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For kbd512 re move of phpBB3 site from Azure to Mars Society...
I created an account for you to explore the phpBB3 site and sent the password by email.
I'm hoping we might be able to set up the site as a / extension from NewMars.com
For example, perhaps? NewMars.com/images
As a reminder, the address for the images site is: http://40.75.112.55/phpBB3/
We have until November 15th to complete the transfer.
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tahanson43206,
If I understand the request correctly, I'm going to install / publish the phpBB3 web app on our NewMars web server.
What about database requirements?
Do I need to install and configure a database schema on our MySQL Server as well?
Is this a "standard" phpBB3 setup, or have you customized the phpBB3 web app or the database schema in any way?
I'm talking about editing the php files or database schema tables and objects, not any photos you've added.
Edit:
This web app is purely for local storage of user-generated media files, such as the rocketry-related PowerPoint presentations / photos / videos created by GW Johnson, correct?
Last edited by kbd512 (2025-10-20 08:25:27)
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For kbd512 re #327
Thank you for following up on my request to see if it might be possible to install the phpBB3 forum package on the Mars Society server. The application has been running for some time on the Azure test site. I ** think ** it should be possible to simply zip the database and install it at the Mars Society server, since the database has already been configured to look like the existing FluxBB system. The first step would be to install the software and see if it can be called using newmars.com/images
If that works, then we can consider whether we want to copy the database or start with the new empty database.
I assume/hope that 99% of the work is installing the phpBB3 package. At the web site for phpBB3 there are multiple versions. I am hoping we can replicate what we have on the Azure site.
I added your ID to the Azure site so you can log in and get a sense of how the package works.
The password was emailed to the email address I have on file.
Note for SpaceNut: If this works, we will need to edit the links to the Azure site. There may be a way to find all occurrences of the address and update them in a single operation. Otherwise can can perform the edits manually.
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For kbd512 ...
Just FYI ... the Azure system is stopped so I can discover why it is not responding.
It is possible it is under unusual demand on the apache2 system due to outside inquiries.
In the mean time, we are unable to serve the 30 or so images we set up for display on the NewMars forum.
If you can schedule some time please see if you can install the phpBB3 package at Mars Society.
I will try to gain control of the Azure system later today, but in any case it is going away in November.
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For kbd512 ...
First, thanks for the two updates about thermal heating studies ... I've updated the index to point to them.
Second, I connected with the Azure system last night and opened MySQL ... it opened and looks the way I remember it. I'll work on creating a mysqldump of the phpBB3 database today. I think there is at least one file you need for configuration, so I'll look for that as well.
Third... thanks for helping with the meeting Sunday. I thought it went well and we are well positioned to move forward.
Your two contributions to the Google Meeting topic sure are encouraging. However, there's a long road ahead to reach the goal you've set.
Update: I just found Post #368 (hiding behind the two on thermal systems).
It looks (to me) as though your specifications would yield a workable design. I note the 200:1 expansion ratio.
If you have time, please add a line to Post #368 that shows the diameter of the cone at the rim. Don't change anything that is already present. What I'm hoping for is something that is a bit easier for someone to read.
More importantly, I'm hoping for numbers that can be plugged right into Blender to generate the desired shapes.
For example, a presentation might look like this:
Throat specification:
Diameter of throat: 2.5 cm
Throat is inside of torus so we need the diameter of the torus and the diameter of the ring of the torus.
The diameter of the ring of the torus was given by GW Johnson in the rocket design image.
Expansion bell specification:
Diameter of cone at merge with throat: ??? cm
Diameter of rim: ??? cm
Length of frustum: 40.471 cm << this is for reference. It is NOT a design input.
In other words, if you were designing the structure using a 3D design package, you would want specific numbers to help the software to create the shapes you want to combine into the finished form.
If you were preparing instructions for someone to create the model you want, you can help them by setting out the numbers with labels that are clear. For planning, it is good to know which numbers are drivers of the process (eg, diameter) and which are generated (eg, frustum).
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tahanson43206,
Diameter of Cone at Merge with Throat (same thing as Throat Diameter): 2.5cm
Diameter of Rim (Nozzle Exit Diameter?): 25.232cm (radius * 2)
Length / Height of Frustum: 40.471cm
Divergence Angle of Nozzle: 15 degrees
Length / Height of the frustum is a derived value, yes, but does your student know how to derive it?
