Supersonic Inlets for Ramjets

This is a more detailed version of an earlier posting on this topic.  That one,  "Inlets Capable of Supersonic Flight Use" dated 21 August 2026 below,  presumed the reader was an amateur.  This one presumes the reader actually knows something about compressible flow with shock waves,  and about how inlet performance data are usually book-kept and used.  

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Supersonic Inlets for Ramjets                                    

Supersonic inlets have spikes or ramps as external compression features that act before the airstream is captured at the cowl lip,  going to internal flow from there.  Spikes go with axisymmetric inlets that have circular cross sections,  ramps with two-dimensional (2-D) inlets that have a rectangular cross section.  The chin inlet is a variation on the nose-mounted axisymmetric spike inlet,  being just a sector of the full circle,  and using part of the vehicle nose as its external compression spike surface.   And,  there are a variety of side-mounted inlets,  both round or rectangular in cross section,  or even half-round.

The external compression surfaces create oblique shock waves with a flow deflection off of the axial direction.  The flow behind an oblique shock wave is still supersonic,  and the total pressure loss across the wave is quite modest.  There is at least one,  and most often,  two (or more),  such oblique waves in a typical supersonic inlet.  The last (“terminal”) shock wave is a normal shock,  perpendicular to the flow,  creating subsonic flow behind the wave,  and with a much larger total pressure loss across the wave,  when compared to an oblique shock at the same Mach number.  See Ref.1 for equations,  tables,  and charts.

By choosing the deflection angles, their geometric locations,  and the number of waves correctly,  about the same total pressure loss ratio across each wave can be had.  The sum of these losses is less than the loss across a single normal shock at the full flight Mach number (or even more if supercritical),  as in a pitot/normal shock inlet.

All of these inlets have a minimum cross section area called the “inlet throat”,  located at,  or just downstream of,  the inlet capture location into internal flow.  They all have divergent diffuser passages downstream of that throat,  where subsonic flow is finally achieved.  With the throat at the cowl lip,  there is no internal flow contraction,  these are called “all-external compression” inlets.  With the throat downstream of the cowl lip,  there is internal flow contraction for more compression,  these are called “mixed-compression” inlets.  The local Mach number at this inlet throat is always still somewhat supersonic.  There are no feasible all-internal compression inlets,  not with any technology known today!  In-line diffusers,  yes.   Inlets,  no. 

All of these inlets share similar-looking characteristic curve shapes for what is called the critical total pressure recovery ratio PRCR,  the critical captured streamtube area ratio ARCR,  and the additive drag coefficient C_Dadd.  The item of greatest influence on the shapes of these curves is the shock-on-lip Mach number,  that being the speed (measured as flight Mach number) at which the oblique shock waves created by the external compression surfaces are focused to fall exactly upon the cowl lip,  by deliberate design.

There is a modest slope change from below shock-on-lip to faster than shock-on-lip in the PRCR curve,  yet it still decreases from high values to low values as flight speed increases.  There is a sharp slope change at shock-on-lip speed in the ARCR curve.  Below shock-on-lip,  the recovered streamtube is much smaller than what is theoretically swept out by the cowl lip.  Above shock on lip,  the recovered streamtube is very close to that theoretical swept-out value.  What that really means is that the inlet can ingest lots of air flow above shock-on-lip speed,  and very little air flow below shock-on-lip speed.  The first priority by far for ramjet application is maximum possible ingested air flow rate!

There is also a sharp slope change in the C_Dadd curve at shock -on-lip speed.  C_Dadd is defined as the drag coefficient of “additive drag”,  based on the swept-out inlet capture area A_C.  The higher values at the lower speeds are the effect of minimally-decelerated still-supersonic air diverted past the cowl lip by the streamtube geometry below shock-on-lip.  This is because the local streamlines behind the oblique shock waves must run parallel to the external compression surfaces that created the waves.  Above shock-on-lip speed,  the C_Dadd values are low,  and in the case of nose-mounted inlets,  often zero.

All of these behaviors and characteristics are illustrated in Figure 1.

Figure 1 – Basic Characteristics of Supersonic Inlets with External Compression

These components must be used differently with turbojets versus ramjets,  because of the quite-different characteristics of those engines.  The turbojet is almost like a positive-displacement pump,  in that,  at any given rotation speed and air density,  there is only one engine air massflow!  Rotation speed is determined by the throttle setting.  The turbojet inlet must deliver the exact air flow rate that the engine demands,  regardless of the flight speed and the inlet ARCR recovery characteristic curve!  To do that,  it must operate “subcritically”,  with the terminal shock “unswallowed”,  and thus located on the external compression surface in front of the cowl lip,  as shown in Figure 2.  There is a sometimes-large spillage of subsonic air around the cowl lip,  in order to deliver the “right” ingested air massflow rate to the turbojet engine.

In contrast,  the ramjet acts like a simple obstruction,  producing a pressure at the entrance to the min obstruction area that depends only on the total air and fuel massflow rates fed to the engine,  and the combusted temperature and properties corresponding to them.  The thrust of the ramjet depends most strongly on the amount of air flow ingested!  That means the inlet must be operated supercritically (with a swallowed terminal shock),  for ingesting the maximum airflow!  The more air,  the higher the combustor pressure,  and the higher the combustor pressure,  the greater that nozzle thrust force!  This is also shown in Figure 2.

