14.5 Supersonic and Hypersonic Flights
293
14.5 Supersonic and Hypersonic Flights
Even after nearly 50 years since the first flight of Concorde and a little more than
20 years after its withdrawal from service, supersonic transport remains a major
challenge for the civil aircraft industry. In the days of the Concorde, the technological
achievements were through the design of an aerodynamic configuration suitable for
supersonic cruise, capable of taking-off and landing on the existing runways and to
develop materials resistant to the high stagnation temperatures at Mach 2 cruise. The
design of the engine with optimum specific fuel consumption and its reliability over
a range of more than 6000 km was also a true challenge. Since then, considerable
progress has been made in materials science both for the body, through the use of
titanium alloy, as well as for dealing with the high temperatures in the engines through
the use of turbine blades manufactured through single-crystal. The power of CFD
and the maintenance in service of large supersonic wind tunnels such as S2MA at
ONERA should allow for the optimisation of a better aerodynamic configuration.
Most influential aircraft manufacturers have a supersonic transport concept aircraft,
but it should be noted that these projects are not only successors of Concorde but
targets a different market which is corporate jets with maximum capacity of less than
20 passengers and it seems that this market is gaining a lot of interest. The targeted
cruise Mach numbers are in the range of 1.4 to 2 for the best trade-off between flight
duration and range.
With regards to aerodynamic performance, it is important to characterise the state
of the flow on the wing which could be laminar at cruise conditions. The other
challenges posed, are the direct environmental impact such as noise at take-off,
propagation of the sonic boom to the ground and emissions of CO 2 and NO x . There
are strict regulations already in place and the increasing need to cut down emission
could hinder the progress in the development of a new generation of supersonic
aircraft. But, this also drives further research into more specific field such as the
sonic boom phenomenon which prohibits supersonic flight over inhabited land. The
Defence Advanced Research Projects Agency (DARPA) in the United States is trying
to address this issue by studying the propagation of the sonic boom from the plane to
the ground and aerodynamic configurations which would minimise its intensity (see
Fig. 14.9). This work should also contribute to specifying a regulation on the acceptable level of sonic-boom intensity and open up the way for commercial supersonic
transport. The extrapolation of the wind tunnel tests to characterise and evaluate the
propagation of the real sonic boom in flight and its impact on ground will be then a
new challenge.
Beyond the supersonic flight, there exist also concepts of hypersonic aircraft with
trajectories inspired by intercontinental ballistic missiles and which could connect
the antipodes in less than two hours. Concurrently to these very futuristic projects,
one sees emerging the concept of “space tourism” which could represent a significant
increase of the atmospheric re-entries from other inhabited planets (see Fig. 14.10).
Such developments will require an upgrade and new developments of the hypersonic
wind tunnels.
293
14.5 Supersonic and Hypersonic Flights
Even after nearly 50 years since the first flight of Concorde and a little more than
20 years after its withdrawal from service, supersonic transport remains a major
challenge for the civil aircraft industry. In the days of the Concorde, the technological
achievements were through the design of an aerodynamic configuration suitable for
supersonic cruise, capable of taking-off and landing on the existing runways and to
develop materials resistant to the high stagnation temperatures at Mach 2 cruise. The
design of the engine with optimum specific fuel consumption and its reliability over
a range of more than 6000 km was also a true challenge. Since then, considerable
progress has been made in materials science both for the body, through the use of
titanium alloy, as well as for dealing with the high temperatures in the engines through
the use of turbine blades manufactured through single-crystal. The power of CFD
and the maintenance in service of large supersonic wind tunnels such as S2MA at
ONERA should allow for the optimisation of a better aerodynamic configuration.
Most influential aircraft manufacturers have a supersonic transport concept aircraft,
but it should be noted that these projects are not only successors of Concorde but
targets a different market which is corporate jets with maximum capacity of less than
20 passengers and it seems that this market is gaining a lot of interest. The targeted
cruise Mach numbers are in the range of 1.4 to 2 for the best trade-off between flight
duration and range.
With regards to aerodynamic performance, it is important to characterise the state
of the flow on the wing which could be laminar at cruise conditions. The other
challenges posed, are the direct environmental impact such as noise at take-off,
propagation of the sonic boom to the ground and emissions of CO 2 and NO x . There
are strict regulations already in place and the increasing need to cut down emission
could hinder the progress in the development of a new generation of supersonic
aircraft. But, this also drives further research into more specific field such as the
sonic boom phenomenon which prohibits supersonic flight over inhabited land. The
Defence Advanced Research Projects Agency (DARPA) in the United States is trying
to address this issue by studying the propagation of the sonic boom from the plane to
the ground and aerodynamic configurations which would minimise its intensity (see
Fig. 14.9). This work should also contribute to specifying a regulation on the acceptable level of sonic-boom intensity and open up the way for commercial supersonic
transport. The extrapolation of the wind tunnel tests to characterise and evaluate the
propagation of the real sonic boom in flight and its impact on ground will be then a
new challenge.
Beyond the supersonic flight, there exist also concepts of hypersonic aircraft with
trajectories inspired by intercontinental ballistic missiles and which could connect
the antipodes in less than two hours. Concurrently to these very futuristic projects,
one sees emerging the concept of “space tourism” which could represent a significant
increase of the atmospheric re-entries from other inhabited planets (see Fig. 14.10).
Such developments will require an upgrade and new developments of the hypersonic
wind tunnels.