making a large sonic boom?

... oh mighty font of knowledge that is TRF ...


we got a level 1 cert on Friday at XPRS. we launched the crayon rocket on an H97. I say we because I wrote the checks and built the motor but otherwise my son prepped the rocket & pushed the button.

so now he's talking about what our level 2 project is going to be. I guess 3 days of high power launches burned "J350" and "K550" and "M2400" in to his brain.

but what impressed him most was the sonic boom from a small rocket on a K550. so maybe a "loud" rocket could be a fun project.

what got me thinking more about this was an article in New Scientist about mitigating the sound of the sonic boom, some glove-work on an F-5E. article - [url]https://www.newscientist.com/news/news.jsp?id=ns99994195[/URL]

what they did was make blunt leading edges and smoother transitions, to fan out the bow and leading edge shock waves.

so, if we want to make the loudest boom possible then obviously we should do the opposite: make a really really sharp nose cone and some reverse sheer fins. right?


what "stock" rockets make good sonic booms?


should we select the motor to bust through mach 1 as soon as possible or would it be better to push right up around it, like a boat at displacement speed - biggest wake, biggest waste of fuel.


yours in hearing damage,
Pete Townsend oops I mean Ted Nugent oops I mean Kirk Hammet OK how about Ludwig Van B?!?

This project sounds pretty cool. How did you hear the boom? Was it during the launch or seconds after. The reason I ask is how do you know it is a sonic boom verses a "propulsion reaction"?

About mach: Stay as far away from true mach as you can. There is a grey area around mach that if you stay in for too long your rocket will shake itself apart. It is usually best to blast through mach or stop well before mach.

Originally posted by PGerringer
About mach: Stay as far away from true mach as you can. There is a grey area around mach that if you stay in for too long your rocket will shake itself apart. It is usually best to blast through mach or stop well before mach.

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So you mean it would sort of like the scene from "the right stuff" where john glenn (????) is breaking mach and his x-1 shaking?

Originally posted by Rocketmanic
So you mean it would sort of like the scene from "the right stuff" where john glenn (????) is breaking mach and his x-1 shaking?

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Yep, exactly. I didn't see it but Ken Parker was personally present when a rocket at the Whitakers launch got caught in the .9 mach range. It came back in pieces. It is best to either go half mach or punch through quickly.

"So you mean it would sort of like the scene from "the right stuff" where john glenn (????) is breaking mach and his x-1 shaking?"

That was CHUCK YEAGER from good ol' West Virginny. John Glenn was the glory hound (excuse me, Senator) from Ohio who flew the first US orbital mission.

Anyway, they're right about Mach. The transonic zone is not a place you want to be for very long. Aircraft & rockets perform best either under or over, but not in the middle. Cessna, for example, had to put a lot of design tricks into the Citation X in order for it to maintain cruise at M.92. Most transport jets stay in the .80-.84 range and it was a big leap. Likewise for Boeing's Sonic Cruiser (unfortunately stopped), which was meant to cruise in the .98 range. Supposedly it would've been capable of sustaining Mach 1.2 if they could find a way to mitigate the boom.

"Where's the kaboom? There was supposed to be an earth-shattering kaboom!"

I don't know what you heard at your rocket launch but I doubt that it was a sonic boom generated by any rockets.

At launch, a rocket is travelling at subsonic speeds and does not generate any shock waves or sonic booms. It travels upwards (right? upwards?) for a considerable distance before it accelerates to anywhere near the speed of sound (1116 feet per second at sea level in a 'standard day' atmosphere). The point where it gets to the speed of sound may be one or two thousand feet, but for this discussion, let's just say it is a really hot performer and goes supersonic at 500 feet.

When the rocket gets to Mach 1.0 it will form a 'normal' shock wave in front of the nose. This wave is basically a flat plane extending to the left and right of the rocket, and propogates forward (upward). If you are on the ground, 500 feet behind, you WILL NOT HEAR this.

If the rocket exceeds Mach 1 the shock wave will begin to form a cone shape with the rocket at the tip. This supersonic shock wave propogates forward (upward) also. If you are on the ground, X?? thousand feet behind, you will not hear this either.

The only way for you to hear a sonic boom generated from a rocket is for someone else to launch it some distance away (half a mile? a mile?) and aim it in a horizontal flight path over your head. Then you might hear a sonic boom, but because the rocket is so small the boom will not be very loud and could easily not be heard at all.

Please let us know before you attempt a horizontal flight like this. I would like to be at least one state away.