Figure 2 – The Same Components Must Be Used Differently for Turbojets and Ramjets

Exactly how the ramjet engine-inlet balance works is shown in Figure 3,  for which the most important behavior is supercritical versus subcritical operation.  The inlet characteristics are represented by the cross plot of PRCR versus ARCR at any one flight Mach number,  very similar to the one shown in Figure 1,  just with some extra details added here.  The corresponding depictions of the inlet flow field and the distribution of conditions through the engine are shown in the figure,  one each for subcritical operation,  operation exactly at the critical inlet point,  and for supercritical operation.  As already discussed,  best ramjet performance obtains when ingested air flow rate is maximized (supercritical inlet). 

Note that the ramjet engine determines the total pressure at the nozzle entrance P_t4 from the flow rates,  and it determines the pressure drops across hardware items and flame zones,  so that it determines the actual operating total pressure P_t2 at the inlet diffuser outlet!  The inlet determines only the maximum-possible diffuser total pressure P_t2CR! 

Only at critical are these equal!  Supercritically,  P_t2CR > P_t2,  the difference measured by the supercritical pressure margin PM.  If the engine-demanded P_t2 is too high,  the inlet will instead operate subcritically,  and spill just enough air to make P_t2 = P_t2CR.  The amount of this air spillage is measured by the subcritical spillage margin SM.

Figure 3 – Exactly How the Engine-Inlet Balance Works with Ramjet

So,  for a supersonic inlet,  there are basically 3 modes related to shock-on-lip speed,  and 3 modes related to inlet criticality.  That’s a total of 9 possible modes and flow patterns,  as depicted in Figure 4.  The critical-inlet condition right at shock-on-lip speed is the design point for the inlet (but not necessarily for the engine-inlet system in the ramjet).  All supersonic inlets,  regardless of the application,  share these 9 behaviors.  Only some of them are appropriate for ramjet,  and only some of them for turbojet.  In the upper left illustration,  both the streamtube geometry is reduced,  and there is subcritical spillage.

Figure 4 – The Nine Behaviors Common to All Supersonic Inlets

The differences between all-external compression inlets and mixed-compression inlets are shown in Figure 5.  The mixed-compression inlet has both external compression by oblique shock waves,  and internal compression by both passage contraction and another oblique shock wave.  The all-external compression inlet has no internal compression,  only an always-divergent internal passage!  It only has the external oblique shock waves,  and its min-area throat is right at the cowl lip station.  At inlet design Mach,  both types of inlet have a terminal normal shock very close to the min-area throat, wherever it is.

The all-external compression inlet has a higher cowl lip drag because of its strongly-curved shape toward the spike or ramp.  But it has no internal contraction,  and so is easy to start (swallow the shock system),  because that geometry entirely avoids the Kantrowitz-Donaldson conundrum (see Ref. 2) peculiar to internal supersonic contractions!  It helps if the demanded backpressure at start is also low,  at values more like large supercritical margin. 

Without any throat bleed means,  the initially-subcritical mixed compression inlet throat area simply cannot subsonically pass the full swept-out supersonic massflow rate (at its design speed),  thus requiring very serious overspeed above design Mach,  in order to start!  Even so,  in order to start at overspeed,  the demanded backpressure must also be low,  corresponding to levels seen at high supercritical pressure margin. 

This difficulty with this approach is that once the inlet is started,  if you slow down to,  or below,  design speed,  and also happen to experience inlet unstart for any reason whatsoever,  you cannot re-start the inlet!  There is no restart,  unless you have some other means to re-accelerate the vehicle back up to the feasible starting overspeed.

Throat bleeds can be through the lateral cowl cheekwalls,  as cutback slots in the 2-D variants,  or by slots cut in the axisymmetric cowl wall tube from ahead of,  to just past,  the throat.  It is also possible to put a throat bleed slot in the centerbody spike or ramp,  leading overboard directly in the 2-D variant,  and leading outward through the centerbody support struts,  for the axisymmetric variant.

Figure 5 – Characteristics for All-External Vs Mixed Compression Inlets

The supersonic inlet has a swept-out capture area defined by the cowl lip and the bottom or centerline of the ramp or spike external compression surface.  When viewed from ahead,  it is obvious to even-the-untrained-eye that the ramp or spike features present an obstruction to the oncoming flow.  If the oblique shock waves are formed properly by the external compression surfaces,  this blockage is not a problem,  as those waves divert the flow parallel to the external compression surface,  and compress it to a smaller size that actually will fit through the available passage area at the inlet throat station!  This is illustrated in the right-hand image of Figure 6.  This is still true,  even if there is some air not ingestible due to the streamtube and shockwave geometry,  while traveling at somewhat lower than the supersonic shock-on-lip speed.

However,  as speed decreases further,  there comes a point where the external compression surfaces cannot maintain the existence of oblique shock waves that are attached to the surface.  The shock system detaches,  and becomes a curved bow wave,  out in front of the external compression features at some standoff distance,  with locally-normal shock characteristics.  This is shown in the middle illustration in Figure 6.  A nominal speed at which this occurs is shown in the figure,  but the actual value depends upon the angles off axial of the compression surfaces.  The reader is referred to the ramp and cone charts for oblique shock waves in NACA 1135 for further details. 

This behavior persists at some bow shock standoff distance that varies,  until flight speed is subsonic,  and the bow shock disappears entirely.  Flow ingestion is still very poor due to the presence of the obstruction that the subsonic approaching flow can “sense”.  This is shown in the left illustration in Figure 6.

