9 ms·

Circular Runways [video]

72 points by cadab 10y ago

saycheese 10y ago
Appears to be an idea that's been around before [1] - might be interesting to build a smaller scale one that's explicitly for drone swarms. [1] http://paleofuture.gizmodo.com/these-circular-runways-were-designed-to-catapult-planes-1679960133 http://paleofuture.gizmodo.com/these-circular-runways-were-d...
- microcolonel 10y ago
  For fixed-wing drone airports, I feel like you'd have better luck making an inclined runway for landings, and a railgun-assisted runway for takeoff. Given that the biggest challenge is finding clearance at both ends of the run way, it would be nice not to have to find 360° clearance for both takeoff and landing.
- dingaling 10y ago
  Re: drones, Flight Refueling in the UK had a target-practice UAV called Falconet in the 1980s that launched from a circular runway. It rested on a dolly secured by a cable to the central post and whirled around until take-off. I think a couple of installations were built but most customers chose a more conventional rocket-boosted dolly for straight runways.
cadab 10y ago
The projects site: http://www.endlessrunway-project.eu/ http://www.endlessrunway-project.eu/
Nrsolis 10y ago
Yeah. Not so much. http://www.airliners.net/forum/viewtopic.php?t=1357935#p19415407 http://www.airliners.net/forum/viewtopic.php?t=1357935#p1941...
- yock 10y ago
  I'm having trouble recreating the poster's numbers. I'm sure it's my own ignorance, so I'd appreciate some correction. radius is 3500m velocity is 82m/s 82^2/3500 ~ 1.92 atan(1.92/9.81) ~ 0.19 or 10 degrees of bank. Where have I gone wrong?
  - htareque 10y ago
    It looks like you used 3500m as the radius when 3500m is the diameter.
    - yock 10y ago
      Thanks a lot, that's it.
- strathmeyer 10y ago
  What's so mental. Why is building such a bank unfathomable??
- gayprogrammer 10y ago
  The linked discussion has a lot of speculation and "that's a dumb idea" posts, but no actual debunking.
- nkoren 10y ago
  A lot of idiots on that forum. "Hey, in just two minutes of casual thinking about this, I've identified a flaw which a professional working on this for years has been unable to see!" Um, yeah, not so much. The concept may have problems, but that's not how it'll be debunked.
  - SteveNuts 10y ago
    That sounds a lot like a lot of comments on HN honestly.
- Applejinx 10y ago
  Well that's interesting. They seem to be arguing that the bank angle is super high, causing the planes to pull massive Gs just to land or take off, and that's terrible. Even if it's true all that means is, (a) planes achieving takeoff instantly have better than stall speed in the open air and can safely get up and away from the city, (b) planes landing can come in at any angle, have infinite space to negotiate a decent landing and no specific window to hit as far as retaining enough runway, plus the landing speed is significantly higher than stall speed in free air. That directly improves the controllability of the aircraft. The guy's right, this would work just fine. Even without a bank and increased G forces, it's not a bad idea, but when you include the reality of the banking increasing takeoff/landing speed over normal stall speed, it becomes a slam dunk. Very good idea anywhere you can afford to build three or more runways in your airport.
yock 10y ago
Non-pilot aviation fanatic here. It seems like adding a bank angle to final approach would increase the risk of stall-spin accidents on landing.
- handedness 10y ago
  Yeah, and any wing loading >1G is going to require increased groundspeed on landing.
- bitmapbrother 10y ago
  Adding a banking in airports that experience the side effects of cold weather could also be very problematic.
nthcolumn 10y ago
Okay only slightly related, I had an idea a long while ago for putting satellites into orbit where you just fling them? I didn't think it good for humans because of the G but for stuff. The win being that the power required is all on earth and you don't have to carry fuel with the payload. You could spin them up on a centrifuge and then let go at just the right time (and angle). I was going to mention it to Elon one day...
- atonse 10y ago
  Wouldn't the force required push the satellite so far towards the edge that it would get crushed?
- mrfusion 10y ago
  You know I've been researching the very same idea. And guess what none of the math I've tried so far rules it out! You do need a very big cable though. Think miles. There are actually many promising technologies to get mass into space with much lower marginal cost. I think the problem is that they all have high capital costs and no one wants to take the risk on a new technology.
  - tdb7893 10y ago
    Wouldn't the problem be air resistance? I thought you generally need to bring fuel with you because if you don't the air will brake you too much
    - mrfusion 10y ago