Powderburner, your explanation would help explain why I didn't hear any noise (besides the G80 motor) when I recently flew a high performance rocket. It was estimated by RockSim at more than 1,000mph but there was no pops or booms or anything like that. I submitted a review at EMRR that should appear soon.

powderburner, thanks for the reply.


your explanation makes sense to me but doesn't explain what we saw and heard.

we saw and heard plenty of rockets flying on those K550 motors. this one smoked, ignited, and I heard the familiar rocket exhaust but quick as a flash the rocket was off the pad and out of sight. a split second later we heard a BOOOM - no extended rumbling like thunder, a quick cut-off like a real sonic boom. the BOOOM seemed to come from low altitude off the pad like maybe 200 feet, but the rocket just wasn't there, it was already gone.

I don't know if the BOOM was louder for people father away from the pad, but if that were true then it would match what you say in your post. the shock waves would reinforce better at a shallower angle, which you get by standing far away from the pad.


we were standing several hundred feet back from the pad. everyone around, close in and far, startled and looked at that launch. now I really regret missing the chance to find out whose rocket that was!



thanks other posters, I appreciate the advice about not loitering at Mach speed. best to bust on through.


(we're not planning any horizontal flights. but my Delta II tube fin model took the assassinate-the-LCO prize recently, it always flew great on C6-3 but I guess the D13-4 was too much of a good thing.)

A Sonic Boom that didnt sound like thunder? I have heard a bunch of sonic booms hanging out on Bases and on Cape Cod (the fly out over the ocean) and they sounded just like thunder, but then they were pretty far away.

I think it may have just been the rocket moving away so fast. I have heard some weird sounds when rockets are moving away very fast

A rocket would give off more of a pop than a boom!
most rockets (we build) that break mach speed ,are not generally as big as the X-1 and simply don't create a very large shockwave
and are not crossing overhead either (hopefully)

from the way I understand, it can only be heard if you happen to be standing horizontally in line with the rocket
at or very near where it reaches mach speed
because the shock wave spreads out horizontaly from the source

it's caused by air not being able to move out of the rockets way fast enough ( or compression mach .8-.9)

as someone mentioned, you don't want to design a rocket to top out at compression...thats when it would most likely fail

I never knew there was a grey area, like they say you learn something new everday
I'm no expert but I don't think you can hear a sonic boom

if you want a rocket to break mach try a caveman sonic boom https://www.cavemanrocketry.com/rocket kits/caveman kits/sonic boom.htm it comes pre covered in carbon-fiber and the fins are carbon fiber sheet, i have one that is used for the booster dart project and i hope to test it with dual deploy on a J350 or I435 which will put it around the 8,500-10,000 feet range and well over mach 1
ill take a video and see i hear a boom


matt

You wont hear the boom

the high pressure that builds up at 0.85 to 1.0 mach
get realsed in a cone shape upward away from the nosecone

I dont think you can hear there boom because of this

Even then it would be small and the sound of the motor would probably drown it out

I always thought that when the vehicle reaches mach 1, the shock wave goes behind the nose. Even then, the motor would, as Ryan said, probably drown the boom (or pop) out.


Just my 2 cents

Anyone want plans for my "mach buster 1"? it is a really super-duper cool rocket that will break mach on as little as an H242T! it will be going mach for .5 seconds on october 18th in cherryfield on an I161W. Anyone who wants plans is welcome to them. just ask. here is a pic of the rocket, and also a link to my review on EMRR: Mach Buster 1 It costs +/- $80, but it is worth it. I have no doubts about it surviving mach again and again.

wow why did such a little rocket cost sooo much?

If you really want it to break the sound barrier put a I357 in there or an I435 or a J570

sorry I lost control for a minute there

Originally posted by Neil
I have no doubts about it surviving mach again and again.

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Hola Neil, from your review I also have no doubts that you'll have good flights without problems. Although, you have to recover it again and again to keep surviving those mach flights!

p.s. While your mother may have been upset about the epoxy/table incident, consider that she still thinks of you as a young person who sometimes makes mistakes. When you are married awhile and do something like this you receive no such considerations!

Those ACME cans and lugs are expensive, and I had to order from 2 places, one for the nose, one for the rest of the stuff, and finish cure epoxy, and fiberglass, and all the other parts, inclueding the motor retainer, which itself is $20, it really adds up!
Ryan- I agree about the bigger motors, but that would have to be launched at Balls or LDRS, it would go 10,000 feet on a J570!!!!! now THATS a rocket!!!! by the way, trogdor, I agree. My head would be on the chopping block for sure if it was a wife and not my mom. luckily all that got stuck to the table was a puddle of epoxy that dripped off the waxed paper, but the rocket was stuck to that, so that was a problem. fortunatley, I got MOST of it off before my mom saw it! are you speaking from experience there????? if so, what did your wife do to YOU after you glued something to a surface that does not fly?

