Bravery Is Taking a Stand

This one needs very little in the way of comment.  So far,  too many have bowed the knee to the would-be dictator.  Bravo to Harvard for standing up to him! 

86 47

Learn to Count?

Trump’s buddy Musk is the target of this one,  also too funny not to share.  Since this is his last official day as head of DOGE,  I thought I’d better post this quickly. 

86 47

Trump vs Hitler

I’m not the only person who has noticed these similarities.  My wife found this on Facebook.  History may not actually repeat itself,  but it often rhymes!  You are losing your democracy,  the same way the Germans of the 1930’s lost theirs.

86 47

Trump and Putin?

Putin does not actually want any peace in Ukraine without totally destroying or conquering it.  He never did.  That is why Trump,  after all these years,  perhaps finally came to realize (at least a little bit) that Putin considers him a lap dog,  not a friend among equals. 

In turn,  that is why Trump is now publicly lashing out verbally at Putin.  Except that,  being the egregious liar that Trump demonstrably is,  we should not believe anything he says,  we should only look at what he actually does. 

If he switches sides back to Ukraine,  AND ACTUALY HELPS TO DEFEND THEM,  then MAYBE we can believe his apparent switch from being Putin’s lap dog to being an opponent of Putin!  I’ll believe it when I see it happen,  and not one second before!

But even if he does switch back,  the earlier switching sides to support Putin IS STILL TREASON of the aid and comfort type!  No matter what mistaken prosecution immunity the Supreme Court might have given him,  he is still subject to impeachment and removal for committing treason as President. 

Congress,  do your sworn duty!   Either that,  or else be complicit in Trump’s treason!

86 47

Comey Seashell 86 47 Photo

This photo posted on Instagram by former FBI director James Comey got him investigated by the Secret Service as a possible threat.  The more-or-less “standard” definition of the slang term “86” is to ditch something,  meaning get rid of it.  The usual connotation is something nonviolent and nonlethal,  although the term is very occasionally used to mean “kill something to get rid of it”. 

Given the more-common nonviolent meaning of “86”,  the juxtaposition “86 47” simply means “ditch or get rid of Trump”.  That’s something a lot of us would like to see happen,  while we still have a democracy left.  Here is the offending photo that Comey took and posted,  of something created on the beach by someone else:

Everybody ought to be posting this (or something similar) somewhere!

What To Do To Oppose a Trump Dictatorship

The following quote is the text of a letter I sent by email to the Washington DC offices of Representative Pete Sessions,  and Senators John Cornyn and Ted Cruz. 

Quote:

Donald Trump has been committing treason of the “aid and comfort” type,  in full view of the public,  in two related ways.  One is damaging our NATO alliance to the point our allies no longer believe we will come to their aid,  if they are attacked.  The other is promoting a “peace” solution for the Ukraine-Russia war that gives Ukrainian territory occupied by Putin’s Russia,  to Russia as a condition for ceasing hostilities,  which is a “win” for Putin by his own definition!  We can argue about the Supreme Court’s decision giving Trump immunity from federal prosecution for his “official acts”,  but there is no implied immunity concerning impeachment for his acts of treason,  as witnessed by millions on live television.

Trump has been extorting various universities,  media companies,  and law firms to do what he wants,  by withholding their funding,  and in Harvard’s case,  by threatening their tax status because they would not submit.  Extortion is a very serious crime in all 50 states!  Again,  we can argue about any prosecution immunity per the Supreme Court,  but this really is a crystal-clear case of his abuse of the powers of his office!  Abusing the power of his office is an impeachable offense,  and has been,  since the very founding of the Republic.

Trump through his minions has deported thousands of illegal immigrants (and a few bona fide legal US residents) to foreign prisons without any due process,  and has a demonstrated history of defying court orders about this process.  This is in utter defiance of the Constitution that he swore to uphold at his inauguration!  He has said in public that he thinks his “policies” pre-empt Constitutional due process protections.  This is a horrifying violation of his oath of office,  and of his duties as President!  It may not be prosecutable,  but it is most definitely impeachable!

