You are not logged in.
I'm setting up the meeting now (th)
Offline
The meeting is open ... the audio alert is working ... we have 60 minutes to work with
(th)
Offline
This was a successful meeting from my perspective.
kbd512 has made excellent progress in his ongoing work with the FluxBB forum database. He has completed downloading of backups of all the files of data, and (as i understand his report) the various meta files that are needed to help to restore the data to a working database. Our goal for the coming week is to see if the Admins can download all those files from a repository, and install them in working order on our home systems.
That will be quite a feat if we can pull it off.
GW Johnson provided updates on his work on an enhanced version of the Rocket Hopper .... It is designed for Mars, so it does not look exactly like anything we've seen before designed for Earth.
For next week, GW has agreed to look at kbd512's idea of using Carbon Monoxide as the fuel for the Rocket Hopper, and kbd512 has begun uploading links to the GW Johnson Postings topic.
In addition, for next week, GW has agreed to attempt to create a Power Point movie as suggested by kdb512, after it turned out the little demo Google meeting system does not allow meetings to be recorded
And! Our contact from National Space Society will attempt to find out how to upload a video from GW to YouTube. We discussed using Zoom to make interactive discussion videos of GW's material, since Google meeting demo version does not appear to support that option.
***
Side note ... I noticed that Google is offering a free one month trial of their Premium version .... It might be interesting to try that.
(th)
Offline
We'll go with Google Meeting today .... 1 AM UTC, 7 PM Houston, 8 PM New Hampshire...
As a reminder, the link to connect to the waiting room is provided in the first post of this topic.
This topic will be open for communication during the meeting.
Google provides 60 minutes for a free meeting, and we can restart the meeting if necessary.
(th)
Offline
Follow up re Google meeting today...
Note: GW may not be able to attend due to ongoing family obligations relating to the Holiday season.
As a reminder, the link to connect to the waiting room is provided in the first post of this topic.
This topic will be open for communication during the meeting.
Google provides 60 minutes for a free meeting, and we can restart the meeting if necessary.
(th)
Offline
GW will attempt to make tonight's meeting. I've invited NSS chapter rep.
There are two little movies to show, and news about the Mars Hopper/Taxi study.
I've hit a snag attempting to load the saved backup data from the FluxBB data base. so hope that comes up.
Reminder ... We are using Google Meeting ... we are NOT using Zoom...
The connect link is at the top of this topic.
Time is 60 minutes ... I'll open the session close to the top of the hour.
7 PM Houston, 8 PM New Hampshire, 1 AM UK (UTC)
(th)
Offline
The equipment for tonight's meeting seems to be running smoothly ... I'll activate the waiting room a minute or so before 1 AM UTC.
This topic will remain open for anyone to write in if that would be helpful.
The link is in post #1 of this topic
(th)
Offline
From my perspective this was a very productive meeting. kbd512 coached GW Johnson through sharing the movie he made of the Rocket Hopper presentation, and our NSS contact was able to confirm receipt of the file.
Thanks to everyone who participated.
(th)
Offline
A part of my connection problem is that I thought we were going to be on the Zoom meeting, and I had that open. When I opened the Google meeting, it still didn't work "right" until I closed out of the Zoom meeting all the way. Even then, there were still problems, as we all saw.
After the meeting, I successfully uploaded to the Google drive, and then I may have successfully shared, the "truck train" video (4 minutes) with all 3 of you (Tom, Brian, and Keith). I also think I might have shared the original 4 min "rocket hopper" video with Tom, who got left off when I shared it with Brian and Keith.
Still working on the "rocket hopper/orbit taxi" presentation. I have a slide set, but no video yet. The first draft script read aloud, times-out as 9 minutes by simply watching the clock. That may be too long for Keith, I don't know.
Thanks to all 3 of you for your patience. I really know next-to-nothing of this computer and internet stuff. My saying that "the last phone I fully understood was rotary dial" is quite literally not a joke at all! I know that's hard to understand, but it really is true.
GW
Last edited by GW Johnson (2023-11-19 20:54:02)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
Offline
As a follow up ... members of NewMars are eligible to see the draft version of the movie(s) prepared by GW Johnson for the NSS education outreach via YouTube.
