3/4 Mercury Redstone

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Not as crazy as it sounds! ;)



No guessing required. Just look at how professional motors of this size have been started quickly for many years. Heat flux + pressure threshold. Due to the large core, getting it up to the pressure threshold quickly is a challenge we don't typically have in regular grain geometries. You cannot rely on self-pressurization from the initial start of the top grain of the motor. Putting enough heat flux into the top grain to fill the motor could damage the grain.

More practical details would probably have to be in the research forum. A rough calculation gives about 100g of 'good' igniter mass, distributed to light as much of the pyrogen surface area as quickly as possible. But, lightly contained to not puke out the nozzle before doing its job.

Not to violate rules but a nearby "thermite" expert might be of assistance eh? I had a "non-physical" scare with the stuff and don't have need for it so haven't revisited it. (Spell that a loud scary bang of an open test conducted at a proper distance) Had a physical "scare" too:

ear1.jpg

No I didn't hold something to my ear I shouldn't. Stupidhead was too close to a conventional igniter test using a laptop to activate the igniter through an Arts II and no BP or BP like substance was involved. The igniter "popped" up
caught, and hit the ear. At least I had a chance to look away and my arm pushed the wire away and I managed not to burn my arm.

Now my cardinal rule (and it should be everyone's too) is first time test or first multiples of tests of anything that involves "fire" needs to ALWAYS be done at the appropriate distance. The hotter the fire, the farther away.
And sheesh, this happened a few years after my thermite scare so Stupidhead should'a known better. Kurt
 
Best way to test igniters (that I've found) is to poke a hole through a piece of luan (or even foam board), shove the wire through so the business end is away from you, set up a video camera away and pointing at the igniter head, and stand behind the board when you ignite it. Watch it afterwards on video.
 
Best way to test igniters (that I've found) is to poke a hole through a piece of luan (or even foam board), shove the wire through so the business end is away from you, set up a video camera away and pointing at the igniter head, and stand behind the board when you ignite it. Watch it afterwards on video.

Yes, that is safe and allows you to look at the big ball of flamey hot stuff. Bigger the charge, the farther away you (and your camera!) should be.

Best way to test an igniter is to contain it in a volume about the same volume as the intended volume of the core of the motor (with some safety margin). A motor casing works well. Drill a small opening in one end to allow it to vent after the test. Instrument this with a pressure sensor and high-temp thermocouple. More details would require continuing the conversation in the Research forum.
 
I'm assuming you might also want to try it with a sample of the propellant you're trying to light to see if the temp or pressure combination is adequate to actually light the stuff. But I'm just guessing here...
 
I'm assuming you might also want to try it with a sample of the propellant you're trying to light to see if the temp or pressure combination is adequate to actually light the stuff. But I'm just guessing here...

A test was already successful with an M version. Q version will be tested in two days. If that is successful, launch will be in three weeks.
 
I'm assuming you might also want to try it with a sample of the propellant you're trying to light to see if the temp or pressure combination is adequate to actually light the stuff. But I'm just guessing here...

Hi Duane,

I usually do a 2-step test for big igniters. First with the core volume and no propellant to see if the igniter lights fast and hits the pressure threshold I'm looking for. Then, a scale motor to see how fast it lights. Same core volume ratio to the igniter mass as the big motor. The pressure part of the testing is similar to sizing an ejection charge... need to know the pyrogen gas constant, burn rate, and density. The other part is the heat flux output of the igniter. That depends on the pyrogen and how it is distributed across the grain. A thermocouple within a known mass (that holds up to the flame) will give a relative value when comparing pyrogens.

As with an ejection charge, you need to make sure it burns without throwing around unburned stuff. Powder form is faster to light, but hard to contain. And can be more like a flash powder with too much damage to the grain. One big blob stays contained but is slow to ignite. For some pryogens, the depth of the charge could be above the DDT threshold and become a high explosive. The compromise solution is well known and available in NASA and Mil documents online.
 
A test was already successful with an M version. Q version will be tested in two days. If that is successful, launch will be in three weeks.