Figure 6 – Low-Speed Behaviors Seen Only in Turbojet Installations

The only “fix” by means of which to increase air ingestion is the spring-loaded blow-in door,  shown in the bottom illustration of Figure 6.  This only works if a suction can be pulled in the inlet duct,  and only a gas turbine can do that.  Ramjet cannot.

Various inlet integrations are possible.  For modern high-speed combustor layouts,  some options are shown in Figure 7.  The old stovepipe-engine designs with V-gutter flameholders,  used in the 1950’s,  were suitable only as engine nacelles added to the basic vehicle,  as in the IM-99 Bomarc interceptor missiles.  In the stovepipe designs,  there is no place inside the engine structure,  in which to package anything,  even the fuel.  And these were limited by materials survivability issues,  to flight speeds under about Mach 3. 

The nose inlet offers the lowest vehicle drag,  with the air transfer duct either coaxial along the centerline as illustrated,  or alternatively,  as an annular passage about a centerbody containing the equipment and fuel. 

The chin inlet is sort-of like a circumferential segment of a nose inlet,  using part of the vehicle nose as its external compression spike.  But,  to achieve shock-on-lip at a reasonable flight Mach number,  the nose half-angle may have to be steeper (more drag) than would otherwise be desired for low drag but high-volume packaging.  Even so,  it still offers a very low-drag vehicle design,  plus it is well-adaptable to noncircular vehicle cross sections that have the flat bottoms by which to be “wave riders” for higher lift.  ASALM-PTV was one of these,  and reached Mach 6,  although that was by accident.  It was designed for cruise at Mach 4,  limited more by materials survival than by thrust-over-drag.

The side entry inlets offer packaging in the front of the vehicle without any geometric interference from the air transfer ducting.  They do increase the vehicle drag,  so that top speeds usually fall in the Mach 3 to 4 range,  limited by thrust-over-drag.  These can take a variety of forms,  leading to a variety of different sudden-dump flameholding geometries. 

The single side inlet offers no added lift capacity,  only just the inlet fairing drags,  which are cowl lip,  skin drag,  aft boat-tail pressure drag,  and aft face base drag.  All of these are traditionally charged against airframe drag,  no matter the thrust-drag accounting scheme.  The inlet needs to go on the belly,  so that at lifting angles of attack,  the inlet flow is not blocked by the vehicle body.  Remember,  ramjets cannot suck air like a pump,  only gas turbines can!

The two-inlet configurations are either symmetrically placed on the two sides,  or asymmetrically placed on those two sides,  but at or below the horizontal.  Both of these geometries offer added lift from the inlet fairings,  which can replace the presence of the forward wing-fins of missiles.   You really do not want inlets anywhere around the dorsal side,  as they have a hard time ingesting air:  the missile body blocks the oncoming stream to one extent or another.

Three inlets are possible,  but that configuration has not been used.  It always suffers from one or two inlets suffering the “dorsal inlet” problem,  to one extent or another. 

Four inlets might do better in the X-configuration,  but in some cases having the fins in the X-configuration might be more important to the vehicle designer.  There are missiles out there with X-configuration inlets,  like the “Sunburn” anti-ship missile.  There was another with the fins in X,  and the inlets in cross-configuration,  as shown in Figure 7.  That was the SA-6 “Gainful” surface to air missile.  Both work.

Any of the illustrated geometries are able to serve as flameholders for LFRJ engines,  but not the GG-fed RJ’s that do not use hypergolic magnesium fuels!  The asymmetric two-inlet configuration is the most successful for GG-fed RJ using fuels that do require flameholding.

There is a preferred location zone for the capture features of any of the side inlet configurations.  This is about 4 to 6 diameters aft of the nose.  Too far forward,  and the flow about the body has not yet re-stabilized from the disturbances presented by that nose.  That puts unrepeatability into the inlet capture characteristics.  Too far aft,  and you get into inlet and fin interference,  plus increased additive drag along the greater wetted length.

Figure 7 – Various Inlet Integrations Are Possible

The SFRJ to date has shown a preference for nose or chin inlet designs,  although side inlets could also feed the same air plenum just ahead of the fuel chamber.  The real design restriction would be,  not being forced to put the side inlet capture features too far forward. 

A very important aspect of the design of ramjets or gas turbine-powered vehicles is the flight envelope.  This is a region in altitude-speed space in which the inlet/engine combination is expected to operate,  and is not expected to operate outside of it.  This kind of thing is illustrated in Figure 8.  Bear in mind that the minimum ramjet flight speed is an appropriately-high ramjet takeover speed,  while the minimum gas turbine speed is literally zero on the surface up to some elevation,  and below vehicle stall speed above it.

As already discussed above,  the minimum takeover speed of a ramjet is usually where you set the design shock-on-lip Mach number for its inlet.  Somewhere along that low-speed boundary in the flight envelope,  is your ramjet design point!  At design,  and at the max mixture ratio expected,  you need enough supercritical pressure margin PM at engine design,  to maintain a PM > 0 all along and near that inner boundary.  PM will increase as you speed up across the envelope toward its outer boundary,  and it will also increase as you lean back mixture ratio in the ramjet engine.  Ambient air temperature also affects it.

Most gas turbine installations do not use actual supersonic inlets,  they use the simpler pitot/normal shock inlets,  because they never fly more than about Mach 2.5.  Pitot/normal shock inlets are a separate topic,  not discussed here.  They operate down to very subsonic speeds.

