For the purposes of my story, seen here someone who went through a similar procedure involving parallel dimensions (see here), becomes nearly indestructible , invulnerable to damage related to excessive heat and fully capable of moving, reacting to stimuli and processing information at the speed of Mach 50 (61740 km/h or 17150 m/s). However, he is still subjected to the forces of air resistance and the consequences of moving at such speeds aren't mitigated or negated by any kind of external "magic" agent. In this situation, I'd like to know what exactly would happen to his environment if he moved at full speed.

In my first question regarding this topic, one of the answers spoke about causing sonic booms, shredding clothes of nearby humans and possibly causing the formation of plasma, but I couldn't find any source which gave me a more precise understanding of what would happen should a human-shaped object moved at speeds above the sound barrier, let alone at such a speed.

In a scenario in which the protagonist, weighing 70kg, being 2m tall and having a volume of approximately 0.062 cubic meters, travels in a straight line a distance of 17150 meters at his max speed of Mach 50 on an asphalt road (assume the road is fully contained within a plane horizontal to the ground) located at sea level (air density being approximately 1.2 kg per cubic meter). What exactly are the results of this human-shaped object (or approximately human shaped if that makes it easier to estimate) to his surroundings, especially regarding the sonic boom and the effects of said movement to the air around him?


-Assume the runner is indestructible, isn't touching the ground despite being infinitely close to it and/or is in a static position, should any of those assumptions help in a better estimate.

-While not necessarily the focus, a small description of how his movement would affect a human being wearing a tuxedo and an average 2 story building with normal glass windows, both at a 3 meter distance and perpendicular to his trajectory, would be greatly appreciated.

-if there's some kind of data lacking, please let me know, so that I may edit it in (I'm not sure exactly of what formula would render me the answer I want, or if there is such a formula).

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    $\begingroup$ For reference, a typical vehicle reentering from Earth orbit is traveling about Mach 25. At that scale, you have charming effects like a bow wave of charged plasma. Nothing close to the line of travel is going to have a good day. $\endgroup$
    – Cadence
    May 31, 2020 at 1:32
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    $\begingroup$ Obligatory XKCD $\endgroup$
    – JBH
    May 31, 2020 at 1:37
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    $\begingroup$ Well on earth he would not follow the curvature of the earth but launch themselves into space, mach 50 is well past escape velocity. $\endgroup$
    – John
    May 31, 2020 at 3:42
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    $\begingroup$ I remember a story by Stanely Schmidt where a modern jet plane was transported back in time to world War I. The pilot became friends with a freinchpilot who was shot down by a famous German pilot - call him the Crimson Count of something. So the jet pilot few to the airfield where the Crimson Count's squadron was parked and swooped down low at high speed, and all of the WWI biplanes were smashed by the wake of the jet's passage. $\endgroup$ May 31, 2020 at 17:45
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    $\begingroup$ @catsteevens well that'll disappoint you, my character is capable of some degree of shape-shifting (another reason why human(oid) was the term I used), so as he's mimicking clothing with his skin I didn't have to worry about that (bday suit). Your case seems to be a bit above the 1200 m/s case. Considering the sound barrier is lower at higher altitudes, your alien suit should do just fine if it can already withstand the effects of going at 4000 mph at sea level. $\endgroup$ May 31, 2020 at 21:41

1 Answer 1


Nothing good

Let's have a look at a few data points along the way to the impossible humanoid:

  • 343 m/s (approx.) supersonic flyby of F/A-18 Hornet in Mythbusters episode to test if sonic boom will break glass. Glass was broken in a pass at 200 feet (60 m) above a test shed.
  • 1200 m/s was the muzzle velocity of the British Ordnance QF 17-pounder, which fired a 3 inch (76.2 mm diameter) projectile. In a discussion on muzzle brakes here, from 17:50-20:08, Lloyd (aka Lindybeige) is reading a passage from a book where the muzzle blast from one of these guns is rocking a friendly tank and disorienting the crew that is some distance away next to it.
  • 7700 m/s was the speed of a Space Shuttle about to commence atmospheric entry. However, a Space Shuttle was doing this speed in the upper reaches of the atmosphere where air is much thinner and the speed of sound is lower. At this speed air cannot move quickly enough to flow out of the way of an object, instead it is compressed to plasma. Re-entry vehicles typically have blunt noses to trap a layer of air in front of them that insulates them from the plasma shockwave (as per the linked article), but even with this protection the skin of a shuttle reached temperatures of around 1500 C.
  • 8092 m/s is the velocity of detonation (VoD) of C-4.
  • 17150 m/s is Mach 50 at sea level, the stated speed of the protagonist in the question.

Let us just think of this in comparison with the C-4 VoD given. When a block of C-4 detonates, it creates a shockwave in all directions. However, unless there are reflective effects, the only shockwave that matters to a victim or inanimate target is the part that is going in their direction. So we can treat the shockwave resulting from the protagonist's motion as being like the blast from C-4.

It's a lot of C-4. If we rather conservatively assume that the skinny protagonist has a height of 2m and an average frontal width of 0.3 m then this gives a frontal area of 0.6 m. This is about the same as a cube of C-4 with each side being 77 cm long, which works out to about 785 kg of C-4.

In the military, I was never on a range that allowed more than 80 kg of high explosive to be detonated simultaneously.

Actually, it's much worse than that. One reason is because the protagonist is travelling at twice the VoD of C-4 and kinetic energy is equal to velocity squared, so it will be 4 times worse. The other is that I have no idea how to calculate the damage resulting from the implosion in the protagonist's backtrail as the vacuum behind him is filled.

So, ignoring vortex effects in the backtrail, every point along the protagonist's path is getting hit with the equivalent of 3 tons of high explosive. Regarding the human in the tuxedo - practically atomised. Depending on the durability of the 2 storey building it may be recognisable as once having been a building but it is effectively destroyed.

  • $\begingroup$ I'm not convinced by your C-4 calculations - the block of explosive does not remain as a solid cube when explodes, but turns into a gas with a much larger volume - but otherwise I agree. (+1) $\endgroup$
    – Rekesoft
    Jun 1, 2020 at 10:21

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