There is no way that this rocket is successful, but darn it I am going to try! (Mach 5+ Composite Case 38mm rocket)

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As someone who has worked on a few (literally 3 so is that a few? lol) hypersonic projects, I can tell you this little bit.

The closer you think you are to getting there, the further away you actually are.

Those who know, know.

One thing else, the more you blow your load at the pad, the slower you are going to go. It is extremely counter-intuitive.

Cool project nonetheless!
I know that the correct way to go really fast and not immediately break up is to get high altitude, which is where the waiting comes in.

However, I want to get hypersonic with as small a rocket as possible. This means not being able to “waste” delta-v on drag, and I instead need to get moving as fast as possible right away. It also means that even in the sim, the rocket drops to sub mach 2 in under a second after burnout.

If I wanted to do hypersonic the “right way”, I would probably stage it on top of some large dumb booster, and use a slower propellant to minimize the drag losses.
 
What I am referring to has nothing to do with altitude, breaking up, etc. There is a physical wall between your DUT, and the term hypersonic.

There is also an approach when it comes to exposed frontal area, impulse, and overall velocity.

BTW, why do you and everyone else in a certain group, keep using the term delta v almost ad nauseam? Honest question, because I honestly want to know! Not being mean either!!! 😁 😁 😁

Delta V is when your starting velocity is unknown to the reader. In this case, your starting velocity is implied, as you are on the surface of the earth and not moving relative to the surface of the earth. (IGNORE CORIOLIS!!) Therefore, you can just say velocity. I know Delta V sounds cool and all, but it really isn't and doesn't apply. Delta V is more applicable when it comes to orbital mechanics or where mass or orbital bodies comes into play due to capture and escape velocity.

For instance. Someone designing a tactical missile of some sort (ATGM), or a gun-fired projectile, does not use the term delta V, it is simply velocity. This project, and every project that people would work on within the realm of HPR and slightly beyond, velocity applies.
 
What I am referring to has nothing to do with altitude, breaking up, etc. There is a physical wall between your DUT, and the term hypersonic.

There is also an approach when it comes to exposed frontal area, impulse, and overall velocity.

BTW, why do you and everyone else in a certain group, keep using the term delta v almost ad nauseam? Honest question, because I honestly want to know! Not being mean either!!! 😁 😁 😁

Delta V is when your starting velocity is unknown to the reader. In this case, your starting velocity is implied, as you are on the surface of the earth and not moving relative to the surface of the earth. (IGNORE CORIOLIS!!) Therefore, you can just say velocity. I know Delta V sounds cool and all, but it really isn't and doesn't apply. Delta V is more applicable when it comes to orbital mechanics or where mass or orbital bodies comes into play due to capture and escape velocity.

For instance. Someone designing a tactical missile of some sort (ATGM), or a gun-fired projectile, does not use the term delta V, it is simply velocity. This project, and every project that people would work on within the realm of HPR and slightly beyond, velocity applies.
I guess the reason for me using the term delta-v instead of raw velocity is because drag is a big part of this rocket. Ive never used it for any hpr rockets before, because its not that big of a deal. In space/without drag, this rocket has around 2860 m/sec of delta v, or enough to go around mach 8.5. Problem with earth being a thing is that there is gravity and drag. So, for the sake of argument assuming fast and slow propellant have the same isp, faster propellant gets you going much faster since drag losses take a massive toll.

Thats the reason for my using of that term in the previous response, but it has almost no real significance to the rocket itself, and is a useless metric imo. I only used it to explain why I choose to use a fast propellant instead of a slower one.

If I had just said “my velocity is 2800 m/sec”, the average person on this forum would say that it makes no sense and could never happen because the term “velocity” doesnt get the point across of potential energy transferred.

But also, would you care to elaborate on this “physical wall” you speak of? Mach 4.99 and 5.01 aren’t particularly different from my understanding.
 