I am calling upon you to put a stop to these gross offenses!  Grow a spine and oppose this would-be dictator,  while there is still time!  Do the job you swore to do,  when you took your oath of office!  Or else you are demonstrably complicit in all of these crimes and offenses!

End quote.

The extortion and deportations,  with demonstrated contempt for due process of law,  are possible because Trump’s appointees are not generally qualified or even competent,  but instead utterly loyal to him:  they are willing to commit any atrocity or illegality that he wants.  That has effectively weaponized many agencies for retribution against Trump’s enemies,  and together with massive indiscriminate layoffs,  rendered many others dysfunctional with internal chaos.  Those are the hallmarks of conversion to dictatorship seen before in history,  with many previous “fearless leader” cults.

To this I would only add Trump’s egregious lying to the public,  about almost everything.  Nearly every time anybody has fact-checked his claims,  it’s been “pants on fire” or very nearly so!  There is absolutely no logical reason to believe anything he says,  about the economy,  about immigration,  or about the effects of any of his policies upon you! 

You might not want to hear that,  but so say the facts!  You are entitled to your own opinions about any of these things,  but you are NOT entitled to your own “facts”!  There really is such a thing as objective fact and objective truth.  And for the broadcast news media,  many of you seem to have forgotten some years ago,  that reporting the objective facts and truth out-prioritizes any equal time given to political opinions.  The recent extortion is making that failure worse yet.

As to Presidential impeachment,  Andrew Johnson was impeached but narrowly acquitted,  essentially for abuse of his powers of office just after the Civil War.  Richard Nixon was about to be impeached,  but resigned before it could happen,  over the same basic abuse of powers offense,  regarding Watergate.  Bill Clinton was impeached,  but acquitted,  over lying to the public about a sex act in the Oval Office with an intern.  Donald Trump was impeached twice during his first term as President,  and narrowly acquitted along party lines by the Senate both times,  for essentially the same abuse of powers offense as Johnson and Nixon,  plus inciting the Capitol riot (an insurrection against the government). 

This time around,  Trump has (1) two counts of treason,  (2) multiple counts of abuse of powers,  many leading toward establishment of a dictatorship,  and (3) thousands of counts of egregiously lying to the public,  as the grounds for impeachment yet again.

I’d much rather see this done within the laws and institutions that we have (but soon,  before Trump can completely destroy them).  Revolution in the streets is a lot messier and harder to clean up afterward.  But it has to be done,  one way or the other,  and soon,  before the conversion to a dictatorship is complete (which is what the Trump “fearless leader” cult is really all about)!  

What I recommend you do:  contact your federal representation often,  and encourage them to do something about these crimes and that threat to our democracy!  Myself,  I have done so around half a dozen times in only the last couple of months,  and I will continue! 

I also think that Trump will sooner or later become aware of me,  and try to take his retribution by abusing my Social Security or my Medicare,  or by using the IRS against me,  or by even trying to deport me (a 5+ generation native-born American citizen) without due process.  He could do that to any of you! 

But,  I consider this opposition to him my civic duty!  My oath of office upon entering the Navy more than half a century ago demands it,  and it had no expiration date!

If a majority of public input runs against Trump in their feedback from constituents,  some few of these Republican representatives who are not part-and-parcel of the Trump “fearless leader” cult,  might actually try to do something about him.  Faint,  but a hope!

For all of them,  their oath of office demands it,  yet so many fail to abide by their oath,  which should tell you all you need to know,  come election time,  if we ever actually have any more real elections!  It takes only a simple majority in the House to impeach,  but a 2/3 majority in the Senate to convict.

Thurgood Marshall was right!  Make your voices heard!  Or else fight it out hand-to-hand in the streets!  THAT is where we currently are! 

-------   

Update 5-23-2025:  I have sent email letters to my 3 federal reps every week since posting this,  beyond those mentioned in the posting as having been sent before this was posted.  I really am practicing what I preach!  I just sent anther today.  And I will continue sending them!  I urge all of you to do the same!  Unless they hear otherwise,  they will continue to believe Trump and his miscreants have majority support,  and will act accordingly.  