If I was working with a CAD software package, I would want to know Aexit and Divergence Angle to create a cone shape with the desired dimensions. From there, I can then figure out where to "slice the cone" for Athroat = 2.5cm^2, to give me the desired 200:1 expansion ratio. GW determined what the surface area of Athroat needed to be, roughly speaking, for the desired flow rate and pressure.
Using only Aexit = 500cm^2, Athroat = 2.5cm^2, and a 15 degree Nozzle Diverge Angle, presuming I know a little trigonometry to derive the height of the cone, meaning exit radius / triangle base length * tan(90-15) and formula to derive radius from the surface area of a circle, meaning sqrt(Aexit/pi), then I have all the info I need to create a frustum with the desired dimensions.
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For kbd512 re #331
Thanks for the additional clarifications and details!
FYI ... I just heard back from the party who I am hoping to interest in working with Blender to create the model. I have offered the opportunity to develop the 1:200 ratio version you would like to see, and the 1:100 version that GW would like to see. I am willing to test both using the OpenFOAM system. Now that we have the Merlin engine working, I should be able to create duplicate projects with the new respective mesh, and run the exact same scenario against the new mesh. I am expecting to see dramatic improvement of pressure with the smaller throat. I would expect the difference between the expansion ratios to be less dramatic but still measurable.
If the opportunity presents itself, I will try to set up a learning opportunity for those who are not familiar with Blender. It will also be a great opportunity for the presenter to build up presentation skills. Your working schedule is going to be difficult to work with, but I'll try to set something up.
What we might do (just thinking at this stage) is set up topics for the two different designs, so interaction with the developer can be documented, without interference between the two different designs. I expect that as we go along, you are going to want to diverge from GW's design, which I expect to be less likely to change as we proceed.
As a reminder, I have yet to learn how to convert an STL file into an OpenFOAM mesh, so I'm looking forward to working on that.
As an additional reminder, each OpenFOAM run takes on the order of 14 hours now, for a 1/4 second sprint. The development of both these new models is going to stretch out for a few weeks, I expect.
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For kbd512 re phpBB3 port to Mars Society servers...
Today I completed a backup of the phpBB3 database:
-rw-rw-r-- 1 azureuser azureuser 1204003 Nov 11 16:28 phpbb_newmars_2025-11-11.sql
Later today I'll attempt to pull it down to local machine.
Once that is complete, the only thing left for me to do (that I know of) would be to copy whatever configuration files you may need from the phpBB3 directory.
We still have three days to complete preparations for the port.
Update later 2025/11/11 ... The mysqldump file was copied down to local machine. I'll deliver it to Dropbox shortly.
We still have 3 full days and possibly 4 days to collect anything you need from the working phpBB3 directory.
Update: The file is uploaded to Dropbox and the link was sent by email to kbd512.
Update: ChatGPT5 offers this suggestion for when you create the database:
CREATE DATABASE phpbb_newmars
CHARACTER SET utf8mb4
COLLATE utf8mb4_unicode_ci;
I assume you would have done that anyway, but I figure it can't hurt to pass along the suggestion.
I noticed somewhere in all the text I've seen in the past day or so that MySQL was picked up by Oracle?
That may have been true for a while.
I have a book on MySQL that was written by someone who worked with or was close to the gent who wrote MySQL back in the ? 70's ? It sure has come a long way since then, but the book shows the fundamentals have stayed fairly consistent over all those years.
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For kbd512 re reactor coolant lines ...
Thank you for your follow up on the discussion of the post-NERVA studies!
Taking into account the quote you provides specifically says the length of the reactor core varied, and using the number of coolant channels you computed as 5128, I found that the total length of coolant lines for the version that was .9 meters long (90 centimeters) would be 4615.2 meters.
That was up from the 422 meters figure we had been considering yesterday.
I am hoping we can reverse engineer the post-NERVA system (CERMET) to figure out what the flow rate is through each of those 5128 channels, and how much thermal energy is imparted to the hydrogen during that brief passage.
We might even be able to figure out how much time is consumed during that brief passage.
Thanks (again) for doing the research to find that helpful data! I think the key information is the radius of the coolant tubes, which is very small compared to the size we'd been thinking about.
A detail of the design that is not clear (to me for sure) is where the cladding layer goes!
In the post #370 (2025-11-10 00:49:12) the radius is given as 0.1778 cm and the cladding is given as 0.025 cm tungsten.
