Categoria: supersonic

Propulsion principles

During Eighties the modern aerospace principles were set. Before they were still the same defined by the ancient Chinese, since the black powder discovery. All of these principle rely on a single, consolidated, sacrosanct dynamic law: the reactive force..

Based on these principle we arrived, somehow to atmospheric supersonic propulsion and satellites send here and there in our solar system (and beyond).

Still during Eighties, the Russian engineer Tsiolkowsky (which, by the way was the same to define the propulsion principles actually allowing us to fly still today) defined the 15 steps required for the “cosmonaut development program”:

  • Arranged rocket for flight training on it.
  • Subsequent aircraft wings are reduced, speed increase.
  • Penetrate very close atmosphere.
  • Flights above the atmosphere and low-gravity planning.
  • Create satellites that return to Earth after the flight.
  • Satellites are settled around the Earth, but can come back to Earth.
  • Provide breathing and feeding cosmonauts by plants.
  • Landing modules, satellites for broadcasting and connection.
  • Widely used greenhouses to ensure the independence of man from the Earth.
  • Arranging of extensive settlements around the Earth.
  • Use solar energy, not only for a comfortable life, but also to move through the solar system (Solar sails).
  • Founded the colony in the asteroid belt and other places of the solar system.
  • Develop and expand the number of space colonies.
  • The population of the Solar system is multiplied. Settling around the Milky Way starts.
  • Sun is cooling down. Mankind is removed to other Suns.

As usual below my humble, free and lovely useless comments:

  • Done. The concept of flight training is now a sort of video gaming…
  • Done. Two or more wings planes are not common any more and supersonic planes have relatively reduced wings
  • Done. Almost at any altitude and also with or without planes…
  • Done. Should I mention any manned low Earth orbit mission?
  • Done. Should I mention the space shuttle?
  • Done. Should I mention the MIR, Space Station or the Tiangong?
  • Almost done. We are working on it. Astronauts do not yet eat plants, but they cultivated them in space.
  • Done. Done. Done. Extensively.
  • Not done. Actually from now our achievements did’t reach yet the Tsiolkowsky’s targets. We are still far from reaching any of the following points and even working on them, with our current propulsion principles knowledge, it seems unrealistic to target all of them.

Let’s say that we have rather good chances of setting up space colonies and use solar sails, but I’m rather skeptical that we have any other option (at the moment?) than staying around our Sun. The last two points, in particular, do not seem to me (only?) actually feasible within a human being lifetime (… unless we reach such evolution stages).

I can not avoid, however, to note how accurate the Tsiolkowsky predictions were until today (I’m talking about someone which was able to tell these stuffs in a century when noting man-made wasn’t moving above our heads), thus I should at least assume that he can not be completely wrong regarding what will happen in future.

This is the only reason motivating me to leave a glimmer in believing in propulsion systems other than action-reaction (here I should list a rather long list of potential/Iwanttobelieve/flyingsaucer/bullshit/semi-bullshit ideas and technologies).



Kantrowitz limit

A.R. Kantrowitz era un arzillo vecchietto (non che sia sempre stato vecchio, ma è deceduto alla veneranda età di 95 anni “calcando le scene” fino alla fine) americano. Fisico ed inventore di questo e di quello.

Tanto per intenderci è stato uno dei primi (se non il primo) a proporre il concetto di propulsione laser per mandare carichi in orbita “sparando” fasci laser da terra. Fu uno dei pionieri e più grandi contributori in diversi campi, tipo meccanica dei fluidi, gasdinamica, magnetoidrodinamica, e via dicendo.

Ora, a parte riconoscere la genialità di Mr. Kantrowitz, mi ci sono imbattuto specialmente cercando di capire il concetto di “Limite di Kantrowitz“.

Prendiamo un condotto connesso ad una sorgente di vuoto. Il flusso di aria (mentre viene aspirata dalla pompa a vuoto) in tale condotto (assumendo un flusso di massa pari alla velocità di ingresso) aumenta man mano di velocità fino ad avvicinarsi a condizioni “di bloccaggio” in cui non si può superare la velocità locale del suono. Riducendo ulteriormente la pressione nel tubo la velocità del flusso non può aumentare, non potendo oltrepassare la velocità locale del suono. Questo il famoso limite di Kantrowitz che in sostanza blocca la velocità del flusso indipendentemente dall’ulteriore calo di pressione. Ovviamente un motore a getto (quelli degli aerei che fanno rumore senza eliche) deve accettare tale limite e non può spingere un flusso oltre Mach 1 al suo interno indipendentemente dall’aspirazione che il compressore è in grado di creare.