-------   

Re-Entering Space Junk Threats

Update 5-10-2025:

A close version of this article appeared as an opinion column in the Waco "Tribune-Herald" newspaper on Saturday,  10 May 2025.  I happen to be on their board of contributors.

--------------------------- 

News stories have it that sometime this week Kosmos 482 will be entering the Earth’s atmosphere uncontrolled,  after 53 years of being lost in a decaying orbit.  This is the Venus atmospheric entry craft for a Russian probe to Venus launched in 1972.  It failed to leave Earth orbit.  Most of it came apart and reentered years ago,  but this entry capsule did not.

This thing could come down anywhere on Earth between 51 degrees north latitude and 51 degrees south latitude!  It weighs about 1100 lb (or 500 kg).   It is an entry craft design,  so the claims that it will likely burn up in the atmosphere are hogwash!  It was specifically designed to survive that! 

Update 5-10-2025:  Kosmos 482 fell to Earth today,  Saturday,  10 May 2025.  Most reports do not know where,  although Roscosmos in Russia says it fell in the Indian Ocean. 

Update 5-23-2025:  It apparently fell west of Jakarta in the sea,   very near Indonesia.  Much of southeast Asia was close enough to have been at serious risk,  as it turns out. 

It has a landing parachute designed for Venus’s thicker atmosphere,  but after 53 years in space,  that might not work,  and certainly the controls to deploy it might not work.  Which means you will most likely have around a half-a-ton object,  coming down to hit at a few hundred miles per hour,  and all in one big piece!  The odds are roughly 2 against 1 that it will hit ocean.  That’s mostly empty water,  but there are people living on islands out there!  There are also ships and planes at risk crossing the ocean,  not to mention the many risks on or over land.

There’s more space flights in recent years,  so we have seen more space junk coming back.  There was a half-ton chunk of metal fell on a village in Africa,  and a Florida house struck by a chunk of steel weighing several pounds.  Some of this debris has been identified,  some not.  Most of it came from things not designed to be re-entry craft,  yet they still hit the surface,  at least as several pieces.  The point is,  there’s now enough of it,  and it is large and heavy enough,  to be a significant risk!

Up to now,  the pronouncements have been (1) it’ll most likely fall in the ocean (true) and (2) it will mostly burn up in the atmosphere before striking the ground (not true). 

This one (Kosmos 482) is an entry vehicle.  Kosmos 954 that fell in Canada back in 1978 was a Russian spy satellite not designed for re-entry,  that had a nuclear reactor aboard.  It made a radioactive mess to clean up in multiple Canadian lakes and a swath of arctic land hundreds of miles in extent!  Reactors are designed for high core temperatures:  the claim that it “would burn up on entry” was patently false,  even then. 

The US space station Skylab fell on western Australia a couple of years later.  The Space Shuttle was supposed to re-boost it,  but ended up not even making its very first test flight until a couple of years after that crash.  Skylab was converted from the thin propellant tankage of a Saturn-5 third stage.  It weighed about 85 or 90 tons at entry and it did break up,  but not very many of the pieces burned up!  The Australians claimed to have picked up some 75 tons of Skylab debris,  including a 1-ton film vault that was almost entirely intact.  So much for the “these things burn up on entry” theory!

The loss of Shuttle Columbia halfway through re-entry over Texas in 2002,  rained down tons of debris for hundreds of miles,  showing just exactly how ridiculous that oft-repeated claim is. 

And this risk has been known for decades!  John Glenn’s Mercury capsule was sent to orbit by an Atlas booster that was essentially a lightweight stainless steel balloon,  relying on some inflation pressure just to hold its shape.   That shell broke up during entry,  yes,  but a piece of the internal propellant piping washed up on an African beach only a few years later.  This piece of debris was identified by the serial number stamped on it,  it was in that good a shape!    This was 6 decades ago that “they” knew this could happen!

