Recent Posts

41

General Discussion / Re: Some physics help, please

« Last post by bobdude11 on September 30, 2025, 12:50:00 PM »

Found this documentary on the 'Drip Rifle' - looks like they tied a rock to the lower string a little above the lower can and when the lower can had sufficient weight, it pulled the rock down that in turn pulled the trigger:

EDIT: changed 'the' to 'they' and corrected spelling of 'pulled'

42

General Discussion / Re: Spaceship design - a hypothetical excercise

« Last post by bobdude11 on September 30, 2025, 12:36:45 PM »

... the images I've seen from Alcubierre's work shows something that looks like an elongated football with a ring around it, and I imagine the force of gravity would be oriented in the direction of travel; IOW, you'd be flying feet-first.

Thank you for the detailed explanation - admittedly, I have only a VERY basic understanding of the math, it still makes sense how you describe it! Also to your note, in the series Enterprise, the Vulcan ships are elongated with a warp ring instead of two nacelles. Perhaps a nod to Alcubierre?

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General Discussion / Re: Spaceship design - a hypothetical excercise

« Last post by bobdude11 on September 30, 2025, 12:31:26 PM »

Its not original to the writers of Star Trek. EE Doc Smith used this concept in his "Lensman" series, published in the late 1930's and early 1940's.

I am not familiar with this series - looks like I need to expand my Sci-Fi collection!

44

The Hoax Theory / Re: Watching the detectives...

« Last post by onebigmonkey on September 28, 2025, 07:21:34 AM »

The latest video (not the livestream) is just embarrassing. They look at a picture of the moon and compare it with amateur astronomer images. They're taken under different lighting conditions and are of different resolution, but that doesn't stop them claiming that NASA is adding and/or taking away (delete as applicable) details for, well, who knows. Theu show remnant craters filled with maria material and claim that they're full of dust, so therefore all the Apollo equioment should be covered in dust and invisble.

How Jarrah fails to join in and go "fellas, you're making dicks of yourself and by extension me" I do not know.

Anyway, the main purpose of this post is to completely discredit the absolute falsehoods claimed by straydog2 about China's imaging of Apollo.

In a series of responses he makes several ciaims, mostly after interrogating AI with leading questions and then paraphrasing its results to make it sound like it's the AI answer when in fact it's his.

Here's a few direct quotes:

"[China] did not release any images that clearly show Apollo hardware."

This at least is correct - the Chang'e-2 resolution is not capable of doing htat, no-one ever claimed it did.

"The Chang'e 2 image is an EXACT MATCH for the NASA LRO image because it is a very blurry COPY of that image...the Chinese have the technology to image the entire Moon in high definition and have already done so, with the exception of the Apollo sites.. So instead of publishing high resolution images showing no Apollo debris at the Apollo sites, they have sent a different kind of message, by not publishing any images at all, with the exception of that one blurry image that they obviously did not take"

"What they did was to take the Apollo 16 LRO image, copy it exactly, make it very blurry and then publish it as a way of exposing the Apollo fraud without actually saying it was a fraud."

"The Chinese not only didn't take that photo but didn't publish it either.. Instead, NASA mislabeled their own blurry A16 LRO image in an silly attempt to make it look like the Chang'e 2 had confirmed one of their alleged landing sites!"

So, to be clear, the dog is claiming China have never published any images of Apollo sites, NASA doctored one of their own images and pretended it was from China.

It's prefectly possible to go to the CNSA's webGIS application and download the large scale tiles, on which you can find the evdience of human activity at Apollo sites. Note I'm saying evidence of human activity., not hardware. That evidence is darkened ground around the lunar modules, with occasional hints of trails to sites around them.

Those tiles are compiled from the probe's CCD instrument, and I decided to set about finding those original tiles. Each Chang'e-2 oribt moved on about 1 degree from the previous one, and produced a pair of images from the forward and rear facing camera. The resulting images are roughly 50km wide and 200km long. Each forward and rear facing image has a 'SCI' and 'GEO' files. The GEO file contains detailed meta data, while the SCI file is the image itself. You can open the SCI file in photoshop by first opening it in notepad (or anyother software capable of reading the file header) to get the image dimensions. Those dimensions are always 6151 pixels wide and around 55000-60000 pixels high. Each SCI file is around 350Mb

You can download them here:

https://moon.bao.ac.cn/ce5web/searchOrder_dataSearchData.search

It's a bit of a faff, finding the relevant orbits is a pain, but eventually I tracked down the files for each Apollo site.