What I am referring to has nothing to do with altitude, breaking up, etc. There is a physical wall between your DUT, and the term hypersonic.

This is completely pointless advice unless you explain what this "physical wall" actually is and how to avoid it if possible.
 
I'm not doughting several hundred g's of acceleration. You claiming hypersonic velocities are where you are wrong severely wrong.

She went boom. Most likely either the nozzle let go or it just blew the bottom out . Valiant try I will give you that. You gotta do this again.

What I am referring to has nothing to do with altitude, breaking up, etc. There is a physical wall between your DUT, and the term hypersonic.

There is also an approach when it comes to exposed frontal area, impulse, and overall velocity.

BTW, why do you and everyone else in a certain group, keep using the term delta v almost ad nauseam? Honest question, because I honestly want to know! Not being mean either!!! 😁 😁 😁

Delta V is when your starting velocity is unknown to the reader. In this case, your starting velocity is implied, as you are on the surface of the earth and not moving relative to the surface of the earth. (IGNORE CORIOLIS!!) Therefore, you can just say velocity. I know Delta V sounds cool and all, but it really isn't and doesn't apply. Delta V is more applicable when it comes to orbital mechanics or where mass or orbital bodies comes into play due to capture and escape velocity.

For instance. Someone designing a tactical missile of some sort (ATGM), or a gun-fired projectile, does not use the term delta V, it is simply velocity. This project, and every project that people would work on within the realm of HPR and slightly beyond, velocity applies.


So gordon, one of the RRS guys, found the rocket which was launched on december 16th and it appears to have had a completely nominal flight from the recovered part (minus the definitely exploded nosecone from my oversized charges). Took the data off and it maxed out my 400G accelerometer (burnout is 0.5 sec here but I suck at excel so dont know how to plot time on the x axis). Integrating accleration gives 1700 m/sec as a lower bound due to maxed out accelerometer, or mach 5 at 2800ft asl. Apogee was also 7200ft.
IMG_0401.jpeg
IMG_0402.jpeg

I believe that makes this the fastest amateur rocket ever (faster than traveler 4 when just looking at the lower bound number). Fins did break on landing, i have no idea when the parachute deployed but it was not attached on the ground. Hypersonics are a bit challenging :)
IMG_1264.jpeg

Apogee charge did fire at apogee as well so my custom flight computer appears to be able to handle mach a-lot.

Looking forward to the v5 of this rocket at balls this year :)
 
So gordon, one of the RRS guys, found the rocket which was launched on december 16th and it appears to have had a completely nominal flight from the recovered part (minus the definitely exploded nosecone from my oversized charges). Took the data off and it maxed out my 400G accelerometer (burnout is 0.5 sec here but I suck at excel so dont know how to plot time on the x axis). Integrating accleration gives 1700 m/sec as a lower bound due to maxed out accelerometer, or mach 5 at 2800ft asl. Apogee was also 7200ft.

Holy cow, Alexander !

Congrats on finding your motor casing.

Eyeballing the coast phase acceleration ( starting at burnout = 0.5 sec, out to about 1.75 sec or so ), I don't see anything in the curve that looks like the rocket may have broken up mid-air

Did Gordon find the fins on the ground near the motor casing ?

What is the object that is hanging down from the forward end of the motor casing ?

Thanks !

-- kjh
 
Holy cow, Alexander !

Congrats on finding your motor casing.

Eyeballing the coast phase acceleration ( starting at burnout = 0.5 sec, out to about 1.75 sec or so ), I don't see anything in the curve that looks like the rocket may have broken up mid-air

Did Gordon find the fins on the ground near the motor casing ?

What is the object that is hanging down from the forward end of the motor casing ?

Thanks !

-- kjh
Yep, gordon gave me back all 4 fins as well, they were right next to it. The object hanging down is the av bay. I glued it in place to make sure it didnt move and had to break it to take it apart.
 
One thought about exceeding the range of your accelerometer ...

