NASA aims to fly its
experimental electric plane this year
Following
a turbulent development that saw some components dramatically failing during
testing, the X-57 is set to finally take flight in 2023. Here's what's been happening.
Sometime later this year—perhaps this summer, perhaps this fall—an electric aircraft from NASA, the X-57, is set to take flight in California. It’s what NASA describes as its “first all-electric experiment aircraft,” and when it does lift off the ground, it won’t look the way that NASA has been depicting the plane on its website.
Here’s what to know about how the plane will work, the
challenges the program has faced, and how lessons from spaceflight helped
inform the details of its battery system.
Modification 2
If
the plane does indeed take flight this year as planned, it will do so in a form
called Modification
2, which involves one electric motor and propeller on each wing
giving the aircraft the thrust it needs to take to the skies.
While
the aeronautics and space agency had hoped to fly the plane—which is based on a Tecnam P2006T—in additional
configurations, known as Modifications 3 and 4, that won’t happen. Why? Because
making a plane that flies safely on just electricity is hard, and the program
is only funded through 2023. (IEEE Spectrum has
more on the program’s original plans.)
“We’ve been learning a lot over the years, and we thought we’d
be learning through flight tests—it turns out we had a lot of lessons to learn
during the design and integration and airworthiness qualification steps, and so
we ended up spending more time and resources on that,” says Sean Clark, the
principle investigator for the X-57 program at NASA.
“And that’s been hugely valuable,” he adds. “But it means that
we’re not going to end up having resources for those Mod 4 [or 3]
flights.”
It will still fly as an all-electric plane, but in Mod 2, with
two motors.
Exploding transistors
One glitch that the team had to iron out before the aircraft can
safely take flight involves components that electricity from the batteries have
to travel through before they reach the motors. The problem was with transistor
modules inside the inverters, which change electricity from DC to AC.
“We were using these modules that are several transistors in a
package—they were specced to be able to tolerate the types of environments we
were expecting to put it in,” says Clark. “But every time we would test them,
they would fail. We would have transistors just blowing up in our environmental
test chamber.”
[Related: This ‘airliner of the future’
has a radical new wing design]
A component failure—such as a piece of equipment blowing up—is
the type of issue that aircraft makers prefer to resolve on the ground. Clark
says they figured it out. “We did a lot of dissection of them—after they
explode, it’s hard to know what went wrong,” he notes, lightheartedly, in a
manner suggesting an engineer faced with a messy problem. The solution was
newer hardware and “redesigning the inverter system basically from the ground
up,” he notes.
They are now “working really well,” he adds. “We’ve put a full
set through qualification, and they’ve all passed.”
Lessons from space
Traditional
aircraft burn fossil fuels, an obviously flammable and explosive substance, to
power their engines. Those working on electric aircraft, powered by batteries,
need to ensure that the battery cells don’t spark fires, either. Last year in
Kansas, for example, an FAA-sponsored test featured a pack of aviation
batteries being dropped by 50 feet to
ensure they could handle the impact. They did.
In the X-57, the batteries are a model known as 18650 cells,
made by Samsung. The aircraft uses 5,120 of them, divided into 16 modules of
320 cells each. An individual module, which includes both battery cells and
packaging, weighs around 51 pounds, Clark says. The trick is to make sure all
of these components are packaged in the right way to avoid a fire, even if one
battery experiences a failure. In other words, failure was an option, but they
plan to manage any failure so that it does not start a blaze. “We found that
there was not an industry standard for how to package these cells into a
high-voltage, high-power pack, that would also protect them against cell
failures,” Clark says.
Help
came from higher up. “We ended up redesigning the battery pack based on a lot
of input from some of the design team that works on the space station here at
NASA,” he adds. He notes that lithium batteries on the International Space
Station, as well as in the EVA suits astronauts use and a device called the pistol
grip tool, were relevant examples in the process. The key takeaways
involved the spacing between the battery cells, as well how to handle the heat
if a cell did malfunction, like by experiencing a thermal
runaway. “What the Johnson [Space Center] team found was one of the
most effective strategies is to actually let that heat from that cell go into
the aluminum structure, but also have the other cells around it absorb a little
bit of heat each,” he explains.
NASA
isn’t alone in exploring the frontier of electric aviation, which represents
one way that the aviation industry could be greener for short flights. Others
working in the space include Beta Technologies, Joby Aviation, Archer Aviation, Wisk Aero, and Eviation with a plane
called Alice. One prominent company, Kitty Hawk, shuttered last
year.
Sometime this year, the X-57 should fly for the first time,
likely making multiple sorties. “I’m still really excited about this
technology,” says Clark. “I’m looking forward to my kids being able to take
short flights in electric airplanes in 10, 15 years—it’s going to be a really
great step for aviation.”
Watch a brief video about the aircraft, below:
Ingen kommentarer:
Legg inn en kommentar
Merk: Bare medlemmer av denne bloggen kan legge inn en kommentar.