Getting to Mars
is a complex aff air
though. The Super
Heavy booster will
rst need to power
Starship and help it
get to orbit, before
returning to the
launch site itself.
Next, Starship needsto be refueled in
orbit by multiple
ights of a similarly
sized tanker before it
can head to Mars.
This tanker is
basically an alternate
version of Starship,
and is also powered
by a Super Heavybooster. There
are actually three
possible versions of
Starship, comprising
Starship, the
tanker, and a craft
for satellite delivery.
After topping up
the ship, the tanker
returns to Earth.JOURNEY TO MARS
Of course, there’s a giant rocket at
the center of Musk’s plan. In September
2017, Musk unveiled the Big Falcon
Rocket (BFR) at the 68th International
Astronautical Congress in Adelaide,
Australia. This was a two-stage design,
featuring a huge booster powered by 31
Raptor engines and the spaceship itself.
In fact, Musk thinks that we can build a
sustainable colony on Mars by 2050.
Fast-forward to November 2018, and
Musk was ready to christen the BFR with
a new name, even though it didn’t – and
still doesn’t – exist in any fully operational
capacity. The part of the rocket that
will actually carry people is now called
Starship, while the rocket booster is
referred to as Super Heavy. Starship
may not be going to any stars in the near
future, but ambitious as always, Musk
has said that later versions will.
The current prototype of Starship
is now built out of 301 stainless steel,
a departure from the aluminum
and carbon ber that was originally
proposed. Stainless steel doesn’t sound
as advanced or even as light as carbon
ber, but it is also a lot cheaper and may
even perform better. It also suits the
purposes of the rocket quite well, since
the type that SpaceX is using, which has
a high chrome-nickel content, actually
A REALLY BIG STAINLESS
STEEL ROCKET
gets stronger in cryogenic conditions. It
essentially has a high fracture toughness,
so it can withstand small structural
imperfections like cracks and prevent
them from propagating.
But while you want your rocket to
be able to withstand the cold in space,
you also want it to be able to tolerate
heat when it reenters the atmosphere.
Stainless steel has a really high melting
point, and it can go up to around 1,500°F.
The metal also allows SpaceX to work
toward Musk’s goal of a regenerative heat
shield. The rocket will need a heat shield
anyway for reentry, but by replacing
the tiles used on the current ship with
something akin to a stainless steel
sandwich, SpaceX can inject water into
the space between the two layers. The
water will absorb heat, and the shield will
bleed water through micro-perforations
to cool the windward side of the rocket, a
process known as transpiration cooling.
Truth be told, the Starship prototype
looks glorious, and its stainless steel
hull looks like a vision straight out of
60s science ction. If all goes according
to plan, Starship will stand roughly
118m tall atop the Super Heavy
booster. That’s taller than even the
Statue of Liberty and would make for a
really imposing sight.FEATUREAUGUST 2019 | HWM 39