Moon, Mars and beyond: the present and future of space exploration is Starship!
May 5, 2021, is a date that will go down in history as one of the most significant
of the hectic space season that we are living in these last years.
It was on that day, in fact, that Starship SN15 (Starship Serial Number 15,
the latest prototype of the rocket designed by Elon Musk's SpaceX),
after the failures of its predecessors has finally managed to achieve a perfect vertical landing,
thus demonstrating the possibility of making reusable and autonomous a vehicle - the
carrier rocket - so far considered only as a brutal source of thrust.
With this first success, Starship has been officially called to play the role of protagonist
of interplanetary transport for at least the next ten years. An investiture reinforced also by the
recent decision of NASA to take advantage of its extraordinary characteristics to bring a human
crew to the Moon with the Artemis III mission. It is basically the story of a rocket that
becomes a space shuttle. It's the capsule that becomes a spaceplane. It's the science
fiction future suddenly becoming reality. Starship is the story of the rocket that
becomes a space shuttle. It is the capsule that
becomes a spaceplane. It's the future of a science fiction film that becomes reality.
I don't know if it has the same effect on you... Suddenly, human
landings on Mars in a decade or so seem much more realistic. And this increased confidence
gives us the desire to get to know Starship all the way. Which we're going to do in a moment!
Musk has often spoken about his dream of building cities on Mars. He believes that
settlements would need large numbers of people in order to become self-sustaining.
Realizing this dream requires a vehicle that's up to the task. Starship is a rocket
and spacecraft combination that could ferry more than 100 people a time to the Red Planet.
The system is designed to be fully reusable, meaning the principal hardware elements are
not discarded in the sea or allowed to burn up, as happens with some other launch systems,
but are instead recovered from space. They can then be refurbished and flown again,
reducing the cost of the whole enterprise.
Starship is able to land on earth,the moon and mars,
be refueled and returned to fly after only 24 hours,or be used for orbital transport carrying
100.000 kilograms of goods from one point of the planet to another in 2 to 3 hours.
At launch, the spacecraft, called Starship, will sit atop a rocket called Super Heavy.
The combined system will stand 120 meters tall and is also referred to as Starship.
Let's take the spacecraft first. With its nose cone and landing fins, the stainless-steel
vehicle resembles the rocket-ships from the golden age of science fiction.
At the rear of the 50 meters-long craft are six highly efficient Raptor engines,
developed over the course of a decade by SpaceX. The combustion takes place in stages,
and the engine's design cuts the amount of propellant that's wasted.
Towards the middle of the vehicle are the propellant tanks. These feed liquid
methane and liquid oxygen to the Raptors. Methane is the fuel and oxygen acts as an
oxidizer - a chemical that makes the fuel burn. The combination is dubbed methalox.
The choice of fuel is unusual for rocket engines, but methane can generate plenty of thrust.
It's also a prudent choice in light of Musk's designs on Mars.
The SpaceX founder says that liquid methane could be synthesized from Martian subsurface water
and from atmospheric carbon dioxide, using a chemical process known as the Sabatier reaction.
Re-fuelling Starship for the return trip to Earth using Martian resources
would confer a level of self-sufficiency, making journeys both more feasible and cost-effective.
Towards the front of the spacecraft - which is sometimes referred to as the
upper stage - is a huge payload compartment that will be able to haul large cargo or
people to destinations in deep space. Now, let's turn to the rocket. Measuring
70 meters long, Super Heavy will be filled with 3,400 tonnes of cryogenic (chilled) methalox.
It will be powered by around 28 Raptor engines (this specification has changed several times),
and It should be able to lift at least 100 tonnes of payload, and possibly as
much as 150 tonnes, to low-Earth orbit. This will make Super Heavy more powerful
than the immense Saturn V launcher used for the Apollo Moon missions in the 1960s and 70s.
The launch happens like this: As Starship ascends from the launch pad, the combined system will
begin to pitch over towards the intended orbit. When the upper stage separates in space, Super
Heavy flips over while falling back towards Earth. As it descends, Super Heavy will deploy steel
structures called "grid fins", from the sides of the booster. These will
help steer the rocket stage back towards its launch pad so it can be flown again.
