Daniel Lancelle

A Scenario for a Future European Shipboard Railgun

Railguns can convert large quantities of electrical energy into kinetic energy of the projectile. This was demonstrated by the 33 MJ muzzle energy shot performed in 2010 in the framework of the Office of Naval Research (ONR) electromagnetic railgun program. Since then, railguns are a prime candidate for future long range artillery systems. In this scenario, a heavy projectile (several kilograms) is accelerated to approx. 2.5 km/s muzzle velocity. While the primary interest for such a hypersonic projectile is the bombardment of targets being hundreds of kilometers away, they can also be used to counter airplane attacks or in other direct fire scenarios. In these cases, the large initial velocity significantly reduces the time to impact the target. In this study we investigate a scenario, where a future shipboard railgun installation delivers the same kinetic energy to a target as the explosive round of a contemporary European ship artillery system. At the same time the railgun outperforms the current artillery systems in range. For this scenario a first draft for the parameters of a railgun system were derived. For the flight-path of the projectile, trajectories for different launch angles were simulated and the aero-thermodynamic heating was estimated using engineering-tools developed within the German Aerospace Center (DLR). This enables the assessment of the feasibility of the different strike scenarios, as well as the identification of the limits of the technology. It is envisioned that this baseline design can be used as a helpful starting point for discussions of a possible electrical weaponization of future European warships.

Thermal Protection, Aerodynamics, and Control Simulation of an Electromagnetically Launched Projectile

In recent years, several ideas to apply electromagnetic launch technology to spaceflight applications have come up. The use of electric energy to propel a payload carrier promises savings of propellant and, therefore, cost reduction for the transfer to orbit. Previous studies mostly comprised a rough estimation of the launcher and the vehicle size. Sometimes, a Δv-budget is given to illustrate the energy expenditure. Some studies neglect the necessity of a rocket engine. Only by means of an electromagnetic launch, without the capability to maneuver reaching an orbit is not achievable. In addition to a propulsion system, an attitude control system and a flight controller are needed to bring the vehicle into a circular orbit. The high acceleration and high velocities at low altitudes have set high demands on the payload-carrying vehicle. Its structure has to withstand the high acceleration forces during launch and the tremendous aerodynamic heat fluxes during ascent through the dense atmosphere. This paper presents a vehicle concept that addresses all these demands. The vehicle consists of a two-stage hybrid rocket engine system, a thermal protection system (TPS), and high-test peroxide monopropellant thrusters for an attitude control system and a guidance, navigation, and control system. A simulation model is created, which consists of a 6-DOF flight mechanics module, an aerodynamic module, propulsion module, TPS simulation, as well as a guidance and flight control simulation. Therefore, the complete ascent with all its aspects can be simulated. The simulation results show that a 710-kg vehicle launched with 2586 g and an initial velocity of 3642 m/s can carry 31.5 kg of payload into a 300-km circular orbit. The configuration of the vehicle can be defined by a set of input parameters. This allows the use of the model within an optimization tool.

Flight test results of investigation of acceleration effects on a gun launched rocket engine

Nowadays, much research has been done in the field of electromagnetic-driven Lorentz rail accelerators (LRA). To apply this technology to launch a sophisticated payload carrying vehicle, mechanical loads due to high acceleration have to be taken into account. The German Aerospace Center (DLR) is doing research in the field of a hybrid rocket propelled payload carrier which shall be launched from an LRA. The structure of the hybrid rocket engine (HRE) is the most critical component, regarding mechanical stress. To investigate the effects of high acceleration during the launch from an LRA, an experimental setup is created. An 80% scale model of an HRE is mounted on a 155-mm howitzer shell. The experimental setup is then launched from the Panzerhaubitze 2000 with an acceleration of 3300 g. The model is equipped with strain gauge sensors to determine deformation during the acceleration phase. An acceleration sensor is integrated to measure the acceleration during launch. Data of the strain gauge bridges and the accelerometer are sampled by an electronic device mounted on the projectile, and buffered in the internal RAM. The data are transmitted to a ground station during free flight by a telemetry device, which is mounted on the howitzer shell instead of a fuse. The flight path of the projectile is tracked by different radar stations to determine the impact point, so that the experiment can be recovered. The test shows that the HRE structure can withstand the mechanical loads that are caused by high acceleration that would occur during a launch from an LRA. Therefore, an HRE is suitable for high-acceleration launch. The sampled data are compared with finite element method calculations. Differences in simulation and measurement are observed.

A scenario for a future European shipboard railgun

Railguns can convert large quantities of electrical energy into kinetic energy of the projectile. This was demonstrated by the 33-MJ muzzle energy shot performed in 2010 in the framework of the Office of Naval Research electromagnetic railgun program. Since then, railguns have been a prime candidate for the future long-range artillery systems. In this scenario, a heavy projectile (several kilograms) is accelerated to approximately 2.5-km/s muzzle velocity. While the primary interest for such a hypersonic projectile is the bombardment of targets hundreds of kilometers away, they can also be used to counter airplane attacks or in other direct fire scenarios. In these cases, the large initial velocity significantly reduces the time to impact the target. In this paper, we investigate a scenario, where a future shipboard railgun installation delivers the same kinetic energy to a target as the explosive round of a contemporary European ship artillery system. At the same time, the railgun outperforms the current artillery systems in range. For this scenario, a first draft for the parameters of a railgun system was derived. For the flight path of the projectile, trajectories for different launch angles were simulated and the aerothermodynamic heating was estimated using engineering tools developed within the German Aerospace Center (DLR). This enables the assessment of the feasibility of the different strike scenarios, as well as the identification of the limits of the technology. It is envisioned that this baseline design can be used as a helpful starting point for discussion of a possible electrical weaponization of the future European warships.

Thermal protection-, aerodynamics- and control simulation of an electromagnetically launched projectile

In recent years several ideas came up to apply electromagnetic launch technology for spaceflight applications. Using electric energy to propel a payload carrier promises the saving of propellant and therefore cost reduction for the transfer to orbit. The conducted studies mostly comprise of a rough estimation of the launcher and the vehicle size. Sometimes a Δv-budget is given to illustrate the energy expenditure. Some of the studies neglect the necessity of a rocket engine. Only by means of an electromagnetic launch without the capability to maneuver, an orbit is not achievable. The high acceleration and the high velocities at low altitude evoke high demands on the payload carrying vehicle. Its structure has to withstand the high acceleration forces during launch and the tremendous aerodynamic heat fluxes during the ascent flight in the dense atmosphere. Moreover a propulsion system, an attitude control system, and a flight controller are needed to bring the vehicle into a circular orbit. This paper presents a vehicle concept that addresses all these demands. The vehicle comprises of a two stage hybrid rocket engine system, a thermal protection system, high test peroxide monopropellant thrusters for attitude control, and a guidance, navigation and control system. A simulation model is created, that consists of a 6-DOF flight mechanics module, aerodynamics model, propulsion module, thermal protection system simulation, as well as of guidance and flight control simulation. Therefore, the complete ascent with all its aspects can be simulated. The simulation results show that a 710 kg vehicle launched with 2586 g and an initial velocity of 3642 m/s can carry 31.5 kg of payload into a 300 km circular orbit. The configuration of the vehicle can be defined by a set of input parameters. This allows using the model within an optimization tool.