Tutto ciò è fantastico (e forse anche un po’ complesso). E la soluzione è sempre stata: stare sotto (o sopra nel caso di flussi che nascono già ipersonici) il fatidico limite. Un recente sistema di trasporto che promette faville (e dai che si capisce e comunque ne ho già sproloquiato almeno qui) propone però un’altra soluzione. La quale, nonostante i miei dubbi sull’intero sistema, devo riconoscere è geniale. Mettiamo un compressore sul muso della capsula (la quale viaggia a folle velocità nel tubo quasi-sottovuoto) che prende l’aria compressa dal davanti e la butta dietro per produrre anche spinta. Così rimaniamo sempre ben al disotto del limite di Kantrowitz e beneficiamo anche della compressione che noi stressi creiamo nel tubo muovendoci (ovviamente ci serve un metodo per partire, ma questa è un’altra storia).

In pratica sarebbe come mettersi dentro una grande siringa che aspira dal davanti per spingere il pistone dal dietro. Il tutto ad oltre 1000 km/h.


Supersonic gull dream

Is it clear that I’m obsessed with the problem (the dream) of having supersonic commercial flights?

I have never been on a Concorde and I have my (strange and wrong) ideas that it was a colossal hoax, but nonetheless it is so fascinating to think about supersonic transfers…

We already discussed (here and here, for instance) that one of the main issues of such a concept is the noise (the sonic boom).

The Supersonic Aerospace International (SAI) developed a very nice concept (only a concept…) for a potentially boomless supersonic aircraft (with a sonic boom claimed to be 1/100 that of the Concorde). The design is based on a “curved gull-wing, an inverted V-tail, and a curvilinear fuselage”.

SAI Quiet Supersonic Transport

WOW. But…

The test flight was planned for the 2011 and the first passengers would have been in 2013. Nothing happen and (both for the business jet-sized Quiet Supersonic Transport (QSST) and for the large-scale plan of having commercial 737-sized transport aircraft) SAI seems having some investors lack and probably any further progress is unlikely.

At the present the QSST development plan (declared both for commercial and military use; the second application is what makes me a bit more confident about the project) considers a test flight in 2017 and passengers in 2018 (and 80 million dollar per aircraft expected).

What a pity (?)


PS. Do you know who is the funder of SAI? Michael Paulson, son of Gulfstream Aerospace founder Allen Paulson

Skreemr from London to New York

Matter of half an hour!

I came back once more (after here, for instance) talking about the “new era of commercial flights”. I’m talking (of course) about supersonic intercontinental commercial jets!

The new player is this time the Skreemr. A scramjet launched from a magnetic gun (a pair of conductive parallel rails and accelerated by means of a strong electromagnetic field) starting at Mach 4 speed and reaching up to Mach 10 (5 times faster than the Concorde).

Two rockets, burning liquid-oxygen and kerosene, would help the magnetic gun to boost the scramjet at Mach 4. Liquid oxygen thus needs to be stored on board, but once reached Mach 4 the scramjet engine would fire up, and then the jet could reach up to 10 times the speed of sound by using just the air oxygen to combust hydrogen fuel

As usual for the time being the most notably results of the projects are some concept renderings.


It comes by itself that the technological barriers are so huge to make the idea a real near-term challenge: materials able to withstand the heat caused by acceleration, the handling of such accelerations on the passengers, craft noise, the engine itself (actually scramjets are under development for military purposes, but nothing is at the moment real about commercial applciations), and so on.

But the Skreemr is perfectly on the race. Airbus patented a new concept for the Concorde-2 (again the Concorde?!?!) and we already talked about the Musk Hyperloop concept here (and here it seems that the test track construction should start soon).

As in almost any race the winner is the faster. Competition is open (although after decades of studies probably the most promising technologies should have been already identified).


PS @ 11.11.15. Just few more words on the concept of magnetic gun since I recently attended to the presentation of the poster below.


Ok, we already known that military were working on this, that it is a valid alternative for launching missiles and projectiles and I do not want to deepen here the physics behind; but do you know what really surprised me?