Previously, SpaceX had wanted to ignite Super Heavy's Raptor engines to guide it down
to a precision landing on six steel legs. SpaceX does something similar with the first stages of
its Falcon 9 rockets, landing them safely on landing pads and drone ships after a launch.
But Mr. Musk recently tweeted to say that this thinking had
changed. SpaceX now plans to catch the falling booster using an arm on the launch tower.
This is the structure that provides engineers and crew members with access to the spacecraft
and rocket while they are sitting on the pad before launch. How exactly this "catch
mechanism" will work, however, remains to be seen. Meanwhile, the Starship upper stage could be
inserted into a "parking orbit" after separation, allowing it to be re-filled with propellant.
To re-fuel, the spacecraft would dock, or mate, with another Starship - already circling the
Earth - that acts solely as a propellant depot. The two ships would actually mate at the rear
section. They would use the same mating interface that
they use to connect to the booster on lift-off. To transfer propellant it becomes very simple:
You use control thrusters to accelerate in the direction that you want to empty.
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OK, you may be wondering... but basically, what will Starship be used for?
For long-haul trips to Mars and back - which could take up to nine months each way - Musk
is looking to install around 40 cabins in the payload area near the front of the upper stage.
You could conceivably have five or six people per cabin, if you really wanted
to crowd people in. But mostly we would expect to see two or three people per cabin, and so
nominally about 100 people per flight to Mars. The payload bay would also host common areas,
storage space, a galley, and a shelter where people could gather to shield from solar storms,
where the Sun belches out harmful charged particles into space.
But, as we have already said, before Mars, which is the original dream of Elon Musk,
Starship will be called to play a key role in the reconquest of the Moon on behalf of NASA.
How? According to the current plan, a Super Heavy rocket will launch Starship into lunar orbit.
Days later, a NASA Space Launch System rocket will launch the crew inside an Orion spacecraft
toward the Moon, which will rendezvous with the Starship while waiting in lunar orbit.
The crew will transfer to the Starship and descend to the Moon. After returning to lunar
orbit aboard the Starship, the astronauts will reboard Orion and return to Earth.
A bit complicated, don't you think? And at this point a question arises:
if the Starship is considered safe enough by NASA to drop humans on the Moon,
wouldn't it be just as safe (and more logical) for the crew to leave directly from Earth
aboard the Starship? This would save NASA about $3 billion per mission - and a difficult
rendezvous and docking in lunar orbit! And that is why we feel like saying that,
probably, if common sense prevails over corporate logic, the future of a
truly sustainable lunar exploration program will see Starship as the sole protagonist.
But Starship's possible uses don't end there.
The uncrewed, or cargo, version of Starship features a payload bay that opens up like the
mouth of a crocodile. This would allow it to be used for launching satellites. SpaceX says the
huge payload capacity opens up possibilities for new types of robotic science missions,
including telescopes larger than the James Webb observatory - the forthcoming successor to Hubble.
The system, also, could even be used for high-speed journeys between different
destinations on Earth. Musk has envisioned using Starship for rapid orbit-based transportation
between any two cities on Earth, an ambitious (or pretty wild) idea called point-to-point travel.
A Starship trip between New York and London, for example, would take an hour.
And more... Starship could eventually carry people to destinations in the "remote Solar System",
including gas giants such as Jupiter. But this remains a long-term objective.
Perhaps, Starship's most spectacular and revolutionary feature, however,
is its way of returning to land In order to bring other spacecraft back to Earth,
engineers have relied on parachutes, or designed the vehicle so that it can land on a runway.
But the Starship upper stage takes a different approach. When it is ready to land,
the ship initially re-enters the atmosphere at a 60-degree angle and then "belly-flops"
to the ground in the horizontal position. This mode of return relies entirely on the
atmosphere to slow the vehicle's descent. The downside is that, in this configuration,
Starship is inherently unstable. The vehicle, therefore, uses four
steel landing flaps, positioned near the front and rear of the vehicle, to control its descent.
