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For Calliban re hoop stress of habitat around an asteroid...
https://newmars.com/forums/viewtopic.ph … 76#p232976
In your reply to Void's image of a toroid shaped habitat around an asteroid you mentioned hoop stress.
This is something I had not thought about before, so thank you for adding this to the architectural issues to be addressed.
A maglev track would certainly help to facilitate movement within a toroidal habitat, so it seems to me a useful addition to the mix.
An O'Neill colony of 1 mile diameter would certainly have hoop stress, but until you brought it to our attention, it would have been easy to overlook.
It would be great to have a detailed study of the forces at work as humans contemplate large rotating habitats.
There aren't many who could make a meaningful contribution to a discussion about the architecture of a rotating space habitat, but you might be one of them.
The Admins could create an environment for such a study, if that would be of interest to members.
Update: If a rotating asteroid is the site for a habitat, does it have to be a full torus? GW Johnson has described baton style habitats for space travel. This idea was studied decades ago by NASA as well. What I'm thinking about is structures on opposite side of a rotating asteroid to maintain rotational balance. A natural shape might be a dome. I suspect there is a limit to the rotation that an asteroid can tolerate before it disassembles.
In fact (come to think of it, that natural limit would be the gravity of the asteroid itself)
Your recent suggestion of excavating a volume inside an asteroid for a large rotating habitat comes to mind as an alternative that might have the best result for the expenditure of energy needed.
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I should clarify. I am not talking about using a maglev for internal transportation, though that may also be of interest in a ring habitat. What I was suggesting was balancing the centrifugal outwardforce of the ring habitat against the gravitational weight of the rock or ice above the tunnel. For point of example, suppose we find an icy kuiper belt object with a surface gravity 1% of Earth. At a depth of 12km beneath the surface, the ice above a tunnel would have a weight of 100 tonnes per square metre, pushing down upon the ceiling. If we put a maglev track on the ceiling of a circumferential tunnel, we can use that weight as a counterbalance for the centrifugal force of the rotating ring habitat.
"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."
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For Calliban re #277
First, thanks for clarifying... I actually understood what you were describing, but I couldn't (apparently) fit it into a frame that I understood, so I translated it into a transportation system.
Would you be interested in seeing a forum structure dedicated to habitats?
if so, I can bring it up with the Admins to see if they would like to introduce another Forum into the Infrastructure category. We have no architects in the membership at present, but we might be successful in recruiting one or two. I realize you are not an architect, but your interests and background would allow you to become one in the context of this non-academic forum.
What I think would be of interest would be a study of your concept for a revolving train of habitat carriages inside a tunnel inside an asteroid of sufficient size. It would be interesting to see how such a train might support human life under those circumstances.
It might be possible to run trains beside the habitat train, to permit entry and exit.
This is a habitat concept that I ** think ** is totally new. As often happens, this is a spinoff from one of Void's visions.
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For Calliban re post on rail guns...
https://newmars.com/forums/viewtopic.ph … 82#p232982
By coincidence, kbd512 talked about exactly that .... self steering munitions from ordinary gunpowder cannon, in the most recent Google Meeting.
If I recall correctly, kbd512 said the munitions use fins to steer, and they do NOT include propulsion of their own.
An inexpensive combat drone wouldn't have a lot of stealthy features, although I suppose clever combatants might think of some.
Update:
I ran a quick Google and got this:
Self-steering bullet researched by US weapons experts
BBC
https://www.bbc.com › news › technology-16810107
Mar 8, 2012 — A self-guiding bullet that can steer itself towards its target is being developed for use by the US military.Discussions and forums
Self Steering Bullet Developed By Lockheed Martin
GTPlanet ·
13 years ago
·
I found this really cool and quite worrying in equal measures :scared: Self-steering bullet researched by US weapons experts A self-guiding.
50 caliber is impressive! Under wing self-guided missiles is one thing. A 50 caliber bullet is something else entirely.
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For Calliban re rock tumbling ....
