kbd512 Postings

tahanson43206 · 2024-10-21 17:48:46

For kbd512...

First, thanks for your thoughtful and detailed review of the nickel iron battery that came up for consideration due to an article about the technology. Your history matches up pretty well with the reporter's text.

I am concerned that two or three emails I sent may have fallen into a bit bucket. I sent emails about the FluxBB upgrade we've been working on for the past year and a half, and I've received no feedback at all, including during the Google Meeting on Sunday.

I used the email address I have on file for the FluxBB project, but if you are no longer using that email address I can try sending to another one.

The emails had to do with the config table that must be updated in the FluxBB MySQL database.

(th)

kbd512 · 2024-10-21 21:37:32

tahanson43206,

I did read your e-mails and I did reconfigure the config table and the config.php. When I viewed the page source for the new app, I noticed that the CSS links were working, so they're definitely reachable / downloadable (by the user's browser), but it's as if the PHP code is not actually applying them.

kbd512 · 2024-10-21 21:44:27

tahanson43206,

Whenever I start working with the new app, I get logged out of the old / existing app. Everything superficially appears to be connected, but the PHP code still isn't fully functional. I've looked at the version of the software running, the structure of the app files, the permissions, etc. If there were a permissions problem, then I'd assume I wouldn't be able to access them from the browser, but I can.

I'd really like to get the stylesheets applied correctly first (so the content displays correctly in the browser), and then worry about the database logins, because I don't think our database config change is messing that up. It's something more fundamental than that, such as PHP itself, our particular code base for the new app, or something server config related.

tahanson43206 · 2024-10-22 06:08:19

For kbd512 re FluxBB upgrade...

Thanks for the update on the situation.

If you have access to MySQL, please update the table using the information provided. That way, when you get the more fundamental problem solved, the system will work properly. The database is clearly being accessed, so that means the config table is being accessed. The config table is where the default Fire is defined, but it may NOT be Fire. The important line is the URL pointer. That ** has ** to be fixed.

(th)

kbd512 · 2024-10-22 18:44:29

tahanson43206,

I believe I did that already, but I'll go over what you sent again.

tahanson43206 · 2024-10-28 09:33:16

For kbd512...

This is a long shot, but I thought of it over night ...

The FluxBB system uses cache to save time serving customers.

Since we've altered the database, we might be able to force the software to rebuild the cache by deleting the files in the cache folder.

No harm is done because the system rebuilds cache automatically.

This might work as an alternative to restarting Apache.

(th)

tahanson43206 · 2024-10-31 10:16:35

For kbd512 re Post in Rotating Fuel Delivery topic....

First, thanks for adding your detailed and thoughtful post to the new topic!

Your point about sloshing inside a large tank is important for planners to consider!

As one small (but important) detail for clarification... in GW's plan (as published so far), there are no bearings involved in rotation.

On the contrary, GW's vision eliminates bearings by moving both the supply tank and the customer vehicle out of the immediate vicinity of the station.

I am hoping our NewMars members will help GW to think through how his proposed system would work in practice.

I have tried to identify operational difficulties, but I'm sure I've missed some.

Your addition of the sloshing is helpful, because it clarifies something significant.

If a tank is spun, why would the cryogenic fluid inside the tank spin? Newton would tell us the liquid would remain still while the metal wall of the tank slides by.

Longitudinal baffles might help, but some CFD studies might be needed to optimize the design of tanks to be used for this purpose.

(th)

kbd512 · 2024-10-31 12:10:26

tahanson43206,

In microgravity, centrifugal force acts as a crucial mechanism to separate liquids or gas bubbles within a liquid by simulating a gravitational pull, effectively pushing denser components outwards from the center of rotation when a container is spun, allowing for separation where natural buoyancy wouldn't occur due to the lack of gravity; this is often used in space applications to manage fluids in microgravity environments.

The fluid inside the tank, cryogenic or otherwise, will eventually be "flung outwards" onto the walls of the tank, where it can be siphoned off. This will induce some degree of sloshing, like it or not. You need counter-rotation of a fluid-dampened weight to prevent gyroscopic precession and wobble. There will be bearings involved, for the damper assembly at a bare minimum. The tank / cylinder rotates in one direction, while the damper rotates in the other. The depot is gyroscopically stable and wobble or vibration is dampened using external counter-rotating weights. This is a good system capable of "self-correcting", and it's proven to work quite well when attached to internal combustion engines.

