Understanding Your Tires

There are basically four types of tires seen on passenger cars and light trucks (pickup trucks).  These are the P-metric and ISO-metric tires most often seen on passenger cars,  and the LT-metric and “flotation” (not metric) tires seen on light trucks.  In some cases,  light trucks come factory-equipped with P-metric or ISO-metric tires,  but you do not see light truck tires as factory equipment on passenger cars.

P-metric is a US Tire and Rim Association (TRA) designation system with tire section width specified in metric millimeters,  but rim size specified in US customary inches.  Section height is given as a percentage to be applied to section width.  It will have a “P-“ in front of the numbers that specify sizes.  This size code is molded into the tire sidewall.  There is a specific set of load-inflation tables from the US TRA that go with these tires (and no others).

ISO metric uses exactly the same numbers to specify size,  but lacks the “P-“ in front of the numbers that are molded into the sidewall of the tire.  Section width is given in millimeters,  and rim size in inches.  Section height is given as a percentage to be applied to section width.  There is a different set of load-inflation tables to use with these tires,  from the European Tyre and Rim Technical Organization (ETRTO).

LT-metric refers to a US TRA class of light truck tires,  using the same metric section width,  section height percentage,  and rim size numbers,  as the P-metric and ISO metric tires.  Those numbers are preceded by “LT-“.  These LT-metric tires have their own set of load-inflation tables from the US TRA.

The “flotation” sizes are the final form of the old US customary inch-size designations.  These are inch measurements for overall diameter,  section width,  and rim diameter.  For the light truck application,  this size designation is followed by the letters “LT”,  as well as another letter designating the load range of the tire. These have their own load-inflation tables from the US TRA.

You must use the correct load-inflation table for the type of tires installed on your car.  These tables are downloadable off the internet.  See the section Load Inflation Tables below.

What Is On the Sidewall

Using the spare for one of my own passenger cars as the example,  here is how to read the pertinent information off the sidewalls of the tire.  The example is an ISO metric tire manufactured by Firestone at a factory in Brazil.  The basic tire size and application information is shown in Figure 1.  The same information is molded into both sidewalls (inner and outer).  Right under the brand name logo,  the code shown reads “175/65R14 82S M+S”.  There is no “P” and no “LT”,  so you know it is ISO-metric.

The tire section width is 175 mm from inner to outer sidewall (not the tread width,  but from bulge to bulge of the sidewalls).  The ratio of section height to section width is 65%,  meaning the section height is 0.65 * 175 mm = 113.75 ~ 114 mm.  Section height measures from where the bead seats down inside the rim edges,  out to the outer tire diameter.  The “R” indicates radial construction.  A “D” or a “B” indicates the now much-rarer bias-ply construction.  The rim diameter is 14 inches,  which is also measured down inside the rim edges,  where the tire bead seats. 

The “82S” tells you the service the tire is meant for.  The load index is 82;  higher index is heavier load capability,  but this varies from size to size,  so you have to use the load-inflation tables.  The speed rating is “S” (112 mph).  The “M+S” is “motor plus sport”,  which is advertising hype,  not really useful.

Figure 1 – Basic Tire Type and Size Information

Somewhere on the sidewalls will be a block of information that gives you the max load and max inflation values the tire is rated for.  Values are given in both metric and US customary units for both items,  as shown in Figure 2.  For this example,  the max load the tire can carry is given as 475 kg = 1047 lb,  and the max inflation is given as 300 KPa = 44 psi.  The max inflation would be “gauge” pressure above local atmospheric,  not absolute pressure.  Max inflation is driven by how the tire is constructed,  not necessarily by the max load it carries in the rating tests.   More below about that.

It is crucial to understand that these max load and max inflation pressure ratings do not necessarily go together (although they can),  nor are they the recommended inflations for any given car.  But,  combined with the data in the appropriate load-inflation table,  together they give you a very clear picture of what loads the tire can safely carry,  and what pressures are required to achieve that capability. If the tires are stock size for the car,  just use the inflation pressures listed on the car’s placard.  If not,  you must adjust inflations using either the max axle loads and the load-inflation table for the replacement tires,  or the load-inflation tables for both the stock and the replacement tires.

Somewhere else on the sidewalls will be molded the relative ratings for treadwear,  traction,  and temperature.  These are shown in Figures 3,  4,  and 5 for this example,  as treadwear “400” (Fig. 3),  traction “A” (Fig. 4),  and temperature “B” (Fig. 5).  These are less informative than often believed.

The treadwear rating is relative to what a cheap tire might provide under the same loading and service conditions.  Values seen are “100” (the cheap-tire reference),  “200”,  “300”,  and “400”.  The higher values are supposed to provide more miles of tread life before they are worn out.  However,  the “400” does NOT last 4 times longer than the “100”;  it only lasts a little longer,  most of the time!  The changes in tire composition (usually extra carbon in the rubber) that confer longer tread life also act to lower traction and perhaps temperature ratings. The higher the carbon loading,  the harder the rubber.

Traction ratings are “A”,  “B”,  and “C”,  with “A” representing the best.  I’ve never seen a “C” traction tire,  and I cannot tell much difference between an “A”-rated tire and a “B”-rated tire.   I don’t see very many “B”-rated tires,  anyway.  Harder tires at higher carbon loading break free and skid easier.

Temperature ratings are also “A”,  “B”,  and “C”.  “A” is the best,  but I have never actually seen anything but a “B” rating ( I do not use retreads).  Tires run hotter under heavy load,  especially in hot weather.  If they get too hot,  the risks of tread separation and blowout rise greatly!  Retreads really suffer from this,  as the vulcanization temperature for the bond joint of the new tread cap onto the old tire,  is necessarily lower than the vulcanization temperature for the old tire carcass.  Otherwise,  the tire would fail during the retread operation.  It is an ugly little fact of life that rubber heated above its vulcanization temperature re-liquifies.

The other thing you really need to know is how old the tire is.  That is because tire rubber degrades over long periods of time,  leading to the tire blowing out,  or otherwise coming apart catastrophically.  A lot of people call this “dry rot”,  but it is really the action over time of ultraviolet light,  plus ozone and other chemicals in the air,  degrading the rubber. 

Somewhere on the outer or inner sidewall,  but not necessarily both,  is a DOT code that will tell you when the tire was manufactured.  For the example,  I first looked at the outer sidewall and found “DOT E2EX 38B” plus a blank oval where the date code should be.  That is shown in Figure 6.  Then I looked at the inner sidewall and found “DOT E2EX 38B 3110”.  The date code is the “3110”. That is Figure 7.  

Figure 2 – Max Load and Inflation Ratings

Figure 3 – Treadwear Rating (“400” Shown)

Figure 4 --  Traction Rating (“A” Shown)

Figure 5 – Temperature Rating (“B” Shown)

Figure 6 – DOT Code Date Is Missing On Outer Sidewall (Empty Third Oval)

Figure 7 – DOT Code Date Is Present On Inner Sidewall Third Oval (Date Code 3110)

This 3110 date code means the tire was manufactured in the 31^st week of calendar year 2010.  This is currently late 2021,  so this tire was manufactured 11 years ago,  and has been in storage waiting to be sold,  ever since then.  As long as the storage was relatively cool,  and especially dark,  the long storage time should not matter that much.  But there is no avoiding the exposure to ozone in the air.

Unfortunately,  there are no hard-and-fast rules for how old a tire can be.  A sort-of general rule of thumb is that it should not exceed 6 to 10 years old,  in service on the car.  Storage doesn’t count much against that,  except for the ozone damage,  as long as it was stored inside and dark.  Myself,  if I haven’t worn this tire out in 5 to 6 years,  I will consider replacing it as “unreliable in service” due to age.

Tire Speed Ratings

The published speed range ratings look like the following table.  As a general rule,  do not exceed the speed rating for the tires you have,  even for a short transient.  If the weather is hot or the load is high,  stay well below the rated top speed.  What happens is that the tire rapidly gets too hot flexing as it rolls,  while simultaneously being stressed harshly by centrifugal forces.  This effect gets greatly exaggerated at high loads or in hotter weather,  and failure can happen in minutes,  or even seconds. 

TIRE SPEED RATINGS TABLE

Tire Speed Ratings  from https://www.readingbody.com/understanding-truck-tires-load-ratings-and-sizes/ as of 8-25-2021

·        L: Only apply these tires to off-road trucks that will not exceed 75 mph.

