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ASPIRE-ing To Go Supersonic AND Hear OR Detect It...

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RocKiteman

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Yes, the Subject line is serious, but ALSO a pun. DON'T bother saying "DON'T QUIT YOUR DAY JOB". I'VE ALREADY HEARD IT. Over the decades. From about 10K people. BEFORE you....

I am posting this HERE - I was not sure exactly where to do so. I base this on a thread in the Mid-Power forum about the Apogee Components' Aspire rocket going supersonic. {I DIDN'T want to send THAT THREAD off topic like I usually do, hence I am posting this 'here'.}

I have Tim Van Milligan's MODEL ROCKET DESIGN AND CONSTRUCTION book. Both the 2nd & 3rd editions. In them he discusses how a rocket can go supersonic and produce a shockwave, but it usually cannot be heard on the ground because the rocket is travelling vertically, not horizontally.

My question to you - who PROBABLY know MORE about electronics {and most everything else} than I do - is this: WHAT device/gizmo/thing would I need to use to hear AND/OR detect a sonic 'boom' {maybe sonic 'crack' is a better description} from a rocket travelling vertically?

I don't need any suggestions on WHERE to locate it, just WHAT could I use.

{Thanks in advance!}
 

dhbarr

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Well, if you have two accurate computer clocks w/ decent mics that's probably the easiest way.
 

georgegassaway

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The device you would need to hear the "sonic crack" would be some kind of electronic microphone/recording device attached to a balloon flying at the altitude that you expect for the rocket to be supersonic. Or maybe an electric powered sailplane that carried the microphone payload to the desired altitude plus a few hundred feet, then dropped the payload(with its own chute) because the air flowing past the microphone during glide would mess with the audio (Actually, same could be true just falling down on a chute if the rate was too fast).

The issue of hearing a supersonic rocket from the ground has come up many times. And pretty much, by the time the rocket is supersonic, the tiny shock wave it would have is unlikely to intersect with the ground, unless the observer ("hearer" was a long long LONG way off. And even then, they'd have trouble determining other launch related noises from the supersonic crack.

So if you really wanted a recording of it, I think you'd need to have the recording system airborne at aobut the altitude of the rocket, and not far off. A free-floating balloon would drift away too fast, so that's one reason why I thought of an electric glider to carry it up then drop it. Or...... an electric powered BLIMP, but those can't handle much wind, and even more complexity/cost (I could see Mythbusters having tried this, but not a modeler). Interestingly, an R/C Blimp's "envelope" would probably be an good physical amplifier of the noise. Not a rece

A much simpler thing would be to just carry onboard electronics inside the rocket, that are capable of determining the velocity of the rocket. Altimeter-based methods do not like supersonic airflow, so more like ones that use inertial / accelerometer sensors.
 

MClark

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Except for you living in Florida......
Launch from bottom of a deep canyon, stand on the rim and hear it go by.

When rockets come in from very high altitude with no ejection sometimes the boom can be heard.

M
 

Steve Shannon

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Yes, the Subject line is serious, but ALSO a pun. DON'T bother saying "DON'T QUIT YOUR DAY JOB". I'VE ALREADY HEARD IT. Over the decades. From about 10K people. BEFORE you....

I am posting this HERE - I was not sure exactly where to do so. I base this on a thread in the Mid-Power forum about the Apogee Components' Aspire rocket going supersonic. {I DIDN'T want to send THAT THREAD off topic like I usually do, hence I am posting this 'here'.}

I have Tim Van Milligan's MODEL ROCKET DESIGN AND CONSTRUCTION book. Both the 2nd & 3rd editions. In them he discusses how a rocket can go supersonic and produce a shockwave, but it usually cannot be heard on the ground because the rocket is travelling vertically, not horizontally.

My question to you - who PROBABLY know MORE about electronics {and most everything else} than I do - is this: WHAT device/gizmo/thing would I need to use to hear AND/OR detect a sonic 'boom' {maybe sonic 'crack' is a better description} from a rocket travelling vertically?

