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41

The Reality of Apollo / Command module/Service module connection

« Last post by Peter B on March 08, 2025, 03:06:18 AM »

Were there any connections between the CM and SM which passed through the CM's heat shield?

I don't think so, but a conservator in this Adam Savage's Tested video thinks it was. Savage is looking at the A11 CM sitting on a cradle, and the CM appears to be bolted to the cradle through the heat shield. The conservator says that these were "the same bolt holes that were used to attach it to the Saturn 5 rocket".

It occurs at about a minute into this video:

Thank you!

42

The Reality of Apollo / Re: Apollo 11 and 17 imaged by South Korea

« Last post by onebigmonkey on March 06, 2025, 01:35:41 PM »

Apollo 15 imaged February 22 last year, released today. This is the calibrated version, the RAW file is flipped horizontally.

43

The Reality of Apollo / Re: Everyday Astronaut video about Apollo

« Last post by JayUtah on March 06, 2025, 11:18:20 AM »

Rockets had been a practical reality for some time by then. The Hale rocket was available starting in the mid-1800s as a gyrostabilized missile that could be fired from a breech-loaded canon. They weren't very accurate. Nevertheless, the notion of constraining a rapid combustion was nothing new, and the mass production of a practical (if dubiously effective) rocket had already occurred.

Tsiolkovsky gets the most credit in my estimation for being an excellent physicist. It's one thing to experiment and note results that you can then harness. It's another thing to understand, quantify, and characterize the elementary principles by which something operates. He answered the question, "What's really going on here?"

44

The Reality of Apollo / Re: Everyday Astronaut video about Apollo

« Last post by Dalhousie on March 05, 2025, 11:38:06 PM »

Its astonishing to me that Konstantin Tsiolkovsky published his Rocket Equation in May 1897, over six years before the Wright Brothers flew, and almost 30 years before Robert Goddard launched the first liquid fueled rocket.

He must have been some engineer!

"Just" a humble school teacher!

45

The Reality of Apollo / Re: Everyday Astronaut video about Apollo

« Last post by smartcooky on March 03, 2025, 04:02:37 AM »

Its astonishing to me that Konstantin Tsiolkovsky published his Rocket Equation in May 1897, over six years before the Wright Brothers flew, and almost 30 years before Robert Goddard launched the first liquid fueled rocket.

He must have been some engineer!

46

The Reality of Apollo / Re: Everyday Astronaut video about Apollo

« Last post by bknight on March 02, 2025, 08:32:50 PM »

After sleeping I reran the video and I have a question concerning Tim's calculations concerning the rocket equation.  In all of his calculations Tim used the Earth's gravitational constant of 9.8 m/sec^2.  I wonder if the Moon's gravitational constant should be used for the CSM/LM while entering/leaving Lunar orbit and the LM's landing/takeoff.  What's the verdict?

Short answer: no, you don't change g₀ to be that for the Moon. This comes up all the time while teaching rocket science. A moment's thought reveals that specific impulse and exhaust velocity have nothing to do with the gravity of anything your rocket might be operating near. All that works in deep space too.

g₀ appears in the rocket calculations to normalize the answer for differences in physical measurement units. "Specific" anything in science wants to be as dimensionless as possible. So something labeled "specific impulse" should be considered dimensionless even though it has units in seconds. To get there, you have to do undo all the physically-based measurements such as for mass, velocity, and force. Time in seconds is the only common thing in that relationship among all the measurement systems, so the physically-measured quantities are normalized to a "specific" quantity using something that exists as the same conceptual relationship in all systems. This is arbitrarily chosen to be Earth's gravity-based acceleration. It's a relationship that's defined in all systems and incorporates units of force, mass, time, and velocity—the quantities we care about when trying to measure rocket performance in terms of propellant behavior.

It's important to understand that this is arbitrary. It doesn't have anything to do with operating a rocket near Earth or anything to do with what the Earth's gravity is doing to the rocket. If you're working in SI, you undo the normalization for your units by using g₀ in SI units. If working in EES, you undo the normalization for pounds-force, gallons, firkins, and cable-lengths by applying g₀ in EES units to get exhaust velocity (for example) in feet per second instead of meters per second.

Short answer, ok.

47

The Reality of Apollo / Re: Everyday Astronaut video about Apollo

« Last post by JayUtah on March 02, 2025, 01:02:52 PM »

After sleeping I reran the video and I have a question concerning Tim's calculations concerning the rocket equation.  In all of his calculations Tim used the Earth's gravitational constant of 9.8 m/sec^2.  I wonder if the Moon's gravitational constant should be used for the CSM/LM while entering/leaving Lunar orbit and the LM's landing/takeoff.  What's the verdict?

Short answer: no, you don't change g₀ to be that for the Moon. This comes up all the time while teaching rocket science. A moment's thought reveals that specific impulse and exhaust velocity have nothing to do with the gravity of anything your rocket might be operating near. All that works in deep space too.

g₀ appears in the rocket calculations to normalize the answer for differences in physical measurement units. "Specific" anything in science wants to be as dimensionless as possible. So something labeled "specific impulse" should be considered dimensionless even though it has units in seconds. To get there, you have to do undo all the physically-based measurements such as for mass, velocity, and force. Time in seconds is the only common thing in that relationship among all the measurement systems, so the physically-measured quantities are normalized to a "specific" quantity using something that exists as the same conceptual relationship in all systems. This is arbitrarily chosen to be Earth's gravity-based acceleration. It's a relationship that's defined in all systems and incorporates units of force, mass, time, and velocity—the quantities we care about when trying to measure rocket performance in terms of propellant behavior.

It's important to understand that this is arbitrary. It doesn't have anything to do with operating a rocket near Earth or anything to do with what the Earth's gravity is doing to the rocket. If you're working in SI, you undo the normalization for your units by using g₀ in SI units. If working in EES, you undo the normalization for pounds-force, gallons, firkins, and cable-lengths by applying g₀ in EES units to get exhaust velocity (for example) in feet per second instead of meters per second.

48

The Reality of Apollo / Re: Everyday Astronaut video about Apollo

« Last post by bknight on March 02, 2025, 09:34:41 AM »

After sleeping I reran the video and I have a question concerning Tim's calculations concerning the rocket equation.  In all of his calculations Tim used the Earth's gravitational constant of 9.8 m/sec^2.  I wonder if the Moon's gravitational constant should be used for the CSM/LM while entering/leaving Lunar orbit and the LM's landing/takeoff.  What's the verdict?

49

General Discussion / Re: Visiting Los Angeles

« Last post by LunarOrbit 🇨🇦 on March 02, 2025, 04:20:49 AM »

I might be wrong, but I think the Getty Museum is in one of the areas that were hit pretty hard by the wild fires. It's still there, but maybe closed to tourism.

50

General Discussion / Visiting Los Angeles

« Last post by Peter B on March 02, 2025, 01:40:39 AM »

Hi everyone

Thanks to a couple of things coming together, it's possible I might be able to visit LA for a week or two in June this year with the family (17, 14 and 12).

We're likely to be fairly limited to LA and surrounds, so I wanted to check with the Brains Trust here on things worth visiting and things worth avoiding.

So far, things I've put on the "visit" list are:

- California Science Center
- La Brea Tar Pits
- Dodgers baseball game
- USS Iowa
- Griffith Observatory
- One of the movie studio places
- Getty Museum

I'd like to work out a way to include a Grand Canyon visit (I see there are 5 day train tours from LA), and my wife thinks the kids would love Disneyland.

Would anyone like to add to or subtract from the list?

Thank you very much!