The Lockheed X-59 QueSST: Pinocchio/Swordfish

Introduction

The X-59s first flight last week was a major step in NASA’s Quiet Supersonic Technology (QueSST) program. Every aircraft that flies supersonic is accompanied by the shadow of the sonic boom (read about it here : https://theaviationevangelist.com/2025/04/13/shockwave/ ). QueSST’s aim is to fly supersonic with no audible sonic boom. To achieve that there are two approaches. The first is to use atmospheric refraction (where the sonic boom makes a U-Turn back towards the sky) like what Boom Supersonic achieved with its XB-1 (read about it here : https://theaviationevangelist.com/2025/10/09/the-boom-xb-1-the-little-plane-that-could/ ) and the other is to engineer sonic booms that are weak and do not have the strength to reach Earth, and if they do, are very weak and barely audible. Enter the QueSST program.

The QueSST Program

The 1973 supersonic over land ban was a bodyblow to the Concorde and civilian supersonic travel over land in the USA.  While supersonic travel in general went into hibernation and Concorde motored on until 2003, the writing was on the wall. For supersonic travel to be profitable, aircraft needed to have the ability to travel supersonic over land and to achieve this, they needed to have no audible sonic boom.

NASA’s High Speed Research (HSR) program which ran between 1990-99 focused on a High Speed Civil Transport (HSCT) that would be environmentally acceptable. The program took into account fuel burn, emissions and of course noise pollution from sonic booms. The aircraft was to be Mach 2.4 capable and have a 300 passenger capacity. The tests involved tracking a Concorde in a U-2 spy plane to measure high altitude emissions and even had sonic boom mitigation technologies tested using a Lockheed SR-71 testbed. New engine nozzle technologies were tested to reduce takeoff and landing noise (on the Concorde the afterburners are responsible for the 110dB noise level). The HSR was probably the first time Computational Fluid Dynamics (CFD) was used to test new innovative designs. 

A heavily modified T-38 Talon and a F-4 Phantom in addition to F-16XLs were used to validate these designs and collect a database of sonic boom signatures, which could be applied to future aircraft designs. While Schlieren photography had existed for over a hundred years, NASA innovated on the technique and created Air-to-Air Background Oriented Schlieren Technique (AirBOS) where a full sized aircraft could be photographed using the Sun as a background to see where the shockwave formation and their interaction with each other and ambient surroundings.

While the actual HSCT program itself ended in 1999 due to lack of funding and Boeing’s withdrawal from the program , the AirBOS series of the tests continued through the 2010s, of note were 2019 flights featuring two T-38s going supersonic at close formation and the shockwave interaction of the two planes.

Lockheed Martin was awarded the preliminary design contract for the X-59 by NASA in 2016.

The X-59 First Steps

The design parameters were to create a Mach 1.42 capable aircraft with a service ceiling of 55,000 feet and a supersonic perceived sonic boom of not more than 75dB, the equivalent of a car door being shut (https://ntrs.nasa.gov/api/citations/20220009074/downloads/QuesstMissOvuaX59Pres_050822r.pdf) . This puts the X-59’s perceived sound over 10 times quieter than the Concorde’s 110dB.

The preliminary design steps were to create a 9% subscale model that could be tested in a wind tunnel between Mach 0.3 – 1.6. Lockheed was finally awarded a $247.5 Mn contract to design and build the low boom X-59 in April 2018, the designation X-59 QueSST would follow in June 2018.

The X-59 Design

The design approach to the X-59 was to alter the aircraft’s shape & aerodynamics to prevent shockwaves from merging into a loud sonic sonic boom, instead the design was about dispersing them before they got stronger and keeping the sonic thump under 75dB. Such aircraft would be of a long and slender profile which distributes pressure disturbances over a longer axial distance (https://www3.nasa.gov/specials/Quesst/how-x59-designed.html  )

The highlevel specs of the X-59 are an overall length of 99.7’ , a wingspan of 29.7’ and a height of 14’. The all moving stabilizers have a span of approx 15’. For a long aircraft the wheelbase is just 17.6’. With the center of gravity exactly above the main landing gear borrowed from an F-16. The aircraft is area rule compliant.

To prevent the formation of a N wave , the X-59’s nose is over a third of the X-59’s length at between 30-35 feet to canard, 38 feet to cockpit. The nose of the X-59 is treated as an independent structure before being mated to the fuselage and is manufactured by Swift Engineering.

