Giorgio Fontana

Gravitational sensor for LISA and its technology demonstration mission

We describe the current design of the European gravitational sensor (GS) for the LISA Technology Package (LTP) that, on board the mission SMART-2, aims to demonstrate geodetic motion within one order of magnitude of the anticipated LISA performance. We report also the development of a noise model used in assessing the performance and determining the feasibility of achieving the overall noise goals for the GS. This analysis includes environmental effects that will be present in the sensor. Finally, we discuss open questions regarding the GS for LTP and LISA, ground testing, and verification issues.

Gravitational Wave Propulsion

There is only one experimental proof that gravitational waves exist. With such a limitation, it may seem premature to suggest the possibility that gravitational waves can became a preferred space propulsion technique. The present understanding of the problem indicates that this is not the case. The emission of gravitational waves from astrophysical sources has been confirmed by observation, the respective detection at large distance from the source is difficult and actually we have no confirmation of a successful detection. Therefore the required preliminary discovery has been already made. This opinion is enforced by many different proposals for building the required powerful gravitational wave generators that have recently appeared in the literature and discussed at conferences. It is no longer reasonable to wait for additional confirmation of the existence of gravitational waves to start a program for building generators and testing their possible application to space travel. A vast literature shows that gravitational waves can be employed for space propulsion. Gravitational wave rockets have been proposed, non‐linearity of Einstein equations allows the conversion of gravitational waves to a static gravitational field and “artificial gravity assist” may become a new way of travelling in space‐time. Different approaches to gravitational wave propulsion are reviewed and compared. Gravitational wave propulsion is also compared to traditional rocket propulsion and an undeniable advantage can be demonstrated in terms of efficiency and performance. Testing the predictions will require gravitational wave generators with high power and wavelength short enough for producing high energy densities. Detectors designed for the specific application must be developed, taking into account that non‐linearity effects are expected. The study and development of Gravitational wave propulsion is a very challenging endeavor, involving the most complex theories, sophisticated materials and testing techniques ever conceived by science. The development of Gravitational wave propulsion appears to be within the reach of a large national or a worldwide research program.

Transport of an ion beam through an octopole guide operating in the R.F.-only mode

Abstract Transport of an ion beam through an octopole guide operating in the r.f.-only mode has been investigated both experimentally and by ion trajectory calculations. The octopole transmission band has been characterized by two limit values of the r.f.-potential. The dependence of these limits on the characteristic energy e (e = 1 8 π2mf2R20, where m is ion mass, f is frequency and R0 is octopole free radius) has been studied considering different configurations of the ion guide.

A methodology for power consumption evaluation of wireless sensor networks

Energy consumption is one of the most constraining requirements for the design and implementation of wireless sensor networks. Simulation tools allow one to significantly decrease the effort and time spent to choose the right solution. Existing simulators provide varying degrees of analysis for communication, application and energy domains. However, they do not provide enough flexibility to estimate the consumed power for a wide range of wireless sensor network (WSN) hardware (HW) platforms. In this paper we present a flexible and extensible simulation framework to estimate power consumption of sensor network applications for arbitrary HW platforms. This framework allows designers of sensor networks to estimate power consumption of the explored HW platform which permits the selection of an optimal HW solution and software (SW) implementation for the desired projects.

Scalable Fractional Lambda Switching: A Testbed

This paper presents experiments on a testbed based on ultra-scalable switches realized using off-the-shelf optical and electronic components. The scalability of this switching architecture, a direct outcome of the deployment of pipeline forwarding, results-in addition to much lower cost-in the need for a smaller amount of components, and, consequently, lower power dissipation, which is key to a “greening” of the Internet. Although an all-optical architecture is demonstrated, we reached the conclusion that, given the current state of the art, a hybrid electro-optical architecture is the “best-of-breed” switch solution.

