As we approach the 50th anniversary of the
Apollo 11 Moon landing this July,
the future of human spaceflight is at a crossroads.
The world’s space agencies have largely turned
their attention and focus towards the Moon,
with NASA recently announcing Project Artemis:
a plan to return astronauts to the lunar surface by 2024.
But against this backdrop, the very way we access space is undergoing a transformation.
For in the last few years alone, relatively young private
companies have managed to reduce launch costs
and achieved feats of engineering that even the oldest
space agencies have yet to emulate.
In these changing times, it appears that commercial
endeavours could become the catalyst enabling the next giant leap into the solar system.
In today’s Mars mission update, we’re going to be
focusing on one organisation that
is actively working towards and determined
to send people to Mars in the near-future:
SpaceX. We’ll cover their first steps towards
launching astronauts into space,
and the beginning of the Starlink constellation,
which could ultimately fund missions
to Mars. Finally, we’ll see all the very latest
developments on the spacecraft they are designing
to send people to Mars, Starship, as the first
prototypes enter the testing phase.
*Martian Colonist intro music plays*
SpaceX, a private company founded by Elon
Musk, has the stated goal of enabling people
to live on other worlds. With ambitious plans
to open a new frontier in spaceflight, they
have the goal of sending people
to Mars in the 2020s. They envision
this leading to a sustained human presence,
an expanding Martian settlement, and perhaps,
one day, the terraforming of the red planet
into a second home for humanity.
To achieve this lofty goal there are many hurdles
that SpaceX needs to overcome in the next
few years. They need to learn how to launch
people into space and keep them alive for
extended periods of time. They need to figure
out how to finance human missions to Mars,
especially given that most government initiatives
are currently focused on the Moon. And finally,
and perhaps most importantly, they need to
create a next generation spacecraft capable
of sending large amounts of cargo and many
people to the surface of Mars. The good news
is that just in the last few months SpaceX
has made great progress on all three of these
challenges.
First, whilst SpaceX are certainly no stranger
to launching payloads into orbit, with 71
Falcon 9 launches to date, they are now on
the verge of becoming the first company to
launch astronauts into space. In March, SpaceX
launched the Dragon 2, or Crew Dragon, into
space, becoming the first human-rated commercial
spacecraft to visit the ISS. Although no astronauts
were aboard for this initial demonstration
flight, the mission successful docked with
the space station, deorbited, and splashed
down in the Atlantic Ocean 6 days after launch.
The data collected from this flight, especially
from sensors attached to a life size dummy
aboard the flight, will provide important
information to refine the design of Dragon 2.
Though this mission was a stunning success,
unfortunately just 6 weeks after Dragon 2
returned to Earth, it was destroyed during
a vibration simulator test. It still isn’t
entirely clear what caused the failure, which
happened just before an escape thruster was
due to ignite, so SpaceX and NASA are currently
conducting a joint investigation to identify
what caused the fault.
Now, what this means in practice is that a scheduled
in-flight abort test, which had planned to use this
Dragon capsule, will have to be delayed, and unfortunately that also means
that the first crewed Dragon 2 flight, which had been scheduled for July,
will have to be pushed back.
Realistically, this probably means that SpaceX won't fly astronauts until early 2020,
but we’ll have to wait for official confirmation of the dates later
this year. In any case, whatever caused this
failure to happen, it’s actually encouraging
that this happened before any people were onboard, so that no lives were at risk.
There will certainly be some important lessons to learn from this and overall it should mean that SpaceX
will be a much safer provider once people do actually take to flight.
But if we want to go beyond Earth orbit, and
on to Mars, the second key challenge is how
to finance the missions. When you consider
that SpaceX’s development of Dragon 2 was
aided by a $2.6 bn contract from NASA, the
lack of similar governmental funding for human
Mars landers leaves SpaceX in the situation
of potentially having to self-fund the development
of spacecraft for Mars missions. Currently,
a large fraction of SpaceX’s revenue comes
from launching commercial satellites into
various orbits and cargo to the ISS. In fact,
their launch revenue last year alone has been
estimated at $2 bn, more than any other launch
provider. This capability is continuing to
expand, with April seeing the first commercial
flight for a paying customer of the world’s
most powerful rocket, the Falcon Heavy. And
although SpaceX’s launches are amongst the
cheapest in the world already, the proven re-usability
of the 1st stage cores for both the Falcon
9 and Falcon Heavy launches enables SpaceX
to save more money on each flight, and hence
devote an increasing fraction of their resources towards
research and development for their Mars endeavours.