Look at the table: “Launch acceleration: 30kGees”! Do you know what it means? That if you put on a mass of 1 kg, it has to support 30000 kg during the launch (few seconds)!! Well, keep in mind that whatever it has to be launched has to be sturdy enough!

And in the poster the approach is proposed for launching spacecrafts… at least people wouldn’t have to support such an acceleration.

New York – San Francisco: 30 min, 20 $

Let me start with a simple, clear, obvious statement: “I’m not used to read Forbes”. Nonetheless, as usual, Mr. Internet led me here and there and in this case to Forbes (here, dated 02.03.15 [some unnecessary but irresistible pills of numerology: the product of the first two digits gives the sum of other two]).

It is at leat 3 years that on the web I spot the Hyperloop concept. Thanks to the paySpaceXpal-man Elon Musk that (the power of money…) dusted the concept off. In brief the Hyperloop is a concept for a high-speed transportation system based on reduced-pressure tubes where pressurized capsules move thanks to air compressors and linear induced motors (here the wiki explanation). What am I talking about? The strange missile here below.


The concept dates back to the 1812 when George Medhurst proposed the idea of air-powered capsules in vacuum tubes in his paper “Calculations and Remarks Tending to Prove the Practicality, Effects and Advantages of a Plan for the Rapid Conveyance of Goods and Passengers Upon An Iron Road Through a Tube of 30 Feet in Area, of the Power and Velocity of Air” (not short, but for sure well explaining title). In 2012 Elon launched his (?!) idea of hyper-fast transportation system that himself defined as a “cross between a Concorde, a railgun and an air hockey table”. Sounds a bit science fiction, but probably times are getting mature and mature (200 hundred years of tech-evolution are not enough, but a good step forward).

The idea bounced around for decades (including Mr. Goddard papers in 1910 and Mr. Heinlain in 9156 mentioning “vacutubes” in Double Star) and in 2000s Swissmetro studied the idea concluding that it was not feasible, not economically feasible. Enough easy from a technical point of view (on the paper), enough expansive to let its economical feasibility still object of debate. 6-7.5 billions dollar, the price tag declared by Musk is considered too low, 100 billions seem more realistic (!).

Forbes begins stating that “Hyperloop is real” and it is partially true. A bundle of venture capitalist, billionaire and former White House deputy put together Hyperloop, a company boding of realizing the Hyperloop concept. Actually they intend to develop before the cargo version and only after the human transportation. Besides Hyperloop it exists, with a very similar name, also the HTT (Hyperloop Transportation Technologies), a research company crowdsourced born (and now hiring about 200 eng working in exchange of stock options; that’s business!) with the same aim: develop the Hyperloop concept. Also Musk itself revealed a plan for funding a test track in Texas with scaled-down capsules, and on June the 23rd 2015 I read here that more than 700 people signed for helping Musk for building its Hyperloop prototype. 3 teams working on the concept (I mean, paid for working on this!).

For me, and the children like me, it is fascinating thinking how Hypoerloop may change the world (boats? old dinosaur. goods transportation? matter for almost-real-time delivery!). Hyperloop can go over and under lands, through the oceans and so on (for the first line proposed by Musk the tubes should go parallel to Interstate 5) and actually overcomes two of the major impediments to rapid travel: air drag and friction. I personally belive (and who cares…) that our concept of transportation system should be deeply revisited (not jut increase the car efficiency of build larger/faster planes) and actually Hyperloop sounds to me a good compromise between science fiction and future reality.

In 2015, New York – San Francisco: 360 min (direct flight), 400 € (as a minimum). Keep on dreaming (and Musk investing).


PS. Let me just point out the image below, taken from the Musk white paper, which compares the MJ (energy) for passenger along the journey Los Angeles – San Francisco.


Obviously (!) the Hyperloop technology is the absolute minimum (and the same would be also comparing times), but:

  • strange that the second best choice is still another Musk creation, the Tesla Model S fully electric car…
  • among “old technologies” cars, with 2 passengers, remain the less energetic options (although we see a lot of one-man-cars). Too energy-consuming airplanes, sounds like useless tech development…
  • Hyperloop has 20 $ estimated for something around 50 MJ, i.e. 0.4 $/MJ. The same cost of a flight connection (about 400$ for 1000 MJ)…