OK ... I found the clarification... the cladding ** surrounds ** the coolant tubes.
From this I conclude the internal diameter for hydrogen flow is 2 x 0.1778 cm or 0.3556 cm.
Compare that to the size of the CFD model intake! The Merlin intake is 40 cm wide and 0.016 * 2 or 0.032 meter tall (Z dimension)
The wetting area inside that small tube is ** far ** greater than is available in the Merlin Engine.
The statement above could be more clearly written. We are comparing the circumference (wetting area) to the area of cross section. The area is expressed as A = 2 Pi r squared. Circumference is expressed as Pi D or 2 Pi r.
1.11715 centimeters is the circumference of the tube with radius 0.1778 cm.
The area of cross section of that tube is 0.099315 square cm.
The ratio between circumference and area in this case is: 11.25
If we increase radius to 1 cm, then circumference is 2* 3.14159 cm
The corresponding area is Pi r squared so 3.14159. The ratio of circumference to area is 2.
The smaller tube has an advantage of 11.25/2 or 5.625 over the larger one.
I asked Gemini to prepare a better explanation of the improved wetting performance as the diameter of the tube decreases.
I hope that GW Johnson is able to allocate some time for study of the 0.3556 cm diameter tube and the related conditions.
The CERMET design appears to be raising the temperature of hydrogen from (approximately) 20 Kelvin to 3000 Kelvin over a distance of 90 centimeters (or so). There are just two factors at work here. The gas is under pressure at the intake, and it is subject to convective heating. Those two factors are the ONLY factors that could account for the change in temperature.
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I asked Gemini to consider the radio of diameter / circumference to area of a heating tube.
I note that Gemini refers to the advantage of the smaller tube over the larger one as an "efficiency" advantage.
The smaller tube is more "efficient" at heating the gas than the larger one.
I'd be glad to help you draft an explanation that clearly presents this critical concept for your forum, using only text and BBCode.
Here is the revised passage, focusing on the ratio of Wetting Area (Circumference) to Flow Area (Cross-section Area), which is the key driver of convective heating efficiency.Why Smaller Tubes Heat Better: The Surface-to-Volume Advantage
We are investigating the principle behind the highly successful regenerative cooling channels used in the NASA studies, which utilize hydrogen flow in very small tubes. Our goal is to demonstrate why decreasing the tube's radius dramatically improves the ability to transfer heat into the flowing gas.
The efficiency of convective heating is determined by the ratio of the surface area available for heat transfer (the tube's inner circumference) to the volume of gas flowing through the tube (the tube's cross-section area). This is mathematically known as the Surface-Area-to-Volume Ratio.
Wetting Area (Circumference, C): $C = 2 \pi r$ (Varies linearly with radius)
Flow Area (Area, A): $A = \pi r^2$ (Varies with the square of the radius)The ratio of these two is simplified to $C/A = 2/r$. This inverse relationship shows that as the radius ($r$) decreases, the ratio increases, giving a massive advantage to smaller tubes.
Example 1: The High-Performance NASA Tube
The NASA study uses a tube with a radius ($r$) of $0.1778$ cm.
Wetting Area ($C$): $2 \times \pi \times 0.1778 \text{ cm} \approx 1.117 \text{ cm}$
Flow Area ($A$): $\pi \times (0.1778 \text{ cm})^2 \approx 0.0993 \text{ cm}^2$
Surface-to-Area Ratio ($C/A$): $1.117 / 0.0993 \approx 11.25$Example 2: A Hypothetical Larger Tube
To illustrate the loss of efficiency, consider a hypothetical tube with a much larger radius ($r$) of $1$ cm.
Wetting Area ($C$): $2 \times \pi \times 1 \text{ cm} \approx 6.28 \text{ cm}$
Flow Area ($A$): $\pi \times (1 \text{ cm})^2 \approx 3.14 \text{ cm}^2$
Surface-to-Area Ratio ($C/A$): $6.28 / 3.14 = 2.0$Conclusion
By reducing the tube's radius from $1$ cm to $0.1778$ cm, we increase the surface-to-area ratio from $2.0$ to $11.25$.
The smaller tube offers an efficiency advantage of $11.25 / 2.0 = 5.625$ times over the larger one. This dramatic increase in the amount of surface available to heat a given volume of gas is the primary reason why fine channels are necessary for high-performance convective heating and cooling applications, such as those found in the NASA test studies.
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