But for a really high-speed gas turbine installation,  not only are the same inlet components used differently,  but the design approach itself is entirely different!  Right up to the maximum possible speed,  you want the oblique shocks to fall ahead of,  or at worst on,  the cowl lip.  (That is utterly different than what you do designing for ramjet!)

That high-speed-side shock-on-lip gives you full freedom to spill air with subcritical spillage margin all across the flight envelope,  in response to changes in engine throttle setting (and engine core rotation speed).  So,  your inlet design shock-on-lip Mach number is the highest speed you ever expect to fly with gas turbine.  To change that,  requires a translating-spike variable inlet geometry technology,  something done with the SR-71.

With gas turbine installations,  both the nozzle throat and nozzle exit areas are variable.  Their maxima get set by the max thrust available at max throttle setting at low altitudes. 

The selection of the inlet capture area A_C is a compromise between the large values needed at low altitude (and ground running),  versus all the rest of the flight envelope.  This gets compromised further by how many blow-in doors are included. 

If you really have a supersonic inlet with a gas turbine installation,  you may have to seriously consider including variable inlet geometry,  in the form of relaxing the compression surfaces back to “flat” relative to the oncoming flow.  That is how you get the removal of the obstruction effect,  that you otherwise inherently have with supersonic inlet technology,  at low or subsonic speeds,  or even up to around Mach 1.5.

Figure 8 – Ramjet and Gas Turbine Use Different Design Approaches

There are a lot of internal flow problems in all of these different inlets,  which can be “fatal” to a given design.  That is also beyond scope here,  being a separate topic entirely,  as are the pitot/normal shock inlets themselves. 

There is also a variation on the mixed-compression inlet that starts easily without overspeed or bleed slots.  It is called the “shock-follower inlet”,  and it compromises its pressure recovery with suboptimal internal shock strengths and locations to accomplish this!  The air ingestion was not compromised,  as this was for a ramjet engine application on the old Russian surface-to-air missile known to NATO as the SA-6 “Gainful”,  which had 4 axisymmetric side-mounted mixed-compression side inlets.

The means to accomplish this was undersizing the centerbody,  in order to oversize the inlet throat area enough to pass the swept-out airflow subsonically.  This is often done in supersonic diffuser work,  per Ref. 2,  although many diffusers are adjustable to a smaller,  more-efficient throat after the shock system is swallowed.  In the SA-6,  throat oversize was done,  and left that way at fixed geometry,  in order to swallow the shock system easily in a very simple design.  That pushed the terminal shock at critical away from the throat,  and closer to the full duct area,  at the rear of the centerbody.  Interference with the waves shed by the centerbody struts does complicate this shock field,  but we will ignore that here.

Subcritically,  all of this unswallows out in front of the cowl lip as with all the other supersonic inlets.  The SA-6 being a ramjet,  operating subcritically was avoided by design,  even at the takeover points.  Supercritically,  there is a complicated train of oblique shocks trailing off the centerbody down into the constant-area ducts.  The terminus of this was complicated,  but effectively it is like a weak normal shock somewhere down in that duct.  Having long ducts to accommodate large supercritical margins is essential.  See Figure 9.

References:

#1.  NACA Technical Report 1135 “Equations,  Tables,  and Charts for Compressible Flow”,  Ames Research Staff,  1953.

#2.  Kantrowitz, A., and Donalson, C., “Preliminary Investigation of Supersonic Diffusers”,  NACA TR L5D20,  1945.

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Trump Lied, He Brought You Far Higher Prices Instead

Donald Trump ran his 2024 campaign promising you prosperity,  in return for your vote for him and his utterly-loyal minions.  Look at your fuel pump and grocery store bills!  He lied!  Between his trade wars and tariffs,  and his war with Iran,  all those prices are up very drastically!  Your pay is not!  Fact,  not opinion!  Hence,  the exaggerated illustration below. 

And it will get worse,  since about a quarter to a third of the world’s petroleum is bottled up in the Middle East,  because of Trump’s war with Iran!  Fuel and energy prices drive the price of everything else!   It’ll take another 6 months to a year,  for the full effect of that shortfall to set in,  only because the economy is so big.  Those are the facts,  not opinion!

He’s doing it again,  lying and trying to bribe you for your vote,  for the upcoming midterm election,  trying to get his preferred choices elected,  to maintain his control of Congress.  $5000 per taxpayer,  I believe it is.  The track record is this:  essentially every claim Trump has ever made that was actually fact-checked,  has proven false!  None of you have any logical reason to believe anything he says at all!   Again,  fact,  not opinion!

My recommendation:  do not believe a word of what Trump or his minions say!  We cannot afford the hundreds of billions of dollars that the promised $5000-per-taxpayer would cost,  conduct a war,  and try to replenish depleted weapons inventories,  all with a $40 trillion dollar-and-rising deficit in a climate of rising interest rates,  plus continue his tax-cuts-to-near-zero for only his billionaire friends and donors!  That’s about as factual as it gets! 

If you are tired of all the lies,  tired of the rapidly-escalating prices,  tired of all the idiotic pointless drama (and possible treason) with foreign affairs,  and tired of all the billionaires taking all the money from you,  then you should vote for somebody other than Trump and his minions!  And that’s a fact,  Jack! 