Apollo 11:

CE2_BMYK_CCD-B07_SCI_N_20101120165451_20101120185249_0532_A

The time of the image is the long sequence of numbers, and the last 4 numbers identifies the orbit.

Tranquility base covers the smallest area, but had the least amount of activity, so other than identifying where the site is it's very difficult to say with certainty that there's anything to see there. I'm still downloading one of the image pairs while writing this, but I don't expect it to show anything.

Apollo 12:

CE2_BMYK_CCD-B08_SCI_N_20101124092425_20101124112222_0577_A
CE2_BMYK_CCD-F08_SCI_N_20101124092425_20101124112222_0577_A

This is the better of the two



where you can see activity around the LM and Surveyor 3.

Apollo 14:

CE2_BMYK_CCD-B08_SCI_N_20101123213629_20101123233428_0571_A
CE2_BMYK_CCD-F08_SCI_N_20101123213629_20101123233428_0571_A

Here's the better of the two:



Cone crater is top right, and there's a nice dark blob around the site of the LM towards the bottom left.

Apollo 15

CE2_BMYK_CCD-B06_SCI_N_20101122022037_20101122041835_0549_A
CE2_BMYK_CCD-F06_GEO_N_20101122022037_20101122041835_0549_A

CE2_BMYK_CCD-B06_SCI_N_20101122041836_20101122061634_0550_A
CE2_BMYK_CCD-F06_SCI_N_20101122041836_20101122061634_0550_A

Here's the Apollo site from each of them:





Again, clear activity around the LM and suggestions of trails leading elsewhere.

Apollo 16

CE2_BMYK_CCD-B08_SCI_N_20101121083844_20101121103642_0540_A
CE2_BMYK_CCD-F08_SCI_N_20101121083844_20101121103642_0540_A



Activity around the LM and LRV VIP spot!

Apollo 17

CE2_BMYK_CCD-B06_SCI_N_20101120030855_20101120050653_0525_A
CE2_BMYK_CCD-F06_SCI_N_20101120030855_20101120050653_0525_A

The rear facing camera looks to have had some sort of issue right at Taurus Littrow, but the forward one does show this:



That little blob in the middle is where Challenger sits to this day.

So there you are Straydog2. As usual, someone's done all the work for you. China has published images of the Apollo landing sites, you can download them from their website and see for yourself. I've done some quite severe processing on those images to bring out the detail, but even without that the darkened ground around the LM on the multi-EVA sites can be made out once you know where to look.

The issue here is his expectation of how China should be doing it. It's a form of the "If I ran the zoo" fallacy. He thinks China should be making a big song and dance about it, and because they haven't that's somehow proof of his delusions. As with India's Chandrayaan series, they didn't go to the moon to prove Apollo happened. It's an irrelevance. Apollo sites are routinely referenced by Chinese academics in their research, and the location and properties of Apollo hardware were used to "ground truth" their observations: they know where and what they are, so they can check what their instruments are showing.

Asking leading questions of AI software is not going to give you the evidence you need, it's just lazy. It is no substitute for doing the hard work yourself. And sure, you can whine about not being able to see any actual hardware, but here's the thing doggy, you don't get to set the standard of acceptable proof. The fact is there's evidence of human activity right where it was always claimed to be. Prove me wrong.

45

General Discussion / Re: Some physics help, please

« Last post by Peter B on September 27, 2025, 06:48:13 PM »

Brilliant! Thank you both.

I was missing the effect of kinetic energy.

