What About This...?

  NIGEY 20:22 11 Jul 2006

Instead of planes flying for hours why cant we build a craft that can fly just 300 miles up, wait for the earth to revolve until your above your desired destination then come back to earth then in effect your only flying say 600 mile not thousands...and whilst up there u can get out your seat and stretch your legs n stuff...is it that mad of an idea really???

  Wilham 20:30 11 Jul 2006

Not mad, just no understanding of angular momentum.

  Forum Editor 20:43 11 Jul 2006

Yes, I'm afraid it is.

To reach an altitude of 300 miles, an aircraft would have to achieve escape velocity. From the surface of the Earth, escape velocity (ignoring air friction) is about 7 miles per second, or 25,000 miles per hour. For an aircraft full of people and luggage to accelerate to that speed the engines would have to be considerably more powerful than the Saturn V booster, which develops around 7.5 million pounds of thrust in its first stage alone.

The aircraft would have to be enormously strong to withstand the buffeting of the launch acceleration, and then to endure the incredible heat of re-entry when it was time to land.

The passengers would all have to be trained to endure the G-forces generated at launch and climb-out, and they would have to tolerate the sickness that invariably comes with weightlessness. All in-flight food would be served in squeezy bags, and nobody would be able to visit the toilet, or stretch their legs during the flight.

The cost, per ticket, would run into tens of thousands of pounds, and life-insurance policies would all be void. Your baggage allownace would be almost nil.

It's back to the drawing board on this one, I think.

  GANDALF <|:-)> 20:44 11 Jul 2006

*ahem* gravity tends to work in lateral and vertical fields *ahem* ;-))


  GANDALF <|:-)> 20:45 11 Jul 2006

I think my answer was shorter ;-))))


  wolfie3000 20:56 11 Jul 2006

So i guess what they do in sci-fi films is impossible then like in starwars an x-wing fighter leaves a planet with only little jets attached to it.

  VoG II 21:02 11 Jul 2006

I think that I could tolerate all of that, apart from the in-flight meal - I don't think that I would survive without BA's squashed sandwich.

  SG Atlantis® 21:52 11 Jul 2006


No that's not my flight taking off just the answers going right over my head.

My questions is how does a man who works in IT know so much? The power of the internet I suppose? Or is one of your clients NASA or something? You seem to have well prepared answers for almost every topic that pops up.

...No offence FE, just curious.

  zincy 22:58 11 Jul 2006

SG Atlantis I was thinking exact same thing! How does the FE knows so much? hehe liked the way FE decribed it as well!!

  namtas 23:13 11 Jul 2006

As the FE will no doubt advise It is not rocket science really.

click here

From the surface of the Earth, escape velocity (ignoring air friction) is about 7 miles per second, or 25,000 miles per hour. Given that initial speed, an object needs no additional force applied to completely escape Earth's gravity.

Answered by: Paul Walorski, B.A. Physics, Part-time Physics Instructor

  Forum Editor 23:20 11 Jul 2006

Because I have a brain the size of a planet? If one of my clients was NASA I can assure you I wouldn't be here, talking about escape velocities, I would be on an island in the Seychelles for six months a year.


Those X-wing fighters can do that because

a) It's a movie

b) The planets have low gravity. For that to be the case the planets would have to be pretty small, or at least have a very low mass.

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