GW Johnson Postings and @Exrocketman1 YouTube videos

tahanson43206 · 2024-09-12 13:23:56

This post may be of interest to a few NewMars members.

The link below points to an animation that GW Johnson was trying to explain with words and fixed drawings.

https://www.youtube.com/watch?v=XLjnTgXXgXk

It turns out that I had made the same mistake made by millions of others in expecting that an ellipse that is the path of a planet would be skinny at the end near the Sun, and fat far from the Sun. The proof of the equivalence of the shape at both ends is provided in the video.

The specific problem I was having is accepting that the ellipse that results from the cut of a cone by a plane delivers the same result regardless of the angle of eccentricity.

This video deserves a place as a reference for the book project.

(th)

tahanson43206 · 2024-09-20 17:35:22

For GW Johnson...
https://newmars.com/forums/viewtopic.ph … 02#p226702
News from SpaceNut...
(th)

tahanson43206 · 2024-09-22 12:42:52

For GW Johnson....

Tried and true method of study ,.... I recognize elements that apply to the book project...

https://lifehacker.com/use-the-sq3r-met … wtab-en-us

(th)

GW Johnson · 2024-09-23 09:46:56

I was taught something similar in 6th grade English long ago: tell 'em what you're going to tell them, then tell it to them, and finish by telling them what you just told them. The first and last pieces are short forms, the middle piece is the long form.

I like adding the relevance to the reader from the SQ3R thing. It was implied to be in the middle part of the 6th grade English thing. Putting it overtly is a reminder to get that job done.

My 6th grade teacher was the school's football coach (yes there was grade school football in those days). He was the only male grade school teacher I had. I think his name was Charles Brown. He used to make jokes about himself vs the "Peanuts" cartoon strip character of the same name.

GW

GW Johnson · 2024-09-30 10:02:50

From today’s AIAA “Daily Launch”, regarding risks of an aging ISS:

ARS TECHNICA
NASA confirms space station cracking a “highest” risk and consequence problem

US space officials do not like to talk about the perils of flying astronauts on the aging International Space Station, elements of which are now more than a quarter of a century old. However, a new report confirms that NASA managers responsible for operating the space station are seriously concerned about a small Russian part of the station, essentially a tunnel that connects a larger module to a docking port, which is leaking. Russian and US officials have known that this small PrK module, which lies between a Progress spacecraft airlock and the Zvezda module, has been leaking since September 2019. A new report, published Thursday by NASA's inspector general, provides details not previously released by the space agency that underline the severity of the problem.

My take on it:

They seem to have focused on a leaking weld, which is a weld that has cracked. They do not seem to be worried about a crack in the pressure shell. Weld cracking is a serious issue, because it risks a sudden decompression blowout, if it comes apart. This usually is a known metallurgical problem, probably with an aluminum alloy (“duralumin”, aluminum with a dollop of copper in it) or maybe a titanium or steel item.

This WILL get worse as time goes by, because the stresses in the metal cycle with day/night temperature changes every 90 minutes, and that cycling causes fatigue. With aluminum, there is a stress level below which fatigue does not occur, but it is quite low (down near 5-10 ksi). To reduce weight, you go for higher design stresses, and accept the limited fatigue life. That is very likely EXACTLY what you are looking at here.

Steel is similar, but the no-fatigue stress level is much higher (a majority fraction of yield, near 30 ksi). Similar for titanium, although I would hesitate to do any welding on 6-4V (alpha phase) titanium! Fasteners are far more reliable for it. Alpha phase is not formable: you literally carve your parts from ingots. There are a couple of beta-phase alloys that are formable into sheet metal, but they age at only room temperature, and do not respond well to welding. One of them was used for SR-71/YF-12/A-11 skins, and cracked somewhere after nearly every flight.

As for the aging ISS, the risks grow daily (a cycle every 90 minutes) that a weld or a panel somewhere is going to blow out and cause an explosive decompression. That will kill the crew, all of them! They have no place to shelter, and no way to get into a p-suit!

