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AeroTech said:
That;'s because it was only half of a K2050ST, running at lower pressure.
Click to expand...
Thanks, for the reply. I was confused by the statement that 2 grains from the K2050 were used. It wasn't clear to me if this was a full K2050 or not. If I assume that this is half a K2050, then I probably can make a rough estimate of the Isp. So, if it was half a K2050 than being an I-motor might be about right for regular performance. I need to go back and look at the original post. Also, someone suggesting using larger grains (with a smaller bore diameter) in order to get to a J-motor might be worthwhile, if someone wants to try this in a larger rocket model.
 
I am assuming that half a K2050 has about 0.7430 lbm ( 1/2 of 674 grams) mass of propellant. Using a total impulse from the graph in the previous post for the Aerospike test, I get 130 lbf-sec/.7430 lbm = 174.98 sec or a specific impulse of 174.98 seconds. This compares with my calculations for a full K2050 with a convergent/divergent nozzle of 209.51 seconds. So, although the aerospike is not as good as the regular K2050 with a standard convergent/divergent nozzle, it is functioning as an aerospike for the supersonic gas. Off the top of my head I am thinking that a nozzle working only as a throat is going to have a specific impulse about roughly 58 percent of a K2050 or about 121 seconds or a little over 1/2 the K2050 specific impulse. (I am thinking that the critical pressure ratio is 0.58, but that depends on what someone uses for the specific heat ratio. I am thinking intuitively just simply multiply the fully expanded nozzle performance by the critical pressure ratio to get a throat-only performance. This is intuitive and needs more justification. In any case as I recall just a throat alone has a coefficient of thrust of 1.0)
 
aerostadt said:
I am assuming that half a K2050 has about 0.7430 lbm ( 1/2 of 674 grams) mass of propellant. Using a total impulse from the graph in the previous post for the Aerospike test, I get 130 lbf-sec/.7430 lbm = 174.98 sec or a specific impulse of 174.98 seconds. This compares with my calculations for a full K2050 with a convergent/divergent nozzle of 209.51 seconds. So, although the aerospike is not as good as the regular K2050 with a standard convergent/divergent nozzle, it is functioning as an aerospike for the supersonic gas. Off the top of my head I am thinking that a nozzle working only as a throat is going to have a specific impulse about roughly 58 percent of a K2050 or about 121 seconds or a little over 1/2 the K2050 specific impulse. (I am thinking that the critical pressure ratio is 0.58, but that depends on what someone uses for the specific heat ratio. I am thinking intuitively just simply multiply the fully expanded nozzle performance by the critical pressure ratio to get a throat-only performance. This is intuitive and needs more justification. In any case as I recall just a throat alone has a coefficient of thrust of 1.0)
Click to expand...


Gary already stated it was a LOW PRESSURE test . Stop over thinking it. The cores are larger then a 852 case , there's 1 part of the Isp loss , then a overly larger throat to lower the Pc , I'm guessing they ran about 550 psi total , so there's part 2 of a "performance loss" . I just want to know when I can get some of these loads
 
3stoogesrocketry said:
Gary already stated it was a LOW PRESSURE test . Stop over thinking it. The cores are larger then a 852 case , there's 1 part of the Isp loss , then a overly larger throat to lower the Pc , I'm guessing they ran about 550 psi total , so there's part 2 of a "performance loss" . I just want to know when I can get some of these loads
Click to expand...
Sure, but as someone that use to work in this field I want to get an idea of what is going on. I, too, was wondering about a reload. I am wondering if a person can buy a K2050 and simply just use two grains out of the package. There is also talk about the J1000ST over on the "Aerospike" thread. I am wondering about that option, but perhaps that option might put more degradation on the nozzle.
 
aerostadt said:
Sure, but as someone that use to work in this field I want to get an idea of what is going on. I, too, was wondering about a reload. I am wondering if a person can buy a K2050 and simply just use two grains out of the package. There is also talk about the J1000ST over on the "Aerospike" thread. I am wondering about that option, but perhaps that option might put more degradation on the nozzle.
Click to expand...


I agree. I apologize if my last response was semi rude . I reread it and I kinda think it was.
 
It looks like matching reloads to the aerospike nozzle takes a little bit of doing. In the other "Aerospike" thread Aerotech stated that they tried the K550W and K1100T reloads with the aerospike nozzle and the propellant were very hard on the nozzle. I assuming that the K2050 reload has been the most successful.
 
Thank you Aerotech! My TARC team has five kids and is in their second year. So far they have flown all Aerotech DMS single use motors. All perfect flights with no issues. A couple weeks ago they flew their first (and my first) reload - an F White Lightning in an RMS 29/60 case. A NAR L3 friend who is an officer of the local club here (NOVAAR) taught us how to assemble them and directly supervised the first two. The brand-new case blistered on the first flight.