·        M: Use with temporary spare tires at no faster than 81 mph.

·        N: These tires have a maximum speed of 87 mph.

·        P: Tires with a P rating, cannot go faster than 93 mph.

·        Q: Q tires are usually winter studded or studless tires and should not exceed 99 mph.

·        R: For heavy-duty LT trucks, the rating may be R, which indicates a speed limit of 106 mph.

·        S: Family vans and sedans use the rating of S to indicate speed maximums of 112 mph.

·        T: Family sedans and vans may also use T-rated tires, which can drive up to 116 mph.

·        U: U tires can reach 124 mph.

·        H: Sports vehicles with H speed ratings can hit 130 mph.

·        V: Sports cars, sedans and coupes often use V-rated tires, which have speed ratings up to 149 mph.

·        W: Exotic sports cars use tires that can reach speeds up to 168 mph and have a W designation.

·        Y: The fastest speed rating — once Z which indicates faster than 149 mph — now is Y, which allows the tires to reach 186 mph.

For the example,  the speed rating is “S”,  corresponding to 112 mph on a passenger car.  That particular car (a 1998 Nissan Sentra) will not go that fast on level ground anyway,  so this isn’t much of an issue.  It won’t even go that fast downhill,  under most circumstances.  It’s a little 1.6-liter 4-cylinder!

Load-Inflation Tables

I got my copy of the four load-inflation tables as one document from the Toyo tire website:  https://www.toyotires.com/tires-101/tire-load-and-inflation-tables

On that website,  there is a link to the stored tables,  which can be downloaded as one single file in pdf format.  That link looks like:  Load & Inflation Table Application Guide

I recommend that you visit the indicated site,  follow the indicated link,  and download the pdf document that contains the four load-inflation tables all in one place.  That file also contains instructions for exactly how to use them.  These four tables cover P-metric,  ISO metric,  LT-metric,  and “flotation” tire types. 

There is an oddity to be aware of,  for dealing with LT-metric light truck tires.  The load index is often two numbers separated by a slash,  not just one.  The higher number pertains when there is a single tire and rim on the end of the axle.  The lower number pertains when there are two tires on two rims on the end of the axle.  The lower load index number represents a lower max load to be carried by each tire. 

The reasoning behind this is what the remaining tire can carry,  if one of the two on the end of the axle deflates.  The remaining inflated tire has to carry the load of the pair,  until the event is detected and the vehicle can be stopped for repair.  It can carry some overload,  but not a full factor 2 overload,  for a short time.  So,  the load index rating is reduced for that dual installation and deflation scenario.

There is another oddity to be aware of,  if P-metric passenger tires are fitted to a light truck.  Light truck-rated tires (the LT-metric,  and “floatation” with “LT” in the size) are typically built of tougher construction,  to withstand more routine abuse and more destructive driving conditions.  P-metric passenger car tires are just not built to withstand that kind of abuse.  While ISO-metric tires are generally a little tougher than P-metric tires of the same size,  they also still fall short of truck service. 

That is why the US Federal Motor Vehicle Safety Standards (FMVSS) demand that the allowable load ratings at any given inflation value be reduced by a factor of 1.10,  if a P-metric tire is to be fitted to a light truck.  If the factory tire on a light truck is a P-metric tire,  this factor 1.10 reduction has already been applied at the factory.  This load rating reduction of the ISO-metric tires is not so required,  but something like that would be highly recommended. 

Resizing Loads and Inflation for the 1998 Nissan Sentra

This is an odd case,  as the stock load margins are very low,  and this car has a history of hot-weather tire blowouts.  P-metric tires of this size (P-175/65R14 load index 81) are no longer so common;  instead the slightly-higher load index ISO metric tires (175/65R14,  load index 82) are now more common. 

The tire inflation placard for this vehicle (for the P175/65R14 size) lists 33 psi front,  29 psi rear for inflation.  The placard weight ratings are GAWR (gross axle weight rating) 1872 lb front (where the engine is),  and 1567 lb rear,  with a gross vehicle weight rating (GVWR) of 3413 lb,  which is always a little less than the sum of the front and rear axle ratings. 

Half the axle ratings are 936 lb front,  and 783.5 lb rear,  which the tires must bear during straight constant-speed driving on level ground.  At the placard inflations,  the tire load capabilities minus the axle rating loads (load margins) are rather small numbers: only about 58 lb front and 153.5 lb rear.  The plot is in Figure 8.  Note that the max load capability of 1019 lb is at the max inflation 35 psig.  

Increasing the rear inflation level to 30 psig raises that load margin to about 168.2 lb.  Increasing the front inflation to 34 psig raises the front load margin to about 74.7 lb.  These slightly higher load margins should help reduce the blowouts,  while still maintaining a handling difference of 4 psi,  same as stock.

Figure 8 – Tire Loads and Capabilities for P-Metric Tires on Nissan

The ISO-metric tires have a higher max inflation pressure (44 psig) than the pressure at max load (36 psig).  One plots this as constant load from the test data max load point,  up to the max inflation pressure point,  as shown in Figure 9.  If we choose 36 psig front and 32 psig rear,  we have larger load margins of 111 lb front and 164.5 lb rear,  at a front-to-rear handling differential of 4 psi,  same as stock.  

Figure 9 – Tire Loads and Capabilities for ISO Metric Tires on Nissan

Accordingly,  I am recommending revised tire inflation levels of 34 psi front and 30 psi rear,  vs the factory placard levels of 33 front and 29 rear,  whenever P-metric tires are used.  I also recommend the slightly-higher-still levels of 36 psi front and 32 psi rear whenever ISO-metric tires are installed.  There is no change to the 60 psi inflation for the “doughnut” spare. 

What this recommendation does is provide tire load capacities equaling or exceeding factory stock levels,  while preserving the front-to-rear inflation differentials.  That outcome is in accord with the guidelines for using the load-inflation tables.  The difference is that my procedure gets you the actual load margins for both the original stock and the revised tire selections.  You have more information.

Resizing Loads and Inflation for a 2005 Ford Focus

This vehicle came factory stock with P195/60R15 standard load (SL) tires of load index 87.  The stock tire inflation placard recommends 32 psig inflation all around,  no differential front-to-rear.  Stock tire load margins based on the load-inflation plot of Figure 10 are 158.5 lb front and 273.5 lb rear.  Hot weather blowouts were never a problem with this car.  There is no need to change the stock tire specification. 

Figure 10 – Tire Loads and Capabilities for P-Metric Tires on Ford Focus

Those factory stock tires are now hard to find,  but the ISO-metric equivalent size is available.  Those are 195/60R15 standard load (SL) tires of load index 91 and speed rating H (130 mph).   These tires are constructed stronger,  reflected in the larger load index,  and have a max inflation of 51 psig,  versus the stock P-metric tire max inflation of 35 psig.  

One would expect higher load capacities at pretty much any pressure,  and this is borne out in the load-inflation plot of Figure 11.  Those data lead to substantially-larger load margins of 236.5 lb front and 351.5 lb rear at the same 32 psig inflation.  These tires will be “tougher” against abuse at the same inflation,  than were the factory-stock P-metric tires. 

The recommendation is keep the factory stock 32 psig inflation (front and rear),  whether the tires are P-metric or ISO-metric.  The 60 psig “doughnut” spare is no different than it was.

Figure 11 – Tire Loads and Capabilities for ISO Metric Tires on Ford Focus

Resizing Loads and Inflation for a 2010 Toyota Prius

This vehicle came factory stock with P-metric P195/65R15 standard load (SL) tires of load index 89,  placarded for inflation at 35 psi front and 33 psi rear.  A plot of the load-inflation data in Figure 12 reveals the rather substantial load margins to be 144 lb front and 176.5 lb rear.  

Figure 12 – Tire Loads and Capabilities for P-Metric Tires on Toyota Prius

The replacement tires are now ISO-metric 195/65R15 standard load (SL) tires of load index 91 and speed rating H (130 mph).  The corresponding load-inflation data plot is given as Figure 13.  These tires increase the load margins to 177 lb front and 185.5 lb rear,  at the same inflation levels. 

Figure 13 – Tire Loads and Capabilities for ISO Metric Tires on Toyota Prius

Thus,  the recommended tire inflation levels need not be revised from the placarded 35 psig front and 33 psig rear.  The 60 psig “doughnut” spare is unchanged.

