Traveling at or near the speed of light is currently beyond our technological capabilities and understanding of physics. According to our current understanding of the universe, objects with mass cannot reach or exceed the speed of light due to the theory of relativity, specifically Einstein's theory of special relativity.
As an object with mass accelerates towards the speed of light, its relativistic mass increases, requiring an infinite amount of energy to reach the speed of light. This means that the energy requirements to propel a spacecraft to such speeds would be astronomical and currently impossible to achieve with any known energy source.
Additionally, there are various other challenges associated with high-speed space travel, such as:
Energy requirements: As mentioned, immense amounts of energy would be necessary to accelerate a spacecraft to relativistic speeds. Currently, we do not have any known energy sources capable of providing such levels of energy efficiency.
Propulsion technology: We would need to develop propulsion systems that could generate thrust and acceleration on the spacecraft without being limited by the mass-energy relationship of relativity. Hypothetical technologies like antimatter propulsion or advanced fusion propulsion have been proposed, but they are still in the realm of speculative theory.
Structural integrity: At extremely high speeds, collisions with even small particles in space could be catastrophic. The impact of interstellar dust and debris at relativistic velocities could release enormous amounts of energy, endangering the spacecraft and crew. Finding effective shielding mechanisms or developing advanced navigation systems to avoid collisions would be crucial.
Time dilation: As an object approaches the speed of light, time dilation occurs, meaning time moves slower for the moving object compared to a stationary observer. This would have significant implications for crewed missions, as time dilation could result in vast time disparities between the travelers and those on Earth.
Regarding the cost and materials, it is impossible to provide an accurate estimation because the technology required for near-light-speed travel is purely speculative at this point. The research, development, and construction of such a spacecraft would likely require advancements in multiple scientific disciplines and likely involve an astronomical cost that is difficult to quantify.
It's worth mentioning that there are ongoing scientific studies and discussions regarding interstellar travel concepts, such as the concept of relativistic interstellar spacecraft. However, these concepts remain highly theoretical and far from practical implementation.
In summary, while space travel at or near the speed of light is a fascinating idea in science fiction, the current understanding of physics and our technological capabilities suggest that achieving such velocities is not feasible with our current knowledge and resources.