I don't need any suggestions on WHERE to locate it, just WHAT could I use.

{Thanks in advance!}
A tall ladder. Sorry, I had to. I'm wired that way.
Actually anything that can reflect or detect the shock wave placed at any level that is above the altitude where the velocity hits Mach and below where is drops below Mach will work. A kite, drone, or balloon with a microphone could do it as long as they are somewhere close to the path of the rocket.
Near the beginning of the 20th century, a soldier fired a suppressed rifle along a row of fence posts. Each time the supersonic bullet passed one of the posts the crack of the shock wave was reflected back. The people watching heard a series of cracks, all coming from that one bullet.




Steve Shannon
 

K'Tesh

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On the subject of balloons... there are those balloons that are nothing more than a thin black plastic bag that are filled with air. The heat from the sun causes it to expand and become lighter than air. Apparently they need relatively calm conditions for launch and recovery (if you want it back to reuse) but a teatherd one of those might work for you. I'd say 3 points of teathering to guarantee proper positioning, and launch in the morning for best lifting results.

I mention this as they quite large, not terribly expensive (no need for lighter than air gases), reusable (if care is taken)(or disposable) and that amplification of sound previously mentioned might be even more pronounced.

[video=youtube;hQWttrozUnQ]https://www.youtube.com/watch?v=hQWttrozUnQ[/video]
 

RocKiteman

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The device you would need to hear the "sonic crack" would be some kind of electronic microphone/recording device attached to a balloon flying at the altitude that you expect for the rocket to be supersonic. Or maybe an electric powered sailplane that carried the microphone payload to the desired altitude plus a few hundred feet, then dropped the payload(with its own chute) because the air flowing past the microphone during glide would mess with the audio (Actually, same could be true just falling down on a chute if the rate was too fast).

The issue of hearing a supersonic rocket from the ground has come up many times. And pretty much, by the time the rocket is supersonic, the tiny shock wave it would have is unlikely to intersect with the ground, unless the observer ("hearer" was a long long LONG way off. And even then, they'd have trouble determining other launch related noises from the supersonic crack.

So if you really wanted a recording of it, I think you'd need to have the recording system airborne at aobut the altitude of the rocket, and not far off. A free-floating balloon would drift away too fast, so that's one reason why I thought of an electric glider to carry it up then drop it. Or...... an electric powered BLIMP, but those can't handle much wind, and even more complexity/cost (I could see Mythbusters having tried this, but not a modeler). Interestingly, an R/C Blimp's "envelope" would probably be an good physical amplifier of the noise. Not a rece

A much simpler thing would be to just carry onboard electronics inside the rocket, that are capable of determining the velocity of the rocket. Altimeter-based methods do not like supersonic airflow, so more like ones that use inertial / accelerometer sensors.

Roger all that, George.

Kite-based, not balloons, r/c aircraft, or "D-WORDS". You can hang A LOT of sh~t from a kite - or kite line - if you know how to do it. One of my OTHER HOBBIES is "KAP" - "Kite Aerial Photography". And while the KITEMAN in RocKITEMAN primarily refers to my interest in using Rogallo Parawings {or maybe even jalbert Parafoils} for rocket recovery, I also enjoy doing kite-based stuff.
 
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RocKiteman

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A tall ladder. Sorry, I had to. I'm wired that way.
At MY HEIGHT, I need a LADDER for EVERYTHING...:wink:

Actually anything that can reflect or detect the shock wave placed at any level that is above the altitude where the velocity hits Mach and below where is drops below Mach will work. A kite, drone, or balloon with a microphone could do it as long as they are somewhere close to the path of the rocket.
Kite-based is what I want to do. I am not interested in trying balloons, and I REALLY don't want to try D-WORDS {drones}.

Near the beginning of the 20th century, a soldier fired a suppressed rifle along a row of fence posts. Each time the supersonic bullet passed one of the posts the crack of the shock wave was reflected back. The people watching heard a series of cracks, all coming from that one bullet.

Steve Shannon
Interesting....
 