Now do you understand why this thing needs to be decommissioned and replaced by something else, and fairly soon, too? It will “look fine” right up to the point where it fails and kills everyone on board, just like the old Dehavilland Comet jet airliner did back in the 1950’s.

GW

tahanson43206 · 2024-09-30 10:13:11

For GW Johnson re #405 and RobertDyck's Large Ship

The deterioration of the ISS, detailed in your post, is happening to a vehicle that is NOT rotating once every 20 seconds, as ships designed along the lines of RobertDyck's Large Ship will be doing.

RobertDyck put development on the back burner, but he could return to the project at any time.

What advice do you have for folks who are now or will be designed large rotating vessels and stations?

Is there a way to design so that some components can be replaced quickly and easily?

Could the ISS have been so designed?

I understand the ISS is a special case because it was driven in large part by the urgent need to try to capture Russian good will when there was an opportunity.

(th)

GW Johnson · 2024-09-30 13:26:24

There are two kinds of cyclic stresses: (1) actual alternating loads, and (2) cycling thermal stresses. But stresses are stresses, regardless of how produced, and if they cycle, fatigue is the risk. If you design down at the infinite fatigue life stress level, aluminum's low density advantage disappears, because you have to use so much of it. But all the metals need to be used at their infinite fatigue life stress levels, unless you can justify accepting a finite life just to get a lighter structure. They do that with airplanes: usually at 40,000 cycles. That gives you many years, even decades of service life at the cycling rate aircraft see: a single handful of flights per day.

Spacecraft are different: there is thermal stress cycling for anything in orbit, as it sees day and night on a rate equal to the orbital period. Exposure to occasionally-higher stresses just shortens the number of cycles to failure. And some exposures will deform the craft or structure, if yield stress is exceeded. Only a rank amateur would ever try to size a structure using its material's ultimate strength! (I see a lot of rank amateurs do exactly that, though! In all sorts of venues, not just this forum.)

We have gotten about 3 decades of service life out of the ISS so far, and likely nearing 4 decades by the time they deorbit it. The concern is that a cracked weld is leaking, and the leak rate is increasing. That means the crack is growing, and they still do not know where it is, despite 2-4 years of looking for it. The risk of a fatal explosive decompression is getting rather large now! It may no longer be wise to continue trying to use the structure without trying to make an effective repair (which so far they have been unable to do).

Structures that rotate should not see cyclic stresses, unless they are out of balance and wobbling. But the things I called out regarding staying below the stress for infinite fatigue life still apply, as all space structures will see thermal cycling due to day/night exposures. My best recommendation is you NEVER obscure access to the pressure shell from inside the pressurized spaces. That way is much easier to trace a leak and find the crack. Once found, you drill out its ends with small bit to relieve the stress concentrations there by radiusing the sharp ends of the crack, and then you can patch over it (which is WAY easier from the inside pressurized space).

Few spacecraft designers follow my advice, though, which is why in 3-something years they have not found the leaking cracked weld in the ISS module, nor could they find the leaking holes in at least two Soyuz spacecraft docked to it.

GW

PS -- don't tell me that composite materials do not experience fatigue. They do accumulate damage over time, but the mechanism is not usually a crack, so they don't use the word "fatigue". It's most commonly delaminating de-bond between fiber and matrix. But the material life is limited, regardless of what you call this effect. There are NO materials that last "forever". Not even wood: there is cumulative damage for wood under cyclic loads, plus there are two different types of rot. And strength depends very strongly on moisture content. It is extremely unlikely that there ever will be any material with an unlimited life under cyclic stresses.

PPS -- no, I am not a materials engineer, nor am I a professional stress analyst. I trained in aerodynamics, thermodynamics, heat transfer, and propulsion. But I had to learn a whale of a lot about the other disciplines, enough to be competent in them, in order to be effective on the job in the kind of defense work we did. My usual role was tying together the other 1-or-2-specialty specialists into a team,
by acting as a "chief engineering scientist", as well as a specialist in some other things my colleagues couldn't cover, such as inlet characteristics and fuel-air combustion aerodynamics.