Resizing Loads and Inflation for a 1995 Ford F-150

This is another very odd case.  The original factory stock P-metric tires are now unavailable for this rather old pickup truck.  These were P235/75R15 extra load (XL) tires of load index 108.  The load-inflation plot for them is given in Figure 14.  Note the application of the 1.10 derate factor leading to the orange derated curve below the blue stock rating curve.  That derate factor is per the FMVSS for using P-metric tires on a light truck.   

Figure 14 – Tire Loads and Capabilities for Factory Stock P235/75R15 XL Tires

The front load margin calculates as 406.1 lb at 35 psig inflation,  and the rear load margin as only 84.5 lb at 41 psig inflation.  Max inflation for these tires is 50 psig.  That loading would be pretty much in accord with 6 occupants in the cab and the full rated 1000 lb of cargo in the bed of the truck. 

I could not get those tires recently.  LT-metric tires were available in this size,  but only with the block tread pattern that does not wear properly with the twin I-beam suspension this truck has.  The only P-metric tires I could find were slightly lower section height,  and (more importantly) only standard load (SL)!  Those were P-235/70R15 SL tires of load index 102.  The load-inflation table data for those tires are plotted in Figure 15 as the blue curve,  and then derated by a factor of 1.10 per the FMVSS as the orange curve.  Max load for these tires is at 35 psig,  and max inflation is 44 psig. 

Figure 15 – Tire Loads and Capabilities for P235/70R15 SL Replacement Tires

With these tires,  which are currently on the truck,  the front load margin at the placard 35 psig inflation is reduced from 406.1 lb down to 206.1 lb.  Technically,  that reduction violates the tire sizing guidelines given in the load-inflation tables document,  but it is still a fairly substantial positive margin. 

The rear load margin at the placard inflation of 41 psig falls from 84.5 lb to a -176.4 lb shortfall,  and THAT is a serious problem indeed!    A small positive load margin would obtain if the rear wheel load were reduced by about 200 lb at each wheel.  That corresponds to a 400 lb reduction in the rear axle load,  in turn corresponding to a 400 lb reduction in the truck bed load. 

The reduced section height also leads to a 3.2% reduction in outer diameter,  making the speedometer reading another 2 mph high at a real 60 mph on the radar,  for that reason alone. 

I have chosen to drive the truck this way at 35 psig front,  41 psig rear (whenever loaded),  but to reduce the truck bed payload from 1000 lb to 600 lb,  and to slow down to about 50 mph whenever 600 lb is exceeded.  This is primarily because they are SL,  not XL,  tires!  But I do not have to like this situation! 

I do not know if a better tire selection is really available,  but I did identify one represented in the load-inflation tables:  P245/70R15 XL tires of load index 108.  These would have a section width 10 mm (0.4 inch) wider,  but they fit the same stock rims.  The outer diameter is much closer to stock.  See Fig. 16.

Figure 16 – Tire Loads and Capabilities for P245/75R15 XL Candidate Replacement Tires

These tires,  if available,  would more-or-less restore the former load margins.  At 35 psig,  front load margin becomes 406.1 lb (same as stock).  At 41 psig,  the rear margin becomes 94.5 lb,  very slightly better than stock.  The only risk would be rubbing something in the front wheel wells during sharp turns,  because of the wider section width. 

The availability of LT-metric tires is far better,  in the stock size.  The problem is the block tread pattern wearing improperly,  something I have already experienced!  It really is a serious problem.  Assuming I could find non-block tread patterns in an LT-metric tire,  the only question is which load range (and the corresponding inflation levels) is appropriate.  Fig. 17 is for LT235/75R15 Load Range C tires.  No derate factor is required.  The load index is 104,  lower than stock.

Figure 17 – Tire Loads and Capabilities for LT235/75R15 Load Range C Tires

These tires require different inflations to meet the load margin needs.  At 45 psig,  the front load margin is near stock at 387.5 lb,  and at 50 psig,  the rear load margin is near stock at 85 lb.  This is acceptable,  but we are running the rear tires right at their max inflation limits.   That is not such a good idea!

Similar data for LT235/75R15 Load Range D tires are given in Figure 18.  The load index is 110,  higher than stock.  At front 45 psig,  we get the same 387.5 lb load margin as the load range C tires.  At 60 psig rear,  we get a greatly-improved load margin of 335 lb.  And,  we are still under the max inflation rating of 65 psig!  These would be quite acceptable,  if the non-block tread pattern could be obtained. 

Figure 18 – Tire Loads and Capabilities for LT235/75R15 Load Range D Tires

The LT235/75R15 Load Range E tires are plotted in Figure 19.  These have load index 116 (much better than stock),  and a max inflation of 80 psig.  

Figure 19 – Tire Loads and Capabilities for LT235/75R15 Load Range E Tires

At the same 45 psig front,  load margin is the same 387.5 lb as the load range C and D tires.  At the same 60 psi rear as load range D,  the load margin is the same 335 lb as the load range D tires.  These meet requirements,  but have excess capability (and expense) that are not needed.

The recommendation here depends upon the tread patterns available in this size for LT-metric tires.  If the non-block tread pattern is available,  then LT235/75R15 XL Load Range D tires of load index 110 are greatly preferred,  to be inflated 45 psig front,  and 60 psig rear,  when loaded.  Unloaded,  one can use 45 psig rear,  and it won’t break away so easily on a wet road.

Failing the availability of the non-block tread pattern,  we would prefer the original stock P235/75R15 XL tire of load index 104,  or as a backup possibility,  could accept the P245/70R15 XL tire of load index 105,  at 35 psig front,  and 41 psig rear when loaded.  35 psig rear unloaded handles better in the rain. 

Under NO circumstances,  should a standard load tire ever again be accepted for this truck!

Final Remarks

Those of you readers who are interested in refitting with larger diameter rims and lower section height tires,  you need to follow pretty much the same the same procedure as I did. 

Here is the procedure:

Go locate a copy of the load inflation tables for the four tire classes.  Look through them to determine where the data tables for each type really are.  Get familiar with them.

Find and plot the proper load-inflation data for your tires,  just like I did.  It will be a slanted straight line up to some max load point,  then a horizontal line from that max load point,  up to the max inflation pressure (if different).  Some tires have max load at max inflation,  most do not.

If you are looking at using passenger car tires on a light truck,  always divide the tire load values from the table by 1.10,  and plot them reduced that way (don’t mess with the inflation pressures).  Use those derated load data for your analysis.  You need not do that with LT-metric or “flotation” size tires rated “LT” for light truck application.  The FMVSS demand this derating for P-metric;  I’d highly recommend it for ISO metric,  too.

Look up or otherwise find your front and rear gross axle weight ratings.  Divide those numbers by 2 to represent the max loads applied to the wheels at the ends of the axles. 

For the stock configuration at the stock tire inflations,  compute for the front and rear the tire load capability minus the wheel load applied.  Those are your stock load capability margins,  front and rear. 

For your new configuration,  do the same thing for a number of candidate inflation pressures.  You are trying to equal or exceed the stock tire load margins front and rear,  at inflation pressures in the new tire that are (1) less than its max inflation,  and (2) that differs front-to-rear by no more than a psi or so,  from the stock difference front-to-rear.  Maintaining that front-to-rear difference is driven by handling effects:  it really is important,  especially in passenger cars.      

What the Ukraine Thing Is Really All About

This is an opinion piece!

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Heard it live from the Russian ambassador’s mouth on CBS’s “Face the Nation”,  Sunday,  20 February!  The Ukraine crisis is not about the Ukraine,  it is about NATO!  They want NATO greatly-reduced in strength,  presumably to leave them freer to try rebuilding the old Soviet empire by re-annexing the breakaway territories.  

That is exactly why they demanded limits on NATO that we could not abide,  in order to “stop” the invasion.  To them,  it was worth a try to see if they could intimidate the West,  and get what they wanted without the cost of an invasion. 

This is almost no different from the way Hitler intimidated and extorted his way to start annexing parts of Europe,  which of course led to World War 2 in Europe.  The only real difference is that there were no nuclear weapons available at the start of World War 2.  (There were by its end,  and the role they played in its end is another quite-complicated story.)