There’s a lot of debris up there in orbit that sooner or later we will have to contrive a means to go get,  for disposal.  I think everybody understands that.  But when you find yourself in a deep hole,  the first thing to do is stop digging!  We do not need to be launching more things into orbit that inherently become debris that will collide (creating more debris) or fall back.

We need to modify the international space treaty to preclude launching satellites that have no means to de-orbit themselves in a controlled fashion over the remotest part of the Pacific.  We need to preclude the jettisoning of anything at all,  not even paint flecks,  once orbital-class speeds have been achieved.  We need to very strongly discourage fielding any future launch and space vehicles that are not fully reusable,  or that do not offer safe stage disposal capability. 

That’s the real lesson here,  and it has been staring us in the face for many years now,  unaddressed!  Will it take deaths on the ground from falling debris to prompt addressing it?  How negligent is that?

Photo of one piece of Kosmos 954 debris,  in the Canadian Arctic

Vehicle Assembly and Refueling Facility in LEO

Described herein is a concept (only) for a facility in low Earth orbit for the assembly and fueling of interplanetary vehicles requiring hyperbolic departure (and arrival),  in particular those associated with space-tug assisted departures and arrivals.  Such a facility need not be a 1-to-2-decade long international project to build,  if it is docked together out of modules that fit within the payload spaces of the current launcher fleet!  That should be easily achievable for a “clean sheet of paper” design like this!

For lunar missions,  the departure from LEO is not hyperbolic,  although it is elliptic at very-near-escape perigee speeds!  Depending upon the choice of the extended departure (and arrival) ellipse,  the LEO departure velocity requirement for a lunar mission can be reduced to near-zero,  with the space tug assuming most or all of that velocity requirement just getting the craft onto the ellipse. 

No calculations have been made,  these results are concept only,  as is perfectly reasonable at this early stage!  The basic design concept has two core sections,  one made of pressurized modules docked together,  and the other a truss core to which a multitude of propellant tanks are attached. 

Attached to one end is the Power and Propulsion Section,  where solar electricity is made,  stored,  and distributed.   This section includes propulsion sufficient to address the needs for countering orbital decay,  conducting debris avoidance,  and performing end-of-life safe disposal. 

The pressurized-core section is the Vehicle Assembly and Refueling Section,  where interplanetary vehicles are assembled from modules,  mated to space tug vehicles as appropriate,  and fueled-up from the propellant depot section for the relevant missions.  Many remote-operated arms similar to those used at the International Space Station (ISS),  and previously on the old Space Shuttle,  are installed to make vehicle assembly and handling operations as safe and easy,  as is possible.  This is a manned microgravity facility,  probably manned by rotating crews,  as is the ISS.

The truss core section has multiple propellant tanks attached to it,  with the propellant feed lines and electric power lines housed inside the truss.  This is the Propellant Depot Section,  presumed to be kept supplied by unspecified tanker flights up from Earth.  It would have both cryogenics and storables,  to supply a variety of on-orbit needs.  Its capacity is also easily expandable. 

The concept for the Vehicle Assembly and Fueling Section is sketched in Figure 1.  The concept for the Power and Propulsion Section is sketched in Figure 2.  The concept for the Propellant Depot Section is sketched in Figure 3.  All figures are at the end of this article.

This kind of a facility would be easiest to keep supplied,  if located in a low-inclination eastward Earth orbit.  That presumes vehicle modules,  propellants,  and supplies are shipped up from the surface.  It would clearly be useful in any event,  but it is an essential enabling item for making use of reusable space tugs for elliptic departure and arrivals,  as described elsewhere in Reference 1. 

Vehicle Assembly and Fueling Section

As the sketches in the first figure indicate,  this facility is built up from many cylindrical modules docked together,  and each is to be small enough to fit in the payload spaces of the existing launcher fleet.  Some of these are oriented along the section axis,  and the others are perpendicular to it,  but all are in one plane.  These could be either hard-shell modules,  or inflatables with hard structural cores,  or a mix of both types.  That choice remains unspecified,  at this time.