I emailed Aerotech - who promptly responded on a Saturday. They had a couple follow-up questions and request for a couple more pictures. I sent them what they asked for and the result was that the igniter slipped. We supervised the kids as they prepped the motor and hooked up the leads - it was indeed up all the way and taped. Someone probably caught the wire with their foot is my guess. Aerotech said this caused the aft end of the grain to ignite instead of how it's supposed to work. The gentleman at Aerotech said this will cause the darker smoke that we saw instead of the normal White Lightening look. The altitude was also less than expected, but still plenty of thrust for a good, safe flight. Aerotech didn't explicitly say, but it sounded like the flame at ignition is also a telltale sign of a slipped igniter along with the darker smoke - at least I haven't caught flame like that in pictures on any other flights.

Since it was user error, I assumed I would be buying a new case, but Aerotech offered and happily and quickly sent us a new one! It even has a cool Apollo 50th logo. I just wanted to say thank you to an awesome company from a grateful fledgling TARC team. I didn't tell Aerotech, but we are a Homeschool Co-op TARC team and don't receive funding from a school district or anything, so, speaking as a dad, the new case is even more appreciated. :)

IMG_9679.jpg

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IMG_9867.JPG

IMG_9896.jpg

IMG_0093.jpg
 
aerostadt said:
I am assuming that half a K2050 has about 0.7430 lbm ( 1/2 of 674 grams) mass of propellant. Using a total impulse from the graph in the previous post for the Aerospike test, I get 130 lbf-sec/.7430 lbm = 174.98 sec or a specific impulse of 174.98 seconds. This compares with my calculations for a full K2050 with a convergent/divergent nozzle of 209.51 seconds. So, although the aerospike is not as good as the regular K2050 with a standard convergent/divergent nozzle, it is functioning as an aerospike for the supersonic gas. Off the top of my head I am thinking that a nozzle working only as a throat is going to have a specific impulse about roughly 58 percent of a K2050 or about 121 seconds or a little over 1/2 the K2050 specific impulse. (I am thinking that the critical pressure ratio is 0.58, but that depends on what someone uses for the specific heat ratio. I am thinking intuitively just simply multiply the fully expanded nozzle performance by the critical pressure ratio to get a throat-only performance. This is intuitive and needs more justification. In any case as I recall just a throat alone has a coefficient of thrust of 1.0)
Click to expand...
I’m showing 313 grams for two K2050ST grains, with a total impulse of 625 N-sec that indicates an Isp of about 204 seconds. The Tripoli certification may have included the delay and other inert weight lost during the burn.

4C4ACD4E-748A-44D6-AFE7-27925FB3B912.jpeg
 
The aerospike nozzle is for show only. With the limitations, there is no performance improvement compared to a regular nozzle. Might even be worse. Where aerospike nozzles are useful is long burns where the altitude changes a lot during the burn.
 
What would be the best method for opening up the core of a grain from the RCS store? Specifically larger than 1/2" where a normal drill bit wouldn't work or would be prohibitively expensive.
 
0011001100 said:
What would be the best method for opening up the core of a grain from the RCS store? Specifically larger than 1/2" where a normal drill bit wouldn't work or would be prohibitively expensive.
Click to expand...
We typically recommend drilling by hand using a plastic or aluminum bushing to guide and center the bit in the grain. Drilling on a lathe can be accomplished at 500 RPM and below, but extreme caution must be observed in terms of avoiding excess friction, metal on metal contact and ensuring the use of non-sparking electrical equipment.
 
AeroTech said:
We typically recommend drilling by hand using a plastic or aluminum bushing to guide and center the bit in the grain. Drilling on a lathe can be accomplished at 500 RPM and below, but extreme caution must be observed in terms of avoiding excess friction, metal on metal contact and ensuring the use of non-sparking electrical equipment.
Click to expand...
Do you think a hole saw bit would work? Like this:
https://www.amazon.com/LENOX-Tools-...=1616684314&sprefix=2+inch+dri,aps,179&sr=8-6Or this:
https://www.amazon.com/Basynol-Fors...=1616684314&sprefix=2+inch+dri,aps,179&sr=8-5
 
Hi, do you have any updates on the order status to Europe?

Sierrafox is still Out of Stock for every Aerotech reloads and Single-use...
 
0011001100 said:
What would be the best method for opening up the core of a grain from the RCS store? Specifically larger than 1/2" where a normal drill bit wouldn't work or would be prohibitively expensive.
Click to expand...
I use a wood auger bit in my battery powered drill set to screw (low speed). Low speed is about 200 rpm. I use a 1" drill for 98 mm grains. Price is reasonable.
 
I would NOT us a holesaw. There is a huge "rubbing surface" (the entire ID and OD of the tool. That generates a lot of heat. Exactly the opposite of what you want to do. The simple spade bit, only has a few points of contact. The rest of the area is open to cooling.
Put another way: Propellant is rubbery so the "set" [offset of all the little teeth] on the holesaw does not cut a wide enough "curf" [slot] to keep the walls from rubbing.
YMMV.
Mike
 
Zertyme said:
Hi, do you have any updates on the order status to Europe?

Sierrafox is still Out of Stock for every Aerotech reloads and Single-use...
Click to expand...
We just made a shipment to our distributor in Switzerland, and more are on the way. Sierrafox needs to contact Juerg at Spacetec Rocketry and place an order.
 

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