Putin and the Russian oligarchs who support each other do not care about Western economic sanctions,  because no ambitious dictators ever really cared about the welfare of the people they oppress.  (I double-dog dare you to name one who did!)  But,  the real risk of revolution if things get bad enough,  is exactly why there is disinformation and false-flag activity to whip up support at home in Russia for this invasion.  Temporary though such support may be,  it will last long enough for the invasion.

With state-controlled media spewing propaganda,  this is easier to do in Russia than here.    But,  spewing that same propaganda to people in the countries of the opposition,  is a way to divide their populations and reduce their opposition,  to one extent or another.  We in the US are not immune to this nefarious activity. 

My fellow citizens,  you should be aware that there are recognized Russian state propaganda agencies broadcasting right here in the US,  masquerading as “foreign news services”,  and trying to interfere in our elections,  for several years now.  Are you familiar with Sputnik and RT (Russia Today)?  You should be!

And you should also know this:  I have lost count of how many times the infamous opinion-mongers at Fox News have quoted various outrageous claims,  that I was able to trace directly back to RT and Sputnik as the sources.  “Providing aid and comfort to the enemy” is in the official definition of treason,  or did you not know that?  That was the basis for the actual treason conviction of the US citizen who was on Japanese radio as “Tokyo Rose” during World War 2. 

As a result of this Russian focus on getting a reduction in the strength of NATO,  and the West refusing,  the invasion of the Ukraine is inevitable,  and there will be war there.  It will be lopsided,  and the Ukraine will quickly lose and be annexed into Russia,  or at least a Russian puppet placed in control.  The Western powers have decided to let this happen,  and punish Russia with economic sanctions,  not military force.  Russia’s post-Soviet economy is fragile and vulnerable,  but this strategy will take much time to have any effect that we in the West can see. 

In the longer term,  Putin may well fall to revolution,  as the Russian economy goes into complete collapse.  But he is quite likely to lash out at the West before he goes,  and that may well involve nuclear weapons.  Even without that,  the collapse of the Russian economy will cause problems in economies worldwide,  because they are all linked far closer than any economies were at the start of World War 2.  You need to be aware of that,  too.  Opposition in any form to ambitious dictators always has its price.  Often,  it is a very high price.  This one will be.

We learned during the lead-up to World War 2 that you cannot appease ambitious dictators,  you must oppose them,  no matter the price.  There is no other way.  I hope this slow-motion attempt to collapse the Russian economy is enough opposition to ward-off the start of a World War 3,  which otherwise might well start from Putin’s lashing-out at us with nuclear weapons,  when he does fall from power.  But it is only a hope!  That is how high this price might well turn out to be!

The stakes are very high.  The risks are very high.  But Putin and the oligarchs who support him,  must go!  There is no other choice.  Russia’s brief flirtation with democracy after the fall of the Soviet empire,  must resume.  

Why?  We in the West are going to need the Russians on our side to help oppose another ambitious dictator in China,  one with a whole lot more economic power behind him. 

Update 2-21-2022:  

Late breaking Monday 21 February:  Putin today begins the Russian invasion of the Ukraine,  using recognition of the Russian-backed separatists in Donbas and Luhansk as the excuse.  There is now no choice for the Western powers except to immediately maximize the economic sanctions!  The only possible goal now is to collapse the Russian economy as fast as is possible,  causing his fall by revolution at home.  It will take time.  Meanwhile,  the Ukraine will slowly cease to exist.

Update 2-24-2022:

Russia is really invading the Ukraine,  as events clearly show.  I told you so!  In the piece above!

So Putin and his government officials are proving to be the liars that I said they were in the piece above.  There is no substantive difference between the behavior of Putin and the behavior of Adolf Hitler.  You can believe nothing he says at face value,  same as was true with Hitler.  Instead,  you must parse his words against his prior words and behavior,  to try to predict what evil he will commit next.  

And,  beware of people who seem to admire him.  They are out there.  Putin has already threatened anybody who resists him militarily with nuclear weapons.  He didn't use those words,  but the meaning was quite clear!  You need no more proof of Putin's evil nature than that.  Putin's admirers would thus seem to be evil themselves.  Which is why I said beware of them.

The West must do more than simple economic sanctions;  they need to topple Putin as soon as possible.  It will take utterly-extreme sanctions,  plus cyberattacks,  plus assassination attempts to do this.  If he falls to a revolution at home,  be aware he is quite likely to lash out at the West as he falls.  I predict he will lash out with those same nuclear weapons.  Y'all have been warned!

You will note that Xi's China is not joining the sanctions against Putin's Russia,  but instead trying to subvert their effects.  Why would he do that?  Easy.  Xi needs Putin in Russia to divert the world's attention from his own ambitions of conquest. Y'all have been warned!

Next on Putin's target list are the other ex-Soviet republics,  and some of them are now members of NATO.  That means that war between Russia and NATO is now inevitable.  It's an Article 5 thing.  The inevitability of such war is precisely because Putin perceives no resistance to his conquering of the Ukraine (it was the same with Hitler).  As it says in the piece above,  Putin and his oligarch supporters in Russia do not care about the Russian people suffering as their economy collapses.  It will take time for them to turn on him.  The only remaining question is "how soon?",  because I rather doubt he can be toppled fast enough to avoid this war-with-NATO outcome.  Again,  I have warned y'all!

Update 3-7-2022:  I see no reason to change anything I have said,  especially the 2-24 update.  

Update 3-14-2022:  The beginnings of WW3 have already started,  whether any of you like it or not.  There will be nuclear weapons used before this is over.  The only real question now is how to prosecute this war without starting the massive nuclear exchange that will destroy most life on the planet. 

Prediction:  if we rely only on sanctions trying to topple Putin with a domestic revolution,  that takes time (months,  maybe a year or more).  During that time,  Putin with conquer Ukraine committing foul atrocities and genocide along the way.  Then he will invade other breakaway countries that had been part of the Soviet Union,  one after another.  He will not stop until militarily opposed.  He may not stop even then.  Same as it was with Hitler.  Thus WW3 between Russia and the West seems to be inevitable.

Observation:  something like the strike in Ukraine immediately adjacent to Poland is the opportunity to militarily oppose Putin without WW3 immediately escalating into total planetary destruction.  If he were to attack a NATO member (and he will,  Estonia Latvia and Lithuania were once Russian and are now NATO,  as is Poland,  and several more),  Article 5 triggers war as a response. Had Putin's army screwed up and actually hit Poland,  that's the excuse to push them back,  and push them out of Ukraine while we are doing it. Without that military opposition,  Putin WILL NEVER stop!  Neither did Hitler.

One more time:  whether we do anything or not,  after a while,  Putin's own people will eventually rise up and overthrow him.  As he topples,  HE WILL LASH OUT at the West!  That will be with nuclear weapons,  more likely tactical weapons used in Europe,  but there is a significant chance he might fling ICBM's at the US.  

It might be better to oppose him militarily,  earlier in this process.  That way we restrain him at least somewhat,  before he topples to that domestic revolution,  and lashes out with those nuclear weapons.  

Something to think about.  Think hard about it!

Update 3-23-2022:  I am surprised and pleased to see how stiff the Ukrainian resistance has proven to be.  As far as I am concerned,  it is no longer a certainty that Russia will conquer them.  Still likely,  but not certain.  The rest of my predictions,  including who-knows-what violence when Putin lashes out at us when he topples,  still stand.  

Update 4-13-2022:  I looked up whether napalm was still a legal weapon of war.  It is,  but its use against civilians is now considered to be a war crime!  So,  you may only use it against enemy military forces.  So be it!

The Russian military convoys strung out for miles along Ukrainian highways are a perfect target for air-dropped napalm bombs.  You just fly down the road,  pickling-off bomb after bomb after bomb. 

I suggest that the western allies make both the attack aircraft and a whole lot of napalm bombs available to the Ukrainians.  Some fighter aircraft to maintain a combat air patrol above the attack aircraft may also be necessary.  

Losses to Russian air defense will be inevitable.  So you send more of this stuff,  rather than less.

The same applies to the bombardment positions being established by Russian forces in eastern Ukraine.  Some of these are artillery,  and some are tactical bombardment missiles.  Doesn’t matter:  all would be destroyed by massive napalm attacks.  Without much civilian destruction,  if any.

This has to be done in a timely fashion,  something that seems to escape most politicians,  here and in other countries.  Time is of the essence.  Just get on with it!

