I'd like to hear comments on a explanation about the alleged lack of delay in radio transmissions from the Moon. Please go to the following Web page and, about 1/4 of the way down the page, you will find a passage written by Patrick Kilcullen, 17 April 2001 (just below the picture of John Young's "big Navy salute").

http://www.apfn.org/apfn/moon.htm

I've had someone ask me about this, but I'm afraid I don't know enough about how the broadcast to the public was actually set up. My impression is that Mr. Kilcullen's explanation is incorrect. Can somebody verify and/or provide a better explanation?

Thanks in advance.

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I'm sure Jay will come in with an authoritative explanation, but I agree that Kilcullen's explanation sounds wrong: the audio feed is from Mission Control, so we get their voices immediately and the astronauts with a delay. We should hear no delay between the astronauts speaking and Mission Control responding, but there should be a delay between Mission Control speaking and the astronauts responding. A number of people claim there are times when there is no such delay, but so far no one has supplied a specific example. (And in any case, if it were a hoax, it would be a simple matter to build a delay into the communications system.)

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That's a gem of a website.

I loved this one,

The maximum thrust was 10,000 lbf, not "several hundred thousand pounds of thrust."

And most of the noise would have been outside the spacecraft, in the silent near-vacuum of the Moon, no?

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"A witty saying proves nothing." Voltaire

The sound could be transmitted by the LM itself.
The noise would be produced by the flow of fuel and oxidizer, and the flow of expelled gas, against the engine.
However, I do not know whether the burning was explosive.

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papageno


"Why waste time learning, when ignorance is instantaneous?" - Hobbes (Calvin and Hobbes)

"It's all about context!" - Vince Noir (The Mighty Boosh)

"I've never heard of such a brutal and shocking injustice that I cared so little about!" - Zapp Brannigan (Futurama)

He must leave his car running all the time with a brick on the gas petal. Since they have landed why would the engine be at full throttle?

What? Are you trying to be reasonable? :wink:
Unfortunately, it does not work for HBs.

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papageno


"Why waste time learning, when ignorance is instantaneous?" - Hobbes (Calvin and Hobbes)

"It's all about context!" - Vince Noir (The Mighty Boosh)

"I've never heard of such a brutal and shocking injustice that I cared so little about!" - Zapp Brannigan (Futurama)

I remember there were time delays in the audio. But is it possible the HBer's may be using edited versions from some documentary? Or, in many cases I can imagine that the answer might have been initiated somwhat before the question or comment was completed by Houston - especially if it was on a pre-defined check-list that would have been virtually memorized or on the arm of the Moonwalker. For instance - if Houston said "take the hammer...(response begins)...out of the holder" Response being something like "Roger, Houston, hammer is out". There would be no apparent delay.
The evidence would have to be pretty overwhelming here (hear?)
Just as plausibly all of the Houston controllers were actually on the moon also, in one of those alien ships negating any time differential :^)

Kilcullen's explanation does not seem correct.

The audio for the telecasts was simply the air-to-ground loop with occasional interjections by NASA public affairs officers (PAO). With few exceptions, that's the audio we get in all historical records. The only differences are in the synchronization between audio and video, which in some cases (e.g., with 16mm film) is a best guess. Specifically absent is any synchronization adjustment between controller and pilot.

The controller's transmission was not recorded as an echo on the downlink. It was recorded simultaneous with its injection to the uplink. There are anomalous controller echoes on the downlink occasionally, due to improper acoustic coupling in the astronaut's headset. But these are not primary recordings; they are echoes of transmissions that had been recorded 2.6 seconds previously when they originated.

Few conspiracists actually cite examples of transmissions they believe contain improper delays. The cited examples fall into these categories:

1. Improper point-of-view interpretation. This is what we've been discussing. The audio records the controller's point of view, not some mythical objective point of view. No delay is expected between and astronaut's question and a controller's response.

2. Misidentification of speaker. The conspiracist is not always clear whether the CAPCOM is speaking or the pilot is speaking, so in conjuction with the previous category he is not able properly to determine where delays are expected.

3. Improper characterization of conversation. Not all radio transmissions fall under the heading of call and response. Simply because an astronaut begins to speak shortly after a controller has spoken does not mean the astronaut is responding specifically to the controller's statement.

4. Improper differentiation of simultaneous threads of conversation. Occasionally the crew and controllers work into a pattern where two or more "threads" of discussion are underway in a single conversation, and responses appropriate to one thread are interpreted as part of a different thread. This was especially prevalent during J-mission EVAs.

5. Incorrect estimation of spacecraft range. A few examples of anomalous "short" delays occurred when the spacecraft was en route to the moon and still very near Earth, thus reducing the light travel time. The 2.6-second round trip applies only to communications at lunar orbit distances.

6. Improper expectations for intervehicular conversations. A common example is the LM checklist carried out prior to DOI and PDI, in which rapid-fire exchanges occur between the CM and the LM, which at the time are only a few miles apart. No delay is expected, since these two pilots can hear each other instantly. The controllers on Earth, however, hear the entire conversation delayed, but with the relative intervehicular timing preserved.