Assuming the file links arrived as reported in Post #34, I should be able to put them on Dropbox so everyone/anyone can see them.
However, there is no point in going to all that effort if there is no one interested in seeing them.
A request here (in this topic) would be sufficient to provide the motivation needed.
(th)
Offline
Just to make sure, I re-sent the 4 minute "truck train" and 4 minute (suborbital) "rocket hopper" presentations to Tom, Brian, and Keith. I also finished and uploaded a 6 minute "hopper / orbital taxi" presentation, and sent it to the same 3.
The same 3 presentations also exist in longer forms more suitable for a quarter-to-half-hour time slot, but no MP4's have been made of these longer forms.
The most astonishing thing about the "hopper/taxi" study was that the long-range suborbital mission set the need for heat protection, not the orbital mission! In fact, the vehicle could return as all exposed-metal construction from all shorter-range suborbital missions and the orbital mission! Keeping that result in, which is truly significant, is what made the "hopper/taxi" presentation run 6 minutes instead of 5.
Even the long range suborbital requirement for heat protection is rather minimal. Stagnation zone surface temperatures peak at just barely over 1800 F, everything else, including windward lateral surfaces, runs under 1600 F. That makes anything with good strength and corrosion resistance at 1600 F a candidate material. That includes SS316L and Inconel X-750. There are others.
The stagnation zone heat protection could be as simple as a thin sheet of 2000 F-capable metal over mineral wool insulation, mounted locally to the surface, and only in and near the stagnation zone. Pressures are low enough to make any low-density alumino-silicate ceramic composite feasible. Or even simple ceramic fabric blankets or quilts, if the wind shear doesn't rip them away.
GW
Last edited by GW Johnson (2023-11-20 14:04:48)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
Offline
Hot CO2 gas is corrosive to steels. The UKs gas cooled reactors experienced corrosion that was only partially mitigated by methane injection. For Magnox reactors which operated at temperatures ~400°C it was a tolerable problem. But AGRs operated at 600°C and suffered severe boiler corrosion. Stainless steel has lower corrosion rates but is not immune, because CO2 reacts with chromium to form chromium carbide, which then oxides and scales off.
https://iopscience.iop.org/article/10.1149/2.F08212IF
However, these are problems in metals that are exposed to hot CO2 continuously for many years. The rocket is exposed for a period of minutes out of every flight. It isn't clear if this would neccesitate use of a different metal or if the corrosion rate is tolerable in light of other life limiting factors for the rocket. There is little point specifying exotic metal heat shields if the fatigue life of the airframe is up before this becomes a problem. One additional complication with the Martian atmosphere is the presence of free oxygen ions in the ionosphere due to photolysis.
On top of the corrosion life concerns is the fact that 316SS melts at about 1400°C. Long before it melts, it progressively loses strength the closer it gets to melting point. At high temperatures, alloy steels become vulnerable to grain boundary precipitation that will aggrevate any corrosion problems and may lead to stress corrosion cracking. There is no easy way of quantifying these problems without experimentation because there are too many unique variables. Oxide dispersion alloys have higher service temperatures, because the oxide particles lodge in crystal dislocations and grain boundaries reducing slippage even at higher temperatures. This doesn't increase melting point, but it does reduce the rate of decline of strength with increasing temperature. These steels are expensive and difficult to fabricate.
One could simply accept the fact that a heat shield has limited life and design a shield that can be unbolted from the airframe after x number of uses. That way, you can live with the technical uncertainty and use experimentation to refine the heat shield design in service to zero in on a cost optimum solution. In much the same way, aircraft engineers were able to refine the material science of gas turbine engines, making periodic improvements over many decades. Modularising the vehicle subsystems makes this easier to do.
Alumino-silicate materials would be less vulnerable to corrosion, given that they are oxides already. Aluminium oxides are not vulnerable to chemical reduction in reducing gases. If they were, we would be making aluminium in that way instead of molten electrolysis. The problem with ceramics in this situation is that we have high a material that is both brittle and a relatively poor conductor of heat. This leads to thermal gradients, with different rates of thermal expansion between layers. This would lead to cracking in any solid ceramic tile. Cermets are possible, as are fibre reinforced cements. But a ceramic heat shield is going to be relatively maintenance intensive and requires inspection between flights. You aren't going to have the same problem with stainless steel. Once you have quantified problems like corrosion and grain boundary precipitation, the safe working life of shield is a known variable.