A frontal view of the nose presents a flat almost duck beak-like profile with a tip in the middle. The top view of the nose tip looks like swept back wing leading edges. The highly sculpted surfaces leading off the nose leading edge look like the nose ramping upwards and back towards the cockpit and a relatively flattish profile leading back towards the rearset nose landing gear. The reason for the shape of the nose is having a conical shape like earstwhile Concorde leads to shockwaves going off in unpredictable directions and in some cases blanketing the vertical rudder. As we move further back the nose cross section transitions from the flat tip to an elliptical type of complex shape as it moves up towards the cockpit. The nose funnel cross section is approx 2 x 2 feet. Overall the nose with its length and continuous uninterrupted design ensures the first shockwave off the tip is soft and has nowhere to merge into propagating downwards and staying soft (below 75dB).

Just before the cockpit at around the 30-35 foot mark aft of the nose tip are the X-59’s fixed canards. They serve two purposes, the first is shockwave separation , distribution and keeping it off the cockpit & eXternal Vision System (XVS, more on this later), the second is to provide forward lift. The X-59’s design is such that the wings are at mid fuselage and the single engine is right back under the vertical T tail, to compensate for the unbalanced lift (as the centre of gravity moves rearward) generated by the lifting surfaces towards the rear of the X-59, the aircraft needs fixed canards that are upward canted generating a dihedral angle. Such positioning helps the X-59 generate a nose up pitch in cruise (at low speeds with their 63° swept angle, they generate vortex lift at high AoA) and maintain balanced flight without generating drag. Furthermore the canards interact with the shockwaves coming off the nose and with the wings further back to ensure shockwave strength is at a minimum, this helps with sonic boom mitigation. The trailing edges of the canards meet the fuselage at 59° angle with the fuselage. Such angling helps with boom mitigation as well. The canard root chord is 10.2’, tip chord of 3.8’ and the span is 13’. The canards generate approx 15-18% of total lift. The canards are subtly blended into the forward fuselage.

The nose design of the X-59 is such that there can be no cockpit canopy bubble like most experimental aircraft. Instead the cockpit of the X-59 has one major similarity to Charles Lindberg’s, Spirit of St Louis, both of them do not have a forward windshield and both of them use side windows to help with external pilot vision. In the Spirit of St Louis , Lindberg had to look out the flat side windows, in the case of the X-59 the side windows are contoured and offer a truncated forward view with the vision line running parallel to the nose. What the X-59 has is the XVS. The XVS consists of two high resolution 4K cameras, one is on the upper nose just forward just forward of where the cockpit windshield would have been, the camera is fairinged to deflect shockwave formation. The bottom camera is just forward of the nose gear and approx 12-18 feet aft the nose tip. The feed from both cameras is processed by the XVS computer for real time stitching and augmentation and overlaid on the secondary cockpit display which includes augmented reality (AR such as runway lines, glide slope indicators & Traffic Collision Avoidance System (TCAS). The latency is >50ms and is designed to feel natural to the pilot.

The flat (0°)low aspect ratio (AR) wings of the X-59 are a double delta(such wings trade pure supersonic speeds for incremental low speed handling) with the inward leading edges of 76° and outward leading edge of 68.6°, the crank is at approx 50-55% outboard sweep. The leading edge of the wings starts about a foot behind the canard trailing edge root (approx 45’ from the nose tip), the geometry of the canard trailing edge is such that the canard tip appears to be at the same level (or close) to the wing leading edge. Such architecture is critical to boom splitting, while at the same time maintaining aerodynamic continuity. The leading edge of the wings starts exactly at the cockpit side windows. The wing root chord is 25’ and the wings feature a washout of approx 2-3° for tip stall mitigation. 

The trailing edges of the wings have a pair of inboard flaps and the outboard ailerons (with restricted movement to avoid fouling up with the crank)are just beyond the trailing edge crank. The canards work in tandem with the ailerons by providing a small positive deflection and reducing mid body shock by 4%. We realize the X-59 is actually a cranked arrow (read here: https://theaviationevangelist.com/2025/10/02/lambda-wings-moving-wingtips-flying-wings-part-3/ ). The trailing edge crank is approx 50-55% of the span with an inboard sweep of 59° and an outboard sweep of 63°. We also observe matching canard angles (something stealth aircraft implement (https://theaviationevangelist.com/2025/10/22/the-theory-of-stealth/ ). The trailing edge allows inboard and outboard control surfaces to be decoupled. Area rule compliance is important for all transonic aircraft and the trailing edge crank ensures the same. 