If your flight computer is programmed to fire the ejection charge at v=0 then the rocket may have been flying pretty fast when it blew the nose.

It depends ...

But I learned this the hard way in the olden days when developing the AltAcc which started out with a +/- 25G accelerometer :)

How fast it was going at ejection depends on how much delta-v ( :) ) was actually accumulated under that missing acceleration curve.

In addition, you might be able to extrapolate across that plateau factoring in drag from your coast phase along with your liftoff mass and propellant mass.

IOW, maybe extrapolate the missing thrust from your logged data:
568204-2162adf00c6cc0e38d3bfc28b864ebee.jpeg

Back to an estimated acceleration -vs- time plot for the missing thrust phase info:
536754-1a2d12d77bd5ff23029d75c200240d58.png

And you could even do an 'in the ballpark' sanity check if you had a thrust curve for your motor as you hinted at in Post #52 - "... the static test will tell a lot ..."

Beautiful stuff -- Just WOW !

-- kjh
 
I figured out how to add time to the plot :). Also attaching data. This is the end of my flight computers data that it logged due to a software bug but it does report in the post flight "debrief" to me apogee and that it deployed at t+5.7 seconds

1718735027913.png
 

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It might be in Sutton's book, but there is a maximum velocity formula that uses propellant mass, ISP, & C* without taking drag into consideration.
It's a good way of calculating the theoretical maximum velocity of an airframe, as drag is only going to reduce the tested design and the airframe will have mass.
 
It might be in Sutton's book, but there is a maximum velocity formula that uses propellant mass, ISP, & C* without taking drag into consideration.
It's a good way of calculating the theoretical maximum velocity of an airframe, as drag is only going to reduce the tested design and the airframe will have mass.
This was done by @Neutronium in the beginning of the thread and it is 2864 m/sec (or mach 8.4). Openrocket said 7.6 for this motor in the rocket but no idea how real that is.
 
Brainstormz123:
I am new to this stuff, so I haven't figured out if it uses a commercial grain or grains and a commercial nozzle. I'm presuming you're at least level 2.

From the data, it looks like the air drag is a significant fraction of thrust. I'm guessing the rocket would go highest if the burn rate was progessive, starting with just enough thrust for a good launch, and increasing as the air gets thinner. This might lead to a higher altitude, of course. How big is the core? Could you put a small, cylindrical homemade grain inside it, with a smaller core that was just big enough for a good launch? Alternatively, maybe a very compact booster? Estes (or more reliable brand) with big fins glued on? Maybe something very fast burning and thin stuffed in the core of the sustainer to allow reliable ignition without adding electric ignition.

I'm guessing you could save a little weight by laying up the fins with several layers of very thin uni placed at different angles. Assuming you can get uni that thin. Or at least two layers of very light spread tow fabric at 0-90 and +/-45. Should be stiffer for the weight. The core could be epoxy, carbon hairballs, and microballoons. I wonder what the weight vs drag tradeoff would be like for fins of different thickness. I also wonder, at least in the case of a low altitude rocket, what kind of aerodynamic refinements might help. Some of these things might not sim very well, of course.

Did the fins have any heat damage? The nose cone?

Thanks for a very entertaining thread, and congrats on a notable accomplishment.
 
Were you using an H3LIS331DL accelerometer set to 400 G's? A rail value of 3500 (m/s^2?) doesn't match my data when I have railed them.
I was using the adxl373 which I bought on aliexpress. Curious about the times you have maxed it out :)

Brainstormz123:
I am new to this stuff, so I haven't figured out if it uses a commercial grain or grains and a commercial nozzle. I'm presuming you're at least level 2.

From the data, it looks like the air drag is a significant fraction of thrust. I'm guessing the rocket would go highest if the burn rate was progessive, starting with just enough thrust for a good launch, and increasing as the air gets thinner. This might lead to a higher altitude, of course. How big is the core? Could you put a small, cylindrical homemade grain inside it, with a smaller core that was just big enough for a good launch? Alternatively, maybe a very compact booster? Estes (or more reliable brand) with big fins glued on? Maybe something very fast burning and thin stuffed in the core of the sustainer to allow reliable ignition without adding electric ignition.