SpaceNut's benediction inspired me to ask Google for information about rock tumbling. The first YouTube that came up showed how to use grit to facilitate the grinding. Apparently it is possible to run tumbling without grit.
If you have a moment to spare, please say a bit more about how the machine will work. Where are you sourcing your rocks?
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For Calliban re many contributions by Void over many years...
Thank you for your perspective as given in a post in Void's Postings topic July 24th.
While we (as a group) attempt to sort through this, please think of notable contributions Void has made that have caught your attention, or that your would particularly like us to remember.
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For Calliban re membership in the forum....
You are literally the ONLY person who has written a post that is about membership.
The outreach effort that SpaceNut put into place drew in five (or possibly six) new members, and most have not participated beyond an initial post or two.
Notable exceptions are PhotonBytes most recently, and Steve Stewart.
Steve in particular contributed an entire concept for agriculture integrated with habitats for Mars.
PhotonBytes still drops by occasionally, but we haven't heard from Steve since 2023.
It seems to me our existing members may feel as though this is a small club whose members share a great deal in common.
The site itself was created to be open to the entire world, and in early years, that actually happened. We have real people (as compared to spam) from many continents, deep in the archives.
The site itself was created to be available to people of all ages and certainly women as well as men. Palomar is a terrific example of a woman who contributed 9800+ posts.
It is possible (and indeed likely) that not all members are aware of GW Johnson's attempts to provide educational opportunities to young people as well as older persons to learn about ellipses in the context of Orbital Mechanics, and more recently he is working on a suite of software and procedures to enable a person to design a rocket system that would stand up to review by professionals.
The kinds of persons we might hope would become members are NOT (yet) cynical adults. They'll get there, I have no doubt.
The topic that Void created was created in all innocence, of purely scientific curiosity.
The problem that occurred is that Void inadvertently used language that would be a magnet for search engines looking for activity on the Internet that is NOT what Void had in mind.
The language would also have set off alarm bells in the minds of mothers (and some fathers) whose children might be interested in this site.
It seems to me that you and Void have identified a need for a private discussion group that is not viewable by the public.
The Mars Society is probably not a good place for such a group.
I remain committed to trying to implement SpaceNut's initiative to bring in new members.
We (Admins and Mods) depend upon our members to provide a welcoming and encouraging environment for young people (or persons of any age for that matter) to try out ideas for their own careers in space or in support of those who go to space.
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For Calliban re exclusive private forum ...
Prior to the current discussion, I have not learned about private forums.
The need that your recent post suggests to me is for a private place where consenting adults can discuss matters that are not suitable for all ages. I asked Google's Gemini, and learned that there are a great many such places.
In addition, I learned that visibility to the public can be turned off with a simple switch at the Admin level.
As it happens, we (admins of this forum) have a test account on Azure, and we have two test sites set up that are visible to the public.
It would be possible (and apparently easy) to configure one of the test sites so that private conversations such as the one Void proposed could be carried on without anyone outside the membership being aware of it.
I suppose the security forces of every nation on Earth would want an account, but that's a question for another day.
In the mean time, if members of ** this ** forum want a place to discuss matters not suitable for ** this ** forum, we have the capability of setting one up.
Here is the conversation with Gemini:
Conversation with Gemini
Private Internet Forum - Hi Gemini! Thank you for your assistance with many previous requests. Today I have a request that is a bit out of the ordinary. I am a participant in an Internet forum that is free and open to the public. Recently, two members expressed interest in having a conversation that is of a sensitive nature, suitable only for adults. Our forum cannot support conversations of that type. however, it occurred to me that there may be such a thing as a private Internet forum, which is not visible to the public, which which is fully visible to members. Have you ever heard of such a thing?
***Yes, absolutely! What you're describing is very common and exists in many forms. A "private Internet forum" or "members-only forum" is a standard feature of many online communities.
Here's how they generally work and some key characteristics:
Restricted Access: Unlike public forums, private forums require some form of authentication (like a username and password) to view or participate in content. This keeps conversations hidden from the general public.
