Speed limit on earth

[Curious layman]

Apologies if this is in the wrong space, I wasn't sure if this should be in engineering or physics.

Is there a limit to how fast we can fly through the air. For example, will we one day have planes that can fly at mach 50?

[zapatos]

In physics, I would say that the limit is c.

[Janus]

Spacecraft during re-entry only get up to ~ mach 25, and even at that speed, the air is heated to a plasma state.  Craft like Apollo and Soyuz use ablative shields that burn off to deal with it. And this is in the upper part of the atmosphere, where the air density is very low.

[Curious layman]

26 minutes ago, Janus said:

Spacecraft during re-entry only get up to ~ mach 25, and even at that speed, the air is heated to a plasma state.  Craft like Apollo and Soyuz use ablative shields that burn off to deal with it. And this is in the upper part of the atmosphere, where the air density is very low.

So it's more of a material science problem then, and fuel too probably.

Does science know the limits for heat resistance in materials, in the same way we know what the limits are for energy capacity for batteries?

34 minutes ago, zapatos said:

In physics, I would say that the limit is c.

Yes, but not through earths atmosphere in a plane though. Makes me think of the relativistic baseball. Lol.

[koti]

36 minutes ago, Curious layman said:

So it's more of a material science problem then, and fuel too probably.

Does science know the limits for heat resistance in materials, in the same way we know what the limits are for energy capacity for batteries?

All materials have their limits, ceramic plates like the ones used on the outside of the Space Shuttle or ceramic car brake rotors in performance cars will eventually vapourize in high enough temperatures. Air resistence would require you to use enormous amounts of fuel/power to propell something to Mach50 in Eatrhs atmosphere, that is if the construction of a your plane would even withstand the huge pressure (it wouldn't) Thats the reason why fast spy planes fly at high altitudes - less fuel needed at high speeds, less air resistence. 

[Phi for All]

1 hour ago, zapatos said:

In physics, I would say that the limit is c.

I, for one, would like to hear Janus do the explanation of what happens at a baseball game where the pitcher tries to throw a "fastball" at the speed of light. 

[koti]

2 minutes ago, Phi for All said:

I, for one, would like to hear Janus do the explanation of what happens at a baseball game where the pitcher tries to throw a "fastball" at the speed of light. 

Friction included or excluded?   

[Phi for All]

1 minute ago, koti said:

Friction included or excluded?   

The title says, "On Earth". Excluded would be off-topic.

[koti]

7 minutes ago, Phi for All said:

The title says, "On Earth". Excluded would be off-topic.

Not many people could but I bet Janus could do it.

[MigL]

The fact that a re-entry vehicle is trying to slow down, and so presents a 'blunt' face to the atmosphere, is where most of the heating comes from.
A 'streamlined' re-entry vehicle would hit the ground at thousands of miles per hour; the space shuttle re-enters bottom first to generate 'slow-down' drag, and the reason ablative tiles are attached to bottom surfaces.

 

Edited October 24, 2020 by MigL

[Curious layman]

Just wondering, if I was traveling at Mach 50, would the g-force  kill me?

[koti]

1 minute ago, Curious layman said:

Just wondering, if I was traveling at Mach 50, would the g-force  kill me?

You wouldn't feel any difference from standing still.

[MigL]

8 minutes ago, Curious layman said:

Just wondering, if I was traveling at Mach 50, would the g-force  kill me?

No, but how you come to a stop might.
( falling off a building never killed anyone; it's that darned landing that does )

Edited October 24, 2020 by MigL

[J.C.MacSwell]

4 hours ago, koti said:

Not many people could but I bet Janus could do it.

I hear he has quite an arm...

[Halc]

Are the requirements such that the object moving has to A) maintain its speed,  B) be self propelled and air-propelled, and C) survive the event.

If A) is a requirement, the shuttle coming in doesn't count since it is slowing down, as is a meteor coming in at mach 100.

If B) is a requirement (probably the most interesting question), then it becomes a question of how much thrust you can generate in a medium using that medium for reaction mass. This is reminiscent of my favorite Bonneville event: Fastest wheel-powered vehicle, far more challenging than simply strapping a cockpit and skateboard to a missile.

If C) is a requirement, the meteor is out. This seems a reasonable requirement since anybody can just go out in space, come back and skim the atmosphere at 0.5c.  Earth might even survive a graze like that.

Related question I've posed to the dinner table: How fast must a ping-pong ball come in from space to destroy a submarine at 100m depth? (We have interesting dinner table conversations)

[Phi for All]

16 hours ago, MigL said:

No, but how you come to a stop might.

As well as how quickly he got up to Mach 50. And by what means (if he had no aircraft to protect him, would the air smash him before the acceleration did?).

[Sensei]

18 hours ago, MigL said:

No, but how you come to a stop might.

Rapid acceleration or deceleration can kill even without hitting anything. Brain is not attached to the skull very tightly and will smash on skull wall, cause fatal injury, internal bleeding and brain swelling. The first symptom of too high acceleration is shortened field of view with black areas on sides. Later lost of consciousness. Airplane pilots and astronauts are training to learn how to fight with it to some level.

Quote

( falling off a building never killed anyone; it's that darned landing that does )

Some people could have heartattack during flight to the ground..

Edited October 25, 2020 by Sensei

[John Cuthber]

21 hours ago, Curious layman said:

Is there a limit to how fast we can fly through the air.

The usual limit is money.

[Sensei]

Quote

Speed limit on earth

BTW, hyperloop and similar are not limited by air resistance as they work in vacuum or very low pressure.

https://en.m.wikipedia.org/wiki/Hyperloop

 

Edited October 25, 2020 by Sensei

[MigL]

1 hour ago, Sensei said:

Rapid acceleration or deceleration can kill even without hitting anything.

That's right.
The Northrop F-20 Tigershark, a development of the F-5 and T-38, was involved in two crashes during development/sales tours, which were effectively caused by aggressive maneuvering ( sustained 9g ). This caused the pilots, Cornell and Barnes, to gradually lose peripheral vision until blackout; neither of themsurvived the crashes.
Cornell died during a demonstration in Taiwan.
Barnes died practicing an air show routine here in Canada.

https://nationalinterest.org/blog/buzz/video-alert-watch-unfortunate-f-20-tigershark-first-prototype-crash-68937
https://www.latimes.com/archives/la-xpm-1985-05-15-mn-8541-story.html

[CharonY]

On 10/24/2020 at 2:29 PM, Curious layman said:

Makes me think of the relativistic baseball. Lol.

The XKCD one? https://what-if.xkcd.com/1/