Project New Orion: Pulsed Nuclear Space Propulsion Using Photofission Activated by Ultra-Intense Laser

Project New Orion entails a pulsed nuclear space propulsion system that utilizes photofission through the implementation of an ultra-intense laser. The historical origins derive from the endeavors of Project Orion, which utilized thermonuclear devices to impart a considerable velocity increment on the respective spacecraft. The shear magnitude of Project Orion significantly detracts from the likelihood of progressive research development testing and evaluation. Project New Orion incorporates a more feasible pathway for the progressive research development testing and evaluation of the pulsed nuclear space propulsion system. Photofission through the application of an ultra-intense laser enables a much more controllable and scalable nuclear yield. The energy source for the ultra-intense laser is derived from a first stage liquid hydrogen and liquid oxygen chemical propulsion system. A portion of the thermal/kinetic energy of the rocket propulsive fluid is converted to electrical energy through a magneto-hydrodynamic generator with cryogenic propellant densification for facilitating the integral superconducting magnets. Fundamental analysis of Project New Orion demonstrates the capacity to impart a meaningful velocity increment through ultra-intense laser derived photofission on a small spacecraft.

A Methodology for Producing Uniform Distribution of UO2 in a Tungsten Matrix

We report a method to produce a uniform mixture of uranium dioxide spherical particles in a tungsten matrix. This method involves mixing 0.5 weight percent of high density polyethylene binder with 60 volume percent uranium dioxide spheres and 40 volume percent tungsten powders. Initially, hafnium oxide spheres were used as a surrogate for uranium dioxide spheres. The HfO2/W/PE powders were thoroughly mixed in a Turbula, then mixed on a hot plate above the drop point of the binder. These powders were then densified using spark plasma sintering. Microstructure was evaluated using scanning electron microscopy, density was measured and hardness measurements were made. Initial carbon content of the powders were measured and carbon content of the sintered materials was measured. Subsequently, W/UO2/Binder powders were mixed using the same methodology to ensure the process could be used for this system. These powders were sintered using hot isostatic pressing and microstructures evaluated. The resultant microstructures contained uniform distribution of HfO2 and UO2 particles in the tungsten matrix with very low carbon content.

Study of Space Reactors for Exploration Missions

Nuclear propulsion has been studied for many decades. The power density of nuclear fission is much higher than chemical process, and for missions to outer solar system requiring several hundred of kilowatts, or for flexible manned missions to Mars requiring several megawatts, nuclear electric propulsion might be the only option offering a reasonable mass in low earth orbit. Despite the existence of low power experiences--SNAP10 in the 60＇s or Buk/Topaz in the 60-80＇s--no high power reactor has been developed： investment cost, long term timeframe, high technological challenges and radioactive hazards are the main challenges we must overtake. However, it seems reasonable to look at the technical challenges that have to be overcome for a next generation of nuclear electric systems for space exploration. This paper will present some recent studies going on in France, on space reactors for exploration. Three classes of power have been considered： 10 kWe, 100 kWe, and several megawatts. Available data from previous studies and developments performed in Russia, USA, and Europe have been collected and gave us a large overview of potential technical solutions. This was the starting point of a trade-off analysis aiming at the selection of the best options, with regards to the technological readiness level in France and Europe. The resulting preliminary designs will be presented and critical technologies needing maturation activities will be highlighted.

Preparation of the highly dense ceramic-metal fuel particle with fine-grained tungsten layer by chemical vapor deposition for the application in nuclear thermal propulsion

The cermet fuel element was achieved by dispersing the UO_(2)particles with or without tungsten(W)coating layer uniformly in the W matrix.It is considered to be a robust and secure fuel for use in nuclear thermal propulsion in the near future.In this study,the effect of deposition temperature on the densification and grain refinement of the W coating layer was investigated.A high-density(19.24 g·cm^(-3))W layer with a uniform thickness(~10μm)and fine grains(~297 nm)was prepared by spouted-bed chemical vapor deposition.The prepared high-density,fine-grained W layer has the following advantages.It can prevent direct contact between fuel particles,resulting in a more uniform fuel distribution.In addition,it can decrease the reaction probability between the fuel kernel and H2,and prevent the release of fission products from the fuel kernel by extending the diffusion path at grain boundaries more efficiently.Moreover,the high-density,fine-grained W layer showed outstanding thermal and mechanical performance.Its average hardness and Young's modulus were approximately 7 and 200 GPa,respectively.The thermal conductivity of the W film was 101-124 W·m^(-1)·K^(-1)at 298-773 K.This work furthers our understanding of the potential application of the high-density,fine-grained W layer in nuclear thermal propulsion.

Mechanical property and thermal shock behavior of tungsten-yttria-stabilized zirconia cermet fabricated by spark plasma sintering

The cermet fuels have been considered as a potential key component for the nuclear thermal propulsion,and the homogeneity of the fuel particles in the metal matrix plays a crucial role in stabilizing the structure at extremely high temperatures.In this work,liquid paraffin was used as additive to improve the distribution of yttria-stabilized zirconia(YSZ,an appropriate surrogate for UO_(2) fuel)microspheres in the tungsten(W)matrix,and the W-YSZ cermet wafers(volume ratio 1:1)with a relative density of 97.6%were fabricated by spark plasma sintering with a specifically designed program.The effects of the paraffin dosage(0-5 wt.%)on the homogeneity,microstructure,mechanical properties,and the thermal conductivity of W-YSZ cermet were investigated.The W-YSZ sample with 2 wt.%paraffin shows the highest homogeneity and exhibits the best comprehensive properties,including the ultimate tensile strength of 132.2 MPa at 600℃,the bending strength of455 MPa and thermal conductivity of 50 W·m^(-1)·K^(-1)at room temperature.Moreover,the cermet could keep structurally sound after thermal shocked at a heat load of 20 MW·m^(-2).These results would be helpful for the design and optimization of the cermet fuels in the nuclear thermal propulsion.

On the stability of multicast flow aggregation in IP over optical network for IPTV delivery

The stable multicast flow aggregation （MFA） problem in internet protocol （IP） over optical network under the dynamical scenario is studied. Given an optical network topology, there is a set of head ends and access touters attached to the optical network, in which each head end can provide a set of programs （IP multicasting flows） and each access router requests a set of programs, we find a set of stable light-trees to accommodate the optimally aggregated multicast IP flows if the requests of access touters changed dynamically. We introduce a program correlation matrix to describe the preference of end users＇ requests. As the original MFA problem is NP-complete, a heuristic approach, named most correlated program first （MCPF）, is presented and compared with the extended least tree first （ELTF） algorithm which is topology- aware. Simulation results show that MCPF can achieve better performance than ELTF in terms of stability with negligible increment of network resource usage.