Now that SpaceX has landed a rocket after launching it into space, the possibility of reusing rockets isn’t as fantastic of an idea as it once was. But is it really that much more affordable?
SpaceX
has promoted reusability as a major cost-saver for the private
spaceflight industry. Right now, rockets are treated as trash once
they’ve taken off, so companies must spend millions of dollars on
manufacturing brand new rockets for every single flight. It costs $60 million to make the Falcon 9,
and $200,000 to fuel it, according to SpaceX CEO Elon Musk. Reusing
rockets could substantially lower these costs, he says; theoretically, a
rocket would only need to be refueled to launch multiple times again.
More than a fill-up.
That’s
not exactly right. SpaceX needs to be certain that its returned rockets
are capable of flying again. The Falcon 9 experiences major temperature
changes during its flights, as well as intense pressures and vibrations
from the winds in the atmosphere. These all produce wear-and-tear on
the vehicle’s hardware — meaning the rocket might need repairs and
updates before it can launch again. Refurbishing a rocket engine is
often expensive. And if those repairs take too long, SpaceX can’t launch
its vehicles as frequently.
Refurbishment
costs were one of the main reasons the Space Shuttle — another
partially reusable space system — turned out to be so expensive. The
Shuttle launched with the help of a giant expendable fuel tank and two
solid rocket boosters that were recovered post-launch. The Shuttle could
then land back on Earth once its time in space was over, like a plane
after flight.
The
reusable design of the Shuttle was meant to save money, since all but
the external tank could be used again post-launch. “Unfortunately it
didn’t work out that way for the Shuttle,” says Wayne Hale, a former
manager of NASA’s Space Shuttle program, and a member of the NASA
Advisory Council. “It was a very complicated vehicle that took an awful
lot of refurbishment to get it to fly again.” The Shuttle’s main engines
had to be replaced after every few launches. The vehicle also needed
lots of inspections and repairs between missions. Additionally, its
solid rocket boosters needed constant updates once they had been
recovered from the ocean, and the external tank had to be built anew for
each flight. All together, this helped to drive up the cost of each
Shuttle mission to somewhere between $450 million and $1.5 billion per launch.
Simpler design
The
Falcon 9 is nowhere near as complex as the Shuttle, so it won’t require
as much work. But the vehicle does experience some of the same flight
conditions as the Shuttle did. The Falcon 9 first stage — the
14-story-high rocket body that SpaceX recovered — can experience
temperature fluctuations that range from -250 degrees Fahrenheit in
space to upwards of 1,000 degrees Fahrenheit during its trip back
through the atmosphere, according to Steve Poulus, a former NASA project
manager who worked on the Space Shuttle. “This is where the design part
becomes paramount,” says Poulus. “SpaceX is probably using metals, and
some parts are probably composite, which are able to withstand those
temperature constraints and not do any damage.”
The
Falcon 9 also experiences heavy pressures and forces from the gases in
the atmosphere. The first stage reaches a maximum speed somewhere
between Mach 5.5 and 7.5. As it travels through the air, the
high-altitude winds can shake and press on the vehicle, causing damage.
“Those atmospheric loads can be up to hundreds of pounds,” says Poulus.By: Loren Grush (The Verge).
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