Membership Control: The forum administrators or moderators control who gets access. This can be:
Invitation-only: Members are invited by existing members or administrators.
Application-based: Prospective members apply and are approved or denied.
Paid membership: Access is granted upon payment of a fee. <<== optional, obviously
Requirement-based: Members might need to meet certain criteria (e.g., a certain number of posts on a public forum before gaining access to a private section).
Privacy and Confidentiality: The primary purpose is to provide a safe space for discussions that might be sensitive, confidential, or simply not intended for public consumption. Members often agree to rules of confidentiality regarding the content discussed within the private forum.
Examples of Use Cases:
Sensitive Topics: As in your case, for adult-oriented conversations, support groups for specific conditions, or discussions about private personal matters.
Professional Groups: For members of an industry to discuss proprietary information or internal challenges.
Gaming Guilds/Clans: To coordinate strategies and share information among members.
Family/Friend Groups: For private communication among a select group. << This may be of interest to some NewMars members
Beta Testing/Development: For discussing unreleased products or software among a select group of testers.
How your forum members could achieve this:
Given that your existing forum doesn't support it, the two members interested in a sensitive conversation would need to either:
Find an existing private forum: There might be other online communities that already cater to the specific sensitive topic they want to discuss and have private sections.
Create their own private space: This could be as simple as:
A private group on a social media platform: Many platforms (Facebook, Reddit, etc.) allow the creation of private groups that are not visible to the public.
A dedicated messaging app group: WhatsApp, Signal, Telegram, Discord, etc., allow for private group chats.
A hosted private forum solution: There are many forum software options (like phpBB, Simple Machines Forum, vBulletin, XenForo) that can be installed on a web server and configured to be completely private. Some companies also offer hosted private forum services.
So, yes, a private Internet forum is definitely "a thing," and it's a very effective way to facilitate discussions that require discretion and privacy.
***Thank you for this helpful list. Our forum is running on a typical PHP based package, and it is visible to the public. Is there a way to turn off visibility to the public for such a forum?
***Yes, for most typical PHP-based forum packages (like phpBB, Simple Machines Forum (SMF), MyBB, vBulletin, etc.), there are definitely ways to turn off public visibility and make them private. This is usually done through the permissions system in the forum's Administration Control Panel (ACP).
The general principle is to restrict the "Guest" user group's ability to view any content. <<== Set at Admin level
Here's a breakdown of the common steps and concepts:
1. Understand User Groups and Permissions
Guests (or Anonymous Users): This is the crucial group. Anyone who visits your forum without logging in is considered a "Guest." To make your forum private, you need to strip this group of all viewing permissions.
Registered Users: This group consists of users who have successfully created an account and logged in. They are the ones you want to grant access to.
Other Groups (Moderators, Administrators, Custom Groups): These groups have elevated permissions, but the focus for privacy is on Guests and Registered Users.
2. Access Your Forum's Administration Control Panel (ACP)
You'll typically log in with your administrator account and find a link or button for the "Admin Control Panel," "Administration Panel," "ACP," or similar.
3. Modify Guest Group Permissions
This is the primary method to make the entire forum private.
Find "Permissions" or "User Groups" section: Navigate to the section of your ACP that deals with user permissions or group management.
Select the "Guests" (or "Anonymous Users") group: Find this group in the list of user groups.
Edit forum-specific permissions for "Guests":
"Can view forums" / "Can read forum" / "Can access forum": Set this to "No" or "Never" for all forums. This is the most critical step. If this is set to "No" for all forums, guests won't be able to see any topics or posts.
You might also want to set other permissions for Guests to "No," such as:
Can post topics
Can reply to topics
Can search
Can send private messages (though they likely won't be able to without an account anyway)
4. Modify "Bots" Group Permissions (Recommended for SEO) <<== Important ... something I would have overlooked
Most modern forum software also has a "Bots" group (for search engine crawlers like Googlebot). To prevent your private content from being indexed by search engines, you should apply the same "No Access" permissions to the "Bots" group as you do for "Guests."
