4/05/2018

"A long time ago in a galaxy far, far away...."


The Group of Atmospheric Science (GAS) is enthusiastically participating in this year’s Star Wars day (4th of May), a tribute established by the fans of the famous saga, which has hooked successive generations of public all around the world. This celebration offers a unique chance to highlight some of the Group’s projects, whose application was somehow advanced in the movie series, as well as to attempt an amusing assessment of how much of science, and how much of fiction can be appreciated in this “sci-fi” epic story.

HABIT and the farms of Tatooine, the two-starred planet

Probably one of the most known worlds that appear in Star Wars is Tatooine, the home planet of Luke Skywalker. It is depicted as a desert planet inhabited, among a varied fauna, by several anthropomorphic creatures, including human settlers (how the hell could people get that far?). These latter are devoted to raise crops by using water extracted from the atmosphere, such as HABIT (a scientific instrument design by GAS that will fly to Mars in 2020 with the next ESA's 2020 ExoMars mission), has been conceived to do. Although it is an instrument originally intended to study the water cycle on Mars, it will indeed collect water from the Martian atmosphere, posing the possibility to serve as the core of future water farms for supplying the crew of eventual manned missions, and the greenhouses they will have to mount for their living.

Luke Skywalker staring at double Tatooinian sunset from his farm.
Credits: Lucasfilm Ltd.

Bearing in mind that, in short, Tatooine appears as an Earth-like planet in terms of size (it can be inferred from the appreciated effect of gravity! on the characters), and provided with a comfortable and breathable atmosphere, HABIT goes further than the fictional systems used in this planet. It is meant to catch water from a faint and extremely dry atmosphere on a cold and far more arid and inhospitable world than Tatooine: Mars. The real expectancy of growing crops there thanks to the water harvested from the air by the instrument overcomes by large any prospect advanced in the movies.

The development of “water farms” is also posed as an application of HABIT in desert areas on Earth which match with the “Tatooinian” environment, where such facilities can contribute a great improvement in life conditions for their inhabitants.

The connection between HABIT and the water collectors in Tatooine has been highlighted several times in different media which have devoted articles to the instrument:

So we can say that HABIT is a truly science (-fiction) instrument. Maybe some of GAS researchers has “direct line” with George Lucas team?

Ionic engines
The Millenium Falcon escaping from Tatooine and a real ion thruster.
Credits: Lucasfilm Ltd/NASA/JPL.

The engines of the movies’ ships are reminiscent of the electric propulsion ones used in modern spacecrafts, which work by expelling an ion jet to generate impulse that can be perceived like a blue light similar to that emitted by the Millenium Falcon thrusters. Yet, the depicted capabilities of the cinematographic engines are far from what can be considered real or possible.

First, electric propulsion engines provide a rather weak thrust, which is only useful, for instance, to perform little attitude control manoeuvres, or to reboost satellites from time to time, since they are always pulled down by the gravity! But to reach their orbit, or to enter deep space in the case of interplanetary missions, spacecrafts need a far more powerful boost. Indeed, a rocket is nothing but a huge tank system, with incorporated thrusters, to drive the proper (and tiny by comparison) spacecraft up to the appropriate speed or orbit (in the case of satellites).

All around spacecrafts and satellites propulsion is crucial in nowadays space exploration. For that reason, GAS is leading this challenging field being part of cutting-edge new technologies projects as PVT-GAMERS (Pressure-Volume-Temperature Gauging Method for Electric Propulsion Systems). A team of Ph.D. students from Luleå University of Technology, supervised by Prof. Maria-Paz Zorzano, is developing a small size demonstrator for an improved gauging method to measure propellant content in spacecrafts’ tanks throughout their operational lifetime. This method will be validated on a parabolic flight within the prestigious ESA programme Fly Your Thesis!

