"You want to wake up in the morning and think the future is going to be great - and that’s
what being a spacefaring civilization is all about. It’s about believing in the future and
thinking that the future will be better than the past. And I can’t think of anything more exciting
than going out there and being among the stars." With this sentence Elon Musk, the founder of
SpaceX, has expressed his idea of colonizing Mars within a few years,
but there is still a long way to go, as evidenced by the latest launch of the SN8 prototype
of the Starship spacecraft, which took place on Wednesday 9th December 2020 from the Cameron
County base in Boca Chica, located approximately 32 km (20 miles) east of Brownsville, Texas.
This test had multiple objectives, as evidenced by various tweets posted by Elon Musk recently:
- successfully take off from the Boca Chica launch pad powered by three Raptor engines
- reach an altitude of 12.5 km - carry out the "backflip" maneuver, that is,
lose the vertical attitude in a controlled manner, turn off the Raptors and position
yourself in a planed attitude with aerodynamic control of the fins and auxiliary rocket system
- recover the vertical structure - turn on the Raptor engines and
compensate until the horizontal movement induced by gliding flight is canceled
- return to the landing area - land on the prepared pitch
Of these points, only the last one was probably missed
(also given the greenish color of the flame) due to a problem with the supply of propellants.
Musk confirmed this hypothesis, revealing via Twitter a low pressure problem in the fuel tank
(the one in the "nose" of the prototype).
Thanks to filming taken from other angles, it will probably be possible
to better analyze how the apical moment of the flight was managed,
i.e. when it seemed that the shutdown of two of the three Raptors had been programmed to
manage a hovering phase, probably useful for preparing the best backflip maneuver.
SN8 landed too hard and exploded, but the point is, it landed exactly on the landing pad. This
testifies to SpaceX's already advanced ability to control the flight of a completely new rocket,
which has indeed inherited the experience gained with control software from the veteran Falcon 9,
but which has a completely new and innovative horizontal flight phase.
It is also unclear whether the three Raptors
performed as expected in the final stages of the descent,
which took place with only one Raptor running and ended with a RUD (Rapid unscheduled disassembly).
In any case, despite the pyrotechnic conclusion, the one reached today by SpaceX remains a first,
historic success: few would have expected that already on the first flight of a prototype
so many milestones would have been achieved, despite Elon Musk himself having estimated
only a probability around 30% of a test success,
and that the same prototype was able to fly for approximately 6 minutes and 40 s.
In fact, it should be immediately clarified that what we have been able to witness is a landing
technique never experienced before by a launcher, which moreover has seen a series of subsystems in
operation until now tested only individually or in static form. The data collected during
this test will still be invaluable in making the necessary improvements on subsequent prototypes.
SN8 is now destroyed, but in Boca Chica the work on the prototypes continues uninterrupted,
and have already reached the production stages of the SN15. The SN9 prototype now appears
practically ready, and we are sure that within a few weeks we will be able to witness
a new attempt at “jump”, which we hope will be crowned with full success.
The very reason why SpaceX is assembling all these prototypes is precisely because they expect to
break many of them, in an iterative process where technical improvements and refinements
will be made on the Starships as the experimentation continues.
Now let's try to tell some more details about the Starship.
First of all, let's clarify the name. Starship is the name used to indicate the whole system
(spacecraft plus rocket), although strictly speaking it would refer only to the spacecraft
mounted on top of the rocket, which in the future, if the tests continue without problems,
will be destined for the transport of a human crew. The actual rocket, which contains the Raptor
main engines, is called Superheavy. In the rest of the video this distinction will be maintained,
talking about Superheavy for the rocket and Starship for the spacecraft.
The system made by Starship and Superheavy rocket is the first space transport system designed to
be completely reusable: this means that, after the space mission, both the Starship and the
Superheavy return to Earth, are overhauled and refueled to be ready for a new flight. Potentially
within 2 or 3 days. Even Elon Musk thought of making landings so precise that he could drop
the Superheavy directly onto the launch pad, to optimize the time between two successive flights.
The size and power of Starship and Superheavy considered together will be even greater than that
of Saturn V, the mythical rocket that transported astronauts to the Moon in 1969: the internal
volume is greater than 1000 m3, in other words it would comfortably fit 50 - 60 people , perhaps 100
a little narrower: such a large volume would allow the launch of entire constellations of satellites,
or the launch to the Moon and its reuse as a lunar base. Overall, it will be 9 m wide and
between 100 and 120 m high (just to give an idea, it will be higher than the Statue of Liberty),
depending on the type of Starship spacecraft that will be used. There are in fact different versions
of the Starship, which will have different characteristics depending on their intended use:
- Crew, to transport astronauts in low earth orbit, ie an earth orbit between
the atmosphere and the van Allen belts, ie between 300 and 1000 km of altitude;
- Lunar, for manned lunar missions: since there is no return to Earth, because astronauts would
use another spacecraft such as NASA's Orion capsule to come back to our planet,
this version of the Starship does not need to have all the aerodynamic surfaces
(such as flaps and ailerons) to control the re-entry phase into the atmosphere.