5. Adjust Global Board Settings (Optional, but useful)
Disable Guest Registration (Optional): If you want to strictly control who can join, you might go to "User Registration Settings" or "Board Features" and:
Set "Account Activation" to "By Administrator" or "By User" (meaning they need to click an email link).
Consider disabling open registration entirely if you plan to invite specific members manually.
Set a Custom Message for Guests: Some forums allow you to set a custom message that guests see instead of an empty forum. This can be helpful to explain that the forum is private and how to gain access (e.g., "This is a private forum. Please register or contact an administrator for access.").
Hide "Who is Online" / Statistics for Guests: Some templates might still show "Who is online" or general statistics to guests even if they can't see forums. You might need to adjust template files (more advanced) or look for specific settings to hide these elements from non-logged-in users.
Important Considerations:
Registration Process: If you make the forum fully private, potential new members will only see a login screen or a "No Forums" message. You'll need a clear way for them to register or request access.
Keep Registration Open, but Require Admin Approval: This is a common method. Guests can register, but their account isn't active until an administrator manually approves it.
Invitation System: Some forums have built-in invitation systems.
Existing Content: Once you change permissions, existing public content will become private. Only logged-in users with the correct permissions will be able to see it.
Search Engine Indexing: While setting bot permissions helps, it doesn't guarantee removal from search engines immediately if the forum was public for a long time. You might need to use Google Search Console (or similar for other search engines) to request removal of indexed pages. Adding a robots.txt file with Disallow: / can also help tell bots not to crawl the site, but it's not a security measure.
Backup: Always back up your forum files and database before making significant changes to permissions or configurations.
By carefully configuring the permissions for the "Guests" and "Bots" groups, you can effectively transform a public PHP forum into a private, members-only community.
Sources
***
Thank you! This is ** very ** helpful!
***
You're very welcome! I'm glad I could provide such useful information.If you have any more questions as you go through the process of making your forum private, or if you encounter any specific hurdles with your particular forum software, don't hesitate to ask.
So there you have it... There are options available for NewMars members who might wish to discuss subjects not suitable for the NewMars forum. The NewMars forum is viewable by the entire population of Earth, and it is open to persons of every age and nationality.
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For Calliban re privacy for forum member posts ...
I am interested in the question you and Void have brought to our attention. In the conversation below, I asked Gemini if it is possible to hide a post from the public, in a public forum. Apparently the answer is yes, but there are so many complications I think I it is highly unlikely the existing four Admins could find the time and energy to pull it off, assuming Mars Society is willing to approve the project.
Never-the-less, here is how that might be done:
Hi Gemini! After posting your reply, it occurred to me there might be another option. Our forum is open to all ages and it is open to the public. One of our members wanted to discuss a sensitive subject not suitable for our audience, and another member expressed interest in seeing it. For the moment, the first member has kindly agreed to remove the post. However, it just occurred to me that perhaps an individual post might be rendered visible only to registered members. In following up on your comprehensive answer above, do you think it might be possible to make an individual post visible to members only?
***
That's an excellent follow-up question, and it gets to a more granular level of control!While making an entire forum visible only to registered members is straightforward in most PHP forum packages, making individual posts (or even individual topics) visible only to registered members is generally not a built-in feature for public forums.
Here's why, and what your options are:
Why it's generally not a built-in feature for individual posts:
Complexity of Permissions: Forum software is primarily designed to apply permissions at the forum or category level. Applying them at the individual post level (or even topic level) introduces a lot of complexity:
How would the forum display a topic where some posts are visible and some are hidden?
What happens to pagination if hidden posts are skipped?
How do replies interact with hidden posts?
It creates a potentially confusing user experience for guests who see a partial conversation.
Performance: Checking permissions for every single post in a thread for every single user request would add significant overhead, especially for busy forums with long threads.
Search Engine Indexing: If a public topic contains a hidden post, search engines might still index the visible parts, but the hidden part would be missed. This might not be a concern for sensitive content, but it's a factor in general forum design.
