolt is screwed in, but how does it de-activate it if, for example, the "UpChuckR" had to be lowered, worked on, or removed from the rail, after arming ?

Dave F.


hurler-5.jpg
 
Ez2cDave said:
Chuck,

I can see how it would activate the switch, as the bolt is screwed in, but how does it de-activate it if, for example, the "UpChuckR" had to be lowered, worked on, or removed from the rail, after arming ?

Dave F.


View attachment 381119
Click to expand...


Good question Dave. Unscrewing the bolt causes the spring in the switch to move to the "off" position.

Chuck C.
 
Nytrunner said:
That quadrant model has a quarter inch diameter blunt tip. Is that close enough?

I could do the full point next, provided I have another 24 hours to let my laptop' do nothing else :D
Click to expand...

Only if you find the time. My understanding is that the sharper the tip, the greater the thermal concentration. Would it be faster if you just did the top six inches of the nosecone and maybe a smaller diameter? If I had the software I would do it for several differing radii to see what happens to the heat buildup.
 
We’re going to run 2 Marsa 33LHD altimeters for sure.

Am giving thought to not running the PerfectFlite back-up altimeter. Reason being is the Marsa’s are highly reliable and having a third altimeter introduces another layer of complexity with the chance for failure.

Hash that out and let me know what you guys think.

Thanks.

Chuck C.
 
Steve Shannon said:
Only if you find the time. My understanding is that the sharper the tip, the greater the thermal concentration. Would it be faster if you just did the top six inches of the nosecone and maybe a smaller diameter? If I had the software I would do it for several differing radii to see what happens to the heat buildup.
Click to expand...

That has potential. Got a table of values of interest?

Airstream temperature plots at pressure a few k' high (little hashmarks in first picture are 1" spaced)

upload_2019-4-27_11-28-35.png

upload_2019-4-27_11-29-0.png

wider shot where shock is visible (ignore the orange boundary, thats because I hovered over the face and it got outline....)

upload_2019-4-27_11-29-46.png
 

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Rail Dawg said:
Good question Dave. Unscrewing the bolt causes the spring in the switch to move to the "off" position.

Chuck C.
Click to expand...

Chuck,

OK . . . So it is a "Momentary-On" slide switch . . .

Just as a "word of caution" . . . There is potential for a serious failure mode, if the need arose to remove the rocket from the pad, or open it, after arming.

If the switch were to stick in the "On" position . . . You would not be able to disarm the electronics and would be in the dangerous situation of having to disassemble the rocket, while "Live" . . .

The primary danger comes from the altimeter(s), if they arm barometrically, of being "fooled" by the internal pressure drop, as the airframe is pulled apart . . . B-O-O-M.

Dave F.


hurler-5.jpg
 
Last edited:
Rail Dawg said:
We’re going to run 2 Marsa 33LHD altimeters for sure.

Am giving thought to not running the PerfectFlite back-up altimeter. Reason being is the Marsa’s are highly reliable and having a third altimeter introduces another layer of complexity with the chance for failure.

Hash that out and let me know what you guys think.

Thanks.

Chuck C.
Click to expand...

I have always been under the impression, not sure if read it someplace or what, that you shouldn’t use the same altimeter for your backup as the primary. If you have an anomaly with the primary it could happen with the backup as well.
 
davdue said:
I have always been under the impression, not sure if read it someplace or what, that you shouldn’t use the same altimeter for your backup as the primary. If you have an anomaly with the primary it could happen with the backup as well.
Click to expand...

That’s a good point.

Chuck C.
 
jbr said:
having gone thru 2 boxes of 500 ematches for ejection charges, I have never had any issues using the same brand of altimeters
the only problems I have had with altimeters have been user based
Click to expand...

That’s actually some good words of wisdom there.

Chuck C.
 
davdue said:
I have always been under the impression, not sure if read it someplace or what, that you shouldn’t use the same altimeter for your backup as the primary. If you have an anomaly with the primary it could happen with the backup as well.
Click to expand...

It depends. In my profession everything we did had some kind of means of surviving a system failure. Having a second altimeter identical to the first altimeter has the benefit of not requiring additional learning.
It doesn’t protect you against an error with the design though. Fortunately those are extremely unlikely. They have happened though. The one I’m most familiar with is the flight of Anthony Cesaroni’s Hyperion rocket at RocLake (different spelling then). The rocket had a Hypertek hybrid motor and two identical AltAcc altimeters. Both altimeters failed identically when they failed to sample the acceleration of the rocket quickly enough and the apogee was not correctly calculated. Having a barometric altimeter as the redundant deployment controller would have saved the rocket.
 
