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Sonic Wind LSRV: A supersonic research automobile

The development story behind a 1,000mph vehicle

 

Left: The design of the Sonic Wind LSRV created by Waldo Stakes

 

 

The Sonic Wind LSRV (Land Speed Research Vehicle) design is the latest refinement of supersonic vehicle concepts and is currently in the build phase of the program. It is a bi-propellant liquid rocket powered automobile that is 48ft-long and 79in-wide from canted out tail fin tip to tail fin tip. It is 5ft tall at its highest point, which is at the top of its T-tail. The vehicle has an overall frontal area of slightly over 8 square feet.

 

Left: Currently being built in Southern California, Sonic Wind LSRV is 85% complete

 

 

 

The vehicle is powered by an XLR-99 rocket engine originally designed and built by Thiokol Motors for the North American X-15 rocket aircraft. The X-15 holds the official air speed record for aircraft which was set in 1967 at over 4,520mph. To this day no manned aircraft has officially flown faster than the X-15 rocket plane.


The XLR-99 rocket engine was known by its creators as the “Million Horse Power engine” because in theory it could generate that amount of power. XLR-99's maximum thrust is between 57,000 and 61,000 lbs at sea level, but was designed to reach peak performance at the edge of space or an altitude of 330,000ft. The engine will initially be used in a slightly detuned mode, developing between 26,000 and 34,000 lbs of thrust. This should push the Sonic Wind LSRV rocket car to well over 1,000mph.


Originally, the XLR-99 was designed to run on a combination of anhydrous Ammonia and liquid Oxygen or LOX. It is now being run on Methanol Alcohol and LOX, which will make the engine slightly more reliable and safer by eliminating the toxicity and hard starting characteristics of Ammonia. Methanol is much less corrosive and easier to handle. The use of Methanol will also give the engine better overall performance and ease of starting. Methanol combusts better than Ammonia, this will help in keeping the engine lit.


The XLR-99 engine has been modified by removing the injector assembly and mounting it to a new technology Compositex ablative composite one piece combustion chamber/nozzle combination of modern design. This new ablative nozzle/combustion chamber combination is built specifically to dimensions for peak exhaust gas expansion ratios at the altitudes of the venues we plan to run the car. This ensures peak engine performance at all times during the burn. Engine burn duration maximum is 22 seconds at maximum thrust with the current propellant loads. The Sonic Wind LSRV vehicle has been designed so as to be easily modified in order to carry more propellants in order to increase engine duration. Currently the chosen venue is the Bonneville Salt Flats in Utah, USA.

 

Left: The Compositex ablative combustion chamber and nozzle for the XLR-99 on Sonic Wind LSRV

 

 

 

 

 

 

 

Left: Drawing of the engine dimensions for the ablative nozzle

 

 

 

 

The Compositex ablative carbon composite combustion chamber eliminates the need for the high pressures of the original stock regenetively cooled nozzle and combustion chamber. This allows the engine, propellant and pressure vessels to be run at much lower pressures. This makes for a much safer vehicle overall.


The original XLR-99 turbo pumps were eliminated and replaced with a simple blow-down fuel and oxidizer system using Helium gas as the presureant for the LOX or oxidizer system, and Nitrogen gas to pressurize the Methanol system. The Helium and Nitrogen gases are stored onboard in high-pressure Titanium spheres of various diameters. Twin regulators and separate complete feed systems allow us to dial in the best fuel-to-oxidizer ratios for peak engine performance.


In the history of land speed record racing it is known that many of the most successful automobile designers chose to find the most powerful aircraft engine of the day and then design an aerodynamically efficient automobile around that engine. Sonic Wind LSRV follows that very same concept. The X-15 is still unmatched in performance to this day and that is why its’ engine the XLR-99 was chosen as the power plant for the Sonic Wind LSRV.


The overall vehicle structural design is unique in that the propellant vessels and gas pressure vessels are stressed into the chassis structure to aid in overall vehicle structural integrity and rigidity.


Aerodynamically, the Sonic Wind LSRV vehicle is unique to land speed record designs. In frontal view the vehicle has a “Bell” shape, which diverts most of the air that strikes the vehicle onto the top of the vehicle. With a bell plan form even the sides of the vehicle are considered the top of the vehicle because of the slope incorporated in the bell shape.


