Abstract: Various schemes have been proposed for reducing the cost to access space; however, few have identified a path to successfully bring such a technology to market. The value proposition of cheap-launch to the current geosynchronous Earth orbit (GEO) communications satellite paradigm is not high--here it is operational costs and not capital costs that dominate. Operators of low Earth orbit (LEO) systems, however, may find that their continued survival dependent on reduced launch costs. Lower launch costs allows for utilization of less reliable and hence less expensive satellite systems. By developing a satellite cost model utilizing a build methodology that takes advantage of cheap-launch, an almost 50% cost reduction can be demonstrated in a LEO constellation's recurring capital expenses. In this case, it will be shown that a cheap-launch LEO system is in fact cheaper to build and deploy than current GEO systems, potentially triggering a shift from GEO to LEO as the dominant satellite communications paradigm.

Abstract: The ram accelerator is a chemically powered hypervelocity mass driver that operates with in-tube propulsive cycles similar to airbreathing ramjets and scramjets. The launcher consists of a long tube filled with a pressurized gaseous fuel-oxidizer mixture in which a subcaliber projectile having the shape similar to that of a ramjet centerbody is accelerated. No propellants for this launch process are carried aboard the projectile; it effectively flies through its own propellant tank. The ram accelerator at the University of Washington has been operated at velocities up to nearly 3 km/s and in-tube Mach numbers greater than 7 in methane-based propellant mixtures. This Mach number capability corresponds to muzzle velocities greater than 7 km/s when using fuel-rich hydrogen-oxygen propellant. The combination of hypervelocity muzzle velocities and the ram accelerator's inherent scalability to multi-ton payload sizes makes it suitable for direct space launch. Technical issues associated with the implementation of the ram accelerator technology for direct space launch applications are presented here.

Abstract: The ram accelerator is a hypervelocity launcher that operates on the principles of a chemically propelled in- tube ramjet. This concept is unique in its potential to launch large-scale projectiles to Earth orbit velocity while controlling the in-tube acceleration. Experimental investigation of the operating characteristics of the ram accelerator at several different facilities around the world has resulted in the demonstration of many key gas dynamic principles and logistical aspects needed for a space launch facility. These experimental results have been used to determine the parameters for a ram accelerator system capable of launching a 2000 kg projectile having an effective density of 1000 kg/m3 at velocities of 6-8 km / s , without exceeding 1500 g. The results of this study indicate that a multi-stage ram accelerator system would be an effective means to launch large-scale projectiles into orbit.

The ram accelerator, a chemically driven ramjet-in-tube device is a new option for direct launch of acceleration-insensitive payloads into Earth orbit. The projectile is the centerbody of a ramjet and travels through a tube filled with a premixed fuel-oxidizer mixture. The tube acts as the cowl of the ramjet. A number of new concepts for a ram accelerator space launch system are presented. The velocity and acceleration capabilities of a number of ram accelerator drive modes, including several new modes, are given. Passive (fin) stabilization during atmospheric transit is investigated and found to be promising. Gasdynamic heating in-tube and during atmospheric transit is studied; the former is found to be severe, but may be alleviated by the selection of the most suitable drive modes, transpiration cooling, or a hydrogen gas core in the launch tube. To place the payload in Earth orbit, scenarios using one impulse and three impulses (with an aeropass) and a new scenario involving an auxiliary vehicle are studied. The auxiliary vehicle scenario is found to be competitive regarding payload, and requires a much simpler projectile, but has the disadvantage of requiring the auxiliary vehicle.

The ram accelerator, a chemically propelled mass driver, is presented as a new approach for diretly launching accleration insensitive payloads into low earth orbit. The cargo vehicle resembles the centerbody of a conventional ramjet and travels through a launch tube filled with a premixed gaseous fuel and oxidizer mixture. The tube acts as the outer cowling of the ramjet and the combustion process travels with the vehicle. Two modes of ram accelerator drive are described, which when used in sequence, are capable of accelerating the cargo vehicle to 10 km/sec. The requirements for placing a 2000 kg vehicle with 50% payload fraction into a 400 km orbit, with a minimum of on-board rocket propellant for circularization maneuvers, are examined. It is shown that aerodynamic heating during atmospheric transit results in very little ablation of the nose. Both direct and indirect orbital insertion scenarios are investigated and a three-step maneuver consisting of two burns and aerobraking is found to minimize the on-board propellant mass. A scenario involving a parking orbit below the desired final orbit is suggested as a means to increase the flexibility of the mass launch concept.