I'm guessing you could save a little weight by laying up the fins with several layers of very thin uni placed at different angles. Assuming you can get uni that thin. Or at least two layers of very light spread tow fabric at 0-90 and +/-45. Should be stiffer for the weight. The core could be epoxy, carbon hairballs, and microballoons. I wonder what the weight vs drag tradeoff would be like for fins of different thickness. I also wonder, at least in the case of a low altitude rocket, what kind of aerodynamic refinements might help. Some of these things might not sim very well, of course.

Did the fins have any heat damage? The nose cone?

Thanks for a very entertaining thread, and congrats on a notable accomplishment.
The main point of this rocket was not at all altitude, it is maximum speed. This rocket would do 30000ft if i added mass to it anywhere, but it would go much slower too. Because drag is basically all the altitude loss, staging something like this would make a very “easy” spaceshot. The fins were compressively molded carbon and fairly light, also dont appear to have any thermal damage. Being above mach 1 for only a second or two means that there isnt much integrated heat load to damage anything. Some paint is smudged off but nothing too damaged beyond that.

In general, every design decision was geared towards minimum mass and not failing in flight. 0 thoughts were put into altitude. Also, I wanted the fastest propellant possible with the highest mass fraction, so used rcs warp9 in a conical core arrangement bonded together so I could run it linerless. Lot of mass savings were had everywhere (like I could have had a diverging section of my nozzle, but the extra thrust traded worse than the mass added)
 
I've railed the H3LIS331 twice on launches set to the 100G range. The 400ms "I" motor peaks at 124 G's at burnout. Four times from ground impacts of 670G's, 900G's, and twice at 715G's with the range set to 200G's. The peak impact G load was determined from impact velocity, impact time duration, depth of the rocket penetration into the ground, and the slope of the impact data captured at 500Hz. There is another rocket with data, somewhere out at the MTA. I searched for 3 years, but never found it before moving to Texas. There was some interest in my data as a backup for soft lunar or Martian landers. Data from a ground penetrator is better than "no data" from the soft lander. Interest has waned the past three years. Compton City College students are taking over my research. I'm giving them my high-speed hardware and software plus sensor ideas for high burn rate propellants.

Since the ADXL373 is a 3-axis sensor, is the data from the other two accelerometer channels available? Which ADXL373 library did you use? Did you record any barometric altimeter data? At high Mach numbers it might not be of much value due to the shockwaves.
 
I've railed the H3LIS331 twice on launches set to the 100G range. The 400ms "I" motor peaks at 124 G's at burnout. Four times from ground impacts of 670G's, 900G's, and twice at 715G's with the range set to 200G's. The peak impact G load was determined from impact velocity, impact time duration, depth of the rocket penetration into the ground, and the slope of the impact data captured at 500Hz. There is another rocket with data, somewhere out at the MTA. I searched for 3 years, but never found it before moving to Texas. There was some interest in my data as a backup for soft lunar or Martian landers. Data from a ground penetrator is better than "no data" from the soft lander. Interest has waned the past three years. Compton City College students are taking over my research. I'm giving them my high-speed hardware and software plus sensor ideas for high burn rate propellants.

Since the ADXL373 is a 3-axis sensor, is the data from the other two accelerometer channels available? Which ADXL373 library did you use? Did you record any barometric altimeter data? At high Mach numbers it might not be of much value due to the shockwaves.
Yes, i have the other two axis of data along with barometer, ill offload those later tonight/tomorrow. I might swap to that other accelerometer later for future board revisions. I wrote the adxl373 library myself, really basic functions for just sampling x y and z accl.
 