The sooner Putin loses this war with massive casualties,  the sooner his people will rise up and topple him.  Is that not the ultimate objective here,  whether anyone wants to admit it or not?

Economic sanctions are taking too long.  Send the Ukrainians the napalm bombs,  and the aircraft needed to use them.

Update 4-16-22:  What the Russians are threatening the west about,  is exactly what scares them the most!  Therefore,  increase the heavy weapons sent to Ukraine,  including what I suggested in the 4-13-22 update just above,  about napalm bombs and the aircraft to carry them.  

The Russians are now worried about Finland and Sweden joining NATO,  which is why they are threatening everybody if such were to happen.  

So,  make that happen sooner,  rather than later!  It is the NATO Article 5 promise that an attack on one is an attack on all,  that scares the ever-loving piss out of Putin!  It is also EXACTLY why he doesn't want Ukraine to join NATO!  Because he knows that war with NATO leads to a defeat of Russia,  and the end of his autocratic reign.  That last is his REAL fear!  

Simple as that!  And just as messy,  if it comes to war with Russia.  I've already told you what is going to happen if/when Putin topples.  So,  how is THAT worse than any other overt war with Russia?  Quit being so f***ing timid dealing with Putin!

Think about it!  Then vote for somebody who will actually do something that makes any sense!  Few currently in office qualify,  from either party.  Party does NOT matter!  You want somebody who will actually DO something!  Period!  End of issue!

You have ALWAYS HAD TERM LIMITS!  No Constitutional amendment is necessary!

Stop voting for incumbents who won't do anything about the problems we face!  Once you know the incumbent won't do anything,  vote for his opponent.  Party doesn't matter.  Multiple terms in office leading to corruption does matter.  

You CANNOT do worse by voting for "the other guy"!  You MIGHT do better!  Keep this "throw-the-bastards-out" philosophy up,  until someone actually does what needs to be done!  Then keep him,  but only until he gets corrupted.  And he will!

Update 4-27-2022:  

Putin is now threatening to use nuclear weapons in Ukraine if "we" (The US and NATO) don't stop shipping weapons to Ukraine.  What he screams loudest about is what he fears most.  The words he uses do not matter,  it is the action:  the attempted extortion to stop the weapons shipments.  

Shipping them the really heavy stuff,  and in mass quantities,  is exactly what we need to do!  That will cause Putin's invasion to be a military failure,  and help speed his toppling by revolution at home.  (This could be over even quicker,  if we gave the Ukrainians some napalm to use on the supply convoys and the massed artillery and rocket-launcher positions.  As indicated above,  I checked on the legality of that under international law.) 

I have already predicted that Putin will lash out at the west with a few nuclear weapons as he topples.  That is inevitable.  He may also use a tactical nuke or two in Ukraine,  before his invasion fails there.  That is also almost inevitable now.  Putin has no qualms about using such weapons,  but he does have a longstanding policy of using them to prevent defeat. 

The "trick" here is distinguishing a small number of ballistic missiles from a mass attack.  That puts a razor edge on the possibility of this needless war turning into the all-out nuclear disaster we have always feared and avoided.  The cold war-era symmetrical reluctance to commit nuclear suicide no longer obtains.  And THAT is why Putin is so dangerous to us all!  This is a war warning!

As I said above,  there is no discernible difference between this situation and the beginnings of WW2 in Europe.  Putin is a ruthless clone of Adolf Hitler,  and he will not stop until opposed in force,  or until he is dead.  Learn from history,  or be destroyed by this madman's reckless actions.  

Simple as that!  And just as hard to learn as it was in 1939. 

Update 5-18-2022:  I see no reason to change the original article or any of the updates.  I see plenty of reason to change politicians serving in office who are screwing around not getting this job done,  by either impeachment or by election.  

Update 7-7-2022:  I still see no reason to change anything so far.  Only an addition:  there are two budding Hitler clones that we face,  not just Putin in Russia.  The other is in China,  and he has a far larger economy and military establishment behind him.  He is the bigger threat.

He is watching:  if Putin conquers Ukraine,  he will invade Taiwan,  which will start WW3 by bringing the US into direct conflict with China.  If Putin is unsuccessful,  he won't be so eager to invade Taiwan.  So Putin must be unsuccessful,  there is no choice here!

The parallels to WW2 are almost too close:  Putin trying to conquer territories more-or-less unopposed in Europe,  with the more massive threat China starting a war with the US in the Pacific,  with a Pearl Harbor-like attack on Taiwan.  

Once again,  you have been warned!

Ukraine needs napalm bombs and the attack planes to carry them,  to stop Putin.  Just get on with it!

A Concept for an On-Orbit Propellant Depot

Update 10-25-2022:  a version of this was presented at the 2022 Mars Society convention at ASU in Tempe,  AZ.  It was well-received.

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This article describes a concept for an on-orbit propellant depot capable of refilling visiting craft,  which presumes the visiting craft have rendezvous and docking capabilities.  This is only a concept,  which has not had any design analysis. 

Such a depot needs orbit adjustment,  reboost,  and debris avoidance propulsion capability.  There is the option to propel the depot sufficiently that it might “go where the job is”,  instead of having the visiting craft come to it,  which could assist with some aspects of orbital debris removal.  But because the facility is so large,  a separate space tug is a far better option for such missions.

Classes of Propellants

There are fundamentally two completely different classes of propellants to handle.  These are the more-or-less room-temperature storable propellants,  now most commonly used in thruster and attitude-control systems,  and there are the cryogenic “main stage” propellants,  which do in fact include the storable material kerosene.  The thruster storables need to be supplied in relatively small quantities,  while the main stage cryogens (and the kerosene) need to be handled in very large quantities.

Zero-gravity propellant ullage problems have been thoroughly discussed in Ref. 1.  The solution for the storable propellants (and the storable kerosene) is the bladdered tank.  This could be a free bladder,  a side-everted bladder,  or an axially-everted bladder.  The exact bladder geometry to be selected is not the real issue here,  in a concept design description.  Those geometries are discussed in Ref. 1.

The solution for the cryogenic propellants has been rather difficult to find.  As discussed in Ref. 1,  the historical solution for various rocket stages requiring free-fall restart has been application of ullage thrust.  The same is said in Ref. 2.  There have been some ideas tested and flown that take advantage of surface tension effects,  as discussed in Ref. 2.  Those same references point out that application of ullage thrust can be expensive in terms of ullage motor propellant quantities,  if you have to do it many times.  The solution selected for this quandary is the spinning tank technology described in Ref. 1.

The other piece of this puzzle is the facility occupancy by a crew.  There is no need to continuously-man this facility!  You only need to send up a crew when there is a propellant transfer to be made.  Once done,  the crew returns to Earth.  There are already standard docking ports of the necessary types (plural) on the International Space Station.  You just equip this facility’s crew module with those same docking ports,  plus some room for a few future new designs.

What Propellants to Have In Stock

The small-quantity thruster propellants under consideration here are the four common hydrazine variants,  and hypergolic nitrogen tetroxide (NTO) as the oxidizer for all of them.  Those hydrazine variants are plain hydrazine (C₂H₄),  monomethyl hydrazine (MMH),  unsymmetrical dimethyl hydrazine (UDMH),  and the brand-name product Aerozine-50,  (a 50-50 blend of UDMH and plain hydrazine).  These are commonly stored at significant pressure,  for pressure-fed thruster systems.

The mostly-cryogenic combinations are (storable) rocket-grade kerosene (RP-1),  cryogenic liquid methane (LCH₄,  which is not the same as liquified natural gas),  and cryogenic liquid hydrogen (LH₂),  with cryogenic liquid oxygen (LOX) as the oxidizer for all of them.  These are commonly stored at rather low pressures,  only such that boiloff is slowed or prevented.  Such engines are usually fed by turbopumps.  List follows:

Fuel                       oxidizer                application

C2H₄                     NTO                      small-quantity thrusters

MMH                    NTO                      small-quantity thrusters

UDMH                  NTO                      small-quantity thrusters

Aerozine-50          NTO                      small-quantity thrusters

RP1                       LOX                       main stage propellant

LCH₄                     LOX                       main stage propellant

LH₂                        LOX                       main stage propellant

There are two other storable oxidizers,  although neither has been used in spacecraft for some years now.  Those are inhibited red fuming nitric acid (IRFNA) and high-test hydrogen peroxide (H₂O₂).  If such should ever be demanded again,  you just add extra storable oxidizer modules to the facility for them.

