Papers by sasi Prabhakaran Viswanathan
Ground simulation of spacecraft motion simulating all six degrees of freedom is a challenging pro... more Ground simulation of spacecraft motion simulating all six degrees of freedom is a challenging problem due to several features of the natural dynamics in space that are difficult to reproduce on ground. Unlike terrestrial (aerial, land or underwater) vehicles, space vehicles have an overwhelmingly large percentage of their total energy in their translational motion. Dynamical coupling between the translational and rotational degrees of freedom can significantly affect the attitude motion of spacecraft. The attitude motion is particularly important for a spacecraft tasked to autonomously rendezvous and capture or dock with a target object in space. Here we present a ground simulator design for 6 DOF simulation of spacecraft engaged in autonomous rendezvous and proximity operation(ARPO) with an unaided target space object. These operations are very risky and difficult to carry out in space, since the target's motion is not well known in advance. Ground simulation using 6 DOF motion simulation capabilities can help reduce the risk of actual on-orbit ARPO missions. The novel design "Autonomous Rendezvous and Proximity Operation ground Simulator (ARPOS)" presented here mimics all the six DOFs of rigid spacecraft with high fidelity. ARPOS has the advantage of linear and spherical air bearings to reproduce the near frictionless environment of an actual spacecraft in space. Nomenclature b = position vector of the pursuer spacecraft in a geocentric inertial frame R = rotation matrix representing the attitude of the pursuer ν = translational (orbital) velocity of the pursuer in its body coordinate frame Ω = rotational (orbital) velocity of the pursuer in its body coordinate frame * 0 → superscript ( b 0 , R 0 , ν 0 , Ω 0 , b 0 g ) represents target object or target spacecraft a = (b 0 -b) relative inertial position vector of the target from the pursuer x = (R T a) relative position vector expressed in the pursuer's body frame Q = (R T R 0 ) attitude of the target resolved in the pursuer's body frame v = ν 0 -Q T (ν+Ω x x ) relative translational velocity of the target with respect to the pursuer in the target's body frame ω = (Ω 0 -Q T Ω) relative angular velocity of the target with respect to the pursuer in the target's body frame ω g = angular velocity of the spacecraft model mounted on the ground simulator with respect to the simulator base Ω g = angular velocity of the spacecraft model mounted on the ground simulator with respect to ground reference frame m b = mass of spacecraft model stage of the simulator J b = moment of inertia of spacecraft model stage of the simulator Π g = angular momentum of the spacecraft model stage in the body frame b g = position vectors of the centers of support of the two supported bodies in their corresponding simulator supports in a lab-fixed inertial frame x g = relative position between pursuer and target ARPOS expressed in inertial frame 2
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Papers by sasi Prabhakaran Viswanathan