Whatever your thoughts on Rian Johnson’s 2017 "Star Wars: The Last Jedi", there is one scene that most agree is 'simply awesome'. Admiral Holdo, who stays behind on the rebel ship Raddus, launches the vessel at lightspeed into an enemy Star Destroyer, cutting it in half in a gorgeous black and white silhouette. It easily stands as one of the most beautiful shots in all of science fiction cinema, never mind just "Star Wars."
This sequence, while beautiful, might not be entirely accurate though. It isn’t a case of saying whether or not it's possible — it goes far deeper than that. In this instance, science suggests that the move would be even more destructive than the film shows. Interestingly, there is also some scientific precedent for what Holdo attempts in the film, as US military strategists have previously considered similar tactics.
What is the Holdo Maneuver in the movie?
At the end of "The Last Jedi," all seems lost for the rebel forces. After an escape plan goes wrong, the First Order manages to lock onto the plucky force’s location, and begin a relentless pursuit. As the remaining Rebel forces seek to escape the First Order’s looming Star Destroyer, it becomes very obvious that they are not going to make it. The Destroyer (named Supremacy in a stunning display of subtlety) is too fast, and would be able to easily capture the rebel escape ships.
However, the First Order did not count on Admiral Holdo staying behind in the larger rebel cruiser, the Raddus. As the other Rebels make their valiant escape, she turns the ship back to face the Star Destroyer, and launches it into lightspeed at the monolithic vessel. Part of the reason the First Order made such a good Star Wars villain was how unstoppable it seemed to be, and the Holdo Maneuver flew in the face of that (quite literally).
Has anyone tried this before?
Ultimately, the theory underlying the Holdo Maneuver is a simple one: it's a kamikaze move, but done at lightspeed. It's a military strategy that, while much older, found prominence in the Pacific Theater of World War 2. However, done at this scale, it packs enough potential energy to theoretically wipe out an Earth-sized planet.
Among science fiction circles, the Raddus would be called an RKKV — or Relativistic Kinetic Kill Vehicle. While this might sound incredibly imposing, all it really means is the use of a high speed object (sometimes a vehicle) and its associated kinetic energy as a makeshift missile.
Interestingly, an idea like the Holdo Maneuver was proposed years before "The Last Jedi." Before turning to work on award winning science fiction novels, Jerry Pournelle worked at Boeing, and formulated an idea called "Project Thor." While this mostly bears no similarity to the MCU's upcoming "Thor: Love and Thunder," its destructive capabilities are reminiscent of Mjolnir.
The idea was to launch telephone-pole sized tungsten projectiles from orbit to wreak tremendous damage against targets on the ground. Later, it was floated as part of Ronald Regan's real-life "Star Wars" program in the 1980s, renamed as Brilliant Pebbles. The most obvious difference between this and the kamikaze move is that Project Thor didn't involve loss of life for the aggressor.
Exactly How Powerful is the Holdo Maneuver?
This is where the science fantasy of "Star Wars" meets an inkling of science fact. To figure out the amount of energy that the impact of an object travelling at lightspeed would have, we need something called the Lorentz Factor. In equations, this is typically represented by the Greek symbol Gamma (ɣ).
This term handily expresses how much the measurements of time, length, and various other physical properties of an object change while moving. For the sake of argument, the Raddus was likely travelling just short of true lightspeed (the speed of light, designated "c," is 186,282 miles per second), so we'll call its speed 99.9% of c. While we'd like to be exact, we are dealing with science fiction as the source material here.
An object travelling at this speed has a Lorentz factor of 22.366. That tells us how much to multiply the kinetic energy of the object at relativistic speeds, to see how much energy it could theoretically have on impact. Einstein's formula for calculating relativistic kinetic energy can be expressed as E=(ɣ-1)mc2.
Interestingly, the Raddus is twice the canonical length of the series' iconic (and equally imposing) Star Destroyers. One of these vast vessels would weigh in at a whopping 4.44 billion kilograms (as per this handy Forbes estimation).
Assuming the Raddus is also twice the size of a classic Star Destroyer, that's then an eye-watering 8.88 billion kilograms (even though it's a fraction of the size of the First Order ship).
When all of these staggeringly large numbers are run through Einstein's equation, we see that the final kinetic energy of the Raddus as it impacted the Supremacy would be around 17x10 (to the power of 27) joules. For reference, the nuclear explosion at Hiroshima clocked in at just over 6x10 (to the power of 13) joules, according to official figures released by Project Ichiban in 1962. The bomb Little Boy's explosion at Hiroshima was five times hotter than the surface of the sun, which puts the colossal impact the Raddus would have into stark perspective.
While many aspects of the new sequels like Rey’s identity and the "forced" ending of "The Rise of Skywalker" are hotly debated, one thing is certain: The Holdo Maneuver would work, and it would likely do a lot more damage than fans saw in "The Last Jedi".
For an excellent video that approaches this question with similar methodology, it is worth checking out Kyle Hill's breakdown of the problem on YouTube here. His technique and use of Porg analogies is great, but his result differs slightly from ours (which you'll see below) thanks to different sources used for the Raddus' weight calculations and a different estimate of how fast the ship would be going.
Would the Holdo Maneuver look like that?
The science behind lightspeed shows how incredibly potent turning the Raddus into an RKKV would be. Relativistic Kinetic Kill Vehicles have such a foreboding name for several reasons. The "relativistic" element comes from how malleable mass, speed, and time all become when things are accelerated to the speed of light.
So, if the intended effect of the Holdo Maneuver is to cause damage, then it would most certainly do that. In the scene itself, we see the Raddus cut the Supremacy in two, then scatter and rend the entire fleet behind it into equally beautiful chunks of stardust.
One of the most terrifying parts of the RKKV concept is that anything that intercepted or blocked the vehicle would likely result in it splintering into numerous other projectiles, thanks to the principle of conservation of momentum. Although most of the kinetic energy would not be conserved in the impact, the momentum of all the shrapnel would be. These pieces would now be moving slightly slower than lightspeed, but would still be mostly as deadly, as we see in "The Last Jedi's" most beautiful moment.
We have actually seen a similar, but non-relativistic, example of this in Earth orbit. In 2007, China demonstrated an anti-satellite weapon that sent a missile slamming into a defunct weather satellite, destroying it.
The collision created a vast cloud of debris that continues to orbit Earth today. In 2013, a piece of that Chinese ASAT test debris apparently hit a small Russian satellite, changing its orbit and likely damaging it.