Photon Rocket Research Articles

Complex structure of Kerr geometry and rotating ‘photon rocket’ solutions

In the frame of the Kerr–Schild approach, we obtain a generalization of the Kerr solution to a nonstationary case corresponding to a rotating source moving with arbitrary acceleration. Similar to the Kerr solution, the solutions obtained have geodesic and shearfree principal null congruence. The current parameters of the solutions are determined by a complex retarded-time construction via a given complex worldline of source. The real part of the complex worldline defines the values of the boost and acceleration while the imaginary part controls the rotation. The acceleration of the source is accompanied by lightlike radiation along the principal null congruence. The solutions obtained generalize to the rotating case the known Kinnersley class of the ‘photon rocket’ solutions.

Robinson-Trautman radiating metrics with zero news and photonrockets

We show that a Robinson-Trautman radiating metric has zeroBondi news if and only if it is a Kinnersley metric for apoint mass accelerating arbitrarily with the emission of matter of zerorest mass. This corrects a statement, which we made in arecent paper (1999 Class. Quantum Grav. 16 611-7),that the news function vanishes only for those Kinnersleymetrics that have axial symmetry. It follows that none of the`photon rockets' of the Kinnersleyfamily generate gravitational waves.

Effect of Photon Rocket in X-ray Binaries

AbstractIt is shown that X-ray binaries can be accelerated by their own radiation. It is possible if the magnetic field of a neutron star in a binary differs from the dipolar field. Asymmetric X-ray emission generated due to accretion of matter onto a neutron star surface creates an accelerating force. Its magnitude can be comparable or even larger than gravitational attraction of the binary to the Galaxy.

Letter: A Note on Kerr-Schild Metrics with Geodesic Null Vector

We calculate the Einstein and Landau-Lifshitzpseudo-tensors for Kerr-Schild metrics with geodesicnull vector and show that the first of these vanishesidentically but that the second does not. These results correct a statement by Gurses and Gursey whoclaimed that both were zero. We also show that thesub-class of metrics for which both pseudotensors vanishincludes the Kinnersley photon rocket metric for anarbitrarily accelerating point mass.

Pure and gravitational radiation

The well known treatment of asymptotically flat vacuum fields is adapted to pure radiation fields. In this approach we find a natural normalization of the radiation null vector. The energy balance at null infinity shows that the mass loss results from a linear superposition of the pure and the gravitational radiation parts. By transformation to Bondi-Sachs coordinates the Kinnersley photon rocket is found to be the only axisymmetric Robinson-Trautman pure radiation solution without gravitational radiation.

The gravitational wave rocket

Einstein's equations admit solutions corresponding to photon rockets. In these a massive particle recoils because of the anisotropic emission of photons. In this paper we consider rocket motion powered only by the emission of gravitational waves. We use the double-series approximation method and show that a loss of mass and gain in momentum arise in the second approximation because of the emission of quadrupole and octupole waves.

Gravitational radiation and the photon rocket

The absence of gravitational radiation in Kinnersley's `photon rocket' solution of Einstein's equations is explained by the fact that in Kerr - Schild coordinates the pseudo-energy - momentum tensor vanishes everywhere. As a result the energy and momentum of the rocket and null fluid is conserved without any contribution to or from the gravitational field. A description is presented in terms of energy and momentum flow in a flat background spacetime.

Photon rockets and the Robinson - Trautman geometries

We point out the relation between the photon rocket spacetimes and the Robinson - Trautman geometries. This allows a discussion of the issues related to the distinction between the gravitational and matter - energy radiation that appear in these metrics in a more geometrical way, taking full advantage of their asymptotic properties at null infinity to separate the Weyl and Ricci radiations, and to clearly establish their gravitational energy content. We also give the exact solution for the generalized photon rockets.

Another photon rocket

An axially symmetric Robinson - Trautman metric of Petrov type II is interpreted as referring to a rocket accelerated by the anisotropic emission of null fluid. The rocket loses no energy as gravitational radiation.

