Based on our current understanding of physics, it is highly unlikely that humans will be able to travel at the speed of light in a spacecraft. According to 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 'c'. This implies that it would be prohibitively difficult, if not impossible, to accelerate a spacecraft with occupants to the speed of light.
Moreover, there are other challenges associated with traveling at such high speeds. Time dilation effects become significant as an object approaches the speed of light. For a spacecraft traveling close to 'c', time would pass more slowly relative to an observer on Earth. This would lead to significant time discrepancies, making it impractical for humans to travel to distant destinations at the speed of light and still return within a reasonable time frame.
That being said, scientists and researchers are constantly exploring new technologies and theories that may challenge our current understanding. Concepts like warp drives or wormholes are sometimes discussed in science fiction and speculative physics as potential means of faster-than-light travel. However, these ideas are highly theoretical and have not yet been proven scientifically or technologically feasible.
While we cannot rule out future discoveries and advancements that may revolutionize our understanding of physics and enable novel modes of travel, at present, it appears unlikely that humans will be able to travel at the speed of light in a spacecraft within the confines of our current scientific knowledge.