Space X Rocket Re-entry Questions

I have a few questions I could not find on the internet that I hope some of you could help me with. What I'd really like is a description or diagram that can show me the speeds and altitude in increments from entry into the atmosphere all the way to the ground.

I'm having a debate with someone on another site that posted a video of him standing on the ground showing two space x rockets landing. He claims the two explosion noises he hear were sonic booms. I told him the rockets had likely reached terminal velocity long before he even started the video and the sound he heard was the rocket engines re igniting as seen in the video.

If it were sonic booms they would have been milliseconds apart but the bang sounds intervals were right in line with the visual of the rockets lighting up one then the other.

I'll try and find the video and post it here give me a minute.

Here's the video. It appears he turned off comments lol.

a reply to: Alien Abduct

From last week's launch:

www.msn.com...

I’d say it’s the sonic booms from the ignition phase of the rockets. The gasses coming out plus the speed of the rockets in the decent are way faster than the speed of sound. The loud racket is the sonic boom sounding continuously. I may be totally wrong as I’m not a rocket scientist, only stayed at the Holiday inn once.

Do those have turbo pumps? Or solid rocket motors?

Do those have turbo pumps? Or solid rocket motors?

I concur and Ive stayed at Holiday Inn multiple times.

The sound appears to be associated with the engine burn, as the rockets were already slowing.

Interesting answers here however..

www.eclipseaviation.com...

Why Does A Rocket Not Have A Sonic Boom?
Observations record the sound of an object, which is moving at supersonic speed, rocking and rocking when releasing shock waves at supersonic speeds. Due to the high altitude of the rocket and the change in altitude, this won’t happen.

Do Rockets Cause A Sonic Boom?
The sonic boom happens when one cubic meter per second exceeds the sound level. As a missile launches, only the exhaust of the rocket results in supersonic sound, so for the entire flight, the only thing that emits supersonic sound is the exhaust of a rocket.

You guys might be better of staying at Holiday Inn Express next time. Never been there myself but you can watch the speedometer as they fall.

spaceflightnow.com...

a reply to: mikell

Many, many articles about the boosters landing and sonic booms from them. Google "spacex booster landing sound barrier"

From FOX:

the booster landing could be seen coming down for landing along Florida's east coast. As the booster breaks the sound barrier, a shock wave moves outward in the form of a sonic boom. People could hear the thunderous sound as far inland as Orlando.

a reply to: putnam6

This is what I was thinking. The rocket only makes a sonic boom if the engine is fired making sound. Otherwise there is no "sonic" to make the boom. And being that those rockets were obviously slowed down to less than 750mph they didn't make a sonic boom when they fired. The sound heard in the video is from only the rockets igniting.

I may be wrong, but I don't think so.

a reply to: Alien Abduct

Expansion of the rocket fuel gases would generate a sonic boom? Like a firework, that bang you hear isn't the rocket displacing air, it's the ignition and explosion of said gases causing a pressure wave.

originally posted by: Grenade
a reply to: Alien Abduct

Expansion of the rocket fuel gases would generate a sonic boom? Like a firework, that bang you hear isn't the rocket displacing air, it's the ignition and explosion of said gases causing a pressure wave.

No no maybe I worded it wrong. What I meant to say is that a falling rocket that isn't ignited isn't making any sound, it's just falling. Therefore it doesn't make a sonic boom. Only when the engine is running and making sound AND the rocket is traveling faster than sound will a sonic boom be made.

I agree with you here and this is what I'm trying to argue on another platform with some dude. He thinks the sound you hear in the video in the OP is two sonic booms.

The sonic booms from each rocket come from the engine, also the stabilizer fin.

a reply to: Alien Abduct
Your friend is right. The booms are sonic booms from when the booster was still super sonic, it just so happens that the boom hits the ground about the same time as the rocket does. I really would have to dig for the link but this is included in SpaceX's environmental impact study with diagrams showing where you can here the sonic boom. These booms are only heard to RTL(return to launch) booster recoveries, which are now rare.

Another interesting fact is easterly trajectory launches create a sonic boom too but the rocket is too far offshore to be heard on land in Florida. Now that SpaceX does polar launches (due south trajectory) an additional sonic boom can be heard by the rocket from about Sebastian, Fl to Fort Pierce.

Droneship recoveries also have a sonic boom that can only be heard out to say...with the exception being sometimes the Bahamas is in the 'window' on a Southeast trajectory, and in theory parts Cuba could hear a sonic boom with a droneship recovery on a polar launch if its close enough to shore are the atmospheric conditions are ideal for it.

a reply to: Alien Abduct

When any object goes supersonic it creates a 'shockwave' aka a sonic boom. The Space Shuttle glided to the runway under no propulsion, yet still had the iconic double sonic boom announcing her arrival a few minutes before touchdown.

originally posted by: jrod
a reply to: Alien Abduct

When any object goes supersonic it creates a 'shockwave' aka a sonic boom. The Space Shuttle glided to the runway under no propulsion, yet still had the iconic double sonic boom announcing her arrival a few minutes before touchdown.

This isn't true, if the rocket isn't making any noise with the engines on it wouldn't make a sonic boom.

source

a reply to: Alien Abduct

A sonic boom has nothing to do with the rocket "making noise". It's created by the vehicle itself breaking the sound barrier. You don't get as big a sonic boom with a rocket due to altitude, and the fact that the vehicle is relatively small. The footprint of a sonic boom is relative to the vehicle area, so an aircraft leaving a sonic boom will have a much larger footprint than a Falcon 9 coming back down.

This video shows a Falcon 9 freefalling, and you hear a double sonic boom before the engine reignites.

www.space.com...

You don't need engines firing to have a sonic boom, as we saw with the space shuttle on reentry. With the Falcon 9, you're only hearing the sonic boom at the end of flight, so it appears that it only happens when the engines ignite. The higher altitude sonic booms don't reach the ground because they aren't large enough to.

a reply to: Alien Abduct

The sounds in the OP video are sonic booms. The camera is several miles from the landing site, so it takes a few seconds for the sound to reach the camera. During that time, the engines reignite, making it appear that the sound is caused by the engines igniting.

a reply to: Zaphod58

Well I'm wrong. Thanks for chiming in Zaphod!😁

originally posted by: jrod
a reply to: Alien Abduct

When any object goes supersonic it creates a 'shockwave' aka a sonic boom. The Space Shuttle glided to the runway under no propulsion, yet still had the iconic double sonic boom announcing her arrival a few minutes before touchdown.

Exactly, the supersonic glider made distinctly audible sonic booms at the landing site.