Design of a Quantum Source of High‐Frequency Gravitational Waves (HFGW) and Test Methodology

The generation of High‐Frequency Gravitational Waves (HFGW) has been identified as the required breakthrough that will lead to new forms of space propulsion. Many techniques have been devised to generate HFGW, but most of them exhibit marginal efficiency, therefore the power emitted in form of gravitational waves (GW) is orders of magnitude lower than the input power. The gravitational wave counterpart of the LASER, termed Gravitational‐wave LASER or “GASER” is the quantum approach to the efficient generation of gravitational waves. Electrons, protons, muons, etc, all have charge and mass, if accelerated they usually lose energy through the very fast electric and magnetic channels, this causes a negligible emission through the gravitational channel. Quantum systems can be engineered to forbid electric and magnetic transitions, therefore the gravitational spin‐2 transitions can take place. A class of active materials, suitable for making a GASER based on electronic transitions in the solid state, is identi...

Generation of Gravitational Waves with Nuclear Reactions

The problem of efficient generation of High Frequency Gravitational Waves (HFGWs) and pulses of Gravitational Radiation might find a reasonably simple solution by employing nuclear matter, especially isomers. A fissioning isomer not only rotates at extremely high frequency (∼ 3.03×1024 s−1), but is also highly deformed in the first stages of fission (the nucleus is rotating and made asymmetric “before” fission). Thus one achieves significant impulsive forces (e.g., 3.67×108 N) acting over extremely short time spans (e.g., 3.3×10−22 s). Alternatively, a pulsed particle beam, which could include antimatter, could trigger nuclear reactions and build up a coherent GW as the particles move through a target mass. The usual difficulty with HFGWs generated by nuclear reactions is the small dimensions of their nuclear‐reaction volumes, that is, the small moment of inertia and submicroscopic radii of gyration (e.g., 10−16 m) of the nuclear‐mass system. Such a difficulty is overcome by utilizing clusters of nuclear ...

Progress in the development of a position sensor for LISA drag-free control

We report on progress in the development of free-falling moving test-masses for LISA and for the related technology demonstration mission. We present simple formulae to evaluate the performance of the device as a function of the various design parameters, and we compare them with preliminary experimental results from a test prototype we are developing. Quantitative agreement is found. Finally, we present a control law, along with a performance simulation, for low-frequency electrostatic suspension of the test-mass with minimal perturbation of the motion within the measuring frequency band.

Gravitational radiation and its application to space travel

Gravitational radiation is an elusive form of radiation predicted by general relativity, it is the subject of intense theoretical and experimental research at the limit of the sensitivity of today’s instrumentation. In spite of the fact that no direct evidence of this radiation now exist, observed astrophysical phenomena have given convincing proofs of its existence. Theories predict that gravitational radiation may also be employed for propulsion, moreover the nonlinear behavior of spacetime may permit the generation of spacetime singularities with colliding beams of gravitational radiation, this phenomenon could become a form of propellantless propulsion. Both applications would require gravitational wave generators with high power and appropriate optical properties. Among the proposed techniques that could be applicable to the production of gravitational waves, a promising one is the possible emission of gravitons by quantum systems. A hypothesis describing the production of gravitons in s-wave/d-wave ...

Effect of the Vacuum Energy Density on Graviton Propagation

It is known that the value L of the vacuum energy density affects the propagation equation for gravitons: A mass term appears in the propagation equation, such that m^2=-L. As a consequence, the polarization states of gravitons also change. This effect of the L-term has been confirmed by recent calculations in a curved background, which is the only proper setting, since solutions of the classical Einstein equations in the presence of a L-term represent a space with constant curvature. A real value for the mass (when L 0) are still unclear; on general grounds, one can expect the onset of instabilities in this case. This is also confirmed by numerical simulations of quantum gravity which became recently available. These properties gain a special interest in consideration of the following. (1) The most recent cosmological data indicate that L is positive and of the order of 0.1 J/m^3. Is this value compatible with a stable propagation of gravitons? (2) The answer to the previous question lies perhaps in the scale dependence of the effective value of L. L may be negative at the small distance/large energy scale at which the quantum behavior of gravitational fields and waves becomes relevant. Furthermore, local contributions to the vacuum energy density (in superconductors in certain states, and in very strong static electromagnetic fields) can change locally the sign of L, and so affect locally the propagation and the properties of gravitons. The graviton wavefunction, for different values of the parameters, may be characterized by superluminal phase velocity or by unitarity only in imaginary valued time.