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dhbarr

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Computer clocks with mics?
All computers have clocks. If you have a pair that drift at about the same rate and ingest GPS/GLONASS/GALILEO, you can be certain they agree on the time to about 40ns.

Now that they both very precisely know what time they think it is, their time-stamped audio can be compared. Throw in your accel-and-baro measurements together with temp, altitude, humidity... yeah, you can prove you broke mach and play back the audio for the doubters.

You -did- say I didn't need to worry about how to get the system to altitude.... :). But I suppose investigating which motors would break mach lowest would be useful in this context. h399 flying case?
 

georgegassaway

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I did not mention drones since the self-generated noise would ruin the experiment. Also why I thought of an electric sailplane, get high up then glide. But I know from carrying tiny video cameras (like 808s) on sailplanes and rocket boosted gliders that there is still "wind" noise.

Which is why I morphed that into the sailplane dropping a listening device payload on a chute, though again that could cause noise if the descent rate was too fast. Or to use a balloon.

A tethered kite pretty much requires a decent amount of wind to carry up a payload to a good enough height. While a tethered balloon works best with low wind.

BTW - Solar balloons are nice novelties but are so wimpy they can't carry much of anything (and work best a couple of hours or so before local noon before the ambient air gets too warm, and of course requires an absolutely clear sunny day). Note in the above video that without any payload at all, it does not rise up very high , the angle on the line is very shallow. And that is in a LIGHT wind. For this kind of experiment the balloon would need to have plenty of buoyancy so that the wind would only blow it say 10-15 degrees off of vertical (75-80 degree elevation), unless it was a really high wind day.

Even a 3 foot helium balloon is rated at carrying about 4 ounces max (but a well-designed system for this could be done that light or lighter).

The more the wind, the more wind noise could be a problem. Although perhaps with a good wind screen method this could be minimized enough without muffling the desired sound too much.


Oh, here's a video of a GoPro on a kite. Going by the audio, apparently there were hundreds of supersonic objects flying past it......

[video=youtube;snwZM-b6gy4]https://www.youtube.com/watch?v=snwZM-b6gy4[/video]

Uh, no. Those were the sounds of the kite (fabric fluttering at times) and its lines. It would theoretically be easier to filter out the sounds of a Drone's motors/props (very very consistent) than to try to deal with the anarchy of the noise on this kite, to "hear" a supersonic object go past.

BTW - When a big rocket that does not deploy its chute, comes crashing down vertically, I will certainly admit that it makes a sound. When it crashes into the ground, that is. Claims of spectators on the ground hearing a supersonic crack before impact are physically impossible for near-vertical impacts. And once the nose touches the ground there's a cacophony of impact noise for awhile, making it also impossible for human ears to determine a supersonic crack from a nose hitting a rock crack or whatever else crack noises as the rocket is destroyed on impact.
 
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hcmbanjo

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The device you would need to hear the "sonic crack" would be some kind of electronic microphone/recording device attached to a balloon flying at the altitude that you expect for the rocket to be supersonic. Or maybe an electric powered sailplane that carried the microphone payload to the desired altitude plus a few hundred feet, then dropped the payload(with its own chute) because the air flowing past the microphone during glide would mess with the audio (Actually, same could be true just falling down on a chute if the rate was too fast).

The issue of hearing a supersonic rocket from the ground has come up many times. And pretty much, by the time the rocket is supersonic, the tiny shock wave it would have is unlikely to intersect with the ground, unless the observer ("hearer" was a long long LONG way off. And even then, they'd have trouble determining other launch related noises from the supersonic crack.