The modules along the core axis provide much crew living space,  lots of storage space for life support and other supplies,  airlocks for space-walk activities,  plus any equipment for Earth observations (potentially replacing those functions after the ISS is decommissioned).  These modules would be equipped with external cradle mounts,  to help hold the vehicles being assembled,  thus freeing up the arms for other tasks that are part of the assembly process.  Some of the hatches should be closed,  when the modules are not in use by the crew. 

The modules perpendicular to the core provide the spaces for the arm operators to work.  The arms are affixed to the module ends.  These modules need large windows,  by which the arm operators can see their workpieces in order to work.  Assembly work areas are disposed along this section,  on two opposite sides.  It should be able to handle a busy traffic load,  if arranged in this way.

Per Reference 2,  I am suggesting that this section’s internal atmosphere follow the “Rule of 43”,  that being a two-gas oxygen-nitrogen system,  at 43 volume percent oxygen,  and 43% of a standard atmosphere total pressure.   This is very close to the best atmosphere that I found (which was 43% oxygen,  43.5% of an atmosphere total pressure),  and it is easier to remember!  It has the same oxygen concentration (as mass per unit volume) as sea level Earthly air at 70 F,  so the “predicted fire burn rate danger” from the usual Arrhenius overall-chemical rate equation,  is no worse than that down here on Earth,  at sea level on a warm day. 

Further,  the “pre-breathe criterion” allows no pre-breathe requirement be imposed for donning pure-oxygen space suits,  of helmet pressures down to as low as only 3.002 psia (155.2 mm Hg)!  That criterion says the ratio of nitrogen partial pressure to suit oxygen helmet pressure,  may not exceed 1.2, in order to avoid the nitrogen blow-off time otherwise required.  (The absolute minimum tolerable suit pressure for functional cognitive capability is 2.675 psia (138.3 mm Hg),  before applying a 10% leak-down factor.  The cognition margin is very slightly negative once leaked down.) 

As a further bonus,  the proposed oxygen partial pressure is the same as that at about 2500 m altitude,  so there should be no long-term hypoxia risks,  or even any reproductive health risks for female crew,  based on centuries of human experiences living up to that altitude,  but not above it.

Power and Propulsion Section

Most likely,  the “best” propulsion choice for this application is a hypergolic storable bi-propellant system,  pressure-fed for the greatest engine simplicity and reliability.  Tanks would be bladdered,  with inert gas (helium) expulsion at effectively the feed pressure to the engines.  Propellants would likely be nitrogen tetroxide (NTO) oxidizer and monomethyl hydrazine (MMH) fuel,  although the other hydrazines could also serve,  which include plain hydrazine,  unsymmetrical dimethyl hydrazine (UDMH),  and Aerozine-50 (a 50-50 blend of plain hydrazine and UDMH).  These tanks would need a thin layer of insulation topped with a very reflective aluminum foil,  plus electric tank heaters to prevent freezing while shadowed.

There is a core module to this section that connects to the rest of the station on one end,  and the engines and their propellant tanks on the other.  It would have multiple “fins” mounted to the sides,  some being waste heat radiators,  the others being solar photovoltaic panels.  There would be controls,  batteries,  and distribution switching equipment inside,  plus a docking module for capsules bringing crew and supplies.  This core module is pressurized for easy access,  but the hatch into it should be closed,  when crew are not working in there.

Propellant Depot Section

This section has a modular truss core containing the multiple types of propellant feed lines,  and the necessary power lines.  The propellant tanks are mounted to its periphery,  as sketched in the third figure.  There are basically two types of propellant tanks,  those equipped to store and deliver cryogenics,  and those equipped to store and deliver storables.  Each propellant species must have its own line fittings,  not interchangeable,  so as to prevent incorrect hookups (which would most likely be disastrous).   There are no pressurized modules in this section. 

For the storables (which includes rocket-grade kerosene RP-1),  the bladder in the tank provides the means to transfer propellant,  driven by inert gas pressure that everts the bladder,  as indicated in the third figure.  These tanks will also need some insulation topped by reflective foil,  and some in-tank heaters,  much like the tanks on the Power and Propulsion Section.  The difference is that the inert gas pressure can be lower,  just enough to drive the transfer,  and not at all far above the level to prevent “hot room temperature” boiloff.

