Elon Musk's recent stunt to launch a red Tesla Roadster towards Mars, with a lot of pilot in astronaut suit in the driver's seat, brought to light a technological theme initially developed in the 1960s, during the Apollo missions. We are talking about the super heavy launchers that is, those rockets that allow to carry at least 50 tons of weight in low Earth orbit (between 160 and 2000 km of altitude).

In astronautics they are called vectors (or launchers) those designed missiles, and used, to send a certain “payload” into space. Depending on the payload (payload in English) they are classified into light throwers (up to 2t), medi (and 2 the 20t), heavy (and 20 a 50t) and super heavy (more than 50t) [1]. Throughout history, very few rockets have been capable of carrying a payload of this magnitude into orbit. The undisputed record (140t) is still up to today Saturn V, the vector that allowed man to reach the Moon (fig.1). Quoting Oriana Fallaci: “A man, placed next to that rocket, it looks less like an ant. It is such a gigantic rocket that its height is equivalent to that of a skyscraper with thirty-six floors, its size is that of a room measuring seven by seven metres. […] If you reach the top with an elevator, I did it, terror grips you. And you don't realize this on television […] you lack terms of comparison…” [2].

Fifty years later, around Falcon Heavy, missile designed by SpaceX, Tesla owner's space company, it must keep its creator's promise, that is, to become the greatest launcher since Wernher von Brown's legendary rocket, with lots of recyclable engines.

Fig.1 – Comparison of some super-heavy throwers

However, many will continue to wonder what the point of sending a sports car into space was. Considered i previous disasters by SpaceX, the first Falcon Heavy launch was at high risk of failure. At the same time it was necessary to carry out tests to understand whether the carrier will be able to, one tomorrow, carry the declared 63.8t of payload [3]. To avoid endangering objects of scientific value, such as million-dollar satellites, Elon Musk has chosen to use his personal "small car" as a test weight [4]. This move has also been widely criticized as a mere publicity stunt, However, it is no secret that the public's affection for astronautics enjoys ups and downs. For example, once the space race against the USSR was won, the Americans stopped following space missions. The cosmic Tesla has certainly awakened everyone's interest.

But what will happen to the car and its driver??

While, according to Musk, they will continue to float in space for the next few billion of years [4], many scholars think differently. A very recent study published by the Canadians Hanno Rein and Daniel Tamayo and the Czech David Vokrouhlicky aims to evaluate the probability of impact of the Tesla with the celestial bodies of the inner solar system. The title of the work "The random walk of cars and their collision probabilities with planets (The random motion of machines and their probability of collision with planets)” [5] It's somewhere between serious and facetious, as indeed is everything relating to this undertaking. In their work, based on serious mathematical models, the researchers carried out multi-body simulations covering a time span of several million years. Assuming the car was launched from Earth and is headed today, without further course corrections, towards the orbit of Mars it is highly probable that, in the future, There will be many close encounters between Tesla and our planet (fig.2). While the probability of impact of an object crossing Earth's orbit can be precisely estimated on a time scale comparable to human life, The Roadster's chaotic orbit cannot be precisely defined as to how long the many encounters will take. Then, conclusions can only be drawn in statistical terms. From this point of view, Tesla's behavior has many similarities with near-Earth asteroids (close to Earth) o NEAs. They move in the internal region of the solar system in a chaotic manner, carrying out numerous close encounters with terrestrial-type planets, which heavily and unpredictably disturb its orbit. The most common fate of this type of asteroid is to crash into the Sun. Only a small percentage of them wander long enough in the area of ​​terrestrial planets to have a non-zero probability of impact with the Earth, Venus or Mars. On the other hand, there are also differences between the Tesla and the NEAs. The first is the fact that asteroids typically spread into the solar system from the asteroid belt., while the Tesla was launched from Earth. The second is the fact that the car did not perceive the gravitational resonance effect with Jupiter, which happens for NEAs. In any case, it is quite certain that the first close encounter with Earth will take place in 2091 and in most of the simulated cases no impact is expected for the subsequent ones 3 millions of years. This doesn't mean that the chances of collision are null, and also define the maximum time with which the material must degrade 1 million years is in fact estimated a probability of impact of 6% with the Earth and del 2.5% with Venus. This leads to the assessment that the Tesla journey in space cannot last more than a few tens of millions of years, as in the case of near-Earth asteroids.

Fig.2 – Orbit of Tesla in the inner solar system [6]

Musk's car is likely to last that long?

Several sites reported an interview [7][8] to a plastics expert at Indiana University, he dr.. William Carroll, that in the 2005 he was president of the American Chemical Society. According to Carroll, between cosmic radiation and micrometeorite impacts, the life expectancy of the materials that make up the vehicle can be, in some cases, even just one year. We are referring to everything that is plastic: on Earth, cosmic rays and the solar wind are attenuated by the atmosphere and the magnetosphere, but in a vacuum it is not so. In extreme conditions, organic polymers risk crumbling in a few months. All the rest, instead, could be destroyed by micrometeorites, that is, very small pieces of rock that are extremely common in space. Suffice it to say that the amount of cosmic dust that is assumed to fall on Earth every day is a few tens of tons. These "pebbles" travel at very high relative speeds and, despite their small mass, They are capable of doing considerable damage. Therefore we must imagine that in the next few centuries the body of the Tesla and its occupant will be reduced to a sieve (promptly baptized Starman, from David Bowie's song) in ashes.

And to conclude, what Starman took with him on his perilous journey to Mars and the asteroid belt? It appears that there is a copy of the in the glove compartment Hitchhiker's Guide to the Galaxy by Douglas Adams and the entire trilogy of Foundation of Isaac Asimov (in 5D optical support). The inevitable towel and the words “Don't Panic (Don't Panic)” (other references to Douglas Adams) they couldn't miss it, as well as a tag that reads “Made on Earth by humans (Made on Earth by humans)”.

In a vacuum it will not be possible to hear “Space Oddity” from the Tesla speakers, but to see her travel like this, against the black background of the cosmos, should be enough for anyone to imagine that it is a "space freak".

 

[UMM]

 

Bibliography:

[1] NASA Launch Propulsion Systems Technology Area Roadmap, TA01-7

https://www.nasa.gov/pdf/500393main_TA01-LaunchPropulsion-DRAFT-Nov2010-A.pdf

[2] Oriana Fallaci – That day on the moon – Rizzoli (1970)

[3] Falcon Heavy Overview from SpaceX website

http://www.spacex.com/falcon-heavy#falconHeavy_overview

[4] Elon Musk's tweet: “Payload will be my midnight cherry Tesla Roadster playing Space Oddity. Destination is Mars orbit. Will be in deep space for a billion years or so if it doesn’t blow up on ascent. 1 dic 2017” / The cargo will be my cherry colored Tesla Roadster [with the car radio] that sends “Space Oddity”. The destination is the orbit of Mars. We will be in deep space for a billion years or so, always that [the rocket] does not explode on takeoff.

https://twitter.com/elonmusk/status/936782477502246912

[5] They have Rein, Daniel Tamayo, David Vokrouhlick – The random walk of cars and their collision probabilities with planets

https://arxiv.org/abs/1802.04718

[6] http://www.whereisroadster.com/

[7] https://www.livescience.com/61680-will-spacex-roadster-survive-in-space.html

[8] https://www.wired.it/scienza/spazio/2018/02/17/tesla-starman-spazio-musk/