Last edited by GW Johnson (2024-09-30 13:44:30)

tahanson43206 · 2024-09-30 14:33:12

For GW Johnson ....

Thanks for that long post #407, with details and examples of various kinds of stress loads on metal.

Bearing in mind that you are not an expert in the field, but instead are doing the best you can to explain a complex behavior of materials, I think that the question of how to deal with metal fatigue in a vehicle in flight needs attention.

Because we have at least three members with US Navy experience (military or civilian) I am guessing that metal fatigue of large structures that must endure all the stresses that the open ocean provides has received a ** lot ** of attention over centuries. A requirement for RoberDyck's Large Ship is that it must be as light as possible. At the same time it must be resilient in the face of all that challenges that come from flight in open vacuum.

Where I'm headed with this is a concept of self-healing structures.... I've read that some work has been attempted along these lines, but I think the work has been with Carbon, which is such a versatile atom.

(th)

GW Johnson · 2024-09-30 15:58:35

There is nothing in Mil Handbook 5 about any materials that are "self-healing". If a material is not listed in there, it is considered not yet ready for application. And that's for the military, who get away with doing things civilians are just NOT allowed to do, under a variety of laws and regulations. A notable exception was beta-phase titanium, which is still not in Mil Hndbk 5, but was used to build the SR-71's long ago. As I said, the military can get away with things that civilians are not allowed to do.

GW

GW Johnson · 2024-10-01 09:58:22

The ISS leak was in today's "Daily Launch", for the second straight day. This time the article was far less clear, and read like an attempt to calm the fears the first article would create. It claimed they all-of-a-sudden reduced the leak rate by some undescribed repair, but did not identify what that was, while simultaneously claiming they still did not understand why they had a leak (which is quite contradictory, so I know the second article is just PR BS from NASA management to the media).

The first article said they closed the door to the leaky module when it is not being used, to limit the atmosphere leakage from the ISS to just that module, into space. It is a tunnel module connecting the rest of the ISS to a Soyuz docking port module, in the Russian portion of the station.

It is quite unclear whether this is a hole somewhere (like two previous Soyuz capsules), a crack in a panel, or a cracked weld. A hole could be a drilling or space debris impact. The first article said they have been looking for it for a long time but still have not located what is leaking or why. That I believe!

But if it is a cracked weld or panel, that is extremely serious. Such cracks always grow in cyclic loading, and how far they can grow before catastrophe happens, is quite finite. We are talking air leak rates on the order of a kg a day or more. This is no pin-hole leak. Which is why the ISS team classified it and its consequences as their worst case evaluations.

GW

tahanson43206 · 2024-10-01 11:41:28

For GW Johnson re #410, but also an interesting post in the Asteroid deflection topic ...

Re #410

I haven't read any reports about this ongoing problem, other than yours, so am hoping you might be willing to consider a couple of questions.

1) Have there been any attempts to use tracer atoms (ie, radioactive) to show where air drifts as the leak does it's thing?

2) Related.... what does "looking for the leak" mean in this context?

3) Risk question: It is possible to pressurize the module to try to create more visible evidence of the leak activity. Does that increase risk of blowout?

****
Regarding the asteroid deflection post ....

If you have multiple years warning (AND you have developed the right kinds of spacecraft and ion engines !!!), you can employ the gravity tractor. But ONLY if you have multiple years of warning! That kind of deflection does not significantly disrupt even the C-types, because the applied "push" is the same magnitude of strength as the binding force.

I know you meant that quotes around "push" would be read by a sophisticated reader as "pull", but why not just say pull in the first place?

The machine you're describing sounds like a gravity tractor.

There is no "push" involved with a gravity tractor, except the "push" on the tractor, which is vanishingly small, because it needs to be small enough not to escape the tiny gravity of the object to be manipulated.

Upon reflection, it occurs to me that the greater the mass of the tractor, the more effective it will be, so if our hypothetical deep space defense force has enough resources to put a tractor near a rubble pile, it might as well put the largest (most massive) tractor in position that it can.