My opinion:  you cannot do any worse,  but you might do better,  no matter who the opposition figure is!  And that goes for state and local,  too!

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 Update 10-4-2026:   this is the fourth of 4 articles published here,  about Trump and the threats that he and his minions pose to America.  Please vote accordingly this November!  The 4 articles are:

Date                    title      

9-19-2026        Trump Dictatorship Evidence

9-24-2026       Trump Treason Evidence

9-29-2026       Trump Lies,  He Lost the Iran War

10-4-2026       Trump Lied,  He Brought You Far Higher Prices Instead  (this one)

Trump Lies: He Lost the Iran War

A word of advice for all readers:  do not listen to what your politicians say,  observe only what they do!  There is an old saw:  “a politician is lying if his lips are moving”.  While that is generally an overstatement,  with Trump (and his minions) it is almost literally true!  Essentially every claim by Trump that was fact-checked,  has proven to be false,  many quite egregiously so!  That is NOT opinion,  it a fact-on-the-ground,  staring you in the face!

The fact on the ground about Trump’s Iran war,  is that he started a war that he could not possibly win,  and so he inevitably lost it! 

It was unclear why he started it for multiple weeks.  The final “reason” offered,  was “no nuclear weapon for Iran”.  We did NOT achieve that goal:  Iran still has its enriched uranium supplies,  buried deep underground beyond the reach of our weapons!  Fact,  not opinion!

Because of the war,  they are quite probably also building the equipment to make bombs of their enriched uranium,  also buried deep underground,  beyond reach of our weapons!  That’s much closer to fact than it is any opinion!

We cannot invade and dig up the materials to take them:  our available forces are too small to mount an invasion that large,  get that far into the country,  and hold off attack from all sides,  while digging-up deeply-buried materials!  Fact,  not opinion!

Trump bragged that Iran’s air force,  air defenses,  and navy were destroyed during the first days of fighting.  While that is actually true,  it is irrelevant!  Iran was NOT planning on fighting its war with us by using those assets!  They had 47 years to plan a very asymmetric war with us:  using proxy terrorist armies,  and deeply-buried supplies of missiles and drones,  plus deeply-buried production facilities for them.  Fact,  not opinion!

The proof is that even today,  after Trump supposedly destroyed their capabilities,  Iran is flinging many missiles and many drones at our bases in the region,  and at our friends and allies,  and at ships in the Strait of Hormuz!  Plus soon,  the outlet of the Red Sea may also get closed,  by Iran’s terrorist proxy army in Yemen,  the Houthis. 

And the closure of the Strait of Hormuz precisely because of Trump’s war with Iran has already cost you dearly at the fuel pump!  Those effects will spread throughout the economy for some time to come,  since fuel powers everything in the economy!  And that will cost you even more!

One possible reason for starting this war was ending Iran’s use of its many terrorist proxy armies.  So far,  none but Hamas has been sharply reduced,  but by the Israelis,  not us,  and even then only by methods that amount to genocide in Gaza.  Hezbollah in Lebanon has suffered some damage from the Israelis (not us),  but is still intact enough to fight.  The rest (there are many,  notably the Houthis) are all unaddressed!  Fact,  not opinion!

Here is a related opinion:  one can oppose the current government of Israel,  without being anti-Israel or anti-semitic!  It was wrong of political figures to falsely frame that issue as “either/or”,  playing right into the hands of extremists and terrorists!  It was wrong of the news media to go along with that false framing,  and most of them did!  Very few will yet publicly say what I just said in the first sentence of this paragraph!  Yet it is quite true!

Back to facts:

Here of late,  Trump’s “reason” for his war has shifted to “reopening the Strait of Hormuz”,  because closing it has cost us so dearly already,  at the fuel pump.  Be aware that it was wide open before he started his war!  Now that the Iranians know “for sure” that their missile and drone threat can shut the Strait traffic down,  it will never again be a freely-open international waterway!  And,  they seem about to use their Houthis in Yemen to close the Red Sea outlet,  too,  cutting off essentially all Middle Eastern oil and driving prices far higher still,  any time they want to do it!  Fact,  not opinion!

The actual objectives were (and are):  no Iranian nuke,  no terrorist proxies,  a freely-open Strait of Hormuz,  plus possibly toppling the Iranian regime.  The only real way to have accomplished any of these goals was to actually topple the Iranian regime.  That regime before the war was a sham democracy in which the Supreme Leader plus some clerics ruled,  propped up by their terrorist private army the Iranian Revolutionary Guard Corps (IRGC).   The IRGC had also infiltrated and controlled the Iranian military for them. 

Now,  after Trump started his war and killed several Iranian government officials,  the terrorist army (IRGC) is pretty much in full control,  ready to fanatically die to the last man,  rather than negotiate,  and quite willing for us to commit genocide by bombing their people!   Trump has made that situation much worse with his war,  not better!  Fact,  not opinion!

And,  by the way,  bombing their country with collateral damage like that infamous school,  has turned the Iranian opposition into supporters of their regime.  It’s an “us versus them” thing!  So,  there is no longer any hope of an internal revolution toppling it from the inside!  There really was such hope,  before Trump started his war!  Fact,  not opinion!

