Particle decay, Oberth effect and a relativistic rocket in the Schwarzschild background

Abstract

We relate the known Oberth effect and the nonrelativistic analogue of the Penrose process. When a particle decays to two fragments, we derive the conditions on the angles under which debris can come out for such a process to occur. We also consider the decay and the Oberth effect in the relativistic case, when a particle moves in the background of the Schwarzschild black hole. This models the process when a rocket ejects fuel. Different scenarios are analyzed depending on what data are fixed. The efficiency of the process is found, in particular, near the horizon and for a photon rocket (when the ejected particle is massless). We prove directly that the most efficient process occurs when fuel is ejected along the rocket trajectory. When this occurs on the horizon, the efficiency reaches 100% for a photon rocket. We compare in two ways how a rocket can reverse its direction of motion to a black hole near the event horizon by restoring the initial energy-to-mass ratio: (i) by a single ejection or (ii) in the two-step process when it stops and moves back afterwards. For a nonphotonic rocket, in case (ii) a larger mass can be taken out from the vicinity of a horizon. For a photonic one, there is no difference between (i) and (ii) in this respect. We also consider briefly the scenario when a rocket hangs over a black hole due to continuous ejection of fuel. Then, the fuel mass decays exponentially with the proper time.

arXiv comment29 pages, matches published version

References in corpus (11)

• Kerr Black Holes as Particle Accelerators to Arbitrarily High Energy
• Acceleration of particles by black holes: kinematic explanation
• Center of mass energy of colliding electrically neutral particles and super-Penrose process
• Zero-momentum trajectories inside a black hole and high energy particle collisions
• Bound on Rindler trajectories in Black Hole spacetime
• Schwarzschild black hole as accelerator of accelerated particles
• Rindler horizons in the Schwarzschild spacetime
• Flow and peculiar velocities for generic motion in spherically symmetric black holes
• High speed escape from a circular orbit
• Particles with negative energies in nonrelativistic and relativistic cases
• Optimal escape from circular orbits around black holes