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GW,
Well, it's working now.
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tahanson43206,
I think that the answer is for all of us to join the meeting in progress.
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For GW Johnson .... please keep going with kbd512.
My attempts to connect are causing the difficulty.
(th)
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tahanson43206,
You can connect using the link I provided, but it just needs to be to the same meeting.
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tahanson43206,
Are we giving up for tonight?
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Many Thanks to kbd512 for opening the meeting for GW Johnson, and later for me.
The procedure for starting a meeting seems to be solid if kbd512 is the lead host.
I'm (obviously) still having to learn the ropes.
We'll leave it that folks who would like to schedule a Zoom session need to post a request in the Zoom topic at least a day ahead of time.
(th)
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For all ... We are still in a learning phase in use of our Professional Zoom account.
Yesterday, I learned that a co-host (kbd512 and I are co-hosts) can create a brand new set of meeting numbers out of thin air.
This is NOT what we want. The numbers for the NightOwl meeting are published in post #1 of this topic.
For everyone to know ahead of time what set of numbers to use, each set of numbers can be given a name (I think) and published in Post #1 of this topic.
Yesterday, I tried to use the NightOwl numbers, and caused a new session created by kbd512 to crash. This is the same problem we ran into with our test Zoom, when Executive Director James Burk started up his Seattle meetings.
We need to agree upon a set of numbers we will use from one week to the next, to avoid creating new sets of numbers.
There may well be a need for separate named sets of numbers, but I am concerned that by creating new sets of numbers, we may be accidently exhausting some resource.
From now on, until we have a better handle on what we are doing, let's try to use the NightOwl numbers.
(th)
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I've tried all the links I can find in this thread, and get the same message: to wait until the host starts the meeting.
Does not seem to be working tonight.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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GW,
I'm working on it.
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I get "the host has another meeting" as of 7:10
As of 7:12, the latest posted link no longer works at all.
GW
Last edited by GW Johnson (2022-08-07 18:12:39)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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GW,
That's odd. I guess Tom has another meeting up and running.
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GW,
Try it again, let me know if you get the same thing.
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For all .... I was tied up all day working on the Post Repair and forgot all about it being Sunday and Zoom day.
I've been trying to figure out how to put Zoom back on track.
We discovered that a host can create a new set of numbers.
This is not good!
We ** have ** a set of published numbers, and should NEVER use newly created numbers.
the procedure that seems to work is to join the numbers published in Post #1 of the Zoom topic.
If you are a host, then log in using the host email address and password.
We want our members to ALWAYS use the same numbers, week after week.
I apologize for becoming so tied up today that I forgot everything else.
(th)
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post 410 actually has extra characters in the link address
%22
this proceeds the https....
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For all,
I have just confirmed that Post #1 of this topic contains the set of numbers needed for a meeting using the Mars Society Professional Zoom account.
I'm asking everyone to use that set of numbers.
If you have an interest in taking part in a Zoom session Sunday evening, please post a message here, or let either kbd512 or me know by emaill
We had regular weekly meetings for several months, and then we entered a period without a regular meeting.
Please let the co-hosts know if you would like to attend a meeting tomorrow evening.
I am able to connect at 1 AM UTC, but it is possible kbd512 would be willing to set up earlier.
Thanks to everyone for past support of the Zoom offering.
(th)
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Sunday is Zoom Day for NewMars Forum.
We are in a By Request mode right now....
If someone would like to request a Zoom session, it is easy enough to do ... just post a request in this topic.
(th)
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Zoom call is now in session.
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Refer to the very first post in this thread to join the meeting, so go back to the very first page and very first post to find that info.
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Today's meeting includes RobertDyck, Host kbd512 and late arrival tahanson43206
Discussion covered a range of topics as usual, with focus on solid material used for hybrid rockets.
Here is a copy of the chat as of this point in the meeting:
From Me to Everyone 10:18 PM
https://news.satnews.com/2022/08/01/hyi … aerospace/
From Rob Dyck to Everyone 10:26 PM
https://www.tasteofhome.com/article/how … ast-longer
From Me to Everyone 10:32 PM
https://www.youtube.com/watch?v=e8w5CZDXNfg
From Me to Everyone 10:40 PM
https://www.priyamstudycentre.com/2018/ … ation.html
From Rob Dyck to Everyone 10:43 PM
http://canada.marssociety.org/winnipeg/plastics.html
From Me to Everyone 10:49 PM
Paraffin wax | What is solid paraffin| Arash Mahya - آرش مهیاhttps://arashmahya.com › paraffin-wax
I'd like to call attention to the web site where RobertDyck is the webmaster .... the page in the url is a collection of chemical information.
(th)
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Today is Zoom Day for NewMars forum.
Last week's experiment using the meeting numbers in Post #1 of the Zoom topic seemed to go well.
No meeting is scheduled at the moment, but we have two co-hosts who might be able to schedule a Zoom meeting at a time you might prefer.
If you are interested in participating, please post a note here in the Zoom topic.
(th)
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The meeting has started. We're still using the meeting info from the very first post in this topic.
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it is now 1 AM UTC and the Zoom is continuing
If there is anyone interested in joining, please either log in or post a note here
(th)
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Many thanks to kbd512 for hosting this evening's Zoom
We took a look at Void's question about using waste heat from a nuclear reactor in a space vehicle to produce thrust.
The comparison is between dumping waste heat to space using radiators, and investing waste heat in accelerating a fluid such as hydrogen.
There are many tradeoffs (I'm sure) but here I'll only mention two that I know of....
Per kbd512's reminder, the lower the temperature of the exhaust to be disposed of, the larger the size (and therefore mass) of the radiator.
On the other hand, the lower the temperature of the exhaust, the lower the thrust that might be achieved.