This translates into lower weight with consequent lower fuel savings;
- Tanker, a sort of spacecraft - tank for refueling in orbit:
one of the major innovations introduced by SpaceX
is the possibility of refueling in orbit, by attaching the Starship to the Tanker spacecraft;
- Cargo: version of the Starship capable
of carrying loads such as large satellites or space telescopes;
- Deep space: used for missions to Pluto and beyond.
- Point to point transfer on Earth:
this version of the Starship would allow travel from one point to another on Earth: from London
to New York it would take just half an hour, while from London to Sydney just under an hour.
The Starship spacecraft will have a low Earth orbit carrying capacity of approximately 100 tons.
By itself it will be 50m high and 9 m wide,
and will be able to carry 1200 tons of fuel. It has six Raptor engines, three for use on Earth
and three for operation in space, where there is no atmosphere.
The Superheavy rocket, 70 m high and 9 m wide and made of a special stainless steel specially
developed by SpaceX for its spacecraft, has a ground mass of about 3 million kg.
It can carry 3400 tons of propellant (liquid methane and liquid oxygen).
In the standard configuration it will have 28 Raptor engines, but in reality their number is
customizable according to needs. In addition, SpaceX has developed a particular technology
that involves reusing the combustion gases produced by the engines
to increase their thrust. Upon returning to the ground, he lands on six metal legs.
Both the Superheavy and the Starship, upon returning, are subjected to very
high temperatures, of the order of 3200 ° C: to withstand these extreme temperatures
SpaceX has preferred to use steel instead of composite materials, because it is less expensive
and easier to work and more resistent. The same special steel alloy will be used by cybertrucks,
vehicles that according to Musk’s idea should be used by astronauts to travel to Mars.
To land on Mars, the idea was to exploit the friction with the Martian atmosphere
to decrease the speed of the Starship, which will cross the upper layers of the martian
atmosphere at a speed of 7.5 km per second: the spacecraft will be equipped with a heat shield
composed of tiles a little along the lines of those of the Space Shuttle,
which will be partially consumed by friction with the Martian atmosphere.
Elon Musk also claims that to build a city capable of supporting a local population on Mars it will
take about 1,000 Starship spacecraft but up to 20 years due to the planetary Earth-Mars alignment,
because to send the Starships and transport goods, infrastructure and crew on Mars
it will be necessary to wait for the launch windows to open, that is, those periods in
which Mars or another celestial body is at the point of its orbit closest to the Earth.
In the case of Mars, the launch window opens approximately every two years.
As with the Falcon rockets, the Starship spacecraft design aims to maximize reuse.
Musk said that, ideally, a Starship can fly up to three times a day, for a total of more than
1,000 flights per year per spacecraft. Which means that if SpaceX builds as many Starships as there
are currently Falcon rockets (about 100), knowing that they can carry up to 100 tons each, then on
an annual basis, SpaceX will be able to launch upwards of 10 million. tons in orbit per year.
Musk pointed out that when you take into account all the spacecraft currently in
operation - and with Falcon rockets making up about half of them - the total payload
capacity is just 500 tons per year. The possibility of three flights a
day by the Starships, can be confusing, but it is not certain that these will be used
for the final journey to Mars. Especially for the construction of a self-sufficient city,
it is much more likely that the Starships will serve as transport ships for orbital
ports ready to supply other spacecraft that will shuttle between Earth and Mars.
Also in Musk's intentions, each Starship flight would cost only $ 2 million,
which is the sum of all the coffees drunk in a day by the inhabitants of Houston,
assuming that each Houstonian drinks only one coffee a day.
But how to build a city on Mars? According to him, for people to survive on the Red Planet,
"glass domes" will initially be needed. Then move on to "terraforming", which would allow
life to be sustained just like on Earth. It is an artificial process that makes it possible to
make a planet habitable by intervening on the atmosphere and thus creating an oxygen reserve
as well as fertile soil. Obviously we do not yet have the necessary technologies - some say we will
never have them - and some users have pointed this out to them: "Terraforming will be too slow to be
relevant in our lives. However, we can establish a human basis there. At least one future space
civilization - discovering our ruins - will be impressed that humans have come this far. '
Why does Elon Musk want to take astronauts to Mars? Because it is a planet quite similar to
the Earth: it is a rocky planet, and it takes just over a day (24 hours, 37 minutes and 23 s
compared to 23 hours 56 minutes for the Earth) to make a rotation around its axis. Furthermore,
the inclination of its axis of rotation with respect to the plane of the orbit
is equal to 25.19 degrees (for the Earth it is about 23 degrees). Mars also has two polar caps,
however, formed by dry ice, that is, ice originating from carbon dioxide;
depending on the season the size of the polar caps increases or decreases. Furthermore,
in 2015 the existence of liquid water was also confirmed.
Who knows if, thanks to SpaceX's Starship, our now sci-fi dream of going to Mars will come true ...