(th)

GW Johnson · 2024-10-01 13:03:58

I cannot answer most of your questions because those answers are not in any of the reports I have seen.

All of the ISS is pressurized to about 1 atm of synthetic air (21% O2, 79% N2). That would include the leaking tunnel module, except when that hatch is closed. Then only that module (and presumably the docking adapter it connects to) leaks down, without leaking down the pressure in the rest of the ISS. Nobody says, but I presume they have to equalize by bleeding air (somehow) into the leaky module before they can re-open the hatch and use the docking adapter.

I have seen absolutely nothing describing how they have been searching for the leak.

Any impactor to an asteroid is a "push", meaning compression in the material underneath the impact point. The gravity tractor is actually a "pull", because the force on the asteroid is directed toward the spacecraft, and the force on the spacecraft directed toward the asteroid. The spacecraft thrusts to keep from being pulled onto the asteroid. That thrust has to be canted at rather strong angles, so that the expelled mass streams DO NOT strike the asteroid, but instead just pass it by. Ion, other, makes NO difference.

Most people think you use a nuclear device as a direct surface impact, or even exploded within the asteroid, but that IS NOT correct! There is no blast wave in a vacuum. You explode the thing alongside very close by, and use the radiant energy to overheat and vaporize the adjacent asteroid surface materials. Those vaporized materials "explode" into space quite violently, causing a big "rocket reaction" force in the opposite direction. The spalled material from an impactor works exactly the same way. Neither approach can be used on a dry C-type (excepting the very smallest, rather inconsequential impactors), because the asteroid will disrupt into a cloud of debris instead of accelerating in the "push" direction.

And yes, the larger the mass of the gravity tractor craft, the more effective it will be. And the larger your thrust requirement, the more expensive your construction, and the more demanding your launch problem. It's a very complex trade-off. Nobody yet knows the right answers, because it has yet to be attempted in any form.

GW

Last edited by GW Johnson (2024-10-01 13:07:02)

tahanson43206 · 2024-10-01 22:08:30

For GW Johnson....

This post by kbd512 is in a topic you might miss if you are limited in time, which seems likely...

https://newmars.com/forums/viewtopic.ph … 09#p226909

The post is a follow up to a post by Calliban about stronger concrete.

I bring this up because you had indicated you are not familiar with 'self-healing' metal, and what kbd512 is talking about is not "self healing" so much as it is tear resistant. What I'm wondering is if the metal used to make space craft might have some feature like this, to help to prevent massive blowout due to the incessant stress cycles of space travel.

(th)

GW Johnson · 2024-10-04 15:35:47

From AIAA’s “Daily Launch” email newsletter for October 4, 2024

SPACE
Top 'safety risk' for the ISS is a leak that has been ongoing for 5 years, NASA audit finds

The ISS has been dealing with a leak in its Russian segment since 2019. As NASA and Roscosmos work to solve it, a new report says the leak is a primary...

My take on it:

If you follow the link to the Ars Technica article, you find out that the 5 year history is all low leakage rate until very recently. The leakage rate increased recently to something over 10 times higher. That smells (to high heaven!) of a crack either getting much longer or another crack forming in addition to the first. This is apparently some sort of fatigue crack failure, either in a component or in a weld somewhere. And they still do not know where it is, which means they cannot even in principle fix it.

I read a lot of discussions about the budgetary, international competitiveness, and reputational issues raised by this problem, but I read very little about crew safety, and that alarms me greatly! This is exactly the same kind of management thinking that preceded both of the fatal shuttle losses. It is happening again!

You are looking at a fatigue crack somewhere in a pressure shell that sees a pressure drop rather near 14-something psi inside-to-outside, under cyclic thermal expansion-induced loads every 90 minutes, with that crack ALREADY starting to grow more rapidly than before! Sudden increase in crack growth means failure is “imminent”, whatever time interval that might really be.

The consequences of the cracked part (whatever it is) actually failing are quite horrific: a sudden explosive decompression, likely of the whole ISS, unless the door to that module is closed and sealed. That whole-ISS decompression would inherently cause the loss of the entire ISS crew, if it were to occur.

