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General Discussion

16870 threads, 325775 comments (2 Viewing)
Views: 113, Comments: 21
Last comment 05/28/2022 by canadianslidewinder
 

Lithium Sulfur Batteries

05/25/2022 by Rixter
This looks promising... https://www.youtube.com/watch?v=ln5u-DETWS0 https://www.youtube.com/watch?v=H-AjRrGglCE
Views: 64, Comments: 3
Last comment 05/26/2022 by PWSlack
 

RoboRat vs RatDroid

05/24/2022 by HiTekRedNek
I recently read about a robot,shaped like a rat for exploring confined,small areas where access is not practical or impossible other wise. Over 20 ye...
Views: 130, Comments: 12
Last comment 05/25/2022 by SolarEagle
Views: 141, Comments: 11
Last comment 05/26/2022 by SolarEagle
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Commercial Space

2113 threads, 4308 comments (0 Viewing)
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CR4 Feedback

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Section Blogs

Challenge Questions

412 blog entries, 30332 comments (0 Viewing)

Beer Can Blueprints (May '22 Challenge Question)

04/30/2022
What are the practical reasons to have concave and beveled bottoms on beer cans? (Okay, so it applies to soda pop cans too.) The image is of a flat-b...
Views: 798, Comments: 26
Last comment 05/23/2022 by Anonymous Poster

A Spicy, Open-Ended Design Solution (April '22 Challenge Question)

03/31/2022
This month's question is a bit different. Rather than a single specific answer, or set of answers, this one challenges your critical thinking. You ha...
Views: 506, Comments: 14
Last comment 04/22/2022 by canadianslidewinder
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CR4 Welcome Wagon

7 blog entries, 20 comments (0 Viewing)

Be excellent to each other

11/21/2021
In recent weeks we’ve talked about eliminating political discussions, reporting things to moderators and also rating threads and comments. If e...
Views: 187, Comments: 11
Last comment 01/09/2022 by phoenix911

Moderator Justice

11/20/2021
This is CR4: Moderator justice The moderators and administrators of CR4 are employees of Globalspec, and [a small] part of our job is to keep CR4 run...
Views: 74, Comments: 0
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Other Blog Entries of Interest

Pesky Ellipse Circumference

10/04/2020 posted in Relativity and Cosmology
by Jorrie
When I first heard that there is no easy exact formula for the circumference of the standard ellipse, I found it hard to believe. I had already learne...
Views: 398, Comments: 8
Last comment 11/30/2020 by Haymaker

SpaceProperTime Diagrams and the Central Singularity

08/24/2020 posted in Relativity and Cosmology
by Jorrie
In my prior Blog post on the Einstein equivalence principle, I have not identified important values, like the mass of the black hole, real distances a...
Views: 287, Comments: 4
Last comment 08/25/2020 by Jorrie

SPT-Acceleration and the Equivalence Principle

08/17/2020 posted in Relativity and Cosmology
by Jorrie
One day after Alice's arrival at Deep-2, she and Dot sat down for the change of shift briefing - recall that Dot must soon return for Home leave. Whil...
Views: 170, Comments: 8
Last comment 08/18/2020 by Jorrie

Space-Propertime Structure and Acceleration II

08/11/2020 posted in Relativity and Cosmology
by Jorrie
This is a fanciful little scenario for 'flexing the muscles' of acceleration in space-propertime a little and so giving a better intuitive feel for th...
Views: 182, Comments: 8
Last comment 08/18/2020 by canadianslidewinder

Space-Propertime Structure and Acceleration

08/07/2020 posted in Relativity and Cosmology
by Jorrie
I have introduced the idea of Epstein Space-Propertime Diagrams (ESPD) in my previous Blog post. To refresh, here is the ESPD's structural relationshi...
Views: 225, Comments: 6
Last comment 08/08/2020 by Jorrie

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