46

General Discussion / Re: Some physics help, please

« Last post by JayUtah on September 27, 2025, 10:40:20 AM »

Potential energy becomes kinetic energy during the fall. The longer the fall, the more kinetic energy. If the can is initially at the same height as the trigger, the first can reaches the end of a string of length L at a velocity



where g is the gravitational acceleration on whatever planet you're on, in whatever system you prefer. Potential energy is



where m is the mass of the water and can. At the end of the fall, all that potential energy is converted to an equivalent amount of kinetic energy



thus



Mass cancels, and algebra lets you solve for velocity in terms of height. There are, of course, more straightforward ways of determining the velocity of an object at the end of a fall. But using the energy formulation helps you understand where the energy comes from and therefore why work is required to stop a falling object.

The exact force imparted to the trigger depends on the elasticity of the string and therefore the stopping distance. But the "extra" force beyond the mere static weight of the can is necessitated by the kinetic energy obtained in the fall.

A half-liter can falling 10 cm and stopping in 1 cm produces an average force across that distance of around 50 N, which is about twice the nominal trigger pull force of a 1903 Springfield rifle such as those issued to American soldiers in World War 1.

47

General Discussion / Re: Some physics help, please

« Last post by rocketman on September 27, 2025, 01:11:30 AM »

I'm not sure whether any non-Australians here are familiar with the "drip rifle", a modification of a standard British rifle developed by an Australian soldier at the end of the Gallipoli campaign in December 1915.

The drip rifle involved tying one end of a piece of string to the trigger of the rifle, and the other end to a can. Water dripped from a second can into the first, and when the first can filled up enough, it fell, pulling the string and thus the trigger. By varying the rate at which water dripped into the first can, the amount of time before the rifle fired could be varied.

The modification was applied to a couple of hundred rifles set up along the trench line. The objective was to maintain a low level of rifle fire through the night of the final evacuation, to fool the Turkish soldiers into believing there were still soldiers in the Australian trenches.

Anyway, in one video online, some people are saying the device wouldn't work as claimed. They say that the weight required to pull the trigger normally was several pounds, and it wouldn't be possible to have cans hold that weight of water.

Instinctively, that doesn't make sense to me - the trigger was pulled by the weight of the can of water falling, which seems different to the pressure exerted by a finger. But I don't know how to explain the difference.

Can someone please explain the different forces involved to numpty me, and why a falling can of water doesn't need to have the same mass as the force needed to pull the trigger?

Thank you!

Cheers

Peter

I’m trying to work out the details here.  How does the can fall?  Is it supported by some weak material that breaks when the can reaches a certain weight?

E.g., what, maybe hang the can with a short, weak string that breaks at some point, but then also have a second, longer string attached to the trigger?

In any event, the force is the weight of the can, plus the force needed to decelerate the can from its falling speed to zero.  That force will depend on the physical properties of the string.  If it’s really stretchy and elastic, the deceleration will take place over a longer period of time, and the force won’t be that great.  But if it’s a very non-stretchy string, the deceleration will be very fast, and the force will be high; in this case, the weight of the can would not have to be that much.  But the force needed to pull the trigger would have to be less than the force that breaks the string.

48

General Discussion / Some physics help, please

« Last post by Peter B on September 26, 2025, 09:47:34 PM »

I'm not sure whether any non-Australians here are familiar with the "drip rifle", a modification of a standard British rifle developed by an Australian soldier at the end of the Gallipoli campaign in December 1915.

The drip rifle involved tying one end of a piece of string to the trigger of the rifle, and the other end to a can. Water dripped from a second can into the first, and when the first can filled up enough, it fell, pulling the string and thus the trigger. By varying the rate at which water dripped into the first can, the amount of time before the rifle fired could be varied.

The modification was applied to a couple of hundred rifles set up along the trench line. The objective was to maintain a low level of rifle fire through the night of the final evacuation, to fool the Turkish soldiers into believing there were still soldiers in the Australian trenches.

Anyway, in one video online, some people are saying the device wouldn't work as claimed. They say that the weight required to pull the trigger normally was several pounds, and it wouldn't be possible to have cans hold that weight of water.

Instinctively, that doesn't make sense to me - the trigger was pulled by the weight of the can of water falling, which seems different to the pressure exerted by a finger. But I don't know how to explain the difference.

Can someone please explain the different forces involved to numpty me, and why a falling can of water doesn't need to have the same mass as the force needed to pull the trigger?

Thank you!