So if you really wanted a recording of it, I think you'd need to have the recording system airborne at aobut the altitude of the rocket, and not far off. A free-floating balloon would drift away too fast, so that's one reason why I thought of an electric glider to carry it up then drop it. Or...... an electric powered BLIMP, but those can't handle much wind, and even more complexity/cost (I could see Mythbusters having tried this, but not a modeler). Interestingly, an R/C Blimp's "envelope" would probably be an good physical amplifier of the noise. Not a rece

A much simpler thing would be to just carry onboard electronics inside the rocket, that are capable of determining the velocity of the rocket. Altimeter-based methods do not like supersonic airflow, so more like ones that use inertial / accelerometer sensors.
Hey George!
Do you remember when all the 1976 NARAM participants stood in a long line in hopes of hearing the sonic boom (or crack) from the FSI Mach 1 system?
http://www.ninfinger.org/rockets/nostalgia/77fsi20b.html
I think it was the 1976 NARAM!
 

georgegassaway

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Hey George!
Do you remember when all the 1976 NARAM participants stood in a long line in hopes of hearing the sonic boom (or crack) from the FSI Mach 1 system?
http://www.ninfinger.org/rockets/nostalgia/77fsi20b.html
I think it was the 1976 NARAM!
Maybe it was NARAM-17 in 1975. Or both.

I remember some people claiming they heard it, but I never bought into it (that any supersonic crack could be heard from the ground, and a suspicion it never went supersonic to begin with). But some heard "something" that they attributed to being a sonic crack. Given that the Mach 1 was an FSI F100, staged to a D20, and IIRC the D20 was a tight fit inside of the F100, the "crack" could have been the instant that the D20 popped off from the F100. And that "pop" would have been heard 1/2 to a second after staging, because of the speed of sound for that pop to travel to the ground to be heard (and the farther out horizontally, the longer the time to hear it). Too many people could attribute that delayed "pop" to the 2nd stage going supersonic and not staging since they already "saw" it stage long before they heard the pop - not realizing the delay in hearing the sound of staging. IIRC, on at least once someone said they heard it...... about 8-10 seconds after liftoff. Yeah.... ejection! The power of suggestion, hearing what you want to hear.

In any case pretty much the only viable (?) way to have tried to document that (the claimed ground-based sounds of the FSI ******) would have been with a very sensitive microphone set-up recording at high speed (audio tape version of slow motion), to later play back and use some sort of instrumentation to try to distinguish random noise, and rocket motor noise, from the audio profile of an expected supersonic crack (with state of the art early 70's technology, available to hobbyists).

Something sort of like this, which is more practical to do today. But someone would really have to know about acoustics/audio to make heads or tails out of the raw data (to tell a supersonic crack from ejection, or staging, or random noise having nothing to do with a rocket, and so on):

 
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K'Tesh

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kite's shadow looked like a double French Military/delta design. Right?
 

tomsteve

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The device you would need to hear the "sonic crack" would be some kind of electronic microphone/recording device attached to a balloon flying at the altitude that you expect for the rocket to be supersonic.
iirc, there was an article in one of the rocket magazines back in the late 90's/early 2000's where a man did the math, determined the altitiude his rocket and motor combination would break mach, and found a cliff where he could place the recording device on the cliff then launched next to the cliff.
 

mccordmw

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Get a cheap drone with a camera on it. Hover in the general area of the launch to capture the footage and hear/see the shockwave? Decent beginner drones run well under $100. I'm considering getting one to help spot rockets that land in the tall grass/corn/soybeans...etc.
 

billdz

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I don't know anything about supersonic flight, does the recording device have to be outside the rocket? If a recorder placed within the rocket would hear the sonic boom, you could just put a phone in the rocket and turn on the Sound Recorder. This Posh Micro X costs $50 shipped and weighs 52 grams, I use it as a tracker with the Find My Droid app.

launched the Posh Micro phone for GPS tracking and flight stats.jpg
 

Threemorewishes

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I don't believe a model rocket is large enough to generate over pressure that will be heard over the surrounding background noise.
 

RocKiteman

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I don't know anything about supersonic flight, does the recording device have to be outside the rocket? If a recorder placed within the rocket would hear the sonic boom, you could just put a phone in the rocket and turn on the Sound Recorder. This Posh Micro X costs $50 shipped and weighs 52 grams, I use it as a tracker with the Find My Droid app.
The sonic boom {or sonic crack} is not audible inside the rocket. Same for an aircraft flying at supersonic speed.
 
