I actually win one with Hunchbacked

[ka9q]

Hunchbacked just put up a video supposedly exposing all the 'incoherences' in the Lunar Module's electrical power system.

He devoted a whole section to his computation of the lifetimes of the ascent and descent stage batteries. He took the stated ascent energy capacity (17.8 kWh for two batteries), voltage (28V) and typical load current (50A/battery) of an ascent battery and computed:

Power drain = 28 V * (50A)² = 70 kW * 2 batteries = 140 kW [sic]

17.8 kWh / 140 kW = 7.62 minutes

and then triumphantly concluded that the batteries could not possibly handle the requirements of an LM ascent, thus proving Apollo was faked. Wow.

Hunchbacked's videos always provide a "target-rich environment" but I didn't even know where to begin with this one. For the non-EEs out there, power is volts times amps, not volts times amps squared. A load of 100A at 28V is therefore 2.8 kW, not 140 kW. At this rate, the ascent batteries would last over 6 hours, not 7 minutes.

I gleefully pointed out that not only should a genius like him know Ohm's Law, but that most normal engineers would at least recheck their own work after getting such an absurd result.

To my utter amazement, within minutes he pulled the video down and sent me a message saying "I acknowledge my error, but it remains absurd".

I would like to read this as saying that his error remains absurd, with which I certainly agree, but I don't think that's what he meant.

[Chew]

You have to wonder while he was writing that formula if it occurred to him why is electricity bill was so low.

Too bad you didn't download his video and share it.

[ka9q]

Actually, I did download it. Where would you like it?

edited to add: Here you go. enjoy:

http://www.ka9q.net/The_special_power_subsystem_of_the_lunar_module-360p.mp4

[Chew]

Excellent! Thanks.

[ka9q]

One of his masterpieces.

[ka9q]

He's got a revision up; the bogus P=VI² Ohm's Law stuff is now silently down the memory hole. But to save face he replaces it with a few other misunderstandings regarding voltage drop in batteries under heavy load, and displays his ignorance of Peukert's Law. Admittedly that's more specialized than Ohm's Law, but it's still something everyone should know who purports to be knowledgeable about batteries.

And of course all the rest of his howlers are still there, including his claim from an earlier video that the ascent stage was deliberately imbalanced by the asymmetric propellant tank placements.

[Tedward]

I have a vague understanding of batteries and consider it a dark art. Peukert's Law is something I have touched on but not really understood. I know (I think I know!) different battery construction is used for differing purposes, e.g. a car battery needs to gives it all when you turn the key as opposed to a UPS battery that needs to let it out at a measured rate over a period of time.

Or have I got it all wrong?

[ka9q]

Peukert's Law is a property of every battery I know - it relates the amp-hour capacity to the discharge rate. The more quickly you discharge the battery, the fewer amp-hours you get out of it before it goes flat. The generic formula is

effective discharge rate ~ I^p

where p is the Peukert exponent. That is, the effective discharge rate is proportional to a power of the actual discharge rate. The exponent p varies with battery chemistry and construction. p=1 means no Peukert effect at all, but for real lead-acid batteries it's typically 1.1-1.3.

This is why battery specifications give tables showing amp-hour capacity as a function of either the discharge current or the number of hours over which the battery is discharged.

The Lunar Module used silver-zinc batteries, but Peukert's law (with different values of p) applies to every battery I know of.

[theteacher]

For the non-EEs out there, power is volts times amps, not volts times amps squared.

It's part of the curriculum for 9'th graders 

[qt]

For the non-EEs out there, power is volts times amps, not volts times amps squared.

It's part of the curriculum for 9'th graders 

Perhaps this slightly confused individual tried to use a formula expressing power in terms of current and ohms, thinking the latter were similar to volts.

[ka9q]

Yeah, that occurred to me too. He was thinking of I²R.

He posted and has now taken down a second version of the video.

[gillianren]

It's part of the curriculum for 9'th graders 

Not when I was a ninth grader.  We took health class that year.

[Noldi400]

It's getting harder and harder for me to believe that hunchbacked is serious and not just pursuing one long-running joke mocking the hoaxer community.

He does at least provide some amusement, mostly because he is constantly coming up with claims that are not the same old tired parroting.

But he seems to be working his way through all the available documentation about Apollo and finding "incoherencies" in each and every one. Not too long ago he even said that when he looks at one of the photos or videos he knows that if he looks long enough he will find an 'incoherency".

Even if one assumes (for the sake of argument) that the landings were hoaxed,  is it reasonable there would be something evident in EVERY piece of documentation? I don't think so.

[ka9q]

he even said that when he looks at one of the photos or videos he knows that if he looks long enough he will find an 'incoherency".

"long enough"?

[gillianren]

Doesn't he mean "inconsistency"?  Hoax believers never know science; is it too much to ask that they maybe understand English?