7. Improper assumptions of protocol. Astronauts and controllers are used to following several conversations at once on radio and intercom links and generally do not respect the lay convention of waiting until the other person has finished speaking in order to prepare a response. It is not always necessary to measure the delay beginning at the end of the controller's statement; it is usually more helpful to being counting when enough of the controller's intent has been communicated in order to suggest a response.

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Clavius Moon Base

The noise laymen associated with the firing of a rocket motor is actually the impact of the exhaust plume with the surrounding atmosphere. The rocket itself does not make much noise.

During ignition you get an ignition transient, which is usually described as a percussive "popping" sound. These transients generally last less than a second even for large pressure-fed motors. Ignitition transients run into 8 seconds for large pump-fed motors, but there is not generally a transient sound associated with long transients.

At steady-state combustion there should be almost no noise -- certainly not the roar or rumble associated with an atmospheric firing.

Acoustics in rocket motors generally fall into three categories:

1. Chugging (10-400 Hz). This is the frequency at which pogo oscillations occur, and is concentrated at the 10-50 Hz range, which generally falls below the threshhold of human hearing. You would feel this vibration in the spacecraft structure, but you wouldn't necessarily hear it. Typical causes include engine-vehicle force coupling and large-scale propellant flow problems. Chugging is solved by adjusting the mass properties of the vehicle and the fluid flow paths of the propellant. The LM would not be especially susceptible to this effect because of its small size.

2. Buzzing (400 Hz - 1 kHz). A well-designed engine will have a bit of this, but generally this is a low-energy vibration. Because one of its primary causes is flow throuh the injector manifold, and because the LM descent engine's injector manifold was not optimal at all throttle settings, this is where I would expect the majority of the DPS acoustic signature to lie. This category corresponds roughly to the sound pitches of the male human voice, and so it could be heard if produced at sufficient amplitude. But as I said, design struggles hardest to mitigate buzzing because this is also the frequency at which structures begin to break.

3. Screaming (1 kHz and above). This is most frequently encountered in new thrust chamber development and is independent of propellant feed and structural issues. Rockets generally cannot be released to production use if screaming persists at measurable energies. If audible energies above 1,000 Hz were produced, the DPS would likely have destroyed itself.

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Clavius Moon Base

Thank you for the detailed explanation. 8)

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"A witty saying proves nothing." Voltaire

...and, even that portion which is within the range of human hearing (could be heard by the astronauts) would still be below the range of a microphone that is optimized for speach (100-3kHz).

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Noise-cancellation microphones -- those that do not adapt to incoming waveforms -- are tuned not only to admit only certain frequencies, but only those sounds above a certain amplitude.

One of the astronauts called their microphones "tonsil mikes" because he quipped they had to be placed down his throat in order for his voice to be loud enough to activate them.

Plume impingement noise is simply irrelevant in this question, and that's what almost all a rocket's noise is. The acoustic signatures I detailed above have drastic engineering consequences and so are predictably mitigated as much as possible. The simple truth is that if an engine makes a lot of audible noise while firing at steady-state in a vacuum, then something is wrong with the engine. Some engines are poorly designed yet functional, and those engines make noise. But the expectation that any joe random engine should make a deafening roar in a vacuum is pure hogwash.

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Clavius Moon Base

Let us add an 8th category to your list of transmission delay examples, or more accurately a sub-category of number 5, Jay:

Improper identification of mission. Anyone here remember Plautus over on the Yahoo group giving us a whole load of examples of 'anomalous' short delays from the Apollo 9 flight?

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"The very powerful and the very stupid have one thing in common: They don't alter their views to fit the facts, they alter the facts to fit their views." The Doctor, Doctor Who: The Face of Evil.

Well, I would classify Apollo 9 as a spacecraft range mistake. The fact that Apollo 9 never left Earth orbit is simply the means by which we know the spacecraft was close to Earth for any given conversation.

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Clavius Moon Base

Listen to some of the audio, for instance of the Apollo 11 landing.

The astros frequently begin to talk, then stop as they are "interrupted" by CAPCOM.

In fact, you can hear the echoes, when CAPCOM would say something, then you hear his voice over the open channel when the astros would talk.

However, the big question is why anyone would believe that the people doing a coverup wouldn't think of speed-of-light lag, which was a fixture in science fiction since the 1930s.

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The Critic-at-Arms writes a (kind of) weekly opinion column, covering a wide range of topics. Maybe even this one! www.sierratimes.com/critic.htm

Buzz Aldrin to Bart Sibrel: Allow me to explain something about rocket engine technology to you. It's an effect called "buzzing".

Sibrel: Huh?

Aldrin: It's simple. First, I'm Buzz. Second, here's a zing!



Sibrel: Ow, that Hertz!

Complete video.

For his crimes against science, truth, and real heroes, I'd say ol' Bart deserves between 400 to 1000 Hertz.

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Hey, I love the video! Too bad it isn't clearer, though.

Look at the relative sizes and ages, and the distance between the attacker and Buzz, and it's clearly a case of self-defense.

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I'll settle for 400 to 1000 Hurts.

Well, we'll just have to get the principals back on location and reshoot it. Of course,