The cryogenics are different,  in that there are no feasible bladder materials that could survive eversion at cryogenic temperatures.  These have to be metal tanks with no bladders,  although they do need a layer of insulation topped by reflective aluminum foil,  plus cryocooler equipment. 

In zero gee,  the propellant will initially be free-floating globules,  eventually settling into a thick film coating the entire inner surface of the tank with a vapor void up the core,  but with no pressure other than enough inert gas pressure to stop boiloff.  The slightest touch causes the thick film to break up into free-floating globules again.  Up to now,  the only way to control this behavior into a stable pool from which a pump can draw suction,  was to use thrusters to accelerate the vehicle.  You can’t do that with tanks on a space station whose orbit you do not want to change.

I had previously come up with the spinning tank concept to fling the propellant to the outer wall by centrifugal force.  From there,  a pump could draw suction from openings along the tank sides instead of one end.  This was conceptualized as the vehicle docking with the tank,  in turn undocked from the station.  The docked vehicle and tank would move away to a safe distance and then spin-up in “rifle-bullet” mode,  to fling tank contents to the outer walls.  Then pumped transfer could take place,  followed by de-spin,  then redocking the tank with the station,  and finally undocking the vehicle from the station’s tank.  While this would work,  it does involve multiple docking operations,  and spin-up/de-spin of some massive objects.  But it was better than trying to store spinning tanks on the station.  This concept was described in Reference 3. 

I have since revised the concept to just spinning the propellant inside the stationary tank,  by means of moving vanes inside the tank.  The suction pickups remain on the outer periphery.  If you use a pair of counter-rotating vane sets inside the tank,  separated by a perforated baffle,  you can avoid gyroscopic forces being applied to the station. This concept is shown in the third figure. 

There are no dock/undock operations associated with a propellant transfer by this means.  The vanes can be spun by a coaxial counter-rotating shaft assembly,  entering one end of the tank through a gland seal,  with the drive motor left accessible for repairs and replacements.  You just spin up for the transfer.  Otherwise,  nothing moves.  This is also the least mass to spin up,  reducing the energy requirements for spin-up/de-spin,  and eliminating any and all thruster operations. 

I put the oxygen (LOX) tanks closest to the Vehicle Assembly and Fueling Section,  because that is the largest species volume being used,  and that shorter length minimizes the power line losses for the motors powering the liquid spin.  As the third figure shows,  I put the cryogenic fuels hydrogen (LH2) and methane (LCH4) adjacent to the oxygen,  because their volumes are also large,  to reduce transmission line losses a bit further.  I separated the NTO from the MMH with the storable RP1,  in order to minimize the possibility of spilled hypergolics coming into contact,  even in vacuum.  That is a crucial safety consideration!

The truss can be extended further,  with additional tanks installed,  either for other propellant species,  or for additional capacity,  or both.  This is because there is no other section to the station beyond the Propellant Depot Section.

I think this “spin the propellant inside stationary tanks” concept may be easier to develop and implement than the alternative “each tank is its own syringe” concept,  because (1) the rotating-shaft gland seal technology already exists,  even for cryogenics,  (2) the required piston seal concepts and associated leakage recovery concepts for the “syringe” do not yet exist for cryogenic fluids,  and (3) the tank-and-equipment masses and dimensions would be lower:  vanes and motor vs a syringe piston and its driving equipment.  The hardware has to ride up to LEO inside existing payload spaces,  after all!

Conclusions

#1.  A combined vehicle assembly facility and propellant depot in LEO could enable all sorts of interplanetary missions very effectively,  and even missions to lunar orbit,  plus replace the Earth-observation functions that will likely cease for a while when the ISS is decommissioned. 

#2.  This type of LEO facility is an enabling item to put an effective space tug operation into effect,  that uses elliptic departures and elliptic arrivals,  to reduce the velocity requirements of interplanetary (and lunar) vehicles.