The only way left to achieve any of the goals (of which NONE have been achieved!!) is to invade and topple the Iranian regime the hard way.  Based on our WW2 experiences,  that would take an invasion force on the order of 1 to 2 million troops,  to sweep the entire country,  and root-out and kill all of the IRGC,  who will fanatically die to the last man rather than ever surrender!  The US cannot possibly do that alone,  it has only about 200,000-300,000 people in all its armed forces,  total!  And Trump has alienated all our allies!  Fact,  not opinion!

The truth about this war being a failure,  attributable directly to Trump,  is finally starting to come out!  He punishes news media who reveal it with lawsuits,  by being barred from events,  and with threats to their operating licenses!  We have greatly depleted our stocks of critical air defense interceptors,  and a lot of our longer-range strike weapons!  It will take years and billions of dollars to replace them!  Therefore,  Trump has made us much more vulnerable,  by that depletion of our weapon stocks,  in any other wars our enemies might well start against us!  Like over Taiwan.  Or the Baltic NATO states.  Or Poland.  All fact,  not opinion!

Trump spent our resources and left us vulnerable,  fighting a war that he started,  but which he could not possibly win!  Previous presidents were told about these dangers and chose not to start a war they could only lose.  So also was Trump informed,  but he chose to start the war anyway,  and now has lost it!  So,  he is now searching desperately for any off-ramp by which to “declare victory” and get out.   

The Iranians lead him on in the “peace talks”,  when they bother to talk at all.  They have no reason to give him that off-ramp,  because they know they won!  That is precisely why this thing has dragged on for so long!  Fact,  not opinion!

Opinion:  incompetence on that colossal of a scale,  which involves waging a war,  and which borders on treason,  cannot go unaddressed! 

It is way past time to get rid of Trump,  before he finishes destroying the US economy and its military!  He has already destroyed our reputation around the world,  and weakened or destroyed our alliances that protected us from our enemies.  He has already cost you dearly at the fuel pump,  and those costs will only rise further and spread throughout the economy!  Hence the appropriateness of the illustration: 

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Search keywords:  bad government, idiocy in politics, treason

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Update 10-4-2026:   this is the third of 4 articles published here,  about Trump and the threats that he and his minions pose to America.  Please vote accordingly this November!  The 4 articles are:

Date                    title      

9-19-2026        Trump Dictatorship Evidence

9-24-2026       Trump Treason Evidence

9-29-2026       Trump Lies,  He Lost the Iran War  (this one)

10-4-2026       Trump Lied,  He Brought You Far Higher Prices Instead

Trump Treason Evidence

Update 9-27-2026:  added bits of text in red a couple of places below,  to indicate how the treasons of damaging the alliances costs you right in your bank accounts!   As well as endangering your freedoms and your lives.

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The Constitution defines two,  and only two,  things that can be called “treason”.   One is a citizen directly making war upon the US.  The other is “providing aid and comfort to the enemy”,  and that is the thing discussed here.

Trump has been waging trade wars and imposing tariffs upon our friends and allies,  angering them,  alienating them,  and making them go elsewhere for trade,  and to seek new alliances (without us).  Canada is just the latest example among many.  Prices for food,  fuel,  and construction materials have risen drastically,  precisely because of those trade wars!  That hits you in your bank accounts!

These were the alliances that protected us from our enemies,  such as Putin’s Russia,  Xi’s China,  Kim’s North Korea,  and the sham democracy that is now terrorist-ruled Iran.  Our enemies have long wanted to weaken or destroy our alliances,  but they could not. 

Now Trump has done it for them!  That is not opinion,  those are the facts upon the ground,  staring everybody right in the face!  Every ally alienated,  and every alliance weakened,  is another count of “aid and comfort” treason!

We have a friend and ally in Ukraine,  who has been holding back Putin’s desire to reconquer much of eastern Europe.  We were supporting Ukraine with weapons and aid,  until Trump took office for his second term.  He essentially stopped US support for Ukraine,  and has repeatedly pushed them to accept Putin’s demands,  in order to end the war.  That would amount to Ukraine’s surrender!  Those,  too,  are the facts,  not opinion at all!  

Ukraine holding back Putin invasions of eastern Europe meant that we and NATO did not have to!  We spent less sending Ukraine aid than we would have spent militarily opposing Putin.  Ending that will hit you in the bank account again!

Trump has therefore effectively tried to destroy our ally Ukraine for Putin,  and that is indisputably aid and comfort he has provided to our enemy Putin!

These many Trump treasons just described demand that he be brought to justice! 

The Department of Justice will not do it,  for Trump has packed its leadership with his utterly-loyal supporters,  and they have driven out all who might act against him. 

Congress cannot punish him,  but it could remove him by impeachment,  so that he cannot commit more!  However,  it has an egregious track record of letting Trump do whatever he wants under Republican control,   because Trump completely controls that party!  Part of that is using your tax dollars trying to build monuments to himself.  And if the reflecting pool is any indication,  he does a bad job of these things,  and so wastes even more of your money!

Part of them are just utterly-loyal to Trump,  and the rest have completely sold out to him,  in order to stay in office and not to be “primaried”.  It has degenerated into a Trump cult of personality,  the exact same way the Nazi party became a Hitler cult of personality!  And he has almost completely imposed a dictatorship from the inside,  just like Hitler did,  but that is another story! (See the article just below,  dated 9-19-2026.)

We need a Congress that will actually do its job for we-the-people!  This one is not it!