      Air resistance hurts you for sure. but the prospect of not bringing your fuel with you (see the rocket equation) really saves the most. In my design I have the ship tethered by a cable and a pipe that's delivering the fuel.
      - derekp7 10y ago
        Orbital velocity is about Mach 25. You would need to be going much faster than that, if your only power is applied in the atmosphere (you'd need enough additional speed to get above the atmosphere, and enough to overcome air resistance. And after the cable lets go, the the orbit will be elliptical, which means that at the end of one orbit you come right back to the launch site. So you need to bring enough fuel with you to flatten out the orbit once you are at the highest altitude. Oh, and then you have the weight and tensile strength of the cable, so similar issues to that faced by building a space elevator. A better idea is the launch loop, but again you have to deal with cable weight and tensile strength.
mrfusion 10y ago
Wouldn't a "P" shape make the most sense? That way you don't have to worry about the banking angle during touch down.
- nayuki 10y ago
  Even better would be a ρ (rho) shape!
hirundo 10y ago
How the heck can you camber the runway at the right angle to work for both a Boeing 747 landing at 160mph and a Cessna Skyhawk landing at 60mph?
- jason_wang 10y ago
  Most commercial aviation airports (Class-B and Class C) separate commercial and general aviation traffic. The landing speed difference along (let along the camber as you suggested) make it impossible to stagger 7x7 traffic with general aviation traffic.
lisper 10y ago
Wow, there are so many reasons this is a terrible idea. 1. It doesn't actually solve the problem it sets out to solve (crosswind landings). To the contrary, a circular runway guarantees that if you have any wind at all then you will have a crosswind at some point in the landing. Not only that, but the apparent wind direction will be constantly shifting during the landing, making the landing even more difficult than a normal crosswind landing. 2. Flying in a circle at a low airspeed and at low altitude is absolutely the single most dangerous thing you can do in an airplane. When you are flying in a circle, the outboard wing is moving faster than the inboard wing, and so if you are flying close to stall speed the inboard wing will stall first, resulting in a spin. It is possible to recover from a spin but you have to descend in order to do it. If the spin starts at low altitude there is nowhere to descend to, so you will crash. Spins on approach to landing are one of the leading causes of fatal crashes in small general aviation aircraft. 3. Airport approach and departure procedures are designed around the fact that runways are aligned in particular directions.
- bitmapbrother 10y ago
  The circular runway is banked so I would assume crosswinds aren't as devastating due to this banking. However, I am curious as to why you so adamantly believe that circular banked runways guarantee crosswinds. Is this based on scientific research that have proven this or is this just a guess?
  - lisper 10y ago
    > I would assume crosswinds aren't as devastating due to this banking. You would assume incorrectly. The bank is mostly irrelevant. Crosswinds happen when the direction of motion of the plane is anything other than directly in to the wind. If you're turning, your heading is continually changing, and so the relative wind direction will be continually changing, and so you will necessarily have a crosswind component everywhere except at the one point when you are heading directly into the wind. Even worse, the crosswind component will be continually changing as you turn. This is even worse than it seems. Landing in a crosswind involves a maneuver called "cross-control" where you roll the plane into the wind with the ailerons while simultaneously apply opposite rudder to arrest the resulting turn. It's one of the hardest things to do in an airplane. Getting it right is tricky even when the runway is straight and level and the wind is steady. Trying to do it on a curved banked runway, where the wind is necessary continually shifting as you turn, would be a total nightmare. > However, I am curious as to why you so adamantly believe that circular banked runways guarantee crosswinds. Is this based on scientific research that have proven this or is this just a guess? I'm a pilot with over twenty years of experience. But you don't have to be a pilot to see the folly of circular runways. It's simple common sense: if you're turning, you can't be heading directly into the wind the whole time.
jason_wang 10y ago
How would a circular runway affect inbound emergency aircrafts? My intuition tells me that a straight runway would be less burdensome on the flight crew. You set up for your approach then you can go back to dealing with the issues at hand.