Last edited by Calliban (2023-11-20 15:16:50)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
Offline
The topic title is updated to reflect it's availability for post-meeting discussion.
The opening post was updated to reflect the new mission:
Updated 2023/11/21 Expanded role for topic...
GW Johnson and Calliban have added posts to this topic following the meeting of November 19, 2023. These posts illustrate the potential for this topic to contain followup discussion of topics that came up in the meeting. As a courtesy, I'd appreciate members referring explicitly to the post and the topic within the post to which they are adding a comment. Any post in the Google Meet topic should have ** some ** connection to the most recent meeting.
(th)
Offline
The Thanksgiving Holiday in the States has brought many families together for the four day Weekend.
I'll set up the Google Meeting at 1 AM UTC as usual, but will be surprised if any of our members decide to stop by.
Time is 7 PM Houston, and 8 PM New Hampshire. This is a Google Meeting, so please use the link at the top of Post #1.
Due to the 1 hour time limit, I'll open the waiting room just before the top of the hours.
Possible items of interest might include the status of the MySQL database loading operation, which appears to have completed successfully here.
We will have no news of the Videos that GW Johnson prepared due to the Thanksgiving Holiday impact on the North Houston NSS chapter.
(th)
Offline
The waiting room is set up for tonight's Google Meeting .... I ** think ** the meeting clock starts when the first guest arrives.
The system seems to be working normally.
Most important (to me for sure) is that the audio alert is working, so when a guest arrives I'll be notified.
(th)
Offline
The meeting is started ... kbd512 and I are here
The meeting just ended! From my point of view, this was a ** very ** productive session.
kbd512 coached me through configuring my user id to work with the fluxbb_newmars database. We consulted online documentation until we found the command that works, and now the non-root user is able to open the database and see the tables.
This is a prerequisite for connecting the database to php, which * I think * is the next step.
***
For SpaceNut ... this is a good time for you to try to set up MySQL on your home system. The procedure to make things work is fresh in mind. It would be good to have duplicate working systems running at all three households.
(th)
Offline
It is Sunday, and we have an opportunity to set up a Google Meeting today.
I'm planning to open the waiting room at 1 AM UTC, 7 PM Houston, 8 PM New Hampshire.
Last week was devoted entirely to validation of the MySQL database created on a development system here.
The previous week was devoted entirely to helping GW Johnson in moving toward a goal of putting his presentations up on YouTube courtesy of the NSS chapter in Houston (North Houston) (there are two chapters).
This week is open for anyone to offer a theme. Todo items include adding php to the development system, along with Apache or Abyss to provide browser support, and securing a copy of the upgraded FluxBB package, with changes made by kbd512 to allow it to run under current php software.
(th)
Offline
I've been looking at the freight transport issue from the moon to LEO, using stations in an elongated halo orbit about the moon as a staging point. Nothing to report just yet. I do this as time permits. Things have gotten busy as the holidays arrive.
The craft that travels between the surface and the station is not the craft that travels between the station and LEO. That much I know already. The lander has a higher thrust requirement. Propellant ullage will be a very serious issue for both vehicles.
NASA's version of the halo orbit extends beyond the Hill sphere stability limit as well as being high enough at periapsis to increase the dV requirements on the lander. I think they may have been driven into that corner by their underperforming Block 1 SLS/Orion not-quite-a-moon-rocket moon rocket than literally cannot reprise Apollo 8, much less any of the landing missions.
I've been looking at that halo orbit and another one that stays inside the Hill sphere, with a lower periapsis. Either one has one distinct advantage over low circular like Apollo: the apoapsis velocity is so low that even a 90 degree plane change is a small dV. You can literally land anywhere on the moon, quite unlike Apollo.
GW
Last edited by GW Johnson (2023-12-03 10:44:07)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
Offline
For GW Johnson ... we could probably make a meeting with just the material in Post #43.
I will try to have something to show, but I'm not sure what it will be yet.
(th)
Offline
The meeting room is open.
This is Google Meeting, not Zoom
Reminder: the link is in Post #1 of this topic
Post meeting report .... kbd512 and I worked on configuration of Apache2 to access/accept php ...