Test in 2 days - so 3/10
Flight 3 weeks later - 3/31? Easter Weekend?
Yuck - wanted to attend but too far to get back in time
 
Test in 2 days - so 3/10
Flight 3 weeks later - 3/31? Easter Weekend?
Yuck - wanted to attend but too far to get back in time

No, I'm an idiot. :facepalm:

The test has been postponed to the next MDRA launch, March 17-18. Flight will be April 7 or 8, the weekend before Red Glare (April 13 - 15).
 
Last 2 bags are done --there was a shipping delay because local post office hasn't figured out how to navigate a field of the Pennsylvania state flower...


PA State flower.jpg


Later!

--Coop
 
TRF,

Launch will be either 7 April or 8 April 2018 depending on weather. That is T-18 days by my calendar.

We have received our class 3 permit. Thank you Bob.
We have successfully tested our motor. Scott S is the man.
Rocket is being painted
Launch tower is being welded
Tom C has all of the chutes packed and ready
Ground testing will be scheduled
Electronics are ready for install

Feckless for Sure
 
TRF,

Launch will be either 7 April or 8 April 2018 depending on weather. That is T-18 days by my calendar.

We have received our class 3 permit. Thank you Bob.
We have successfully tested our motor. Scott S is the man.
Rocket is being painted
Launch tower is being welded
Tom C has all of the chutes packed and ready
Ground testing will be scheduled
Electronics are ready for install

Feckless for Sure

Best of luck my friend. It's incredible you took a public "bath" with your intentions to try to scope out knowledge from the high level peanut
gallery. This'll probably be the highest flying built up project since the Australian V-2. They took some hits from the "more horsepower" gang
but stuck with, "we designed it to do what the structure is supposed to do and just did it."

Looks like the motor came up gently without a fuss, got down to business and carried on in a very mellow, laid back manner. It didn't suggest to me
a frenetic, on the edge firing where everything is pushed to the limit. Just git'r done. Yeah it was loud, but it was 8 inches big. Kurt
 
TRF,

Launch will be either 7 April or 8 April 2018 depending on weather. That is T-18 days by my calendar.

We have received our class 3 permit. Thank you Bob.
We have successfully tested our motor. Scott S is the man.
Rocket is being painted
Launch tower is being welded
Tom C has all of the chutes packed and ready
Ground testing will be scheduled
Electronics are ready for install

Feckless for Sure

When on those dates? Anticipate starting to set up in the morning and fly the afternoon of the 7th or early the 8th?
Thinking of trying to drive down that Saturday morning (but it is almost a 6 hour drive)
 
Good luck with the prep and flight. :clap:


This'll probably be the highest flying built up project since the Australian V-2.
:tongue: :)
624' we got to. GLOW was 400kg. Just glad the recovery systems worked at almost ground level! It has to be the most impressive small park flyer I have seen!
 
What is the simulated altitude now that you have the motor's thrust curve and a good estimate of the finished weight?
 
John,

Good to hear from you and thanks for your reply. I think we will fly a solid kilometer or 3200 feet. Otherwise we will CATO at 625 feet. Either way we are we are going "over the top." Should be lots of fun and we would enjoy your company. Hope you will attend.

Feckless Counsel
 
Painting the parts. Shiny paint on the capsule shows a lot if dimples, seams and other skin defects. Hope the vinyl lines make all that disappear. Compare that to the "dull hammered white" of the airframe.

Painted white 2.jpg

Painted white 1.jpg

Painted escape tower.jpg

capsule painted.jpg
 
April 7th, right at the same time as Nasa's SLI. Oh well, I'll be reading the flight reports and watching video!

~
 
Painting the parts. Shiny paint on the capsule shows a lot if dimples, seams and other skin defects. Hope the vinyl lines make all that disappear. Compare that to the "dull hammered white" of the airframe.

It just adds to the authenticity of the look. I have yet to see a NASA rocket in person that looks as good as what we try to reproduce, let alone a Nathan master piece. I have no doubt that once she is all assembled and sitting on the pad that she will be awe inspiring in all of her splendor.
 
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