Purpose of "Public": A "public" forum implies that the content is generally accessible to anyone Browse. Introducing selective post visibility can muddy that clear distinction.
Your Options (from easiest to most complex):
Move the Sensitive Discussion to a Private Forum/Sub-forum:
This is by far the cleanest and most recommended solution.
How: Create a new forum or sub-forum within your existing forum structure. Set the permissions for this specific new forum so that the "Guests" group has "No Access" (cannot view forums, read topics, or read posts). Only "Registered Users" (or a specific "Adults Only" user group you create) would have access to this new forum.
Benefit: It clearly segments the content, maintains the public nature of the rest of your forum, and is supported by the built-in permission systems of virtually all PHP forum software. The two members can have their private conversation there without affecting the main forum.
Utilize a "Hide" BBCode or Plugin (if available for your specific forum software):
Some forum software or community-developed add-ons/plugins offer "hide" BBCode tags (e.g., [HIDE_GUESTS]...[/HIDE_GUESTS]).
How: Users would wrap the sensitive content within these special BBCode tags. When a guest views the post, they would see a message like "Content hidden from guests. Please register to view." When a registered user views it, they see the content.
Caveats:
Availability: You'd need to check if your specific forum software has such a feature built-in, or if there's a reliable, compatible plugin/mod available for your version. Installing third-party modifications can sometimes cause compatibility issues or security risks if not from a reputable source.
Source Code Visibility: Crucially, many simple "hide" BBCodes only hide the content visually using CSS or JavaScript. The actual content might still be present in the HTML source code of the page, meaning anyone could "view source" to see it. This is not suitable for truly sensitive content. For it to be truly hidden, the server-side PHP would need to prevent the content from ever being sent to the guest's browser.
Moderation: You'd need clear guidelines for members on when and how to use this, and moderators would need to ensure it's used appropriately.
Custom Code/Development (Advanced & Not Recommended for this situation):
It is technically possible to modify the core PHP files of your forum to implement post-level visibility checks.
How: This would involve adding conditional logic to the templates and the post-rendering functions that check the user's logged-in status before displaying content.
Why not recommended:
Extremely Difficult: Requires strong PHP and understanding of your forum's specific codebase.
Maintenance Nightmare: Any time you update your forum software, these custom modifications would likely be overwritten, requiring you to re-apply them (and potentially fix them due to changes in the core code).
Security Risks: Incorrectly implemented custom code can introduce vulnerabilities.
Recommendation:
For your scenario, the first option (creating a private sub-forum) is by far the most practical, secure, and maintainable solution. It leverages the existing, robust permission system of your forum software for exactly this kind of use case. It allows for clear boundaries between public and sensitive discussions, and it's something you can likely implement quickly and easily through your Admin Control Panel without needing any custom coding or risky third-party plugins.
***Thank you for this helpful reply! This is a great day for learning new things!
You're most welcome! I'm really glad to hear it was helpful and that you're enjoying the learning process. That's fantastic!
If any more questions pop up as you explore these options for your forum, just let me know. Happy to help!
Calliban, I think the answer is right there! SpaceNut already created a private forum. All we have to do is to create a private forum for taboo subjects.
I'll invite the Admins to consider creating a category or a forum within Meta if that is possible, in which members can place discussion topics that are not suitable for the global audience.
The downside is that the forum would still be visible to children (young people not considered adults) who might become members.
However, perhaps we can create a category of membership with permissions that exclude them from sensitive posts.
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For Calliban re outstanding idea of colonizing passing galactic objects...
https://newmars.com/forums/viewtopic.ph … 13#p233013
This is another of your many first rate ideas. That comet (2024YR) is receiving a lot of press these days.
Please consider the possibility you/(with help?) might be able to turn that idea into a piece for a major recognized publication.
You have the kernel of an idea that a science fiction writer such as Quaoar or perhaps even Terraformer could turn into income and public enlightenment.
If treated as a science fact piece, it would surely fit into the publishing umbra of at least a few major publications.
GW Johnson is a published author in Texas ... he might be willing to give your piece exposure there.