Photon rockets and gravitational radiation

The absence of gravitational radiation in Kinnersley's `photon rocket' solution of Einstein's equations is clarified by studying the mathematically well defined problem of point-like photon rockets in Minkowski space (i.e. massive particles emitting null fluid anisotropically and accelerating because of the recoil). We explicitly compute the (uniquely defined) linearized retarded gravitational waves emitted by such objects, which are the coherent superposition of the gravitational waves generated by the motion of the massive point-like rocket and of those generated by the energy--momentum distribution of the photon fluid. In the special case (corresponding to Kinnersley's solution) where the anisotropy of the photon emission is purely dipolar we find that the gravitational wave amplitude generated by the energy--momentum of the photons exactly cancels the usual 1/r gravitational wave amplitude generated by the accelerated motion of the rocket. More general photon anisotropies would, however, generate genuine gravitational radiation at infinity. Our explicit calculations show the compatibility between the non-radiative character of Kinnersley's solution and the currently used gravitational wave generation formalisms based on post-Minkowskian perturbation theory.

The photon rocket

There is an exact solution of Einstein's equations corresponding to a particle emitting null fluid anisotropically, and accelerating because of the recoil. I examine this solution and find no sign of emission of gravitational radiation. I give the Killing vectors of the metric, and some of the curvature invariants.

Feasibility study of the use of antimatter as a rocket propellant

W negative protons (p~) come into contact with regular protons (p), annihilation takes place and matter is converted into energy with the liberation of 2m0c, equal to 1876 Mev/event. This is equivalent to 3.86 X 10 Btu/lb or 6.7 X 10 times the energy released by burning a pound of a mixture of hydrogen and oxygen. The velocity of the ejected products (photons) is the speed of light, and the propellant thus becomes a potential one for a photon rocket. The specific impulse is about 30 X 10 sec. These glowing figures must be tempered by the recognition of the very difficult problems of production, storage, and use of such material. These items will be discussed from a feasibility standpoint to see what may be the limiting factors on production rates, storage concentrations and containment times possible in magnetic and electric fields, and propulsion efficiency and weight problems inherent in use.

On the mechanics of photon rockets in the general theory of relativity

Generally covariant equations of motion of a photon rocket comprising all the basic dynamic and thermodynamic processes are derived and are written for the case of a weak gravitational field. The equations lead to results which agree with those obtained by other means.

What an Astronaut Will See and Encounter When Flying at a Speed Approaching That of Light

In our t ime, when the most daring dreams about reaching cosmic space are coming true, when artificial satellites and cosmic rockets developed by man 's hands are penetrating the boundless distances of the solar system, human thought seeks for new, untested ways to conquer the cosmos. People not only dream, but begin to compute mathematically the possibilities of flying to other stars of our galaxy. How can we conquer the enormous distance separating us from even the nearest stars? The future astronaut will be able to bridge it during his lifetime only if his ship will move with a speed approaching tha t of light. The observer moving with a speed approaching tha t of light (relativistic speed), exists now on the pages of fantastic novels only. Although one writes about photon rockets there is yet no real basis for developing them. Will it ever be possible for a flight with relativistic speed to become a reality? The history of science and of technology convincingly proves tha t the most categorical n o cannot be applied to the future. What seems impossible today can become completely feasible tomorrow. But, even in our t ime and with the contemporary level of knowledge, one can foresee a part at least of the difficulties and obstacles which will be met and will have to be overcome by the future relativistic navigator to the stars. The motion involving relativistic speed hides several surprises which are discussed in this article.

Relativity and Space Travel

This paper treats in terms of the special theory of relativity: a "clock paradox" involving the fact that the frequency of an atomic oscillator on a moving body is lowered but the mass which is converted into radiation is increased; the case of the twin who goes on a space trip at near-light speed and returns younger than his brother on earth; the shift in frequency in the presence of a gravitational field; the clock rate on a satellite; the speed attainable by a photon rocket; and a space ship propelled by the energy of interstellar matter.