This is much like a skydiver uses their arms and legs to control a free-fall.
As Starship approaches the ground, it should be slow enough to execute an engine burn that
flips the vehicle into a vertical position. It then uses the Raptors as retro-rockets
to guide the vehicle down to a safe landing. Musk says this general approach could be used
to bring Starship down safely on any planetary surface in the Solar System - Mars included.
SpaceX plans to have its first Starship test flight to orbit launch from Texas
and splashdown off the coast of an island in Hawaii, according to a document the company
filed recently with the Federal Communications Commission. The orbital flight test would mark
the first time SpaceX stacks both elements of its massive Starship system together,
the next key development step in its attempt to build a rocket that could one day land on Mars.
As outlined in the document, a Super Heavy booster stage will launch Starship from SpaceX’s
Boca Chica, Texas, facilities and separate in midair nearly three minutes into flight.
About five minutes later, that booster stage will return back to Earth
and splashdown in the Gulf of Mexico — or as SpaceX puts it: it will “perform
a partial return and land in the Gulf of Mexico approximately 30 km from the shore.”
Meanwhile, Starship (the top half of the entire rocket system) will continue into orbit,
nearly completing a full trip around Earth before plunging back through the atmosphere over Hawaii
roughly 90 minutes after launching from Texas. Starship will aim to nail a “powered,
targeted landing” on the ocean about 100 km off the northwest coast of Kauai,
the state’s northernmost island. The document didn’t name a specific date for
Starship’s orbital flight. Elon Musk said it could happen this summer or by the end of 2021, but an
email that accompanied Thursday’s filing indicated it could happen any time in the next year, before
March 1st, 2022. That email also says the maximum altitude for Starship is 116 km — an extremely low
orbital altitude sitting just north of the boundary between space and Earth’s atmosphere.
Whenever it happens, the orbital test will demonstrate Starship maneuvers that can’t
be simulated using computers. SpaceX intends to collect as much data as possible during flight
to quantify entry dynamics and better understand what the vehicle experiences in a flight regime
that is extremely difficult to accurately predict or replicate computationally. The flight data
gleaned from Starship’s test will anchor any changes in vehicle design... and build better
models for us to use in our internal simulations. However, to better understand the great revolution
that SpaceX is bringing in the field of space exploration, it will be enough to reflect on
this fact:: during its 30-year shuttle program, NASA built five Shuttles, one every six years on
average. Elon Musk, instead, is preparing to build Starship prototypes at the rate of one per month!.
Rather than choosing to analyze everything for years or decades before performing a first
flight test, as NASA has done, Musk's approach is to build,
throw, crash, solve problems, then try again. That a space program is conducted not with three
or four but with dozens of ships - and possibly hundreds... and that will definitely make a huge
difference! In a few years, the Starships launches will be counted per week, or even per day.
The average rate of four Shuttle flights per year meant that with an annual program cost
of $ 4 billion per year, the actual cost of a single flight was $ 1 billion. Musk
aims to manage 200 flights per year, which is possible with just 20 operational ships,
each re-airing every 36 days. This would give 5 million dollars per flight, or one 200th of the
cost of the Shuttle with five times its payload, for an overall improvement of a thousand times!
But there is more. The Starship will not only give us the ability to send human explorers to Mars,
the Moon, and other Inner Solar System destinations,
it will give us a two-order-of-magnitude increase in overall operational capability
to roughly do whatever you want to do in space. This includes not only the pursuit of a robust
program of probes to the outer solar system and making all kinds of experimental investigations
in Earth orbit economically feasible, but also the possibility of building giant space telescopes.
Much of our knowledge in physics comes from astronomy because the Universe is the biggest
and the best laboratory there is. There is no better place to do astronomy than in Space.
The Hubble Space Telescope, with a mirror of 2.4 meters in diameter,
has made extraordinary discoveries. What can we learn once we are able to build telescopes
2.4 kilometers in diameter in deep space? The possibilities are literally beyond imagination.
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