Properly-Applying Spinning-Tank Technology to Solve Cryogen Ullage Problems

The “trick” is not to spin the cryogenic tanks while they are attached to the depot!  That introduces severe sealing problems and the resulting logistical problems. 

Instead,  the craft to be refueled docks to a tank,  detaches it from the depot,  and moves off some distance,  then spins up with the tank docked to the craft,  to effect the transfer tank-to-spacecraft with pumps.  Then it de-spins and returns the tank to the depot. You do this twice:  once for the fuel,  then again for oxidizer.  See Figure 1.  Vapor exchange is required along with liquid transfer,  per Ref. 1. 

Figure 1 – Spinning-Tank Technology Applied to Cryogenic Refill On-Orbit

Transfers to the depot from tanker craft work exactly the same way:  detach the empty tank to be filled,  move off and spin up the docked tank-and-spacecraft,  transfer the liquid (and vapor),  then de-spin and return the filled tank to the depot.  See again Figure 1. 

Spin-up/spin-down thruster propellants are minimized by the use of “rifle-bullet spin”,  and also very much by being limited to only the inertia of spacecraft plus tank,  not the entire depot or its entire assemblage of tanks!  It is end-to-end docking plus that “rifle-bullet spin”,  of only the tank and visiting craft,  so the moment of inertia,  and total impulse required of the spin thrusters,  is minimized.  This was well-discussed in Ref. 1.  At about 1 rpm and near 2 m radii,  the spin induces about 0.0022 gee (corrected value 2-4-22). 

That's for the cryogenic materials only.  The storables are in the same sort of bladdered tanks as the spacecraft that use them.  You just dock with the depot module and pump,  from bladdered tank to bladdered tank.  Pressurant gases are involved to push on the bladders.  There is no spin needed.

The only design requirements imposed on the craft transferring-out cryogenic liquids,  are the need for propellant suction points out on the tank periphery,  as well as on the aft domes,  plus the presence of perforated radial baffles in the tank that speed the spin-up of the liquid globules inside.  See again Ref. 1.  Craft that only receive liquids do not need periphery drains or baffles,  spin or not.

Depot Station Layout

Excepting kerosene,  the bladdered storables are primarily for attitude/maneuvering thrusters.  Those quantities are far lower,  no matter which combination you desire.  So there are hydrazine tanks for around a 1 cubic meter each of hydrazine,  MMH,  UDMH,  and Aerozine-50,  plus tanks for about 5 cubic meters of NTO.   Those are 1-ton-class quantities of each fuel material,  and a 5-ton-class quantity of NTO to support any-and-all of them. 

The storable kerosene,  and the cryogenics LOX,  LCH₄,  and LH₂ are needed in far,  far larger quantities,  being main stage propellants.  The kerosene transfers just like the other storables,  except the tanks are far larger,  around 300 cubic meters for a nominal 250 ton quantity.  The LCH₄ is near twice that volume,  and the LH₂ around 11-12 times that volume.  This assumes very large receiving craft,  and roughly-equal frequency of demand for each fuel type,  which may or may not be actually true.  The shared LOX volume to support each of these is simply huge (at around 2300 cubic meters),  that being the largest volume stored on the depot station.

See Figure 2 for some crudely-estimated quantities.  These were done in an Excel spreadsheet.

Figure 2 – Crudely-Estimated Quantities for Storables and for Cryogens

Reboost and attitude control could be a combination of the storable propellants plus electric propulsion powered by some solar panels,  all located on (or in) a “power and propulsion module”.  This power and propulsion module would be at one end of the depot station.  The crew compartment would be at the other end.  You want the NTO tanks near one end,  as physically far from the 4 types of hydrazine tanks as possible,  to avoid any possibilities of explosions-upon-contact,  if there are ever any leaks.  These materials are hypergolic,  even in vacuum.

The large kerosene bladdered tanks should probably be at the same end as the hydrazine tanks,  just closer than the hydrazines to the center of mass.  The largest and heaviest item is the LOX tankage,  which should be near center of mass.  The LH₂ tanks can be at the same end as the NTO storage,  just closer to the center of mass than the NTO.  I show the LCH₄ tanks forward of the LOX,  just to better center the LOX on the center of gravity.  Because of the toxicity of NTO residues from any spills,  the crew compartment should be far away from the NTO storage.  That puts the propulsion and power module at the NTO end of the facility.  See Figures 3,  4,  and 5.

Figure 3 – The Bladdered-Tank Storable Modules

Those modules associated with bladdered tanks need an adjacent docking adapter for the visiting spacecraft,  with the tanks situated such that there is clearance to come in and dock.  Once docked,  you just hook up the transfer lines,  and do the fluid transfer.  This would also apply to tankers refilling the facility.  There is no spin,  and the pressurant gas supplies plus the plumbing and electrical,  are within the depot module truss.  The visiting craft undocks and then redocks elsewhere,  to switch from fuel to oxidizer.  There are manipulator arms on the modules to assist with the docking operations.

Figure 4 – The Cryogenic Tank Modules

Figure 5 – Recommended Facility Layout

The cryogenics are a different situation.  These large tanks must be perpendicular to the axis of the depot facility,  and must have appropriate docking gear on both ends of the tanks.  The visiting craft docks directly to the end of the tank,  and makes the fluid and vapor connections.  Then it detaches the tank from the depot,  and moves off a short distance (for safety).  The docked vehicle-and-tank gets spun up for the fluid transfer,  then de-spun once completed.  It redocks the tank with the station,  undoes the connections,  and finally undocks from the re-docked tank. 

If both fuel and oxidizer are cryogenic,  then one repeats this procedure with the appropriate other tanks.  There are a few relocatable manipulator arms that attach to the cryogenic tank docking structures,  which assist with all the docking operations.  Not every tank needs a manipulator arm.

Preventing Incorrect Connections

If the visiting vehicle is to be refilled from the facility,  its tanks need the plumbing connections to make the indicated hook-ups.  This is pretty simple for the storables,  including the kerosene.  For the cryogens,  the visiting vehicle does not necessarily need the perforated spin baffles or periphery fluid drains that are needed in the depot tanks.  But,  any tankers attempting to refill facility tanks will need these extra plumbing features,  as was indicated in Figure 1.

Since the oxidizer quantities are nearly always larger than the fuel quantities,  I recommend making the hose/plumbing connections and fittings for oxidizers about 1.5 to 2 times physically larger than the fuel fittings.  That prevents incorrect hook-ups,  something particularly important with the hypergolic hydrazines and NTO. 

However,  there also needs to be some sort of keying feature on all of the fuel connections,  so that only the correct fittings can be coupled,  even though they are of equal size.  You do not want to mix species among the hydrazines,  or get kerosene when you wanted a hydrazine,  or vice versa. 

You also need to key the oxidizer fittings by species,  just in case IRFNA or high-test H₂O₂ ever get added to the facility.  It would be harder,  but not impossible,  to mix up NTO and LOX,  just because of the difference in bladdered versus spinning-tank technologies.  But keying the fittings absolutely stops that.

These fitting sizes and keying features are a critical safety requirement,  and should be standardized “up front”,  so that everyone is using the same equipment!

Power and Propulsion Module

This item (also shown in Figure 5) has the thrusters and the solar panels required to power the entire facility,  and to move it as needed.  Those thrust applications would include reboost for orbital decay,  deorbit at end-of-life,  debris avoidance maneuvers,  and general attitude control.  I’d recommend something similar to the Space Shuttle “OMS” and attitude-thruster systems,  which were a hydrazine variant-NTO thruster design,  plus some sort of electric thruster,  for its far-higher specific impulse,  for the reboost operations and any other orbit changes. 

My own preference for the electric thruster would be an iodine thruster,  for the easy fuel storage and handling,  even though those are not yet very common,  or even in wide use.  The bigger the electric system,  the more solar panels would be needed on this module,  and there are geometric limits to that.

Crew Habitat and Docking Module

The layout in Figure 5 also shows a crew habitation module at the other end from the power and propulsion module.  There is attached to it a multi-port docking module for crew transfer vehicles.  Crews would be required during any refilling operations for visiting vessels,  or for tankers re-supplying the facility.  Otherwise,  there is no need for crew aboard,  not even during transits to other orbits.  Crews would be aboard relatively short-term for the necessary fluid transfer operations.  Long term occupancy (like the International Space Station) is not an issue here!

