Dr. Suess on Trump

The illustration speaks for itself! 

-----  

Search code                                 15112025

Search keywords                        bad government,  idiocy in politics

-----   

Where Should the New Space Stations Be Located?

The International Space Station (ISS) is due to be retired and de-orbited sometime during 2030.  It replacements are very likely to be commercial stations.  The question arises:  in what orbit should these new space stations be located?

This is an important question,  because they will all be located in one or another low circular Earth orbit (LEO),  in order to stay out of the Van Allen Belt radiation (roughly about 900 miles = 1400 km up).  Plane changes in low circular Earth orbit are very costly to achieve,  in terms of rocket delta-velocity (dV) requirements. 

This is because the plane change dV requirement (direction only,  with no speed change) is dV = 2*V*sin(angle change/2).  At typical LEO speed (around 7.8 km/s),  a 10 degree plane change costs about dV = 1.36 km/s.  A 20 degree change costs 2.7 km/s.  A 30 degree plane change costs about 4.0 km/s.  It gets worse very quickly,  the bigger the plane change angle.

The “right” answer to this important question depends upon what you really intend to do with these new space stations.  If you want them to support human or robotic missions to the moon and planets,  the ISS orbit is just flat wrong,  and by a large amount! 

Such missions need to be flown from an orbit near the plane of the moon’s orbit,  or the planes of the orbits of the planets.  All the planes of the various planets’ orbits about the sun are rather close to the plane of the Earth’s orbit about the sun,  called the “ecliptic plane”.  This situation is illustrated in the figure.

All these possible destinations do not require large plane changes,  if mounted from Earth orbits inclined somewhere close to a band between the Earth’s equatorial plane and the ecliptic plane,  a band that also contains the orbit of the moon about the Earth. 

The plane of the ISS is at 55 degrees inclination to the Earth’s equator,  set there to enable easy access for the Russians from launch sites in Russia.  That’s a 60+ degree plane change to go elsewhere,  at least dV = 7.8 km/s!  Earth surface escape is only 11 km/s!

That high ISS inclination is just plain wrong for easy access to the moon or planets.  It always was.  An equatorial orbit about the Earth has the very lowest velocity requirements to reach from an equatorial launch site,  but all the orbits in the equatorial-to-ecliptic band are fairly easy to reach,  from pretty much any launch site in the US.

So,  if you really want these future space stations to actually successfully support future missions to the moon and planets,  manned or robotic,  you want them to be in this band of low-inclination orbits about the Earth.  Simple as that!

What might such mission support be?  Well,  perhaps assembly by docking together a lunar or interplanetary craft,  at a space station using remote manipulator arms,  from components sent up from Earth.  This is an approach well documented by the experience of building the ISS from the Space Shuttle with its arm,  and by the experience ever since of using the ISS arm to dock supply and crew vehicles.

These lunar or interplanetary craft could be fueled for their missions,  using propellants previously sent up by tanker vehicles from Earth,  and kept in tanks at the space station for such a purpose.  We would need a way to load and unload cryogenic propellants for this job,  since many such craft will need them.  So far,  only room temperature storable propellants have been transferred in weightlessness,  using expulsion bladders inside the tanks.  You cannot do that with cryogenics!  No materials have the necessary very large elongation capabilities,  at such low temperatures!

SpaceX wants to do this tanker vehicle transfer with cryogenic oxygen and methane in their “Starship” soon,  using ullage thrust.  That approach does alter the orbit,  something not tolerable when operating at a space station. 

But there might be an easy way to do that cryogenic transfer job,  without spinning huge vehicles,  or without applying any ullage thrust that alters their orbits.  See the article “Tank Design for Easy Cryogenic Transfers In Weightlessness”,  posted 26 July 2025 to this site (search code: 26072025,  search keyword:  space program).  As the article indicates,  this concept is undergoing the patent process.  A patent is pending.

You turn the system on,  wait several seconds,  then start the propellant transfer pump.  No ullage thrust gets applied,  and no vehicles or space station are spun up.  There are no unwanted forces at the tank mountings,  applied to anything!

The notion of elliptic departure and capture was explored in the posting “Elliptic Capture”,  dated 1 October 2024 this site.  The notion of space tug assist was first explored in the article “Tug-Assisted Arrivals and Departures”,  dated 1 December 2024 this site.  The search codes for those articles are 01102024 and 01122024,  respectively.  Both share the search keyword “space program”.