The lower wing root is seamlessly blended into the fuselage underbelly using area rule sculpting to avoid waist shock like what Concorde had. The 22’ of blending appears to look canoe-like and is 1.8’ at the deepest point between the wing and fuselage. The blending reduces underside pressure by 18%. The sculpting incorporates fuel tank #2.

The all moving horizontal stabilizer has a span of 26.2’ (almost as large as the wings) root chord 14.6’ and a tip chord of 5.9’. Here is where it gets interesting! The area of the stabilizers at 2582 ft is actually larger than the wings at 2152 ft!! The reason for this is at Mach1.4 and 55,000’ the stabilizers are responsible for pitch control. The leading edge 63° (we now have the canards and horizontal stabilizers & wings having similar angles). The trailing edge of the stabilizer has a forward sweep of 12.6°. Such a design delays tail shock and extends pressure recovery, the delay is 22ms v/s a neutral trailing edge. A front view of the aircraft highlights how the canards & wings are mounted at two distinct vertical heights relative to the fuselage waterline. Such a placement further prevents shockwaves merging by separating them vertically, thereby reducing boom strength. ( Carnards at 1.8’ above the wing and the horizontal stabilizers appear to run at a similar angle and height to the wing). 

The vertical tail assembly of the X-59 includes the engine fairing (the engine sits on top of the fuselage using area ruling) , the vertical tail above it and the T tail at the top. Behind the engine is the aft shelf that extends about 3-4’ under the engine exhaust to divert supersonic exhaust upwards, without it the jet’s mach diamonds will interact with the fuselage boundary layer amplifying sonic booms. 

The vertical tail of the X-59 is 14’ tall (including the engine height) with a backward sweep of 59° and a pure tail height of 10.5’. The horizontal fins on the T tail appear to have a similar geometry to the canards albeit about half the size.

The Engine

The X-59 uses a single GE F-414 low bypass afterburning turbofan with a bypass ratio of 0.25:1. The same engine is used on the F-18 Super Hornet. As mentioned earlier the engine is mounted on top of the fuselage and below the vertical tail fin. The engine produces 14,000 pounds of thrust dry and 22,000 pounhds of thrust with full afterburner. The engine with a service ceiling of 60,000’ is capable of handling the X-59’s test parameters.

Materials & Construction

Over 85% of the aircraft is made of carbon fibre reinforced polymers (CFRP), working with such a material helps achieve the complex aerodynamic shaping of the X-59. The nose of the aircraft which weighs in at approx 300 pounds is a hollow CFRP cone. The inside of the nose has between 6-8 CFRP bulkheads that are each spaced about 4-6’ apart. Between the bulheads are between 8-12 stringers that run the full length of the nose cone. The nose is OOA (Out of Autoclave) cured to hold precise shape and is bolted to the fuselage with shear resistant bolts at flange joints that transfer loads to the fuselage. The nose is pressurised at 2-5psi with dry nitrogen. This increases panel stiffness by between 30-40% and helps boom consistency while preventing flutter and protecting avionics.

The fuselage is a central load bearing barrel that integrates 4 fuel tanks that hold 12,500 pounds of fuel, enabling the aircraft a range of 3,500nm. Furthermore the fuselage also integrates the cockpit and avionics. Titanium is used in the X-59 wherever it comes in direct contact with CFRP. The wingbox is aluminium and is bonded to CFRP skins via co-cured doublers. All the other bulkheads in the fuselage are CFRP (Toray 2510 prepeg). The forward engine firewall is titanium-aluminium-vanadium (Ti-6Al-4V), while the mid engine ring is Inconel, the aft nozzle is CFRP+Inconel liner.

Summation

The X-59 promises a fresh new look at supersonic flight and the data collected will be invaluable to future supersonic airliners. With a total of approx 50-100 flights planned over a 2-3 year period, the first 20-30 flights are expected to be subsonic and will test onboard systems. The next 20-40 flights will be transonic (over Mach 1.0) and will focus on acoustic measurements over remote areas such as Edwards AFB. The final 10-20 flights are planned over cities such as Galveston,TX and others to gather public perception. 

The first planned supersonic flight is expected to be mid 2026….

Innovation is Key…

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