Options For Spinning-Up (and De-Spinning) Cryo-Tank and Vessel

The concepts selected here do minimize the thruster propellant quantities required for spin-up and de-spin,  assuming thrusters are used for this purpose.  That is the historically-proven way to do it. 

However,  adding a flywheel for electric torque spin-up and de-spin is another viable (if undemonstrated) option.  This flywheel should probably be within the docking adapter on the end of the tank adjacent to the vessel,  so as to be nearest the docked center of gravity. 

The flywheel will need to be rather massive,  and will spin quite fast,  so that its angular momentum magnitude equals the angular momentum magnitude of the docked cryo tank and vessel.

Adding a “Go-To-The-Job” Capability Is Unattractive

If you want this depot facility to take on the role of scavenging abandoned spent stages for their propellants,  before de-orbiting them,  then you need to add very considerable extra propulsive capability to the depot station.  It would have to go and rendezvous with every target spent stage. 

You do that with very much larger fuel tanks for the electric propulsion and for the storable-powered thruster,  both located in the power and propulsion module.  That option is also shown in Figure 5,  as extra tanks to be added surrounding the power and propulsion module.  The orbital changes to do this are made unmanned,  controlled from the ground.  You send up crews temporarily,  only when propellant transfers are to be made.

Otherwise,  there is just no need for a facility propulsive capacity that large!  That is why the option takes the form of added tanks.  Everything else is the same.  Although,  choosing instead to create a specialized vehicle to operate as a “space tug” to go get the spent stage,  and transport it to the facility,  is probably the better concept,  and by far.  Such a space tug is just not that massive,  while this propellant depot facility is simply enormous.

Thrust Sizing

But in any event,  the thrust-induced accelerations need to be quite low,  in order to avoid large bending loads in the cryogen tank attachments.  Accelerations on the order of 0.01 gee or less should be fine,  with the storable thruster.  It is quite likely the electric propulsion would provide accelerations more in the ballpark of 0.0001 gee.  While very low indeed,  that’s all right:  the electric propulsion would only be used while unmanned,  to make significant orbital changes that are not time critical.  More time-critical adjustments (such as debris avoidance),  would use the storable-propellant thruster.

References

#1. “Propellant Ullage Problem and Solutions”,  Gary W. Johnson,  posted 18 August 2021 to http://exrocketman.blogspot.com. 

#2. “A Detailed Historical Review of Propellant Management Devices for Low Gravity Propellant Acquisition”,  Jason W. Hartwig,  NASA Glenn Research Center, Cleveland, OH, 44135, USA; undated AIAA paper but ca. 2015;  (pretty much the same information was also in the Hartwig Ph.D. dissertation).

For articles posted on the “exrocketman” site,  use the navigation utility left side of page.  Click on the year,  then on the month,  then if need be on the title.  

The Vaccinations Really Do Work!

These plots are data recently published in the New York Times,  complete with attributions to sources.  They are real data,  and they make liars out of those who claim the vaccinations do no good!  Look for yourself. 

Case rate data are in Figure 1.  Hospitalization rate data are in Figure 2.  Death rate data are in Figure 3.  These are recent enough that the Omicron variant dominates,  but the Delta variant is still out there. 

The attribution for Figure 1 is:  “Data is age adjusted. Recent data may be incomplete.  Sources: New York City Department of Health, Washington Department of Health”

The attribution for Figure 2 is:  “Data is age adjusted. Recent data may be incomplete. Sources: New York City Department of Health, Washington Department of Health”

The attribution for Figure 3 is:  “Data is age adjusted. Recent data may be incomplete. Sources: New York City Department of Health, Washington Department of Health”

So,  dear readers,  if your sources have been lying to you about the effectiveness of the vaccines and boosters,  then what else have they been lying about to you? 

Makes you wonder. 

Figure 1 – Case Rate Data

Figure 2 – Hospitalization Rate Data

Figure 3 – Death Rate Data

A Question For Readers

Here is a question for my readers who are particularly interested in the space travel stuff that I do.  Would you be interested in participating with others of like mind,  working on these kinds of ideas?  If so,  you might visit,  or even join,  the community that is on the New Mars forums,  part of the Mars Society’s efforts. 

That link is http://newmars.com/forums/

I am a frequent contributor there,  and we on those forums are looking for more folks interested in trying to contribute toward any possible viable ideas.  Give it a try.  Let me know here what you think,  if you go visit there.  Please use the comment option here.  I only remove obvious spam. 

GW 

Pertinent Funny

This one speaks for itself,  but is pertinent to so many things I see going on.  Enjoy.  My wife found this for me somewhere on her Facebook.  

Refining Proposed Suit and Habitat Atmospheres

Update 10-25-2022:  a version of this article and "Habitat Atmospheres and Long-Term Health" (dated 1 Jan 2022),  combined into one paper,  was presented as a paper at the 2022 Mars Society convention at ASU in Tempe,  AZ.  It was well-received.  

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I came up with the design analysis of suit and habitat atmospheres posted in Ref. 1,  and then developed a simplified and organized spreadsheet model,  to implement that design analysis procedure,  all in one convenient place.  This model uses a long-term hypoxia criterion developed from data in Ref. 2 for the habitat,  and two short-term hypoxia criteria for the minimum-pressure suit,  from pilot oxygen mask requirements.  I developed a fire danger criterion for the habitat out of oxygen concentration,  per its use in Arrhenius-type reaction-rate models. The “no pre-breathe” criterion is NASA’s,  via the USN.

The fully-compliant habitat and min-pressure suit atmosphere values of Ref. 1 are now the default case in the spreadsheet model.  This was reported in the Addendum to Ref. 1.  I have since done two further analyses,  denoted “work case 1” and “work case 2”,  as their own worksheets in the spreadsheet.

The default case at 0.45 atm and 45% oxygen (by volume) in the habitat,  produced a recommendation well in excess of the long-term hypoxia criterion,  even leaked down to 0.40 atm (some 11.111% lower). It was compliant with the fire danger criterion,  and produced a 3.031 psia pure-oxygen suit proposal that is compliant with the fully-cognitive short-term hypoxia criterion,  even if leaked down by 10% on pressure.  This is the lowest suit pressure that meets no pre-breathe.  Anything higher also requires no pre-breathe.  This is a very good combination,  but I wanted to see if I could do even better.

For “work case 1”,  I reduced the design (max) habitat pressure to 0.40 atm,  and increased the oxygen to 50%,  with a 10% pressure leak-down specified for both suit and habitat.  This still meets the long-term hypoxia criterion for the habitat,  even leaked down,  and it still meets the fire danger criterion,  by a very slightly better margin.  But it produced a min pressure suit option that failed to meet the fully-cognitive short term hypoxia criterion entirely,  and also failed to meet the bare survival hypoxia criterion when leaked down. 

I had to separately raise that suit pressure back up to 3.013 psia pure oxygen,  before it met the fully-cognitive short-term hypoxia criterion,  even leaked down.  This suit also needs no pre-breathe.  Paired with the upgraded min suit pressure,  this is also a good combination,  although it wastes some of the pre-breathe margin.  I added a separate suit upgrade calculation off to the right,  in this worksheet.

So then I ran “work case 2”.  I started getting acceptable suit pressures at about 0.43 atm habitat pressure,  and I fully met the habitat long-term hypoxia and fire danger criteria,  at just about 43.5% oxygen.  I had to hunt around a bit on both habitat pressure and oxygen percentage,  before settling on these values.  They resulted in a min suit pressure that was just a bit lower than the default case or “work case 1” at 2.975 psia,  but it still met the short-term fully-cognitive hypoxia criterion,  even when leaked down 10%.  This is the best combination I have yet found.  The separate suit upgrade calculation is also in this worksheet,  but was not needed.

The default case is Fig. 1,  which is also Fig. 9 in Ref. 1,  “work case 1” is Fig. 2,  and this best-version-yet “work case 2” is Fig. 3.  The previously most recent posting (prior to Ref. 1) about this subject is Ref. 3.

Spreadsheet Availability and Function

If you want a copy of the spreadsheet file,  please contact me by email.  As it says in the user instructions on the worksheets I created,  I recommend that you keep these example cases unchanged as templates.  Copy one of them to a fresh worksheet and do your design analysis there. 