I ended up with some homework to do to prepare for next week's meeting .... there have been some changes made to apache2 that make it slightly different from previous versions.
***
We took a few minutes to talk about the NASA ideas for the Gateway, and what factors led to the decisions made about where to position the Gateway, and which vehicles to use to do what.
(th)
Offline
Today is Google Meeting day at NewMars....
Agenda items include:
1) Status of duplicate environment in Admin offsite systems
2) GW Johnson new work on Lunar vehicles and specific orbits - possible movie - slide show for sure
3) Status of Large Ship 3D modeling
4) Other items? SpaceX staging?
The link to the meeting is available in Post #1 of this topic.
Times: 7 PM Houston, 8 PM New Hampshire, 1 AM next day UTC
(th)
Offline
I will try to make the google meeting.
Won't have any video. Will have slides. The paper is up and visible in the drop box with the forums link, and it is also up on my "exrocketman" site. The "exrocketman" posting seems to be drawing quite a bit of readership.
In case I cannot, here's the results:
Those design rough-out results indicate that propellant manufactured at the moon's south pole should be shipped directly to LEO by a single vehicle, and not trans-shipped in two vehicles via some station in a halo orbit about the moon.
It is possible to do this single stage and unrefilled, despite the substantial dV, if one makes the return voyage very lightly laden (5 tons of tank empties plus single-digit cargo tonnage, sized for 95 tons of payload-propellant outbound).
I could not make LOX-LCH4 work for this design, the dV is past the knee in the curve, where adding vast quantities of propellant to the sizing gets very little improvement in dV. It was marginally feasible with LOX-LH2 while not pushing the state-of-the-art very hard. That's OK, LOX-LH2 is exactly what you can make from ice, without any easily-used carbon.
The ratio of tons-burned to tons-delivered was lowest with this direct shipment. With LOX-LCH4 propulsion, the halo station route was actually less favorable than shipping propellant up from Earth using SpaceX's Starship/Superheavy. With LOX-LH2 propulsion for the halo station vehicles, I think that ranking might reverse, although I did not size such vehicles.
However, the halo route cannot beat the direct route, because of the compounding effect of payload fractions in two vehicles, versus the simple payload fraction of only one. NASA will not like me finding their halo station to be useless for supplying lunar-derived propellant tonnage to LEO. For such a purpose, "Gateway" will be no gateway at all.
And, I found "Gateway" to be in the wrong orbit anyway, one that is not long-term stable. Its apoapsis is outside the moon's Hill sphere for long-term stability.
GW
Last edited by GW Johnson (2023-12-10 10:19:37)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
Offline
The Google Meeting is on track to start at the top of the hour. Use the link in Post #1 of this topic.
GW Johnson is here and we're in business.
Well, GW ** was ** here ... he clicked on something and went away. He's back
Post meeting summary:
GW Johnson gave his presentation on his recent work on a variety of scenarios relating to the Moon.
He received feedback (questions and comments) from kbd512 and me, and his next venture will be to turn this into a movie, using the PowerPoint movie software suggested by kbd512 a couple of weeks ago.
I demonstrated a working php command that shows the entire configuration of software needed to run the forum software is installed and working, and the database is loaded. Most of the data tables appear to have loaded correctly, but there are problems with the post table. The problems seem to involve the messages, and I suspect that the problems may turn out to be related to the use of special characters. I'll be investigating that problem further.
kbd512 has agreed to upload the version of the forum software that he has modified to run with state-of-the-art support software.
(th)
Offline
Today is Google Meeting day for NewMars...
I'm planning to open the waiting room at 1 AM UTC, 7 PM Houston, 8 PM New Hampshire...
Last week's meeting was interesting and productive.
Agenda for today's meeting may include updates on GW Johnson's work on presentations including video ones.
In addition, I have completed validation of the data for the duplicate forum configuration here. All that remains is to install forum software.
Other subjects are possible, and welcome.
The link to the meeting is available in Post #1 of this topic.
The meeting will last for an hour but it can be renewed if there is interest.
(th)
Offline
The Google Meeting is on track to start at the top of the hour...
Update at 19:57 New Hampshire time ... the waiting room is open.
(th)
Offline