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Projections for the earliest interstellar mission possibilities are calculated based on 27 years of data on historic energy trends, societal priorities, required mission energy, and the implications of the Incessant Obsolescence Postulate…
A technique by which a spacecraft can interact with flows of ionized gas in space (the solar wind or interstellar medium) to be accelerated to velocities greater than the wind velocity is explored. Inspired by the dynamic soaring maneuvers…
Advanced civilizations capable of interstellar travel, if they exist, are likely to have advanced propulsion methods. Spaceships moving at high speeds would leave a particular signature which could be detected from Earth. We propose a…
We derive the covariant optimality conditions for rocket trajectories in general relativity, with and without a bound on the magnitude of the proper acceleration. The resulting theory is then applied to solve two specific problems: the…
Recent observations of the luminosity-redshift in Type Ia supernovae suggest an accelerated inflation of the Universe (open Universe) as well as the observed matter density showed to be less than the critical one, suggesting that a large…
In this paper we look at the ultimate limits of a photon propulsion rocket. The maximum velocity for a photon propulsion rocket is just below the speed of light and is a function of the reduced Compton wavelength of the heaviest subatomic…
The paper shows that, conceptually and operationally, the speed of light as measured locally in the inertial comoving frame of a point on the rim of a rotating disk, is different from the one measured globally for a round trip along the…
Neutron stars are compact objects rotating at high speed, up to a substantial fraction of the speed of light (up to 20\% for millisecond pulsars) and possessing ultra-strong electromagnetic fields (close to and sometimes above the quantum…
Interest in the exploration of, and the establishment of a human settlement, on Mars is rapidly growing. To achieve this, rapid transit will be required to bring crucial cargo. Current missions to Mars take 150 days, which would be too long…
It is widely believed that the cosmological redshift is not a Doppler shift. However, Bunn & Hogg have recently pointed out that to settle properly this problem, one has to transport parallelly the velocity four-vector of a distant galaxy…
The inverse problem of cosmic ray transport of ultra-high energy cosmic rays is considered. The analysis of Auger data on energy spectrum, energy dependence of mean logarithm of atomic mass number and its variance allows definite…
Stars and their winds can contribute to the non-thermal (NT) emission in extragalactic jets. Given the complexity of jet-star interactions, the properties of the resulting emission are strongly linked to those of the emitting flows. We…
A black hole can launch a powerful relativistic jet after it tidally disrupts a star. If this jet fortuitously aligns with our line of sight, the overall brightness is Doppler boosted by several orders of magnitude. Consequently, such…
Propellantless propulsion refers to methods of space travel that do not require onboard propellant, instead relying on natural forces or external energy sources. In this paper, I review different approaches that have been explored and…
Radial Velocity follow-up is essential to establish or exclude the planetary nature of a transiting companion as well as to accurately determine its mass. Here we present some elements of an efficient Doppler follow-up strategy, based on…
A puzzling feature of the {\it Chandra}--detected quasar jets is that their X-ray emission decreases faster along the jet than their radio emission, resulting to an outward increasing radio to X-ray ratio. In some sources this behavior is…
We consider a nearly free falling Earth satellite where atomic wave interferometers are tied to a telescope pointing towards a faraway star. They measure the acceleration and the rotation relatively to the local inertial frame. We calculate…
Many of the planets discovered via the radial velocity technique are hot Jupiters in 3-5 day orbits with ~10$% chance of transiting their parent star. However, radial velocity surveys for extra-solar planets generally require substantial…
This paper discusses the physics, engineering and mission architecture relating to a gram-sized interstellar probe propelled by a laser beam. The objectives are to design a fly-by mission to Alpha Centauri with a total mission duration of…
Nature succeeds in accelerating extended and massive objects to relativistic velocities. Jets in Active Galactic Nuclei and in galactic superluminal sources and gamma-ray bursts fireballs have bulk Lorentz factors from a few to several…