72 points by cadab 10y ago

Appears to be an idea that's been around before [1] - might be interesting to build a smaller scale one that's explicitly for drone swarms. [1] http://paleofuture.gizmodo.com/these-circular-runways-were-designed-to-catapult-planes-1679960133 http://paleofuture.gizmodo.com/these-circular-runways-were-d...

microcolonel 10y ago
For fixed-wing drone airports, I feel like you'd have better luck making an inclined runway for landings, and a railgun-assisted runway for takeoff. Given that the biggest challenge is finding clearance at both ends of the run way, it would be nice not to have to find 360° clearance for both takeoff and landing.
dingaling 10y ago
Re: drones, Flight Refueling in the UK had a target-practice UAV called Falconet in the 1980s that launched from a circular runway. It rested on a dolly secured by a cable to the central post and whirled around until take-off. I think a couple of installations were built but most customers chose a more conventional rocket-boosted dolly for straight runways.

cadab 10y ago

The projects site: http://www.endlessrunway-project.eu/ http://www.endlessrunway-project.eu/

Nrsolis 10y ago

Yeah. Not so much. http://www.airliners.net/forum/viewtopic.php?t=1357935#p19415407 http://www.airliners.net/forum/viewtopic.php?t=1357935#p1941...

yock 10y ago
I'm having trouble recreating the poster's numbers. I'm sure it's my own ignorance, so I'd appreciate some correction. radius is 3500m velocity is 82m/s 82^2/3500 ~ 1.92 atan(1.92/9.81) ~ 0.19 or 10 degrees of bank. Where have I gone wrong?
- htareque 10y ago
  It looks like you used 3500m as the radius when 3500m is the diameter.
  - yock 10y ago
    Thanks a lot, that's it.
strathmeyer 10y ago
What's so mental. Why is building such a bank unfathomable??
gayprogrammer 10y ago
The linked discussion has a lot of speculation and "that's a dumb idea" posts, but no actual debunking.
nkoren 10y ago
A lot of idiots on that forum. "Hey, in just two minutes of casual thinking about this, I've identified a flaw which a professional working on this for years has been unable to see!" Um, yeah, not so much. The concept may have problems, but that's not how it'll be debunked.
- SteveNuts 10y ago
  That sounds a lot like a lot of comments on HN honestly.
Applejinx 10y ago
Well that's interesting. They seem to be arguing that the bank angle is super high, causing the planes to pull massive Gs just to land or take off, and that's terrible. Even if it's true all that means is, (a) planes achieving takeoff instantly have better than stall speed in the open air and can safely get up and away from the city, (b) planes landing can come in at any angle, have infinite space to negotiate a decent landing and no specific window to hit as far as retaining enough runway, plus the landing speed is significantly higher than stall speed in free air. That directly improves the controllability of the aircraft. The guy's right, this would work just fine. Even without a bank and increased G forces, it's not a bad idea, but when you include the reality of the banking increasing takeoff/landing speed over normal stall speed, it becomes a slam dunk. Very good idea anywhere you can afford to build three or more runways in your airport.

yock 10y ago

Non-pilot aviation fanatic here. It seems like adding a bank angle to final approach would increase the risk of stall-spin accidents on landing.

handedness 10y ago
Yeah, and any wing loading >1G is going to require increased groundspeed on landing.
bitmapbrother 10y ago
Adding a banking in airports that experience the side effects of cold weather could also be very problematic.

nthcolumn 10y ago

Okay only slightly related, I had an idea a long while ago for putting satellites into orbit where you just fling them? I didn't think it good for humans because of the G but for stuff. The win being that the power required is all on earth and you don't have to carry fuel with the payload. You could spin them up on a centrifuge and then let go at just the right time (and angle). I was going to mention it to Elon one day...

