“We haven’t even found
the limits of the composites”
Blake Scholl, Boom founder and chief executive officer
AEROSPACETESTINGINTERNATIONAL.COM // SEPTEMBER 23
heat. For example, at Mach 2.0, the nose and leading
edges can reach 242°F. At Mach 2.2, the temperatures
reach 307°F and more if the day’s ambient temperature,
is high.
Both XB-1 and Overture fly at Mach 2.2. Concorde
flew at Mach 2.0. “We chose Mach 2.2 because it is fast
enough to make a massive difference in travel, yet slow
enough to require only known, proven basic
technologies,” Scholl says.
The high temperatures at these speeds will damage
the engine core, so the inlet is designed to slow the
incoming air. “The process is to take the supersonic air,
the Mach 2.2 air that’s coming at you, then slow it,
compress it with the inlet and feed it to the engine at
about half the speed of sound,” Scholl explains.
“We’ve done a lot of the work through finite element
analysis FEA and computational fluid dynamics CFD,”
he says. “We use tools that were developed at NASA, plus
tools that we developed in-house ourselves for CFD.”
As well as slowing and compressing the
air, the inlet needs to provide uniform air
flow, which is easier to achieve at subsonic
speeds because the air goes straight into the
engine. However, at supersonic speeds a
much more complicated compression
inducting system is required. Scholl says,
“You’ve got to feed the air to the engine in a
sufficiently uniform way that it’s not going
to choke on you.”
Choking occurs when the air flow
3,700
parts in the XB-1
prototype
307°F
from supersonic air
friction
becomes compressed and its density increases to the
point where its velocity slows down too much.
The wind tunnel tests included all the modes of flight
from take-off, through ascent and cruise to over-speed
conditions. “We tested at Mach 2.24. The team came back
from that test and I said, ‘What are you going to do in the
next iteration?’ They said, ‘There is no next iteration.
We’re done.’ For a little while, I didn’t believe them. It’s a
wind tunnels
1 // The XB-1 is Boom’s
supersonic demonstrator
aircraft that will flight test
the technologies for the
company’s planned 55-seat
Overture supersonic airliner
2 // Forward fuselage
tooling for the XB-1
/AEROSPACETESTINGINTERNATIONAL.COM