#3.  This kind of fueling operation could use “spin-the-fluid-in-a-stationary-tank” to reduce the overall energy requirements of propellant transfer,  eliminate any need for the use of ullage thrusters,  and also eliminate many dock/undock operations.

#4.  All the other technologies required to build this thing already exist. 

References (use date and title in the archive tool on the left,  to access quickly):

#1.  G. W. Johnson,  “Tug-Assisted Arrivals and Departures”,  posted to “exrocketman” 1 December 2024. 

#2.  G. W. Johnson,  “Refining Proposed Suit and Habitat Atmospheres”,  posted to “exrocketman” 2 January 2022.

#3.  G. W. Johnson,  “A Concept for an On-Orbit Propellant Depot”,  posted to “exrocketman” 1 February 2022.

Figures:

Figure 1 – Concept Sketches For the Vehicle Assembly and Fueling Section

Figure 2 – Concept Sketches For the Power and Propulsion Section

Figure 3 – Concept Sketches For the Propellant Depot Section

Update 5-4-2025: 

Conversations with a friend led me to understand that what I have in mind for the vane-equipped tank may not be readily apparent to the reader.  Please see the sketch in Figure A below,  as you read the following more detailed descriptions.

There are just two sets of vanes inside the tank,  mounted on shafting that causes them to counter-rotate.  Their tips spin circumferentially,  but in opposite directions (which avoids applying gyroscopic forces to the depot station).  There is a perforated baffle between the two sets of vanes so that the two volumes of fluid which are affected by the vanes,  also rotate circumferentially,  independently in each section. 

Yet the baffle is perforated,  so that the radially-measured levels of the fluid,  flung out to the tank wall,  are equal in the two sections.  It is one shaft,  with a gland seal at one tank head,  and an internally-mounted  bearing at the other.  There is a gear box near the middle that makes the shafting turn in opposite directions in the two sections.  There are probably 4+ vanes in each section,  mounted to the shafts.  If you forgo “instant” response,  these vane and shaft assemblies can be fairly lightweight construction.

The propellant pickup is along one side of the tank,  not one or the other end head,  since the centrifugal forces will fling the propellant to the outer cylindrical wall,  forming a big hollow cylindrical "form" in each of the two sections,  as wetted to the local outer wall.  These propellants are moving in opposite directions circumferentially in the two sections,  induced to do so by the spinning vanes.  But that circumferential motion does not really affect the suction drains along the tank cylindrical wall! 

You spin the vanes to withdraw propellants,  but you need no spin to pump propellant into the tank.  I put the drive motor outside the propellant tank for its safety (remembering the in-tank stirring-fan device that caused the explosion on Apollo-13),  and for easy maintenance and repair.  Cryogenic gland seal technology already exists,  in rocket engine turbopumps.  The vane shaft motor and the propellant withdrawal line are on the end that attaches to the core structure of the orbital propellant depot space station.  All the power lines and fluid delivery piping is inside that core.

This is a heavier solution than ullage thrusters,  so this is definitely only for a propellant depot in orbit (where you do not want to disturb the orbit with ullage thrust),  not the vehicles it is supposed to supply with propellants on orbit. 

However,  per the not-to-scale concept sketch in Figure B below,  it might be "just the thing" for the "payload" propellant tanks of a dedicated tanker vehicle sent up to supply this depot station.  Those will be rather small compared to the rest of the upper stage delivery craft,  in turn small compared to its launch booster.  The sketch is not to scale,  in order to provide clarity about which tanks are vane-equipped,  and which are not.  Ultimately,  this tanker needs to be a fully-recoverable vehicle. 

Figure A – Concept Details for Cryogenic Vane-Ullage Propellant Tank

Figure B – Concept Sketch for Dedicated Tanker Vehicle 

Update 5-27-2025:

I extended my investigations into some preliminary design analysis to determine some “typical” design characteristics for spinning-vane tanks of the counter-rotating type.  I ran my numbers in metric,  since that is what most space industry people are now using.