If you copy “work case 1” or “work case 2”,  you get the suit pressure rework calculations as well,  off to the right of the main design analysis.  That is only necessary if your min suit pressure falls in a range that violates the short-term hypoxia criteria.  I did not put the revised suit calculation block on the “default case” worksheet.

If you instead want to create your own calculations,  just remember this critical point:  to get wet in-lung oxygenation,  you must first subtract-off the water vapor partial pressure to get the total partial pressure of the breathing gas inside the wet lungs.  Only after that is done do you get to apply the breathing gas volume percentages to that total partial pressure of breathing gas in the lungs. 

My calculations start with a proposed habitat atmosphere at some dry total pressure,  with a volume percentage of oxygen in it,  and also the assumption that it is a two-gas mix of just oxygen and nitrogen.  That produces the dry breathing gas partial pressures of oxygen and nitrogen. 

I reduce that total pressure by the vapor pressure of water at human body temperature to find the partial pressures of the breathing gas in the wet lungs,  and apply the volume percentages to that reduced value,  to get the partial pressures of oxygen and nitrogen in the wet lungs.  The partial pressure of oxygen in the wet lungs compares to the long-term hypoxia criterion of min 0.14 atm.

I do a molecular weight calculation to determine the mass fraction of oxygen in the mix,  which multiplies the dry breathing gas density to produce the oxygen concentration as mass per unit volume,  for comparison to the fire danger criterion of max 0.275 kg/m³,  for warm dry sea level air at 77 F = 25 C.

The partial pressure of nitrogen in the dry habitat atmosphere gets divided by the NASA/USN “no pre-breathe” factor of 1.2,  to produce the minimum pure oxygen suit pressure you can use,  and still avoid a pre-breathe time requirement.  This gets the vapor pressure of water subtracted to find the wet in-lung partial pressure of oxygen.  That gets compared to the short-term hypoxia factors:  min 0.12 atm for full cognitive capability,  and min 0.10 atm for bare survival.  (Somewhere under about 0.08 atm is the “certain death-by-hypoxia” point,  although such exposure does take significant time to injure or kill.)

It is entirely acceptable to find a habitat atmosphere at somewhat lower pressure and slightly higher oxygen than my best recommendation (“work case 2”),  that meets long-term hypoxia and fire danger criteria,  yet the resulting minimum pure oxygen suit pressure fails to meet the short-term hypoxia criteria (that is exactly that happened in my “work case 1”). 

That minimum suit pressure is just a lower bound on what you can design your suits to have.  You can always design your suits to a higher pressure than this lower bound,  to meet the hypoxia criteria.  They will always then satisfy the “no pre-breathe” criterion.  That is exactly what I did in “work case 1”,  and it is precisely why I added the suit pressure redesign block out to the right of the main calculation block.

References

#1. G. W. Johnson,  “Habitat Atmospheres and Long-Term Health”,  posted 1-1-2022 to http://exrocketman.blogspot.com

#2. Martin Enserink,  “Hypoxia City”,  a science news article published in the journal magazine “Science”,  volume 365,  Issue 6458,  dated 13 September 2019,  as published by the American Association for the Advancement of Science (AAAS).   

#3. G. W. Johnson,  “Suit and Habitat Atmospheres 2018”,  posted 16 March 2018 to http://exrocketman.blogspot.com 

Figure 1 – Default Case is Best Case From Ref. 1 (0.45 atm at 45% O2)

Figure 2 – This Is the “Work Case 1” Worksheet,  Now In the Spreadsheet File (0.40 atm at 50% O2)

Figure 3 – This Is the “Work Case 2” Worksheet,  In the Spreadsheet,  and The Best Yet (0.43 atm 43.5%)

Addendum:  “Rule of 43” for Habitat and Suit Atmospheres

Here’s a design combination that is really easy to remember,  and yet gets just about as good an answer as the fully optimized form.  The optimum case had a habitat atmosphere that was 43.5% oxygen at 0.43 atm pressure.  It produced a minimum oxygen suit pressure of 2.975 psia.  The habitat satisfied the fire danger criterion,  and the long-term hypoxia criterion,  even leaked down 10%.  The suit met the no pre-breathe time requirement,  and the fully-cognitive short-term hypoxia criterion,  even when leaked down 10%.  It would be more easy-to-wear as a gas balloon design than current NASA suits,  by far!  It would be even more feasible and easy-to-build as an MCP suit than what Dr. Webb did in the 1960’s. 

The “rule of 43” case gets very similar results,  but is far easier to remember.  It uses a habitat atmosphere that is 43% oxygen at 0.43 atm pressure (both “43”).  It meets the fire danger criterion,  and meets the long-term hypoxia criterion if leaked down no more than 9.5% (it just barely fails at 10%).  The min suit pressure for no pre-breathe time comes out just a tad higher at 3.002 psia pure oxygen,  and meets the short-term fully-cognitive hypoxia criterion at 10% leaked-down.  Like the optimum case,  this would be far easier to wear as a as balloon suit,  and far easier to build as an MCP suit.

Figure 4 is the “rule of 43” combination,  and Figure 3 above is the optimum combination that I found earlier.  These were done with the spreadsheet tool I developed,  and in just a matter of less than an hour,  iterating through several possibilities where the atm of pressure and the oxygen percentage were the same numbers.

Figure 4 --  “Rule-Of-43” Design Case At 0.43 Atm Pressure And 43% Oxygen

These two cases are so close,  that I see very little difference between them.  If the objective of “something easy to remember” is as important as I have been told it is,  then this “rule of 43” design is the one you really want.  Its no pre-breathe min suit pressure is very slightly higher,  and its habitat pressure leak-down percentage isn’t quite the full 10%,  but that doesn’t really matter.  Both are in the very same ballpark,  with the differences out in the decimal places. 

The main point here is to get into that ballpark,  so as to reduce the min suit pressure for no pre-breathe way below NASA practice,  so that easier-to-wear gas balloon suits become feasible,  and that even easier-to-build MCP suits become possible.  These suit pressures are quite adequate,  but are far below what NASA and its favored contractors have been using (3 psia vs over-4.2 psia). 

You find out how adequate these lower suit pressures really are,  once you generalize the health and oxygen mask altitude criteria to wet in-lung oxygen partial pressures.  You need that generalization of those criteria,  in order to extend them correctly to lower pressures and higher oxygen percentages,  than those of Earthly air.  You also need a fire danger criterion cast in the mass/volume chemical concentration format.  And,  you need suit short-term hypoxia criteria based on Earthly use of oxygen masks for pilots at high altitudes.

Utter-Minimum Suit Pure Oxygen Pressures

I used the “work case 2” suit upgrade calculation block to investigate just how low a suit pressure was safe,  using the short-term hypoxia criteria.  Remember,  a wet in-lung oxygen partial pressure of 0.12 atm supports a fully-cognitive wearer.  0.10 atm supports survival without full cognition:  the wearer may well be somewhat nonfunctional mentally. 

Figure 5 is what I get if I require the fully-cognitive hypoxia criterion to the suit in the 10% leaked-down state.   Figure 6 is what I get if I only require the fully-cognitive hypoxia criterion to the design pressure;  leaked down 10%,  it fails fully cognitive,  but still satisfies bare survival.  The lesson here is that suit pressures as low as 2.675 psia will be quite adequate for fully-cognitive wearers.  2.407 psia will save life,  even if the wearer is mentally not fully functional.

Figure 5 – Min Suit For Fully-Cognitive When Leaked-Down 10%

Figure 6 – Min Suit For Fully-Cognitive Only At Design Pressure

A word of caution:  these utter-minimum pressure suit designs cannot be used indiscriminately with the two long-term habitat atmospheres identified so far (0.43 atm and 43.5% O2,  and the “rule of 43” design with 0.43 atm and 43% O2).  The utter-minimum pressure designs violate the min suit pressure specs for no pre-breathe time,  because the ratio of habitat nitrogen partial pressure to suit design pressure exceeds the 1.200 criterion. 

I include these utter-minimum suit design specs here,  to show what is actually feasible for adequate life support and mental functionality in pure oxygen suit designs,  when those designs are independent of a habitat pressure that must meet a long-term hypoxia criterion (for the safety of pregnant women and unborn/newborn children).