Try the sturdy Hawk Mountain TRANSONIC II rocket for your L2 supersonic flight. Their web site https://hawkmountain.ws/ says that "This is a very high performance rocket, capable of reaching altitudes over 14,000 feet and Mach 1.4 with an Aerotech K550W!" It would be great at the Black Rock Desert!

Neil - Only 10K on a J570? It must be heavier than I thought...

A minimalistic, 38mm Mach/Altitude buster would hit 15K on a nice windless day. Around mach 2 as well.

If you're going for altitude and speed, the ACME way is not the best way. The canister is very heavy, adds thickness to the back of the rocket when the point is to taper it, and is very thick. The ACME rail guides are VERY draggy, especially when compared to the round version of buttons, or a tower. If you want to break records or go real fast, use G10 with Fiberglass/Carbon fin to fin glassing.

Ask Rocketman248 about sticking an F101T in a 24mm fiberglassed rocket. Whiplash was felt all around, I can't wait to do it again

yeah those lugs look kinda big. If I had a big enough feild I would make one. use a tower or buttons

Just out of curiousity why did you choose the I161?

Ryan - I was wondering that as well, the I161 may not get you speed, just altitude. You want an I357T.

Availability may factor in on this...

Originally posted by Neil
but that would have to be launched at Balls or LDRS, it would go 10,000 feet on a J570!!!!! now THATS a rocket!!!!

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Give Dr. Frank a jingle... have him make you up a J1500, now THAT'S a BALLS project

only 1.4? that thing costs quite a bit! by the way, how long does that J1500 burn? does he make them himself? the lugs are that large because the fin can gets in the way if they are not. I think 10K is more than enogh for me, that would already need an FAA call in, and a billion dollars worth of beepers, transmitters etc. I chose the I161W because stephen boy had one, and he sold it to me so I could use it to enter HPR with a boom. I thought it would be a little less expensive, and easy, to buy it off him, so I did. the I357T is a blue thuder. I try to get white lighning motors if at all possible. I like the smoke! how long would that J1500 be? the thing is only 45" long, minus parachute, shock cord, nose etc. the I161W will make this thing go... let me dig it up.... here it is: Max Speed: 1193FPS, acceleration: 994 feet per second per second, altitude: 5573.09 feet, and above mach 1 for .5 seconds. if that is not a great entrance to HPR, I do not know what is. well, maybe a J570, but still. this motor was availible, and it will make that puppy SCREAM!!!!

Hi Neil,

What's the weight on your Mach Buster 1?

-Scott

Neil -

I am curious of the weight, as well. Your EMRR review says it's 12 oz. I dunno how accurate that is, but if that is the true weight, then you may be looking at a mach flight with the I161. If it's about 2 pounds fully loaded (with motor and chutes) , then it will not break the barrier. With the ACME guides hanging off of it, a mach flight is highly unlikly. It'll move, thats for sure.

My 38mm, minimalistic dual deploy rocket, 38" long, about 1.5# fully loaded is going to fly on an I300T, and that will break mach for sure. It takes a significant amount of acceleration to break through the barrier, flights hardly ever "just break" the barrier. You need to punch through with a hard hitting, fast motor, like a BT for example.

Frank's J1500 is 29" long, I believe. See a motor similar to this in action at https://www.blastzone.com/images/balls2002/clusterlaunch.jpg (that's 7 of Greg Deputy's J2000s in a LOC Ultimate Max). Jeff at Loki Research also makes a case similar to it.

JOOC, what sim program are you using? I'd be surprised if the vehicle passes Mach, I've had many, many rockets say they'd go over mach, but not quite make it. When you reach the zone of 0.85-0.90 Mach, strange turbulences begin to occur over the airframe and your C_d goes way up. After you punch through Mach, this drops off again and drag goes way down. Go figger. Anyways, what will most likely happen is your vehicle will get up to about 0.9 mach and then turbulence will stop it from going any farther. But still -- 0.9 mach! That's pretty fast.

Oh yeah... WL is a great propellant!

SpaceCAD says it would be 12 OZ, dry, 1.5 pounds loaded with the I161W. Mach or not, it will be a good entrance to HPR.

IMHO I belive the BT would really make that puppy scream. WHAM and the things is gone. Then agian with WL there is a better chance of getting it back