Here is the only opinion in this entire article:  control of Congress needs to change with the upcoming midterm elections,  or Trump will continue committing treasons until he finally destroys our democracy completely!  Hence,  the illustration:

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Search code DDMMYYYY format:   24092026

Search keywords:  bad government,  idiocy in  politics,  treason

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Update 10-4-2026:   this is the second of 4 articles published here,  about Trump and the threats that he and his minions pose to America.  Please vote accordingly this November!  The 4 articles are:

Date                    title      

9-19-2026        Trump Dictatorship Evidence

9-24-2026       Trump Treason Evidence  (this one)

9-29-2026       Trump Lies,  He Lost the Iran War

10-4-2026       Trump Lied,  He Brought You Far Higher Prices Instead

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Update 10-10-2026:  Trump doing a deal with Putin for Russian diesel is nothing but an ineffective stunt to win votes for his people in the midterm election,  trying to overcome voter anger over fuel prices.  But it is also yet another count of treason,  in addition to all those described above! 

The "deal" was relaxing the economic pressure of a ban on Russian oil and oil products,  for a little bit of diesel fuel,  that cannot affect fuel prices in any noticeable way,  because the quantity is too small.  It just looks like Trump is trying to do something about fuel prices.  Appearance only!

That economic pressure on Russia was the only remaining significant US support for our embattled ally Ukraine,  because Trump stopped sending them weapons and money when he took office for this term.  Putin will use the money he gets for that diesel to kill more people in Ukraine!  And Trump is therefore directly helping Putin to kill those people in our ally Ukraine! Treason!  Committed right in front of your eyes!

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Trump Dictatorship Evidence

The first image below is my spreadsheet that tracks 10 hallmarks of a dictatorship.  As of this date,  I see 8 fully in place,  and 2 mostly in place.  The secret police force is definitely in place,  with them killing both demonized immigrants and US citizens who protest too strongly,  plus “detention centers” (concentration camps) where inmates die of neglect.  Immigrants are “disappeared” by deportations without due process,  instead of gas chambers.  Opponents are next!

The second image is my view of the political spectrum as a circle,  not the straight line that everybody thinks it is!  I see free societies on one side of the circle,  and authoritarian dictatorships on the other side.  There are two paths to the other side,  but once there,  there is no difference in behavior!  It does not matter what they say,  only what they do!

A military leader recently said in public that no troops would be sent to polling places during the November midterms.  Given that Trump has cashiered most of the higher officers who will not back him,  and that the fact-checking track record says about 100% of Trump’s claims are lies,  I do expect to see troops at polling places in November!  If Trump thinks he is losing control of Congress,  I predict that he will declare martial law and have the troops confiscate the ballots and voting machines from the polling places!

And THAT will be the final end of a free and democratic America!  On its 250^th birthday!

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search code DDMMYYYY format:      19092026

search keywords:          bad government,  idiocy in politics,  treason

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Update 10-4-2026:   this is the first of 4 articles published here,  about Trump and the threats that he and his minions pose to America.  Please vote accordingly this November!  The 4 articles are:

Date                    title      

9-19-2026        Trump Dictatorship Evidence  (this one)

9-24-2026       Trump Treason Evidence

9-29-2026       Trump Lies,  He Lost the Iran War

10-4-2026       Trump Lied,  He Brought You Far Higher Prices Instead

Starship/Superheavy Hot Staging

This is not insider knowledge.  It is based only upon what SpaceX has publicly released. 

There is some kind of geometrically-shaped shield plate that protects the front end of the Superheavy booster where the forward dome of the forward propellant tank is otherwise exposed.  This shield was shed after hot staging with Version 2,  but is now integral to the booster stage in Version 3.  It deflects the plumes of the Starship upper stage engines,  from striking and damaging or destroying that forward tank end,  during hot staging.

This shield structure is coupled with an interstage ring between the stages,  part of the Superheavy,  that is “porous”,  in the sense that there are openings through which the deflected engine plumes can exit laterally,  in a more-or-less radial direction,  during the transient hot-staging event.  The force to turn a plume gets exerted upon that shield.

The Superheavy booster had four grid fins spaced 90 degrees apart,  in Version 2.  Plume blast damage had been noted to the grid fin rotated into the way of plumes,  during the booster flip maneuver,  in Version 2.  In Version 3,  there are only 3 grid fins,  still spaced 90 degrees  apart,  but somewhat larger than the Version 2 grid fins.  That leaves a space where there is no grid fin,  which is clocked to align with the dorsal side of the upper stage Starship,  as shown in Figure 1. 

Figure 1 – Version 3 Starship/Superheavy Arrangement and Intended Booster Flip Direction

The design direction of the booster flip is a plane aligned with the dorsal-ventral plane of Starship,  and the front of the booster is supposed to flip in the direction where it moves “down” as shown in the figure.  Thus,  no grid fin is exposed to plume blast damage anymore,  in Version 3.  The side of the booster is less vulnerable to plume blast damage,  being cooled by the cryogenic propellant vapors inside.  

In Version 2,  the torque to flip the booster came from a strong gimbal angle of the 3 booster engines firing during the staging event to keep the booster propellants settled into the aft ends of their tanks,  where the suction-feeds to the engines are located.   This is still the case in Version 3,  with some control of the deflected plume force directions added,  by one or both of two means:   (1) the geometric shaping of the shield and of the “porosity” of the interstage ring,  can favor a plume deflection force component in the intended flip direction,  and (2)  the startup sequencing of the Starship engines can also produce a temporary plume deflection force component favoring the intended flip direction. 

