BASE jump near Mt. Everest

[JasonG]

 

I imagine you have a lot steeper glide slope at that altitude!

[Tyson.g]

"it is important to note he didn't actually jump Everest. He jumped a mountain right next to Everest called Changtse. His feat is still very impressive but I do feel people need to be honest about what they do. Everest is still open for the first base jump"

From the comments section

[JasonG]

True, I don't think the summit of Everest will ever see some BASE action. But they were pretty high up nonetheless. 7200m!

[Lowell_Skoog]

 

I imagine you have a lot steeper glide slope at that altitude!

 

My understanding is that glide ratio does not change with altitude, but speed does. Glide ratio is the relative speed forward versus downward through the air. These speeds are both linearly related to air density, so the glide ratio remains the same as the air thins.

 

(Feel free to correct me if I'm wrong.)

 

[pcg]

I'm not a pilot or an aerospace engineer so I'm not familiar with the definition of glide slope and glide ratio. However, if you do a simple mental experiment and imagine the worst case scenario - zero air density, then (assuming your initial acceleration only has a vertical component) you will fall straight down no matter what your shape or angle of attack.

I think the poster is referring to glide path, and is correct in thinking that the glide path will be steeper at higher altitudes, but perhaps used the incorrect phrase to describe what he is thinking about, as I also may have done.

[alpine et]

 

I imagine you have a lot steeper glide slope at that altitude!

 

My understanding is that glide ratio does not change with altitude, but speed does. Glide ratio is the relative speed forward versus downward through the air. These speeds are both linearly related to air density, so the glide ratio remains the same as the air thins.

 

(Feel free to correct me if I'm wrong.)

 

 

Lowell, I think you are correct - below is an excerpt from a website detailing high altitude soaring. It describes how the best glide ratio is unchanged at altitude, but the speed changes. I believe best glide ratio is just the ratio that maximizes distance, so is basically the same as the glide ratio you'd reach while base jumping if your aim is to get out as far as possible, which is usually the goal??!

 

http://www.ssa.org/myhome.asp?mbr=4616398811

 

As we climb to higher altitudes, the air becomes thinner, or less dense. However, the indicated airspeed for stall, minimum sink, and best glide remains almost exactly the same. Some errors do creep in at the higher altitudes, but they are not larger than a knot or two. At 31,000 feet in our example, the minimum sink speed will still be near 50 knots IAS, and the best glide speed will still be near 60 knots IAS. The angle of attack of the wing at these indicated airspeeds will be the same as it was at sea level. The thing that has changed is the speed through the air mass (true airspeed). It is 100 knots in our example situation, and since there is no wind, the ground speed will also be 100 knots.

[JasonG]

Ah Ha, that isn't very intuitive, but quite interesting. Thanks for the correction!

[RaisedByPikas]

I'm not a pilot or an aerospace engineer so I'm not familiar with the definition of glide slope and glide ratio. However, if you do a simple mental experiment and imagine the worst case scenario - zero air density, then (assuming your initial acceleration only has a vertical component) you will fall straight down no matter what your shape or angle of attack.

I think the poster is referring to glide path, and is correct in thinking that the glide path will be steeper at higher altitudes, but perhaps used the incorrect phrase to describe what he is thinking about, as I also may have done.

 

This is what is known as a divide by zero error. If there is no air resistance then you would keep accelerating to infinite velocity.

 

But at high altitudes you would have to fall further to get up enough speed to achieve the ideal glide ratio so a high altitude base jumper should need more vertical distance before they can start tracking away from the mountain.

Edited June 12, 2013 by RaisedByPikas

[Choada_Boy]

If there is no air resistance then you would keep accelerating to infinite velocity.

 

The velocity of a massive object cannot exceed the speed of light, as put forth by A. Einstein in his special theory of relativity. Light itself cannot have infinite velocity.