It is customary to use rotation speed measured in revolutions per minute,  rpm.  The conversion to or from radians per second looks like this:

               ω, rad/s = (N, rpm)*(2*pi rad/rev)/(60 sec/min)

or N, rpm = (ω, rad/s)*(60 sec/min)/(2*pi rad/rev)

The radial acceleration component “a” felt at the radius tip for a rotation speed ω is:

               a, m/s² = (R, m)*(ω, rad/s)²  or ω, rad/s = [(R, m)/(a, m/s²)]^0.5

You divide that “a” by the standard value of g = 9.80667 m/s² to express that acceleration in “standard gees”,  as n = a/g,  which is often also customary,  and dimensionless.  

The distance s that something falls through,  under constant acceleration a,  depends upon the square of the fall time.  Radial acceleration is not constant,  but we will ignore that:

               s = 0.5*a*t²

The floating spherical globules are everywhere throughout the tank cross section,  so the average distance through which a globule must fall is R/2.  Substituting that into the previous equation and solving for a fall time,  we have:

               t = (R/a)^0.5

which is a sort of time constant t_const for the process of all the globules accelerating outward along the radius.  (Note that for axial “ullage” acceleration,  you would use the tank length L instead of its radius R for a measure of the average fall length s = L/2 in the same equation for time constant.)

The process is quite stochastic,  but the usual “rule of thumb” is to wait 3 time constants,  and then the process is pretty much completed.   Thus:

               t_settle  ~ 3*t_const

Figure C shows N, rpm versus n, gees,  parametric upon values of R from 1 to 5 meters.  There is clearly a wide range of possible values.  The corresponding settling time estimates versus n, gees,  parametric upon R are given in Figure D just below. 

Figure C – Results for N, rpm,  Versus n, gees,  Parametric Upon R, m

Figure D – Results for t_settle, sec,  Versus n,  gees,  Parametric Upon R, m

Amazingly enough,  those t_settle values actually formed a tight band of solutions across a fairly wide range of R from 1 to 5 meters!  If one selects n = 0.1 gees,  the settling times all fall 3 < t_settle < 7 sec!  So,  the design problem is rather conveniently bounded at about n = 0.1 applied rotational gees,  with any conceivable settling times under about 10 sec!

Applying that revelation,  I plotted the necessary rotation rates N, rpm,  versus the tank radii R, m,  for only 0.1 radial gee.  Those data are given in Figure E,  and indicate a bound on the rotation rate as 4 < N < 10 rpm,  for all radii from 1 to 5 meters!  That rather conveniently bounds the rotation rates to rather low values.  Tip speeds are also closely bounded as about 1 to just over 2 m/s,  also low numbers. 

Bear in mind that if you wait about 10 sec,  you have all the settling times covered!  That is a rather short settling time!  The smaller value of 3 sec occurs at the smaller R = 1 m,  so yet smaller tanks are no problem at all.  At this time in history,  it would be difficult to imagine successfully transporting to orbit a tank much larger than 10 m in diameter,  so we have that end of things fairly well covered,  also!  And the highest tip speed is less than twice the max flow speed recommended for liquids in pipes.  We should be okay there!

Figure E – Required Rotation Rates vs Radius at 0.1 Gee

This Figure E and a nominal settling time of 10 seconds pretty well has most conceivable tank sizes “covered” for designing-in counter-rotating vanes.  Such would require no dock and undock operations to transfer the propellants,  and would apply no unwanted forces due to spin reactions or gyroscopic resistance forces to whatever structure or vehicle such a tank is mounted upon (precisely because there are counter-rotating sets of vanes).  The pump suction points are on the tank lateral wall instead of the ends.  So what?  The tank itself does NOT spin!  So,  there is no balance problem,  other than the vanes themselves,  when you build one of these tanks.  You just spin up the vanes,  wait about 10 seconds,  then start your transfer pump.  How simple is that?

Again,  such would enable cryogenic propellant storage and transfers from an orbiting propellant depot station,  to any vehicle departing from there.  Such could also be the “delivered payload” tanks of a dedicated supply tanker vehicle,  arriving at that same station.  The implications for making deep space missions cheaper with reusability,  and cheaper still by means of space-tug-assisted elliptic departure,  are simply staggering!