Q about relativistic mass increase, starship

[ContactLight]

A warning is often given that if one wants to have a spaceship traveling at relativistic speeds (usually to get to another star), the ship's mass increases, making acceleration more difficult. But if it where an antimatter propelled ship, with mass being turned into energy, then wouldn't the mass increase be offset by the increased energy released?

In other words, say you have a best case scenario: it's a positron-electron reaction, producing all gamma rays, which by then we know how to redirect and use, almost 100%, for forward propulsion. So all propellant mass is being turned into energy, almost all of which is being spent on forward propulsion. Isn't the propellant mass increasing, along with the whole ship's mass, and so the ratio of ship's mass to energy being released in the "combustion chamber" always the same?

 

[pervect]

No. The easiest way to see this is to not even use the concept of "relativistic mass". For detailed calculations, see for instance

http://math.ucr.edu/home/baez/physics/Relativity/SR/rocket.html

 

[Entropia]

This is a very interesting question and one that has been debated among physicists and engineers for quite some time. The concept of relativistic mass increase is a fundamental principle in Einstein's theory of relativity, which states that as an object's velocity approaches the speed of light, its mass increases. This increase in mass results in a higher amount of energy required to accelerate the object, making it more difficult to reach relativistic speeds.

However, your idea of using antimatter propulsion to offset the mass increase is a valid one. Antimatter reactions, such as positron-electron reactions, do release a tremendous amount of energy and can potentially provide enough thrust to counteract the increase in mass. In this scenario, the ratio of the ship's mass to the energy being released would remain constant, as you pointed out.

However, there are a few things to consider. Firstly, the technology to harness and control antimatter reactions is still in its infancy and is currently not feasible for practical use in space travel. Additionally, the amount of antimatter required for propulsion would be massive and extremely expensive to produce. It would also pose significant safety concerns, as even a small amount of antimatter coming into contact with regular matter could result in a catastrophic explosion.

Furthermore, even if we were able to overcome these challenges and use antimatter propulsion, the relativistic mass increase would still have an impact on the efficiency and speed of the ship. While it may help offset the increase in mass, it would not eliminate it entirely. The ship would still experience a significant increase in mass as it approaches relativistic speeds, making it more difficult to accelerate and requiring even more energy.

In conclusion, while your idea of using antimatter propulsion to offset the relativistic mass increase is intriguing, it is currently not a practical or feasible solution for interstellar travel. The concept of relativistic mass increase is a fundamental principle of physics, and while it may present challenges for space travel, it is something that we must take into account and work around in our pursuit of exploring the universe.