Aerodynamics.

[F.W 5,734]

Its great on here apart from our liking of peeing,we manage to have the occasional scientific discussion.

I was watching an aircraft flying over today,and couldnt help thinking,what limits the speed that such large planes can fly?Is there any reason a 737 couldnt fly at Mach 2 for instance?Or what is likely to be the fastest ever aircraft that mankind could in theory build?There must be a kind of ratio of weight of aircraft vs size of engine etc.

What IS the fastest ever manmade machine,or rocket etc?I guess things like bullets move at thousands of feet per second,but not machines.

[Guest UnabashedUser]

Looks like Mach 6

Ramjets work most efficiently at supersonic speeds around Mach 3 (2,300 mph; 3,700 km/h). This type of engine can operate up to speeds of Mach 6 (4,600 mph; 7,400 km/h).

https://en.wikipedia.org/wiki/Ramjet

[Scot_Lover 1,876]

ISS?

Admittedly, it has the aerodynamics of a brick, but it still manages 24,000 kph, completes an orbit of our planet every 90 min.

[gldenwetgoose 21,487]

To answer the first half of your question, the as Newton observed, for every force there is an equal and opposite reaction - so as an aircraft travels forward, aerodynamic drag tries to slow it down. Hence to keep it in flight we have to provide thrust.

So to make if fly faster, we just apply more thrust. The problems are though, that all that thrust needs fuel, and also the air in the atmosphere dragging past the aeroplane causes friction, which results in a build up of heat.  So making a plane fly faster is a combination of making it less 'draggy' or more aerodynamic, and giving it more powerful but fuel efficient engines.  Concorde did that amazingly well for a 1970's product, but only had a very low passenger capacity and high operating costs.  These days the commercial drive is less on the speed aspects (business is all done online), it's more on the bulk transportation of people. Hence there hasn't been the commercial drive to increase speed.

There has been the commercial drive to reduce operating costs and environmental impact - today's engines are far more fuel efficient but not suited to higher speed operation.

[steve25805 126,015]

The fastest ever man made object is the Juno space probe which used the slingshot effect of the Earth's gravity to accelerate it to a speed in excess of 165,000 mph, 25 miles per second. 

That is 50 times faster than a bullet, and could get you from the UK to Australia in under 8 minutes.

[gldenwetgoose 21,487]

Don’t want to be pedantic- but as soon as an object gets outside the Earth’s atmosphere then aerodynamics cease to apply....  makes things a whole lot easier (from one aspect). 

[Scot_Lover 1,876]

7 hours ago, gldenwetgoose said:

Don’t want to be pedantic- but as soon as an object gets outside the Earth’s atmosphere then aerodynamics cease to apply....  makes things a whole lot easier (from one aspect). 

I know, but the question was the fastest man made object, lol. That's what I responded to, ISS is currently the fastest thing we've made that carries passengers. All bets are off when someone goes to Mars, though.

[2prnot2p 1,066]

I do know that the fastest plane ever made was the old SR-71 Blackbird spy plane that the U.S. military used to fly.  They retired it some years back.  The military never told how fast it could go, or how high, but they did wear space suits to fly it.  Whenever a record was set, they'd go up with the Blackbird and break it.  It carried no weapons and would fly right over Moscow and take pictures.  It was so fast and flew so high that there was no chance that the Soviets could ever shoot it down.  I once read that it flew at about 100,000 feet in altitude.  That's amazing!

I think the advancement in satellites combined with the high cost prompted the U.S. to retire it.  It's too bad.  It was such a cool plane.  My son used to have a photo of it on his wall when he was a kid.  Fond memories, for sure.

 

Edited February 16, 2019 by 2prnot2p

[2prnot2p 1,066]

I just read up on the SR-71.  It seems that officially it hit Mach 3.2, but an insider said he was onboard when it hit Mach 3.5.  That is fast! 

Also, I read that the U.S. military is going to focus on unmanned drones for spying now.  But, there's also work being done on the Blackbird's replacement.  I have to believe they're already using one.  It was retired in 1999 and I can't see them going 20 years without a manned spy plane.  They tell us only what they want to tell us, right?  LOL!

[gldenwetgoose 21,487]

I'll give you that one @Scot_Lover - fair enough. 😉

 

[spywareonya 37,961]

I think @F.W asked about Flying propelled intra-atmosphere stuff

Like airplanes

I think it's indeed the ramjet like @UnabashedUser said

[speedy3471 10,655]

On 2/15/2019 at 11:54 PM, 2prnot2p said:

I just read up on the SR-71.  It seems that officially it hit Mach 3.2, but an insider said he was onboard when it hit Mach 3.5.  That is fast! 

Also, I read that the U.S. military is going to focus on unmanned drones for spying now.  But, there's also work being done on the Blackbird's replacement.  I have to believe they're already using one.  It was retired in 1999 and I can't see them going 20 years without a manned spy plane.  They tell us only what they want to tell us, right?  LOL!

The CIA also stole the titanium used to make that wonderful aircraft from the USSR.

[2prnot2p 1,066]

1 hour ago, speedy3471 said:

The CIA also stole the titanium used to make that wonderful aircraft from the USSR.

They did?  Please, do tell more!

[speedy3471 10,655]

23 minutes ago, 2prnot2p said:

They did?  Please, do tell more!

I believe 90% of the air frame is made out of titanium. The USA didn't have enough so thru third world countries and shell companies they acquired it from the USSR. 

Iam sure the whole thing is still highly classified. I read about that somewhere. The aircraft leaked fuel while on the ground. Once airborne and at cruising speed the heat from friction sealed her up. 

[2prnot2p 1,066]

2 minutes ago, speedy3471 said:

I believe 90% of the air frame is made out of titanium. The USA didn't have enough so thru third world countries and shell companies they acquired it from the USSR. 

Iam sure the whole thing is still highly classified. I read about that somewhere. The aircraft leaked fuel while on the ground. Once airborne and at cruising speed the heat from friction sealed her up. 

Pretty clever!

[speedy3471 10,655]

Just now, 2prnot2p said:

Pretty clever!

Absolutely lol. It could fly higher and faster than any other interceptor it was likely to encounter. Iam sure it would be able to run from SAM's as well. Provided it picked up the missiles soon enough on radar 

[likesToLick 10,216]

On 2/16/2019 at 4:24 PM, 2prnot2p said:

I have to believe they're already using one.  It was retired in 1999 and I can't see them going 20 years without a manned spy plane. 

Today satellites can probably do all of the intelligence gathering that was once done by spy planes.

[likesToLick 10,216]

On 2/15/2019 at 5:37 AM, F.W said:

Is there any reason a 737 couldnt fly at Mach 2 for instance?

Airframes are designed for a particular maximum operating speed and not more.  On 737s this is somewhere around 350 knots I think.  If you put a 737 into a dive and exceeded this speed,  things would begin to go wrong.  Probably the first thing to happen is that control surfaces would begin to flutter and the aircraft would no longer respond to controls.  If it continued to increase speed after this,  parts of the aircraft structure would begin to deform and eventually break.  For example,  the engine pylons might possibly bend and then break free from the wings.

Aircraft are built only as strong as they need to be to fly the mission they are designed for.  Any extra strength would make the plane heavier,  and it would then have to carry fewer passengers or less fuel.  Plane makers go to a lot of trouble to make them as light as possible,  and just, barely, strong enough for safety.

So,  I would guess that most likely a 737 would be badly damaged before its speed even reached mach 1.