However, launch revenue alone is not sufficient
if you want to bankroll large-scale missions
to Mars. SpaceX have another
ambitious plan which will dramatically increase
their available funding. This is Starlink,
a constellation of 12,000 low-orbit satellites
to provide internet to the entire world. Planned
to be complete by 2027, Starlink will provide
up to 50% faster internet speeds than current
fibre optic cables at an affordable price
anywhere on the world, be it land, sea, or air.
Just a few days ago, on May 24th, SpaceX
began constructing the Starlink constellation
with the launch of the first 60 satellites
on board a Falcon 9 rocket. Each Starlink satellite
has a mass of 227 kg, is powered by a
3 kW solar panel, and has a bandwidth around
17 Gbps. After deploying at 440 km altitude,
each satellite used a Krypton ion drive to raise
themselves to their operational 550 km orbit.
This choice of a Kr ion drive, instead of
the usual Xe, reduces the propellant cost
by around 5-10x whilst maintaining the impressively
efficient specific impulse of 1500 s.
Now given the relatively low orbits of the Starlink
satellites, and the sheer numbers involved,
the risk of collisions with orbiting debris
and space junk is naturally a concern.
But this is another area where the ion drive is
crucial, as it allows each satellite to autonomously
change its orbit to avoid collisions in space
and even to de-orbit itself over a few months
towards the end of their life. And should for whatever
reason a satellite become inoperable, residual
drag at such low orbital altitudes will cause the orbits
to naturally decay with the satellite re-entering
the atmosphere within 5 years.
SpaceX are planning up to 5 more Starlink
launches this year alone, so by the end of
this year the first 360 satellites could be
in place. Once 400 satellites reach orbit,
potentially within the next 12 months, a limited
internet service may begin for the United States.
By the time 800 satellites are in position,
moderate global coverage will begin, with
an estimated 1000 required before the constellation
begins to pay for itself. Under an agreement
with the US Government’s Federal Communications
Commission, SpaceX need to launch at least
2,200 satellites by a deadline in April 2024,
with the remaining 10,000 satellites in place by November 2027. Suffice it to say that this will be
a colossal undertaking, requiring on average
2 Falcon 9 launches every month from now until
2027, with an estimated cost of $10 bn to
complete the constellation. Whilst this may seem
like a lot upfront, SpaceX have already raised
over $1 billion since the beginning of this
year, which combined with previous investments
puts them in a strong financial position to
build this constellation. And the potential rewards are
huge, with an estimated profit of $30 - $50 bn / year
after completion, about 10x SpaceX's
estimated launch revenue at that point.
Starlink therefore represents a cornerstone in SpaceX’s plans to sustainably fund human missions to Mars.
Which brings us onto the most exciting aspect
of SpaceX’s vision: the development of Starship,
the spacecraft they plan to use to send the
first people to Mars in the 2020s. In brief,
SpaceX are developing a rocket system composed
of two parts: a 55 m upper stage called Starship
and a 67 m booster called Super-Heavy. With
the combined system capable of transporting
up to 100 tons of cargo or 100 passengers to Mars.
If you’re interested in more details about the design of Starship, Super Heavy, and how the combined system
will enable travel to Mars, you can find those in previous
Mars Mission Updates like
the one up there, but today I want to focus
on the latest developments in the construction
and testing of the first Starship prototypes.
SpaceX have come a long way since the last
Mars Mission Update in December. In January,
they completed the structure of a Starship
prototype called Starhopper in Texas. Standing
39 m tall, Starhopper will test SpaceX’s
raptor engines in a realistic flight environment
by conducting brief ‘hop’ tests, where
the vehicle ascends, hovers, and then returns
to land. One of the most striking things to
note is that Starhopper has been built out
of steel, which is a rather unusual choice in the aerospace industry today.
Originally, Starship was designed to be made out of
lightweight carbon fibre composites, so the choice to switch to the heavier option
of steel may at first seem rather counter-intuitive.
Elon Musk recently clarified the reasoning
behind this choice, and in short, it largely
comes down to the material behaviour of certain
alloys of steel. In particular,
an alloy called 301 stainless steel, which
has a high nickel and chromium content, has
highly desirable properties both at cryogenic
temperatures and at the highly elevated temperatures
experienced during atmospheric entry. Since
SpaceX chills their propellants to around
-200 C to increase their density, the material
lining the fuel tanks needs to not become
brittle at these temperatures. Unlike regular
steel, which certainly does, 301 stainless
steel actually becomes 50% stronger
at these cryogenic temperatures.