I was using the adxl373 which I bought on aliexpress. Curious about the times you have maxed it out :)


The main point of this rocket was not at all altitude, it is maximum speed. This rocket would do 30000ft if i added mass to it anywhere, but it would go much slower too. Because drag is basically all the altitude loss, staging something like this would make a very “easy” spaceshot. The fins were compressively molded carbon and fairly light, also dont appear to have any thermal damage. Being above mach 1 for only a second or two means that there isnt much integrated heat load to damage anything. Some paint is smudged off but nothing too damaged beyond that.

In general, every design decision was geared towards minimum mass and not failing in flight. 0 thoughts were put into altitude. Also, I wanted the fastest propellant possible with the highest mass fraction, so used rcs warp9 in a conical core arrangement bonded together so I could run it linerless. Lot of mass savings were had everywhere (like I could have had a diverging section of my nozzle, but the extra thrust traded worse than the mass added)
I knew you didn't have altitude as a goal, I just wondered if a bit of slow burn to get some altitude first would actually result in higher speeds in the thinner air.

Does anyone keep speed records for model rockets? I wonder what the smallest motor that could make a rocket go supersonic (or hypersonic) is? Could it be done with something from Estes?
 
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I knew you didn't have altitude as a goal, I just wondered if a bit of slow burn to get some altitude first would actually result in higher speeds in the thinner air.

Does anyone keep speed records for model rockets? I wonder what the smallest motor that could make a rocket go supersonic (or hypersonic) is? Could it be done with something from Estes?

No, there really aren’t speed records as recording speed accurately and consistently is a challenge. Combine that with fantastical simulations and claims of flights hitting Mach 77 on an I motor with a .1379 second burn in the lower atmosphere because a new cutting edge grain geometry was used and, well…

It’s all fun and exciting, but we need to bring some logic and basic science into the equation.

…and no, cannot break Mach with an Estes motor
 
I knew you didn't have altitude as a goal, I just wondered if a bit of slow burn to get some altitude first would actually result in higher speeds in the thinner air.

Does anyone keep speed records for model rockets? I wonder what the smallest motor that could make a rocket go supersonic (or hypersonic) is? Could it be done with something from Estes?
There is a relationship between propellant mass energy and maximum velocity. You either increase the propellant mass or the energy available in the propellant, Isp, to achieve higher velocities. Black powder has an Isp range of 80-90 seconds. The best nitrate black powder propellant I've seen was 98 seconds. All propellants below an Isp of 100 cannot achieve supersonic flight in a single stage configuration.

The smallest possible supersonic motor I built was an 18x80mm 47 N*s F motor in the pictured rocket built by Randy Sobczak.
 

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I knew you didn't have altitude as a goal, I just wondered if a bit of slow burn to get some altitude first would actually result in higher speeds in the thinner air.

Does anyone keep speed records for model rockets? I wonder what the smallest motor that could make a rocket go supersonic (or hypersonic) is? Could it be done with something from Estes?
Not a hobby rocket motor, but gyrojets were firing right around Mach 1. Its certainly possible to get something that small supersonic, but not with black powder motors in their current state. Looking at the rocket equation, which gives the maximum change in velocity neglecting drag/gravity losses, dV = ISP*g*log(m0/mf). That first term ISP is motor specific impulse and it scales linearly (double the ISP in the same rocket gives you double the dV), the last term is a logarithmic function of pre/post burn mass (m0 = initial mass, mf = final mass). This equation is why after rocketry really took off in the 40s it wasn't long before we had rockets passing the Karman line but it took well over a decade after to get something to orbit.

For comparison: it takes about 2 km/s dV to pass the Karman line on a typical rocket. The V2 had a specific impulse of 203 seconds at sealevel (239 in a vacuum), an initial mass of 12805 kg, a final mass of 4008 kg, and using the rocket equation got around 2300-2700 m/s dV.