Spacecrafts sent to the Moon or other planets escape from the gravitational! link with the Earth thanks to this enormous investment of energy and then, they continue to move in a constant direction and speed according to Newton’s first law. Those sent to Mars, for example, only make a few brief thrusts afterwards to correct their trajectory, and those sent to more distant planets in the outer Solar System, can take advantage of the gravitational! pull of others they can find along their way to accelerate for a while increasing their velocity.

EM drive prototype.
Credits: JPL.

But by no means are they propelled in a constant way like it happens in the case of Star Wars ships; it would be just impossible to carry the amount of propellant they would need to do that... unless the EM Drive (radio frequency -RF- resonant cavity thruster), a project in which GAS was involved by performing some related studies, is eventually developed.

This type of engine could provide a constant impulse, and hence a constant acceleration with no need of any propellant, allowing to reach very high velocities, but it is not clear by the time being that it is even physically possible.

As you see, space technology is always opening whole new science fields to explore and create knowledge, but also… amazing space opera film scripts.

Space and time

In Star Wars, our heroes travel the length and breadth of a whole galaxy with stunning ease, severely misguiding the understanding of cosmic distances, which is a kind of complicated matter because it overwhelms our perception scales, that are “calibrated” for our world around.

Let’s consider some few examples to put the issue in context:

A mean trip to Mars takes some 7 months on average, travelling at thousands of kilometres per hour (the probe New Horizon is so far the fastest spacecraft ever launched, with a velocity of 58.000 km/h currently); and it is only the planet next door! And the foreseen duration of the journey to Uranus for the proposed mission Uranus Pathfinder, if eventually launched, would be of more than 12 years (though it would include an initial visit to Venus, which is in the opposite direction with relation to Uranus itself).

With regard to interstellar journeys, we could resort to the Voyager 1 probe. It officially reached the limits of the Solar System in 2012, after almost 40 years marauding around. In its further journey, and although it is not going to anywhere in particular, it will past by a relatively close system (some 17 light years from here), around the star Gliese 445, what will take place within... 40.000 years! By the way, Voyager 1 is right now the second fastest spacecraft ever but, remember, this is not because the use of a continuous impulse; it will continue moving with constant speed and direction until some force acting on it changes them.

Mars Science Laboratory cruise stage bound to Mars.
Credits: NASA/JPL.

If we count on the aforementioned EM Drive engines, the acceleration provided could increase the speed of a spacecraft continuously, but not indefinitely. There is a limit for the maximum velocity an object can reach, as it can be cleared out from the famous expression by Einstein (E = m·c2). It shows that mass and energy are equivalent and, therefore, the increase of kinetic energy of the given object as it speeds up, equals an increase of its mass, what implies a bigger and bigger investment of thrusting energy to keep a constant acceleration.

In any case, and supposing the feasibility of travelling at the speed of light (what is just impossible for any object according to our current knowledge), it is worth to remind that our galaxy, the Milky Way, measures 18.000 light years (long axis) so, even at such a velocity, it would take 18.000 years to cross it from one side to another… mind-blowing! Isn’t it?

To say nothing about the time imbalance such circumstance would entail…if you enter the “hyperspace” in the Millenium Falcon, nothing would be the same once you are back to the start point eventually…


May the (gravity) force be with you

Gravity is an important force ruling the dynamics of the universe. It determines not only the celestial choreography of planets revolving around stars, but the existence of the stars themselves. The gravitational pressure within their core cause the fusion of atoms which keep them switched on. At a “local” level, gravity is the ultimate responsible for the rhythms of our planet (from days length to ocean tides pace), and everything we do must be exerted somehow against its effects. It is so connatural that, without it, we would be in trouble, as the astronauts who have spent long periods in the International Space Station know very well.

Nevertheless, this natural phenomenon, which stems from the interaction of matter with the structure of our universe itself, is absolutely omitted in Star Wars. This entails a severe decrease in the “sci” content of the movies (although that doesn’t detract from the saga not even an ounce of epic excitement, it must be admitted).

