NFPA Journal - Fall 2021 - 30

PREPPED FOR
TAKEOFF
A DECADES-OLD
CONCEPT TAKES SHAPE
The idea of flying in a VTOL aircraft
from one end of a city to the other in
the same way you'd hop in a cab is not
new. In fact, it's several decades old.
In 1968, the Institute for Defense
Analyses, a private nonprofit research
group, published a report titled " The
Demand for Intercity Passenger Transportation
by VTOL Aircraft. " The report
envisioned a theoretical future of intercity
VTOL transport beginning in 1975
and thriving by 1985. It did, however,
recognize it was making some pretty
big leaps in order to arrive at this
imagined future. " In this study we have
assumed the VTOL [aircraft] have overcome
some very real problems involved
in operating ... in densely populated
city centers-noise, air pollution, safety,
and the availability of city-center vertiports, "
the report says.
Fifty years later, those limiting
factors are just being overcome, said
Alexander, who is leading a task group
for the NFPA 418 technical committee
to explore the fire safety challenges at
vertiports and to incorporate solutions
into the standard. Mostly, he said,
it's due to improvements in battery
technology. While industry statistics
are hard to come by, the majority of
emerging VTOL aircraft designs use
batterypowered
electric motors, which offer
a quieter, cleaner alternative to traditional
fuel-powered aircraft.
" We're seeing huge advancements
in battery technology, " Alexander
said. " Batteries are getting smaller
and lighter, and they're storing more
energy. "
It wasn't long ago that batteries suitable
for the UAM industry seemed out
of reach. But now those batteries are
here, Alexander said, and the industry
is poised to take off in the same way
the electric vehicle market has in recent
years. For air travel, the challenges to
getting to where we are now have been
more nuanced than in the world of
electric vehicles, however, and they provide
hints as to what the fire protection
challenges will be for this technology.
" In the helicopter world, for instance,
if I'm flying from point A to point B,
30 | NFPA JOURNAL * FALL 2021
the regulations state that when I arrive
at point B, I should still have 20 minutes
of fuel on board, " Alexander said.
For eVTOL aircraft, that translates to
the need for very energy-dense batteries-something
with the energy density
of 325 to 400 watt-hours per kilogram,
according to industry experts. The
batteries in most Tesla cars, for comparison,
deliver about 250 watt-hours
per kilogram.
As recently as 2018, engineering such
energy-dense batteries seemed like an
impossible feat, with headlines from
that year reading, " Why Tesla batteries
won't work for air taxis " and " The batFrom
Asia to the United States to
Europe, plans are underway to construct
vertiports. Many renderings of
these planned facilities look similar to
airports but built to a much smaller
scale, although others are more distinctive.
One concept being developed
in Italy, for example, is inspired by the
African baobab tree-a natural wood-
forward design featuring VTOL landing
pads stationed 100 feet in the air.
There are also plans to add VTOL
landing pads to existing structures-
configurations sometimes referred
to as vertistops. In June, Joby Aviation
announced a partnership with
Takeoff-and-landing infrastructure for these new types of urban aircraft range from
helicopter-style pads like an existing facility in Singapore (above) to fanciful pods rising
100 feet above an Italian landscape in the rendering on the facing page.
tery to power Uber's flying car dreams
doesn't exist (yet). " Fast-forward to
2021, however, and we see headlines
like " Innovative batteries put flying
cars on the horizon " and " Air taxis will
utilize next-generation batteries and
motors. "
What that means for experts like
Alexander is there's no time to spare in
addressing the fire safety challenges of
vertiports.
Miami-based parking garage operator
REEF Technology to add vertistops
to parking garage rooftops in several
metropolitan areas. " Parking structures
are ideal locations for us as they
allow us to deliver our customers as
close to their destination as possible
while minimizing any local impact and
reducing the need for building new
infrastructure, " the company said in a
press release.
VOLOCOPTER

NFPA Journal - Fall 2021

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