This selection of proper space station orbits,  an effective cryogenic propellant transfer tank,  the notion of elliptic orbit departure and arrival,  and a reusable space tug stage,  together make possible a space program of cost effectiveness that dwarfs anything ever seen before!  And THOSE FOUR THINGS are what really needs to happen!

-----  

Search code DDMMYYYY                     11112025

Search keyword                                         space program

-----  

 

Get Acquainted Info: High Speed Vehicles

This article is for people who know little about high speed flight vehicles.  It gets across some key concepts about:

#1. frontal thrust density and top speed capabilities, 

#2. how the same inlet components are used quite differently in ramjet versus turbojet installations, 

#3. why achieving combined cycle engine designs can be so difficult,  and

#4.  how heat protection is the true driving issue for high-supersonic and hypersonic flight.

There are other articles posted here and available elsewhere,  that go into considerably more detail about these topics.  But this one tries to illustrate the basics,  to get started.

-----  

Get Acquainted Info: High Speed Vehicles  

There are many concepts to understand about high-speed flight.  Frontal thrust density is a very important issue.  And,  there is no “magic” to waveriders.  See these 2 illustrations:

 

The number of propulsion nozzles at the back of a vehicle also seriously affects frontal thrust density.  This applies to both rockets and airbreathers (of any type).  See:

The over-simplified behavior of inlets on a supersonic ramjet vehicle is shown: 

 Bear in mind that pitot-normal shock inlets,  which have no shock-on-lip behavior,  actually have 6 behaviors to understand,  and external-compression feature-fitted inlets have 9 different behaviors to understand.   You do not initially need to understand all that detail!

But,  it is the basic as-illustrated inlet behavior above,  that drives supersonic ramjet performance.  Ramjet takeover from the booster needs to occur no lower than shock-on-lip speed.  The lower the shock-on-lip speed is,  the smaller the booster can be,  leaving more room for ramjet fuel and the nonpropulsive items.  Considerably higher speed is still efficient:

For supersonic flight,  gas turbine engine installations use the same supersonic inlet components,  but they use them quite differently!  These are usually low-bypass “turbojets”,  and they are usually fitted with afterburners. 

Unlike the ramjet,  which when operating properly,  accepts a fixed scooped air massflow from the inlet,  the turbojet demands a variable air massflow corresponding to its rotor speed(s),  determined in turn by the throttle control setting.  The turbojet inlet has to vary the captured air massflow to match engine demand,  which inherently requires subcritical inlet operation,  with variable-but-significant amounts of spillage around the cowl lip. 

The dominant pressure-rise feature in a turbojet installation is the compressor,  not the inlet!  (The only pressure rise feature in a ramjet is the inlet.)  See:

High speed flight involves lots of aero-heating.  Adjacent and captured air temperatures are high.  As you go hypersonic,  shock impingements multiply heating rates substantially.  See:

Shown just below are the heating rates to,  from,  and within,  any given piece of exposed material.  There is steady-state equilibrium (applicable to hypersonic cruise),  and there is transient behavior (applicable to atmospheric entry),  to worry about. 

Radiation occurs only when there is a view of something hot or cold from the affected surface.  The emissivity “e” can make radiative transfer either inefficient if low,  or efficient if high.  It varies between 0 and 1.  (The sigma represents Boltzmann’s constant.)

For convective transfer,  heating rates can be to,  or from,  the surface.  The “film coefficient” h is larger near stagnation zones,  and smaller on lateral skins.  The values of h all decrease as the air thins drastically at very high altitudes. 

Thermal conduction can be to,  from,  or within the piece.  The conduction within acts to set the temperature distribution of the piece from one end to the other.  The other two determine how much heat enters or leaves the piece.  See:

It should now be obvious that the main enabling factor for high supersonic,  or especially hypersonic,  flight is really thermal management,  more so even than propulsion.

And “scramjet propulsion”,  whether combined-cycle or not,   does not make your job any easier,  because it is geometrically incompatible with ramjet and gas turbine,  including even most of the inlet.  In fact,  combining any of these propulsive cycles,  including rocket,  is difficult at best,  because of the severe geometric incompatibilities,  not to mention the speed-of-application differences.  See:

The two that do combine well are rocket and ramjet,  for the “integral rocket ramjet” (IRR):

-----  

For posting on “exrocketman”

Search code DDMMYYYY:                                   02112025

Search keywords:                                                    aerothermo,  airplanes,  ramjet

-----