Sonic Wind LSRVs’ body was originally designed with a hollow area at the top of the center of the vehicle. The original design had a wasp waist contour. CFD analysis showed that there were shock anomalies created by this design that could possibly generate excessive lift and create drag. So the entire design was shortened and simplified into its current shape single slope shape. This allows better control of shock waves in order to anchor them over the top of the car to aid in negative lift.
The Bell shape of the body allows supersonic body shock waves to be used to further aid vehicle roll stability. Roll control is also enhanced by the shocks that will be generated and radiate downward from the lower rear supersonic bi wedge tail fins which are canted tip out at 45 degrees but can be adjusted for proper shock placement.

Left and below: These figures show CFD analysis of the original Sonic Wind LSRV design. As you can see the shock anomalies shown in the images could generate excessive lift and drag

 

 

 

 

 

There is a progressively expanding area rectangular tunnel running the length of the underside of the vehicle that allows underside air to be vacuumed into the plume of the rocket engine and evacuated from the underside of the car. This generates a negative lift throughout the entire length of the vehicle. It is similar to a modern day Formula 1 racing car ground effects system only slightly more complex in arrangement.


This vehicle design also incorporates an expanding vertical supersonic ogive-shaped air dam under the nose of the vehicle that wraps around the front wheels and expands automatically as necessary if a lifting moment is detected. In expanding it creates a turbulent air wake at the underside and base of the car. This wake creates high drag at the base of the car and the whole car gets aerodynamically heavier without changing the flow over the entire automobile. This new device eliminates the drag wakes caused by the adjustable canards of earlier LSR vehicles. The vertical supersonic ogive air dam is controlled by a balance sensor and powered by a pneumatic ram for quick and sure deployment and retraction. It will also be used as an air brake as it can be deployed so wide that it extends past the body sides and makes all the air on the lower part of the body turbulent increasing overall vehicle drag.


Steering is accomplished dynamically by rotating the front drum axle supporting the seven front ring wheels a-la motorcycles and also aerodynamically via a steering fin located at the very front, underside of the vehicle. The front wheel drum is mounted in trail so it will realign itself with the running surface when returning to the running surface after any lift moments.


The wheel designs are a ring wheel design. The ring wheel concept minimizes spinning wheel mass and centrifugal forces and unnecessary gyroscopic précis moments from taking control of the vehicle in cases of extreme yaw.


There are seven 2in-wide ring-shaped wheels or “ring wheels” slipped over a large diameter drum axle which contains front wheel lubricant (water) under the nose. There are two much larger diameter 8in-wide ring wheels at the rear of the vehicle, making it a true three-pointer vehicle. The front wheels, because of their smaller diameter and mass, will have gyroscopic authority over the nose of the vehicle adding stability.
 

Left: The author designed the wheels as you can see here with seven 2in-wide ring-shaped wheels slipped over a large diameter drum axle

 

 

Two three-stage reefed 17ft-diameter supersonic parachutes will be used to slow the vehicle down, one for deployment and the other as backup. A ground drag type of brake will bring the vehicle to a complete stop. This is done by collapsing the rear suspension by relieving air pressure in the rear shock absorbers at the end of a run and dropping the rear of the vehicle onto the playa. There is a rough drag plate mounted to the underside rear of the vehicle and the friction created by it dragging on the playa will slow and stop the vehicle while adding low-speed directional stability at the same time.


Another novel feature on this vehicle is the use of a high energy 250 watt Green diode Laser firing forward from the nose of the vehicle, which is used by the driver as a guide to aim the vehicle at the horizon. This is to aid in directional control and steering precision in the same way a laser sight is used on a weapon.


The driver is encased in a cylindrical safety capsule built of Maragin steel and wrapped with layers of composites, making it virtually blast-proof. In case of a mishap the capsule is separated from the vehicle and has its own supersonic parachute to bring it to a stop. The driver is suspended in the capsule in a Kevlar and nylon webbing or hammock to isolate him from shock and vibration.


All these features make for the most powerful and potentially fastest car ever built anywhere in the World. To read more about Waldo Stakes and the Sonic Wind LSRV project go to www.sonicwindLSRV.com

 

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