Compare that to the fatigue failures that downed multiple Comet jet liners in the mid 1950’s, with loss of all aboard every time, in a complete midair breakup of the aircraft. That also turned out to be fatigue cracking, on a pressure shell seeing only about 7.3 psi pressure difference inside-to-outside. Fatigue was not well-understood then; but that “excuse” certainly does not obtain now!

My recommendation: close that damned door to the leaking module! Only open it when you must use that docking port, and when you do, close another door somewhere else, to limit how much of the station depressurizes, if the module does fail!

And when it does fail (and eventually it will!), that will be a very sudden event, and there will be no warning! Same as the Comet jetliners 7 decades ago.

GW

Last edited by GW Johnson (2024-10-04 15:36:41)

tahanson43206 · 2024-10-04 15:44:51

For GW Johnson re #414

Could that module be vented to space? The docking port could be opened as well, of course.

That would put vacuum on the inside door of the module. Could it handle that? Is that a two-door system?

Would this change allow the fatigue site to do it's thing without a massive blowout?

(th)

GW Johnson · 2024-10-04 18:24:51

TH:

Think of it as a sine wave superposed on a DC level. The sine wave is the day/night cycle of thermal expansion and contraction, from the solar illumination or darkness every 90 minutes or thereabouts. The DC level is the pressure inside the shell, which is just pretty near 1 std atm. The DC level makes the basic stress level higher, while the sine wave is the cyclic part. It's too late to reduce stress below that for infinite fatigue life: the damage is done, the crack is there (and leaking).

These considerations do not depend on whether that is a weld or some shell panel. Only the specific numbers for cycles-to-failure. Most of what I read at least implies this is some cracked weld somewhere. Those fail quicker than the base aluminum, usually. But they haven't found it in 5 years of looking, so nobody really knows what is the true problem.

Metallurgically speaking, a sudden increase in crack growth rate occurs right before the fatigue sample actually fails, in the usual cyclic loading test scenarios. This is a piece of the module pressure shell, or there would not be a 5-year leak history. With the leak rate accelerating by over a factor of 10 very recently, we "know" that failure is "imminent". Failure means explosive decompression, likely fatal for the crew, unless that door into the leaking module is closed and sealed.

It really is that simple. And that dangerous in space. The biggest problem is that with no details, there is no definition of "imminent". Except my gut intuition says it ain't years anymore. Months? Weeks? Days? Who knows?

GW

Last edited by GW Johnson (2024-10-04 18:28:39)

tahanson43206 · 2024-10-04 18:36:18

For GW Johnson re #416

Thanks for additional detail about what will happen if the module remains pressurized.

I am curious to know what would happen if the air in the module were allowed to vent to Space.

I asked Google, and it surprised me by revealing that this appears to be a scenario that has been considered...

AI Overview
Learn more…
The Russian Zvezda module of the International Space Station (ISS) has been leaking air since 2019:
In June 2024, NASA's Office of Inspector General (OIG) elevated the leak to the highest risk level in the ISS's risk management system.
By April 2024, the leak rate had increased to 3.7 pounds per day.
The leak is in the service module transfer tunnel of the Zvezda module, which launched in 2000.
NASA and Roscosmos, the Russian space agency, are working together to address the leak.
The area can be sealed off to reduce air loss from the rest of the station.
If the leaks continue, NASA and Roscosmos may need to permanently close the hatch to the affected tunnel.
This would cut astronauts off from using one of the four docking ports for the Russian segment.

The option of losing a docking port is apparently under serious consideration.

(th)

tahanson43206 · 2024-10-09 07:32:19

For GW Johnson...

Now that you are safely returned from your strenuous and challenging travels around the American West, I am hoping you might have a moment to look at a post by Calliban...

https://newmars.com/forums/viewtopic.ph … 34#p227134

The above link is my reply to Calliban's original post. What I'm hoping you might find interesting is an estimate of what it would take to move a single passenger with minimal baggage and supplies from the cycler to Mars, or to Earth for that matter, on a return trip.