This radical disregard of gravity, which is constant throughout the whole series, gives place to some scenes bordering the absurd. The characters are under its influence even inside the ships while they are in the interstellar space and, regarding the way they move in every situation, it could be said that they are always submitted to an Earth-like gravity. On Mars, whose gravity is a thirty percent lower than Earth’s one, people will have some trouble to move around appropriately, to say nothing about the Moon, where everybody has watched how difficult is to move thanks to the Apollo missions videos (the gravity there is one sixth of ours).

It could be mentioned also the scence in which Han Solo, princess Leia and Chewbacca, after landing the Millenium Falcon on an asteroid, go out just wearing a kind of protective mask covering their noses and mouths. Not only the gravity keeps on being terrestrial, but the lack of pressure does not seem to pose any problem as it would indeed happen.

Gravity changes so much the performance of systems and humans that there are dedicated platforms, like the zero-g flights of ESA which are used in the FYT! student campaigns, only devoted to test for a short time the performance of small controlled experiments. We, at the GAS group, will participate this Autumn in one of these amazing zero-g campaigns! To our knowledge in the Star Wars saga, only Princess Leia knows what it is like to fly zero-g. Hopefully we will also be supported by “the Force” during our campaign.

The diversity of planets. A Universe Planet Encyclopaedia

Along the eight episodes filmed so far, they appear a large number of planets in Star Wars apart from Tatooine: Alderaan, Hoth, Bespin, Endor or Naboo, just to remember a few of them.

Some of the planets which appear in Star Wars and illustration of real ones. Credits: NASA/ESA

With respect to the issue of the gravity (again!) and the atmosphere in the vast majority of them, it must be asserted that they are nothing but earths with a certain intensified feature (mainly mean temperature, or amount of surface water). It must be admitted, however, that Star Wars advanced in a very visionary and anticipatory way the existence of exoplanets with the first movie (episode IV) in 1977, whereas the first confirmation of the existence of a real one, PSR1257+12b, by Aleksander Wolszczan, was announced in 1992, 15 years after!

Since then, some four thousand of new exoplanets have been detected and, though apart from the localization itself little more can be known about them, it is clear that their diversity overcomes that reflected in the movies. In addition to the basic and seemingly constant distinction between rocky and gaseous ones, they come in a wide range of sizes, wrapped by atmospheres with a varied composition which determine very difficult to imagine surface environments.

In our own Solar System you can find some illustrative examples, such as the thick atmosphere of Venus, warming the surface up to some 400º C on average and traversed by sulphuric acid clouds, or the cold nitrogen atmosphere of Titan, the largest moon of Saturn, in which methane acts as water on Earth (that is to say, it forms clouds which precipitates as rain, and flows over the surface as rivers, accumulating in lakes as well).

GAS has the exoplanet research among its main projects, aimed to the development of advanced methods for their spectroscopic study, in order to achieve a reliable method for their fine characterization. Samuel Konatham, PhD Candidate of GAS, exoplanet hunter and Star Wars fan, is on it finding the hottest and the coldest exoplanets as you can see in this graphics “hot off the press” from our laboratories, straight away, courtesy of Mr. Konatham:

Plots of the hottest and the coldest exoplanets found so far. Credits: Group of Atmospheric Science

The Star Wars saga is about to be finished with the last episode, which will be released (hopefully) next year, after having provided immensurable amounts of joy to its uncountable fans throughout decades. But science, and in particular exoplanetary exploration, promises to provide thrilling discoveries from now on which, as usual, will be probably far more amazing than any conceivable fiction. And GAS will be there to inspire all the audience around the world with more challenging Star Wars space science and sci-fiction fantastic technology to explore the Universe.

Because curiosity is the path to the bright side!

Special thanks to:
Javier Martín-Torres
Mª Paz Zorzano
Samuel Konatham
Álvaro Tomás Soria Salinas
Juan Antonio Ramírez Luque
Linda Alfredsson
And, of course, all the Star Wars past, present and future creators.