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For Calliban re PhotonByte's idea of harvesting a comet such as Haley's...
https://newmars.com/forums/viewtopic.ph … 22#p233022
Your suggestion of slow nuclear reminded me of earlier discussion in the forum, suggesting that an alternative harvesting method is to collect a ton or so of material in small harvesters. It would be interesting to see what it would take to match orbit with Halley as it passes Earth (or Mars) orbit and collect some of it's mass.
I like your idea of colonizing an interstellar comet such as 31/ATLAS . GW Johnson took a quick look at the dV to match orbit, and my recollection is that it may be beyond human capability in the time available. However, future such visitors should be accessible, with new capabilities. Even if people can't set up shop in the near term, it should be possible to drop an instrument package on the object.
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It was also thought that nuclear ion driven engine using the ice of the comet for fuel was also part of Cere's discusions.
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For Calliban re rocket sled for horizontal take off....
Your recent post on this idea was in mind as I read a report on SSTO status...
I thought you might appreciate seeing that there is at least one company seriously considering your idea:
From Gemini SSTO report July 27, 2025:
A key innovation of Radian One is its plan to replace traditional vertical launches with a unique rocket-powered sled system. This sled is designed to accelerate the spaceplane along a two-mile rail, reaching speeds of Mach 0.7 (537 mph) before the spaceplane's own engines ignite to propel it into orbit. This novel approach is specifically intended to "address the 'tyranny of the rocket equation'" by providing significant initial acceleration without consuming onboard propellant, thereby reducing the required propellant mass fraction for the vehicle itself. This directly relates to the concept of "launch assists" as a strategic engineering solution. By gaining a significant portion of its initial velocity and kinetic energy externally, the vehicle reduces the required delta-v from its onboard propulsion system. This, in turn, allows for a lower propellant mass fraction for the vehicle, potentially enabling a higher payload fraction or more robust reusability features, making the overall SSTO design more feasible. Launch assist mechanisms represent a pragmatic approach to circumventing the fundamental mass fraction challenge of SSTO. They offload a portion of the energy requirement from the vehicle's internal systems, making the design less constrained by the need for ultra-lightweight structures and extreme engine efficiency across the entire flight profile. This suggests a potential future for SSTO where the "single-stage" concept might implicitly include significant ground-based launch infrastructure. It highlights a shift from purely onboard solutions to integrated system solutions that leverage external energy input to achieve orbital access, blurring the lines of what constitutes a "single stage" in a broader operational context.
The Radian One spaceplane is designed for high reusability, targeting up to 100 missions with a rapid 48-hour turnaround time between flights. Once in orbit, it is intended to function similarly to the Space Shuttle, deploying payloads such as satellites and performing missions like Earth observation and defense applications. While technically promising, the economic viability of Radian One remains a "significant question," particularly due to the intense competition from reusable multi-stage rockets from companies like SpaceX, which have already driven down LEO costs to approximately US
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For Calliban re post with link for Void:
https://newmars.com/forums/viewtopic.ph … 68#p233068
I followed the link and instead of watching the video, I read a great number of the comments.
I often find the comments to a video more interesting than the video, and that was the case here.
I got the impression the video was about spinning, and SpinLaunch was even mentioned in one of the comments.
So here is what I'm offering for you to think about....
If we wanted to send a probe to catch ATLAS/31, my understanding is it would be exceedingly difficult with existing chemical propulsion, due to the dramatic dV required for an intercept.
I'm hoping this inquire will inspire you to do some math to see what might be possible.
If we spun up two probes of identical mass, turning around an axis where power is applied (somehow) I wonder what the limits of existing materials might be. If we use a tether of some existing material, and set the mass of the probe at 100 kg (and there are two in this scenario to balance the tether) what velocity might be achieved.
My recollection is that the dV to intercept ATLAS/31 is 30 km/s.
Could a rotating tether system achieve that velocity?
One probe would head for the comet/object, and the other would head out at the same velocity in the opposite direction.
I don't recall anyone thinking about this before, so the video you found may be a first.
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