What I am proposing is to use Calliban's luxurious cycler for the long leg of a trip, and a high speed, high G taxi to make the plane changes and velocity change to deliver the passenger swiftly to the destination planet or object.

There should be quite a significant set of business opportunities around the cycler, including supply for the cycler itself, and the support services at various destinations.

In deep space atomic powered taxi concepts should be possible. The long arm of the Terran Government will be ever-present but perhaps less effective outside the Lunar orbit.

(th)

GW Johnson · 2024-10-11 09:43:38

Tom:

I think the end result of my thinking about cyclers, limited as it is, is that you are likely better off with a large artificial space habitat placed in the correct cycler orbit. It is unlikely in the extreme that there will be an asteroid in the correct orbit to use. As near as I can tell, there is one and only one possible orbit that could host an Aldrin cycler between Earth and Mars. The odds of any sort of celestial body actually being in that exact orbit are pretty much zero. The cycler will need propulsion for course corrections, because every planetary close pass will disturb the cycler from its proper orbit by the 3-body effect.

Meanwhile, I have also been looking at the process of moving from exploration to colonization of Mars (or anywhere else). As presented in my convention paper at the Phoenix convention, I still maintain there are 3 distinct phases to this, with different mission requirements, different vehicle design constraints, and different levels of appropriate governmental involvement. Those phases are exploration ("find out what all is there, and where exactly it is located"), experimental permanent bases learning how to live off the land, and what everybody thinks of as real colonization: building big settlements. There is some overlap of vehicles between exploration and experimental base, but none with settlement.

To that end, I have re-looked at the exploration vehicles, particularly one-way unmanned cargo delivery, to incorporate the Void idea of using cargo containers as soft, rough field landing pad surfaces, plus elliptic departure tug assist, with a reusable tug stage. It's starting to make real sense now, simpler than what I came up with before, and smaller. I have a transit vehicle of about 115 tons that delivers 39 tons of dead-head cargo by direct entry and rocket braking. This thing needs a reusable departure stage tug around 90-100 tons in size. I did not push the state-of-the-art in either rocket performance or in reducing inert masses. The transfer stage uses NTO-MMH. The reusable tug uses LOX-LH2, and I tried to account for evaporative losses on a 4-day elliptic departure orbit. It took two attempts before I found a feasible solution, and then I had to refine that.

I'm putting all this together as a series of PowerPoint slide sets first. I can write documents from those, once the stories "gel". I am one hell of a long way from done. But this does suggest another book of some sort.

GW

tahanson43206 · 2024-10-16 17:30:18

And here is an image to go with Post #419

(th)

GW Johnson · 2024-10-16 20:40:39

What's in post 420 is a sketch I created that pertains to a manned orbit-to-orbit transport between Earth and Mars, of an approach different from what was in my Mars mission plan from 2016. This one is bigger, and uses rifle-bullet spin for artificial gravity, instead of baton spin, as in the 2016 plan. But this is NOT a "large ship", this is for smaller crewed missions, not passenger service for settling the planet. What's in the two counter-rotating disks are work stations, gymnasiums, eating facilities, and such like, not staterooms. This thing could either fly orbit-to-orbit with a large propulsion stage, to be refilled on orbit at Mars with pre-positioned propellant supplies, or it could serve as a cycler station with a smaller propulsion unit for course corrections. I have NOT sized power supplies or propulsion units for it.

The cargo delivery vehicle NOT shown in post 420 is unmanned, and travels one-way from LEO to a direct entry and landing at Mars. There is a transit vehicle composed of cargo containers and propulsion cores, with heat shielding on the bottoms of the cargo containers. There is a reusable tug departure stage that assists the transit vehicle to depart from an extended elliptic orbit to reduce the transit propulsion requirement. The cargo containers also serve as enormous landing pads in a configuration designed around rough field stability and low bearing pressure for soft field suitability. This thing delivers about 39 metric tons of dead-head cargo inside the containers per flight. The cargo container doors are at ground level after landing, for unload not unlike shipping containers here. The loaded transit vehicle is about 115 tons, and the tug departure stage about 70-75 tons. That design is pretty much roughed-out, and meets all requirements in its final form.