The tradeoff for using radiators is the mass of the radiators, which remains constant throughout the voyage.
The tradeoff for using a fluid is that the mass is high at the beginning of the voyage, so the effect of the thrust is smaller than is true as the flight continues, until at the end of the voyage, the fluid is exhausted and the thrust is at it's maximum.
There may be too many unknowns to be able to compute useful results, or to make useful design decisions.
At this point, in the absence of numbers to work with, we are left with impressions of what might happen.
(th)
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tahanson43206,
The nuclear reactor doesn't care if your Hydrogen propellant is present to absorb the reactor's excess thermal power output, or not. The reactor does care about what temperature it's operated at. If it gets hotter than the containment vessel or nuclear fuel or whatever else it's made from can withstand, then it melts down and ceases to produce usable power output in any form. If your constant electric power output requirement is 1MWe from the electric generating portion of your overall space nuclear power system, then that determines the size of your radiator array. If you demand more power from the reactor, then you have more waste heat to get rid of, period. That's why overall thermal-to-whatever efficiency is such a big deal. Within limits, you can run reactors at higher temperatures in order to reduce the size of your radiator array, but that typically demands heavier materials (high grade steels, Tungsten, or ceramic metals) that increase the weight and decrease the overall performance. Since we discussed VASIMR in this use case, "overall performance" is what Dr. Franklin Chang-Diaz calls the "Alpha" of the vehicle. That's power-to-weight ratio in layman's terms. Dr. Chang-Diaz required an alpha of 1kWe per kg of total space nuclear power system mass, from a theoretical space nuclear power system, in order for VASIMR to propel a nuclear-electric / VASIMR-powered vehicle to Mars in 39 days. Dr. Zubrin lambasted the idea, but then NASA did some experimentation indicating that such a system might be possible using a TWDEC (Traveling Wave Direct Energy Conversion) nuclear power system.
The folks at University of Washington State also called their proposed pulsed plasmoid nuclear fusion propulsion system's overall power-to-weight performance, the "Alpha" of the vehicle. Those were some of the same bubbas who came up with M2P2 for radiation shielding and propulsion and aerobraking, Dr Slough / Dr Kirtley / Dr Wing Lee.
NASA then funded another fusion propulsion concept with more performance potential, from Georgia Tech I think, after extensive computer and lab experiment work was carried out on the exponentially increasing magnetic field confinement concept from U of W, which is not at all new in the world of fusion physics experiments. Basically, U of W's fusion propulsion concept was based on implosion of a D-T pellet trapped inside the magnetic field of an Aluminum or Lithium foil liner that was electromagnetically collapsed around the D-T fuel at supersonic speeds and the heat of fusion used to vaporize the metal foil liner to generate thrust and lots of it. This was repeated multiple times per second. It probably would've worked, because it's been working in various fusion experiments here on Earth for many years, but GT's concept has a lot more potential over time and could enable moving ISS-sized spacecraft to Mars while expending almost nothing in terms of propellant.
Anyway, the U of W concept would've produced 36MW of jet power from Lithium foil vaporized at the moment of fusion, also had an alpha of 1kW/kg, while being directed out an electromagnetic nozzle / pusher plate assembly (think drastically scaled-down Orion-esque nuclear bomb propulsion system). IIRC, it required 180kWe of input solar power provided by a pair of ROSA arrays, some of the power of each "shot" was recycled back into the super capacitor bank, and it would've been the first practical propulsion design capable of delivering 50% payload on a "normal" 6 month outbound flight to Mars, and come back, and capture into orbit at both ends of the trip, all without refueling. The "trick" is that U of W's fusion propulsion concept didn't generate 1 Watt of electrical power from fusion, so it didn't run afoul the most intractable problems of fusion energy. All of the heat and power from fusion was immediately directed out the rocket nozzle, which also had the effect of drastically lowering the radiator mass required. They made it as far as demonstrating that the foil liner could be formed and collapsed at the required supersonic speed and repetition rate to generate every bit of the 36MW of power promised. The concept is actually quite like how fission is achieved in nuclear weapons using explosively-driven supersonic implosion, except that the super caps generate the input power and the foil liner imploding at supersonic speeds generates an exponentially increasing electromagnetic field which achieves the temperatures and pressures required to fuse the D-T pellet. As I said, it's been done many times in university plasma physics experiments, but this was / is a very novel application of the technology that uses it for propulsion rather than electrical power output. I thought of this because you asked how to avoid the need for huge radiators and this is how the U of W team generated big power numbers without big radiators.
In practice, you could run a nuclear thermal propulsion system at very high power for propulsion purposes, and then operate it at very low output levels to generate electrical power thereafter. However, your radiator array sizing must be sufficient to operate your reactor at whatever power output level you need to generate electricity. This was part of the Bi-modal and Tri-modal NTR design concept proposed decades ago. The reactor would go to GigaWatts of output for a half hour for propulsion, then drop down to a few 10s of kWs of electrical output for the rest of the transit.
If you had a nuclear reactor ejecting fission fragments from a very thin rotating "hard drive platter" design, then you could conceivably get crazy-high Isp numbers, thrust in line with any other high-power electric propulsion system, and do that without massive radiators. The "dusty plasma" variant would use Am242m nuclear fuel and could conceivably achieve a specific impulse as high as 1,000,000 seconds (not a typo). A transit to Mars would take as little as 14 days. Am242m was chosen because it only requires 1% of the mass of U235 or Pu239 to go critical. This concept came out in the 1980s. I think the fact that it was basically an open cycle nuclear reactor core intentionally throwing fission fragments out the back is what killed it, sort of like the open cycle gas core and nuclear salt water rocket or detonating nuclear weapons behind the spacecraft.
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