Considering now high temperatures,
steel also benefits enormously from its higher
melting point, allowing it to reach around
900 C while maintaining its structure, which
compares to just 200 C for carbon fibre
composites. But during atmospheric entry,
where temperatures can exceed 1500 C, additional
heat shielding is required. So the side of Starship
which is directly exposed to the flow during entry, also called the windward side, will
therefore be coated in a series of hexagonal
tiles, which have already been successfully
tested up to 1400 C. But should the tiles experience
higher temperatures, small outlets will either leak
liquid water or liquid methane, effectively allowing
the rocket to ‘sweat’, in a process called
transpiration cooling. The side opposite the
flow, also known as the leeward side, experiences lower
temperatures and so doesn’t require these tiles or the transpiration cooling system.
This system offers two major benefits: first, the
higher melting point of steel means a reduced overall
heatshield mass, which more than compensates for
the higher weight from choosing steel as your material; and secondly, the hexagonal tiles with
transpiration cooling don’t need to be replaced or refurbished after every single flight -
as is the case with ablative heatshields,
So Starship will therefore feature the first regenerative
heatshield, making the spacecraft completely and rapidly reusable.
Back to the Starhopper. In March,
the first Raptor engine was installed on the
Starhopper in Texas. Now you’ll notice that
the top half of the hopper is missing, which
is because the nose cone blew over during
some high speed winds in late January, so the fuel tanks were instead just installed in the bottom section
alone, which won't hinder the testing.
In the first phase of hop tests, only
a single Raptor engine will be fired, whilst
later tests will use 3 engines. The current
Starship design will eventually host 6 Raptor
engines, 3 optimised for sea-level operation
and 3 optimised for vacuum operation – with testing
of the vacuum Raptor engines due to commence around September. In April, Starhopper underwent its first static
fire test, followed a few days later by the
first tethered hop. The Raptor
engine has since been detached and sent to a lab for disassembly in order to assess its performance.
Currently, it is expected that a new Raptor engine will be installed shortly, with hops due to resume
in around a week’s time.
While the first Starhopper has been undergoing
testing, SpaceX have already begun constructing
the next prototypes. At the same site in Texas,
the first Starship prototype theoretically
capable of reaching orbit is also being assembled.
The orbital Starhopper will be a full-size
Starship prototype, 55 m tall and 9 m in diameter,
with a thicker shell and shock absorbers installed
on its landing legs. Meanwhile, a second orbital
Starhopper is being assembled in Florida by
an independent team, which will share progress and insights with the Texas team,
but ultimately they will pursue different build techniques.
If all goes well, then the
body of the Texas orbital Starhopper should
be complete in June, with propellant tanks,
landing legs, and support for Raptor engines
added soon afterwards. Bearing in mind that
the first Starhopper construction only started
late last year, it is seriously impressive
to see how rapidly SpaceX are developing this
new vehicle. Indeed, production of the first
Super Heavy booster could begin as soon as
August, so by the end of this year SpaceX
may not be far off having a full-scale test
article for the combined Starship and Super Heavy
system. We’ll learn more about the details of the latest
design, any changes involved, and about the testing of Starship, in a few weeks’ time
at a presentation Elon Musk has planned, currently for June 20th.
And of course, I’ll provide a summary of this in the next Mars Mission Update.
So that brings us to the end of this update,
but before I go, I have some really exciting personal
news to share with you. So as many of you know, I’ve been spending the last few months writing
my PhD thesis on exoplanet atmospheres. I
now have a complete draft, which should be
submitted in the next few weeks, so by this
summer I should finally have my doctorate.
Now since I know that some of you are also interested
in planets besides Mars, I’ve taken care
to write an accessible overview of exoplanet
science, and how we characterise their atmospheres,
all of which will be publicly available when
my thesis goes online later this year.
I’m also pleased to announce that I have
accepted a research position. In September,
I will be joining the Carl Sagan Institute
at Cornell University,
so in a few months times I’ll be moving
Stateside. While at Cornell, I’ll be developing
algorithms to figure out the composition of
exoplanet atmospheres with the upcoming James
Webb Space Telescope. And yes, this does include
the possibility of searching for biosignatures
on habitable exoplanets.
But in the meantime, there’s more upcoming
content planned for this channel.
So I had originally planned to talk a little bit about NASA's new Project Artemis in this update,
but it was already getting a little bit long by that point.
So I haven't forgotten about this. I've instead decided to make a standalone dedicated video about
Project Artemis, and what this might mean for the timelines involved in sending people to Mars.
So that video is being developed at the moment, and should be out within 2-4 weeks,
but, in any case, by the end of June.
I'm also planning to hold a livestream
on the 50th anniversary of the Apollo 11 landing in July,
and I'll discuss that in more detail at the end of the Project Artemis video (i.e. what will be involved in that
livestream). So, in any case, there's plenty more content coming up in the next few months.
And so I'll leave it there, and I look forward to seeing you next time!
Thanks for watching everyone, please do let
me know if you have any questions or comments
down below. To make sure you don’t miss
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