Just launching an Estes F15 on its own with no airframe or fins: the initial mass is 101.8 g, final mass is 41.8 g, and specific impulse is ~84 seconds, so the dV would be 730 m/s. Most of that velocity would be lost to drag and gravity losses (pointing straight up it loses about 5% of its impulse just to gravity and probably substantially more from drag).

For the Aerotech O5500 (also no airframe or fins, just motor), initial mass is 16.783 kg, final mass is 7.004 kg, specific impulse is 223 seconds, and dV would be 1910 m/s.
 
Guys, there is a lot more to breaking the sound barrier than the theoretical specific impulse of the motor.
 
Guys, there is a lot more to breaking the sound barrier than the theoretical specific impulse of the motor.
Of course. But if your dV isn't supersonic, you don't even need to think about those other factors.
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drewnickel:
Thanks for that equation. Maybe I need to read a basic book about rocketry. Or at least sit down for a while and think about what's left of the physics I know. I probably could have derived that equation if I'd thought about it for a while.
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Maybe there is some kind of radar gun that's not horribly expensive that could measure the speeds. Or optically, with fuselage lengths per second, though I don't know if the latter would be accurate enough.
 
Of course. But if your dV isn't supersonic, you don't even need to think about those other factors.
-------
drewnickel:
Thanks for that equation. Maybe I need to read a basic book about rocketry. Or at least sit down for a while and think about what's left of the physics I know. I probably could have derived that equation if I'd thought about it for a while.
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Maybe there is some kind of radar gun that's not horribly expensive that could measure the speeds. Or optically, with fuselage lengths per second, though I don't know if the latter would be accurate enough.
Read George Sutton's "Rocket Propulsion Elements" Chapter 5 for the dv equation.

There are now radar units that are very small that could be used for velocity measurements.
 
There is a relationship between propellant mass energy and maximum velocity. You either increase the propellant mass or the energy available in the propellant, Isp, to achieve higher velocities. Black powder has an Isp range of 80-90 seconds. The best nitrate black powder propellant I've seen was 98 seconds. All propellants below an Isp of 100 cannot achieve supersonic flight in a single stage configuration.

snip
I'm not so sure. I think a really minimalist approach might work. While I doubt it's correct, I came up with an ork file that Openrocket thought would hit Mach 1 on an Estes F15. Estes motors, of course, have, relatively thick, heavy cases. I'm skeptical, so I started a thread in the software section. No doubt an optimized BP motor is capable of better performance.
 
Not a hobby rocket motor, but gyrojets were firing right around Mach 1. Its certainly possible to get something that small supersonic, but not with black powder motors in their current state. Looking at the rocket equation, which gives the maximum change in velocity neglecting drag/gravity losses, dV = ISP*g*log(m0/mf). That first term ISP is motor specific impulse and it scales linearly (double the ISP in the same rocket gives you double the dV), the last term is a logarithmic function of pre/post burn mass (m0 = initial mass, mf = final mass). This equation is why after rocketry really took off in the 40s it wasn't long before we had rockets passing the Karman line but it took well over a decade after to get something to orbit.

For comparison: it takes about 2 km/s dV to pass the Karman line on a typical rocket. The V2 had a specific impulse of 203 seconds at sealevel (239 in a vacuum), an initial mass of 12805 kg, a final mass of 4008 kg, and using the rocket equation got around 2300-2700 m/s dV.

Just launching an Estes F15 on its own with no airframe or fins: the initial mass is 101.8 g, final mass is 41.8 g, and specific impulse is ~84 seconds, so the dV would be 730 m/s. Most of that velocity would be lost to drag and gravity losses (pointing straight up it loses about 5% of its impulse just to gravity and probably substantially more from drag).

For the Aerotech O5500 (also no airframe or fins, just motor), initial mass is 16.783 kg, final mass is 7.004 kg, specific impulse is 223 seconds, and dV would be 1910 m/s.
Gyrojets only achieved Mach 1 at burnout with a Double-Base propellant. Within 10 feet they would bounce off of you like you were Superman.
 
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