Missile launching, staging and maneuvering present unique numerical modeling and simulation challenges to CFD codes. These challenges are because of the complex geometry, complex physics, and relative motion between different bodies. CFDRC has developed coupled state-of-the-art CFD technology, 6-DOF and control modules to solve those challenging problems. Our technology provides solutions for an extensive range of missile transient events, including launching, staging, and meneuvering.

In addition to developing software technologies, CFDRC provides engineering consulting services for a full range of missile transient events and aerodynamics problems, including those involving multiple moving bodies and moving control surfaces. Our engineers are highly experienced at applying CFD technology to these problems.

At high altitudes and low ambient pressures, the rocket plumes of missile control jets expand much faster and wider than at sea level. The plume expansion may even interfere with the targeting sensors in the nose of the missile. The finite rate chemistry and thermal non-equilibrium models that CFDRC engineers developed and incorporated into CFD-FASTRAN allow accurate prediction of such effects. In addition to these models, the code also employs models for surface reaction. This enables the modeling of reacting flow fields in hypersonic flows, as well as the surface reactions that are caused by the aerodynamic heating in such flows.

In this study, CFDRC engineers computed the interaction of a control jet with the hypersonic flow field around the AIT interceptor missile at an altitude of 110,000 feet and a velocity of 3.5 km/sec (corresponding to a Mach number of 8.2). The jet exit Mach number was 3.5. Reacting and non-reacting simulations of the mixing of the solid propellant exhaust jet with the external flow showed the potential for external afterburning of the plume gases.

This simulation conducted by CFDRC engineers, computes the trajectory of a guided missile nose cone with and without an active-fin control autopilot. In one case the autopilot was inactive and the control surfaces remained stationary. In the other case, an autopilot model was coupled with CFD-FASTRAN and was used to direct the motion of the control surfaces. The simulation algorithm is shown on the right, while the movies below show the relative effect of the autopilot on the trajectory and alignment of the missile.

The coupled aerodynamics and rigid-body dynamics solvers, together with the automatic chimera overset grid capability allow the simulation of such complex problems. This type of simulation enables designers and analysts to test control modules and maneuvering capability in real-life type situations where aerodynamics, flight dynamics and controls are fully coupled.

CFDRC engineers used the CFD-FASTRAN multiple moving body capability to predict the trajectories of the canard covers for this projectile, and to assess the potential impact of the covers with the tail fins. The ejection of the canard covers is initiated under the influence of spring mechanisms. The covers then rotate on hinges for a short duration, before being released into the ambient high-speed air-stream. The covers experience rotation rates of up to 15000 degrees per second.

The code's motion models enable full specification of the time-dependent forces or constraints applied by the spring mechanisms, the hinges, and the release mechanisms. Such constraints and point forces can be intuitively and easily specified in the code's GUI. This computation relies not only on the motion model, but also on the ability of the automated chimera overset grid to handle multiple moving bodies in relative motion.

This technology was developed by CFDRC engineers and can be easily adapted for customer specific applications.

This 2D tube launch demonstration shows a generic missile ejecting out of a canister. The thrust forces were specified using a time dependent pressure and temperature profile at the nozzle exit of the missile. This type of simulation allows the analyst or design engineer to evaluate potential contact between the missile and the canister and to evaluate the separation dynamics as the missile exits from the canister while accounting for all the physics and body dynamics.