There are two separate effects going on during the hot-staging event,  which must both be successful,  but which are also linked to each other in ways that make the successful “solution space” rather small!  These are indicated in Figure 2 below,  which depicts the conditions as the hot staging begins,  but before the flip starts.  (Drag was ignored.)

First,  the acceleration of the upper stage Starship has to be larger than the acceleration of the Superheavy booster (before the flip starts),  in order not to risk a collision. 

Second,  the axial acceleration of the Superheavy booster must be a positive number large enough to keep the propellants settled,  all during the staging event,  and all during the flip maneuver. 

That last is also complicated by the flip motion possibly flinging the propellants forward,  in only the forward tank,  if the flip is too fast!

The variables available for controlling this event are the thrust levels used in the booster and upper stage engines,  the shaping of the shield and interstage ring porosity geometries,  and the sequence of ignition of the upper stage engines. 

To simplify this first look,  the author chose only a full thrust setting in the 3 booster engines,  and lighting all 6 upper stage engines at once,   but a some reduced thrust.  Guesses were made for plume deflection force component angles and booster engine gimbal angles.   All of this is indicated in the figure.

The author has no actual data for the engine thrust levels at the staging altitude,  or for the actual masses of either stage at the time of staging.  He made reasonable guesses for these,  as well,  as indicated in the figure.  So the results are inherently approximate!

Figure 2 – Finding A Thrust Setting For Starship That Keeps Superheavy Accelerating

It would not be possible to get full thrust in an engine at the moment of ignition!  It is more practical to ignite at a partial-thrust setting propellant flow rate,  stabilize after a split second,  and then throttle up quickly a split second after that,  as desired. 

The author chose to look at full and half thrust initially,  and then added a 40% thrust setting,  after getting negative booster acceleration at full upper stage thrust,  and zero booster acceleration at half thrust.  The 0.1 gee booster axial at 40% Starship thrust is in the rough ballpark of other ullage thrust applications.  The 40% thrust setting is within the capability of the Raptor-3 engine design,  so this point really is a feasible thing to do!

As the figure indicates,  the Starship upper stage has the acceleration to leave the booster behind,  at 40% thrust on 6 engines.  It cannot throttle up until the flip has proceeded enough to direct the front end of Superheavy out of the way of the Starship engine plumes.

Also indicated in the figure,  the Superheavy axial acceleration is zero at half Starship thrust,  and only 0.10 gees at 40% Starship thrust.  Starship cannot throttle down much more than that,  and still leave the vicinity at about 0.4 gees!  Which is exactly why this author says the solution space here is quite narrow!  Screw this up,  and the propellants will unsettle,  the booster engines will suck vapor,  and their turbopumps will explode!

The next step was to look at starting the booster flip.  This is illustrated in Figure 3,  which presumes the 40% thrust solution just obtained above.  Two cases were examined:  a booster engine gimbal angle of 10 degrees,  and a comparable lateral deflection force generated by shield geometry and/or interstage porosity distribution.  The booster mass moment of inertia was approximated by the solid bar formula for rotation about its center of gravity (cg).  That cg was simply presumed to be halfway along the booster.  

Figure 3 – Starting the Booster Flip Maneuver During Hot Staging

The results for time-to-clear shown lower right of figure are amazingly close to what is in the publicly-released videos of these flight tests (about a second or two to clear)!  Considering how crude all the assumed data is,  that outcome is quite remarkable!  Letting deflected upper stage plumes help the gimballed booster engines to start the flip maneuver is definitely beneficial,  but it is not an overwhelming effect.  That would seem to be the lesson to be learned here.

That brings up the “spin gravity” effect of the flipping booster upon the settling of propellants in its forward tanks by engine-induced acceleration.  As depicted in Figure 4,  this depends upon which side of the booster cg falls the free surface in the forward tank.  One must take into account relative tank sizes,  and how full those tanks are.  A very crude estimate is shown in the figure,  indicating that spin will help settle the propellants.

Figure 4 – Evaluating Whether Spin of Flip Affects Propellant Settling

Note that had the LOX tank been forward in the design instead of aft,  this outcome would not be true!

The magnitude of the “spin gravity” effect depends upon the rotation rate ω at the time the booster clears the plumes,  which is crudely angular acceleration times the clearance time,  for the two cases shown in Figure 3 above. Those would be 0.139 rad/s for the gimbal only case,  and 0.186 rad/s for both effects together. 

The acceleration in gees at the free surface would be L ω²,  where L is the distance between the cg and the free surface.  As measured from the left as shown in Figure 4,  as long as the free surface is left of the cg,  the spin gravity gees adds to the axial thrust gees.  If the free surface falls to right of the cg as shown in the figure,  then the spin gees would subtract from the axial gees!  There is a coupling between stage layout and “spin gravity” risks.

For the dimensions indicated in Figure 4,  the LCH4 free surface is 10 m left of the cg. So,  if only gimballing,  one would add about 0.020 gees to the axial 0.1 gees.  If faster for both effects together,  one would add about 0.035 gees.  The additions would be a bit over 3 times larger for the LOX tank,  as the L to its free surface is larger at something like 33.7 m.

Much more accurate dimensions masses,  and propellant-remaining percentages would be needed to get reliable results!  But these results obtained here do seem to crudely indicate what is going on during Starship/Superheavy hot staging.

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search code DDMMYYYY format      12092026

search keywords:  forensics, launch, space program

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