A massively de-rated internal combustion engine, or two, such as a Wankel, can supply the input mechanical power, requiring no delicate and expensive solar panels or radiators or batteries. This is IVF (Integrated Vehicle Fluids) technology that ULA developed for the ACES upper stage of Vulcan. The depot will only spin-up or spin-down while transferring fluids, thus the engine is only operated for an hour or two per transfer operation. It's low-tech, but it works, doesn't cost too much, and is durable, especially over the brief periods of time it will be operated for.

You need some oxidizer and fuel to power station keeping thrusters that correct attitude and adjust the orbit, as required, so even if you had an electrical stabilization and main propulsion system (such as the system proposed for ISS to reduce chemical propellant consumption), it would still require some higher-thrust chemical thrusters. Maybe you could do arc-jet thrusters, but then you have very high electrical power requirements.

When topped off, each of these LOX depots will probably weigh about the same as ISS, so around 1,000t per depot (Starship 3 carries a LOT of propellant). The chemical thruster system that uses the same oxidizer and fuel as what it's refueling is, in my opinion, the most highly integrated solution. A small combustion engine operating at low-load allows it to power itself for a long time. The mass associated with electrical propulsion is going to come close to the empty mass of the tankage (because you need quite a lot of power for near-impulsive maneuvers), so that's a bad cost and mass trade, in my opinion, even though it would economize on propellant consumption.

If you have other thoughts on this, please share them. My opinion is only a data point. It needs more math to show the trades. ULA did mass trades for LH2 boil-off with electrical vs the combustion engine, and concluded that for missions lasting beyond 24 hours, the combustion engine was the lowest mass solution, but that was 10+ years ago as of 2024, and it was an upper stage / space tug / propellant depot. If solar panel tech and battery tech has greatly improved since then, I think we should do a trade study.

You WILL get lower propellant consumption using SEP, but there's a substantial mass trade-off, and vehicle control is more difficult and delicate using SEP vs impulsive (higher thrust) chemical thrusters. So, run numbers on how much power for near-impulsive control over the depot, which informs PV panel mass, PPU mass, ion engine mass, etc. We have the tech now for both, so do the math for SEP Ion, SEP ArcJet (likely required for on-orbit maneuvering), and pure combustion (thrusters and internal combustion engine, the ULA "IVF" system) for mass and cost.

Spending more money on better hardware up-front, may or may not pay off, long-term, if that means greater maintenance down the road or operational restrictions (only transfer prop in full-Sun, battery charge state dependent prop transfer window, etc).

Summary:
1. Propellant slosh needs addressing
2. Gyroscopic stability is good for prop transfer safety (no "out-of-control" Agena docking target nightmares)
3. Do the trade studies on realistic options for vehicle propulsion and station keeping
4. Assume Argon or maybe even Oxygen vs very expensive Xenon for SEP, so lower performance but very low cost propellant
5. Keep tabs on anticipated costs and don't kid yourself about how expensive this "seemingly simple" propellant depot will be- it'll be the largest satellite anyone has ever put up there by quite a lot, and thus a very expensive capital asset, albeit one that enables all kinds of missions beyond Earth

tahanson43206 · 2024-11-10 21:28:16

For kbd512 re touchups needed as we close in on finishing the FluxBB upgrade.

This evening we discovered that there are style sheets in the production system that were not present in the clean system we downloaded from the repository.

That may not be a problem, if no one ever used one of the new style sheets.

A database query of the user table ??? may allow us to determine if there are any members who are using any of the alternatives styles.

If there are not, I think we could just leave things as they are. Otherwise, perhaps there is a way to import the additional style sheets from the production system?

(th)

tahanson43206 · 2024-11-17 21:35:07

For kbd512 re last hurdle with new FluxBB version!

It is possible that my Display setting in the new system got set to Air when I logged in without styles working.

I checked and the setting is indeed Fire in the production system.

Hopefully our members will check their ability to log in soon!

(th)

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#126 2024-10-21 17:48:46

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