GW

Last edited by GW Johnson (2024-10-16 20:41:56)

GW Johnson · 2024-10-19 13:14:28

BTW, for the crew orbit-to-orbit transport shown in post 420 just above, I did NOT overtly specify an atmosphere. I just specified near 1 full gee at the rim of the two centrifuge disks. There is NOTHING that inherently links atmosphere choice to gee-level choice. I picked 1 gee to ensure that all aboard would be physically fit to endure entry and landing gee levels in the 3-6 range with impunity, as can ordinary untrained Earth citizens.

We have absolutely no experience, or any evidence, to suggest that people acclimatized at 0.38 gee can withstand the 3-6 gee exposures that are inherent for the landing on Mars! In my opinion, the lower gee level is a totally unjustified risk! Suspenders, belt, and armored codpiece! Especially where paying passengers are involved!

In point of fact, I would use about 43%-by-volume oxygen in a two-gas mix with nitrogen, at a pressure in the neighborhood of 0.43 atm. That's my "rule of 43" atmosphere proposal. That atmosphere meets all the long-term and short-term hypoxia-prevention criteria I can identify, while at the same time allowing no pre-breathe requirement for pure oxygen spacesuits down to 3.0 psia suit pressure! There would be no pre-breathe needed for any spacesuit designs at or above that 3 psia figure!

And that's actually lower than the 3.7 psia used in the Mercury/Gemini/Apollo suits very successfully! It also makes MCP suit design and operation a lot easier! Dr. Webb designed his at 3.7 psia, give or take a tad. They pretty much become infeasible above about 4 psia.

And, the oxygen concentration (calculated as kg/cu.m) never exceeds that in 77 F air at 1 atm pressure, so any fires are NOT accelerated above the Earthly rates we have fire-fighting experience with, by the 43% oxygen! They would be accelerated at higher pressures with the higher kg/cu.m of oxygen, but not at 0.43 atm. You have to worry about this! It killed the Apollo-1 crew on the pad, remember?

And yet, my proposed atmosphere's oxygen partial pressure does not fall short of that in Earthly air at about 2500 m altitude, above which there are higher incidences of birthing problems and also higher incidences of chronic altitude sickness, but not below! Any settlements or cities we build out there in space or on Mars could use the same atmosphere, and not fear reproductive failures induced by chronic hypoxia!

GW

Last edited by GW Johnson (2024-10-19 13:32:30)

tahanson43206 · 2024-10-19 13:38:14

For GW Johnson re counter-rotating ship design....

RobertDyck's Large Ship project(topic) lasted two years, and it came to a screeching halt when the attempt was made to figure out how to build the system.

An assembly plan requires a bill of materials, and generally that follows completion of a set of drawings.

It is going to take some time and investment of a fair amount of human thinking time to put those two together.

My assumption is that your design, like that of RobertDyck, must be assembled in orbit, and that with the total omission of on site humans for most roles. I see no reason for on site humans with the advent of reliable remote presence systems, so their requirements can be eliminated from the planning.

The vessel itself ** will ** be a human habitat when it is finished, or at least when enough is finished to support human presence.

(th)

GW Johnson · 2024-10-23 09:08:34

To assemble large things in orbit, there are two possibilities: (1) simply dock together modules that you can launch with your existing rockets, and/or (2) assemble components together "from scratch" in a sort of shipyard-in-space, which components can be launched up there by the rockets you have. (1) is how we built the ISS. We have never done much toward (2) at all.

But (2) is the only choice for creating really big vessels in orbit! You will have to join together pieces to create frames and stringers, and then attach plates to them. Rivets? Bolts? Welding? Whatever. Cargo containers full of such components have been envisioned for assembly into large structure on orbit, since about 1940. But we have never really done it, except on a very small scale, such as servicing components on the Hubble.