2 altimeters doubles the probability of an altimeter failure.

2 altimeters increases the probably of getting a deployment....sometime, but not necessarily at the right time.s

The more altimeters you have, the earlier will be your first deployment, if programmed for the same time.

Consider all the failures possible, not just the fail to get an event.
 
Steve Shannon said:
0 to 3/4 inch radius by 1/8s, looking at both drag and temperatures.
And we probably ought to start a separate thread rather than distract from Chuck’s thread.
There are lots of technical papers reaching back 50 years or longer (and current as well) documenting the effects of spherically blunted nosecones.
For instance:
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19670024114.pdf
Click to expand...

Whoa, mach 20? The X-15 with the XLR-99 motor flew with a very rounded nose.

NAR_X-15A-2_left_front_Jack_McKay_19651202_book.jpg
 
Ez2cDave said:
Chuck,

OK . . . So it is a "Momentary-On" slide switch . . .

Just as a "word of caution" . . . There is potential for a serious failure mode, if the need arose to remove the rocket from the pad, or open it, after arming.

If the switch were to stick in the "On" position . . . You would not be able to disarm the electronics and would be in the dangerous situation of having to disassemble the rocket, while "Live" . . .

The primary danger comes from the altimeter(s), if they arm barometrically, of being "fooled" by the internal pressure drop, as the airframe is pulled apart . . . B-O-O-M.

Dave F.


View attachment 381174
Click to expand...

Honestly I don't see why you don't get one of the well made screw switches for this rocket. No point in using a 5 cent switch on a 5k rocket and risk losing it all.
 
0011001100 said:
Honestly I don't see why you don't get one of the well made screw switches for this rocket. No point in using a 5 cent switch on a 5k rocket and risk losing it all.
Click to expand...

I think you’re right. After doing some test connections yesterday I wasn’t impressed with the robustness of the switch at all.

Am going to go with a switch far more able to handle the potential stresses.

Thanks.

Chuck C.
 
Rail Dawg said:
I think you’re right. After doing some test connections yesterday I wasn’t impressed with the robustness of the switch at all.

Am going to go with a switch far more able to handle the potential stresses.

Thanks.

Chuck C.
Click to expand...

Chuck,

Good call on changing to a different switch . . .

There was potential for a serious failure mode, if the need arose to remove the rocket from the pad, or open it, after arming.

If the switch had stuck in the "On" position . . . You would not have been able to disarm the electronics and would have put yourself in the dangerous situation of having to disassemble the rocket, while "Live" . . .

The primary danger comes from the altimeter units, potentially, not being able to be powered down. If they are designed to arm barometrically, they might have been "fooled" by the internal pressure drop, as the airframe was pulled apart . . . B-O-O-M !

Dave F.

hurler-5.jpg
 
Rail Dawg said:
I think you’re right. After doing some test connections yesterday I wasn’t impressed with the robustness of the switch at all.

Am going to go with a switch far more able to handle the potential stresses.

Thanks.

Chuck C.
Click to expand...
Chuck, check out the screw switches from Missileworks. Easy to mount and very reliable.
 
After using various switches I found these combat robotic switch. I defy anyone to find a more robust unit.
Get a T-handle allan wrench to arm [3.00]
Rated to 40 amps continous [100amp 10 sec]
The block is solid Delrin and once switch is armed it cannot move till you dis-arm it.

https://www.fingertechrobotics.com/proddetail.php?prod=ft-mini-switch

Screen Shot 2019-04-29 at 6.38.47 PM.png

By the way I got around areo-heating by replacing tip with phenolic rather than metal.

Mount switches on BP next to vent holes and T-handle to arm.

20160809_172440.jpg
 
blackjack2564 said:
After using various switches I found these combat robotic switch. I defy anyone to find a more robust unit.
Get a T-handle allan wrench to arm [3.00]
Rated to 40 amps continous [100amp 10 sec]
The block is solid Delrin and once switch is armed it cannot move till you dis-arm it.

https://www.fingertechrobotics.com/proddetail.php?prod=ft-mini-switch

View attachment 381344

By the way I got around areo-heating by replacing tip with phenolic rather than metal.

Mount switches on BP next to vent holes and T-handle to arm.

View attachment 381343
Click to expand...


Ok I like this “combat robotic switch”.

Looks like it can take a beating and those wire connectors are solid. I’m going to order these and see how they work.

Thanks for this and to the others with their good ideas.

Chuck C.
 
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