Planck photon rocket drives --- which in theory could hit velocities equal to 99.999 percent the speed of light --- might eventually offer propulsion engineers a way to drastically reduce interstellar travel times without trashing the laws of physics as we currently understand them. A hypothetical photon rocket’s directional thrust would come from photons (or electromagnetic radiation in the form of light) and turn a one-way journey to Mars into a three-minute and four second trip.
In a forthcoming paper in the journal Acta Astronautica, a Norwegian professor argues that the theoretical ultimate speed limit of any spacecraft falls just below lightspeed in a vacuum, or 186,282 miles per second But that's also still considerably beyond the limits of what can currently be achieved in today's particle accelerators.
“The fuel is converted into light which leads to radiation pressure that drives the rocket forward ,” said Haug, who teaches quantitative finance at the Norwegian University of Life Sciences. He admits that’s an unconventional background for rocket science but says a lot of the math used in contemporary physics directly overlaps with finance option theory, so photon rockets are not that much of a stretch.
Haug used such math to combine contemporary conventional rocket theory with the theories of the pioneering theoretical physicist Max Planck’s work on the nature of fundamental mass, length and time intervals. Using these calculations, in his paper, Haug shows that in theory two Planck masses of fuel would be needed for every fundamental particle in a rocket’s payload. (One Planck mass is theorized to have about the same mass as a flea egg.)
“Laboratory experiments show that the concept of driving an object forward by using only photons is clearly possible,” said Haug. “But there is still a long way to go in developing large photon rockets that could send materials or people into outer space.”
Haug speculates that any given fundamental particle should in theory turn into a hypothetical Planck mass particle as soon as it reaches its maximum velocity. Theorized to be micro-sized black holes by some physicists, including Stephen Hawking, Planck mass particles are thought to be more massive than any known observed fundamental particle, but as yet have never been detected. Some theorists reason they may have been prevalent in the first moments after the cosmological Big Bang.
But in Haug’s theory, such Planck mass particles would be generated basically at the instant two photons collide. However, just as quickly, these particles disappear after dissolving into energy.
Haug says the fuel for such a rocket could take any form as long as its technology allowed for 100 percent conversion into light energy, where all of the fuel’s mass could be converted for directional thrust.
As for faster than light travel?
Even large space rockets must ultimately follow the ‘’laws” of subatomic particles, says Haug.
“If no subatomic particle can move faster than my derivations predict, then this must also be the absolute maximum speed limit for a rocket,” said Haug.
But hopes of testing his theory in the near term are pretty slim, he says. That would require particle accelerators far stronger than Europe’s Large Hadron Collider (LHC).
As for making quick trips to Mars?
At this stage, it’s unrealistic to think about full-scale spacecraft traveling at velocities a tiny fraction below lightspeed itself, says Haug. The technology might best be used to enable travel at a fraction of the speed of light --- still much faster than current feasible velocities.
What would photon rockets ultimately do for launch costs?
If one really were able to build rocket propulsion technology where almost all of the fuel mass was converted to energy, he says, this would dramatically reduce the need for large fuel payloads and launch costs.
But Haug says this would also require a major breakthrough in particle physics.