Cheers

Peter

49

General Discussion / Re: Spaceship design - a hypothetical excercise

« Last post by smartcooky on September 26, 2025, 04:49:08 PM »

In Star Trek, they have control over inertia, and therefore it's not really how fast they CAN accelerate, but how fast they WANT to accelerate. According to DS9 S01E01, the warp field can lower the inertial mass of the object inside it.

I remember that and thought it was an interesting take on warp drive. Until that explanation, I always thought the warp "bubble" was meant to move space instead of the ship, hence the idea of "folding space" around the ship.

Its not original to the writers of Star Trek. EE Doc Smith used this concept in his "Lensman" series, published in the late 1930's and early 1940's.

It was called the "Bergenholm Inertialess Drive", which allowed his spaceships to achieve FTL travel by nullifying, or almost nullifying, inertia (essentially, reducing mass to near zero) so that effectively any thrust would result in the spaceship's near-instant acceleration to near or beyond light speed. Because mass was so dramatically reduced this would result in two things
1. The crew would feel little or no acceleration.
2. A workaround for the problem of relativistic increase in mass to infinity as you approach light speed.

It did have a drawback though.

If a ship were to approach a planet, its lack of mass would mean it could not go into orbit. It would have to power down its "Bergenholm Inertialess Drive" and upon regaining it is mass, it would also regain the original velocity AND vector it had before the drive was turned on (which could be any velocity in any direction) a figure that would almost certainly be significantly different from that that of the planet. This could result in the spaceship instantly tearing away (or towards) the planet at velocities measured in tens of thousands of km/sec, possible colliding with the planets, and certainly turning all the ship's occupants into pink paste. Therefore, prior to shutting down the drive, ship was required to match its natural "intrinsic velocity"[/i] to that of the planet (it is never explained how this was done)

50

General Discussion / Re: Spaceship design - a hypothetical excercise

« Last post by jfb on September 26, 2025, 11:33:17 AM »

wouldn't the sheer mass prevent the ship from traveling beyond a certain speed or possibly not even able to move at all?

Even an itty-bitty ion thruster imparting a fraction of a Newton will eventually get it moving to relativistic speeds, it's just a matter of how long you're willing to wait and how much propellant you have available.  Munging the Tsiolkovsky equation a bit, you can compute the propellant mass as



So if the Enterprise masses, say, 1.9 x 10^8 kg per one online estimate (m_dry), and we want it to go 0.5 c (delta v), and our itty-bitty ion thruster has an exhaust velocity of 50,000 m/s (v_e), then we'd need on the order of e²⁹⁹⁸ kg of propellant. 

That's ... a lot (my calculator overflows on it). So, yeah, practically speaking, getting something as big as the Enterprise moving would be a challenge. 

I am not fully clear how the impulse engines would work, but it seems that they would have to put out quite a bit of energy to move the ship with any significant speed

It's never really explained exactly how impulse engines work.  Given the name, it's strongly implied it's some kind of reaction drive, but God knows what the actual mechanism is.  It could be a fusion drive sort of like what's used in The Expanse (at least the TV version); a pellet of deuterium wrapped in a lithium (I think) shell, blasted by lasers to induce fusion, reaction products are directed out of the engine at near light speed.  Low mass, but super-high velocity, providing a pretty good push.   

But again, it's never really explained, and like with the itty-bitty ion thruster the fuel necessary would likely out-mass the rest of the ship by a lot.   

The genius of warp drive (at least as commonly envisioned) is that you aren't moving very fast at all relative to local space; you're warping spacetime to bring your destination closer to you and push your departure point away from you.  The mass of your vessel is almost irrelevant.  And, what many people seem to miss is that if you can warp spacetime, then you get artificial gravity and inertial damping for free¹. 

It's a big "if", though.  The math works, sure, but the energy requirements are on the far side of feasible.  I know people have been refining Alcubierre's work to bring that energy requirement down, but it's still more than we can realistically generate or harness with any near-term technology.  There's a reason Trek hand-waved it away with anti-matter. 

• Although the Enterprise wouldn't be shaped like that; the images I've seen from Alcubierre's work shows something that looks like an elongated football with a ring around it, and I imagine the force of gravity would be oriented in the direction of travel; IOW, you'd be flying feet-first.