|
|
Post by Jairo on Jun 30, 2005 8:50:39 GMT -4
In Bart Sibrel´s Astronauts Gone Wild, it is said that Al Bean and Geene Cernan contradicted each other when answering if the descent engine could be heard.
I know that Cernan said it was hard to tell the difference between feeling and hearing the sound, probably because he was meaning he knew the engine was loud by feeling the vibration through the contact with the ship.
Besides I know Al Bean said it couldn´t be heard, I don´t know exactly what was his wording and context.
Do you know anything about this case?
|
|
|
|
Post by JayUtah on Jun 30, 2005 9:12:16 GMT -4
No, but I'm not surprised. The characteristic vibration frequencies of most rocket engines hover around the lower limit of human sound perception: 10 Hz or so. Besides, if one astronaut heard it and the other one didn't, that's not a problem. We know it's not tremendously loud.
|
|
|
|
Post by Jairo on Jul 1, 2005 11:52:17 GMT -4
Cernan used the word "loud" to describe it.
Sibrel´s critic seems like a misquote and it can be debunked by other means, but I think this case deserves a closer look.
|
|
|
|
Post by JayUtah on Jul 1, 2005 14:00:22 GMT -4
"Loud" is subjective. And there's a difference between assuming it would be loud (further assuming it would be audible) based on how much vibration you're feeling, and actually hearing something that's loud.
|
|
|
|
Post by Jairo on Jul 1, 2005 17:11:37 GMT -4
Well, that was basically what I said when I debunked this.
I also added that Cernan was a veteran from Gemini. If being in missions whose authenticity was out of question didn´t change his mind, he could as well be in a true Apollo mission and keep describing engines that way.
|
|
|
|
Post by inconceivable on May 20, 2009 23:19:51 GMT -4
I was wondering why the explosive bolts, during seperation of the LEMN on ascent from the moon, weren't heard on the mics.
|
|
|
|
Post by AtomicDog on May 21, 2009 0:21:01 GMT -4
Why would they be? The microphones were inside closed spacesuit helmets.
|
|
Bob B.
Bob the Excel Guru?
Posts: 3,072
|
Post by Bob B. on May 21, 2009 0:31:29 GMT -4
I can't imagine why the explosive bolts would be anymore audible than the engine.
|
|
|
|
Post by Jason Thompson on May 21, 2009 4:52:34 GMT -4
I can't imagine inconceivable actually cares what we say in reply, given past form....
|
|
|
|
Post by PeterB on May 21, 2009 9:42:36 GMT -4
Why would they be? The microphones were inside closed spacesuit helmets. And they were highly directional. |
|
|
|
Post by inconceivable on May 21, 2009 10:28:58 GMT -4
If Cernan said the engines were loud than possibly then the explosive bolts would have been heard also. We know that on the moon, the hammering of some of the rocks was picked up on the mics. So maybe the explosion of the bolts?
|
|
|
|
Post by AtomicDog on May 21, 2009 14:28:36 GMT -4
Now what might be the difference between someone in a spacesuit hammering on a rock and someone in a spacesuit standing on a floor with an explosive event occurring many feet from them?
|
|
|
|
Post by Jason Thompson on May 21, 2009 15:15:03 GMT -4
Even if the explosive bolts could be heard, their detonation coincided with the ignition of the engine, so how would they be distinguised?
|
|
|
|
Post by Kiwi on May 22, 2009 7:33:39 GMT -4
Inconceivable, what sort of sound do you expect explosive bolts to make in a vacuum? The same as on earth? And what sort of sound would we hear if it did indeed reach the microphones inside the helmets? Could it even reach the microphones? Perhaps you could research the matter and come up with some figures. Let's see, I'm no expert, so just guessing: - Decibels reached by the explosions of unrestrained bolts in earth's atmosphere.
- Decibels transmitted through the structure of the LM descent stage on earth...
- ...And in a vacuum.
- Whether or not the sound, if any, reached the ascent stage before it launched.
- Etc....
|
|
|
|
Post by drewid on Jun 11, 2009 4:01:05 GMT -4
I've not done very much research so I could be off.
There is a big difference between perceived loudness and actual volume. How much vibration someone is picking up will increase or decrease perceived volume.
Companies sell transducers you can bolt to a chair that introduce subsonic vibration into your 5.1 surround sound mix. This greatly increases the percieved volume of bass frequencies without affecting actual volume at all.
other points -
You can see from recent onboard footage of shuttle takeoff, and from testimony of other astronauts, that rockets produce lots of vibration in air, but a lot less in a vacuum. You can't say "it produces x horsepower therefore its x loud." It depends where the combustion is taking place.
Peoples hearing differs, 10 hz is waaay below most peoples hearing, which tends to bottom out just above 20hz.
|
|