But, we're going to have to learn how to do such assembly in orbit, and we will need an orbital facility for that, in order to send crews to Mars and elsewhere, without a colossal expense at every mission. The colossal expense is inherent in building and operating the orbital shipyard, but not as a continuing thing with every mission. Going to Mars and elsewhere just cannot be done only capsules and LM's on a rocket, the way Apollo went to the moon. Radiation and microgravity diseases say that is just the wrong concept for long missions.

GW

Last edited by GW Johnson (2024-10-23 09:10:41)

tahanson43206 · 2024-10-23 13:08:34

For GW Johnson re assembly in orbit....

You've already proposed a fuel depot.

Your choice for that facility is relatively low in LEO terms, which is advantages for numerous reasons, but it does require more frequent boosts as part of the cost of doing business.

My question follows on from the discussion of assembly ... can the two facilities be part of the same complex?

There would be plenty of advantages for that as well.

A large facility is NOT going to be playing dodgem, as the ISS has been doing.

It seems to me a large facility is going to need to clear the path in front of it.

The "rules of the road" would be similar to maritime rules, giving precedence for right-of-way based upon mass of the vehicle.

(th)

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#401 2024-09-12 13:23:56

Re: GW Johnson Postings and @Exrocketman1 YouTube videos

#402 2024-09-20 17:35:22

Re: GW Johnson Postings and @Exrocketman1 YouTube videos

#403 2024-09-22 12:42:52

Re: GW Johnson Postings and @Exrocketman1 YouTube videos

#404 2024-09-23 09:46:56

Re: GW Johnson Postings and @Exrocketman1 YouTube videos

#405 2024-09-30 10:02:50

Re: GW Johnson Postings and @Exrocketman1 YouTube videos

#406 2024-09-30 10:13:11

Re: GW Johnson Postings and @Exrocketman1 YouTube videos

#407 2024-09-30 13:26:24

Re: GW Johnson Postings and @Exrocketman1 YouTube videos

#408 2024-09-30 14:33:12

Re: GW Johnson Postings and @Exrocketman1 YouTube videos

#409 2024-09-30 15:58:35

Re: GW Johnson Postings and @Exrocketman1 YouTube videos

#410 2024-10-01 09:58:22

Re: GW Johnson Postings and @Exrocketman1 YouTube videos

#411 2024-10-01 11:41:28

Re: GW Johnson Postings and @Exrocketman1 YouTube videos

#412 2024-10-01 13:03:58

Re: GW Johnson Postings and @Exrocketman1 YouTube videos

#413 2024-10-01 22:08:30

Re: GW Johnson Postings and @Exrocketman1 YouTube videos

#414 2024-10-04 15:35:47

Re: GW Johnson Postings and @Exrocketman1 YouTube videos

#415 2024-10-04 15:44:51

Re: GW Johnson Postings and @Exrocketman1 YouTube videos

#416 2024-10-04 18:24:51

Re: GW Johnson Postings and @Exrocketman1 YouTube videos

#417 2024-10-04 18:36:18

Re: GW Johnson Postings and @Exrocketman1 YouTube videos

#418 2024-10-09 07:32:19

Re: GW Johnson Postings and @Exrocketman1 YouTube videos

#419 2024-10-11 09:43:38

Re: GW Johnson Postings and @Exrocketman1 YouTube videos

#420 2024-10-16 17:30:18

Re: GW Johnson Postings and @Exrocketman1 YouTube videos

#421 2024-10-16 20:40:39

Re: GW Johnson Postings and @Exrocketman1 YouTube videos

#422 2024-10-19 13:14:28

Re: GW Johnson Postings and @Exrocketman1 YouTube videos

#423 2024-10-19 13:38:14

Re: GW Johnson Postings and @Exrocketman1 YouTube videos

#424 2024-10-23 09:08:34

Re: GW Johnson Postings and @Exrocketman1 YouTube videos

#425 2024-10-23 13:08:34

Re: GW Johnson Postings and @Exrocketman1 YouTube videos

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