Supersonic Institute

Lakewood, CO, United States

Supersonic Institute

Lakewood, CO, United States

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Miller A.R.,Supersonic Institute | Lassiter D.A.,Supersonic Institute
International Journal of Hydrogen Energy | Year: 2015

At Mach 2, the supersonic Concorde reduced travel time from New York to London to 43% of today's subsonic aircraft. However, it was not commercially successful because of issues related to supersonic shock waves: high fuel consumption and the sonic boom. The unexplored phenomenon of aerodynamic tunneling has the potential of enabling efficient, quiet, zero-emissions supersonic transport. A vehicle is transported from terrestrial point A to B via a closed, ambient-pressure tube containing an atmosphere more aerodynamically favorable than air. A predicted speed limit of such a vehicle is Mach 2.8-3.0 in a hydrogen tube, without shock waves. We have commenced a multi-phase project to experimentally measure the power and energy of a 1:16-scale tunneling vehicle. For each of six experimental gases - methane-hydrogen (mixture), methane, carbon dioxide, air, oxygen, and argon - we will measure thrust, power, energy consumption, and propulsive efficiency. This paper concerns the completed first phase, engineering design of the experimental vehicle, a monorail, wheeled tube vehicle that balances with ailerons and uses propeller propulsion. © 2015 Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.


Miller A.R.,Supersonic Institute
International Journal of Hydrogen Energy | Year: 2014

A challenge of aerodynamic tunneling in hydrogen, and to a lesser extent other high-efficacy gases, with propeller propulsion is the long distance to accelerate to cruise speed. This problem is partly inherent to high-speed vehicles and is partly due to relatively low propeller thrust in the low density of hydrogen. A theory of "density stages" for ideal gases is developed. The idea is to span the distance from zero speed to terminal velocity by stages of successively decreasing gas density but increasing speed of sound. For constant acceleration within each stage and the condition that the product of gas density and propeller frequency forms a monotone decreasing sequence, I prove that the time and distance to reach terminal speed are decreasing functions of the number of stages. Density stages can substantially reduce the time and distance for acceleration or deceleration. Copyright © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. Copyright © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights.


Miller A.R.,Supersonic Institute
International Journal of Hydrogen Energy | Year: 2014

Aerodynamic tunneling is the process of transporting a vehicle from terrestrial point A to B via a closed tube containing an atmosphere more aerodynamically favorable than air. Equations are derived for "gas efficacy," Γ, a measure of how well a gas increases Mach-1 speed or decreases drag of a vehicle. Theoretical results, Γp and its Mach-normalized form Γ1, based on reducing the vehicle to a flat plate, allows efficacy to be calculated ab initio as a function of only four gas parameters: ratio of specific heats, pressure, density, and viscosity. Hydrogen has the highest normalized gas efficacy (Γ1 = 48.5 s/kg). Ammonia, hydrocarbon gases, and helium have above-average efficacies. Xenon has the lowest (10.1 s/kg). Binary mixtures of hydrogen and methane (or natural gas) are proposed for lowering the upper flammability limit at a relatively small penalty in efficacy. Copyright © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.


Miller A.R.,Supersonic Institute
International Journal of Hydrogen Energy | Year: 2012

A hydrogen propeller is the method of propulsion of a conceptual supersonic vehicle that operates within a hydrogen-filled tube at cruise speed of 1 km/s. Because Mach number governs formation of shock waves at the blade tips, the high sonic speed of hydrogen allows a rotational frequency 3.85 times faster than the same propeller operating in air immediately outside the tube. Rankine-Froude propulsive efficiency and - for a given vehicle Mach number-propeller pitch and helix angle are invariant with respect to the atmosphere. To achieve constant efficiency at a given thrust and for adequate acceleration, the low density of hydrogen requires some combination of higher frequency, more blades, or larger diameter. The hydrogen propeller conceptual design employs 14 contra-rotating blades, 4.11 m diameter, and rotational frequency of 40.4 s-1 at translational velocity of 970 m/s. © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.


Miller A.R.,Supersonic Institute
International Journal of Hydrogen Energy | Year: 2012

To compare 24 common gases as potential operating atmospheres for tube vehicles, equations are derived for aerodynamic (tunneling) performance of the atmosphere and molar energy density of the tube vehicle. Aerodynamic performance is a function of the speed of sound and Reynolds number, and energy density is a function of the free energy of reduction or oxidation of the tube gas and the stoichiometric coefficients of the stored reactants. The product of these two parameters determines the rank of atmospheric merit. Hydrogen exhibits the highest aerodynamic performance, yields the fourth highest energy density, and has the highest overall merit. Acetylene, ammonia, and methane, in decreasing order, follow hydrogen in merit. Although superficially a promising tube gas, helium is below average in merit because of low energy density of the vehicle. © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

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