atonse 10y ago
Wouldn't the force required push the satellite so far towards the edge that it would get crushed?
mrfusion 10y ago
You know I've been researching the very same idea. And guess what none of the math I've tried so far rules it out! You do need a very big cable though. Think miles. There are actually many promising technologies to get mass into space with much lower marginal cost. I think the problem is that they all have high capital costs and no one wants to take the risk on a new technology.
- tdb7893 10y ago
  Wouldn't the problem be air resistance? I thought you generally need to bring fuel with you because if you don't the air will brake you too much
  - mrfusion 10y ago
    Air resistance hurts you for sure. but the prospect of not bringing your fuel with you (see the rocket equation) really saves the most. In my design I have the ship tethered by a cable and a pipe that's delivering the fuel.
    - derekp7 10y ago
      Orbital velocity is about Mach 25. You would need to be going much faster than that, if your only power is applied in the atmosphere (you'd need enough additional speed to get above the atmosphere, and enough to overcome air resistance. And after the cable lets go, the the orbit will be elliptical, which means that at the end of one orbit you come right back to the launch site. So you need to bring enough fuel with you to flatten out the orbit once you are at the highest altitude. Oh, and then you have the weight and tensile strength of the cable, so similar issues to that faced by building a space elevator. A better idea is the launch loop, but again you have to deal with cable weight and tensile strength.

mrfusion 10y ago

Wouldn't a "P" shape make the most sense? That way you don't have to worry about the banking angle during touch down.

nayuki 10y ago
Even better would be a ρ (rho) shape!

hirundo 10y ago

How the heck can you camber the runway at the right angle to work for both a Boeing 747 landing at 160mph and a Cessna Skyhawk landing at 60mph?

jason_wang 10y ago
Most commercial aviation airports (Class-B and Class C) separate commercial and general aviation traffic. The landing speed difference along (let along the camber as you suggested) make it impossible to stagger 7x7 traffic with general aviation traffic.

lisper 10y ago

Wow, there are so many reasons this is a terrible idea. 1. It doesn't actually solve the problem it sets out to solve (crosswind landings). To the contrary, a circular runway guarantees that if you have any wind at all then you will have a crosswind at some point in the landing. Not only that, but the apparent wind direction will be constantly shifting during the landing, making the landing even more difficult than a normal crosswind landing. 2. Flying in a circle at a low airspeed and at low altitude is absolutely the single most dangerous thing you can do in an airplane. When you are flying in a circle, the outboard wing is moving faster than the inboard wing, and so if you are flying close to stall speed the inboard wing will stall first, resulting in a spin. It is possible to recover from a spin but you have to descend in order to do it. If the spin starts at low altitude there is nowhere to descend to, so you will crash. Spins on approach to landing are one of the leading causes of fatal crashes in small general aviation aircraft. 3. Airport approach and departure procedures are designed around the fact that runways are aligned in particular directions.

bitmapbrother 10y ago
The circular runway is banked so I would assume crosswinds aren't as devastating due to this banking. However, I am curious as to why you so adamantly believe that circular banked runways guarantee crosswinds. Is this based on scientific research that have proven this or is this just a guess?
- lisper 10y ago
  > I would assume crosswinds aren't as devastating due to this banking. You would assume incorrectly. The bank is mostly irrelevant. Crosswinds happen when the direction of motion of the plane is anything other than directly in to the wind. If you're turning, your heading is continually changing, and so the relative wind direction will be continually changing, and so you will necessarily have a crosswind component everywhere except at the one point when you are heading directly into the wind. Even worse, the crosswind component will be continually changing as you turn. This is even worse than it seems. Landing in a crosswind involves a maneuver called "cross-control" where you roll the plane into the wind with the ailerons while simultaneously apply opposite rudder to arrest the resulting turn. It's one of the hardest things to do in an airplane. Getting it right is tricky even when the runway is straight and level and the wind is steady. Trying to do it on a curved banked runway, where the wind is necessary continually shifting as you turn, would be a total nightmare. > However, I am curious as to why you so adamantly believe that circular banked runways guarantee crosswinds. Is this based on scientific research that have proven this or is this just a guess? I'm a pilot with over twenty years of experience. But you don't have to be a pilot to see the folly of circular runways. It's simple common sense: if you're turning, you can't be heading directly into the wind the whole time.

jason_wang 10y ago

How would a circular runway affect inbound emergency aircrafts? My intuition tells me that a straight runway would be less burdensome on the flight crew. You set up for your approach then you can go back to dealing with the issues at hand.