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RocKiteman

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I don't know anything about supersonic flight, does the recording device have to be outside the rocket? If a recorder placed within the rocket would hear the sonic boom, you could just put a phone in the rocket and turn on the Sound Recorder. This Posh Micro X costs $50 shipped and weighs 52 grams, I use it as a tracker with the Find My Droid app.
The sonic boom/crack/pressure wave/whatever is much like the bow wave of a boat travelling on water. People on the shore getting 'hit' by that bow wave as the boat passes by them are experiencing the kind-of/sort-of equivalent of people hearing a sonic boom.
 

RocKiteman

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I don't believe a model rocket is large enough to generate over pressure that will be heard over the surrounding background noise.
AFAIK: Formation of a sonic boom/crack/whatever is the result of an object exceeding the local speed of sound. Size is not an overriding factor.

Read what Tim Van Milligan of Apogee Components has written about Apogee's "Aspire" rocket kit.
 
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dhbarr

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kite's shadow looked like a double French Military/delta design. Right?
Delta conyne is, as I understand it, the loadiftingest variety currently.
 

RocKiteman

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Delta conyne is, as I understand it, the loadiftingest variety currently.
Some use rokkaku's for good lift. {That is the only other type of kite that I can think of off the top of my head at the moment.}

It also depends on wind speed as well. The Dopero I mentioned in a previous post was created by German KAP'er Ralf Beutnagel in the mid ??? 1990's. It is DESIGNED for lifting camera gear in low wind speed conditions. "Dopero" stands for "Double Pearson's Roller", IIRC. The "Pearson's Roller" is a type of kite invented by a Brit[?] named Alek[?] Pearson in the early[?] 20th century.

They say when you get old, memory is the second thing to go. I forget what goes first...:wink:
 

georgegassaway

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Put a cheap camera (that records sound), even the 808 keychain type camera, onto a kite and send it up as a simple test.

Most likely there's going to be a lot of sounds and"pops" and creaks, as heard hundreds of times in the kite video I posted a few days ago.

Then imagine how the heck you could ever accurately tell that random noise of pops from a "pop" of a supersonic rocket going by, or the pop of the ejection charge.

A drone makes the problem far worse due to the self-generated engine/prop noise. Unless a hi-tech noise cancelling method is used, which does not filter out the noise you DO want to hear.

A tethered helium balloon would likely have the same pop-creak problems as a tethered kite. So to solve that, the balloon's tether line would need to be remotely detached say a minute before the launch, then rigged to pop the balloon (or drop the recording system), falling with a chute, after the rocket flew, otherwise a long long chase.

If anyone has really successfully done it.......then they ought to post the recording and other supporting data.

Otherwise, sort of reminds me of an R&D project at a NARAM in 1978. They said it was the first successful onboard video transmission from a model rocket. So, where was the video of the flight? Well, hmm, uh, hemm...haw..... they didn't have anything to record the video with. Not even an 8mm movie camera pointed at a TV screen during the flight? REALLY? Terrible project management at best, BS at worst (Tend to believe it was more of the former than the latter. But in any case very dumb and sounded fishy given the whole idea was to be able to SEE the video!). And IIRC, there was some excuse why they would not be doing a live demonstration flight at NARAM.
 

RocKiteman

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[video=youtube;snwZM-b6gy4]https://www.youtube.com/watch?v=snwZM-b6gy4[/video].
(1) I have NO IDEA why that double-delta conyne kite was SO NOISY. It OBVIOUSLY was not rigged to be as QUIET as possible.

(2) I would likely NOT put anything ON the kite. Just suspend it {or them - multiple mics} from the kite line. Most KAP'ers do it that way using either "Picavet" suspension, or {something I CANNOT remember the name of at the moment}.

(3) The built-in mic on a GoPro is NOT optimized to be "directional" AFAIK. I would use a SEPARATE microphone that had some directional {properties?} to it [them].
 
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